Mark Schultz

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10 Myths About Geothermal Heating & Cooling

Illustration of a geothermal heating & cooling system that handles multiple loads for a home. Illustration from Modern Geothermal HVAC.

Imagine a home in which the temperature is always comfortable, yet the heating and cooling system is out of sight. That system performs efficiently but doesn’t require extensive maintenance or knowledge on the part of the owners.

The air smells fresh; you can hear the birds chirping and the wind rustling lazily through the trees. The home shares energy with the earth similar to the way the roots of the trees exchange the essentials of life to their leaves and branches. Sounds comfortable, doesn’t it?

Geothermal heating and cooling makes that vision a reality. Geothermal HVAC (heating, ventilating, and air conditioning) brings a building in harmony with the earth beneath, taking advantage of subterranean temperatures to provide heating in the winter and cooling in the summer.

How Geothermal Heating and Cooling Works

Outdoor temperatures fluctuate with the changing seasons but underground temperatures don’t change as dramatically, thanks to the insulating properties of the earth. Four to six feet below ground, temperatures remain relatively constant year-round. A geothermal system, which typically consists of an indoor handling unit and a buried system of pipes, called an earth loop, and/or a pump to reinjection well, capitalizes on these constant temperatures to provide “free” energy.

(Note that geothermal HVAC should not be confused with “geothermal energy,” the process by which electricity is generated directly from the heat inside the earth. That takes place on the scale of utilities and uses different processes, normally by heating water to boiling.)

The pipes that make up an earth loop are usually made of polyethylene and can be buried under the ground horizontally or vertically, depending on the characteristics of the site. If an aquifer is available, engineers may prefer to design an “open loop” system, in which a well is drilled into the underground water. Water is pumped up, run past a heat exchanger, and then the water is returned to the same aquifer, through “reinjection.”

Diagram of how geothermal HVAC systems work

Diagram of how geothermal HVAC systems work. Illustration from Modern Geothermal HVAC

In winter, fluid circulating through the system’s earth loop or well absorbs stored heat from the ground and carries it indoors. The indoor unit compresses the heat to a higher temperature and distributes it throughout the building, as if it were an air conditioner running in reverse. In summer, the geothermal HVAC system pulls heat from the building and carries it through the earth loop/pump to reinjection well, where it deposits the heat into the cooler earth/aquifer.

Unlike ordinary heating and cooling systems, geothermal HVAC systems do not burn fossil fuel to generate heat; they simply transfer heat to and from the earth. Typically, electric power is used only to operate the unit’s fan, compressor, and pump.

A geothermal cooling and heating system has three main components: the heat-pump unit, the liquid heat-exchange medium (open or closed loop), and the air-delivery system (ductwork) and/or the radiant heating (in the floor or elsewhere).

Geothermal heat pumps, as well as all other types of heat pumps, have efficiencies rated according to their coefficient of performance, or COP. It’s a scientific way of determining how much energy the system moves versus how much it uses. Most geothermal heat pump systems have COPs of 3.0 to 5.0. This means for every unit of energy used to power the system, three to five units are supplied as heat.

Geothermal systems require little maintenance. When installed properly, which is critical, the buried loop can last for generations. The unit’s fan, compressor, and pump are housed indoors, protected from the harsh weather conditions, so they tend to last for many years, often decades. Usually, periodic checks and filter changes and annual coil cleaning are the only required maintenance.

Geothermal HVAC Spreads

Geothermal HVAC systems have been used for more than 60 years in the U.S. and beyond.

They work with nature, not against it, and they emit no greenhouse gases. (As mentioned earlier, they use a smaller amount of electricity to run, because they are coupled in with the earth’s average temperature.)

Geothermal HVAC systems are becoming common features of eco-friendly homes as part of the growing green building movement. Green projects accounted for 20 percent of all newly built homes in the U.S. last year. By 2016, a Wall Street Journal article predicted that green housing will grow from $36 billion a year to as much as $114 billion. That’s approaching 30 to 40 percent of the entire housing market.

But a lot of information out there on geothermal heating and cooling is based on outdated information, or outright myths. In our new book Modern Geothermal HVAC Engineering and Control Applications (Egg/Cunniff/Orio -McGraw-Hill 2013), co-authors Greg Cunniff, Carl Orio and I bust many of these myths.

Geothermal HVAC Myths Busted

  • Geothermal HVAC systems are not considered a renewable technology because they use electricity. Fact: Geothermal HVAC systems use only one unit of electricity to move up to five units of cooling or heating from the earth to a building.
  • Photovoltaic and wind power are more favorable renewable technologies when compared to geothermal HVAC systems. Fact: Geothermal HVAC systems remove four times more kilowatt-hours of consumption from the electrical grid per dollar spent than photovoltaic and wind power add to the electrical grid. Those other technologies can certainly play an important role, but geothermal HVAC is often the most cost effective way to reduce environmental impact of conditioning spaces.
  • Geothermal HVAC needs lots of yard or real estate in which to place the polyethylene piping earth loops. Fact: Depending on the characteristics of the site, the earth loop may be buried vertically, meaning little above-ground surface is needed. Or, if there is an available aquifer that can be tapped into, only a few square feet of real estate are needed. Remember, the water is returned to the aquifer whence it came after passing over a heat exchanger, so it is not “used” or otherwise negatively impacted.
  • Geothermal HVAC heat pumps are noisy. Fact: The systems run very quiet and there is no equipment outside to bother neighbors.

A technician inspects a geothermal HVAC air handler

A technician inspects a geothermal HVAC air handler. Photo courtesy of Jay Egg

  • Geothermal systems eventually “wear out. Fact: Earth loops can last for generations. The heat-exchange equipment typically lasts decades, since it is protected indoors. When it does need to be replaced, the expense is much less than putting in an entire new geothermal system, since the loop or well is the most pricey to install. New technical guidelines eliminate the issue of thermal retention in the ground, so heat can be exchanged with it indefinitely. In the past, some improperly sized systems did overheat or overcool the ground over time, to the point that the system no longer had enough of a temperature gradient to function.
  • Geothermal HVAC systems only work in heating mode. Fact: They work just as effectively in cooling and can be engineered to require no additional backup heat source if desired, although some customers decide that it is more cost effective to have a small backup system for just the coldest days if it means their loop can be smaller.
  • Geothermal HVAC systems cannot heat water, a pool, and a home at the same time. Fact: Systems can be designed to handle multiple loads simultaneously.
  • Geothermal HVAC systems put refrigerant lines into the ground. Fact: Most systems use only water in the loops or lines.
  • Geothermal HVAC systems use lots of water. Fact: Geothermal systems actually consume no water. If an aquifer is used to exchange heat with the earth, all the water is returned to that same aquifer. In the past, there were some “pump and dump” operations that wasted the water after passing over the heat exchanger, but those are exceedingly rare now. When applied commercially, geothermal HVAC systems actually eliminate millions of gallons of water that would otherwise have been evaporated in cooling towers in traditional systems.
  • Geothermal HVAC technology is not financially feasible without federal and local tax incentives. Fact: Federal and local incentives typically amount to between 30 and 60 percent of total geothermal system cost, which can often make the initial price of a system competitive with conventional equipment. Standard air-source HVAC systems cost around $3,000 per ton of heating or cooling capacity, during new construction (homes usually use between one and five tons). Geothermal HVAC systems start at about $5,000 per ton, and can go as high as $8,000 or $9,000 per ton. However, new installation practices are reducing costs, to the point where the price is getting closer to conventional systems under the right conditions.

Factors that help reduce cost include economies of scale for community, commercial, or even large residential applications and increasing competition for geothermal equipment (especially from major brands like Bosch, Carrier, and Trane). Open loops, using a pump and reinjection well, are cheaper to install than closed loops.

Geothermal Heating and Cooling System in Maryland

[Image: Maryland geothermal HVAC installer] [Image: earth-river-geothermal] [Image: Earth River Geothermal Annapolis Maryland BBB Accredited Business]
From the ground up- We’re changing the way we live!

[Image: Geothermal Maryland]

Geothermal Heating and Cooling in Maryland [Image: Earth River Geothermal - Geothermal Heating and Cooling - Annapolis, Maryland] By Sarah Brophy, Kymberly Taylor & Michael Loftus What’s Up Magazine Annapolis, Maryland As gasoline prices rise and fossil fuels disappear, more and more Marylanders are looking down- at the ground; just six feet below their garden, residence, business, or favorite football field, there exists an almost infinite supply of heat, or geothermal energy. When harnessed to a geothermal heat pump, geothermal energy can be used to efficiently heat and to cool your residential or commercial property.

[Image: Residential geothermal heating system installation]

Your furnace burns a combustible fuel, such as oil or propane, to produce heat; geothermal heating and cooling systems transfer heat stored in the earth into your home or business, using underground pipes filled with water (mixed with an antifreeze solution). A geothermal heating and cooling system concentrates that heat efficiently and distributes it indoors. Throughout the summer, a geothermal heat pump will act as a heat sink and it enables you to naturally cool your home or business by using the earth’s stable subterranean temperature of fifty-seven degrees Fahrenheit. During the winter, a geothermal heating and cooling system reverses its loops and concentrates the heat from below your property to provide the most energy-efficient form of heating and cooling available on the market. The initial installation cost for a modest home is about twenty-thousand dollars and it can take as few as five years for the savings to offset those costs, depending upon the systems they replace, and the geothermal incentives codified into law. By switching to a geothermal heating and cooling system, not only will your energy bills drop 30 to 60% (depending upon which type of system you currently use), you’ll also have the satisfaction of tapping into a clean, cost-effective and unlimited renewable energy source: the Earth. Also, your wallet will share in your satisfaction- there are federal, state, and local funds available to help defray the costs. The American Recovery and Reinvestment Act alone provides residential geothermal energy credits that allow a 30% federal geothermal tax deduction (for qualified geothermal heating and air conditioning systems installations) with no upper limit. The effective cost of a $20,000 installation is therefore reduced to $14,000, even before Maryland geothermal grant funds are considered. Local property tax credits, which can amount up to $7,000 in additional savings ($2,500 in Anne Arundel County) can reduce the total cost to levels below standard heating and cooling system installations.

How Do Geothermal Heating and Cooling Systems Work?

[Image: Geothermal contractor lays three six foot deep trenches for the geothermal ground loops]

First, your contractor digs three to six-foot deep trenches. Have you ever wondered why rabbits live in extensive burrows located deep underneath the ground? In Maryland, no matter what the weather is like outside, the subterranean temperature, greater than six feet underground, is always a moderate and stable 56-57° Fahrenheit. A geothermal heat pump system captures heat from the ground and uses water as the heat transfer medium. Water transmits heat 200 times more efficiently than the air that is used by conventional air source heat pumps. These environmentally friendly geothermal pumps actually work with nature- they turn extremely cold air into hot air in the wintertime and very hot air into cold air in the summertime. Geothermal heating and cooling systems also reduce carbon emissions and energy usage by up to 72% when compared to conventional heat pumps.

[Image: Pipes and geothermal ground loops are laid into the wells and trenches]

Next, pipes or ground loops are laid down. Sometimes, deep wells are drilled, depending on the site. Geothermal heating and cooling systems need three things to operate:
  • Ground Loops
  • A Geothermal Heat Pump
  • Duct Work. (To distribute the energy around your home or business).
Ground loops are pipes filled with an aqueous solution and they are buried at least six feet underground near your home or business. They cycle the aqueous solution from the ground to your home and then back into the ground. There are closed loops and open loops. A closed-loop circulates the same aqueous solution continuously. An open loop is simply a pipe that is open at both ends and circulates groundwater. Vertical closed-loop systems are used almost exclusively in Maryland.

[Image: Geothermal ground loops are buried into the ground]

Later, all ground loops are buried. The geothermal heat pump is the system’s “brain.” However, instead of right and left hemispheres, the pump has compressors and heat exchangers. About the size of a washing machine, the system is attached to the outdoor geothermal ground loops. Usually, the geothermal heat pump is located in a cabinet located in your basement or attic. Ground loops carry geothermal heat to the geothermal heat pump, which uses its compressor to convert 57°F groundwater into an exceptionally hot gas-approximately 175°F. A heat exchanger then removes the heat from the gas and channels it to a blower, or fan, that circulates heat throughout your home or business’ ductwork and vents. Geothermal Cooling & Geothermal Air Conditioning In the summer, your geothermal heat pump uses the same groundwater to cool your home. Do you ever hear your central air conditioner groaning on a 90°F scorching day? It is working hard to draw in that 90-degree air and to lower its temperature by about 15°F so you can remain cool and comfy inside. Your geothermal pump does not need to work as hard so is much quieter and significantly more energy-efficient. Instead of converting very hot air to cool air, it begins with a 56-57°F ground source baseline temperature to produce air cold enough to keep your home comfortable. The thermal “hot” water cycles back underground, where the earth regulates its temperature back to about 57°F. But wait, there’s more. Instead of cycling all the heat back to the ground, modern geothermal heating and cooling systems can capture this heat to provide domestic hot water by using a device called a desuperheater. Desuperheaters shorten the payback periods of an investment in a geothermal heating and cooling system.

[Image: Geothermal heat pump that has a desuperheater inside]

This geothermal heat pump has a desuperheater inside. It directs, by a horizontal pipe, residual heat right to your water tank to assist with heating.

Geothermal Heating in Action

Geothermal energy systems are becoming more and more mainstream. You can find them at The Market House in Annapolis (when it finally re-opens,) Easton’s St. Mark’s United Methodist Church, Kent Island’s United Methodist Church, Washington College’s two newest dorms (and soon in its renovated dining hall), Gilliam and Spector Halls at St. John’s College-and in many residences around Annapolis, including John Martin’s home. Martin considered solar energy for heating his home when he began exploring renewable energy systems. He ultimately chose geothermal, though at some point he may use solar power to heat his pool. Geothermal heating is a “no brainer,” Martin says, because his residence, due to its northern exposure and extensive glass surfaces, is very expensive to heat and cool. With “GeoExchange” he and his family are trying to do their part. “We can continue to enjoy the house, be more energy-efficient, and have a greener planet. We’re trying to make a little bit of difference,” he says. He has calculated that the money he saves on energy bills will equal his upfront costs to install the system in just six years. And, he notes, it gets shorter every time the price of oil goes up. In other words, eventually, his savings on energy bills will equal the upfront costs. The contractor who installed the Martins’ system, Earth River Geothermal Inc., notes that geothermal systems may have huge financial and environmental benefits; however, the homeowner should understand that initial capital costs are relatively high. Retrofits for modestly sized homes start at about $20,000 for a 3-ton geothermal system. He points out that the United States Environmental Protection Agency reports that geothermal systems are “the most energy-efficient, environmentally clean, and cost-effective space-conditioning systems available.” Moreover, the United States Government Accountability Office predicts that “if geothermal systems were installed nationwide they could save several billion dollars annually in energy costs and substantially reduce pollution”. Keep in mind that, especially if you are retrofitting an existing building, the drilling process can surprise you and your neighbors. Inevitably water, dirt, and sand combine to create a mucky mess. The Martins needed four 300-foot geothermal wells. Although John Martin’s geothermal contractor prepared the yard by removing the sod and covering the driveway with tarps and resodded the lawn after the project’s completion, he says that the whole process still temporarily creates “a hefty mess.” Institutions confront the same concern as homeowners over rising utility bills. Containing energy costs at Washington College in Chestertown is critical, especially with 30,000 square feet of new dorm space. Briggs Cunningham, the climate action coordinator at the college’s Center for Environment and Society, says that by installing geothermal, “the college can keep its budget at a fairly consistent level.” There was some student concern about building “new” (not typically considered a sustainable practice), but the dorms will allow more students to live on campus and provide student housing as older dorms are retrofitted or used for other purposes. When it comes to accessing geothermal heat, the Eastern Shore and Annapolis have a geological advantage over many other parts of the country: soil composed of sand, clay, and not much rock. Pliable earth makes drilling wells for geothermal exchange much easier than it is in other areas, even if the hole is just six inches across. At St. Mark’s United Methodist Church in Easton, twelve wells were needed, every 404 feet. These were dug during the first phase of expansion. And there is room for 28 more wells for future phases. The Kent Island United Methodist Church drilled 50 geothermal wells and has room for another 50 geothermal wells if the church expands. Though geothermal heating and cooling systems seem unwieldy, one professional in charge of the Easton and Kent Island church expansions reminds us that the systems are versatile: they can be modified to work with existing radiators or to direct hot and cold air into different zones. And they can be controlled automatically, much like a conventional central heating and air conditioning. If a loop in a well fails, the well can be closed off and sealed and a new well drilled and connected. “The new technology is finding its ground. It’s not a fast recovery system, but it’s very constant and saves energy and lowers operating costs,” he says.

Geothermal Heating and Cooling Cost

[Image: Geothermal ground loops are buried and completely concealed after the geothermal work is completed.]

Ground loops are buried and completely concealed, so this formidable mess disappears when the job is done. Your contractor should be able to help you sort out grants and tax credits that will help reduce your costs. There was a 30 percent federal tax credit for residential systems and the Maryland grant program has benefited from the 2009 government stimulus money though, at this writing, applicants may face a waiting period in 2010. Currently, there is a 26% Federal geothermal heating and cooling tax credit. Even if you don’t receive a grant during the first year, you may be eligible to join a waiting list. Local counties also have geothermal property tax credits, especially in Anne Arundel County, Howard County, Montgomery County, and Prince Georges County. You can learn about state grants and rebates on the Maryland Energy Administration‘s Web site. Remember to hold on to your receipts and purchase documents so you can prove that you qualify. Some alternative energy systems just may not be feasible. When you consider the cost of a system and whether it will suit your needs, take into account three factors:
  • Installation cost
  • Appropriateness to your site
  • Available rebates, grants, and tax credits as well as the energy savings that offset the initial cost
  • Maintenance costs. Geothermal systems, because they work with so little effort, have a long life and minimal maintenance costs.
We must add the “planet” to the list. It’s not all about economics, but also about something priceless: a healthier environment for future generations. Sarah S. Brophy’s new initials after her name are LEED-AP: Leadership in Energy and Environmental Design-Accredited Professional. With green building and living becoming mainstream, LEED is no longer just for businesses, architects, and engineers-it’s for homebuilders and homeowners, too. The simplest and easiest practices continue to make a difference in your energy use. Here are ways to conserve energy in two important areas:

[Image: In Maryland, the subterranean temperature is a steady 57 degrees Fahrenheit year round]

In Maryland, the subterranean temperature is a steady 55-57°F year-round.

Residential Heating and Cooling

Ask your utility company, or find an experienced contractor, to conduct an energy audit to identify inefficiencies in your home or business. Infrared technology may be used to spot air leaks. An auditor will also examine your insulation and look for gaps from animal holes or missing building fabric around light fixtures and piping that let heat escape. Put up your storm windows; use insulating blinds or curtains and use draft “snakes”. Examine your sliders, if you have them, and ensure that they are sealed properly. One expert notes “even the best slider made is a poor excuse for a window or door.” Check weather stripping on doors and caulking on windows. Eliminate gaps where heat can leak out. Keep furnace filters clean to improve airflow. Keep blankets and throws on your most-used chairs and couches. While watching television or reading, wrap up rather than turning the heat up. Warm cold floors with seasonal throw rugs. Hot Water Heaters Turn down the temperature on your water heater. Find the tank, locate the thermostat, and drop it to 120°F or so. If you are turning on cold water in the bath or shower to adjust the temperature of your hot water, your hot water is too hot. Water loses a lot of heat traveling through pipes. Make sure that the tank and the pipes are well insulated. What’s Up Magazine Annapolis, Maryland

The Most Efficient Heating and Cooling Technology

Let’s have a look at the most efficient heating and cooling technology while replacing a thirteen SEER air conditioning system and eighty AFUE with a WaterFurnace geothermal heating and cooling system.

If you’re in the market for new HVAC equipment, it’s most likely because your current system is nearing its end of life or you’re building a new house and you’re in the process of learning your options. In both scenarios, some level of investment is required.

What is the minimum you would be content with for your house? If you are contemplating geothermal it is very likely that efficiency is imperative to you. If the very least you’d accept is a sixteen SEER air-conditioner coupled with a ninety-two AFUE furnace, it is logical to use that cost as a starting point for examination because it signifies the least amount of money you can devote and still be at ease.

Depending on where you reside, the total cost for a sixteen SEER air conditioner and a ninety-two AFUE system can vary significantly; however, it can reach as much as thirteen thousand in many places. Prices differ greatly depending upon numerous factors (ground composition, topography, size of the house, equipment selected, etc.); however, let us set the price to put in a ground-source heating and cooling system in your home is twenty-five thousand dollars. There is currently a twenty-six percent United States’ Fed. Tax Credit which is set to decrease each year until 2021.

That equates to a six-thousand-five-hundred dollars credited to your taxes; it is not just a deduction. The initial cost difference between a regular system versus a geothermal heating and cooling system is just five-thousand-five-hundred dollars. Your county or municipality may also have additional incentives that will not be factored in this calculation.

Geothermal vs. New Air Conditioning & Furnace (Cost Difference) $5,500
80 AFUE System Vs. Aging 13 SEER: Annual Savings of Geothermal $1,416
Amount of Time To Recoup Investment: 58 months
After 25 Years (average life of GHP[4]) Profit: $40,912

The most efficient heating and cooling technology is geothermal!

VIEW MARYLAND’S INCENTIVES FOR RENEWABLES & EFFICIENCY

The Most Efficient Method of Heating & Cooling Your Home

WaterFurnace Geothermal Heat Pumps Are 530% Efficient When Compared To The Best Gas Furnace Which Has An Efficiency of 98%!

Earth River Geothermal designs and installs vertical geothermal loop fields for the best ground source heat pumps available on the market, WaterFurnace Geothermal Heating and Cooling Systems. WaterFurnace systems rank #1 in energy-efficiency because WaterFurnace systems can deliver 5+ units of energy for every 1 unit of electrical energy used. When compared to even the most superior ordinary gas furnace system which delivers < 1 unit of energy for every unit it consumes. This means that a WaterFurnace geothermal system’s energy efficiency exceeds 530% when compared to the most efficient gas furnace which rates only 98%. – WaterFurnace

Analysis Of Cost And Energy Performance Of Geothermal Heat Pump Systems In Southern Louisiana

Duran Tapia, Claudia de Lourdes, “Analysis of Cost and Energy Performance of Geothermal Heat Pump Systems in Southern Louisiana” (2017). LSU Master’s Theses. 4504. https://digitalcommons.lsu.edu/gradschool_theses/4504

This Thesis is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Master’s Theses by an authorized graduate school editor of LSU Digital Commons. For more information, please contact gradetd@lsu.edu.

Claudia de Lourdes Duran Tapia‘s one-hundred-seventy page thesis about ground-source heating and cooling systems. Mark Schultz, President of Earth River Geothermal and his web developer, Michael A. Loftus will be gathering energy consumption data and systems data from clients throughout 2020 in order to produce a report similar in format for Central Maryland.

Claudia de Lourdes Duran Tapia, Louisiana State University and Agricultural and Mechanical College, claudiaduran_21 [at] hotmail.com.

A Thesis Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Master of Science in Construction Management in

The Bert S. Turner Department of Construction Management by

Claudia de Lourdes Duran Tapia B.S., University of New Orleans, 2015 August 2017

Acknowledgments

I am grateful for the Bert S. Turner Department of Construction Management at Louisiana State University for funding this research. I would like to especially thank Dr. Christofer Harper for giving me the opportunity to pursue this degree and for his constant support and guidance throughout this endeavor. Also, I would like to thank Dr. Yimin Zhu and Dr. Chao Wang for their valuable assistance during this research project. This research would not have been possible without the participation of several consultants, non-profit organizations, and each of the homeowners and contractors who shared their knowledge and experience of working with geothermal heat pumps.

My gratitude to my graduate colleagues in the Construction Management Department, whose friendship and invaluable support helped me to enjoy this year of graduate school. I cannot be more thankful to my father, Jorge Duran Camacho, only the smartest, hardworking engineer and generous man I have ever met. I want to especially thank my mother, Claudia, who dedicated years of her life to take care of me and my siblings Gabriela and Jorge, her unconditional love and support has motivated me to always look forward even in the toughest moments.

Finally, I would like to thank Luis de Grau, who shared with me his passion for green building and encouraged me from the beginning of this journey. Thank you, Lord, for all your blessings, especially for my old friends and the new friends I have made in LSU because they made me feel less far from home and no matter where I go, I will always carry them in my heart.

TABLE OF CONTENTS

ACKNOWLEDGMENTS ABSTRACT

CHAPTER 1: INTRODUCTION 1.2. Background 1.2. Report Organization

CHAPTER 2: LITERATURE REVIEW 2.1. Overview of 2.2. Geothermal Heat Pump System Components 2.3. Standards and Certifications 2.4. Geothermal Heat Pump Market Overview 2.5. Other Ground-Source Thermal Technology 2.6. Performance and Cost Data

CHAPTER 3: METHODOLOGY 3.1. Define Scope of Work 3.2. Conduct Literature Review 3.3. Develop Case Study Protocol 3.4. Conduct Case Studies 3.5. Analyze Case Study Data 3.6. Discussion and Conclusions

CHAPTER 4: ANALYSIS 4.1. Case Study 1 4.2. Case Study 2 4.3. Case Study 3 4.4. Case Study 4

CHAPTER 5: DISCUSSION 5.1. Case Study 1 (GH1 and CH1) 5.2. Case Study 2 (GH2) 5.3. Case Study 3 (GH3 and CH3) 5.4. Case Study 4 (GH4) 5.5. Comparison of Case Studies

CHAPTER 6: CONCLUSIONS 6.1. Primary Results and Conclusions 6.2. Limitations 6.3. Future Research

REFERENCES

APPENDIX A. GEOTHERMAL CASE STUDY PROTOCOL QUESTIONNAIRE APPENDIX B. CONVENTIONAL CASE STUDY PROTOCOL QUESTIONNAIRE APPENDIX C. CONVENTIONAL HVAC SYSTEM QUOTE SHEET APPENDIX D. AVERAGE COST ELECTRICITY AND NATURAL GAS FOR RESIDENCES IN LOUISIANA APPENDIX E. PAYBACK PERIOD CALCULATIONS VITA

ABSTRACT

In the last three decades of the geothermal heat pump (GHP) industry, there has been an urge to present data, especially performance and itemized installation cost, as a plan to reduce the lack of knowledge and trust towards GHP systems for heating and cooling. The potential of GHPs in hot and humid climates is significant [Tao and Zhu, 2012]. However, past research efforts have demonstrated this potential through the use of simulation rather than real-time data. Therefore, the scope of work for this research is to investigate GHP system applications for residential buildings in areas with hot and humid climates. Based on the scope of work, the objective of this research is to determine the cost, energy performance, and the payback period of GHP systems using real data collected from residences in southern Louisiana.

To achieve this objective, the research answered the following questions: RQ1: How do geothermal heat pump systems perform in terms of energy usage and costs in hot and humid climates when compared to traditional HVAC systems? RQ2: What is the payback period for installing a GHP system in hot and humid climates for a residential dwelling?

A case study protocol was developed to collect building information, HVAC installation cost, financial incentive, energy usage, and end-user satisfaction data from residential buildings in Louisiana, three with GHP systems and two with conventional air-source systems. The electricity consumption and usage cost between the samples were compared using ANOVA in SPSS.

This study concludes that tax credits can make GHP systems more affordable to average size households as the payback period can be four times longer without the tax credits, (note: this the thesis focuses on data obtained from Louisiana, a southern state within the United States where cold weather is rarely forecasted. although the contractor base for GHPs in southern Louisiana is in its infancy, homeowners feel more satisfied with the performance of a GHP system than with the performance of a conventional air-source system.

CHAPTER 1: INTRODUCTION

1.2. Background

Energy is necessary for almost all facets of human existence: oil and gas for cooking and heating; electricity for cooling, lighting, appliances and machines; gasoline and diesel fuel for transportation; and a mix of energy supplies for a myriad of other purposes [2008 APS Energy report]. In terms of economics, energy is key to macroeconomic growth. In most cases, energy consumption increases as societies become more developed and their standard of living increases. The United States, for example, with the highest per capita gross domestic product reported by the World Bank, consumed 97.8 quads (1 quad=1015 Btu) of energy in 2010 which represented 19% of all global consumption, making the US the second-largest share after China [2011 Buildings Energy Data Book, p.1-7].

Americans spend 90% of their time indoors, working, living, shopping and entertaining in buildings that consume enormous amounts of energy. Since most of their energy comes directly or indirectly from fossil fuels, buildings are responsible for large quantities of greenhouse gas (GHG) emissions [2008 APS Energy Report]. According to the U.S. Energy Information Administration (EIA), in 2010 the building sector consumed 40% of total primary energy but consumed 74% of all electricity usage.

Heating Ventilating and Air Conditioning (HVAC) systems are typically one of the largest components of building energy consumption, accounting for 42% of residential primary energy use and 32% of commercial building primary energy use [2011 Buildings Energy Data Book, tables 2.1.6 and 3.1.5]. Yet, a large fraction of the energy delivered to buildings is wasted because of inefficient building technologies and systems [2008 APS Energy Report]. In order to improve energy efficiency and savings, new technologies and systems must be explored, particularly on the HVAC side of energy consumption. The U.S. Department of Energy Building Technologies Program (DOE-BTP) identified geothermal heat pumps as one such high-impact technology that can substantially reduce energy consumption and peak electrical demand in residential and commercial buildings.

Geothermal Heat Pumps (GHP), also known as Ground-Source Heat Pumps (GSHP) are among the most efficient, with annual energy consumption as little as half that of conventional systems. When compared to a stereotypical Air-Source Heat Pump (ASHP) or typical furnace with a split-system air conditioner, the primary energy savings are in the range of 30% to 60%. In addition, for many commercial and residential applications, GHPs also provide water heating via a desuperheater [2012 DOE-BTP R&D Roadmap].

While GHPs are more energy-efficient compared to the best available ASHPs and forced-air furnace systems, national impacts also depend on likely market penetrations of each alternative. Multiple studies identified three key barriers that inhibit GHP widespread industry growth:

High first cost for ground loops Low market awareness and lack of knowledge/trust in GHP benefits, and… Infrastructure limitations including a limited number of qualified installers.

The purpose of this study is to address the second identified key barrier, especially in U.S. Southern states, by developing an economic feasibility analysis to compare the energy performance and cost of GHP systems with other conventional air-source HVAC systems installed in residential buildings in Southern Louisiana to determine the benefits and challenges of GHPs in climates that experience higher cooling loads that heating loads. This research employs utility and monitored data of actual GHP systems to calculate the payback period on the investment of such systems. The study will compare the payback period obtained with and without considering the Federal residential tax credit.

To address the purpose of this research, this thesis is organized into six chapters and altogether describes the work that has been completed in order to achieve the objectives and answers the research questions for this research project. The following information briefly describes the contents of each chapter:

1.2. Report Organization

Chapter 1, the current chapter, provides a background of building energy consumption and introduces GHPs as well as the benefits and barriers of GHPs in the United States market. This chapter also briefly explains the motivation that precedes this research, the purpose and the main tasks.

Chapter 2 presents a substantial collection of literature review, which contains the most important basic theory behind GHP systems. The content of this chapter is meant to expand the knowledge that homeowners or any person have in regards to non-conventional HVAC systems. This chapter attempts to clarify certain common misinterpretations of GHP system applications/limitations, particularly, applications based on geography and climate. Chapter 2 also highlights the difference between this study and previous similar research projects and how this difference intends to improve the body of knowledge.

Chapter 3 describes the methodology used for this research. The third chapter provides the detailed steps for conducting this research from the initial literature review through the analysis and discussion of results and conclusions.

Chapter 4 summarizes the general information of each case study and analyzes the information collected in each case study from surveys (Appendix A) and interviews.

Chapter 4 additionally presents the results of the statistical tests and payback period return on investment evaluation conducted based on the energy usage and cost data collected from each case study.

Chapter 5 discusses the results obtained in the analyses presented in the previous chapter. The author utilizes this section to provide insight from the results observed in each case the study, especially in cases where the system design was determined to be non-ideal for the the facility, oversized, or unnecessarily complex. The discussion goes beyond numbers and presents information that highlights specific components of GHP systems in residential homes found in southern Louisiana as well as the perceived satisfaction in using a GHP system.

Chapter 6 provides a brief summary of the knowledge gained from this study as well as reviewing the goals achieved and lessons learned in conducting this research project. This chapter presents the conclusions and limitations of this study and suggests possible future research.

CHAPTER 2: LITERATURE REVIEW

2.1. Overview

Geothermal energy or geothermal heat is the thermal energy stored below the surface of Earth. Geothermal heat recovered from different depths below the surface provides unique and different possibilities of utilization. Among the advantages of geothermal energy is that the source does not depend on the weather and is available 24 hours per day and 7 days a week. Consumed geothermal energy is renewed and replenished from the internal planetary reservoir and is unlimited from a human perspective if used sustainably. Using renewable energy resources sustainably means that the rate of consumption is equal or smaller to the rate of renewing the process [Stober and Bucher, 2013].

Geothermal energy is used in three main ways: electricity generation, direct heating, and indirect heating and cooling via geothermal heat pumps (GHPs). These three processes use high, medium, and low temperature resources, respectively. High and medium temperature resources are usually the product of thermal flows produced by the molten core of the Earth, which collects in areas of water or rock. Low temperature resources are near ambient temperature and are mostly attributable to solar energy absorbed at the ground level and ambient air. High and medium temperature thermal resources are often deep within the earth, and the depth affects whether they can be exploited economically as drilling and other extraction costs can increase substantially when drilling at great depths [Self et al., 2012]. Low temperature geothermal resources are abundant and can be extracted and utilized in most locations around the world. Extracting such thermal energy is relatively simple because the depths involved are normally small. Heat pumps extract low temperature thermal energy and raise the temperature to that required for practical use [Self et al., 2012].

In terms of using geothermal energy, indirect heating and cooling using GHP technology is not the same technology as geothermal power generation, also known as enhanced geothermal systems (EGS), in which the extreme heat of subsurface geological processes is used to produce steam and ultimately to generate electricity. Nor is it the same as the direct use of geothermal heat, in which moderate-temperature geothermal sources such as hot springs are used directly to heat greenhouses, aquaculture ponds, and other agricultural facilities. GHP systems use the only renewable energy resource that (a) is available at most building’s point of use, (b) is available on demand, (c) cannot normally be depleted (assuming proper design), and (d) are potentially affordable [Liu, 2010].

The biggest difference between GHP and conventional space conditioning and water heating systems is that, instead of rejecting heat from the buildings to the ambient air (in cooling mode) and extracting heat from fossil fuel combustion, electricity, or the ambient air (in space and/or water heating modes), a GHP rejects heat to or extracts heat from various ground resources, including the earth, surface water, recycled gray water, sewage treatment plant effluent, stormwater retention basins, harvested rainwater, and water from subsurface aquifers– either alone or in combination with conventional heat addition and rejection devices in a hybrid configuration [Liu, 2010].

GHPs are becoming more common as the costs of energy and equipment maintenance rise. When properly designed and installed, GHPs not only reduce energy use, but lower maintenance costs and extend equipment life since they have no exposed outdoor equipment. They are very simple devices and have only a slight difference from traditional heat pumps [Kavanaugh, 2006].

Finances of course are a key issue. Although GHPs need considerable initial investment (higher than common HVAC systems), in theory the overall performance is more favorable. The higher installation cost is due to the additional ground and site work (usually drilling and completion activities) and components (heat pump, connections, and distributors). On the other hand, running costs for GHPs are generally low, as usage is mainly electricity for operating the heat pumps and circulation pumps [Rybach, 2012].

Current GHP research and development efforts focus on reducing installation costs through advanced design and installation configurations and approaches. Additionally, many organizations, including the Department of Energy-Building Technologies Program (DOE-BTP), are focusing efforts on innovative financing approaches to defer or reduce upfront costs.

2.2. Geothermal Heat Pump System Components

A GHP system, in its most basic elements, consists of a ground loop, a heat pump, and a heating/cooling distribution system. This section will review the basic principles of the airconditioner and the fundamentals of heat pumps, along with introducing the various types of ground loops and the different configurations available.

2.2.1. Indoor Components

2.2.1.1. Heat Pump

To understand how GHPs work we need to start from the basics: the air-conditioner. The air-conditioner, also known as the refrigeration cycle, consists of several primary components and four primary functions as shown in Figure 2.1.

Figure 2.1 - Simple Vapor-Compression Refrigeration Cycle

Figure 2.1. Simple Vapor-Compression Refrigeration Cycle (Adapted from: Kavanaugh, 2006)

The compressor (shown between points 1 and 2 in Figure 2.1), driven by an electric motor, is typically located outdoors, and “sucks” the refrigerant from point 4 through tubing in the evaporator coil. This action causes the liquid refrigerant to evaporate and become cold (≈45°F). The evaporating refrigerant inside the tubes cools the air being circulated over the outside of the tubes and fins by the indoor fan. In order to move the refrigerant from point 1 to point 2, it must be raised to a higher pressure by the compressor. The compressor causes the refrigerant to become a hot and high pressure vapor. The hot refrigerant vapor is sent through the tubing inside the condenser. Outdoor air circulated by a fan cools the refrigerant and causes it to return to a liquid (condense). Even though the outside air may be warm (80-100°F) it is cooler than the hot refrigerant (100-160°F). The warm liquid leaving the condenser at point 3 passes through an expansion valve device which lowers the refrigerant pressure before it returns to point 4 to repeat the cycle [Kavanaugh, 2006]. In water cooled or geothermal systems, a pump is used rather than an outdoor fan. Figure 2.2 shows the primary components of a water source air-conditioner followed by a description of the cooling-only cycle.

Figure 2.2 - Water Source Air Conditioner

Figure 2.2. Water Source Air Conditioner (Adapted from: Kavanaugh, 2006)

The cycle of a water source-air conditioner in cooling-only mode is basically the same as the one described on the previous page except for the location of the compressor and the replacement of the outdoor fan with a pump. In this case, the compressor is located indoors and the use of a pump changes the process from points 2 to 3.

After the refrigerant is compressed, the hot and high-pressure refrigerant vapor is sent through the outside tubing of a tube-inside-tube water coil condenser. Water is circulated by the pump through the condenser coil and outdoor water loop (ground loop, lake loop or water well) and cools the refrigerant causing it to return to a liquid (condense).

The water is typically 50°F to 90°F and is cooler than the hot refrigerant (90°F to 140°F). The liquid refrigerant leaving the condenser from point 3 passes through an expansion device which lowers the refrigerant pressure before it returns to point 4 to repeat cycle [, Kavanaugh, 2006]. Heat naturally flows “downhill”, from higher to lower temperatures. A heat pump is a machine which causes the heat to flow in a direction opposite to its natural tendency or “uphill” in terms of temperature. Because work must be done to accomplish this, the name heat “pump” is used to describe the device. In reality, a heat pump is nothing more than a refrigeration unit. Any refrigeration device (window air conditioner, refrigerator, freezer, etc.) moves heat from a space and discharges that heat at higher temperatures. One primary difference between a heat pump and a refrigeration unit is that heat pumps are reversible and can provide either heating or cooling to the space [Rafferty, 2001].

A heat pump is merely an air-conditioner with extra four-way reversing valve that allows the condenser (hot coil) and evaporator (cold coil) to reverse places in winter. Figure 2.3 and Figure 2.4 shows the reversing valve in heating mode and cooling mode respectively. The valve permits the refrigerant to travel from the indoor air coil to the compressor while in cooling mode and from the water coil to the compressor while in heating mode.

In heating mode, the reversing valve slides to a position that routes the hot refrigerant from the compressor through the top port to the indoor air coil (now the condenser) through the right bottom part of the reversing valve. Thus the air circulated by the indoor fan will be heated. After passing through the expansion device, the refrigerant enters the outdoor coil at a low temperature. Because the temperature of the refrigerant is low, heat can be transferred from the water to the refrigerant inside the evaporator [Kavanaugh, 2006].

Figure 2.3 - Heating Cycle

Figure 2.3. Heating Cycle (Adapted from: Oklahoma State University)

Figure 2.4 - Cooling Cycle

Figure 2.4. Cooling Cycle (Adapted from: Oklahoma State University)

The advantage of using water from the ground or lake/pond is that backup heat is often unnecessary. If the water loop is connected to a properly sized ground or lake coil loop, the heating efficiency is exceptionally high when compared to conventional systems. Figure 2.5 presents a more anatomically correct diagram of a “water-to-air” heat pump. Note that an additional heat recovery coil or desuperheater can also be added to the GHP unit to partially heat domestic hot water (DHW) with waste heat in the summer and with excess heating capacity in the winter [Kavanaugh, 2006].

However, the heat pump only produces DHW when it is running for either space heating or cooling purposes. The percentage of annual DHW needs met depends upon the run time of the heat pump and DHW usage patterns in a facility. The largest savings occur in applications where the heat pump runs a large number of hours, particularly in cooling mode, and where alternative water heating is by electric resistance. The capacity of the desuperheater is directly related to the heat pump capacity. For an average family size (3.5 persons) with a 3-Ton heat pump, the annual savings on DHW would be in the range of 25% (colder climates) to 35% (warmer climates) or about $100 – $150 per year at $0.08/KWh [Rafferty, 2001].

Figure 2.5 - Ground-Source Geothermal Heat Pump Unit

Figure 2.5. Ground-Source “Geothermal” Heat Pump Unit (Adapted from: Kavanaugh, 2006)

One of the most important characteristics of heat pumps, particularly in the context of home heating/cooling, is that the efficiency of the unit and the energy required to operate it are directly related to the temperatures between which it operates. In cooling, the inlet fluid temperature should be as low as possible to reduce heat pump energy consumption. While in heating mode the inlet fluid temperature should be as high as possible. In other words, the temperature lift across the heat pump which is the difference between the source and load temperatures should be minimized. This is important because it forms the basis for the efficiency advantage of GHPs over air-source heat pumps (ASHPs).

An ASHP must remove heat from cold outside air in the winter and deliver heat to hot outside air in the summer. In contrast, the GHP retrieves heat from relatively warm soil (or groundwater) in the winter and delivers heat to the same relatively cool soil (or groundwater) in the summer. As a result, GHP, regardless of the season is always pumping the heat over a shorter temperature distance than the ASHP. This leads to higher efficiency and lower energy use. The most commonly used GHP unit is the single package water-to-air heat pump as shown in Figure 2.6. All of the components are contained in a single enclosure about the size of a small gas furnace. The single package design is a major advantage over the so-called split system used for ASHP. The lack of an outside unit reduces the amount of refrigerant required and the potential for leaks, which results in a major enhancement to reliability.

Virtually all GHP units use refrigerant R-22 which is considered a transition refrigerant with an ozone depletion value (ODP) of 0.05. High efficiency equipment generally contains a high efficiency compressor, larger air coil, higher efficiency fan motor, and sometimes, a larger refrigerant-to-water heat exchanger. Manufacturers also offer split systems, water-to-water heat pumps, multi-speed compressors, dual compressor, and rooftop versions of this equipment to suit various applications [Rafferty, 2001].

Figure 2.6 - Single Package Water-to-Air Heat Pump

Figure 2.6. Single Package Water-to-Air Heat Pump (Source: WaterFurnace)

2.2.1.2. Distribution System

The second indoor component of a geothermal system is the distribution system that is responsible for moving conditioned air from the heat pump throughout the home. The typical thermal output system in a residential application transfer heat to either a forced air heating/cooling system (a “water-to-air” system), or to a hydronic system for radiant heating, pool heating, or domestic water heating (a “water-to-water” system).

A typical residential system has a 3-ton (36,000 Btu/hr) thermal capacity. Depending on the layout of a given building and the nature of the heating/cooling loads, the building may use either a distributed architecture or a centralized architecture. A distributed architecture uses many small units, each one serving a specific zone or subset of the building space, while a centralized architecture uses fewer and higher capacity units in combination with a traditional distribution system [Goetzler et al., 2012].

Whether it is a forced air or radiant system, an efficient HVAC distribution system is very important for a high performance geothermal system. For radiant systems, pipes must be properly sized, have proper spacing, and have a good thermal connection with the room. For air distribution systems, ducts must be tightly sealed and efficient [Home Owner Guide to Geothermal Heat Pump Systems, Ground Energy Support].

2.2.1.3. System Controls

The most basic type of control system is a heating and cooling thermostat. Programmable thermostats, also called setback thermostats, can be energy savers for homes by automatically adjusting the temperature setting when people are sleeping or not at home. Most of the common Wi-Fi thermostats (e.g. Ecobee®, Nest®) are compatible with geothermal heat pumps. The thermostat selected should be designed for the particular heating and cooling equipment it will be controlling, otherwise it could actually increase energy bills.

A thermostat should be located centrally within the house or zone on an interior wall. It should not receive direct sunlight or be near a heat-producing appliance. A good location is often 4 to 5 feet above the floor in an interior hallway near a return air grille. The interior wall should be well sealed at the top and bottom to prevent circulation of cool air in winter or hot air in summer [Louisiana Department of Natural Resources, 2010].

2.2.2. Outdoor Components

2.2.2.1. Ground Heat Exchanger

Unlike an ASHP with its outside coil and fan, a GHP also called Ground-Source Heat Pump (GSHP), relies on fluid-filled pipes buried beneath the earth as a source of heating in winter and cooling in summer. In heating mode, the GHP pulls heat from the earth and transfers this heat to the indoor air or water, and in cooling mode the heat pump pulls heat from the indoor air and rejects the heat into the ground. This transfer of heat is called Geo-Exchange. The primary undisturbed temperature of the ground heat source is given by the thermal properties (heat conductivity and heat capacity) and hydraulic properties (water and air content) of the subsurface. High porosity and void content of the ground typically reduce the heat conductivity. For example, if the groundwater table is low and the ground is in the vadose (unsaturated) zone instead of the saturated zone, the voids are filled with air instead of water which decreases the heat conductivity of the system [Stober and Bucher, 2013].

Therefore, it is important for engineers to perform a ground thermal conductivity test prior to starting the design of the ground heat exchanger (GHX). In general, steadily flowing groundwater can be expected to be beneficial to the thermal performance of closed-loop ground heat exchangers. The transfer of heat away from the borehole field via a fluid flow will alleviate the possible buildup of heat around the boreholes over time [Chiasson et al., 2000]. The climatic conditions at a home’s location also affect the temperature of the ground heat source. However, a few feet below the surface of the earth the ground remains at a relatively constant temperature all year round. Depending on the latitude of a location, ground temperatures can range from 45 F (7 °C) to 75 F (21 °C). Similar to a cave, the ground temperature is warmer than the air above it during the winter and cooler than the air in the summer [U.S. Department of Energy].

Eliminating the outside equipment means higher efficiency, less maintenance, greater equipment life, less noise, and stronger resilience [Gregor, 2012]. The buried piping in geothermal systems usually has a 25-year warranty. Most experts believe the piping will last longer, because it is made of durable plastic with heat-sealed connections, and the circulating fluid typically has an anticorrosive additive. The actual costs of GHPs vary according to the difficulty of installing the ground loops as well as the size and features of the equipment. Proper installation of the geothermal loops is essential for high performance and the longevity of the system. Therefore, qualified and experienced geothermal heat pump contractors should be used for installation [Louisiana Department of Natural Resources, 2010].

2.2.2.2. Type of Ground Loop

Ground source heat pumps are generally classified by the type of ground loop. Selection of one over another type of ground loop depends mostly on the site characteristics, local regulations, and contractor availability.

Closed-loop heat pumps, also known as ground-coupled heat pumps (GCHPs), are the most common system type. Energy transfer in a GCHP involves four media: indoor air, the refrigerant gas, water in the loop, and the earth mass. Energy must pass through three heat exchangers: the indoor air-to-refrigerant coil, the refrigerant-to-water coil, and the water-to-earth pipe wall.

In the cooling mode, thermal energy flows from the indoor air to the refrigerant, to the loop water, and to the earth. Electric energy that powers the compressor enters the refrigerant gas as heat of compression and sensible heat from the motor and passes on to the earth. The total heat rejected to the earth is the sum of the heat absorbed from the indoor space plus the electrical energy needed to power the compressor.

In heating mode, the compressor heat energy goes into the indoor space along with the heat absorbed from the earth. For every unit of electrical energy needed to drive the heat pump compressor, three to four additional units of heat energy are absorbed from the earth [Braud, 1992]. The Ground heat exchanger (GHX) loop pipe material is typically high-density polyethylene (HDPE). The heat pump controller operates the pumps to circulate the water/refrigerant solution throughout the GHX as necessary to meet the required heating or cooling load. In colder climates, water is usually mixed with refrigerant to prevent the water from freezing. Closed-loop GHXs can have either a vertical, horizontal, or slinky-like configurations, which are laid in the ground or occasionally in a pond or lake. The vertical configuration consists of a loop that runs down the length of a vertical borehole and returns to the top. Each ton of capacity typically requires a single borehole of approximately 150 to 220 feet deep [Rafferty, 2008]. The vertical loop has a smaller ground surface area requirement, typically 200-400 ft² (5- 10 m²/kW), which makes it more feasible for smaller properties but it adds on significant drilling costs to the total installation cost of the system [ASHRAE, 1995].

The major advantage of a vertical loop configuration is that it places the loop in a much more thermally stable zone as the deeper the boreholes, the ground temperature is more consistent. Thermal advantages of the vertical configuration over the horizontal configuration are less of a factor in moderate climates. The more extreme the climate, either in heating or cooling, the greater the advantage of the vertical system [Valizade, 2013].

Horizontal loops lie in trenches four to six feet deep and require 125 to 300 feet of trench per ton of cooling/heating capacity delivered [Rafferty, 2008]. This type of configuration usually represents a less expensive option since it involves less digging. On the other hand, it requires much more space and the ground temperature is more exposed to seasonal fluctuations. The length of pipe necessary is a function of system size, climate, soil/rock thermal characteristics and loop type. The ground surface area for a typical horizontal loop ranges from 2000 ft² to 3500 ft² per ton (50-90 m²/kW) [ASHRAE, 1995].

A variation of the horizontal loop is the spiral or “slinky” loop configuration in which the piping is laid out in an overlapping circular fashion. This configuration requires less ground area but more pipe length and pumping energy than a basic horizontal setup [Valizade, 2013]. Figure 2.7 shows the three different loop configurations, vertical, horizontal and slinky, within the same category of GCHPs. Figure 2.7. Closed-Loop or Ground-Coupled Heat Pumps (GCHP) (Adapted from: Kavanaugh and Rafferty, 1997)

Figure 2.7 - Closed-Loop or Ground-Coupled Heat Pumps (GCHP)

Open-loop systems, also known as ground-water heat pumps (GWHP), pump ground water from a well into the heat pump’s heat exchanger and then re-inject the water back to the aquifer via a second well. In some applications, regulations allow the building owner to reject water into an existing body of surface water, thereby avoiding the need for an injection well.

Surface disposal is the least expensive option; but, even if a disposal well is required, the capital cost is likely to be much less than the cost of a closed loop ground coupled heat pump system. Water quality is also an important issue. Since the water is used directly in the heat pump, the issue of corrosion and/or scaling can be a problem. If the water is hard (>100 ppm of calcium carbonate) or contains hydrogen sulfide, a closed loop system would be a better choice. If the water is good quality and the house is to be served by a well for domestic water, serious consideration should be given to the open loop approach. Figure 2.8 shows the two configurations for GWHPs, one as a two well and the other as a single well with surface disposal [Goetzler et al., 2012]. Figure 2.8. Open-Loop or Groundwater Heat Pumps (GWHP) (Adapted from: Kavanaugh and Rafferty, 1997)

Pond/lake configurations, also known as surface-water heat pumps (SWHP), can use either open-loop or closed-loop architectures. The latter often uses a submerged “slinky” configuration to exchange heat with the water at the bottom of a pond or lake [Goetzler et al., 2012] as shown in Figure 2.9. Figure 2.9. Lake/Pond or Surface Water Heat Pumps (SWHP) (Adapted from: Kavanaugh and Rafferty, 1997)Figure 2.9 - Lake Pond or Surface Water Heat Pumps (SWHP)

Direct Exchange (DX), also known as Direct GeoExchange (DGX) systems are a niche form of closed-loop system that circulate refrigerant from the heat pump directly through buried metal tubing instead of using a secondary glycol/water loop. Advanced DX systems are generally more efficient than systems that use a conventional ground loop. This efficiency gain is due to the lack of a water-circulation pump, which directly reduces electricity consumption, and the lack of a water-to-refrigerant heat exchanger, which decreases the temperature lift. DX loops are also appealing due to lower installation costs. The ground loop itself is smaller and requires less land area. However, DX systems present many technical challenges for designers, installers and building owners. For example, underground leaks of refrigerant pose serious performance and environmental concerns, in addition to the high cost and complexity of locating and repairing such leaks [Goetzler et al., 2012].

Figure 2.8 - Open-Loop or Groundwater Heat Pumps (GWHP)

Estimates indicate that for offices and other similar building types, hybrid systems may provide benefits across the majority of climate regions. Hybrid configurations use a ground loop to meet the entirety of the smaller load in terms of heating and cooling load (most U.S. commercial applications are cooling-dominated). Figure 2.10 shows an example schematic of a hybrid system that utilizes a cooling tower to supplement the ground loop during the cooling season.

Figure 2.10 - Schematic of Hybrid GHP

Figure 2.10. Schematic of Hybrid GHP (Adapted from: Goetzler et al., 2012)

Some large buildings now have systems that use a variety of alternative ground-heatexchanger architectures, including flooded-mine water, municipal wastewater systems, standing column wells, and combinations of various water sources. Despite the need for custom engineering design for each system, utilizing such alternative heat sinks/sources enables greater energy savings and reduces overall costs [Goetzler et al., 2012]. Table 2.1 summarizes the type of ground loops available for GHP systems.

Table 2.1 - Summary of Type of Loop for GHXs

* Hybrid systems can use any type of loop (usually supplement system with cooling tower)

2.2.3. Equipment Sizing

Typically, energy efficient homes require less demand for heating and cooling; so cost savings may be realized by installing units that are properly sized to meet the load requirements. Because energy bills in more efficient homes are typically lower, high efficiency systems may not provide as much annual savings on energy bills and may not be as cost effective as compared to less efficient houses.

It is important to size GHP systems properly as oversized equipment cost more to install, can waste energy and increase energy bills, and may decrease comfort such as providing inadequate dehumidification [Louisiana Department of Natural Resources, 2010]. Therefore, use a sizing procedure such as:

Calculations in Manual J published by the Air Conditioning Contractors Association. Procedures developed by the American Society of Heating, Refrigeration, and Air

Conditioning Engineers (ASHRAE). Software procedures developed by electrical or gas utilities, the U.S. Department of Energy, HVAC equipment manufacturers, or private software companies.

The heating and cooling load calculations rely on the size and type of construction for each component of the building envelope, as well as the heat given off by the lights, people, and equipment inside the house. If a zoned heating and cooling system is used, the loads in each zone should be calculated separately.

Proper sizing also includes designing the cooling system to provide adequate dehumidification. In humid climate, such as the Southern United States, it is critical to calculate the latent load (the amount of dehumidification needed for the home). If the latent load is ignored, the home may become uncomfortable due to excess humidity. The Sensible Heating Fraction (SHF) designates the portion of the cooling load for reducing indoor temperatures (sensible cooling).

For example, in a HVAC unit with a 0.75 SHF, 75% of the energy expended by the unit goes towards cooling indoor air. The remaining 25% goes towards latent heat removal or taking moisture out of the air in the home. Many homes in places such as Louisiana have design SHFs of approximately 0.7, that is, 70% of the cooling will be sensible and 30% latent. Systems that deliver less than 30% latent cooling may fail to provide adequate dehumidification in summer [Louisiana Department of Natural Resources, 2010]. Additionally, the size of the system will dictate the size of the Ground Heat Exchanger (GHX).

2.3. Standards and Certifications

2.3.1. Performance Ratings

All heat pumps are rated by the American Refrigerant Institute (ARI). For GHPs, results are published every six months in the Directory of Certified Applied Air Conditioning Products. Cooling performance is defined by the index EER which means Energy Efficiency Ratio. The EER is the cooling effect produced by the unit (in Btu/hr) divided by the electrical input (in Watts), which measures the number of Btu’s removed by one Watt of electricity (Btu/Wh). Electrical input includes operating the compressor and fans, and a “pumping” allowance (for the groundwater or ground loop).

Heating performance is defined by the coefficient of performance (COP). COP is the heating affect produced by the unit (in Btu/hr) divided by the energy equivalent of the electrical input (in Btu/hr) resulting in a dimensionless value. COP also includes allowance for pumping. Both the COP and EER values for GHPs are valid only at the specific test conditions used in the rating.

COP and EER are single point values and therefore cannot be directly compared to seasonal values such as the seasonal energy efficiency ratio (SEER) or the heating seasonal performance factor (HSPF), which are published for air-source equipment. Table 2.2 summarizes typical installed costs for GSHPs and ASHP at typical and best efficiency levels [Rafferty, 2001].

Table 2.2. Typical and Best Efficiency Levels and Installation Cost of GSHP and ASHP (Source: Cooperman et al., 2012)

Table 2.2 - Typical and Best Efficiency Levels and Installation Cost of GSHP and ASHP

2.3.2. Heat Pump Efficiency Standards

There are a few industry standards that specify the minimum energy efficiencies of GSHP units in ground water and ground loop applications, including ASHRAE standards 90.1 (2010) and 189 (2010), as well as the Energy Star standards of the Environmental Protection Agency (EPA).

Heat pump efficiencies shall be measured in accordance with the ISO/AHRI/ASHRAE

Standard 13256-1 (for water-to-air heat pumps) and 13256-2 (for water-to-water heat pumps). Federal and local governments adopt the minimum efficiencies specified in these standards in their related building energy efficiency codes, procurement requirements, and/or qualifications for financial incentives.

For example, the Energy Star certification is a prerequisite for obtaining the federal tax credits for GSHP installations. The Energy Star minimum efficiency requirements for GSHP equipment at various applications are listed in Table 2.3. Currently, more than 3,600 GSHP models have been certified by the ENERGY STAR® standard.

Table 2.3. ENERGY STAR Minimum Efficiency Requirements of GSHP Equipment  Source: www.energystar.gov)

Table 2.3 - ENERGY STAR Minimum Efficiency Requirements of GSHP Equipment

2.3.3. System Design and Performance Evaluation Standards

The International Ground Source Heat Pump Association (IGSHPA), located at Oklahoma State University, originally developed and maintains a series of manuals and tools for the design and installation of GSHP or GHP systems that use closed-loop (horizontal or vertical) GHXs for residential and light commercial buildings. The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) has published several guides on the design, operation, and commissioning of commercial GHP systems. ASHRAE also maintains a chapter dedicated to the application of GHP technologies in its Handbook of HVAC Applications [ASHRAE, 2011].

The National Ground Water Association (NGWA) has published guidelines for the construction of vertical boreholes for closed-loop GHP systems, the scope of which includes loop field design, test holes and samples, borehole construction, piping, borehole grouting, loop field identification, and permanent loop piping decommissioning [NGWA, 2009]. These publications have been widely accepted by the United States GSHP industry. Properly sizing the closed-loop GHX is very important as this component represents a significant share of the overall system cost. The sizing methodology needs to account for many factors, including the heat rejection and extraction loads, the physical layout of the GHX, the thermal properties of soil/rock formation at the job site, and the thermal properties of the grouting material. Several software programs are used in the U.S. to size closed-loop vertical borehole GHXs, including GLHEPRO, GlheCal, EES, GLD, and GeoDesigner. These software programs require the user to provide building heating and cooling loads at design conditions and estimates of the cumulative loads.

In addition, these software programs cannot perform a comprehensive energy analysis of a whole building with a GHP system. There are a few integrated simulation tools, such as eQUEST, TRNSYS, and EnergyPLUS, that can be used in sizing the GHX and optimizing the design of GHP systems [Liu et al., 2015].

2.3.4. Professional Certification Standards

Proper professional licenses or certifications are usually required in the U.S. to design and install GHP systems, especially for commercial projects. In all states, it is required that designers of GHP systems must be registered Professional Engineers, and in some states they must also be accredited by IGSHPA as Certified Geo Exchange Designers (CGD). Many states require that ground loop installers be IGSHPA-accredited installers and/or drillers and that the installer of the indoor portion of the GHP system be an HVAC technician certified by the Air-Conditioning Contractors of America. Recently, the Geothermal Exchange Organization developed the first national certification standard for all the disciplines involved in GSHP projects [Liu et al., 2015].

2.4. Geothermal Heat Pump Market Overview

2.4.1. Global Market Development

The growing awareness and popularity of GHPs has had a significant impact on the direct-use of geothermal energy. The installed capacity grew 1.51 times from 1995 through 2015 at a compound annual rate of 8.65%. This is due, in part, to better reporting and the ability of geothermal heat pumps to utilize groundwater or ground coupled sources anywhere in the world.

Table 2.4 provides the five leading countries in terms of installed capacity in thermal megawatts

(MWt) of heat pumps. The leading countries in terms of annual energy use in Terajoules per year

(TJ/year) with heat pumps are: China, USA, Sweden, Finland, and Germany [Lund et al., 2015].

Table 2.4. Worldwide Leaders in the Installation of GHPs (Source: Lund and Boyd, 2015)

Table 2.4 - Worldwide Leaders in the Installation of GHPs

Around US$ 20 billion were reported as invested in geothermal energy by 49 countries during the period 2010-2014, for both direct use and power, doubled the amount from 2005 to 2009 for 46 countries. The average was US$ 407 million per country, with countries investing over US$ 500 million (or US$ 100 million per year) being: Turkey, Kenya, China, Thailand, USA, Switzerland, New Zealand, Australia, Italy and South Korean (in descending order).

In terms of categories of investment: 28.3% was for electric power utilization in 16 countries, 21.8% was for direct-use in 32 countries, 25.6% was for field development including production drilling and surface equipment in 32 countries, and 24.4% was for R&D including surface exploration and exploratory drilling in 48 countries [Lund et al., 2015]. In regards to U.S. geographical distribution, GHPs are used in all 50 states and the District of Columbia. About 52% of domestic GHPs shipments went to ten states: Florida, Illinois, Indiana, Michigan, Minnesota, Missouri, New York, Ohio, Pennsylvania, and Texas. The split between the cumulative residential and commercial GHPs applications by 2012 is 3.5:1 [Navigant Consulting, 2013]. It is estimated that 75% of residential applications are in new construction and 25% in retrofits of existing homes [Ellis, 2008].

A recent Navigant Research report (2013) indicates that the United States represented 29% of global GHP installations by capacity with 13,564 MWt (3.9 million tons) installed in This corresponds to roughly 199 million m² (2.14 billion ft²) of building floor space [Liu et al, 2016].

In the United States, there are 27 known domestic manufacturers of GHP equipment [US EIA, 2010]. Small packaged or split water-to-air heat pump units with cooling capacities ranging from 0.5 to 20 tons (1.74 – 70 kW) are most common in the United States. The efficiency and applicability of GHP units have been improved in recent years as a result of a number of technological advancements, including inverter-compressor technology with communicating controls, along with improvements and refinements to refrigerant coils and to all aspects of variable-speed motors [US EIA, 2010 and Liu et al., 2015]

A report issued by Priority Metrics Group (2009) estimated that the GHP market in the United States was approximately $3.7 billion in 2009, which includes the costs for design, equipment, and installation. A few surveys [Kavanaugh 1989, Huttrer 1994, Kavanaugh et al. 1995, and Kavanaugh et al. 2012] have been conducted in the U.S. to collect cost information for GHP systems. According to the study [Kavanaugh et al., 2012], the average cost of a commercial GHP system increased by 129% from 1995 to 2012. This same study determined that the cost increase (177%) for the interior portion of the GHP system (including the heat pump and other major equipment, controls, piping, and ductwork) exceeded the cost increase for the closed-loop portion (52%) over the 17 year period.

The typical price, in 2006 dollars, of a GHP system installed in a new home is in the range of $3000-5000 per ton; the average price for large-scale housing retrofits of GHP systems is $4600 per ton [DOD, 2007]. The simple payback period for a GHP retrofit project in the United States is usually 8-14 years [DOD, 2007 and Liu, 2010]. For new construction, the payback period is shorter than retrofits, as a payback period of 5 years or more is common [Hughes, 2008].

The cost of a GHP system in the U.S. is about 2-3 times higher than similar GHP system in China. In China, the GHP industry has experienced explosive growth since 2005 due to strong promotion and financial incentives offered by the Chinese central government for renewable energy technologies such as GHPs. The cumulative building floor space conditioned by GHP systems in China grew from zero to 4.3 billion square feet in just one decade. The high growth rate may even increase in the future because of increased mandatory requirements and governmental investment in fighting the severe air pollution found in China [Liu et al., 2015].

2.4.2. Status of U.S. GHP Industry

The U.S. GHP industry began to take shape in the early 1970s by general contracting and manufacturing entrepreneurs. The GHP industry includes manufacturers of water-source (geothermal) heat pumps, HDPE piping and fittings, circulating pumps, and specialty components, as well as the design infrastructure, an installation infrastructure, and various electric utilities. Currently these infrastructures only exist in some localities, and elsewhere customers lack access to the technology [Hughes, 2008]. The small group of manufacturers presented in Table 2.5 is believed to produce most GHP units. Other major brands, such as Carrier, participate in the GHP market by sourcing water-source heat pump units from other manufacturers. The manufacturing base for HDPE pipe is large and well-established. Circulating pumps, propylene glycol antifreeze, plate heat exchangers, fluid coolers, and many other products used in GHP systems are already massproduced to serve markets much larger than the GHP market [Liu, 2010].

Table 2.5. GHPs and HDPE Pipe Manufacturers

The economic impact of ground-coupled technology is truly unique. It is not sophisticated, high technology. It is good for local business. A new trade – ground loop contracting is needed to provide the ground-coupling. Bore drilling gives work to small water well drillers. Pipe installation, trenching, and other loop work use small contractors and local labor. The dollars the customer invests in ground-coupling feed the local economy instead of paying for a new large distant electric power plant [Braud, 1992].

Some regions of the country have their own regional geothermal professional organizations. Members of these organizations, presented in Table 2.6 are committed to furthering their industry.

Table 2.6. Regional Geothermal Professional Organizations

Table 2.6 - Regional Geothermal Professional Organizations

As seen in the previous table, there is no regional geothermal professional organization representing southern states, even though from a scientific and technical point of view the potential for wide applications of GHP systems in hot and humid climate is significant [Tao and Zhu, 2012]. The IGSHPA provides access to their business directory of accredited installers, designers, and contractors. Table 2.7 summarizes the information found in the IGSHPA database for US southern states.

The number of accredited installers in the state of Louisiana is the second lowest after Mississippi, and in huge disadvantage compared to Texas. These results illustrate the lack of knowledge that HVAC contractors, as much as building owners, have in GHP systems and therefore the inevitable poor market competition within the HVAC industry in Louisiana.

Table 2.7. IGSHPA Business Directory for U.S. Southern States

Table 2.7 - IGSHPA Business Directory for U.S. Southern States

State Accredited Installer Trainer Certified GeoExchange Designer Vertical Loop Installer Certified Geothermal Inspector

In regards to academia, there is not much evidence of previous research work of GHPs in Louisiana, except by an independent study (1998) prepared for the U.S. Department of Energy by Oak Ridge National Laboratory. The study is about the installation of over 4,000 GHPs at the U.S. Army’s Fort Polk military base in Leesville, LA; the world’s largest installation of GHPs at the time (1996).

Smaller and less detailed case studies of GHPs in Louisiana can be found in research work of Braud (1992) and Smilie (1984). Harry J. Braud was a professor in the department of Agricultural Engineering at Louisiana State University, Baton Rouge. Most of his geothermal research publications are from the late 80s and early 90s. Nevertheless, the design of GHPs as well as the market barriers described in the study published by professor Braud has remained very much the same.

In the past decades research efforts regarding GHPs in Louisiana has decreased to almost zero. This might be one of the main reasons for the low awareness of the applications of GHPs in Louisiana, thus, for the low market penetration in this state. Hughes study (2008) surveyed GHP industry experts and were asked to respond the question: What are the key barriers to rapid growth of the GHP industry? The most important identified barrier was the high first cost of GHPs to consumers and the given solution was to assemble independent, statistically valid, hard data on the costs and benefits of GHPs.

Given the need for data, a new sector in the GHP industry emerged. This relatively new sector is composed by companies that specialize in web-based GHP monitoring to track system performance. Ground Energy Support, for instance, developed a monitoring system called GxTrackerTM that monitors the basic operations of geothermal heating and cooling system and displays this real-time information online. The purpose of a monitoring system is to enable homeowners to insure that the heat pump system is providing the optimal return on investment.

2.4.3. Key Barriers

Initial cost and long payback periods clearly limit GHP system acceptance in many markets. Currently in commercial markets, GHPs are primarily limited to institutional customers (e.g., federal, state, and local governments and K-12 schools) that take the lifecycle view of a GHP system. In residential markets, GHPs are limited to a small subset of newly constructed homes that the builder plans to occupy and thus wants to equip with the best available system, and to home retrofits in which the owner plans to occupy the premises long enough to justify the investment [Liu, 2010].

While loop cost appears to be a major reason for higher first cost, the $5,400 “indoor” equipment cost should be approximately the same as the $4,000 typical first cost of a conventional system given the essentially equal complexity of the equipment and installation [Kavanaugh and Gilbreath, 1995]. Many new HVAC market entrants require additional resources and/or knowledge for safe and correct installation. Without knowledge of, and experience with, of GHP systems and equipment, installers are hesitant to advertise and sell such systems. Furthermore, inexperienced designers tend to oversize GHP systems and/or add excessive backup capacity to provide a larger safety margin, but doing so unnecessarily increases their cost [Liu, 2010].

The lack of public awareness and trust in non-conventional HVAC systems directly leads to low motivation to invest in GHP systems. Given the large proportion of unmotivated consumers and inexperienced design and installation professionals, the GHP supply chain must educate consumers and even provide extra technical assistance for the design and installation of GHP systems. These extra selling and training costs are then included in the prices of GHP products [Liu, 2010].

Reductions in GHP system cost, improvements in installation quality, greater competition, and improved market penetration have occurred primarily in the areas that have been involved with GHPs for several years. The first cost of GHPs in areas that do not have established contractors and designers is often prohibitively high. These relatively high costs cannot be economically justified by many potential customers. Thus, the GHP industry in these areas does not develop sufficiently to support loop and HVAC contractors who will invest in the equipment and training necessary to install GHPs effectively [Kavanaugh and Gilbreath, 1995]. Consumers who make purchase decisions based primarily on first cost will not be likely candidates for purchase of higher cost equipment that can save them on operating costs. While part of this barrier can be overcome through greater consumer education and awareness of energy benefits, first-cost barriers must also be addressed directly [Goetzler et al., 2014]. Recommendations are to concentrate on reducing the cost of the components with the greatest potential (heat pumps, indoor installation, and pumps) instead of overemphasize low36 cost loops at the expense of quality. GHP manufacturers have to find a way to reduce costs in order to become more competitive compared to high efficient air-source systems. Additional suggestions are to involve experienced contractors in loop research & development for affordable housing projects [Kavanaugh and Gilbreath, 1995].

2.4.4. Policies and Incentives

State and Federal government organizations typically use tax incentives, such as property and sales tax incentives, and tax credits to offset the costs of purchasing, installing, and/or owning a geothermal heating and cooling system. The residential renewable energy tax credit established by The Energy Policy Act of 2005, initially applied to solar-electric systems, solar water heating systems and fuel cells. However, the Energy Improvement and Extension Act of 2008 extended the tax credit to small wind-energy systems and geothermal heat pumps, effective as of January 1, 2008. The credit was further enhanced in February 2009 by The American Recovery and Reinvestment Act of 2009, which removed the maximum amount for all eligible technologies (except fuel cells), placed in service after 2008 [DSIRE, 2017].

In 2015, the US federal government extended similar tax credits for commercial and residential solar energy installation, but for geothermal heat pumps and other clean energy technologies stopped at the end of December 2016. According to Doug Dougherty, President of the Geothermal Exchange Organization (GEO), geothermal heat pumps are 100% ‘Made in the USA’ with American-made components manufactured and installed by American workers. Without reinstatement and extension of federal tax credits, the entire geothermal supply chain, including manufacturers, distributors, dealers, contractors, installers, drillers – plus all the families and small businesses that they support – will all see loss of investments and jobs [GeoExchange, 2017].

The geothermal industry is currently working towards the reinstitute and extension of commercial and residential installation tax credits geothermal heat pumps through 2021. Table 2.8 presents a few federal policies in place that apply to geothermal heating and cooling technologies (ground source heat pumps, direct-use). Additionally, the Database of State Incentives for Renewables and Efficiency (DSIRE) contains further information on state, local, utility, and federal incentives and policies that support renewable energy and energy efficiency,

Table 2.8. Current Federal Policies for Geothermal Technologies (Source: National Renewable Energy Laboratory, www.nrel.gov)