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Ground Source Heat Pumps: Systems and Applications

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1 Ground Source Heat Pumps: Systems and Applications
Gary Phetteplace, PhD, PE GWA Research LLC Lyme, NH 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

2 Efficiency Vermont is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request. This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation. AIA Providers can use their own powerpoint template as long as it doesn’t have your company logos. To personalize this slide, please insert your company name in the purple area. You may change the color used in the text. All other wording on this slide is mandatory and cannot be changed.

3 At the end of this program, participants will be able to:
Learning Objectives At the end of this program, participants will be able to: Understand the Northeast's Best Practices for Geothermal Heat Pumps Be proficient in Design, Installation & Operational best practices (Loads, sizing, ventilation, controls, energy consumption, routine maintenance) Understand the importance of pumping in the design of an efficient Geothermal heat pump system. Understand the lessons learned from practical experience To personalize this slide, please insert your four learning objectives in the purple area on this slide. You may change the color used in the text. Be sure that these four learning objectives are identical to the ones that were submitted on the course registration. Please remove the “sample slide” lingo from the upper right hand corner of the page.

4 Course Evaluations In order to maintain high-quality learning experiences, please access the evaluation for this course by logging into CES Discovery and clicking on the Course Evaluation link on the left side of the page. As a new requirement, Providers are required to encourage members to complete the online CES Discovery Evaluation. You may still use your own paper evaluation form to collect feedback for your personal records, however our online evaluation must still be encouraged.

5 Now for my “Expectation Management” Slide
Introduction to: the most common types of ground-source heat pump systems and a few of their design details/issues. Level of detail is NOT SUFFICIENT for system design, nor is coverage close to complete. Intent is that participant will start to become a more intelligent consumer of the technology. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

6 Commercial Vs. Residential
Much of what I will say today is applicable to both commercial scale and residential scale systems however this is a bit more focus on commercial scale systems Commercial scale geothermal heat pump systems offer some challenges that residential systems do not Commercial scale systems also offer many more opportunities and in general better economics 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

7 Geothermal Heat Pumps and Geothermal Energy
Geothermal heat pumps should not be confused with “true Geothermal Energy”. True geothermal energy is normally in the form of hot water or steam geysers or hot springs that may be used directly for space heating, agriculture/aquiculture, and even in some cases electric power generation. To a varying degrees geothermal heat pumps make limited use of energy from the earth, however largely they use the earth as an energy storage device. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

8 Heat Pumps and how they work
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

9 (c) Gary Phetteplace, GWA Research, LLC
Fundamentals Heat normally flows from regions/bodies at warmer temperatures to colder ones, analogous to water flowing down hill. If we want to make heat move in the opposite direction on the temperature scale, energy must be input, just as we must input energy to move water to a higher elevation. Moving heat up the temperature scale is the purpose of a heat pump, air-conditioner, or refrigerator. In terms of the basic physics involved they are all the same, the nomenclature is strictly a function of the application. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

10 (c) Gary Phetteplace, GWA Research, LLC
Heat pumps, Air-Conditioners, and Refrigerators: what’s the difference? Purpose Heat Source (Tc) Heat Sink (Th) Refrigerator Cool interior of refrigerator Interior of refrigerator Room Air Air-Conditioner Space Cooling Room air Outdoor air or other Heat Pump Space Heating 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

11 So how does a heat pump or refrigerator work?
It’s some thermodynamic trickery that is called a “vapor compression cycle”. This cycle basically exploits the fact that at lower pressures liquids boil at lower temperatures. Just as water boils at a lower temperature at 10,000 feet where the atmospheric pressure is lower, a refrigerant behaves the same way. Forcing the refrigerant around a cycle between two temperatures by changing it’s pressure allows heat to be transferred up the temperature scale. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

12 Diagram of how a Heat Pump works
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

13 So what does a Heat Pump look like?
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

14 A diagrammatic representation of a Water-to-Air Heat Pump
Courtesy of Steve Kavanaugh 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

15 Geothermal Heat Pump Basics
Courtesy of Steve Kavanaugh 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

16 Why is a heat pump advantageous?
It turns out that if you don’t need to move the heat very far up the temperature scale, it takes a lot less energy to do so than to create the heat by another means (i.e. burn fuel). A “lot less” is the order of one third or one forth. It’s also a simple matter to change the direction of the refrigerant flow such that a heat pump can provide both heating and cooling; i.e. air-conditioning becomes part of the system at negligible extra cost. In larger buildings like schools, multiple heat pumps are often connected to a single circulating loop of water and not only is it possible for one unit to be heating while another cooling, it’s advantageous. Efficiency is increased because it’s possible to move much of the heat around with water instead of air. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

17 Measure of heat pump performance: COP (coefficient of performance)
Useful heat effect may be heating, cooling, or hot water heating for example. Energy input is normally in the form of electricity. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

18 (c) Gary Phetteplace, GWA Research, LLC
Heat Pump Performance 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

19 (c) Gary Phetteplace, GWA Research, LLC
COP Vs EER The EER is a parameter with an inconsistent set of units which the air-conditioning industry prefers because it makes cooling performance look better. The COP can be found by dividing the EER (expressed in Btu/hr of output per Watt of input) by The COP is dimensionless. The COP is used in Europe. If you get the idea that I think using the EER is stupid, you are right. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

20 Cooling Equipment Capacity
Cooling equipment capacity is normally expressed in “Tons” A “Ton” of cooling is equivalent to 12,000 Btu/hr The “Ton” is carried over from the earliest days of ice based refrigeration and is equivalent to the amount of refrigeration effect that is derived from thawing 2000 lbm of ice in one day Cooling capacity outside of the North America is expressed in kW, which is more rational 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

21 The ground as a heat source
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

22 Example calculated soil temperatures
Note: This is not a generalized result, it is based on a number of assumptions – DON’T USE THIS FOR YOUR APPLICATION. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

23 Some measured soil temperatures
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

24 Summary thoughts on the ground as heat source/sink
Stable temperatures even at moderate depths are very favorable for heat pumps. The ground has a relatively high capacity to accept/provide heat, but an understanding of how to accomplish the heat exchange is required. When compared to ambient air as a heat source/sink, the ground is far superior due to stable temperatures. With outdoor air the demand for heating/cooling is exactly coincident with it’s ability to provide the opposite and it’s inability to provide what is needed. Air-Source heat pumps are largely responsible for the bad rap that heat pumps have taken in years past. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

25 (c) Gary Phetteplace, GWA Research, LLC
Basic System Types 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

26 Terminology Slide courtesy of Kevin Rafferty 10 February 2011
One of the places where we shot ourselves in the foot. Slide courtesy of Kevin Rafferty 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

27 CLOSED LOOP Vertical Ground Coupled
Advantages low land area requirement. stable deep soil temperature. adaptable to many sites. Disadvantages may have high cost. does not work well in some geological conditions. needs experienced vertical loop installer. That is often not your conventional well driller. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

28 CLOSED LOOP Horizontal Ground Coupled
Advantages may have lower first cost. less special skills. less uncertainty in site conditions, but soil conditions can vary seasonally. Disadvantages high land area requirement. limited potential for HX w/groundwater. wider seasonal temperature swings, lower efficiency. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

29 CLOSED LOOP Slinky Ground Coupled
Advantages those of horizontal ground-coupled. but less land area. adaptable to wide range of construction equipment. Disadvantages lots of pipe and pumping. widest seasonal temperature swings, lowest efficiency. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

30 (c) Gary Phetteplace, GWA Research, LLC
Surface Water Systems Advantages Low first cost Direct cooling may be possible Disadvantages Fishermen Wide seasonal temperature swings, high imbalance in heating/cooling performance Commercial-scale systems require significant water bodies (Illustration from Kavanaugh and Rafferty, 1997) 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

31 (c) Gary Phetteplace, GWA Research, LLC
OPEN LOOP Ground Water 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

32 Open loop ground water system
Advantages May have lowest first cost, especially for large loads Stable source temperature, high efficiency Some direct cooling possible Oldest, lots of experience (a lot of the early systems had problems, most of which would have been solved by a heat exchanger isolating the ground water) Disadvantages Environmental requirements may be tougher Site specific Poor water quality can cause difficulties, isolating ground water from heat pumps is often necessary 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

33 (c) Gary Phetteplace, GWA Research, LLC
Standing Column Well This system is, in concept, a cross between a vertical ground-coupled system and a open loop ground water system: @ 0% bleed it’s like a ground-coupled system using the water directly for the ground coupling, except it only engages the ground from the static water level down and there may be some losses in potential heat transfer due to stratification/poor mixing. @100% bleed it’s an open loop system with disposal at the surface. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

34 (c) Gary Phetteplace, GWA Research, LLC
Standing Column Well Advantages An alternative in areas with high drilling costs and formations producing limited amounts of water Disadvantages Limited ground-coupling Site specific, may require multiple, deep wells Poor water quality can cause difficulties Bleed water disposal may be problematic Pumping costs will be high at high bleed rates Inadequate design criteria 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

35 Brief Overview of Design Issues for Ground-Coupled Systems
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

36 Design of the ground-coupling
Sizing of the ground-coupling for a heat pump is different than sizing conventional equipment. The capacity of the ground to absorb or provide heat is a transient heat transfer problem. The thermal state of the ground is determined by prior heat addition/extractions rates and durations. While significant imbalance of heat extraction/heat rejection can be tolerated, the long term impacts must be considered. The ground can not be assumed infinite and the interaction of adjacent borehole heat exchangers is very important for commercial scale systems. Bottom line is that we need to know the load duration information as well as peak load and we need a design tool that appropriately considers all these factors as well as accurately models the heat transfer in the ground. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

37 (c) Gary Phetteplace, GWA Research, LLC
Information required for design of ground-coupled HVAC Vs conventional HVAC system Conventional fossil-fuel fired Fuel availability Maximum (design) heat load Maximum cooling load Ground-coupled “Block” loads, their timing and duration, heating and cooling combined, possibility domestic hot water as well Thermal properties of the ground Undisturbed ground temperature Geology and it’s impact on drilling Heat pump performance Tentative ground-coupling layout consistent w/site Planned borehole design including sizing, grouting, backfill, etc. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

38 Design of the ground-coupling
(Courtesy of Steve Kavanaugh) 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

39 Vertical Ground-Loop Design
Design software essential for commercial- scale systems. Sources: GchpCalc Version 4.2, Energy Information Services, $300 GLHEPRO V.3.0, International Ground Source Heat Pump Association (IGSHPA), $500 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

40 Other Ground-Loop Considerations –Piping
High Density Polyethylene (HDPE) piping is only piping acceptable for use, see ASHRAE manual for Specs. All joints that are buried in the ground must be fused, mechanical types of joints like barbed fittings and clamps should never be used. Fusion joints are typically butt fused but sometimes socket fused joints are used on the smaller diameters. Buried vaults are sometimes used to allow isolation and testing remote from the building and supply and return piping from that point to the building. A high capacity pump is used to flush each borehole heat exchanger (or a few if in series) before they are connected to the headers. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

41 Sub-header manifolding school project near Reno, NV
(Courtesy of Lisa Meline) 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

42 Other Ground-Loop Considerations –Thermal tests
Through site characterization, including test boring is advisable, especially where little is known about the geological conditions at the job site. For larger projects, 25 tons or more, in-situ thermal properties tests will probably be justified. Much can be learned about drilling conditions from this as well and the test well can be integrated into final well field. Recommendations for thermal properties testing requirements and methods can be Found in Chapter 32 of the 2007 ASHRAE HVAC Applications Handbook. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

43 Other Ground-Loop Considerations –Thermal tests
(Illustration from Kavanaugh and Rafferty, 1997) 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

44 Thermal properties test apparatus
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

45 (c) Gary Phetteplace, GWA Research, LLC
Pumping energy can destroy the efficiency of an otherwise efficient system (from Kavanaugh and Rafferty, 1997). 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

46 Summary thoughts for closed loop ground-coupled systems
Do not undersize (or oversize) the loop field Use Energy Star rated heat pumps Think system efficiency and try for an “A” grade in pumping Conduct thermal conductivity tests for larger commercial scale jobs Use design software for larger commercial scale jobs Don’t fall pray to what appears to be heat transfer magic 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

47 Overview of Design Issues for Ground Water Systems
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

48 (c) Gary Phetteplace, GWA Research, LLC
Open Loop system types (Illustration courtesy Kevin Rafferty) 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

49 (c) Gary Phetteplace, GWA Research, LLC
Open loop system cost is a strong function of system size, ground coupled system cost is essentially flat (Illustration courtesy Kevin Rafferty) 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

50 (c) Gary Phetteplace, GWA Research, LLC
When determining water flow rate there is a trade off between heat pump efficiency and pumping costs. Thus an optimum water flow rate exists 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

51 (c) Gary Phetteplace, GWA Research, LLC
The optimum flow rate will be lower for deeper static levels within the well 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

52 Open Loop Design Issues Summary
Site Regulatory issues Drill and test early Building Design for block load Building loop pump – 7.5 hp or less per 100tons Use small heat pump units (< 6tons) Use efficient heat pump units (Energy Star rated) Groundwater Flow (usually 1-2 gpm/ton) Chemistry – analysis, previous experience, sand removal Pressurization Isolation – heat exchanger (2 to 4F approach) Wells Production well pump control Production/injection separation Geohydrologist consultant needed? (Slide courtesy of Kevin Rafferty) 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

53 Summary of Ground-Source vs. Conventional Systems
GSHP Advantages Ideal zone control Simple, highly reliable controls and equipment Low operating cost Low maintenance Less floor area requirements No on site fuel Green technology Heat recovery hot water heating possible GSHP Disadvantages Higher first costs compared to some systems Experienced designers and design guidance limited Installation infrastructure regionally inadequate 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

54 (c) Gary Phetteplace, GWA Research, LLC
Economics 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

55 DoD GCHP installations
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

56 (c) Gary Phetteplace, GWA Research, LLC
Climate Zones 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

57 Payback by Climate Zone
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

58 (c) Gary Phetteplace, GWA Research, LLC
How do the energy trends favor GSHP? Phetteplace’s Normalized Energy Costs 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

59 Electric generation mix in the US
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

60 Relative Heating Costs for Phetteplace’s Energy Costs
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

61 Environmental Benefits
Often overstated in terms of being renewable Remember the heat pump does not make or convert energy, it just moves it around and that uses energy that may not be renewable Thus its carbon footprint will be derived from the driving energy input source (i.e. electricity). That’s not all bad news as the next slide shows. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

62 CO2 emissions for various means of Heating
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

63 Closing Remarks and References
10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

64 Advice on Selecting Designers
These systems are actually quite simple, but they are entirely foreign to many HVAC designers, especially in some regions of the US the Northeast being one of them. The inexperienced designer usually attempts to treat these systems like other HVAC systems; if that’s the case results may suffer in terms of: Low efficiency Higher first cost Both of the above Worse case not even work, or fail prematurely As a consumer, the most prudent thing you can do is get someone who has demonstrated they know these systems and can design/install successful ones, for commercial systems require a trained PE. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

65 Advice on Selecting Designers (Cont.)
For residential systems the design will often be done by the installer, again look for someone who has demonstrated they know these systems and can design/install successful ones. Do not accept systems that are geothermal in name only, for example: A ground loop has been connected to a chiller and a central air handling system There is too little ground coupling and backup systems are responsible for satisfying much of the load Avoid systems with elaborate and expensive controls: distributed heat pumps do not need more than thermostats for control. Insist on minimum provisions such as pressure and temperature ports (P&T ports or Pete’s Plugs) for trouble shooting. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

66 Advice on Selecting Designers(Cont.)
For both residential and commercial, be wary of “one trick horses”. If they do not know of the major types of systems and can not explain to you how they arrived at the one they are recommending for you, look for someone else who can. Consider bringing both design and installation expertise in from other areas if the infrastructure is lacking in your part of the country, for larger systems it will usually be an investment well worthwhile both in terms of achieving a successful system and often in terms of reducing costs. If you do not feel completely comfortable in judging designer/installer qualifications, seek the advice of an expert. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

67 Advice on Selecting Designers: Commercial Systems
For commercial design make sure your designer has taken a short-course on design of these systems Be sure the designer obtains a copy of one of the recommended design software programs and training on how to use it. For commercial scale systems do not size ground-coupling based on rules-of-thumb, manufacturers recommendations, etc. Check to see that the designer has obtained copies of the accepted design guides and uses them, some are listed at the end of this presentation. If he/she has questions be sure they consult an experienced designer. Do not let the designer make the systems overly complicated by adding unnecessary backup, redundancy, unnecessary controls, etc. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

68 Advice on Selecting Installers
Again, as a consumer, the most prudent thing you can do is get someone who has demonstrated they know these systems and can install successful ones. Check references and ask not only how well the system works but how much energy it is using. For commercial scale or large residential developments consider bringing installation expertise in from other areas . IGSHPA certification of the installer is a necessary but not sufficient condition. Attempt to find installers who will take responsibility for both the interior and exterior portions of the system, either within their organization or with established partners. Monitor the installation. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

69 (c) Gary Phetteplace, GWA Research, LLC
References Recommended design references: 2007 ASHRAE Handbook, HVAC Applications. Chapter 32 – Geothermal Energy. American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), Atlanta, GA. Kavanaugh, Steven and Kevin Rafferty. (1997). Ground source heat pumps—design of geothermal systems for commercial and institutional buildings. American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), Atlanta, GA. Recommended survey article: Phetteplace, G. (2007). Geothermal Heat Pump Technology, Journal of Energy Engineering, Vol. 133, No. 1, pgs , American Society of Civil Engineers. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

70 (c) Gary Phetteplace, GWA Research, LLC
Credits Kevin Rafferty, Engineering Consultant, Klamath Falls, OR. (See heatspring.com for design course offerings) Steve Kavanaugh, Energy Information Services, (See heatspring.com for design course offerings) Kirk Mescher, CM Engineering, Columbia, MO , Lisa Meline, meline engineering, Sacramento, CA , 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC

71 (c) Gary Phetteplace, GWA Research, LLC
Thank You! Contact Information: Dr. Gary Phetteplace, PE GWA Research LLC 7 Masa Morey Lane Lyme, NH 03768 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC


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