Ground Source Heat Pumps: Systems and Applications

1. Ground Source Heat Pumps: Systems and Applications 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 1

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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 Slide 5

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 Slide 6

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 Slide 7

8. Heat Pumpsand how they work 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 8

9. 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 Slide 9

10. Heat pumps, Air-Conditioners, and Refrigerators: what�s the difference? 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC 10

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 11

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

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

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

15. Geothermal Heat Pump Basics 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 15

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 Slide 16

17. Measure of heat pump performance: COP (coefficient of performance) 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 17

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

19. 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 3.412. 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 Slide 19

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 Slide 20

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

22. Example calculated soil temperatures 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 22

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

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 Slide 24

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

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

27. CLOSED LOOP Vertical Ground Coupled 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 27

28. CLOSED LOOPHorizontal Ground Coupled 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 28

29. CLOSED LOOPSlinky Ground Coupled 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 29

30. 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 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC 30

31. OPEN LOOPGround Water 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 31

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 32

33. 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 33

34. 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 34

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

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 Slide 36

37. 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 Slide 37

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

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

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 Slide 40

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

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 Slide 42

43. Other Ground-Loop Considerations �Thermal tests 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 43

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

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

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 Slide 46

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

48. Open Loop system types 10 February 2011 Slide 48 (c) Gary Phetteplace, GWA Research, LLC

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

50. 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 Slide 50 (c) Gary Phetteplace, GWA Research, LLC

51. The optimum flow rate will be lower fordeeper static levels within the well 10 February 2011 Slide 51 (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? 10 February 2011 Slide 52 (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 53

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

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

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

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

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

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

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

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 Slide 61

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

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

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 Slide 64

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 Slide 65

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 Slide 66

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 Slide 67

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 Slide 68

69. 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. 32-38, American Society of Civil Engineers. 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 69

70. Credits Kevin Rafferty, Engineering Consultant, Klamath Falls, OR. tripower@cvc.net (See heatspring.com for design course offerings) Steve Kavanaugh, Energy Information Services, www.geokiss.com, info@geokiss.com (See heatspring.com for design course offerings) Kirk Mescher, CM Engineering, Columbia, MO. 573-874-9455, kirk@cmeng.com, www.cmeng.com Lisa Meline, meline engineering, Sacramento, CA. 916-366-3458, lisa@meline.com, www.meline.com 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 70

71. Thank You! 10 February 2011 (c) Gary Phetteplace, GWA Research, LLC Slide 71