Ground Source Heat Pump (GHP) Technologies in Residential Construction

Josh White

Impetus

• 41% of U.S. energy consumption in 2014 came from residential heating and cooling.

(U.S. Energy Information Administration, April 2015)

Energy Production

Retrieved from http://www.eia.gov

“Geothermal” Pumps

• Low Grade-Refers to extraction of energy as a result of stored solar radiation.

• High Grade-Refers to energy that comes from pressurized water in the Earth’s crust.

(2014) Geothermal Heating and Cooling Systems. International School of Well Drilling

Regional Temperature Variation (Annually)

http://www.physicalgeography.net/fundamentals/7l.html

-Relatively large daily and annual surface temperature variation based on incident solar radiation at a given latitude

45o N

Ground Temperature Variation (by Latitude and Depth)

Mean annual earth temperature observations at individual stations, superimposed on well-water temperature contours.

http://www.builditsolar.com/Projects/Cooling/EarthTemperatures.htm

Le Feuvre 2007

Anatomy of a GHP

Source: Chewonki.org

Vapor Compression Cycle

Reverse Rankine or Refrigeration Cycle

Source: Chewonki.org

ffden-2.phys.uaf.edu/212_spring2007.web.dir

Drives phase change of refrigerant, liquid to gas and back.

Coefficient of Performance

COP = Q/W

Expresses the efficiency of a heat pump as the ratio of the heat extracted from the pump to the work done by the compressor.

Ex. ΔT= (T1 – T2) = 31oC Where T2 = 6oC or 279K

COP = T1 / ΔT = 10! (Ideal case)

Actual values on the order of 3-5

Direct vs. Indirect Systems

• Direct systems pump working fluid into boreholes and allow heat transfer between sink and fluid directly

• Indirect systems utilize a circulating fluid (separate from the working fluid) is used as an intermediary for heat transfer.

Case Study #1: Z-Homes

2011 in Issaquah, WA

•10 Units

•“Zero net energy use”

•Zero Carbon Emissions

•Use of photovoltaics and GHP

Liljequist B. 2011

Z-Home GHP

•15- 220ft Boreholes

•1” Diameter U-shaped pipes grouted and fused to a network just below the surface

•Pipes constructed of high density polyethylene (same as for natural gas)

•Pumping fluid is a water/ethanol mixture

Liljequist B. 2011

PipingOne of the polyethylene pipes

Difficult ground conditions meant 10 weeks of drilling!

Subsurface networks of transfer pipes

Liljequist B. 2011

GHP Well field Rig

Liljequist B. 2011

Heat Pump

• Product of WaterfurnaceTM

• 1.5 Tons

• COP Range 3.1 to 4.0

• Cost: $3000-$8000

Efficiency

Waterfurnace Product Manual

Working Fluid

• R-410-A Refrigerant

• Alternative to Freon and other CFC’s

• Requires low boiling point

Case Study #2- Direct Expansion Heating (China)

Anatomy of a GHP

Source: Chewonki.org

Comparison to Coupled GHP

Drawbacks• Requires more working fluid• More prone to leaks• Copper pipe vs polyethylene

Benefits• Less well piping• Less expensive long term

Cost Comparison

Assumed for 90 day cooling and 140 day heating

Conclusions

• Expense limits use in residential construction to commercial builders/ higher budget projects

• Feasible solely based on size, performance, and annual operating costs

• Subsidies can help expedite proliferation of the product

ReferencesAndrews, J. & Jelley, N. (2013). Energy Science. Oxford University Press. Oxford, UK.

(Used as Background Only) Brown, J. (2015). A Crash Course in Geothermal Heat Pumps. Nordic Heating and Cooling.

Retrieved from http://www.nordicghp.com on 5/1/2015. Caird, S. & Roy, R. (2010). Adoption and Use of Household Microgeneration Heat Technologies. Low Carbon Economy, vol. 1, pp. 61-70. Gao, Y. et al. (2013). Comprehensive Benefit Analysis of Direct Expansion Ground Source Heat Pump System. Energy and Power Engineering, vol. 5, pp. 76-81. Liljequist, B. (2011). A Zero Energy Community. Dwell, September 14. Retrieved from: www.dwell.com/renovation/article/zero-energy-community-part-1 on 4/10/2015. Smith, M. (1974). Geothermal Power. AIP Conference Proceedings, 19, 401.

Uncredited (2014) Geothermal Heating and Cooling Systems. International School of Well Drilling; Lakeland, Fl.

Direct Correspondence with City of Issaquah and RH2 Engineering