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Groton Local Energy Seminar Series # 7: Geothermal Energy to Heat Our New Home
09-Apr-08 By Lynwood Valentine Prest, P.E.
Presentation available at: http://grotonlocal.org/seminar.shtml Email: vprest@gmail.com
Val and Wendy Prest’s New Home in Groton, MA
• Heavily-insulated • Uses Geothermal Energy for its HVAC • Designed and decorated by the home owners • Builder: Shawn Boyd
– Boyd Building, LLC, Jaffrey, NH
TIGHTNESS & INSULATION
• Critical, no matter what fuels & HVAC equipment used • Insulate roof or attic - R=30 or better. Ours is R=50. • Insulate exterior walls, doors and windows - R=20 or better. Ours is about R=27. • Insulate around penetrations through roofs, attics & exterior walls with spray-on foam • Around doors, windows, pipes, ducts, electrical items, etc. • NO fireplace so no chimney and flue • Insulate sills atop foundations with spray-on urethane foam • Obtain lowest possible Energy Star Rating. They measure air leakage rates. • 0 to 100 w/ max at 85 to obtain Energy Star rating • Our house came in at 44
Other Factors
• VENTILATION
– Necessary because house is so tight against air leaks
• LIGHTING & APPLIANCES
– Energy Star to minimize electrical usage and heat generation
HVAC with Water Filters
Geothermal Water Piping
Ven Mar Energy Economizer
Geothermal Heating System
• Design: Water Energy Distributors, Inc., Hampstead, NH
– Uses their standing-well concept, a single water well that serves for both domestic use and geothermal energy.
• Furnished & installed by Bill Wenzel Heating and Air Conditioning, Inc., Merrimack, NH
– Tranquility system with a 40-gallon water storage tank and a separate 80-gallon water heater tank – Ven Mar energy recovery ventilator – 240V ultraviolet germicidal lamp – 2 separate zone-damper panels.
• Installation included:
– Ductwork and grilles – Insulation of exposed ductwork.
• COST, including installation: $33,985
Water Well
• Single well for both geothermal energy and domestic use
– Water line splits just inside the house. – One line goes to the heat exchanger of the geothermal system – Other line goes to the domestic water system
• Heat exchanger utilizes 35 gpm of water to obtain heat and cooling energy
– Incoming water stays about 49 to 50 degrees F all year
• Well, originally designed for a depth of 700 ft., stopped at 300 ft. upon encountering a 400 gpm aquifer • COST= $10,505
Economic Analysis - Installation • Cost for geothermal
– Cost of system: – Cost of well: – Total cost: $33,985 $10,505 $44,490
• Cost of conventional alternative:
– Cost of water well: – Cost of oil/gas-fired HVAC system: – Total cost: $4,500 $19,000 $23,500
• Additional cost for geothermal:
$20,990
Other Decision Factors
• Entire lot (less than 1/4 acre) is within the 100 foot buffer zone from the lake’s edge. • We did not want oil on the property, and it is expensive anyway. • We have little to no room for a large propane gas tank. • Coal and wood fired systems are labor intensive, messy on cleanup, and needs waste disposal. • Electrical resistance heating is too inefficient and expensive to operate.
Actual Operational Costs for Electricity
Month of Bill *8/2007 9/2007 10/2007 11/2007 12/2007 1/2008 2/2008 3/2008 TOTAL Amount of Bill 23.14 124.09 168.29 155.52 155.25 258.19 346.38 342.73 1,598.04
Supplier: Groton Electric Light
Comparison with Operational Cost for Conventional Oil Alternative
• Heating with oil:
– Estimated gals. per month: – Est’d $ per month at $3.46/gal: 253.3
• Non-heating electricity per mo.: • Total est’d for oil + electric per mo.: • Total est’d for oil + electric per yr.:
$876 $124 $1,000 $5,871
• Est’d total electric for geothermal/yr.: $2,278 • Net savings per year: $3,593 • Time to recover excess capital costs: 6 years
Bill’s