Geothermal HVAC for Homes, Farms and Businesses(and schools) Alice Gitchell Richard Stockton College Please feel free to ask questions at any time!
What’s in the name? • “Geothermal energy” has historically referred to geysers and steam from deep in the earth • Not found in New Jersey • Better term is GeoExchange • Registered trademark of Geothermal Heat Pump Consortium • www.geoexchange.org
Why Stockton? • Long term interest in energy technology • Most of our heating and cooling is done by GeoExchange – 1650 T cooling capacity • “World’s largest” for many years • Used for research and training • Moving towards a very advanced system
The science behind GeoExchange • Constant temperature found a few feet below ground surface • Not making heat (by burning fuel) but moving it • Heat can be “moved” into a building to warm it, leaving the ground cooler • Heat can be discharged into the ground, leaving your building cooler and the ground a little warmer • So how to get to the right TEMPERATURE?
Science behind the heat pump • A heat pump runs on electricity, does work and “separates” hot from cold • Closed system with a gas inside • Compressing a gas heats it, expanding a gas cools it • Take advantage of either “side” of this closed system
Putting it together • Water to air heat transfer • Using electricity to move both air & water around • Two common configurations • Open versus closed loop
Open loop system • Suitable for house or small business • Pump well water through heat pump • Extract heat (winter) or discard heat (summer) • Discharge water to another well or other arrangement (landscaping) • Can “zone” using multiple small heat pumps
Components – water to air HVAC system • Well • Heat pump(s) • Thermostats or building management system • Ductwork • Discharge arrangement for water
Closed loop system • Put PVC piping into ground for heat exchange • “Borehole” is the most common configuration – 100 to 400 feet deep • Fill with water to circulate for heat exchange • System is isolated from groundwater • Can be scaled UP • Borehole field a LONG term investment
Advantages – open or closed system • Same equipment provides heating and cooling – less mechanical space required • Lower operating cost (percentage varies according to alternatives) - less pollution • Comfort factors - temperature never goes very high (so air is less dry) & air moves more slowly than forced hot air • Can heat and cool at same time (but not with the same heat pump)
Advantages (cont.) • Flexible configuration – inside building and also in terms of ground coupling • Quiet • No equipment exposed to weather or vandalism • Don’t need certified boiler operators • “Bragging rights” • Rebates – go to www.njssb.com click on equipment, currently $370 per ton
Disadvantages • Slightly higher initial cost for both equipment and design • Construction can be disruptive (for larger projects) • Unfamiliar to maintenance staff – but maintenance costs are lower in long run • Greatest benefits to facilities with high, consistent loads • Not economical for cooling only (in NJ)
Important pointers • Easier with new construction (but retrofits can work and should be included in comparisons) • Introduce into planning early – building will be slightly different • Check experience of architect and engineer • Need life cycle cost analysis and energy study • Geology counts – sand is good but rock is NOT bad • Ask for details if you are told “it won’t work”.
What’s next? • Hybrid systems – when AC and heat demand are out of balance • Pond or ocean systems • Standing column configurations • Aquifer thermal energy storage (ATES) seasonal storage common in Europe • Energy efficiency or carbon reduction credits – RECs in NJ now limited to renewable generation of electricity, but this could change
Stockton Projects Completed(research included) • Geothermal HVAC • Photovoltaics – 18 kW on Arts & Sciences Building, 2 kW on daycare • Lighting upgrades, motor replacement, etc. • Energy Alert – human behavior - harvest easy savings on high demand days • Fuel cell
Fuel cell • 200 kW electricity + 900,000 btu heat per hour • Consumes natural gas, so why do it? • Bypasses all transmission loss and reduces air pollution • “Transitional technology” in the public interest • Distributed generation less vulnerable to disruption • Non interruptible power – critical equipment and emergency response
Next at Stockton • Photovoltaics – large scale – flat roofs as a New Jersey resource • ATES (800 T cooling capacity) – feasibility study complete • Wind (1.5 MWatts) – careful evaluation of wildlife impacts necessary, technical advances important