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

Stockton campus

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

Closed loop

Vertical Piping

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