School facilities are being utilized more today than ever before. Whereas years ago students would attend classes and then the building would be locked down tight, now schools are used throughout the evenings and weekends. The costs to heat and cool a facility during these extra-use hours can affect a school's budget dramatically, prompting administrators to search for additional ways to cut energy consumption and reduce operating costs.
One option gaining attention is geothermal heating and cooling systems. Due to the relative stability of ground temperature, geothermal systems inherently are more efficient than heat pumps, which rely on outside air as a heat source or heat sink. Geothermal systems provide the highest efficiencies and lowest environmental impacts in summer cooling and winter heating, as well as water heating.
Understanding the system Before a school begins investigating geothermal heating and cooling as an option, it must understand the technology. Below the frost line, the temperature of the earth is relatively constant. These systems use geothermal heat pumps to take advantage of the constant temperature to provide efficient comfort conditioning.
Geothermal heating and cooling systems are composed of three primary parts: *An earth connection for transferring heat between the earth and a fluid contained in a series of pipes.
*A geothermal heat pump to move heat between the fluid in the earth and a fluid contained in a series of pipes.
*A distribution system for delivering heating or cooling to the building. Many systems also have additional equipment to supplement the building's water heater or a full-demand water heater to meet all of the building's hot-wate r needs.
In most school installations, one geothermal heat pump is used for one or two classrooms. The heat pumps may be in the classroom as consoles, in closets or above hallway ceilings. Larger heat pumps are used for areas such as cafeterias and gymnasiums, and others may be used to provide hot water for kitchens and locker rooms.
All of the heat pumps then are attached to the same earth connection by a loop of pipe inside the building. The earth connection is either a series of buried pipes (closed loop) or water wells (open loop), often buried beneath parking lots or playing fields.
Closed-loop systems circulate water or an environmentally safe antifreeze through buried plastic pipes. The fluid absorbs heat from the ground during the winter and transfers it to the heat pumps inside the school. In the summer, the process is reversed with heat from the building returning to the ground. Open-loop systems operate on the same principle and can be installed where an adequate supply of water is available.
Exploring the benefits There are many benefits to utilizing geothermal systems in schools, including: *Reduced energy costs. Electric utilities and energy service companies (ESCOs) often find that these systems provide low maintenance costs, and due to their flatter load profile, usually cost less to serve than other electric options. This results in reduced costs for the end user. Another benefit is that the increased efficiency reduces the need for additional electrical capacity, transmission and distribution grids.
*Low operating costs. Geothermal systems do not require an outdoor unit, which allows for noise reduction and improved aesthetics. Also, heating-system lifetimes are enhanced due to the system's simplicity and lack of exposure to weather elements. Comfort often is improved by higher discharge temperatures and better humidity control.
*Low maintenance costs. Routine maintenance is primarily replacement of air filters, which can be done by in-house staff. The heat pumps are modular and interchangeable; therefore, there is no need to stock parts for multiple boilers and chillers.
*Less harm to the environment. Geothermal systems limit CO2 emissions more than gas, electric, oil or propane. Emissions that are released occur at the power plant where they are monitored and controlled.
*Increased comfort levels. Geothermal systems use many relatively small heat pumps; therefore, each teacher can have control of the individual classroom comfort level.
*Increased design flexibility. These systems eliminate the need for outdoor or rooftop equipment. Therefore, schools are not limited to flat roofs. Also, there are no roof penetrations for piping or a need for service people on the roof, reducing roof maintenance.
*Increased safety. Some combustion-based systems present an explosion hazard if storage or delivery of the fuel is not controlled carefully. Incorrectly installed systems, chimneys that become blocked, or downdrafting can cause carbon monoxide to remain inside the buildings. Geothermal systems have no combustion, and thus do not produce indoor pollutants. Also, since the earth connection is buried, there is no chance of accidents from students climbing on equipment.
Banking the savings While installation costs sometimes are higher due to the additional cost of the earth connection, expenses are saved in other ways. For example, geothermal systems allow a school to forgo a boiler room, which can decrease building size by 3 to 5 percent. Also, since large ductwork is not used to distribute energy throughout the building, floor-to-roof heights can be reduced.
In almost all cases, operating costs associated with geothermal systems are lower than those of other heating and cooling systems. The actual savings, which can amount to 40 percent or more on an annual basis, will depend on the type of system being replaced and the characteristics of the building and location--utility rates, availability of natural gas, weather, hydrology and geology. Another potential cost savings is that the energy from the s ystem's refrigerant cycle can be designed to preheat the building's hot water supply, heat a swimming pool or be used for other purposes.