Geothermal Defining Geothermal Energy Dictionary definition Relating to the internal heat of the earth The Earth acts as a giant solar collector, absorbing approximately 50% of the energy emitted by the Sun. Air temperatures may fluctuate as much as 50 F above and below the annual average. However, only a few feet below the surface, the changes in earth temperatures are much less severe. Heat Pumps Heat pumps move energy from one location to another, instead of creating heat by burning fossil fuels, such as a gas furnace does. -- (like your refrigerator). Geothermal Heat Pumps use the earth or well water to provide heating, cooling and hot water for your home. A geothermal heat pump moves energy to/from the ground, eliminating the outdoor equipment associated with ordinary heat pumps or air conditioners. The Basic Ground Source Heat Pump System The earth loop is placed in the ground either horizontally or vertically, or it can be placed in a pond. Water and anti-freeze is circulated through the pipe, transporting heat to the heat pump during the heating mode and away from the heat pump during the cooling mode. The heat transfer takes place inside the heat pump in a water- to-refrigerant heat exchanger. Energy Source During the heating season, the earth serves as a heat source. (HE - Heat of extraction) During the cooling season, the earth serves as a heat sink. (HR - Heat of rejection) Heat Pump Operation Geothermal heat pumps consist of four circuits: Distribution circuit The system that distributes the conditioned air or water solution throughout the home or building and returns it to the unit. Refrigerant circuit A sealed and pressurized circuit of refrigerant including compressor, expansion valve, water-to-refrigerant heat exchanger(s), air coil, reversing valve. The refrigerant is either R-22 or R-410A. Heat Pump Operation Geothermal heat pumps consist of four circuits: Ground loop circuit The piping system buried in the ground has fluid that is circulated by pumps to and from the geothermal unit. Hot water circuit Domestic water can be heated in a geothermal unit with a device called a desuperheater. A piping connection is made from the geothermal unit to the water heater. Heat Pump Operation Each of these circuits is closed and sealed from the others there is no direct mixing. However, heat energy does transfer from the refrigeration circuit to the other three circuits. The refrigerant flow will change direction when the unit changes modes (heating or cooling). Heat Pump Operation The Four Circuits in a Geothermal Heat Pump Distribution Circuit Earth Loop Circuit Refrigeration Circuit Hot Water Circuit = Flow of Energy (Heat) Heating Mode Operation Cooling Mode Operation The Basic Refrigeration Cycle Compressor CondenserEvaporator TXV High Pressure Vapor State High Pressure Liquid State Low Pressure Liquid State Low Pressure Vapor State The Refrigeration Cycle Heating Mode Operation The Refrigeration Cycle Cooling Mode Operation Free Energy Geothermal Heat Pumps use only a small amount of energy to capture a large amount of FREE energy from the earth. Equipment Performance Ratings ARI has designated the efficiency ratings for water-to-air heat pumps as: Energy Efficiency Ratio (EER) EER = BTU output divided by power watt input For cooling operation under steady state test conditions Coefficient of Performance (COP) COP = BTU output divided by BTU input For heating operation under steady state test conditions Loop Types Closed Loop (w/ antifreeze) Horizontal Vertical Pond Open Loop Well Water Positive & Negatives Open well systems + can be cheaper initial install cost + constant supply of consistent btuhs -requires substantial water over life of system -if well fails no heating or cooling -not allowed in some local areas Well Water (Open Loop) Uses existing well Requires 1.5 gpm/ton Open Loop Systems Key Considerations Adequate water supply (5-9 gpm in addition to household requirements) Good quality water (low mineral content) Adequate discharge location (drainage ditch, field tile, pond, etc.) Positive & Negatives Closed loop systems + low maintenance + typical one time install, long warranty on pipe - higher up front installation cost - variable supply of btuhs so sizing is critical -requires dedicated space for wells or trenches Horizontal Loop 2- Pipe Horizontal Typically 3-4 trenches, 250 feet long each 4- Pipe Horizontal Typically 2 trenches, 180 feet long each 6- Pipe Horizontal Typically 1 or 2 trenches, 120 feet long each Horizontal 4 & 6 Pipe Loops Typically 3 or 4 trenches, feet long each 10 ft feet 2-3 feet Slinky Vertical Loop Typically 3 to 5 bore holes, 130 feet deep each Vertical bore without backfill Vertical Loop/Grouted Bentonite Grout backfill Geothermal pipe Vertical Loop Drilling Use drilling rig like ones used for water well drilling. Pond Loop Minimum acre, 8 ft. deep