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»WHAT IS GROUND SOURCE HEATING/COOLING? HOW DOES IT WORK?
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The refrigerator enters to the compressor as a vapor. Than vapor compressed to the high pressure level. The refrigerator which is very hot at the compressor output, will get cold and concentrated at condenser while giving out heat. Refrigerator will enter to the expansion valve after condenser. Than its pressure and temperature will decrease. After expansion valve, the refrigerator will be vapor while taking heat from the cooling area at evaporator. The cycle will be completed with refrigerators entering to the compressor after the evaporation.
As an example, the fridge at houses works based on cooling cycle same as heat pumps. The freezing part is evaporator and the pipes behind the fridge are condenser. The heat pumps are various as shown in the example. Only, the cooling area and the heating area are changing.
Source
Load
Air
Air: Air Ducts
Water: Fan coil, floor
heating, radiator... Water (sea,lake,river,...)
Water (Underground)
Water (Boiler / Tower)
Soil
Solar Energy
Geothermal Energy
Waste Heat Source
As shown on the table above, the heat pumps use different sources and they are called with different names as the type of its source. As an example, if heat pump uses air as a source, it is called air source heat pump. If it uses water as a source, it is called water source heat pump. The source type effects to the total system efficiency and the operating costs directly.
Air is a type of source which can be found easily but the temperature of it will change widely from winter to the summer. It is wanted from source to be cold while cooling or to be hot while heating. But the air is hotter at summer and cold at winter. So cooling or heating will be the less efficient while using air as a source.
The water used differently as a source. The types will be seas, lakes and rivers also the underground water. Besides the boiler/tower system called hybrid system is a water source.
Ground source heat pumps are using soil as a source. Water is circulating in the pipes which are buried under the soil. The heat energy under the soil is transferred to the heating area with heat pump. The cooling cycle is used while the heat transferred to the place from the source. The ground source temperature is changing a little bit from winter to the summer. The soil temperature change depends on the country, city and the soil type. A large soil area is necessary for using ground source heat pump.
Besides the general types of sources explained above, there are different source types, too. Low temperature geothermal water, hot or cold waste water, stored hot water with solar energy are the different types of heat pump sources.
WHAT IS GROUND SOURCE HEATING/COOLING? HOW DOES IT WORK?
The outside air temperature changes depend on the seasons. The underground soil temperature is constant nearly 1,5m-2m under the soil. The ground source heat pump system which occurs from an indoor unit and buried pipes under the soil, use the constant underground temperature to get energy efficiently. At winter, the water circulating in the buried pipes, transfers the stored heat under the soil to the indoor. The indoor unit is increased the temperature of water and give it in to the heating areas. At summer, the system works reversibly. It takes the heat from cooling area and transfers it to the underground which is cooler than the cooling area. As mentioned there is no fuel burning, only the stored heat transferring one place to another. Because of this reason the ground source heat pump system is 25%efficient from natural gas and 65% efficient from LPG.
There are two parts in the GSHP. The load side is the heating or cooling area and the source side which gives or takes the heat from underground. The load side can be air or water which is cold or hot. The conditioned air or water works with the load side building system like air handling or fan coils. The important part is the source side and it has different types. These types divided into two basic parts like closed or open systems. The basic parts divided into various types too.
The closed heat exchangers occur with closed loop and buried underground polyethylene pipes. The closed loop pipes are connected to the heat pump unit and the natural friendly antifreeze-water solution circulating in the pipes. In the closed pipes, the water only circulates, it doesn’t expend the water as in the open loop systems.
Closed loops generally occur near the building and are buried horizontally. If there is not enough space, the pipes can be buried vertically. The empty soil space near your building is enough for having GSHP system.
The trenches for using to bury the pipes are generally 2-3m dept. For a good isolated 600m2 house, 45kW system will be enough with nearly 1700-2500m pipe depends on the soil type.
One of the horizontal pipe burial type is slinky installation. At this type the polyethylene pipes can be buried to smaller trenches. So slinky type horizontal installation need less soil space from one or two pipe horizontal system.
The other horizontal pipe burial type is vertical installation. The heat exchanger pipes buried to the vertical bore holes. The dual pipes with a U-bolt at the end of the pipe buried to the borehole nearly 60m for 3,5Kw. The difference between this type drilling and water drilling is, the bore hole diameter is small and no need jacket in the hole.
A well, lake, river, sea or waste water at fabrics may be used as a open source. If the water content is harmful for the heat pump unit, plate heat exchanger has to be used between the source side and the unit. The water’s energy is taken and given back to another place without any damage to the nature.
At the buildings like shopping malls the heating or cooling load is very big. So the necessary soil area has to be very large for ground source heat pump system.
In the system of water source heat pump, all of the unit has a fan powered exchanger at load side, a water to water exchanger at load side, compressor and control panel. At the load side while the unit cools the air the source side water gets hot. The opposite of it occurs too. While the unit heats the air the source side water gets cool.
