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Solar Thermal Photovoltaics
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Heat Pumps Heat Pumps work by removing heat from one place and putting it into another place. A fridge/freezer is the most common example. It removes heat from food and dumps it in your kitchen. You are heating your house by removing heat from frozen peas. However, pea heating is not the most suitable way to heat your house, not least because of the limited thermal capacity of peas. Heat pumps can be used to heat your home (or cool it) or heat hot water by collecting heat from (or dumping heat to) the outside air, ground, or water (for an overview of how heat pumps work, click here). With efficiency depending mainly on temperature differentials between the source and the destination of the heat, expect to get around three to four units of energy for every one put in. Eco-nomical offers 3 types of heat pump, ground source (often called GSHP) which use a fluid filled pipe buried underground to extract heat from the earth and move it into water for heating, air source water heaters which extract heat from the air, and pool heaters, which are optimised for lower output temperatures required by swimming pools. All of the below are 230V single phase with CE approval. Ground Source Heat Pumps
Air Source Water Heaters
Pool Heaters
How Heat Pumps (including fridges) Work Heat energy will always move from an area of high temperature to an area of low temperature. The bigger the temperature differential, the greater the flow. (It is important to be clear about the difference between heat and temperature. Heat is a measure of the quantity of one type of energy in something, temperature to how warm or cold it is. The same amount of heat energy will change the temperature of different substances by different amounts, 1kWh of heat will raise the temperature of 50 kg of steel more than that of 50kg of water. Because of this difference between heat and temperature, it is possible to remove heat energy from a cold thing and put it into a warmer thing. This is done using a convenient trick. A gas increases in temperature when it is compressed (which is why a bicycle pump gets warm when you use it) and gets colder when it is allowed to increase in volume (which is why ice sometimes forms on a gas bottle in use). A refrigeration fluid is used to transport heat from the cold input to the heat pump to the hot output. The fluid is expanded and evaporated to make it colder than what you are removing heat from, say, frozen peas at -5C. Heat energy then flows from the peas to the fluid in the refrigeration circuit, making the peas colder and the fluid warmer. The fluid is then compressed and condensed, which raises its temperature. Note that this temperature rise is not heat energy supplied during the act of compression, it is intrinsic to the compression process. Now the fluid is hotter than the water being heated, so heat flows from the refrigerant into the hot water.
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