thermal energy is the kind of heating that is a heat pump.
thermal energy is the kind of heating that is a heat pump.
what kind of heating is a heat pump?
thermal energy
heat pumps use work to move heat from one place to another, and can be used for both heating and air conditioning. though capital intensive, heat pumps are economical to run and can be powered by renewable electricity. two common types of heat pump are air-source heat pumps (ashp) and ground-source heat pumps (gshp), depending on whether heat is transferred from the air or from the ground. air source heat pumps are not effective when the outside air temperature is lower than about -15 °c, while ground-source heat pumps are not affected. the efficiency of a heat pump is measured by the coefficient of performance (cop): for every unit of electricity used to pump the heat, an air source heat pump generates 2.5 to 3 units of heat (i.e. it has a cop of 2.5 to 3), whereas a gshp generates 3 to 3.5 units of heat. based on current fuel prices for the united kingdom, assuming a cop of 3-4, a gshp is sometimes a cheaper form of space heating than electric, oil, and solid fuel heating. heat pumps can be linked to an interseasonal thermal energy storage (hot or cold), doubling the cop from 4 to 8 by extracting heat from warmer ground.
renewable heat
the heat pump is a refrigeration based appliance which reverses refrigerant flow between the indoor and outdoor coils. this is done by energizing a reversing valve (also known as a "4-way" or "change-over" valve). during cooling, the indoor coil is an evaporator removing heat from the indoor air and transferring it to the outdoor coil where it is rejected to the outdoor air. during heating, the outdoor coil becomes the evaporator and heat is removed from the outdoor air and transferred to the indoor air through the indoor coil. the reversing valve, controlled by the thermostat, causes the change-over from heat to cool. residential heat pump thermostats generally have an "o" terminal to energize the reversing valve in cooling. some residential and many commercial heat pump thermostats use a "b" terminal to energize the reversing valve in heating. the heating capacity of a heat pump decreases as outdoor temperatures fall. at some outdoor temperature (called the balance point) the ability of the refrigeration system to transfer heat into the building falls below the heating needs of the building. a typical heat pump is fitted with electric heating elements to supplement the refrigeration heat when the outdoor temperature is below this balance point. operation of the supplemental heat is controlled by a second stage heating contact in the heat pump thermostat. during heating, the outdoor coil is operating at a temperature below the outdoor temperature and condensation on the coil may take place. this condensation may then freeze onto the coil, reducing its heat transfer capacity. heat pumps, therefore, have a provision for occasional defrost of the outdoor coil. this is done by reversing the cycle to the cooling mode, shutting off the outdoor fan, and energizing the electric heating elements. the electric heat in defrost mode is needed to keep the system from blowing cold air inside the building. the elements are then used in the "reheat" function. although the thermostat may indicate the system is in defrost and electric heat is activated, the defrost function is not controlled by the thermostat. since the heat pump has electric heat elements for supplemental and reheats, the heat pump thermostat provides for use of the electric heat elements should the refrigeration system fail. this function is normally activated by an "e" terminal on the thermostat. when in emergency heat, the thermostat makes no attempt to operate the compressor or outdoor fan.
thermostat