Engr. Dr. Muhammad Nawaz Iqbal
A heat pump is a device that uses the refrigeration cycle to transfer thermal energy from the outside to heat a building (or a portion of a building). Many heat pumps can also be used to cool a building by rejecting heat outdoors after removing it from the enclosed area. Air conditioners are devices that only offer to cool. An example of refrigerant that is at room temperature gets compressed while the heating mode is on. The refrigerant heats up as a result. To an indoor unit, this thermal energy can be transferred. The refrigerant is squeezed and then let outside once more. It returns to the environment cooler than it was before it lost some of its thermal energy. Before the cycle restarts, it can now absorb the ambient energy from the ground or the air. Pumps, fans, and compressors all use electricity to operate.
Heat pumps with an air source, a ground source, a water source, or an exhaust air source are common varieties. Additionally, district heating systems employ them. A ground-source heat pump, also known as a geothermal heat pump in North America, extracts heat from the ground or groundwater below a depth of about 30 feet, where both are kept at a comparatively constant temperature throughout the year (9.1 m). A well-maintained ground-source heat pump would normally have a seasonal COP of about 3.0 as heat is taken from the ground and a COP of approximately 4.0 at the start of the heating season. Due to the necessity of drilling boreholes for the vertical placement of heat exchanger pipe or trenches for the horizontal placement of the piping carrying the heat exchange fluid, ground-source heat pumps are more expensive to install (water with a little antifreeze).
Since the Paleolithic era, geothermal heating has been utilized for space heating and bathing, respectively, utilizing water from hot springs. Geothermal power, the phrase used to describe the production of electricity from geothermal energy, has become more significant in recent years. Although only a very small portion of the earth’s geothermal energy is now being effectively utilized, frequently in regions close to tectonic plate borders, it is estimated that the earth’s geothermal energy resources are theoretically more than sufficient to meet humanity’s energy needs.
A ground heat exchanger in contact with the ground or groundwater is used by ground source heat pumps to extract or release heat. Accurate system design is essential to a successful system since poor design can lead to the system freezing after several years or to very inefficient system performance.
Heating performance is often reduced to dimensionless units as the coefficient of performance while cooling performance is typically stated in units of BTU/hr/watt. The BTU/hr/watt conversion factor is 3.41. The overall energy output is significantly more than the electrical input since a heat pump moves three to five times as much heat energy as it does electric energy. Since radiant electric heat is 100% efficient, this leads to net thermal efficiencies of more than 300%. Electric heaters and conventional combustion furnaces are never capable of achieving 100% efficiency. When compared to electric resistance heating and conventional air-conditioning equipment, ground-source heat pumps can cut energy usage – and the associated air pollution emissions – by up to 72%.
By utilizing inter-seasonal heat transfer and seasonal thermal energy storage, ground source heat pumps’ efficiency can be significantly increased. Thermal banks allow for the efficient retrieval of heat that was caught and stored over the summer. The importance of this advantage is greatest in commercial or district heating systems because heat storage efficiency rises with scale.
