Heat pumps are used for space heating and cooling, as well as water heating. They operate on the fact that the earth beneath the surface remains at a constant temperature throughout the year, and that the ground acts as a heat source in winter and a heat sink in summer. They can be used in both residential and commercial or institutional buildings. Other heat pump types are available such as air and water source. These operate on the same principle indoors but the method of collecting heat is different for each type.
How it works.
The earth’s surface acts as a huge solar collector, absorbing radiation from the sun. In this country the ground maintains a constant temperature between 11C and 13C, several meters below the surface. Heat pumps take advantage of this by transferring the heat stored in the earth or in ground water to buildings in winter and the opposite in summer for cooling. Through compression, heat pumps can act as a multiplier, taking in heat at low temperature and release it at a higher temperature so that it may be used to heat water or air. A heat pump looks similar and can perform the same functions as a conventional gas or oil boiler, i.e. space heating and sanitary hot water production. For every unit of electricity used to operate the heat pump, up to four, five or even six units of heat are generated. Therefore for every unit of electricity used to pump the heat, 3-6 units of heat are produced. Ground source heat pumps use a 'closed loop' system of water/anti-freeze or direct expansion to collect the soil heat. Air/water heat pumps collect heat from the outside air. Generally, air temperatures are moderate in Ireland but due to natural frosting of the air heat exchanger during heat collection and our moist climate, it is necessary that these pumps use a proportion of energy produced to defrost. This leads to a decrease in performance which increases as the air temperature decreases which is offset by a low installation cost. Water/water heat pumps use water from a well/river directly as a heat source. These are generally 'open loop' collectors, i.e. the water is passed through and discarded, unlike the 'closed loop systems'.
Installation in the Home
The system has three main components: a series of pipes in the ground, a heat pump and a heat distribution system. Lengths of plastic pipes are buried in the ground, either in a borehole or a horizontal trench near the building to be heated or cooled. Fluid, normally water with anti-freeze, absorbs or emits heat to the soil, depending on whether the ambient air is colder or warmer than the soil. In winter, the heat pump removes the heat from the fluid, upgrades it to a higher temperature for use in the building, typically in under-floor heating. A distribution system is needed to transfer the heat extracted from the ground by the heat pump.The heat is often in the form of hot water and is distributed around the dwelling by low temperature radiators or an underfloor heating system.The geothermal pump systems reach fairly high Coefficient of performance (COP), 3-6, on the coldest of winter nights, compared to 2-4 for air-source heat pumps on cool days. Ground source heat pumps (GSHPs) are among the most energy efficient technologies for providing space heating and water heating. The setup costs are higher than for conventional systems, but the difference is usually returned in energy savings in 3 to 10 years. System life is estimated at 20 years for inside components and 50+ years for the ground loop.
The optimum heat supply to a building is when the demand is met and nothing is in excess. An intelligent electronic controller for weather compensation in the heating system can pro-actively adjust the supply of heat to keep it at exactly that point by detecting changes in the weather conditions outside. In reverse, a heating system without a weather compensator will only react on the current indoor temperature, and thus be prone to be in delay when changes occur outside. This negatively affects both user comfort and energy efficiency.
How does it work?
The weather compensator gets its signal from an outdoor temperature sensor placed on the shadow side of the building. The sensor registers the actual temperature and the electronic controller adjusts, if necessary, the heat supply (flow temperature) to reflect the new conditions. The controller will also adjust the heat supply to the radiators and ensure that room temperatures are kept constant. The user will thereby not even notice that the weather has changed outside and experience the same temperature and comfort at all times.
10 – 40 % energy savings with electronic weather compensation
By letting the flow temperature in the heating system reflect outside temperatures, the user will not only experience increased comfort, but also smaller heat bills. In a recently published COWI report, the advantages of weather compensation are sound and clear:
In one-family houses, the expected energy saving is on average 10% and in some cases up to 40%! Especially in one-family houses with a large consumption of heat, a weather compensator is an investment, which quickly pays back.
Electronic controllers featuring weather compensation are a natural part of modern heating systems and will optimize comfort while saving energy. Whether the sun is shining or the snow is falling,weather compensated controllers will ensure a heating system which operates optimally and keeps the user's surroundings comfortable