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New dwellings at the design stage are in the ideal position for developers, builders and prospective owners to be able to take advantage of the latest technology and advances in RENEWABLE ENERGY SOURCES. There are a number of methods for harvesting energy without creating further huge amounts of carbon emissions, including Ground Source Heat Pumps, Air Source Heat Pumps and Solar Panels.
Ground source heat pumps, as the name would imply, harvest heat from the ground via buried pipes, buried below the lawn for example. Low-grade heat is collected from the ground by a liquid that is pumped through the pipes and is then returned to the heat pump via a suitable manifold. The liquid is compressed in the manifold and via a heat exchanger the heat is extracted for use to warm domestic hot water or the space heating system (radiators underfloor heating etc.) The underground pipe system, known as the loop, has to have its length calculated by taking into account the thermal heat available from the soil and then the length tailored to suite the heating requirement of the proposed dwelling. The ground source heat pump is run on electricity but will supply approximately four times the energy that is purchased to run the pump. E.g. 1kWH used supplies 4kWh of energy to the dwelling.
Air source heat pumps; again use a heat exchanger, together with a compressor and expansion valve to extract heat from the air. The supply harvested energy drops slightly to approximately 3kWh per 1kWh purchased, this reduction in efficiency is partially offset by there not being the outlay requirement that ground loops and bore holes call for. Surprisingly air source heat pumps can effectively extract heat from air that has a temperature well below zero. Noise is not an issue as the modern pumps currently available are quiet in operation.
Water source heat pumps are also available but this is not a renewable energy source that is necessarily easily available to everyone on a small domestic scale.
Solar panels need to be well positioned in order to provide approximately 50% of the domestic hot water to the dwelling, and the ideal position is not readily available for all dwellings. They are targeted at a relatively small percentage of the total energy the dwelling requires simply by the means of the current technology, thereby they do not have the potential to reduce the dwellings running costs that heat pumps have. One plus point is the significant reduction in CO2 emissions, which helps fulfil the obligation to use renewable energy, they also help to hit TER targets and achieve a better SAP rating.The use of HEAT PUMPS and SOLA PANELS can provide a welcome reduction in the TARGET EMISSIONS RATE (TER) and the DWELLING EMISSIONS RATE (DER) and help provide a satisfactory SAP rating, subjects which have been highlighted in previous articles.
Installing an underfloor heating system works well with the heat pump scenario, because the lower flow temperatures usually used with wet underfloor heating systems suit heat pumps, which work more efficiently at lower temperatures. Increase efficiency can be obtained by installing an ‘intelligent control system’ as opposed to a ‘standard control system’ at the outset of the heat pump/underfloor heating installation. A possible advantage of underfloor heating over a wet radiator system is simply, that the heat source is at floor level. Whereas with radiators the main convection point could be argued as being at waist height, or least well above knee level, leaving a possible cold spot of some 90cm above floor level and a hot spot a chest level. Therefore underfloor heating does have a viable argument that it is a more evenly distributed heating method starting with the lower flow temperature from the HEAT PUMP.