Make
the right choice for you and your environment
To find out how - Telephone: 01633 53 54 55 or Email (see contacts)
Micaul Solar are Grant Approved Accredited Installers under the BRE Microgeneration Certification Scheme MCS1074
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To find out how - Telephone: 01633 53 54 55 or Email (see contacts)
Micaul Solar are Grant Approved Accredited Installers under the BRE Microgeneration Certification Scheme MCS1074 |
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Micaul Solar First Company in Wales to be Microgeneration Accredited for Heat Pumps and Solar Thermal
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Ground, Air and Exhaust Air Heat Pumps
Heat pumps extract stored solar heat energy from the environment, ground, air or water and use that heat energy to generate heated water for heating and hot water. The heat pump then raises the temperature of the thermal energy extracted from the environment using operating energy to a level suitable for heating and DHW preparation.
Air to water heat pumps utilise the outside air as their energy source. Even at temperatures of up to -20 °C, heat pumps can still extract heating energy from the outside air.
Brine (or Ground) to water heat pumps utilise the ground via either ground heat collectors installed horizontally in the ground close to the surface or borehole heat exchangers placed vertically in the ground convey the heat to the surface. One advantage of a ground source heat pump is that is can be reversed to provide cooling in the summer. Reversible heat pumps are not usually eligible for grants.
Water to water heat pumps extract the heat from the ground water provided that it is available in adequate quality and volume and that approval of local water authorities has been granted.
Heat pumps are one of the most efficient heating and hot water systems available, as they utilise the solar heat stored in the surrounding air, in the ground or in ground water all year round and when used on a green tariff now being offered by most energy suppliers it could seen to supply central heating, hot water and electricity with zero carbon generation. Heat pump systems powered by standard tariff electricity can still produce 40% lower carbon emissions than gas fired and 55% less than oil fired installations. This is due to the ‘free energy’ the heat pump harvests from the environment and in many new build applications, heat pumps often provide the lowest running costs of any heating system.
In a well insulated building, heat pumps can provide 3 to 4 kilowatts of free energy for every 1 kilowatt of electricity used to power them. This ratio is known as the CoP (co-efficient of performance).
Heat pumps are at their most efficient when the water they produce is between 350C and 450C, far lower than would be practical for conventional radiator system typically needing water at 650C or higher, but ideal for warm water underfloor heating systems. Heat pumps are perfectly capable of producing water of a higher temperature but the efficiency rating or Coefficient of Performance (CoP) suffers, falling on average by 30% when delivering water at 500C, significantly compromising the economic and ecological benefits of the system. A CoP of five means that for every kilowatt of electricity put in, you get five kilowatts of energy out in the form of warm water.
In addition to the operational cost savings based on efficiencies, whilst a typical gas boiler should have annual safety checks by a Corgi registered heating engineer, heat pumps require no servicing, just a simple annual check of the system pressure that also helps to keep costs down.
Heat Pump Operating Principle
A heat pump heating system consists of the heat source system, the heat pump itself and a heat distribution and storage system.
Within the closed circuit of the heat pump, the refrigerant is responsible for transferring and transporting the heat. The actual heat gain from the environment takes place in the heat pump‘s evaporator 1 where a liquid refrigerant evaporates even in sub-zero temperatures when heat energy from the ground, air or water is passed across it, thereby storing the recovered energy. This change of state into a gas enables it to be compressed so this volume of the refrigerant is then drawn into a compressor (usually scroll type which is more efficient and quieter) where it is compressed 2. When the refrigerant is compressed, both the pressure and temperature of the refrigerant increases significantly. Within this closed circuit, the hot refrigerant flows on to the liquefier 3 – a heat exchanger in which the recovered heat is transferred to the heating system. This transfer of heat away from the refrigerant returns it to a liquid form. After the expansion valve 4 has caused a reduction in pressure and temperature, the refrigerant can once again absorb thermal energy from the environment, and the cycle begins once again.
Ground Source Heat Pump The most common method of extracting warmth from the ground is via collector pipes laid between 1 and 2 metres below the surface in a series of horizontal trenches.
The amount of land needed is approximately double the floor area of the property to be heated (150m² floor area requires approximately 300m2 land for the collector pipes), which could be a problem in densely populated urban areas.
Where land is at a premium, the collector pipes can be set into a vertical borehole; the earth gets warmer the deeper the borehole, so a correspondingly smaller amount of tube is required. However, the geology of the British Isles is notoriously varied in its makeup, meaning quotations for drilling boreholes may also vary significantly as contractors allow for the worst-case scenario. Any uncertainty can be overcome by commissioning a geotechnical survey giving detailed information on exact ground conditions.
Air Source Heat Pump
payback of a ground source heat pump with either trench or borehole is prohibitive, an air source heat pump may be the answer for heating and domestic hot water production. The unit itself works on a similar principle to the ground source heat pump but, as its name suggests, heat is extracted from passing air, requiring only an outside wall for installation and therefore, greatly reducing cost. Air source heat pumps are available as external or internal units with internal requiring ducting through an outside wall.
On average, the CoP is slightly less than for a ground source heat pump and units may require a supplementary source such as an immersion heater in severe weather conditions; a feature which is available on some units as standard.
Exhaust Air Heat Pump
To comply with current Part L of the building regulations, new homes and apartments in the UK are becoming increasingly well insulated. However, as building’s heat losses are reduced the ratio of lost heat due to uncontrolled ventilation increases and can now account for up to half of the building’s total heat loss. Part F of the regulations detail how to maintain the indoor air quality whilst avoiding wasted energy by designing either passive or controlled ventilation systems.
The Government’s Standard Assessment Procedure or ‘SAP’ now combines all aspects of energy efficiency to estimate a dwelling’s overall thermal performance in accordance with target energy use and reduced CO2 emissions. The use of controlled ventilation systems with heat recovery are favourably modelled, as are energy efficient types of heating systems including heat pumps.
Exhaust air heat pumps combines heat recovery and controlled ventilation into a compact, energy saving easy to install unit that controls the building’s ventilation and supplies all its heating and hot water. The exhaust air heat pump unit extracts air via ductwork connected to the warm areas of the building such as bathrooms, kitchens and utility rooms. Heat is removed from the air and transferred into the heat pump’s refrigerant circuit before being discharged to the outside.
Heat Pumps with Solar Thermal When heat pumps are used in conjunction with solar thermal systems, reductions in energy and carbon emissions are even greater. Although the operating costs of the heat pump are much less than other systems, solar thermal operating costs are almost negligible, usually only the cost of running a central heating size pump. Solar PV panels cans be used to power a DC pump and controller which will eliminate this cost.
To find out more, contact us on 01633 53 54 55
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Where
space is at even more of a premium and or the capital cost and therefore
