Heat pumps 2 Specification


>


ground-source, so air-source shouldn’t be discounted as a technology. ‘With capacities of up to 60kW available, giving


COPs of up to 4.4 (based on air temperature of 7C, and flow temperature of 35C), these units can meet large commercial needs as efficiently as ground- source models. They have fewer space constraints and lower installation costs and have been used in a wide variety of installations such as schools and communal systems. They are also effective when used to pre-heat domestic hot water, helping to increase overall system efficiencies.’ Davis is seeing a lot of interest in air-source heat


pumps from specifiers, especially for refurbishment projects: ‘They can be retrofitted far more easily than a ground-source system. The one barrier to [greater uptake of ASHPs] is probably planning. For example, the London Toolkit [offering advice on renewables] specifically prescribes against air-source heat pumps. That is just ignorance and lack of understanding. There is a lot of work for the industry to do to overcome [these sorts of] misconceptions.’


For those companies that are making and promoting


heat pumps, this technology is viewed as a potentially superior solution to other more traditional sources, such as gas boilers or oil heating. Manufacturers are clearly keen to be able to offer specifiers a range of solutions, however, and the payback on investment


Air-source heat pumps can be retrofitted more easily than ground- source ones – Chris Davis


afforded by heat pumps is likely to be boosted with the introduction of the RHI. Even without the RHI, heat pumps are being taken up by social housing providers as they refurbish domestic properties, because the technology can mean lower fuel bills for tenants (see box). This may explain why heating product providers increasingly see heat pumps as the future – and this is one bandwagon that they increasingly seem to prefer to be on, rather than risk being left behind. l


Case study Heat pumps come to fore as homes go off the gas grid


Cottsway housing association in west Oxfordshire, UK, chose to install an air- source heat pump on a three-bedroomed mid-terrace house in August 2008. The 1960s traditional brick building had already undergone a series of insulation works a few years earlier – including filling the 50mm cavity wall with rock, placing 300mm insulation in the loft, and replacing the windows and doors with double glazing and new front and rear doors. Next, the old heating systems – storage


heaters in all rooms, and a storage convector and solid fuel open fire in the lounge – were ripped out and replaced with an air-source heat pump. The property was off the gas grid. Cottsway decided against simply


connecting the house to the gas grid partly because of cost; a gas connection to the grid can cost anything from £750 to £3,500. Add on the costs of a gas boiler, tanks, pumps, pipes and radiators and he says that could increase by another £4,000. In contrast, the air-source heat pump


and its set-up, with tank, radiators and so on, costs on average £5,300 – but, with up to £3,300 funding from the Low Carbon Building programme, the heat pump was an attractive option. During the year-long trial, the heat pump


used 4,156kwh of electricity to supply all the heating and hot water, at a cost of £384,


The Pearce family say their heating and hot water bills have been cut by half after an air-source heat pump replaced electric storage heating


with the total cost of electricity consumed being £810. This is down from a total electrical consumption of 15,563kwh a year – at a cost of £1,137 in bills. Subsequently, the household’s CO2 emissions have been reduced from 9 tonnes a year to just 3.2 tonnes. Energy generation at the property is now


also being supplemented with solar thermal energy, which could generate up to 80 per


cent of the tenants’ hot water in the height of summer, according to Cottsway. The housing association also hopes that


the heat pump will generate more savings when the Renewable Heat Incentive scheme takes effect. The full version of this article can be found in the CIBSE Journal Social Housing Supplement, published with the June 2010 Journal. Visit www.cibsejournal.com


44


CIBSE Journal August 2010


www.cibsejournal.com


Cottsway HA


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68