generating tiles with solar thermal tiles to heat water required in homes. A Nu-Lok roof on St. Silas Church in Islington, London is reportedly the first Grade 2 listed building in the UK with a south facing PV roof. (4)


and electricity in a simultaneous process at the point of use, can enable costs savings to be made and carbon emissions reduced through economies of scale from centrally generated grid electricity. It is a technology which can be used for building heating, industrial heating, and district heating.


CHP plant converts around 30 per cent of energy in fuel to electricity and another


55 per cent into useable heat, to realise an overall energy efficiency of 85 per cent, which compares favourably with the overall energy efficiency of centralised grid power and heat generation and transmission at around 55 per cent. (7)


This had led to an increased inclusion of district heating systems in new property development and regeneration initiatives, although to realise comparatively high heat efficiencies the buildings supplied by district heating need to have a continuous heat load. (8)


CHP may not offer such an efficient renewable energy source solution though for new housing schemes involving phased development as the continuous power supply requirements of CHP might not be met. A better solution for phased developments, or for applications in rural areas which are not connected to an urban mans supply system, can be mini CHP plants (up to 50kw electrical capacity) or micro CHP plants (up to 2kw electrical capacity) which can supply single dwellings. In using waste heat for space and water heating, micro CHP plants can also supply electricity for lighting and household appliances, with any excess being sold back to the grid where there is an agreement in place to do so. (9)


Biomass. Biomass is an organic substance derived from non- fossil animal or vegetable matter, which for vegetable matter is carbon neutral in that the carbon absorbed when the biomass (e.g. timber) is grown is effectively equivalent to the carbon released in the burning process. (10)


Seamless Integration – A Nu-Lok Roof on St. Silas Church in Islington, London


Solar Thermal. Unlike solar photovoltaics, which produce energy from daylight, solar thermal technology generates energy through the absorption of direct sunlight to heat collectors, with the systems being easily installed in existing roofs or new construction at comparatively modest cost. Whereas PV derived energy has to be used at the time of its generation, solar thermal technology can be used anywhere that hot water can be stored, which may require hot water cylinders to be replaced with retrofit installations. The stored hot water can then be used in overcast conditions or at night. (5)


Integrated boiler and solar thermal equipment systems should avoid energy waste from boilers firing to fulfil morning domestic hot water needs when cylinders are already full of hot water from the morning sun. (6)


Combined Heat and Power. Combined Heat and Power (CHP), involving the conversion of a single fuel into both heat


16


Notwithstanding early teething problems, a new generation of comparatively clean and user-friendly biomass boilers, such as the Hoval BioLyt boiler, have a pellet feeding system from the storage area to the boiler, automated controls to automatically switch off when heat is not required and re- ignite when heat demand is restored, and include self-cleaning surfaces to avoid soot deposits and automatic extraction of


ash from combustion. (11)


Biomass is typically available in wood logs, pellets or woodchip, which offer a carbon neutral fuel source alternative to gas and oil, but can involve energy source costs risks associated with reliability of supply and possibilities of transportation costs increases. Being bulky in nature, the availability of space for storage of the fuel, and the development costs of providing storage in new developments, will add to overall construction costs for developers.


Heat Pumps. Heat pumps work by extracting ‘free heat’ from air, ground, water, or recovered heat sources and transporting the heat to where it can be used for space or water heating. Having had a poor reputation for limited effectiveness in heat generation, modern pumps can now cope with providing space and water heating to flow temperatures of up to 75 degrees centigrade. (12)


deliver the highest efficiencies, although benefits of air source pumps are that they avoid the space requirements and costs


THE TERRIER - Autumn 2011


Ground source heat pumps can


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