Hot water Measured peak demand periods
Theoretical design day (Average day + uprated peak demand
Measured average daily demand & theoretical design day with uprated peak demand & data overlay
peak. Despite this, carbon savings and costs are no longer aligned. If we take the 2022 average occupancy
rate for UK care homes as 23.5, the yearly running costs resulting from a change from gas to direct electric would increase from £1,019 to £3,019. Even with an ASHP operating at optimum efficiency (for 35 per cent recorded reduction in energy), costs would be £2,862. This is close to three times that of gas alone, so it is important to consider the nominal value of the carbon reduction when planning a refurbishment from gas to electricity. However, we can still take advantage of solar thermal, which can be employed to offset energy use in gas-fired systems as well as offsetting costs in electric/ASHP applications.
Harnessing the power of the sun As a high-temperature renewable source of hot water, solar thermal lends itself
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to working in conjunction with not only conventional gas heating but also other renewable technologies, including air source heat pumps which can be used to provide pre-heat to solar thermal. This enables a variety of hybrid applications to be considered to meet the varied demands of care home buildings.
Solar thermal systems are ideal for care homes that use and rely on large amounts of hot water, but it is important to understand that a solar thermal system will not fully replace your existing water heating system and will not provide space heating. All areas of the UK are suitable for solar energy technology; however, solar insolation, the energy generated from sunlight within collectors, will decrease as the sun’s inclination falls in the winter months and this is affected by how northerly located a building is in the UK, as well as cloud cover. Solar thermal systems are obviously most productive in
the summer months, when there is most sunlight, resulting in the additional need for either non-renewable energy sources or heat pumps which will still generate usable energy all year round, even if ambient outside temperatures drop to -20°C during the winter months.
Shading from neighbouring buildings
or tall trees, for example, can also greatly reduce a solar system’s output, in which case a commercial air source heat pump would be a preferred alternative to produce low-carbon heat energy. The actual percentage of your water heating demand covered by solar thermal will depend on your site and energy consumption habits (though this figure is typically around 30 per cent for commercial sites). A south-facing and unobstructed roof with an inclination of 30° from the horizontal is optimal, though by no means essential, as solar collectors can be installed in a variety of ways – built on the roof, built
www.thecarehomeenvironment.com April 2023
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