An Introduction to the Hybrid Solar Solution a report by Nigel Wakefield Commercial Director, Newform Energy Ltd
The Hybrid Solar Solution
This British-designed and -built solution is the first in the world to combine three different renewable energy technologies into a single efficient and reliable system. It can provide all of the annual central heating and hot water requirements of well-insulated homes and generate more than enough electricity to do so carbon-neutrally.
In order to explain how the hybrid solar solution generates efficiencies in both financial and environmental terms, it is useful to take a step back and look at the three component technologies involved.
1. Photovoltaic Panels
Photovoltaic (PV) panels have been available for decades; the introduction of electricity feed-in tariffs has made them an economically viable producer of both electricity and revenue. A little-mentioned drawback with PV is that as the surface temperature of the panel rises the output drops, as electrical conductivity is impaired by heat. This can result in disappointing operational output in periods of sustained hot and cloudless conditions when one would otherwise expect PV panels to perform at their best.
2. Solar Thermal Collectors
Under direct sunlight, traditional solar thermal installations collect the sun’s heat and convert this into hot water, typically meeting the large part of a property’s summer hot water requirements. A major drawback is that in times of little or no sunlight there is little or no hot water. In winter, solar thermal collectors can be rendered essentially useless for long periods.
3. Heat Pumps
Heat pump technology has been available for many years and installations of both ground- and air-source systems are meeting heating demands worldwide. However, while these devices are potentially greener than burning fossil fuels directly for heat, they use large amounts of electricity to power compressors that upgrade latent heat to a useful temperature. The lower the temperature of the latent heat source, the less efficient the heat output.
Advantages of the Hybrid Solar Solution
The hybrid solar solution combines all three of the above technologies in such a way that the aggregate system output is far greater than those produced by the individual components.
How is this achieved? PV panels, as already mentioned, have a linear drop-off in electrical efficiency as the surface temperature of the panel rises. Given that PV panels are typically dark-coloured and mounted in such a way as to receive maximum exposure to the sun, this rise in panel temperature is inevitable. PV panels typically lose up to 0.5% in efficiency per degree rise in panel temperature.
© TOUCH BRIEFINGS 2011
However, with the hybrid solar solution, the PV and thermal elements are combined on a single panel – a photovoltaic thermal (or PV-T) collector. A flat-plate solar thermal collector is bonded with thermal conductive glue on to the back of the PV panel, thereby directly drawing heat away from the panel surface.
This has two main advantages: first, by reducing the panel surface temperature the electrical output is maintained at a higher level for a longer period, and second, with the PV and thermal elements
This British-designed and -built solution is the first in the world to combine three different renewable energy technologies into a single efficient and reliable system.
combined on a single panel less roof area is required, allowing for greater electrical and thermal output than could be achieved by separate PV and solar thermal installations on the same amount of roof space.
In the UK, electrical output from a PV-T panel is generally more than 20% higher over the course of a year than that achieved by the same wattage of good-quality monocrystalline PV panels. The uplift in electrical output is counteracted by a decrease in thermal output per unit area when compared with more traditional solar thermal collectors. This is a benefit in that it increases the area of roof that can usefully be used by PV-T.
Solar thermal output is dependent on direct sunlight, so for half of the day in summer and for most of the winter a solar thermal collector operates very inefficiently, if at all, and the heat collected is often at a much lower temperature than that required for use in a house. However, with the hybrid solar solution, the liquid loop in the solar thermal collector is connected both to the hot water cylinder and also to the heat pump.
With the integration of the heat pump, the output of the thermal collector is no longer directly related to the intensity of the sun and therefore a reasonably constant output temperature can be achieved irrespective of solar input – at times in summer when there is strong direct sunlight the solar thermal component of the PV-T will typically generate sufficient heat to cater for a household’s hot water requirements and the output is therefore directed straight to the hot water cylinder.
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