The patented new system incorporates a unique mixture of technologies to pre-heat domestic hot water for radiators, baths and showers while also generating electricity. It uses heat pipes – super conductors of heat energy – found in high-tech devices. More than half of domestic energy use in the UK is to heat water.
“As a professional engineer with a long-term research interest in heat pipes I could see many advantages in applying this technology to a renewable energy system” said Dr Hussam Jouhara of Brunel’s Institute of Energy Futures and leader of the team that developed the new system. “Until now there was no system which fully addressed all the technical and practical issues that face making an entire building’s roof a solar-powered generator of both heat energy and electrical energy.”
Dr Jouhara explained that PV panels represent an inherent challenge to the engineer in that the more intense the sunlight, the more electricity the cells will produce although only a fraction of the sun’s energy can be turned into electricity. The sunnier it is, the more of that unusable energy hits the cell which, in turn, heats it up. Increased heat degrades PV cells electrical generation ability. The obvious solution to this major technical issue seemed to be heat pipes installed in flat panels, which will whisk that heat away to produce domestic hot water.
Dr Jouhara’s methods outperformed identical panels by 15 per cent in proof of concept tests in addition to the full spectrum of energy from the sun harnessed instead of being wasted. The new panels are also PV coated for the most southerly-facing aspect of the roof and are designed to clip together to form a weather-tight roof. This addresses a wide range of practical installation issues where previous attempts to integrate solar panels with conventional roofing techniques have a poor track record.
“When we constructed our test roof using standard “off-the-shelf” roof trusses, tradesmen were able to quickly and easily screw together the panels with no extra guidance than a simple set of written instructions” Dr Jouhara added. “The heat pipe technology also turns the biggest downside of integrating solar panels into conventional roofs into a positive. Currently the panels would get hottest in the summer and roofs need to be designed to dissipate that heat. Simply insulating the house below is not a good solution as that simply traps it driving up the PV panel temperature and further lowering its performance. With our system there is no waste heat.”
The new solar roof is now undergoing further extensive testing at the Building Research Establishment (BRE) in Watford where a prototype system is currently powering a standard UK three-bedroom detached house. This has already achieved one unexpected finding in that the system is so efficient it can capture the energy from the evaporation of early morning dew off the trial roof.
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