The patented system harnesses a mixture of technologies to pre-heat domestic hot water for radiators, baths and showers while also generating electricity. More than half of domestic energy use in the UK is to heat water.
At its heart is the use of heat pipes – devices familiar from high-performance cooling schemes for high-dissipation processors in PCs and other products.
Dr Hussam Jouhara of Brunel’s Institute of Energy Futures, who led the team which developed the new system explained: “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”.
“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.”
Heat pipes seemed to Dr Jouhara an obvious solution to a major technical issue with solar cell or photovoltaic (PV) panels used to generate electricity.
“PV panels have an inherent challenge to the engineer,” explained Dr Jouhara. “The more intense the sunlight the more electricity the cells will produce but only a fraction of the sun’s energy can be turned into electricity.
“So the sunnier it is the more of that unusable energy hits the cell which, in turn, heats it up. As PV cells heat up their electrical generation ability is degraded. Heat pipes, in this case, constructed in flat panels 4 m x 400 mm, will whisk that away to heat domestic hot water.”
In proof-of-concept tests, PV cells cooled by Dr Jouhara’s methods outperformed identical panels by 15%. And rather than being wasted, almost the full spectrum of energy from the sun is harnessed.
The system also addresses a wide range of practical issues in installing solar panels in new properties. Attempts to integrate installing solar panels with conventional roofing techniques have a poor track record.
“What was needed was an engineered, systems approach,” said Dr Jouhara. “Our solar panels are PV coated for the most southerly-facing aspect of the roof and are designed to clip together as a weather-tight roof as simply as clicking together laminate flooring.