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Hybrid solar panel roof slashes energy bills

Scientists at Brunel University London have designed a new hybrid roofing system that could halve energy bills in new homes.

The patented system harnesses a unique 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 – superconductors of heat energy – which found in high-tech devices from PCs to the International Space Station, where they prevent it from melting in the heat of the sun on one side and freezing in the vacuum of space on the other.

Dr Hussam Jouhara of Brunel’s Institute of Energy Futures, who led the British team that developed the new system, said: “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 that 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 PV panels used to generate electricity.

“PV panels have an inherent challenge to the engineer,” he said. “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 4m x 400mm, 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.

Dr Jouhara’s system also addresses a wide range of practical issues in installing solar panels in new properties.

Attempts to integrate solar panel installation with conventional roofing techniques have a poor track record.

The solar roof is now undergoing extensive further trials at the Building Research Establishment in Watford, where a prototype is powering a standard three-bedroom detached house.

There has already been one unexpected finding, Dr Jouhara added: “Our flat heat pipes are so efficient that they can actually capture the energy from early morning dew evaporating off the trial roof.”

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