You would think that the more sunlight that hits a solar panel, the better. When it comes to efficiency though, that's not the case – as photovoltaic cells heat up their efficiency decreases. To capture that heat and put it to good use, a team of scientists from Brunel University London has created a hybrid system that turns the whole roof into a solar generator.

The patented system combines flat heat pipes with PV cells to both heat water and generate electricity. Heat pipes are used to transfer heat away from surfaces where it's not wanted in various settings, such as personal computers, data center cooling, and even in space.

The flat heat pipes used are flat, measuring 4mm (0.4cm) x 400mm (40cm), which optimizes the collection solar radiation. Theses pipes heat water for use elsewhere as well as transferring heat away from the solar cells, which means their efficiency is not degraded to the same extent. During proof of concept tests, the scientists found that the pipes helped PV cells to cool by 15 percent more compared with a standard installation.

"Currently the panels would get hottest in the summer and roofs need to be designed to dissipate that heat," says Dr. Hussam Jouhara, a specialist in heat pipe technology who led the scientific team. "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 flat heat pipes also lend themselves to easy installation. "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," says Dr. Jouhara.

A prototype of the system is currently being tested on a standard three-bedroom detached house by the Building Research Establishment (BRE) in Watford.

Dr. Jourhara says they have already noted some surprising capabilities: "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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