Hybrid solar panel heats water while generating electricity

UK renewables company Naked Energy has invented Virtu, a hybrid solar panel that simultaneously heats water and generates electricity.

The technology, developed by Naked Energy’s chief engineer Richard Boyle, integrates an electricity-generating photovoltaic cell into a hot-water-generating solar thermal panel. The solar thermal panels are placed into vacuum tubes and are unaffected by ambient temperature.

Nick Simmons, chief financial officer of Naked Energy, told The Engineer: ‘We can create more useful energy per square metre than conventional panels on the market today.’

Through combining the two technologies, Boyle was able to address one of the fundamental problems facing photovoltaic cells.

‘When photovoltaic panels get hot they become less efficient. For every 1º rise in temperature [from 25°C], you lose half a percentage point of efficiency,’ said Simmons. ‘A very efficient photovoltaic panel has a maximum efficiency of approximately 18 per cent. But by the time you get up to 65°C, which is quite a normal temperature on the face of a solar panel, you’re down to something like four per cent efficiency.’

Heat is transferred away from the photovoltaic cells with a patented thermosyphon technology that harvests the unwanted heat from the photovoltaic cell to heat up water.

As a result of taking the heat away and cooling down the photovoltaic cell, it is possible to generate more electricity than conventional photovoltaic cells.

‘We bond the photovoltaic cells to the thermosyphon, so there is a very small temperature differential between the photovoltaic cell and the thermosyphon. This means the photovoltaic cells are maintained at a uniform temperature,’ said Simmons.

Naked Energy has been working closely with Prof Peter Childs, an expert in heat transfer from Imperial College London, to further improve the efficiency of the solar panels.

Childs recently found that Naked Energy’s photovoltaic cells generate 40–45 per cent more energy as a result of the heat transfer method.

‘Sussex University is helping us put the product into production,’ said Simmons. ‘It’s been helping us make dyes and various tools to press the substrate of the thermosyphon, so we now have a way to manufacture the technology at scale.’

Naked Energy is currently on a trade mission to San Francisco that is being run in association with the Technology Strategy Board, UK Trade & Investment and other private sponsors.