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Naked Energy

A UK start-up believes its rooftop solar photovoltaic thermal technology can help decarbonise buildings

Vacuum tube solar technology captures significantly more heat than traditional flat panel alternatives, says UK company

The technology claim:
Combining photovoltaic and solar thermal collectors into a single product means significantly more heat and power is produced than is possible with separate PV and solar thermal installations

The key statistic
: The technology, known as Virtu, can produce 40% more heat and power, or energy in kilowatt hours, from a given flat roof area than separate photovoltaic and solar thermal panels

Trials:
Virtu has seen its first large-scale commercial installation at the Active Office project in the UK, a building designed to generate more energy than it consumes
UK solar tech start-up Naked Energy aims to decarbonise buildings with its eye-catching rooftop solar photovoltaic thermal (PVT) technology Virtu. Combining PV and solar thermal collectors into a single product means significantly more heat and power can be produced than is possible with separate PV and solar thermal installations in the same roof space, says Naked Energy. Its patented vacuum tube technology also does a better job of capturing heat for use in buildings than competing flat panel PVT technologies, says the company. Virtu can typically produce some 40% more heat and power, or energy in kilowatt hours, from a given flat roof area than a separate PV and solar thermal panel, claims Naked Energy. Fixed installation costs per unit of energy produced are also lower, helping to maximise investor returns. Other PVT technologies on the market also combine power and heating functions in a single product, but they typically have lower efficiency at the higher temperatures needed for solar thermal applications like domestic hot water and space heating. At 60°C Virtu has thermal efficiency, the percentage of available solar radiation converted into heat, of approximately 60%. This is about double that of the flat panel technologies that dominate the market. Flat panel PVT systems must typically be combined with heat pumps or used for smaller applications like heating a swimming pool at 30°C. Historically, the problem with PVT technology is that it uses flat panels and a lot of heat is lost into the atmosphere,” says Christophe Williams, CEO of Naked Energy. Virtu prevents these heat losses by being housed in a vacuum tube, something Williams says makes it globally unique”. With Virtu, a heat transfer device also draws heat away from the PV cells, cooling them to a uniform temperature and creating an environment in which power output is maximised.

Importance of certification

Naked Energy began operations in 2011 and is in the process of certifying Virtu with German product certification group TÜV for a European Standard for solar thermal and under International Electrotechnical Commission standards for PV, as a PVT standard does not yet exist. Certification is key for plans to scale up production, in part because subsidies and tax rebates for PVT technology are conditional upon it. Now a small company, with seven staff and three contractors, Naked Energy is also gearing up for a £2 million round of fundraising to further advance the technology after raising £1.1 million in its first public crowd-funding programme in July 2018. That will enable it to complete the certification process, build on the existing commercial pipeline for Virtu and bolster marketing efforts. Initial applications for Virtu, which has been supported by EIT Climate-KIC, a European public-private climate innovation partnership, are seen mainly for commercial and industrial buildings, although Naked Energy also plans to target large-scale applications like district heating in the future. Virtu has seen its first large-scale commercial installation at the Active Office project in the UK, a building designed to generate more energy than it consumes over the course of a year.


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Heather O’Brian