Is Solar Thermal the Cinderella of Clean Energy?

On this week's episode of Profit Meets Purpose, Christophe Williams - Founder and Chief Executive Officer of Naked Energy - shares how solar thermal is the forgotten Cinderella of the clean energy story. 

Christophe Williams does not have the traditional engineering background of many a clean technology founder. His former working life saw him lead advertising campaigns for global brands such as Sony, Microsoft and BMW - winning a Guinness World Record for a Toshiba commercial. 

It was a chance conversation with a cameraman’s brother in 2009 that introduced him to solar thermal energy. “He opened my eyes to the big heat problem, heat being half of all the energy we use on the planet,” Williams says. Solar thermal technologies take the warmth of the sun and put it into a fluid that can be used to heat buildings. The latent potential of this zero carbon, zero cost source of heating eventually led to the creation of Naked Energy.  

Since its founding in 2009, the company has scaled significantly and has delivered some flagship projects. “We're just a little player. It's a 20 billion industry right now. I call it the Cinderella of solar - it gets overlooked.” For the sector to fulfill its potential, says Williiams, “we have to raise awareness, do really high profile projects, plus we've got to influence policy and that takes time”.

For investors seeking opportunities in emerging technologies, Naked Energy stands out as a compelling example of how clean energy innovations can successfully scale. Williams embraces the challenges of this journey, highlighting the constant balancing act required to grow a cleantech company - from securing funding and educating future customers on the value of sustainable solutions, to building the right team, forming strategic partnerships, and advocating for supportive policy change.

Listen to the full episode here. 

Solar thermal energy

The wider energy landscape shows growing momentum for renewables. In 2024, 5.2% of renewable energy came from solar, and in the first half of 2025, renewables overtook fossil fuels as the world’s leading source of electricity. Embracing this transformation, Naked Energy is positioning itself as a key player in the clean energy economy. The company now holds 24 patents, has achieved TÜV certification for its technology, and has raised £30 million in funding. With just over 30 employees, it has completed 150 projects across 10 countries, spanning sectors from hospitality to heavy industry.

Naked Energy’s flagship Virtu (PVT) photovoltaic/thermal cooling systems technology combines solar photovoltaic (PV) and solar thermal systems into a single product that generates both electricity and heat.

Unlike conventional solar panels, Virtu uses sealed glass tubes, similar to a thermos flask, which trap the sun’s warmth. Inside each tube, silicon PV cells are bonded directly to a heat exchanger, so the system simultaneously produces hot water and power. This hybrid approach means Virtu delivers four times the carbon savings of standard PV. “Even in the UK or cooler climates, you’re still getting hot water, and that’s unique,” Williams explains.  

The company began to scale in 2013, after winning a Shell engineering competition that delivered £40,000 in prize money and a further £500,000 from angel investors - enough for Williams to commit to it full time. Barclays invested in 2022, the 12th investment under the bank's £175m Sustainable Impact Capital programme which makes investments in innovative, environmentally-focused businesses. 

Williams explains that this investment played a foundational role in Naked Energy reaching new markets, not least to Barclay’s “significant presence” in the US. “Decarbonising heat on a global scale is needed to address climate change,” he says.  

In 2024 the firm closed its Series B raise led by E.ON. Daniel Joisten, Head of Innovation Commercialisation at E.ON Energy Infrastructure Solutions, said at the time, “Naked Energy’s solutions have distinctive and convincing value propositions. We will utilise them to help our customers, in industries such as food & beverage and hospitality, to decarbonise their businesses profitably.”

Having successfully closed successive funding rounds, Williams says Naked Energy is now in the “fourth valley of death”, whereby it has proven technology and has customers, but its price point remains too high for wider adoption. He reasons that, “hardware costs have fallen but labour hasn’t. Design, integration, installation, those fixed costs remain. Our approach is to be so efficient that those costs amortise faster.” 

Acceleration through innovation

Williams believes that the role that solar-thermal technologies can play in the transition to net zero are being undervalued. Electrification has dominated the renewable energy conversation, but Williams argues it cannot carry the load alone. Upgrading a national grid that took a century to build, he notes, is not something that can be achieved in a single decade, especially as AI data centres, electric vehicles and heat pumps push demand ever higher. “There’s a slight oversimplification that we can electrify absolutely everything,” he says. “The grid must be near-zero carbon and have capacity for growing demand. We need a full suite of solutions.”

As a board member of Solar Heat Europe, a trade association, Williams is advocating for heat to receive the same policy attention as electricity. He calls for clear government targets to transform the power sector, arguing that harnessing the sun’s heat locally could ease pressure on the grid while addressing one of the most overlooked sources of emissions. “We’re talking to the European Commission about the Fit for 55 Act and the directives they’ve got for renewable energy and building performance,” he says. “There is policy coming but by the time it filters through each country’s mandates, it takes too long.”

Against this slow policy backdrop, Naked Energy is building its own technologies that can accelerate decarbonisation now. The company has paired its hardware with a digital monitoring platform Clarity 24/7, which tracks real-time energy performance, output and carbon savings, providing customers with insights into their energy use and carbon impact.

With hardware costs still a barrier to implementation, the company is complementing its products with software designed to speed up and encourage adoption. Its upcoming platform Clarity 360, harnesses data from Google’s Project Sunroof to generate system layouts, costings and carbon savings in minutes rather than weeks. If successful, it could dramatically cut design costs and help organisations that, as Williams puts it, “want to decarbonise but don’t know where to start”.

Ultimately, Williams believes that the growth of sectors like solar heat depends on outcompeting alternative energy sources and proving how these technologies can deliver quickly, efficiently, and at scale.​​

Landmark projects and future growth

Naked Energy has achieved some landmark successes with the adoption of its technology. For example their project at the British Library, a Grade I-listed complex next to London’s St Pancras station. The library needed low-temperature heat for space conditioning, domestic hot water and the careful humidity control of rooms housing rare manuscripts. 

Historic preservation posed a challenge to the library's adoption of renewable energy. English Heritage, concerned about reflective glare and visual impact, prohibited the use of standard PV panels on the roof. “Our tubes are low-profile, 26cm, and concentrate light into the absorber,” Williams explains, “‘glint-and-glare’ studies cleared them. Only our product was allowed.” The result, he adds, is “the largest solar heat project ever in the UK,” supplying two low-temperature circuits and directly displacing gas.

Other sites where Naked Energy has installed its technology include luxury hotel the Mandarin Oriental Hyde Park and at the grounds of renowned tennis championship Wimbledon. 

Scaling growth

Moving forward, Williams recognises the need to scale further if solar-thermal energy is to make a meaningful contribution to the global clean energy transition.

“Naked Energy doesn’t need to just do thousands of buildings,” he says. “We’ve got to do hundreds of thousands, millions, of buildings and projects at scale. That’s going to require not only more capital, but larger funds willing to make £100 million or £200 million investments.”

For Williams, the next stage of growth will require as much building awareness through education as it does engineering and product development. He believes that policymakers, investors and consumers alike need to better understand solar thermal energy’s potential role in decarbonising heat.

“Solar thermal has been the forgotten Cinderella,” he says, “but that’s starting to change.” With its blend of hardware innovation and digital intelligence, Naked Energy aims to bring solar thermal into the mainstream lexicon, transforming how the world powers and warms its buildings.

Listen to the full episode here.