Nearly two decades ago, Andrew Bissell was relaxing in his beachfront home near Edinburgh, contemplating his next steps after he and his wife, Susan Lang-Bissell, had sold their medical imaging startup. Faced with the prospect of either retiring or embarking on a new venture, Bissell found himself at a crossroads.
“Do we retire or do we start again?” Bissell recalled in an interview with TechCrunch.
During this period of reflection, Bissell came across a science magazine article that changed his trajectory. The article warned of potential sea level rises ranging from 30 centimeters to a meter by the end of the century, due to climate change.
His reaction was immediate. “If that happens, the ground floor of our home would be underwater twice a day,” Bissell thought. “Now imagine that happening to millions of homes around the world. That’s simply unacceptable.”
Rather than take a conventional environmental route, such as joining an organization like Greenpeace, Bissell and his wife took a different approach. They decided to launch Sunamp, a company aimed at tackling climate change through innovative energy storage solutions. Partnering with a lab at the University of Edinburgh, the couple set out to develop a thermal battery capable of storing solar energy as heat, which could then be used for home heating and hot water.
At the core of Sunamp’s technology is a thermal battery that relies on a key ingredient: sodium acetate trihydrate (SAT), a compound commonly found in salt-and-vinegar potato chips. SAT, along with water and special crystal habit modifiers, forms the basis of Sunamp’s heat storage solution. The concept itself isn’t new — SAT has been used for years in hand warmers, where it releases heat when crystallized. However, Sunamp’s innovation allows this process to be reversed, enabling heat to be stored for future use.
One of the main challenges with SAT is its tendency to degrade over time, eventually failing to recrystallize. Sunamp overcame this hurdle by introducing a type of acrylic as a crystal habit modifier. This ensures that the SAT crystals form correctly over and over again, extending the battery’s lifespan. Bissell explains that the result is a material that can last for up to 40,000 heating cycles, equivalent to over 50 years of daily use. Sunamp has branded this material as “Plentigrade.”
The goal behind the technology is to capture surplus renewable energy — whether from solar or wind — and store it as heat. When renewable energy is abundant, the battery charges. When energy demand peaks or the wind isn’t blowing, the battery discharges, providing heat through the crystallization of the SAT.
Sunamp has already established a presence in the United Kingdom and Italy and is now aiming to expand into other Western European countries and the United States. As part of this expansion, the company is in the process of raising Series B funding. According to Bissell, Sunamp is generating revenue in the “tens of millions range.”
The company’s first mass-market product, a compact heat battery designed for domestic hot water, caters to customers with limited space. “Globally, about half of homes don’t have the space for a traditional hot water tank,” Bissell said. “We’re targeting the other half, the ones who can’t afford that extra room.”
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