Are you ready for a heating revolution?

To heat a building to a typical 23°C, traditionally something is heated up by a heat source at hundreds or indeed thousands of degrees centigrade to a temperature of typically 70°C, and then cooled down to achieve the temperature balance required. The same goes for hot water. It’s often heated to around 65°C then cooled to a more tolerable level. This approach is hugely wasteful but is the norm in today’s heating and hot water systems.

A rulebreaking solution from Minus7 challenges this traditional practice in an effort to reduce unnecessary energy wastage. It does so by harnessing renewable energy. And, while the Minus7 approach is contributing to climate change reduction, it is also tackling the growing challenge of fuel poverty faced by many today. 

The concept behind Minus7, which is the brainchild of Naval Architect Alastair Hunter, is relatively straightforward. It combines solar thermal, heat pump and energy storage technologies to capture, boost, store and distribute energy as heat. At its core is a roofing system made of liquid-filled solar thermal panels that can harvest energy day and night - at temperatures as low as -7°C (hence the name Minus7). The captured energy is then transferred to underground thermal storesvia heat exchangers. The stores work as energy sources for the heating and hot water requirements of the building.

The complex balance between the components that make up the system is discretely controlled by a solar energy processor (SEP) developed by Minus7, while the building occupants can control the heating and water temperature with a conventional thermostat and timer. This approach is not new.

Back in the 1980s, a prototype of the system was built into a house using similar principles. Its design was based around a steel frame. Water circulated within the roof element of the frame and a heat store was incorporated into the core of the building.

“This solution didn’t gain traction as it was ahead of its time,” said Hamish Wilson, Director at Minus7. “The appetite for renewable energy solutions just wasn’t strong enough. Throughout the 1980s and 1990s various attempts were made to commercialise a system of this type, but unfortunately they all failed.”

Today, the situation is very different and much more favourable. The economic environment is right, with incentives available for the adoption of renewable energy solutions, and there is a greater understanding of the environmental benefits that renewables offer. renewables offer. However, Hamish believes the real enabling factor has been an evolution of the technology and knowledge, which has allowed significant improvements in the control technology, together with a better understanding of the mechanisms of heat capture and storage. As a result, systems like the Minus7 solution are able to realise the full potential on offer.

“The more sophisticated technology available today enables much finer control of a three stage system,” added Hamish. “For example, our SEP knows when to run the heat pump and at what temperature. This capability means the combined solution is now a viable alternative to traditional heating methods; in both its effectiveness through temperature management and its efficiency through accurate levels of control.”

Everything is under control
It is the knowledge of the control strategy that gives Minus7 its competitive edge. The company has spent years developing a deep understanding of the nuances of controlling a heat pump, controlling fluid temperatures coming from a roof and how they distribute heat into buildings at lower temperatures.

While this evolution in technology, and a growth in demand for sustainable solutions, makes the project viable today, commercialising it has by no means been easy for the Minus7 team. “Fine tuning the control technology to maximise system efficiency and effectiveness has been tricky, but by far and away the biggest problem has been the bureaucratic minefield,” continued Hamish.

Getting BRE (previously the Building Research Establishment) recognition with a hybrid solution was the biggest challenge the company faced by a long way. “The UK Government’s subsidy regime is highly prescriptive. For example, it defines heat pumps as either ‘ground source’ heat pumps, ‘water source’ heat pumps or ‘air source’ heat pumps. Because our solution offers an entirely new approach there was no existing category for it,” said Hamish.

To overcome this barrier, the Minus7 team had to work with BRE to develop a new category Solar Assisted Heat pumps. It was a process that took five years and relied on dogged persistence on the part of the Minus7 team. And it may not have succeeded at all were it not for support from some early adopters of the technology, who backed the company through much of the early prototyping phase. These clients enabled the company to install working systems and get real data from properties, to demonstrate that the solution, and its concepts, worked.

Worth the effort
The hard work eventually paid off; Minus7 have the certifications needed to access available subsidies and appropriately classify its products within the construction trade, and as a result, it now has a commercially viable product to take to market.

The technology still has a little way to go before the costs involved make it an effective choice for a typical three-bed semi. So the focus is on new-build estates, blocks of flats and in particular, housing associations—where the solution is helping to address fuel poverty, with tenants able to buy their energy for significantly less than traditional fuels such as gas.

Looking ahead
Of course, the potential for changes to the renewable heat incentives creates a risk for the business. However the Minus7 team has a reasonable degree of confidence that the current incentives will be around for at least four more years. In that period, the business needs to work hard to reduce manufacturing costs of the system by around 40%, at which point it will be directly competitive with gas, regardless of the scale of the project. This objective is now a key strategic focus for the company and one that the team are confident that they can sucessfully meet.

But as you may imagine, the Minus7 team is not resting on its laurels; it is constantly working on new products to complement the current system. A key focus of this work is a roof system with embedded photovoltaic cells. The cells are cooled by the water in the roof, and as a result, a significant uplift in the yields from the PV cells is expected when compared to standard solutions.

When this technology is perfected, the Minus7 team will be able to meet the aim of providing a full heat and power solution which can, in effect, take an entire residential estate off the traditional power grid, heralding a sea change in what we understand as the normal model for power generation and distribution.

Minus7 has worked with Breakthrough funding, a company that helps UK SMEs achieve R&D tax credits - a government scheme created to enhance and reward innovation amongst UK businesses. Could you be eligible? Click here to learn more.

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