The ENGINEER

Balanced Energy Network decarbonises heating and cooling

By Stuart Nathan 7 November 2018

Collaborate to Innovate 2018

Category: Energy and environment

Winner: Balanced Energy Network

Partners: ICAX Ltd, LSBU, Upside Energy, Mixergy, Origen Power, Cranfield University, Mixergy and TFGI

A system for decarbonising heating by sharing energy between buildings using heat pumps

A new type of heating network described as an “Internet for heat” is currently reaching the end of a 27-month program. BEN, which is part funded by Innovate UK, is an effort to decarbonise heating, which accounted for over 30% of the UK’s total carbon emissions in 2016. The government describes decarbonisation of heat as the most difficult technical challenge in meeting carbon reduction targets. In 2017 a requirement was set to supply 40TW hours of heat through low carbon networks by 2030, and 10TW hours by 2020. As some 80% of homes built today will still be around in 2050, the BEN project was set up both to be suitable for installation in new-build housing and to retrofit to existing buildings.

The collaboration team is seeking to demonstrate a concept for heat sharing known as a Fifth Generation Heat Network (5GHN), which is suitable for delivering heat from a new type of advanced heat pump operating at a normal heating circuit temperature of 80°C, alongside existing gas boilers. The 5GHN is able to expand organically and link piecemeal across a city, and is linked to large-scale seasonal thermal storage from a natural aquifer and also shorter term high-temperature storage in advanced water tanks; all of these are capable of operating under control of a cloud-based demand-side response aggregator.

This Fifth Generation Heat Network has been developed by ICAX, the coordinator of the project. ICAX also designed and developed a new type of high-temperature pump which is central to the concept as it allows the new heat pump to replace gas boilers without the need to refurbish existing heat distribution systems.

LSBU, meanwhile, is acting as the host site for the initial network, while also providing system modelling and assessment of it. Upside Energy provided demand side management analysis and cloud-based control of the electrical elements of the system. Mixergy designed and developed the thermal storage cylinders. Origen Power has developed a a fuel cell calciner in partnership with Cranfield University, which enables electricity to be generated in a way that removes carbon dioxide from the atmosphere.

Put simply, the heat sharing network works by transferring warmth via piping circuits between buildings at near ground temperature, and recovering it via heat pumps in each building. These heat pumps are designed to replace gas boilers in existing buildings without the need to replace existing heat distribution systems.

The advantages of this type of system over conventional CHP (combined heat and power) district heating systems include integration of diverse heating systems through the recovery of low-grade waste heat, delivery of simultaneous heating and cooling, and reduction of installation costs through making use of the existing infrastructure. When buildings require cooling the heat can be released into the district circuit to warm those buildings that need it. The result is a flexible network which advantages both those releasing heat and those extracting it: a heat sharing dividend. Built into the system is equipment to exchange information about sources and needs for heating and cooling that allows this flexible use of the available energy.

“There are tremendous energy efficiency gains in heat networks, and we’ve known this for a long time,” says Aaron Gillich, senior lecturer in energy and building services engineering at LSBU. But there are significant engineering challenges to establishing such networks, he adds, not least their size. “These things are big. We have to plan them decades in advance, we have to know what demand is going to be, who the clients are going to be. The long-term legal issues of clients and suppliers become very tricky to plan that far in advance.”

One difficulty, Gillich says, is that traditional systems only provide heating. The UK is a very heating oriented country, but with climate change we may have to think more about limiting summertime overheating. The use of heat pumps in the system permits the electrification of heating, he says, a vital component in decarbonisation as electricity can come from low carbon sources. At LSBU, Gillich explains, the heat pump system is linked to borehole thermal storage, with two 100m bores drilled into the chalk aquifer by drilling specialist TFGI from where water can be drawn when needed at around 15°C to regulate temperature of the loop. “We haven’t really done this in the UK yet for some reason,” he says. “There are boreholes serving individual buildings, but they haven’t been linked into networks before.”

The other essential component of the system is demand-side response, Gillich said. This is analogous to a battery management system in the electrical grid: it turns on charging and discharging when needed to balance the entire system. At BEN it shuttles heat between buildings, storing it into 10,000 litre hot water storage tanks when necessary. The fuel cell calciner component provides a non-intermittent way of generating electricity to power the heat pumps.

The calciner works by feeding natural gas into a standard fuel cell to generate electricity. This process generates heat, and this is used to break limestone down into lime (CaO) and pure CO₂ which can be used, or stored underground. The lime produced can also be used in industrial processes, during which it absorbs carbon dioxide and is converted back into calcium carbonate – the original limestone. Overall, the process is carbon negative, absorbing 800g of carbon for every kilowatt hour of electricity generated as opposed to releasing 400g of carbon dioxide for every kilowatt hour with conventional combustion technologies. Origen Power’s Tim Kruger suggests using the lime to counter ocean acidification. “You absorb about twice as much carbon dioxide when you add it to seawater as when you use it industrially”.

The project is already reaping rewards for the partners. ICAX and LSBU have won two further collaborative R&D programs and are collaborating on a further R&D proposal. Origen has won a major further R&D award and is working on proposals with both ICAX and LSBU. Upside and Mixergy have also won an R&D award. Commercial gains have also been forthcoming for ICAX, Upside, Mixergy and Origen.