C2I 2018: Balanced Energy Network (BEN) decarbonises heating

A system for decarbonising heating by sharing energy between buildings and using heat pumps is under trial in London

Intended to create and develop a new type of heating network described as an “Internet for heat”, that is currently reaching the end of a 27-month program funded by Innovate UK, BEN is part of an effort to decarbonise heating, which accounted for over 30% of the UK’s total carbon emissions in 2016. The government describes this effort as the most difficult policy and technical challenge in meeting carbon reduction targets, and 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 project was set up both to be suitable for installation in new-build housing and to retrofit to existing buildings.

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

The CWHN was developed by ICAX, which is acting as the coordinator of the project; it also designed and developed a new type of high-temperature pump which is central to the concept. LSBU, meanwhile, is acting as the host site for an experimental network, while also providing system modelling and assessment of the network. Terra Firma Ground Investigations (TFGI) designed and drilled two 110m boreholes to regulate the network temperature.  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; and Origen Power developed a device called 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.

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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 installation costs through making use of the existing infrastructure. When builders 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. 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 do 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 represent the electrification of heating, he says, a vital component in decarbonisation at their power 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.”

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, he explained: it turns on charging and discharging when needed to balance the entire system; in this case it shuttles heat between buildings, dumping it into 10,000l 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 line 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.