HEAT NETWORK | SWAFFHAM PRIOR (AC)/39MW (DC) solar farm owned by CCC. It was decided that both projects would connect to the same distribution network substation. A shared connection would allow electricity to flow behind the meter, enabling CCC to selfsupply renewable electricity directly to itself, says Messenger. By combining the solar farm with the energy centre, we were able to rationalise our network connection costs, he adds. This also provides an advantage in managing our export and import to and from the network. The electricity generated by the solar farm that is consumed by the energy centre would have otherwise been sold via a wholesale export agreement. The export unit rate would be approximately a third of the cost of peak retail import unit rate. Thanks to the comparatively large scale of the solar farm, coupled with 4x50m3 thermal stores, Bouygues E&Ss models predict that the vast majority of electricity consumed by the energy centre will be sourced from the solar farm. The thermal stores are to be used to meet short-term peaks in demand, and will enable the system to optimise tariffs. Generally, they will be charged during the day when electricity is available via the solar PV array to provide heat the following evening. Their inclusion, coupled with the hydronic design of the scheme, allows us to deliver a larger capacity of heat into the network for a short duration than the total capacity of the heat pumps in this sense, the thermal stores act as a capacitor, says Messenger, who adds that they can also supply several hours heat into the network in the event of unplanned maintenance. Further back-up comes from an electrode boiler, made feasible by access to the solar farms cheap electricity (see panel, Backup heating on page 21). Heat-supply agreements Avieco engaged with the community over the terms of the Heat Supply Agreement. It is another utility, but the contracts are much longer-term, says Troup. Consumer protection is expected to be provided by Ofgem, which is the regulator for heat networks. To ensure residents dont pay a premium for their community-supplied heat, the tariff has been linked to the price of heating oil. The other key issue is that joining the community heat project costs nothing if you sign up before the construction is finished this means everyone, independent of wealth, can join, says Dupr. The project capital costs are 11.9m, which are being funded by a 2.9m grant from the Heat Network Investment Project and capital borrowing by the council. The cost over the life of the project will be covered by heat charges and income from the Renewable Heat Incentive. Another challenge was obtaining permission to run pipework under a public highway. No statutory regimes allow this in practice, but CCC found alternative legislative powers that enabled it to access the highway. The primary network being installed by Pinnacle Power is racing to go live by spring 2022, in time to apply for the RHI grant. There will be a gradual ramping of connections over the first five years, with a target of around 100 properties in the first 12 months. We aim to deliver around 4GWh/ annum within the next five years, which is around 75% of dwellings, says Messenger. When up and running, Englands first rural village heat network is projected to save more than 47,000 tonnes of carbon annually, and could pave the way for similar schemes. Its not surprising that there are many others interested in replicating the scheme, says Dupr. This is a historic village with many challenges including listed buildings, private and narrow roads. We could not have chosen a more difficult village to retrofit if it can be done here, it can be done anywhere. CJ The energy centre is 500 metres from the village. The field with the ground arrays can no longer be ploughed but instead will become a wildflower meadow to boost biodiversity 24 February 2022 www.cibsejournal.com CIBSE Feb22 pp20-22, 24 Swaffham Prior.indd 24 28/01/2022 16:19