HEAT NETWORK | CITIGEN that temperatures can be lowered at the heat exchanger for newer buildings. Chatzidiakos says the optimum mode of operation, which is a trade-off between cost and carbon, is to run one CHP and the heat pumps: Consuming gas to operate one CHP provides power to run the heat pump, with any surplus sold, while the heat pump can produce heat and chill to the network. The systems inherent adaptability helps ensure its commercial viability over time. We want to have exibility on our networks so that if, say, the gas price goes up, we can still run the network and meet our business case, Chatzidiakos explains. At the moment, with the gas price, it still makes commercial sense to run at least one CHP and the heat pumps, rather than run the heat pumps on their own, which we could do. In addition to responding to the gas price, the system will be able to vary its mode of operation in combination with the thermal store, to respond to the price of power. The system is currently being commissioned and the boreholes performance tested to see just how much energy they can yield and store. The intention is to balance the heat in and out of the aquifer to maintain its temperature at 14C. We can use all of the boreholes as a heat sink or source, or we can extract heat The system will be able to vary its mode of operation in combination with the thermal store, to respond to the price of power Heat pumps could run on their own without a CHP from one and return heat to the ground through another, explains Oluwole. As part of the project, E.ON has cosponsored a study from the universities of Birmingham and Cambridge to help gain an understanding of the impact of interaction from multiple boreholes. There are no rules or regulations to establish the interaction between boreholes, particularly from boreholes on one scheme being drilled close to those on another, says Oluwole. This project should allow Defra [the Department for Environment, Food and Rural Affairs] and the EA [Environment IMAX XTRA 2 The UKs experts in commercial heating EXPERTS Total plant room solutions by Ideal Heating and ACV UK idealheating.com 50 May 2022 www.cibsejournal.com CIBSE May 22 pp46-48, 50-51 Citigen Supp.indd 50 22/04/2022 15:57