HEAT NETWORKS | PLYMOUTH CITY CENTRE PLYMOUTHS GENERATION GAIN When Plymouth City Council looked at heating and cooling buildings more efficiently, it found the areas geology offered a source of energy that enabled it to use the latest heat network technology. Andy Pearson reports T Typical hot pipe temperatures for heat networks Conventional: 80oC 4th generation: 55oC 5th generation: 14oC he construction of Plymouth City Councils 5th-generation district heating and cooling (5DHC) network began last month. It started with the drilling of the first well into the aquifer that flows through the limestone strata on which areas of the city are built. This pioneering low-carbon project will supply a cluster of buildings in the city centre with heat and coolth. It is one of several district energy schemes being explored by the council as part of its initiative to reduce carbon emissions. Generating heat represents the biggest energy use in the UK so, to meet our target of reducing greenhouse gas emissions by at least 80% by 2050, we will have to decarbonise nearly all heat generation in buildings and most industrial processes, says Jon Selman, low carbon city officer in the Strategic Planning and Infrastructure Service at Plymouth City Council. Reducing demand for heat through improved energy efficiency will be important but it will not be enough to meet the 2050 target. This is where heat networks have a role to play. Plymouth City Council never set out to pioneer the use of 5DHC, which features no central energy centre and uses local heat pumps to heat and cool buildings. But it was participating in the HeatNet project (co-financed by the European Regional Development Fund) to explore the implementation of 4th-generation district heating and cooling (4DHC) networks in the city. Conventional heat networks typically deliver hot water at 80oC, usually heated by gas boilers or a CHP engine housed in an energy centre, says Selman. Fourth-generation district and cooling networks feature an energy centre supplying heat outwards to buildings, but they usually operate at a lower temperature than conventional networks [around 55oC], resulting in lower capital costs, lower heat losses and greater energy efficiency. (See Figure 1). The 4DHC networks were of interest to the council because their lower temperatures offered the city the opportunity to use waste heat and renewable heat sources, such as ground source. Plymouth is one of the pilot areas to demonstrate the application of this approach, says Selman. Mapping heat loads Under the HeatNet project, the council commissioned BuroHappold and Building Energy Solutions to map the heat loads and heat sources for Civic Centre Debenhams 38 August 2019 www.cibsejournal.com CIBSE Aug19 pp38-40 Plymouth heat network.indd 38 19/07/2019 14:46