Hot topics for the classroom

A multi-academy school trust expects to reduce carbon emissions by more than 9,000 tonnes with installation of heat-pumps in tandem with solar PV across several sites. The £5m project for Abbey Multi-Academy Trust (Abbey MAT) in Yorkshire, will see installation of 38 air-source heat pumps in five schools and is projected to save around £84,000 a year in energy costs.

The project, funded under the government’s Public Sector Decarbonisation Scheme (PSDS), uses solar PV arrays installed on school buildings, which partly power the AquaCiat TD300 heat pumps and help further reduce operating costs and carbon emissions.

During the summer, when the schools are closed any, surplus electricity produced will be fed into the grid, helping to cover energy costs for the rest of the year.

The project partners comprise consultant Energy Management Group, Robert Whetham Associates, HVAC specialist BReng Hull and Toshiba Carrier distributor Cool Designs.

David Ryder, Head of IT and Infrastructure at Abbey MAT, said: “At our large secondary schools, the heat pumps are deployed in clusters in the form of ‘farms.’ The units harvest low grade ‘free’ energy from the environment and upgrade it to a useful temperature, replacing the need for high carbon-emitting gas boilers in the majority of school buildings.”

The partners note the importance of optimising system performance by adjusting flow rates and set points to ensure comfortable indoor temperatures for students and staff throughout the day and over the year.

To meet tight funding deadline, Abbey MAT’s grant application required submission of detailed proposals for each school within a tight window of just two weeks. The Trust worked closely with decarbonisation specialist EMG to prepare the application.

One of the key challenges was to assess the requirements for upgrading existing radiators to take account of the lower water temperatures delivered by the heat pumps. This required room-by-room surveys from Rob Smelt, director of BReng Hull, in collaboration with EMG and Cool Designs on the technical aspects of the grant submission.

The audit took account of the type and size of existing heat emitters, glazing, building fabric, room orientation, insulation and occupancy levels. It resulted in around 50 per cent of existing radiators either being replaced with higher capacity units, or augmented with new units to achieve the required heating capacity. The additional investment required was covered by the successful PSDS grant.

The fine-tuning of the systems at those schools already converted has begun, with an initial water temperature of 65 deg C in the early morning reduced to 50 deg C once students are on site and in class – taking account of the fact they  contribute 3 kW of heat they within the average classroom.

The Trust is now developing an innovative school-wide heat map, produced by using temperature data from new heat-sensitive fire alarm systems.

Mr Ryder said: “The idea is to give a real-time overview of actual conditions in each space across a school, so that set-points and flow-rates from the heat pumps can be further optimised.”

Paul Smith, Sales Director for Applied Products, Toshiba Carrier UK, said: “In adopting high performance heat pumps – with the added benefit of solar-generated electricity to power them – the schools have undertaken a major transformation that sets them firmly on the path to becoming carbon neutral. It is a journey that all public and commercial buildings will need to make if the UK is to achieve the nation’s strategic goal of being carbon neutral by 2050.”