Balanced Energy Networks

by Edward Thompson

Clean Heating without combustion

A retrofit district heating system has recently been installed in the heart of London South Bank University (LSBU) by the Balanced Energy Networks (BEN) consortium.

The BEN project, which is part funded by Innovate UK, incorporates a number of innovations which highlight the route towards clean heating. That in turn answers the stated objectives of BEIS's recent Clean Growth Strategy and DEFRA's objectives in its Clean Air Strategy consultation.

BEIS believes in district heating as a route to reducing carbon emissions. However, there are formidable obstacles in the way of establishing district heating systems based on combined heat and power (CHP): these are centred on the enormous cost of establishing and administering a central energy centre, the cost and disruption of installing heavily insulated pipework in the ground, and the legal barriers to signing up tenants for very long-term contracts.

In the case of London South Bank University (LSBU) there was no free space that could have been allocated to installing a central CHP-based Energy Centre.

There are also increasing concerns about the idea of installing combustion-based engines in the centre of London which is already breaching air pollution limits. There is also the realisation that with the rapid decarbonisation of the Grid, Combined Heat and Power based on combustion is no longer a valid route to reducing CO₂ emissions.

An alternative approach has been designed and delivered based on an ambient ground temperature Heat Sharing Network. This network draws water from the London Chalk Aquifer 112 metres below the ground. It circulates the water via the plant room of each building on the network, and returns the water to the aquifer via another discharge borehole. A high-temperature heat pump has been installed in the plantroom of each building on the network. The pump extracts heat from the water in the network and transfers it to the existing heat distribution system in each building.

This form of heat transfer avoids the use of combustion completely. Therefore there are no emissions of CO₂ on site, which answers the Clean Growth Strategy comprehensively. There are also no emissions of NOx, SOx or particulates which answers totally the Clean Air Strategy.

As well as avoiding CO₂ emissions and air pollution issues the BEN installation at LSBU has avoided the cost of digging up the roads within the university estate to install heavily insulated metal pipe network. Instead, low diameter plastic pipes have been mounted on the walls of existing buildings to transfer water from the aquifer via plant rooms in each building and back to the aquifer.

The cost and disruption of refurbishing the heat distribution mechanisms in each building has also been avoided by retaining the existing heat emission systems and using specifically designed high-temperature heat pumps – which can deliver water at up to 82°C when required. This was key to installing the new network into a busy site without the buildings suffering any downtime. The existing gas boilers have been retained on site as a back up.

In addition to the innovations above the heat pumps employ Demand Side Response ("DSR"). They are linked to the electric supply companies via a DSR Aggregator which permits them to take advantage of cheaper electricity when this is offered by the Grid – and to avoid the use of expensive electricity in peak hours.

The BEN consortium has designed and installed heavily-insulated thermal energy storage tanks for hot water which provides additional flexibility and capacity to take advantage of Demand Side Response, both for heating and for domestic hot water.

The consortium comprised: London South Bank University; ICAX who provided the design and project management; Upside Energy who worked with ICAX to enable Demand Side Response for heat pumps and heat storage; Mixergy who designed and provided thermal energy storage tanks; TFGI who drilled the boreholes to the London Aquifer, Origen Power and Cranfield University who have designed and constructed a fuel cell calciner demonstrator which generates electricity in a combustion-free process that removes CO₂ from the atmosphere.

The result is a network which balances the temperature in the buildings against the thermal mass of the London Aquifer. The BEN is capable of transferring heat into the buildings in winter, and out of the buildings to the aquifer in summer. The timing of electric consumption from the Grid is balanced against the fluctuating diurnal demand and supply for electricity as signalled by Demand Side Management in real time.

A BEN also provides a mechanism for balancing the budgets of its owners, as it is radically cheaper to install than a CHP-based network and also cheaper – and cleaner – to run than a gas-based network for heating and a chiller based system for cooling.

The horns of the Energy Trilemma have been blunted.