The potential for thermal storage to reduce the overall carbon emissions from district heating systems

A report by researchers at Tyndall Manchester demonstrates that significant carbon emissions savings can be achieved through the addition of thermal storage to combined heat and power with district heating systems (CHP-DH).  This study complements previous research which established the case for adding thermal storage to improve the viability of CHP-DH systems.

The researchers used industry standard modelling software to determine carbon emissions for a test case both with and without thermal storage of a CHP-DH system which uses gas reciprocating engines typical of many systems in the UK.

The useable heat and electricity produced by CHP plant delivered via a DH network displaces heat produced by building scale boilers and electricity with a higher carbon intensity drawn down from the grid. The addition of thermal storage to the CHP-DH system test case enables a greater annual quantity of electricity to be produced compared with the reference case with no storage. There is therefore an increase in carbon emissions from the CHP-DH system itself but this is offset from grid supplied electricity with a higher emissions factor which otherwise would be drawn down if the additional electricity was not produced.

For some cases peak load boilers could be decommissioned due to their lower utilisation which might also result in further emissions reductions in cases where these boilers are fuelled by oil or coal rather than by natural gas.

The analysis shows that the embedded carbon of the store, supply pipes and foundations are rapidly paid back by the additional carbon savings resulting from the more efficient operation of the CHP-DH system and consequent displacement of grid electricity.

The study suggests measures that could be taken to make the case for retro-fit of thermal storage more attractive for Energy Supply Companies as well as areas for further research.