The Dimplex SI 100 TE and SIH 6 ME heat pumps recover waste heat from the National Grid substation in Worcestershire and use it to heat the main substation building and a neighbouring Environmental Education Centre. Using waste heat in this way means there is no need for backup heating or a ground source collector, which would have been unachievable due to the confines of working within an electricity substation.
The Education Centre, which is mainly constructed from wood and won awards for its sustainable build in the late 1990s, now benefits from free heating for its total space heating requirement of 27kW. Part of the National Grid's Environmental Education Centre Network, it is a partnership between the National Grid, Worcestershire County Council and Worcester College of Technology.
Rook Services worked closely with Dimplex’s in-house renewable heating design team to install two Dimplex ground source heat pumps at Bishops Wood, connected via a header pipe to a series of four dry air coolers. Each air cooler is located within an individual brick enclosure which houses a 275kV/132kV step-change transformer.
The brick enclosures are designed to reduce noise for surrounding properties, including the Education Centre. However, the temperature of the air inside each enclosure is higher than the ambient air because of the heat wastage from the transformers. Water flows through the header pipe to each brick enclosure, where it is warmed sufficiently and returned to the heat pumps, which are located in a dedicated plant room. The heat pump system feeds new wet radiator systems installed in the substation building and Education Centre, together with hot water for the substation building.
Combining intelligent system design with high efficiency products, this unique application has enabled Rook Services to install renewable heating where ground source heat pump collectors or air source heat pumps may not be viable. It recovers significant waste heat from the transformers to provide free heating for the substation building and Education Centre, contributing to National Grid’s overall CSR strategy. The system is expected to pay back in less than nine years.
Nick Richards from Rook Services said: “We were already working in partnership with National Grid to deliver an ongoing programme of innovative Dimplex heat pump installations, designed to recover waste heat from its assets.
“After first patenting an idea to use waste heat from underground cables to provide space heating for adjacent buildings, Rook Services spotted an opportunity to apply this unique application to transformers at National Grid substations. Bishop’s Wood was the third installation to utilise Dimplex ground source heat pump technology for this application.
“The original requirement for this project was to provide cost-effective space and hot water heating for the main substation building. The building has a heating requirement of 73kW and the previous heating system had become inefficient and ineffective.
“However, it soon became clear that this installation could deliver additional benefits too, in the form of space heating for a neighbouring Environmental Education Centre.
“It’s a truly unique application, made possible by the high temperature and high performance features of the Dimplex ground source heat pumps – and one of which we were very proud to be a part of.”