WASTE HEAT RECOVERY WITH DIMPLEX HEAT PUMPS
Two Dimplex ground source heat pumps are central to an innovative renewable heating solution which uses waste heat from transformers at a major National Grid substation to provide space and hot water heating for two adjacent buildings.
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 innovative solution, which has been designed and patented by Rook Services as part of National Grid’s commitment to reduce carbon footprint, has been installed at Bishops Wood Centre near Stourport.
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 Service 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 and commitment to reduce carbon footprint. The system is expected to pay back in less than nine years.