Heat is extracted from nearby wastewater treatment plants and transferred in a closed loop system to the heat pumps located at the greenhouses. Electricity for the ground source heat pumps is provided by the grid and Combined Heat and Power units. Such ‘CHPs’ have the added benefits of providing waste heat which further supplements the greenhouse heating and providing carbon dioxide to enrich the atmosphere inside the greenhouse to encourage plant growth.
The systems will constitute the highest installed capacity of heat pump technology so far in the UK’s agritech sector, capable of generating a combined total of 70MW peak of thermal power. The system will also result in the treated water outflows from the recycling centres being cooled sufficiently before they are released back into the river to protect local ecosystems.
A heat plate exchanger is used to extract heat from the discharge - 1,000L.s-1 at Norwich and 550L.s-1 at Bury St Edmunds - taking between 3K and 6K out of the water. Both greenhouse sites are located around 2.4km from their respective water treatment centres.
The heat plate exchanger system extracts the heat energy using a water and Thermox DTX (heat transfer fluid) based system. A closed circuit then takes the heat transfer fluid directly up to the heat pumps. Specifically employed for the system, Hydratech’s Thermox DTX is a high efficiency, non-toxic geothermal heat transfer fluid with antifreeze function, for use in geothermal, GSHP & air source heat recovery systems.
The carbon footprint of the food produced at the sites is expected to be 75% lower than equivalent European greenhouses, and 10 times more productive than field farming. The East Anglian sustainability projects demonstrate how renewable heating systems, and heat pumps in particular can be deployed on a commercial scale.
Industry proven to maximise heat recovery, reduce maintenance and lower running costs, Thermox DTX is specified by the UK’s largest heat pump contractors, installers and designers. It has been commissioned in thousands of commercial and domestic heat pump systems by industry leaders such as Kensa, Nu-Heat and Ideal.