Background:

Low Carbon Farming’s mega-greenhouse projects in Norfolk and Suffolk are a world-first for renewable heating. The turn-key heat pump project, capable of producing 12% of the UK’s tomatoes has 70 acres of greenhouse growing space, five times more glass than the Shard, and over 10km of underground pipeline.

Solution:

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.

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™ (Hydratech Glycol) based system. A closed circuit then takes the heat transfer fluid directly up to the heat pumps. Specifically employed for the system, 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 total Thermox DTX™ mixture of over 1.5M litres was delivered to the two associated Energy Centres in Norwich and Bury St. Edmunds over a period of four weeks, then pumped over from road tankers into the respective pipelines by Hydratech Services engineers.

The systems 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 also cools the treated water outflows from the recycling centres, before they are released back into the river, to protect local ecosystems.

Key Takeaways:

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.

Since 2010 more than 6,670,000 litres of Thermox DTX™ concentrate has been supplied to 500-plus customers, for use in renewable energy installations. At an average mixture ratio of 1:3 (25% v/v) this equates to a Total System Volume in excess of 26,680,000 litres.

To complement and support all heat transfer fluid (HTF) products, Hydratech can provide a full range of technical services. These extend from over-the-phone consultancy on fluid selection, through to a hands-on Fluid Management Service, incorporating flushing and conditioning of systems, filling with HTF and long-term monitoring and maintenance.