Following his recent investment in a new turnkey greenhouse (See references), Chris Durnford has become the first UK grower to have an operational heat pump.
Red Roofs Nursery has 6 compartments with 2 separate buffer systems which until now have been heated by a single boiler and CHP. The CHP was the nursery's primary energy source, with the boiler only required as a backup and during occasional periods of high heat demand. Now, to reduce the nursery's dependence on gas and encouraged by the very attractive heat pump subsidy available through the RHI, a 750 kW heat pump has also been installed.
Installing a heat pump is not something to be taken lightly, as the initial investment is considerable and integration of a heat pump into an existing modern heating system requires a lot of experience and know-how. In this case the heat pump expertise was provided by Certhon, who have installed a number of heat pumps in greenhouses around the world, and by CMW - who ensured that the control was properly integrated into the Priva heat management system.
- Always to have enough heat available to satisfy the demand from all the greenhouses
- Both buffers are open systems (no isolation valves), so the buffers must never empty completely
- To have enough spare capacity in the buffers to ensure the CHP can run throughout the day to produce sufficient CO2 without destroying heat. (The buffers must be at their minimum fill level at the start of the day)
- Use the heat pump as the primary heat source after the CHP
- Block operation of the heat pump from 16.00 to 19.30 when the electricity cost is uneconomic
- As far as possible, operate the boiler for CO2 only
- Maximise RHI revenue
Achieving these objectives is only possible because of bespoke software, written for the Priva climate computer by Gordon Badham of CMW, which communicates with the software in the heat pump. As the ground water source is common to both the heat pump and the irrigation system, part of the bespoke programming ensures that the levels in the irrigation water tanks are maintained at the desired levels whilst maximising the heat production from the heat pump.