AHDB News Summer 2018

FOR THE HORTICULTURAL INDUSTRY GrowSave News Summer 2018 Since autumn last year, we have seen and heard about an increasing number of heat pump projects in horticulture. Ground and water source heat pumps are still incentivised highly in the RHI scheme. Growers with an interest in establishing such a project are urged to act now, because of the length of time it can take to establish a project and the prospect of the RHI ending in 2020. Historically, uptake of heat pumps has been slow. They are often perceived as complex, although that really isn’t the case. In fact, most of us have a heat pump in our homes, in the form of a refrigerator. The principle is to extract heat from a low grade (i.e. low temperature) heat source and, through a process of mechanical work (evaporation followed by condensation), raise the temperature before extracting the heat for a useful purpose. Before installing a heat pump, some careful consideration is required. It is important to identify where the heat will come from. If using the ground, do you have sufficient area for a horizontal ground loop, or will you need to drill expensive boreholes? Alternatively, do you have access to a suitable water source, such as an aquifer, river or lake? Often, the return water cannot be disposed of with drain water, so consider whether you can use it yourself, or what else you might do with it. Bear in mind also that usable heat is output at around 55°C, although a well-designed heat distribution network can still extract sufficient thermal energy for horticultural applications. Another thing to remember is that heat pumps require electricity to operate. Typically, for 1kWh of electricity input, 3-5kWh of heat is output, but make sure that you have an adequate import connection from the grid to provide the necessary power. Alternatively, a Combined Heat and Power (CHP) plant could provide electricity. If designing a system from scratch, the CHP and heat pump can be sized to complement each other in terms of electric output, input and total heat requirement. If you are still unconvinced about heat pumps, consider that they are low maintenance, require less management than a boiler, and make use of a sustainable heat source. In the run-up to the end of the RHI scheme, we expect to see and be involved in many more heat pump installations for horticultural applications. Here at GrowSave, we have published a number of technical articles and information about applications of heat pumps in horticulture, which can be found at www.growsave.co.uk . www.growsave.co.uk/flipbook/nov- 2015/# www.growsave.co.uk/userFiles/24__ heat_pumps_what_are_they_and_ how_do_they_work.pdf www.growsave.co.uk/userFiles/25__ heat_pumps_the_practicalities.pdf Heat Pumps in Horticulture Ed Hardy