Heat Pumps Today

20 Use of heat pumps in agriculture is growing. We report on two recent projects that harness heat from aquifers for drying high quality animal feed. Premium Feed Drying Facilities are Powered by Ground Source Heat Pumps Heating accounts for around 40% of the total energy used in agriculture, representing some 7,497GWh of heating input. The need for heating di ers significantly between di erent types of farming. Broadly, however, around half of agriculture's heating requirement is for supporting crops in covered growing facilities, and the remainder shared between cereal drying and animal support. Importantly, the heating requirement in agriculture spans relatively low temperature ranges. This makes it ideal for the use of heat pumps, which operate most e‚ciently within modest temperature ranges. The further requirement for produce cooling alongside a heating capability on a farm can also help make economic sense of heat pump-based schemes. This is because combined cooling and heating projects can be designed to make optimum use of the total energy available, helping pay-back and further replacing use of expensive, high carbon grid energy with cheaper, low carbon renewable energy. Two recent large-scale agricultural ground-source heat pump (GSHP) projects demonstrate the e ectiveness of this approach for improving the e‚ciency of crop drying, as a means of both reducing costs and improving yields. The projects were carried out by OMNI Heat and Power Ltd using Carrier high e‚ciency heat pumps based on screw compressors. Stoke-on-Trent- based OMNI specialises in renewable heat and waste-to-energy solutions. In addition to heat pump projects, it has experience in Combined Heat and Power (CHP), anaerobic digestion, biomass, and gasification technologies. February | March 2022 I N S T A L L A T I O N S The first project employs 1.5MW of Carrier heat pumps to dry Lucerne hay, a premium feed in demand by UK racehorse breeders and trainers. The GSHP system was installed at a specialist hay-growing farm near Coventry. Lucerne is a high-quality feed that has a high protein content, which helps horses in training remain slim and fit while maintaining high energy levels. It is also rich in nutrients such as vitamins A, K, E, and calcium. It is such a rich food source that it is often given as a supplement rather than a whole feed. The heat pump-based hay drying facility is designed to ensure full drying throughout bales of cut Lucerne hay, to minimise spoilage and ensure the highest possible yields for the grower. Installed with support under the Renewable Heat Incentive (RHI) scheme, the facility uses two Carrier AquaForce® 30XWHV water-source variable-speed screw heat pumps to upgrade energy extracted from a series of boreholes, which tap an underground aquifer beneath the farm. The Carrier heat pumps upgrade the water temperature from 0°C from the boreholes to 35°C exiting the system. It is then used to evenly and consistently dry the Lucerne hay bales, which are spread out on specially designed drying floors. To further enhance e‚ciency, the heat pumps are equipped with Carrier’s Greenspeed® intelligence inverter drive and control system, which matches the speed of the compressor to the current load. This optimises performance, reduces energy use, cuts carbon emissions, and minimizes running costs for customers. Project 1