ONE of the lesser discussed forms of renewable energy is 'ground source' heating, perhaps because, by its very nature, its not in the slightest bit visible to passers-by.

Unlike its horizon-hogging cousins, the wind turbines, or the rooftop rash of solar panels, a ground sourcing network is literally buried out of sight – coils of pipe under a large area, gathering the heat held in the soil, and bringing it back to a Ground Source Heat Pump, that will concentrate the few degrees of temperature rise contained in a constant flow of liquid not unlike anti-freeze into a large temperature rise in a water vessel.

Capturing this environmental heat just takes a little electricity to run the pump, and qualifies for the Government tariff on renewable heat, for seven years in a domestic energy system, and for 20 years if its commercial system.

One company which has specialised in this low-key technology is Durham's Calibrate Energy Engineering. Installing commercial heat pump systems for 12 years, Calibrate was recognised at the 2018 Highland Show with the Silver Innovation Award for its ‘Heat pump grain drier’ system, which has been installed on a number of farms. It was also named as one of the UK Top 16 Emerging Engineering Companies for the Renewables sector as part of the 2017 Parliamentary review presented in the Houses of Parliament.

Calibrate has developed a 'modulised plantroom' solution suitable for agricultural heating and chilling requirements, like grain drying, dairying or potato storage –the heat pump system for each application is designed to manage the particular process, and manufactured in its workshops and delivered to site ready for installation and use.

The computer brain behind each systems is a version of the company's own bespoke controller, which can operate the installation via a cloud-based system, enabling Calibrate to monitor all aspects of the process and tariff generation meters online.

For example, a Heat Pump Grain Drying system concentrates the circulating ground heat with a 350% efficient heat pump, whilst earning the 20-year Government RHI tariff, and producing the useful ‘free’ by-product of chilled water, which can be used elsewhere on the farm, to dehumidify the recirculated air through the grain as well as chilling the grain to anywhere between 10 degrees C to 15 degrees C below ambient.

Calibrate describes its systems as 'hugely flexible', allowing for the energy generated to run various parts of the farming business. For example, whilst one array can run the grain drying process, another array from the heat pump can service a farmhouse, and two cottages.

On a dairy farm, the system can be formatted to provide both hot water and chilling. The heat from the ground is again increased with a 350% efficient heat pump, and the by-product of the heat pump’s heating cycle is again chilled water. This is used to chill the milk through a one pass plate exchanger bringing the milk from 18°C to 3.5°C. Using this system, the milk is at storage temperature less than five minutes after leaving the cow – a normally costly process achieved for free using the heating by-product. This system is independent from an existing refrigeration system, giving 100% back up.

“We offer our clients a 20-year warranty package ensuring there are no surprises or hidden costs with our technology,” said MD Shane McDonald. "If you have a grain dryer, potato store, or dairy farm it is worth looking more closely at the options that Calibrate can offer you."

The company is located in rural Northumberland, but has clients all over the UK who are happy for prospective purchasers of this equipment to visit their sites and see their renewable projects up and running and see the savings and income generation figures that back the confidence in the systems.