The growth of ground-source for the greenhouse industry

Gillian Hogarth explains how Drilcorp’s specialist Geotechnical Exploration Division, which looks after geothermal energy boreholes, can help fruit and vegetable producers in the UK be more efficient with their energy consumption
The growth of ground-source for the greenhouse industry The growth of ground-source for the greenhouse industry The growth of ground-source for the greenhouse industry The growth of ground-source for the greenhouse industry The growth of ground-source for the greenhouse industry

Boreholes have long been used to irrigate produce grown in glasshouses now they are increasingly being used for heat generation too

With the costs to import fruit and veg increasing and Brexit (still) on the horizon, the industry has seen an increase in the growing of these foods in Britain. However, the costs of energy to heat greenhouses across 400 acres of land can be astronomical. Yet the growth of green energy has also seen an increase with the use of open and closed loop ground-source heating systems potentially offering a solution.

Farms are struggling with extreme droughts and rising water costs. Climate change and droughts have reduced the available surface water flowing from mountain ranges to irrigate crops. Farmers have had to resort to pumping water from underground aquifers.

Finding a sustainable solution is also a long-term consideration and has both environmental and economic impacts for any business. Sustainability does not mean that we should not use the natural resources that we have such as the soil, water and energy which are finite but rather that we use them responsibly and wisely.

Agriculture is the largest global consumer of freshwater. The term ‘water footprint' measures the volume of evapotranspiration (ET) or water use of a crop per unit mass of yield. To produce 1kg of fruit and vegetables water is needed in vast amounts. Olives use 4,400L while bananas use 800, apples 700 and lettuce 130L.

By using the latest technology and recycling water, oxygen, carbon dioxide, and nutrients growers are able to encourage the growth of high-quality fruit without causing major damage to the environment.

Investing in a borehole can be a long-term solution

Irrigation is perhaps one of the most important factors in growing and the cost of a mains supply for such an intensive operation can be enormous. Investing in a borehole can be a long-term solution and most farmers and growers find that it pays for itself within a few years.

Geothermal energy for greenhouse heating has been common practice for nearly 100 years but ground-source heating has seen an increase in recent years. The source is basically thermal water with temperatures between 40°C and 80°C. Ground-source can be used for both heating and cooling and therefore can meet the demand of keeping a constant temperature in winter and cooling in summer.

Drilcorp has over 27 years of experience in the borehole drilling sector and has a specialist Geotechnical Exploration Division which looks after geothermal energy boreholes.

Ground-source heat pumps use different heat sources such as solid, liquid or gas. The most popular are using groundwater from a nearby aquifer. The temperature produced is nearly constant all year round at around 11°. These systems need both a production well and a re-injection well.

Ground-source heat pumps (GSHPs) use pipes that are buried in the land to extract heat from the ground. A ground-source heat pump circulates a mixture of water and antifreeze around a loop of pipe, called a ground loop, which is buried in the surrounding land. Heat from the ground is absorbed into the fluid and then passes through a heat exchanger into the heat pump. The ground stays at a fairly constant temperature under the surface, so the heat pump can be used throughout the year. The loop can be horizontal or vertical. Deep vertical boreholes can draw more heat from the ground.

This type of system uses well or surface body water as the heat exchange fluid that circulates directly through the GSHP system. Once it has circulated through the system, the water returns to the ground through the well, a recharge well, or surface discharge. This option is obviously practical only where there is an adequate supply of relatively clean water, and all regulations regarding groundwater discharge are met.

A borehole can also be used as a water source for irrigation and can be connected to a drip irrigation system. 20,000L per day can be extracted without the need for a licence from the Environment Agency and Drilcorp can assist with all licencing requirements.