By Richard Batty

In countries which offer feed-in tariffs for renewable energy, farmers have discovered photovoltaics as a welcome additional source of income. Compared with other energy sources, it can be used flexibly and easily, with minimum impact on the environment. It doesn’t harm the environment, makes no noise, is hardly visible and does not compete with food production. The yields can be easily calculated and little maintenance is required.

To offer English farmers suitable technology at a fair price, the Mole Valley Farmers Cooperative, which has more than 30,000 members, has added photovoltaic systems to its range of products. Concepts and components were assessed and tested in order to assemble a suitable system. The cooperative was not just looking for value for money, though. Above all, it wanted to make sure that the cooperative’s members would be able to make a well-founded decision and receive products to bring high yields reliably and over a long time.

A farm PV installation system consists of the same components as any other solar power system. Tailoring the system to the needs of farmers still requires more than just choosing the best components and mounting them onto a suitable roof. For one, the environment has to be taken into account: dust and moisture are everywhere on a farm. Finding sufficient surface area, however, is rarely a problem. A system should, therefore, be installed in such a position that it generates the highest possible yields, and is easily and safely accessible for cleaning.

Mole Valley Cooperative based its selection on these requirements among others. The chosen components were then tested under real-life conditions. The selection of the inverter provider soon led the cooperative to Mastervolt, a Dutch manufacturer. Their CS transformerless inverters were chosen due to their high yield and flexibility, with a wide input voltage range of up to 1,000 V. The low own-consumption of just 5-10 W is an additional bonus because the devices start particularly early in the morning and remain active until late evening.

The deciding factor was the specific experience of the Amsterdam-based development department. For more than 20 years, Mastervolt engineers have been developing power supply units for yachts. The company is one of the world’s market leaders in this area of the industry.  The cooperative concluded that someone who is able to develop systems which work reliably for many years in hot and humid engine rooms on board ships should also be able to supply farmers with resistant technology.

In order to guarantee a long-term, economically stable relationship, Mole Valley also prefers to work with European suppliers who would also be easier to contact in case of any warrantee issues. This was another argument in favor of Mastervolt and Norwegian module supplier REC. The same applies to the installers recommended to the members. In addition to experience with agricultural facilities, installers also have to have their heart in it and must have been working in PV before the successful feed-in tariffs were introduced in England.

Two Sunmaster XL 10 inverters and two CS 15 with 10 kW and 15 kW output respectively were chosen for the test field on the farm of the cooperative’s director. Both unit types have adaptive cooling to ensure safe operation even at high temperatures. Another deciding factor was the fact that the Mastervolt inverters, in combination with their data logger solution, were able to deliver all necessary yield data for evaluation by Mole Valley.

In terms of substructure, Mole Valley chose an unusual solution, opting for a ground-mounted installation as a standard solution. This ensures ideal module cooling and thus higher yields, while making cleaning easier and safer by not requiring staff to climb onto roofs. Ground-mounting also made tracking possible. Even though automatic trackers were also tested, they will only be employed where customers request them explicitly. This is because when systems are used under harsh environmental conditions for many years, this may lead to increased maintenance, which would overshadow the increased yields produced thanks to the tracking system.

In order to benefit from the advantages of tracking without having to live with the disadvantages, the internal design department at Mole Valley simply came up with a manual system, which allows adapting the inclination in several steps, using a simple and robust design with a crank. A substructure for the 10 kWp standard system can be adapted to the changing seasons by one person. Farmers planning to install more than 10 kWp can order several system packages. This is independent of the type of substructure used. In the testing period between October and March, a system with a manual tracker generated eleven percent more yield than a rigid system. Although this value will be evened out over the summer months, Mole Valley expects the system to generate several percent of additional yield each year. Since adapting the substructure incurs relatively low additional costs and can be done in a matter of minutes, this is a particularly worthwhile investment.

Richard Batty is managing the sales and marketing activities for Mastervolt UK (www.mastervolt.com). He holds a BSc in Engineering from the University of Birmingham and an MBA from City University, London. During the past 20 years, he has worked for a number of high technology companies in Europe in technical, product and business development roles. Batty is personally technically qualified to design solar PV systems including MCS accreditation.