Delta inverters drive German farm’s solar power-sharing system

Business news | February 20, 2020

By Nick Flaherty

GreenRock Energy has used inverters from Delta Electronics for a 2MWp commercial solar rooftop project in Thuringia, Germany. It also uses a lithium iron phosphate battery storage system with a capacity of 242kWh.

GreenRock installed the 2MW of photovoltaic (PV) solar capacity on the roofs of three agricultural buildings at a pig farm in Remda, between Jena and Weimar in Thuringia, Germany. From the end of 2019, two of the PV plants will feed electricity back into the grid at a fixed contractual price and the third plant will be used by the farmer. The size of the plants, 750 kWp x 2 for the grid feed-in and 500 kWp for the self-consumption, was deliberately chosen.

6,000 square metres of roof surface had to be completely renovated and freed of asbestos so that the structural insulated panels could be installed to hold the solar PV system. The three buildings were equipped with 7,500 polycrystalline solar modules, which came directly from the company’s subsidiary Greenrock Trina. Each of the Trina Honey modules supplies 275W from 60 cells. The assembly system for the solar modules consists of trapezoidal sheets and a substructure of 180mm aluminium rails supplied by the German company, Saytec.

The installation also includes 32 string inverters from Delta Electronics. These inverters had three different power classes to take the special features of each roof into account and make optimum use of the roof surface.

The M88H inverter was specially developed for use in large solar parks and is available in two connection variants. It has a maximum efficiency of 98.5 per cent and weighs 84kg. The terminal box with AC and DC surge arresters, terminals and DC disconnectors is already integrated into the device and can easily be disconnected from the power module. When the power module is replaced, the junction box with the entire cabling remains at the installation site, saving time and reducing maintenance and repair costs.

“The M88H has one of the highest power outputs and is one of the most efficient string inverters on the market and ideal for large PV systems,” said Martin Kofler, CEO of GreenRock Energy.

While two PV plants feed the electricity produced into the grid, the owner decided to use the third PV plant for self-consumption. The resulting 500,000kWh of energy is buffered in lithium batteries with a capacity of around 242kWh. This was installed under consideration of the agricultural environment as well as the climatic conditions. Soltaro’s lithium iron phosphate storage system uses an efficient high voltage of 1,000 volts DC and is controlled via the energy management system from Smart 1 Solutions. The system optimizes energy distribution for private consumption and grid feed-in.

The owner of the PV plant receives electricity at a fixed price, which is ten percent below the tariff that the owner has paid to an energy supplier at the time a contract was concluded. The fixed price is valid for 20 years. The Remda project is the first reference project for GreenRock Energy to implement a rental electricity model that includes relatively large battery storage with 225 kilowatts of power. GreenRock Energy calls this model s-plus. “Our idea is that as many people as possible can benefit from the advantages of a photovoltaic system without having to make investments,” said Kofler. This gives customers planning security for 20 years through a fixed electricity price. From the 21st year, they will also receive a share of the plant’s income.

This is a new approach in Germany that has a great deal of potential for ensuring that photovoltaic systems are increasingly built, irrespective of the requirements of the EEG (Erneuerbare-Energien-Gesetz, the renewable energy law in Germany), he says.

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