Electricity for sheep

In December 2019, we were contacted by farmers from the village of Zlatna niva, Shoumen district. Modern agriculture is impossible without electricity, but connection to a common electricity grid costs about 20 thousand leva and takes more than a year. And then it is paid for every kilowatt-hour.

A reasonable solution to the problem is building a solar power plant of our own. We were told that it was necessary to provide energy for a single-phase sheep milking machine, milk cooling bath and the household needs of farm staff. According to the given budget of 14 thousand leva, we have proposed the optimal configuration.

Monocrystalline solar modules Jinko Solar JKM320M-60 with a power of 320 Wp each, convert the solar energy into electrical energy. These nine modules under ideal conditions will provide a power of 2.88 kW. On darkest days (for example, during rain) solar power plants typically produce 5-15% of the peak power of installed modules. In our case, this means 140-430 watts.

Photovoltaic power is supplied through special PV cables to the Victron Energy controller BlueSolar MPPT 150/45-Tr. The controller performs several tasks at once. First, it lowers the voltage of the solar modules (about 110 volts) to the level needed for battery charging. Second, it constantly adjusts the input voltage for optimum performance of the solar modules, depending on their irradiation. Third, the controller adjusts the output voltage and current depending on the charge level and the temperature of the batteries, ensuring their longevity.

Simple scheme of the plant

Energy is stored in four 12-volt Victron Energy AGM Super Cycle Lead-Acid batteries with a capacity of 170 A·h each. They are connected in series, forming a rated voltage of 48 volts. The Super Cycle batteries can be discharged up to 80%, so the useful energy reserve will be 170×48×0.8=6.5 kW·h. Practically, taking the losses into account, it means that fully charged batteries can provide us with 1 kW power for 6 hours in the dark part of the day or with 500 W for 12 hours.

Victron Energy inverter MultiPlus-II 48/3000/35-32 GX converts the DC voltage from the controller and the batteries into 230 volts AC. It can also operate in charger mode when a generator is in use. The rated power of the inverter is 2.4 kW. The GX letters in the modification name mean that the inverter has an integrated remote monitoring system.

Power plants assembly at NENCOM

In order to save money, the client independently installed a supporting structure for the solar modules in accordance with our recommendations and drawings. We recommended him to make an angle of 45° and orient the entire structure just south.

We mounted special aluminum profiles on the finished structure and attached photovoltaic modules to them.

The actual inclination of the solar panels was almost 50°, which will have a positive effect on energy production in winter when the sun does not rise too high above the horizon.

We installed electronics and batteries in a construction trailer, leaving an advance on the length of the cables. This equipment shall be moved later to new premises.

All electronic are housed in a NENCOM company box, which provides additional protection and accelerates the installation of equipment in the facility.

NENCOM box

Equipment inside the box

The balancers equalize the battery charge

The real cost of this project in December 2019 is 13 970 BGN (7 142 €) including delivery, installation and VAT. The prices for solar power plant equipment are gradually decreasing, so in future such a system may cost a little less or provide more energy for the same money.

Project video