Solar power station in the village of Govedartsi

Roman Rubanovich, NENCOM

In the autumn of 2018, the owner of a house in the village of Govedartsi (Samokov municipality) order us to build hybrid power station. Project goal — minimal dependence on electricity suppliers and constantly rising tariffs.

The power station have to use solar energy as a priority, and with its shortage — electricity from the grid. In case of an emergency grid failure, the power station must continue to operate on batteries.

Although the house is large, the roof is modest in size and has no southern slope. The most suitable southeast slope is partially occupied solar collectors and a chimney. Therefore, the customer expressed a desire to use the remaining roof area as efficiently as possible. This requires photovoltaic modules with high efficiency, for example — Panasonic Solar 330 Wp with a 19.7% efficiency and low temperature power factor.

After analyzing the initial data, we developed a 3D model of the location of solar modules on the roof of the house. It turned out that we can place 12 of these modules with a total capacity 3.96 kWp:

Then we simulated the operation of the power station taking the insolation and climate in this region, as well as taking the azimuth and the angle of inclination of photovoltaic panels:

The forecast calculates all losses, including those associated with the heating of modules in the warm season and snow sticking in winter. In this regard, the mountainous regions are sometimes more effective than the flat ones due to the clean atmosphere and cool summers:

A week after coordinating the project with the customer, we started to work. To install solar panels on the roof, we used reliable aluminum structures, special cables with a large cross section, double insulation and UV protection, as well as high-quality Swiss connectors Stäubli.

As the «heart» of the whole system, we chose the legendary inverter-charger Victron Energy Quattro 5000. The feature of the Quattro model is that it has two AC inputs and two AC outputs.

Inputs can be used for two alternating current sources, for example for a public grid and the generator. And two outputs can be useful if all the loads need to be divided into «critical», which have to work constantly, and «non-critical», which have to work only if there is an external grid.

We divided Panasonic photovoltaic modules into 4 groups (string) of 3 modules and connected to the solar controller Victron Energy SmartSolar MPPT 250/70.

For energy storage, we installed four Victron Energy Super Cycle 230 A·h Lead Acid AGM batteries. We connected these 12-volt batteries in series to obtain 48 volts and to minimize the loss of energy in the cables. We also installed three balancers that balance the voltage between the batteries.

Victron Energy Super Cycle batteries allow up to 20% discharge, unlike the Deep Cycle series, which has a limit of up to 50%. Thus, the total battery power capacity is 11 kW·h, and useful capacity at discharge up to 20% — 8.8 kW·h.

In the door of the metal cabinet with the equipment, we installed a monitoring system with a color display and connecting to a free portal to collect statistics and remotely monitor all parameters.

We have updated the software of all components of the power system to the latest version and configured the system according to the wishes of the customer.

After starting up the power system, we checked all the components and connections using a thermal imager and made sure that everything was working properly.

As usual, we shot a short video about our work:

One month later, we doubled the capacity of the energy storage system at the request of the customer. Now the useful capacity is 17.6 kW·h.

At the same time, we cleaned the solar panels from the snow and just had a good time in the mountains.