Solar power station in Varna #1

In April 2019 a young family from Varna commissioned us to build hybrid solar power station for their home. We inspected the place and prepared two projects.

The first project provides partial autonomy and the second — complete independence from the public grid. The couple chose the first option, as the best.

When designing solar plants, we use specialized software that allows us to combine satellite images, client drawings and 3D modeling.

The program takes into account the make, model, inclination and azimuth of the solar modules, as well as climate data for the area and other factors to simulate the operation of the future power station.

We determine the shade of trees and other objects for each day and time of year, and we take this into account when arranging the solar modules.

For the implementation of the project we used only the southwest slope of the roof, we put on it 15 photovoltaic modules Trina Solar with power of 275 Wp each. The total installed capacity of solar panels is 4 125 Wp.

At the same time as the roof work, we installed an inverter, batteries, controller and other power station equipment in the technical room. Hybrid solar power station must be able to work at the same time with photovoltaic modules, batteries and external grid.

For converting DC voltage from solar modules and batteries to AC voltage as standard, we installed inverter Victron Energy Quattro 8000.

Like other hybrid inverters from the Netherland company Victron, this model has a built-in battery charger to power the batteries from the public grid if needed.

Eight 12-volt Victron Energy AGM Super Cycle batteries with a capacity of 230 A·h each are used to store solar energy. We connected them in two consecutive series of 4 each to get a voltage of 48 volts.

Super Cycle batteries allow a deep discharge of up to 20%. Thus, the total useful storage capacity is 17.6 kW·h.

For transfering energy from the solar modules to the inverter and the batteries we use high efficient controller Victron Energy SmartSolar MPPT 250/85.

We have also installed battery balansers and a Venus GX device for remote monitoring and statistics collection. Through this device, the station is connected to a free VRM portal, which can view the history of energy production and consumption by sorting by month, week, day or hour.

Thanks to the statistics we know that the station operates in full autonomous mode all summer long. From the time the power station was launched in April to the time this article was written in August, only 7% of total energy consumed was from the grid. And mainly not because there was not enough solar power, but because of testing all the functions of the system.

It is important to note that all the equipment in the house works only on electricity, and the owners of the house do not save energy and refuse anything for themselves. For heating water use electric water heater with capacity 3 kW, for cooking — electrical oven, for cooling — air conditioners. Also in the house are constantly used washing machine, big TV, refrigerator, electrical tools and many more.

The graph clearly shows that consumption «From Solar» is more than «From Battery». This means that customers follow our recommendations. It is always advisable to maximize the use of solar energy directly rather than via batteries.

First, when the sun is shining but the batteries are already fully charged and most appliances are off, the power plant «is forced» to reduce its power to the level of consumption, and we do not receive from it all that it is capable of.

Second, with the cycle «charge-discharge» significant energy losses occur and battery life is reduced. That is why during the day it is very useful to start a washing machine and a vacuum cleaner, to heat water in the water heater, to iron, to prepare food and so on.

The other graph shows that overnight batteries rarely discharge up to 65%, and in most cases — till 75-80%.

This means that not only all summer but also part of the autumn, the station can operate in full autonomous mode without connecting to a public grid.

In addition to detailed statistics, the VRM portal allows the power station to be monitored in real time and to change its settings from anywhere in the world.

An example of real-time monitoring

On the darkest days, the power station produces about 8% of its peak power — about 330 watts. This is quite sufficient for the simultaneous operation of a refrigerator, TV and charge battery.

After the equipment was installed, we updated the software of all components to the latest versions and set up the power station taking into account the wishes of the contracting authorities.

Setting up the remote monitoring system

All cables are hided in corrugations and cable ducts to ensure safety and a pleasant appearance. We provided the necessary schematics, instructions and training to our clients.

Traditionally, we shot a short video about the construction of this power station: