Off grid solution, a real case

Our private customer is convinced. His house has been equipped with solar panels and he owns an electric vehicle. Nevertheless, the energy prices are always increasing. The customer would like to purchase an off grid installation and asks the YouPower team to undertake a study, with the following guiding principles:

• Existing solar panel installation, 10 kWp power
• Immediate use of as much solar energy as possible
• Use of the battery in the dark hours of the day and in the evening
• The power consumption is 16,000 kWh per year. This is quite a lot for a family, but the recharging of the electric vehicle is also included.
• The customer has a connection to the natural gas network

Our customer also wants to get an idea of the off grid installation’s cost recovery installatie. On that matter, the remaining life of the solar panels, which is approximately 14 years at this moment, has a decisive role. Our plan is to do better than that.

According to Fluvius*

*Fluvius is the Flemish electricity and natural gas provider. This installation is a so-called parallel system, whereby one is not disconnected from the grid. The battery installation is independent of the prosumer redress. A production installation with a maximum AC power of 10 kVA, possibly combined with a battery and equipped with a meter running backwards, still falls under the prosumer rate system. This rate is paid for (the sum of) the power of the inverters to which a production installation is connected. Only by going off grid, this prosumer rate can be avoided.

There are no regulations concerning the installation of an off grid system. One is completely free to size this independent installation.

Extra added value when going off the grid

Companies or families that are in a secluded location or that are forced to provide usually expensive connections because of their distance to the street, can have an additional advantage by going off the grid. And this counts even more for agricultural companies.

Customer’s individual power consumption

The annual consumption is 16,000 kWh. We spread this consumption over a full year, according to the table below, based on measurements per quarter.

Energy yield of solar panels

The Flemish independent authority of the energy market (VREG) can provide these data. The consumption during the summer months is lower than in the winter months. And the energy yield of the solar panels is larger in spring and summer, since the sun shines more in those months. We consider this information when choosing a battery system. This is represented in the table below.

This yield profile is independent of the installed installation power, in kWp. We start from this synthetic load profile to make our calculations, and as such, we take the annual spread of the consumption into account.

To measure is to know

The customer is connected to the natural gas network. The off grid installation can be equipped with an emergency generator running on natural gas.The solar panels remain the primary energy source. Surplus energy is stored in the batteries and released when required. The emergency generator helps in case of a shortage of energy during peak moments.

YouPower measures the actual and the peak consumption over a given period. This allows us to size all of it, from emergency generator to battery, inverters and cables. With these measurements we obtain a chart, similar to the one pictured below. This applies to a particular day scenario. The hourly yield depends on the season, yet the principle remains the same.

Yellow: immediate consumption
Blue: storage, or consumption through the battery
Orange: power supply by emergency generator

Solar panels – avoid a grid study

Currently, 10 kWp of power is available. If the customer wishes to extend the installation to meet the current electricity consumption of 16,000 kWh, and also to remain connected to the grid, he will be obliged to carry out a grid study, and he will have to install additional elements such as a disconnection panel and a four quadrant energy meter. An off grid installation easily saves you between 10,000 and 20,000 EUR.

Inverter and battery charger

Thanks to the Victron inverters, the cheapest energy is used at the right time. After all, our software makes sure that the battery charges and releases energy. Individual settings and parameters can be used for every separate project. For instance, in the event of a larger energy consumption at night, the charging of the electric vehicle slows down. By using the applications, the customer can simply follow the consumption in real time.

Why Victron Quattro?

The Belgian federation for electricity and natural gas grid operators Synergrid approved Victron Quattro for usage in a parallel system (wherein one remains connected to the public power grid). As soon as one goes off the grid, this won’t make any difference, but this inverter thus has the label.

The main output of the Victron Quattro 48/8000/110-100/100 is a UPS. This way, the entire Battery Management System (BMS) remains active in case power failure. In that case, the UPS takes over the supply of the connected load. This is done very quickly (less than 20 milliseconds) so all equipment remains in operation. An additional second output enables the possible connection of other elements that are preferably not charged through the battery, but are supplied directly through AC voltage at the moment it is available, for instance when the emergency generator is active.

The power supply in the house is 3 x 400 V. YouPower installs 3 inverters, one for each stage. The Quattro inverter can be installed in both autonomous and PV systems connected to the grid, and also together with other alternative energy systems to enable a future extension.

Compatible batteries coupled in parallel

Lithium-Ion Pylontech US2000B is the safest of all Li-ion batteries, and can deal with high discharge currents. The nominal voltage per cell is 3.2 V. Lithium is much more energy efficient than lead acid. There is a 10 year warranty on 80% of the capacity. The capacity of the battery group is 14.4 kWh, six 2.4 kWh cells, and to be put together in a 19” rack.

Each battery module has a CAN BUS RJ45 connection, for communication. The batteries are connected in parallel, and linked through power cabling. The working voltage is 48V and is in function of the customer, namely 50 Ah. We assume a continuous flow of 25 A up to a peak flow of 100 A, during 1 minute. Each separate module communicates by means of the CAN bus.

Battery Management system

The chosen Li-ion battery has a built-in BMS system that manages voltage, current and temperature. The BMS system intervenes in case of an excessive charging current, a tension too high and large temperature fluctuations. At the same time, the BMS system brings the right balance between charging and discharging current, which significantly lengthens the battery life.

The following BMS functions are included

Flexibility is key

A nice thing about this kind of system is that it’s always possible to extend. From the start of each project, YouPower thinks of a possible future extension, and makes sure that all elements of the system, such as inverters, cables and type of devices are sufficiently sized for future use.

Safety first at YouPower

Battery installation

The location of the battery should meet the following qualifications:

• Watertight location
• Stable and level floor
• No explosives or flammable materials nearby
• Room temperature between 0°C and 50°C
• Constant temperature and humidity
• Minimal dust quantity
• Min. 2 m from a heath source
• Min. 0.5 m from a ventilation inverter
• Do not cover the battery
• Keep children and pets away from the installation
• Mandatory ventilation of the space
• In case the required temperatures are not observed, the battery switches off automatically