Battery storage systems

How does a battery storage system work?

In principle, a photovoltaic battery storage system works in the same way as your smartphone’s battery. At its heart is a powerful lithium-ion battery that stores electricity and discharges it when needed. The key difference is that your battery storage system is not charged with electricity from the mains socket but instead with the solar electricity produced by your photovoltaic system. Whenever the solar power system on your roof produces more electricity than is being consumed in your home at that time, the surplus electricity flows into the battery storage device. You can then use this electricity when it’s dark outside or when your PV system is generating less electricity due to adverse weather conditions. This allows you to power your home with self-generated electricity, whatever the weather or time of day.

Why is installing a battery storage system worthwhile?

Combining a photovoltaic system and a solar battery storage system enables you become more independent of external power suppliers and reduce your exposure to volatile electricity prices. It helps you to use more of the solar-powered electricity you generate as opposed to feeding it into the public grid at low prices and then buying any additional electricity you need at higher rates. At the same time, you’ll be making your contribution to the energy transition and reducing CO₂ emissions.

A battery storage system with integrated inverter

If you already have a solar power system, you probably already have an inverter. Our storage solutions for retrofitting projects, such as the SENEC.Home V2.1, are compatible with most inverters on the market. However, we also offer battery storage systems with integrated inverters, such as the SENEC.Home V3 hybrid, which is an ideal choice for new system installations. This saves the costs of buying an additional inverter and having it installed.

Independent power supplies are on trend

Demand for independent power supplies is rising – and with good reason! For one thing, more people are becoming aware of the need for sustainability and systematic climate protection. In addition, consumers are looking to reduce their dependence on energy suppliers and minimise their exposure to volatile electricity prices. New technologies are making battery storage system solutions increasingly affordable. It is also interesting to note that operators of PV systems that feed electricity into the grid are looking for ways to increase their use of self-generated electricity. And, given that retrofitting existing systems with battery storage devices does not usually pose a problem, this too is constantly driving demand.

Buying a battery energy storage system: Points to remember

Almost all domestic energy storage systems on the market rely on lithium-ion technology, so the technical differences between them may not be immediately clear. One point worth asking about is storage capacity. In most cases, the storage capacity available for use will be less than the stated nominal capacity. SENEC is the only provide that guarantees 100% of capacity of its storage systems for the first ten years. So, from day one, 10 kilowatt-hours means 10 kilowatt-hours.

Checklist: What can a battery storage system do?

• Monitoring: Is there a function that allows you to see relevant KPIs such as electricity generation, charge level and supply rate?
• Energy management system (EMS): Are there smart functions that enable you to control how the storage system works, e.g. using data from weather forecasts?
• Installation: How much will it cost to install and how much space will the storage system need? Is it a floor-mounted or wall-mounted device?
• Connection to charging point: Can the battery storage system be combined with an EV charging point so that you can charge your car with solar-powered electricity?
• Connection to heat pump: Can you couple the battery storage system to your heat pump to heat your home with solar electricity?
• Smart Home integration: Can the battery storage system be integrated into Smart Home systems?
• Expandable: Does the manufacturer offer additional options and system components to expand your battery energy storage solution as you wish?

How long does it take to install a domestic photovoltaic storage system?

First of all, you will make an appointment for your specialist partner to visit your home. They will precisely plan the PV system and the storage device in accordance with your wishes. Following this appointment and a consultation meeting, they will give you a proposal. If you accept it, the process of actually installing a battery storage system is relatively swift.

How big should my battery storage system be?

Choosing a storage device with suitable capacity is a decisive factor in the cost effectiveness of your PV system. If the storage device is too small to cover your household’s daily needs, you will have to buy electricity from your energy supplier. If the storage device is too large, it will never be fully charged – and your surplus electricity will always flow into the storage device instead of being fed into the grid. If that happens, you will miss out on the feed-in tariff.

Determining your household’s electricity needs

What size storage device would be suitable for your household is primarily determined by two factors:

1. Your electricity usage (annual consumption in kilowatt-hours/kWh)
2. The size of your solar power system (capacity in kilowatt-peak/kWp)

The storage device should be able to cover your electricity needs in the evening and at night – i.e. over the period in which your PV system does not generate electricity. As a rule of thumb for a rough calculation, you can estimate that every 1,000 kWh of annual electricity consumption requires around 1 kWp of photovoltaic capacity or 1 kWh of storage capacity.

1,000 kWh annual household consumption = 1 kWp PV = 1 kWh battery capacity

You can roughly establish your annual household electricity consumption by looking at your annual statements for recent years. Your SENEC specialist partner will precisely calculate the size of storage device you need. They will provide detailed advice and recommend a SENEC storage device with storage capacity of either 2.5 kWh, 5 kWh, 7.5 kWh or 10 kWh.

Battery storage system capacity: Three examples

Smart charging options: Peak shaving and forecast-based charging

Solar power systems generate different amounts of electricity depending on the weather and time of day. Any solar electricity you do not use straight away is stored in your battery storage system or fed into the public grid. However, the German Renewable Energy Act (Erneuerbare-Energien-Gesetz – EEG) and subsidy programmes for battery storage systems set out by different federal states limit the proportion of solar electricity you can feed into the grid. SENEC battery storage systems offer smart management charge functions, giving you the option between peak shaving and forecast-based charging. This enables you to make the most efficient use of your solar-powered electricity and minimise the risk of your PV system being curtailed.

Peak shaving
Excess solar electricity is fed into the grid as a priority. Electricity is only fed into the storage system once the feed-in limit has been reached. Peak shaving processes can be scheduled.

Forecast-based charging
Charging of the storage device is controlled based on weather forecasts and system-specific generation and consumption data. This allows you to use and store as much of your self-generated solar electricity as possible.

Do I need to conclude an electricity contract for my battery storage system?

No, you can continue to purchase additional electricity from your energy provider as before. However, with SENEC.Cloud we give you the opportunity to cover your entire electricity needs with self-generated energy. With our cloud solution, you effectively “pay in” surplus solar electricity over the summer so that you can “withdraw” it over the dark winter months.

Old batteries from battery storage systems are returned to their manufacturers

According to the German Battery Act (BattG), manufacturers are obligated to take back and recycle their batteries. As a distributor, SENEC is obligated to take back your old batteries free of charge – just as you can return old household batteries to supermarkets. We return the batteries to the manufacturer, who is best placed to reuse the valuable materials.