Components of a solar power storage system

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Solar power storage is available in different designs and for (almost) every need – from small devices with low capacity to large storages that have space for many kilowatt hours of electricity. Due to the constant further development of the technology, the devices are constantly getting new features and additional functions, to know more checkout

The most important components of battery storage

But as exciting as the technology inside is, some power storage devices look unspectacular: rectangular (often single-colored) boxes that vary in size between a small chest of drawers and an oversized refrigerator. But “designer pieces” for hanging on the wall or for installation in the utility room are also increasingly being offered. While there are of course certain differences from manufacturer to manufacturer and model to model, the basic components of solar powered generator are always the same.

The battery or more precisely the solar battery is the heart of the storage system. Here the energy from your PV solar panel system is temporarily stored using sophisticated electrochemical processes. For a long time, lead-acid batteries were considered the battery standard. In the meantime, however, 12v lithium battery are most frequently used on more than 90 percent of storage devices (you can find out about the advantages and disadvantages of the respective materials in the chapter “Tips for your storage device purchase”). No matter which type you choose: high quality and reliable functionality are important characteristics of a good battery. So you can unload and reload them many times. At the same time, however, you should take into account that you will have to change the battery after 10 to 15 years. Because even the highest quality batteries lose their power over time. However, the exchange is usually possible without any problems.

The battery management system (BMS) ensures that everything is in order when charging. It constantly monitors the battery’s activities and has a variety of functions to react appropriately under certain circumstances – for example when the battery is about to overheat. In addition, the BMS protects against overcharging and regulates the charging process. The charging management procedures differ for the individual battery types, since they have different requirements. With lead-acid batteries, for example, it is important that no harmful chemical processes (so-called “gassing”) occur during charging. Lithium-ion batteries, on the other hand, ideally have to be charged more gently and more slowly. When discharging, the battery management system ensures that no deep discharge takes place. This means that the battery will not be discharged below a certain voltage. This could cause serious damage to the battery. Protection against deep discharge is particularly important for storage systems for solar power. Because in phases with little sunshine, more energy is drawn from the battery than is recharged by the PV system. Without a corresponding regulation by the BMS, the limit of the normal depth of discharge would quickly be undershot.

Also essential for the usability of the electricity storage is the inverter, in the specific case of the photovoltaic system also called solar inverter (3000w power inverter is one of the most common). It converts direct current into alternating current< Why is this necessary? Rechargeable batteries work on direct current, but most household appliances require alternating current. The public power grid is also based on alternating current. If you want to feed the electrical energy from your solar power storage system into the grid, it must first be converted accordingly. Your PV system also has an inverter for the same reason. Because the solar cells also produce direct current, an inverter between the system and storage is not necessary as standard.

The charge controller lives up to its name. In addition to the BMS, it regulates the charging current and charging voltage of the battery. This ensures that the battery is charged gently and that its capacity and performance are retained for as long as possible. The charge controller communicates between the PV system, the storage system and the connected end devices and thus supports battery charge management.

Important terms relating to solar storage

How a storage battery works is hard science, not rocket science. Nevertheless, technical details and connections can sometimes be difficult to understand – especially if you are not particularly tech-savvy, let alone well-versed in the fields of physics and chemistry. So that you can still find your way around the jungle of technical terms, we would like to explain the most important terms relating to solar power storage in the following.

Efficiency, how efficient the storage is

You may have heard the term “efficiency” before, for example in connection with motors. In general, the efficiency indicates how efficiently a device converts or uses the energy supplied. In the case of electricity storage, the efficiency relates specifically to the question: How much of the electricity fed in from the PV system can actually be drawn afterwards?

Because a certain part of the supplied energy is de facto lost during the storage process. Strictly speaking, the energy is not lost, keyword “law of conservation of energy”. However, it is converted into heat when stored and is therefore no longer available to you as electricity. Across the board, the efficiency of solar power storage is between 70 and 95 percent. However, it is important to differentiate here again between the efficiency of the battery and the overall efficiency of the entire power storage system.

There is also the system efficiency. It describes the entirety of all efficiencies relevant to your PV system. In addition to the efficiency of the storage system, the efficiency of the photovoltaic system itself also counts. Because as soon as the solar energy has reached the solar cells, the solar power passes through various stations (e.g. solar modules, cabling, inverters). There are also losses.

Cycle count, how long the memory lasts

You have probably come across the term “cycle” in other contexts. The word comes from the Latin “cyclus”, which means nothing other than “circle”. In the case of power storage, a cycle denotes a process of charging, storing and discharging the energy. Manufacturers of power storage and rechargeable batteries indicate the estimated service life of the respective device using the number of possible cycles – the so-called number of cycles.

Strictly speaking, this means full cycles. This means: When charging, the full capacity of the battery is used and when energy is drained, the battery is emptied down to the maximum depth of discharge. However, this is a very theoretical scenario. In practice or in everyday use of the memory, full cycles rarely occur. The electricity storage is often not fully utilized and there are only so-called partial cycles. These only correspond to a certain proportion of the possible full cycles. A solar power storage unit normally manages more partial cycles than the full cycles specified by the manufacturer (the service life of modern devices is around 5,000 to 10,000 cycles).

Storage capacity, how much the storage can store

The third important term is storage capacity. It simply describes how much energy your solar power storage unit can absorb. While “the higher, the better” can be said with a thumbs-up in terms of efficiency and number of cycles, it is a bit more complicated when it comes to storage capacity. Because the optimal storage capacity depends entirely on your individual situation and the power consumption in your household.

In short: precise considerations are called for here. Your storage capacity should be large enough to power the household from sunset to sunrise. At the same time you want to avoid unnecessary additional costs and still use as much solar power as possible yourself. If the storage is too small, it cannot store enough energy for the night. Then you have to buy expensive electricity from the public grid. An example: Every month you need 300 kilowatt hours (kWh) more electricity than your storage system can supply. At an electricity price of 40 cents per kWh, that’s 120 dollars in avoidable additional costs. The solar calculator can help you calculate how many solar panels you need to install and how many capacity batteries you need.

So why not just buy an extra-large model right away? Then the storage would always have enough energy “in stock”. On the other hand, you could also no longer feed as much electricity into the grid. With a (hypothetical) payment of 10 cents per kWh, 500 kilowatt hours that are not fed into the grid would mean a loss of 50 dollars.

What electricity storage means for your household

Many operators of private PV systems do not even have electricity storage on their screens when building their new system. Some don’t even know that this option exists. The other is often not aware of the immense advantages such a device brings him.

Electricity storage means more independence

Because you make yourself even more independent of the public power grid: Instead of an average of 30 percent without a storage system, you get an average of 60 percent of your electricity from solar energy with a storage system. With an exemplary consumption of 4000 kWh per year, that’s 2000 kWh.

In addition to the financial aspect (at a price of 36 cents per kilowatt hour, for example, 720 dollars can be saved every year in our example) the “climate protection” factor is an additional motivator. Because the more energy you can use from your PV system, the higher your personal share of green electricity. In any case, it is worth considering a power storage system from the outset when planning a photovoltaic system.