Storage systems

PHOTOVOLTAICS

Storage systems

Together with you, we design the right system for every roof and every individual requirement. Let us advise you.

The future of our energy supply

Renewable energies are the future of our energy supply. One of the most important tasks is therefore to drive the energy transition forward.

Up until now, energy was generated centrally and passed on to consumers via distribution networks. This changes due to the construction of decentralized photovoltaic systems, which means that everyone can become an electricity producer (power plant). The proportion of energy generated from photovoltaics is rising steadily across Germany.

Due to the rapid expansion of renewable energies, the importance of energy storage for integrating self-generated electricity into the supply network is also growing. And since self-generated electricity is cheaper than that of the grid operator, the economic factor of energy storage also increases. In addition, households consume most electricity in the morning and especially in the evening when cooking or the television is on. During the day, however, when the sun is shining and the photovoltaic system is producing electricity, many people are not at home.

A storage system ensures that the environmentally friendly energy is made available with a time delay so that up to 75 percent of the electricity consumed in the household comes from the own solar system. In this way, you can optimize your own electricity and the constantly rising electricity prices only play a minor role. In addition, storage systems enable important consumers to be protected against power failures.

A DC-coupled and an AC-coupled system can be used to store the energy that is available from the current self-consumption.

What kind of storage systems are there?

DC storage

In the DC system, the energy storage device is connected in the intermediate circuit of the inverter of the photovoltaic system. This means that the direct voltage (DC) coming from the photovoltaic modules is not first converted into alternating voltage (AC), but is stored directly in the battery via a battery charge controller.

Compared to the AC storage system, this results in a higher degree of efficiency and lower acquisition costs due to the lack of an additional inverter.

However, it is disadvantageous that the batteries have to be in the immediate vicinity of the photovoltaic inverter, which often poses a space problem. Existing photovoltaic systems are also difficult to retrofit. The DC system cannot be used as an energy store for other energy producers such as combined heat and power plants (CHP), small wind power plants and small biogas plants. Even the likely upcoming smart metering, where electricity can be bought cheaply from the public grid at certain times of the day or week, cannot be used optimally here at the moment.

AC storage

In principle, the energy in an AC storage system is also stored in a direct voltage (DC), as this is not possible in any other way. However, a conversion takes place here from the AC network (alternating voltage network), where the coffee machine, for example, is also connected. An inverter, which is separate from the generation system, smooths the alternating voltage during storage and stores the energy in the direct voltage battery. If the energy is needed, the inverter converts the direct voltage back into the alternating voltage of the house network.

The advantages of this system compared to the DC variant are that it can be used in existing systems and the more flexible location, since the batteries do not have to be located directly next to the inverter of the photovoltaic system, which often leads to space problems. Furthermore, other energy producers such as combined heat and power plants (CHP), wind power plants and small biogas plants can also use the same storage unit, as these are connected to the identical AC power grid. A future-oriented advantage lies in smart metering, where electricity can be purchased cheaply from the public grid at certain times of the day or week.

A disadvantage of the AC system is a low level of efficiency due to the double conversion, since the direct voltage of the photovoltaic system is first converted into alternating voltage and then converted back into direct voltage for storage. Another disadvantage is the higher acquisition costs due to the separate inverter, which is not required for the DC storage system. Polycrystalline PV modules can be recognized by their mostly bluish color and crystalline structure. The use of polycrystalline solar cells or solar modules is currently one of the most frequently used PV modules in PV module production worldwide.

For the production of polycrystalline silicon cells, raw silicon is heated very strongly, cooled in a controlled manner in a casting mold and then cut into silicon wafers, 0.2 to 0.3 mm thick.

The crystal structure is inhomogeneous due to the irregular arrangement of the many crystals and is easily recognizable due to the pattern. Further chemical processes and the application of the contact tracks complete the manufacturing process of the solar cell.

The efficiency of poly- or multicrystalline modules is lower than that of monocrystalline modules. However, compared to monocrystalline modules, the yield prospects of polycrystalline modules per installed kWp are not lower.

Drums

When it comes to storage media, lead gel & lithium are currently the most important technologies.

Lead-gel batteries have a lower purchase price than a lithium system and can be discharged with high currents. However, the service life is shorter and only 50% of the capacity can be used in normal operation, which in turn brings about 30% reserve for the exceptional case of emergency power operation.

Lithium batteries usually do not have such a high discharge current capability, which can be necessary in emergency power operation. However, a load of 95-100% is possible with constant performance, which is more problematic with lead-gel systems. You are also more flexible when choosing a location with a lithium battery.

Lead-acid systems are not advisable in residential buildings, as they are more maintenance-intensive and also have a higher degree of degassing.

In addition, electrically powered vehicles and hydrogen systems can also serve as energy storage devices in the future.