TRITEC Support Storage Systems

Frequently asked questions for the Storage Systems support site

PV storage. In our FAQ section, we have put together useful information about the application and the mode of operation of storage devices from our TRITEC product range. You also have the opportunity to ask us questions. Our TRITEC product management is looking forward to your e-mail!

General questions regarding storage devices

What exactly is a PV storage system?

A PV storage system is a device, which stores electrical energy of a solar system for later use. Private household energy is predominantly consumed at times of the days, which differ from the times solar energy is usually generated. Moreover, the seasons and weather conditions also have a major impact on the energy yield. For optimum use, the system stores the available solar energy in batteries.

What are the differences existing among storage systems?

PV storage systems can be distinguished in terms of AC or DC coupled storage systems.

How is an AC coupled storage system structured?

In an AC system, the battery is separately connected – via its own inverter and direct current converter – to the alternating current mains of the house. Via a mains inverter, PV modules feed the generated energy into the house AC mains. The AC storage device takes produced energy from the alternating current mains and converts it into direct current for charging the batteries.

How is a DC coupled storage system structured?

In DC systems, the battery is connected – on the DC side – to the intermediate circuit of the inverter after the MPP tracker of PV modules. Batteries are directly charged by the direct current of the PV system.

How do storage systems work?

Together with PV modules, the storage systems can fully automatically control private power consumption. Depending on the available solar energy, the storage system controls own consumption, energy storage, as well as feeding energy into the grid.

Which components do storage systems include?

They generally include batteries, charge regulators, battery controls and inverters.

What are the benefits of the storage systems for the end user?

Greater independence of increasing electricity prices, with the long-term result of lower electricity bills. Suitability for new and existing installations. More own consumption and thus increased efficiency of the PV system

Where does power come from when the sun does not shine?

When the sun does not shine, stored power from the storage device is used first. Should the stored capacity be insufficient, additional power is taken from the power grid.

What happens when the sun shines and the energy stores are full?

If the batteries are fully charged, the excess power is fed into the power grid at the feed-in tariff.

What happens in winter when modules are snow-covered?

The storage system takes over your energy management fully automatically. Should there be no energy from the sun and even the energy stores are depleted, power will be automatically supplied from the grid.

Can a storage system bridge over a power/grid failure?

During a grid failure, storage systems with standby power or emergency power capability can supply power to the connected consumers. In this case, however, only those consumers should be connected which are supposed to be continuously supplied with power during a grid failure: Refrigerator, heating system, emergency lights, etc., since these consumers can only be supplied with energy until the batteries have reached their maximum depth of discharge.

Depending on the storage system, there will be an interruption between 3 and 10 seconds when switching from grid operation to emergency or standby power operation.

Can storage systems be used to operate two-phase and three-phase appliances such as an electric cooker or a water boiler?

There are storage systems, which are designed for one-phase or three-phase operation. With offset dual position counters, multi-phase consumers can also be completely supplied with a single-phase storage system in grid operation. That is due to the fact that offsetting is solved by balancing, and the feed-in counter totals over all three phases. Then it doesn't matter in which phase there will be the feed-in, in which phases the consumers are, and whether power is perhaps fed in on one phase and on the other two phases it is consumed.

What about the start-up power of e.g. a circular saw?

In grid operation, the required "extra energy" is provided by the public grid. A major part of the storage system (depending on the devices) can provide short-term "extra energy" in a backup operation.

When will the system have paid for itself?

Depending on the PV system, energy consumption and energy purchase price, a storage system can already have paid for itself within 7 to 10 years.

Which size of system is appropriate for a storage system?

The storage systems in the TRITEC product range are offered in different designs and possible extensions, and they are suitable for any size of system. For more information, see our data sheets.

Can storage systems be retrofitted with existing PV systems?

For AC coupled storage systems, retrofitting to an existing PV system is possible without any adjustments to the PV system. For DC coupled storage systems, DC inputs must be designed for current stringing. Otherwise, changes must be made to stringing. Also, in DC systems, the existing inverter can no longer be used.

What to do with my old inverters?

Inverters are an integral component of the complete systems. If you already have inverters, you may sell them to a dealer of your confidence or, for example, in on-line auctions for the best price.

Can the storage system be leased?

We currently do not offer any storage leasing.

Questions regarding batteries

Which rechargeable battery system is used?

For PV storage systems, two different no-maintenance battery technologies are mainly used: The lead gel technology and the lithium technology. The lead gel technology has been tried and tested for decades and is accordingly very reliable. In contrast, the lithium technology is still quite "young" or recent, but it has a much longer service life and more charging cycles.

What is the life expectancy of rechargeable batteries?

The lead gel technology is designed for a maximum service life of up to 10 years with a maximum of 2,500 full cycles. Depending on the lithium battery type, the lithium technology is designed for a life of up to 20 years with a maximum of 8,000 full cycles. Many tests showed a much higher service life. These values may differ very much with different battery manufacturers and types.

How long can the nominal output be retrieved when the rechargeable battery is full? For lead technology, nominal output can be retrieved up to a charge level of 50%, for lithium technology up to a charge level of 20%; furthermore, power is obtained from the PV system or from the grid. Its duration depends on the size of the storage system. These values may differ very much with different battery manufacturers and types.

Is it possible to subsequently connect additional batteries?

Yes, there are a few models which can be retrofitted.

Is there a guarantee for rechargeable batteries?

Yes, however the guarantee period and the scope as well differ very much from one manufacturer to the other.

What happens when rechargeable batteries are defective?

The storage system issues an error message. For the most part, the battery units can be replaced any time by specialists.

What happens when, in winter, the storage system is discharged to its maximum depth of discharge and the modules are snow-covered for several weeks? With some systems, the storage part may be put into a sort of "hibernation" period. The storage system will be inactive for that period of time. Batteries are charged up to a certain percentage so that the batteries' own discharge over several weeks will not be harmful.

Is a storage system still functional if the battery completely deteriorates or only one cell deteriorates and/or is defective?

The actual function of the system (own consumption of solar energy, feed-in, consumption of grid energy) is not affected by the batteries' aging. Lithium technology: Here, each individual cell is continuously electronically monitored and charging will be controlled so that the battery's end of service life generally occurs simultaneously for all cells. Lead gel technology: As a rule, lead batteries do not fail suddenly but – if at all – individual battery blocks or cells will slowly lose their capacity or are short-circuited after their usual service life. Reduced battery capacity can be detected based on the data on energies, voltages, etc. in the system display.

Must installation sites of storage systems be ventilated?

Ventilation depends on the battery technology used. Lead technology: While in operation, all lead batteries develop hydrogen and oxygen gas in their housing interior. This is known as oxyhydrogen gas. Under certain conditions, these gases can escape from the battery to the surroundings, partly via the pressure relief valve. This applies independent of battery technology, design or manufacturer. During installation, the ventilation specifications EN50272 are to be complied with concerning setup and ventilation. Lithium technology: For lithium batteries, there are currently no special requirements regarding additional forced ventilation. You will receive more detailed information about this from the battery manufacturers.

Contact PV Storage

Head of Product Management

Simon Schmidt

+41 61 264 00 25

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