Frequently asked questions about utility-scale battery energy storage systems (FAQ)

The increased use of renewable energies such as wind and solar energy poses challenges for the national grid. The production of these energy sources fluctuates and is not always in sync with consumption. Without storage technologies such as battery storage, surplus renewable energy often has to be switched off (curtailed) to avoid overloading the power grid.

Distribution and transmission connected battery storage systems can store this surplus energy and then feed it back into the grid when demand is high or renewable sources are unable to supply their maximum output. This optimises the application of renewable energy assets, whilst also helping to stabilise the frequency of the grid. In this way, battery storage systems can make a significant contribution to driving forward the energy transition and reducing dependence on fossil fuels.

Battery storage systems are typically installed near existing grid infrastructure or co-located with renewable assets such as solar farms and offer the possibility of storing large amounts of electricity and discharging it when the grid requires additional energy. This offers the potential to ease the load on the grid and thus reduce the need for extension in short term.

Utility-scale battery storage systems should be planned at locations that allow optimal integration into the power grid. Locations near substations are particularly suitable, as they can feed directly into the grid with minimal elextrical losses. Regions with a high feed-in of renewable energies, such as solar farms and wind turbines, also offer potential, as battery storage systems can store surpluses and feed back into the grid during hours when there is little sun and/or wind.

Utility-scale battery storage systems can be used to provide energy, which helps to compensate for fluctuations in power flows across the grid network. They are particularly used for primary and secondary balancing power, as they can react with large amounts of power in a very short time frame.

• Primary control power: This is activated within seconds to stabilise the frequency of the national grid when deviations occur. Battery energy storage systems can feed energy into the grid immediately or absorb surplus energy to keep the grid frequency at 50 hertz. This type of control energy must be provided for a maximum period of 15 minutes until the secondary control power kicks in.
• Secondary control power: This is activated if frequency deviations last longer. It is activated within 30 seconds and helps to compensate for major fluctuations and give the grid operators time to access other energy sources. Large-scale battery storage systems therefore offer a reliable way of ensuring grid stability.

In the day-ahead market and the intraday market, utility-scale battery storage systems offer the opportunity to buy electricity at times of low prices and sell it again when demand is high or prices are higher. They help to react flexibly to short-term price and grid changes and enable the efficient utilisation of renewable energy.

greentech is in constant dialogue with suppliers and continuously compares cell technologies. Lithium-ion cells currently have significant advantages compared to other cell technologies. Lithium-ion cells are characterised by their longevity, i.e. they can undergo a particularly large number of charging and discharging processes before their capacity decreases significantly. In applications such as grid stabilisation, the technology offers the advantage of a particularly fast response time. In addition to their technical superiority, lithium-ion cells are preferable for stationary battery storage systems due to their high availability.

The fire risk of large battery storage systems is low as they are equipped with their own fire protection system. This usually includes a system for continuous monitoring (e.g. smoke detectors, temperature sensors), automatic extinguishing devices and emergency management mechanisms.

Yes, up to 95% of lithium-ion batteries can be recycled. This helps to reduce dependence on raw material imports and supports the circular economy.

Our projects are realised in the medium, high and extra-high voltage range, enabling us to guarantee broad coverage of the grid levels and meet the specific requirements of the respective locations. The output depends heavily on the local grid situation. In terms of capacity, we are currently focussing on two-hour systems.

Areas that are easily accessible and close to substations or power lines are required for battery storage. Suitable sites are

• Agricultural land
• Industrial and commercial sites
• Former power plant sites

The area should be at least 10 acres in size to enable the operation and planning requirements.

Project development is organised in several steps. The entire process is managed by the greentech team: A site assessment is undertaken to determine the feasibility of a battery development. If the results of this study are satisfactory then a grid application can be made to secure the desired capacity. After which , the landowners receive a preliminary offer. Once the negotiations have been successfully concluded and signed, the planning process can begin. After the planning consent is obtained the site can be constructed and the system is finally put into operation. We take the needs of the landowners into great consideration alongside that of the local community.

Regardless of whether utility-scale battery storage systems are privileged on farm land or realised via an urban land-use planning procedure, greentech relies on close cooperation with the local representatives and the responsible authorities throughout the entire process. For each project, we organise community exhibition events for interested parties at an early stage and attach particular importance to taking the concerns of local citizens and the community into account from the planning stage until the battery energy storage system is realised. For us, acting as equals, regularly consulting and clear communication are crucial in order to create transparency for all parties involved and achieve a high level of acceptance for the project.

We attach great importance on using local companies in the project development (e.g. planning consultants and stakeholder engagement), construction (e.g. fencing, groundworks and civil engineering) and operation (e.g. green maintenance).

Our battery storage systems are connected to the distribution or transmission grid and therefore feed the stored electricity directly into the national grid. Unfortunately, direct marketing to the local community is not yet possible.