Energy storage: prosumer, in a transformer station or large-scale?

The importance of energy storage for the power system

The impact of renewable energy sources on the power grid

The existing power grid system is designed to distribute energy from large power plants. However, the shift towards renewable energy sources, driven by the need to reduce CO2 emissions, involves decentralized sources connected to the network at various locations. These sources operate irregularly based on weather conditions. In contrast, a centralized power system architecture is vulnerable to issues such as local voltage surges and excessive energy production compared to demand at a given moment. This often leads to disruptions in renewable energy installations and energy losses, particularly on sunny days when photovoltaic energy production could be at its peak. Additionally, potential prosumers may encounter difficulties connecting their installations to the grid due to its limited capacity.

Solution to the problem – energy storage

To make distributed energy generation both profitable and compatible with the power system, energy storage becomes essential. It enables the utilization of excess energy generated during periods of overproduction at times when demand surpasses generation. Among the various technologies, lithium-ion batteries emerge as the most popular for this purpose. This article will specifically delve into energy storage facilities employing lithium-ion batteries.

Prosumer energy storage

Prosumer energy storage units are compact energy storage devices crafted to store energy generated by home photovoltaic installations. Typically, their capacity spans from several to several dozen kilowatt-hours. In Poland, the most prevalent storage facility has an installed energy capacity of 10 kWh. This popularity is attributed to its optimal alignment with installations boasting a power range of 5-7 kW, commonly observed in single-family homes.

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Advantages of prosumer energy storage

Independence from grid energy supplies

Integrating energy storage into a photovoltaic installation facilitates the utilization of a substantial portion of the generated energy right at its production site. In the case of a hybrid or off-grid PV setup, energy storage plays a crucial role in achieving complete independence from other energy sources.

Fewer refusals to connect renewable energy installations

Acquiring approval to connect a photovoltaic installation to the grid poses a considerable challenge today, as numerous renewable energy sources are already connected, contributing to voltage fluctuations. The implementation of prosumer energy storage proves effective in mitigating the risk of overloading the grid with distributed generation, thereby eliminating a prevalent reason for rejection.

Prosumers are becoming flexible

Energy storage enables the accomplishment of what is unattainable with renewable sources alone: the regulation of the energy supplied to the grid at any given moment. This capability ensures the storage of excess energy during production peaks, facilitating its release when demand arises. This proves to be an economically advantageous strategy, as owners can accumulate energy from renewable sources or the grid during periods of low prices and subsequently sell it at peak prices.

Financing for prosumer energy storage facilities in Poland

Within the Moje Prąd 4.0 program, individual prosumers holding contracts with a DSO have the opportunity to seek financial support for energy storage facilities surpassing 2 kWh in capacity. However, eligibility is subject to specific conditions, such as the requirement to settle accounts through the net-billing system or transitioning to such a settlement arrangement.

Disadvantages of prosumer energy storage

More expensive per unit

The cost of small energy storage facilities per unit of installed energy is higher when compared to larger storage facilities. Specifically, a storage facility with a capacity of 10 kWh is priced at approximately PLN 30,000.

Greater consumption of raw materials

Storing energy on a smaller scale is less efficient compared to larger-scale storage. When storing energy from multiple installations separately, a larger total capacity is required than for a single, larger storage facility. Additionally, the extraction of materials like cobalt and lithium, essential for lithium-ion battery production, has environmental impacts. Furthermore, there is a rapid depletion of lithium resources, which presents a risk of challenges when transitioning to alternative forms of energy storage before their technologies are fully developed.

Energy storage in transformer stations

Energy storage units can be situated in transformer stations, offering space efficiency and simplifying various electrical connections. Typically, energy storage in transformer stations has a capacity ranging from several dozen kilowatt hours. To increase energy storage, individual stations can be interconnected.

Advantages of energy storage in transformer stations

Cheaper and more effective than prosumer ones

The greater capacity of energy storage in transformer stations enables a reduction in space and materials required for production compared to distributed energy storage systems. This leads to cost savings and, simultaneously, allows for a more efficient utilization of the installed energy.

Multiple applications of energy storage in transformer stations

Energy storage facilities in transformer stations serve multiple purposes beyond storing energy from PV installations. They can draw energy from the grid during periods of low prices, enabling its use when grid prices are higher. These facilities can supply power to industrial plants, commercial establishments like gas stations or shopping centers, and even residential estates. In case of a power system failure, energy storage in transformer stations can act as a temporary power source.

Flexibility and expandability

Energy storage in transformer stations offers flexibility in choosing capacity and power according to the specific requirements of customers. The modular design of both individual batteries and entire stations allows for easy expansion if there is an increased demand for energy storage.

Disadvantages of energy storage in transformer stations

Difficulty in selecting the optimal energy storage

Investors frequently grapple with the decision of choosing the optimal energy storage solution. This decision is not straightforward, as opting for a larger capacity warehouse entails higher costs, while a smaller warehouse might not sufficiently store significant energy surpluses.

Large-scale energy storage

Large-scale energy storage facilities, commonly referred to as hubs, boast capacities ranging from hundreds of megawatts to gigawatts, exemplified by structures like the Tesla Megapack in Australia. These facilities are composed of numerous smaller elements distributed across an extensive area.

Advantages of large-scale energy storage

Energy storage efficiency

The extensive capacity and formidable power of hubs significantly reduce instances where they cannot store surplus energy, ensuring that the power they deliver is typically adequate to meet demand.

Economic efficiency

Similar to the previously mentioned types, large-scale energy storage systems enable the purchase of energy at lower prices and subsequent resale at higher prices. Due to the substantial scale of these solutions, profitability is often realized within a short timeframe.

Disadvantages of large-scale energy storage

In the event of a failure, a larger group of recipients is affected

Energy storage systems employing lithium-ion batteries face fire risks due to thermal runaway resulting from product defects, damage, or improper operation. This issue is especially pronounced in large warehouses, as battery fires can spread to adjacent cells. If one cell overheats, a chain reaction can impact others, leading to the combustion of an entire module and temporary decommissioning of the entire energy storage facility. There are instances of proactive shutdowns of energy storage units due to fires in similar units, posing challenges for both storage owners and energy consumers.

Optimal energy storage depending on the application

The selection of an energy storage system depends on the specific requirements of the facility it will collaborate with. For scenarios with limited energy generation, prosumer storage is likely the optimal choice. This type of storage can facilitate independence from the grid for facilities with lower energy demands. Hubs are well-suited for large-scale projects. However, energy storage in transformer stations emerges as a versatile solution. While primarily designed for medium-sized facilities, these stations can also power numerous smaller loads. Additionally, energy storage in transformer stations may serve as an alternative to larger storage facilities, integrating into setups like microgrids or virtual power plants.