Energy Storage Systems in Batteries Are Emerging

Considering all the negative consequences that humanity is already feeling due to the excessive exploitation of fossil fuels, it is more than clear that renewable sources of energy such as wind, water, and solar are key to supplying economies and households with energy for the years to come. However, the intermittency of such sources, which also affects energy price volatility, is a challenge that still needs to be addressed. The solution that is emerging, which still needs technological refinement, is the construction of large battery systems that could store the produced energy for later use, or, simply put, to further balance energy production and consumption.

Connection for Balance

To create such a battery system in Croatia, a year ago the European Commission approved a non-repayable grant of 19.8 million euros to the Rijeka company IE-Energy, which will build it near Šibenik. The system will have a capacity of as much as 50 megawatts, or 110 megawatt-hours, and will be among the largest in the region. As explained to us by Željko Šmitran, the director of IE-Energy, the project is in the final phase of obtaining documentation.

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– We expect to start in the first quarter of next year. The battery system connected to the transmission network will serve to balance the system and will contribute to the easier integration of a larger number of new, but uncontrollable renewable energy sources, such as wind and solar, with its flexibility in both directions – receiving energy from the grid and giving energy back to the grid – Šmitran announces, emphasizing that it is still difficult to say what the current demand for such systems is, as the market is still in its infancy.

In addition to the mentioned example of a large project in Croatia, Hrvatska elektroprivreda already has three energy storage battery systems in operation – in the building at HEP’s headquarters in Zagreb, as part of the e-charging system at the Vukova Gorica rest area, and next to the solar power plant on Vis.

– The battery system on Vis, with a power of one megawatt and a capacity of 1.44 megawatt-hours, was installed with the aim of providing balancing services for the electricity system and to preserve network stability on the island. Projects for battery storage are being developed at several potential locations in Croatia, for example, on the islands of Unije and Lošinj, in KTE Jertovec, and others, with a total capacity of up to 50 megawatt-hours – they emphasize at HEP.

Practically Alongside Solar

They add that they see the greatest potential for application in the installation of battery storage next to solar power plants.

– Battery systems for storing electricity work well when connected to a solar power plant, either in the form of large industrial photovoltaic plants or photovoltaic panels on the roofs of houses. The battery storage can be charged with energy from the solar power plant during periods of excess production and supply consumers with electricity during periods when the plant is not producing. This means that users could continuously be supplied with renewable energy – they explain at HEP.

The Croatian Transmission System Operator (HOPS) deals with connecting such storage to the transmission network. However, according to the Electricity Market Act, HOPS cannot own energy storage facilities.

– HOPS only deals with the connections of such storage to the transmission network, which may eventually be used to provide ancillary services. In Croatia, there is currently no requirement that, for example, every renewable energy plant that connects must have an appropriate battery installed – they note at HOPS.

Additionally, HOPS supports the connections of battery systems because, as they emphasize, ‘they can have their role in providing ancillary services and alleviating congestion in the network’, but they note that HOPS is not in a position to require the installation of such devices.

The Magic of Batteries

Some of the advantages of battery systems over other electricity storage systems that they mention at HEP include fast response, a lifespan longer than ten years, efficiency greater than 90 percent, high adaptability to the user (large range of electricity storage capacity and large range of output power), reliability, and safety. The reaction to the needs of the transmission system dispatcher within two seconds is an advantage that Šmitran also mentions, adding that the installation and implementation of the system is relatively simple, ‘thus avoiding expensive and slow upgrades of the energy system’. At HEP, they also explain that owners of battery storage ‘can achieve additional income and justify the investment in battery storage by trading on the electricity market or providing ancillary services to the electricity system such as voltage and frequency regulation’.

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However, as the biggest disadvantage of the system, HEP cites the high investment cost, which includes the installation of expensive materials in batteries, and they note that an additional disadvantage is the low energy storage density. Šmitran, however, emphasizes that batteries ‘are not the solution to all problems’, but are an important element that is combined with other elements of the system at the transmission level. He believes that the legislative framework of the Republic of Croatia is fully in line with European Union directives and allows for the unhindered development of projects such as the construction of a large battery system near Šibenik.

– Now it only takes time and private initiative for the projects to be developed and put into operation – adds Šmitran.

Whether it is about large stationary energy storage in the electricity system or small user devices, the basic and most commonly used energy storage technology is currently lithium-ion batteries, they explain at HEP. However, the full potential of batteries is much greater.

– Batteries could have wide applications in various household devices, especially in synergy with photovoltaic panels on the roofs of houses. Namely, batteries in devices can be charged at times of lower electricity prices in the market and discharged at times of higher prices, providing ancillary services to the electricity system, which would represent an additional source of income for households. For such a development to occur, a further drop in battery prices and a clear and sustainable model for participation in the electricity market and providing ancillary services to the electricity system are needed – they explain at HEP.

System Security

Šmitran, however, believes that batteries are not key for charging, but will be key for the safe functioning of the system, together with other elements of the system, such as, for example, reversible hydropower plants, new power lines, and connections of sufficient capacity with neighboring countries, as well as advanced digital systems for managing the energy system.

– Here I primarily mean behind-the-meter batteries installed at end consumers who also have integrated solar power plants on their roofs. Their full economic value will come to the fore the moment dynamic tariffs are introduced to our market alongside existing lower and higher tariffs, which will allow end users to achieve additional economic benefits through their flexibility in production and consumption, i.e., by using batteries, via so-called virtual power plants, for example, at noon when there is too much energy in the system or in the evening when that energy is lacking, and in return help the system operator to manage the system more easily and safely, in which, in the future, a large part of the energy will come from uncontrollable renewable energy sources. This will reduce the risk for the operator and for users from unwanted consequences that may potentially arise from the integration of renewable energy sources into the electricity system of Croatia – Šmitran explains, emphasizing that one of the priorities for system operators will be risk management, as the electricity market of the EU functions based on their infrastructure and the infrastructure of network users.

– The short-term shock in electricity markets due to the start of the war in Ukraine best demonstrated this – concludes Šmitran.