Electrical energy storage facilities – “a thing of the future” or “a present necessity”?

Until recently (4-5 years ago), energy storage facilities were a foreign element for the power system in Poland. In the energy system that included generation, distribution and consumption, there was no energy storage facility. It was like a magical device with two functions: at the time of introducing electricity into it, the storage facility was treated as a final receiver, and therefore all applicable distribution fees were charged, whereas at the time of drawing (introducing) this energy from the storage facility into the grid, it became a generator and was treated as a power plant (producer), i.e. all distribution fees were charged again.

Such an approach to electrical energy storage facilities effectively killed any justification for the business use of energy storage in economic terms. Therefore, in that period, energy storage facilities, also known as energy reservoirs, were used in pilot projects of distribution system operators.

What caused the change to occur? The decisive moment for energy storage facilities was the amendment to the Energy Law, which entered into force on 3 July 2021.

That was a green light for the development of energy storage facilities in Poland. The definitions of an energy storage facility were established, double charging of the distribution fees was eliminated and, most importantly, the cost of building fixed energy storage facilities was started to be classified as a reasonable cost, which became an alternative to investments in cable and network infrastructure. The investments of this type may be included in the operator’s development plans and carried out on the same basis as other investments.

We can say with certainty that following the amendment to the Energy Law the energy storage facility has become a kind of the fourth element of the energy system. It is worth noting the multitasking performance of the energy storage facility.

What exactly are energy storage facilities and how do they work?

In Polish law, we can find three definitions of what the energy storage facility is.

The Energy Law Act describes the energy storage facility as an installation for storing energy, connected to the grid and capable of supplying electricity to the grid.

The Power Market Act defines such a device as an energy storage facility, as referred to in Article 2(17) of the Renewable Energy Act of 20 February 2015, which is capable of supplying electricity to the grid.

RES Act: a separate device or a set of devices for storing energy in any form, which do not cause emissions to be an environmental burden, in such a way as to allow at least its partial recovery.

There are several different energy storage technologies. The most common way of storing energy produced by RES is to use batteries. These are galvanic cells, which can be reused and charged with electric current multiple times. All batteries accumulate, and then release electricity through reversible chemical reactions. The main advantage of lithium-ion batteries is their low weight combined with a high power density, which means that the low capacity device can be charged and discharged with high currents.

A stationary energy storage facility may be part of a generation source, may be used by distribution system operators and a transmission operator to ensure grid operation security, may also be part of the receiving system, and in addition, the energy storage facility and the energy storage may be a separate business activity of a power company. Therefore, a new term appears in the power system, “storage operator”, which is of a new entity that can provide storage services.

Why has the need for using energy storage facilities arisen?

The dynamic development of photovoltaics in the last seven years – the number of prosumers increased from 5,000 to 900,000 – undoubtedly shows that without energy storage facilities, the electricity system will not be able to absorb the energy produced. According to the data provided by one of the distribution system operators (PGE), it appears that it plans to build electrical energy storage facilities with a total installed capacity of around 80 MW by 2030.

Given the connection conditions issued so far and the recently started construction of offshore wind farms, we will have almost 50 GW of renewable power installed in the system by 2030, of which around 6 GW from offshore farms, and by 2040 the capacity from offshore farms will increase to 11 GW.

The development of RES has also caused many problems and identified many barriers in the power system. The spontaneous shut-downs of PV systems, the inability to receive the electrical energy generated from RES, outdated low-voltage grid, the technical difficulties of maintaining operation safety of the grid with high saturation of prosumer systems or, last but not least, the refusal to issue connection conditions for new RES installations have led to the search for solutions that could prevent all these problems.

Read also Modern PV energy storage facilities – can a company be self-sufficient in its energy needs?

What are the advantages of electrical energy storage facilities and why are they cost-effective?

1. Postponing the consumption – with energy storage facilities, prosumers and all users can wait and use the stored energy when they really need it.
2. Network parameters stabilization – with electric energy storage facilities, the distribution system operators can smooth the load curve of the network due to the power generation which is highest in the afternoon, while the consumption is lowest in this time.
3. Voltage control – the biggest problem currently faced by prosumers, as voltage in the nearest network is too high at the time when the generation is largest.
4. Reduction of ordered power – in this way, industrial plants and other energy consumers can reduce their financial costs, increase their functionality, and ensure the security and continuity of power supply.
5. Improvement in power supply reliability – in locations with poorly developed distribution infrastructure.
6. Elimination of problems with connection power – operators of electric vehicle charging networks on high-speed roads, in city centres, etc.
7. Possibility of connecting more RES without investments in the transmission infrastructure.
8. Optimization of power supply structures – we can build an electrical energy storage facility instead of rebuilding a specific section of the distribution network (cost-effectiveness balance).
9. Reduction of power factor (reactive power compensation).
10. Provision of system services, power balancing, power reserve, load equalization.

This is just a sample list of power storage facility applications – with a little imagination and will, we can find the application of energy storage facilities in every sector of the industry.

Looking at the wide range of applications as well as the need to strengthen the power system and the necessity to store energy, we have to accelerate investment in energy storage facilities. This is also due to the need to modernize our distribution and transmission networks in the context of the development and possibility of integration of RES sources into the power system.

One of the energy storage solutions on the market to support the supply of power station auxiliaries is the 3S – SunSmartStore technology offered by Eltel Networks.

How to select an electrical energy storage facility?

We can ask ourselves – but what energy storage facilities do we need? Those prosumer ones for home installations, or collective energy storage facilities that serve groups of prosumers? Or maybe the storage facilities that the operators will invest in, both at the distribution network level and at the transmission network level?

The answer to this question is very simple – the point is not “whether”, but “how much”.

Both the domestic prosumer energy storage facilities (e.g. in 3S technology) and the industrial collective energy storage facilities, operated for example by an energy community, are clearly needed, but also the energy storage facilities at the level of network operators are required. In this case, it is necessary to use large container-type energy storage facilities from recognized manufacturers, such as Tesla or Hengtong, for which Eltel Networks proposes the development and configuration of solutions dedicated to a specific customer according to its expectations and needs.

It is important here to use the potential and the functionalities offered by the energy storage facilities at different investors and different locations within the system.

How much is a power storage facility? Can it be subsidized?

When new technologies emerge, the age-old question arises: “How much does it cost and why is it so expensive?”.

It is difficult to clearly answer how much an energy storage facility costs. Many factors influence the price. The first and most important is the capacity of the battery, the other one is the type of batteries to be used, the space available for the battery to be built-in – and much more.

So we can see that the price will fluctuate in a fairly wide range. Based on the data found on the Internet, we can assume that the prices of domestic energy storage facilities of approx. 3 kWh start at about PLN 20,000 PLN and the domestic energy storage facility of 5 kWh is about PLN 30,000 to 35,000. However, attention should be paid to an extremely important parameter that characterizes energy storage facilities, namely the so-called life span. It varies from 5 to 20 years with approx. 10000 charging cycles.

Therefore, the prices of energy storage facilities should be approached with great caution, as a change in any parameter can significantly affect its price.

Despite the continued development of technologies and falling prices of energy storage facilities, their price goes beyond the financial capacity of many households.

In response to the increased interest in photovoltaic systems, the Ministry of Climate and Environment, under the governmental program named My Current 4.0, has covered with subsidies not only PV systems, but also energy storage facilities. The priority in My Current 4.0 program will be solutions to increase self-consumption at the point of power generation through its storage.

The maximum amount of funding for the installation one can receive under this program in the form of a non-repayable grant is PLN 7,500 for an energy storage facility of 2 to 10 kW.

Why is it worth to develop and support the installation of energy storage facilities in different areas of the system?

Because it is best to solve the problem where it arises. Prosumer systems represent a certain technical challenge for the functioning of distribution networks. Most distribution networks were designed many years ago and no one planned them to be bidirectional flow networks. At the time of the construction of the networks, it was not expected that almost one million micro-power plants would be present at the terminals of the network, because, after all, any PV system is a kind of a power plant. The whole process of the design and construction of domestic PV systems is mostly carried out under a notification of construction works. It follows that the transmission system operators find out about such an installation only afterwards and are unable to prepare (upgrade) the specific section of the system in advance to receive electricity from these installations. There are therefore problems with the introduction and receipt of energy produced by domestic plants. Thus, domestic energy storage facilities make sense and are technically justified, since they enable the distribution system operator to incur lower expenditures for network upgrades.

Coming back then to the question in the title, it is safe to say that what was “a thing of the future” a few years ago has become “a present necessity” now.

Based on the recent efforts made by both Poland (on 18 May 2022, the Senate’s National Economy and Innovation Committee held a debate “Energy storage facilities as part of building energy security in Poland”) and the European Commission (when presenting the action plan for building energy independence across the European Union, the role of energy storage facilities was emphasized), we can see that there is no development of RES and power engineering without electricity storage facilities.

Read also Electrical power engineering in the face of the climate crisis

Author: Zbigniew Styczeń