Energy storage: Key to the effective use of renewables?


In the era of green transition and decarbonization, the instability of renewable energy sources compared to fossil sources is a serious obstacle. The solution is energy storage.

Author: Aleksandra Krzysztoszek /

Content of this article does not reflect the positions or opinions of the EU-SysFlex project or its partners. EU-SysFlex is not responsible for the information or opinions included in this article.


Along with the rising prices of energy from fossil sources and the global trend towards climate transformation, renewable energy sources are gaining on popularity in Poland and other European countries. However, the disadvantage of renewable energy, especially compared to carbon, is its limited stability and controllability. Renewables are very much dependent on weather conditions, such as wind and sun.

That is why energy storage comes as such an important solution. They enable to increase the stability of the RES-based system, which translates into energy security.

“Energy storage, moderately important in the current power system based on stable coal-fired power plants, is becoming a key element in the pending energy transition. The new energy mix will be increasingly based on clean, renewable, future-proof sources, which are, however, rather unstable ”, points out Jan Ruszkowski, communication specialist at the Polish Green Network.

“Everyone – from households to industry – would like electricity to be available exactly when we need it. Although we obtain energy relatively easily, it is much more difficult to store it until the moment when it is in greatest demand”, he says.

„In order to avoid the most catastrophic consequences of the climate crisis, but also taking into account economic factors and the climate policy of the European Union, the heat energy will have to be replaced by the renewables, with a whole set of modern supporting solutions. One of the key elements of this set will be energy storage”, says Marta Gregorczyk from Greenpeace Polska.

How does energy storage work?

Storing energy as such is nothing new. Some of the technologies serving this purpose, such as lead-acid batteries, are already a hundred years old. Energy is stored both in pumped storage plants, as well as in common batteries used in devices (e.g. mobile phones) or vehicles.

There are various types of energy storage available on the market: mechanical storage, including pumped storage power plants, compressed air storage and flywheels, electrochemical (accumulators and rechargeable batteries), chemical (fuel cells, hydrogen storage), thermal storage (heat accumulation) and electric storage (supercapacitors). Energy storage also divides into direct storage (magnetic and electric field) and indirect storage (conversion of electric energy into another type of energy, e.g. chemical potential and kinetic).

The first of the mentioned types has the largest share in the world market. Pumped storage plants are responsible for over 95 percent of worldwide energy storage capacity.

The solution used most commonly in households is the electrochemical method of energy conversion, while large photovoltaic farms generally use mechanical and chemical storage of solar energy.

Pumped storage power plants – large, efficient and useful

Pumped storage plants have the largest power range among the various types of energy storage. The largest power plant of this type in the world has approximately 3 GW of capacity, and in Poland – slightly over 700 MW.

They work in a daily and seasonal cycle, which is important especially for long-term energy storage. Their use effectively increases the stability of energy supplies. What’s more, this type of storage works very well in the face of a blackout threat. In crisis situations, pumped storage plants are able to start high power and thus prevent power cuts.

On the other hand, they take up a lot of space. This limits the freedom in choosing the location for this type of infrastructure so that they work in synergy with RES. The topography is also important. However, low operating and operational costs speak for this type of energy storage.

Other technologies: flywheels, hydrogen storage

Another energy storage technology that can be used in renewable energy, especially in wind farms, is flywheel energy storage. They store kinetic energy. As Aleksander Tetyn from explains, the flywheel accelerates during the loading phase, and when it is unloaded, it brakes. Flywheel storage a very small power range: 0.1 to 20 MW. Its advantage is efficiency exceeding 90 percent. and long service life (approx. 20 years.

Energy can also be stored by using hydrogen as an energy carrier. „Due to its characteristics, H2 in its pure form has an extremely high energy density, which is up to five times higher than the energy from hard coal”, points, adding that thanks to its properties and the possibility of electrolysis, excess energy from renewable energy sources can be used to produce zero-emission hydrogen, which in turn will allow for energy storage, for example in transport or industry.

The disadvantage of hydrogen storage, however, is the high operating and maintenance costs, ranging from $15 to $50 perkilowatt. However, given that this technology is still evolving, it can be expected that the costs will decrease over time.

Energy storage for homes and farms

Experts believe that the development of renewable energy sources will not be possible without appropriate energy storage technologies. Among those who need energy stories are companies, as well as farmers and prosumers who set up solar installations.

In households, it allows for the storage of surplus energy production and its use during the period when solar panels do not produce it. This allows the user to achieve up to 90 percent energy self-sufficiency. The solution mostly benefits people who do not consume a lot of energy during the day, when its production is the highest (for example, because they are at work), but want to make use of all the energy that is produced, but is also useful in places that are exposed to frequent energy breaks.

Energy storage is also a useful solution for farmers. Along with the increased demand for electricity, resulting from the increasing mechanization of agriculture in recent decades, the already high farm maintenance costs are also rising. Increasing electricity prices add to the problem. As a consequence, the bills, for instance for the operation of a cold store, can be horrendous.

To pay less for energy, some farmers decide for photovoltaic. However, due to the nature of their activity, they cannot allow for interruptions in the supply of energy – for example, in the case of fruit growers, too long a break in the operation of cooling systems may result in rotting of the fruit collected in the cold store. Thanks to the energy storage, the photovoltaic installation can simultaneously produce energy to meet the current demand and to charge the storage facilities.

How important are energy storage for the climate transformation and development of renewables?

“According to the best scientific knowledge, in order to combat the climate crisis effectively, Europe, including Poland, must abandon coal by 2030, and gas by 2035. Without investing in the construction of electricity and heat energy storage, this target will be impossible to implement, stresses Marta Gregorczyk.

Energy storage „along with other solutions, such as the intensive development of renewable energy sources (in particular, wind and sun energy), increasing energy efficiency, controlling energy demand, development of prosumer energy – will allow for a departure from burning fossil fuels and a real pursuit of a system fully based on renewable energy”, she says.

„Energy storage is an important complement to renewable energy in the energy system,” agrees Aleksander Śniegocki, an energy policy expert. He stresses that in batteries it is primarily about short-term storage, which allows for a better match of energy demand and supply in a one-day perspective.

„We will also need larger-scale long-term energy storage to cope with seasonal fluctuations not only in supply but also in energy demand – the need for heating will increase the demand for electricity in winter season,” Śniegocki told in a written comment.

The use of batteries for this purpose is not an option due to the scale of needs and cost issues, he says. . The solution is storing energy in the form of hydrogen, which, however, requires appropriate infrastructure. Heat storage can also prove useful, adds the expert.

Energy storage and Polish needs

As indicated by Jan Ruszkowski, currently pumped storage hydroelectric power plants respond for about 90 percent of the capacity of electricity storage facilities existing in the Polish power system. However, such systems will not be developed any more due to the high costs and the lack of favorable conditions. Warehouses based on all kinds of electrochemical cells get cheaper, but are still expensive.

„The needs and challenges are clear – over 7 GW of power from photovoltaic panels produced in the Polish energy sector in the last 5 years comes mainly from micro-installations on the roofs of single-family houses,” says the expert.

He points out that households have the greatest demand for energy in the mornings and evenings, therefore the self-consumption of „own” energy does not usually exceed 20-30 percent. „The remaining energy is transferred to the local distribution network, where its excess causes more and more problems”, he explains.

Government programme will benefit the wealthiest consumers

The new edition of the government’s subsidies programme „My Own Electricity” for photovoltaic from the new year offers funding only to those who install home energy storage, which is very expensive,” says the analysts. Consequently, the programme benefits the most affluent people, and thus the least needy.

“It is also worth noting that the cost-effectiveness of electricity storage grows with their size. It would be much more profitable to invest in larger warehouses by network operators than in individual household installations”.

After the amendment to the energy law was passed last year, some large RES installations (so-called hybrid installations, which consist of both photovoltaic panels and wind turbines) are even required to have their own energy storage, notes Ruszkowski.

Heat accumulators

The Polish Green Network expert also points out that while storing electricity is difficult and expensive, it is easier and much cheaper to store heat energy, which is very much needed not only during the heating season but also throughout the year for domestic hot water.

“Heat accumulators have been used for many years – the main investors are heat and power plants. However, the technology will soon be available also to smaller entities. Small local heating plants in Denmark operate during the day, accumulating heat in a large reservoir of water. The heat comes from a mix of various sources, e.g. solar collectors, windmills, heat pumps, electricity from the grid when hourly rates are low, cogeneration gas turbines and so on „, he explains.

“In the face of very unfavorable changes in the billing of individual photovoltaic micro-installations, which will come into force in Poland from April, storing energy in the form of hot water may become a good option also for households. Especially as selling surplus of own solar energy to an electro-energy operator will soon become extremely unprofitable”, adds the expert.


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