How does energy storage work?

Electric Vehicle, Renewables

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If generating renewable energy is important, it is even more important to have it available to users thanks to energy storage, but do we know how it works? 

Our society is heading towards a greener future. A future in which the decarbonisation of our economy is crucial to achieve climate neutrality and, therefore, a more sustainable and environmentally friendly world. Electricity generation is key to this energy transformation process, thanks to the emergence of renewable energies, which enable the generation of green energy. But this type of energy is not always available for our use, as it depends on two conditioning factors: weather conditions and the timetable of demand. This is why electricity storage is a key solution for achieving our decarbonisation goals. But have you ever wondered how energy storage works? Let’s see how.

As we said before, we cannot program the wind to blow when we need it, nor can we make sunlight shine to power our solar panels. So how can we guarantee that renewable energies power our electricity grid? The answer is energy storage. So, thanks to this, we are able to store the surplus energy generated by renewables when demand is low and supply it to the grid when demand is high. This is a technological blessing based on different solutions that we need to know about before understanding how storage works.

The most traditional solution, and the most visible today, is the hydroelectric power plant. Dams and reservoirs that, when the sun and wind are not enough, release the power of the water through their gates to feed the movement of their turbines and thus generate large amounts of electricity according to energy demand. This is the solution that perhaps we are all familiar with but do not always associate with energy storage, as we see it as just another renewable energy source; although its great virtue is the capacity to store the power of water for use when it is most convenient and necessary.

We can also include in this classification the so-called solar thermal power plants, which flourished in the first decade of the 2000s in countries such as Spain, and which store the energy generated by the photovoltaic panels in molten salt that later enable the production of steam and the consequent movement of the turbines that generate electricity. A series of parabolic photovoltaic panels point towards a large central collector containing the molten salt, so that when the sunlight disappears and the demand for energy rises, the supply is available to households. These include plants such as Noor Ouarzazate II (200 MWe) in Morocco, which stores energy for 6 hours.

But if you are reading this article it is probably because of another type of solution, the most innovative and the most #trendy today. We are referring to the storage of electrical energy in batteries. This technology, which could be likened to the powerbank that saves us when our mobile starts to run low on battery power, is revolutionising our grid and is allowing new renewable energy projects to emerge with the guarantee of being able to supply energy at times when weather conditions do not allow for regular renewable energy. So, let’s take a look, point by point, at how this technology, which will become crucial in the near future, works.

A round trip through the electricity network

It all starts at the point of energy generation. Let’s use the example of a photovoltaic plant, which we can all, to some extent, have in mind. So, from the photovoltaic panels, the energy passes through the electrical installation until it reaches, in the first instance, the power converters, which allow us to change the current from direct current to alternating current (AC/DC for music lovers): something necessary for it to flow through the grid without any problems.

To ensure that the grid does not lose any of the valuable watts generated, the equipment in the transformer substations intervenes by raising the voltage and preventing energy losses. Thanks to the work of these centres, the energy arrives “safe and sound” at the electricity substation, which will act as a midfielder – in soccer jargon – distributing the energy in energy that goes directly to the consumers and energy that will be stored in large battery containers for later supply. Well, that’s it, isn’t it? The energy has already reached the batteries and the enigma has been solved. Nothing could be further from the truth, because great ideas require great solutions.

At this point, the energy in the substations has to reduce voltage again and change the current to direct current before it can be stored. In other words, it has to pass again through our busy friends called transformer stations, whose technology and reliability are crucial for the integration of renewables, which then leave the stored energy in the batteries waiting for the call to action. Thus, when demand rises, this energy is sent back to the transformation centres, which once again “fine-tune” the energy by increasing its voltage, sending it to the substation, which will change the current to alternating current, for finally being fed into the electricity grid to reach the different consumption points. Quite an achievement.

Well, it is this complex electrical system that allows, and will allow, the renewable energy generated in a plant in broad daylight to be enjoyed at ten o’clock at night to run our household appliances without emitting a single particle of carbon dioxide into the night. Do you now understand why this technology is so fundamental? Given the huge benefits for consumers and the planet, the deployment of energy storage is expected to triple year on year. With this, in just two decades we will go from around 10 GW of power currently installed worldwide – an undoubtedly token figure – to more than 1,100 GW, making the energy transition and a more sustainable world possible.

Still have doubts? Don’t worry, we have prepared a short video for you to see all this complex operation in a simple and interactive way. Don’t miss it!

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