Is it possible to store surplus energy?

The electricity generated from different sources is fed into the grid to respond to demand at different times of the day. So generation can be adjusted to avoid shortages and guarantee the energy supply, based on forecasts that take into account a number of factors including demand at similar times in the past, the weather, etc.

There are generation models that allow the volume of energy produced to be varied: For example, it is possible to vary production from a nuclear, thermal or hydroelectric power plant. However, this is not always possible with renewable energies. This is why.

The challenge of the Energy Transition

The aim of the Energy Transition is to progress towards a model where efficiency, independence and sustainability give greater prominence to emission-free renewable energy sources.

However, with this type of energy production cannot always be regulated. With a wind farm, if you wish to produce less energy you can stop some generators. But if you wish to produce more and there is no wind, it will not be possible. But wouldn't it be more efficient to always produce as much energy as possible and be able to store the surplus for times when renewable energy production falls?

That is why large-scale energy storage is presenting challenges with regard to innovation and development. To make progress in decarbonisation and give greater prominence to renewable energies in generation, we need to be able to inject the surpluses produced from these sources into the grid by means of efficient, versatile, high-capacity and at the same time economical storage systems.

Nevertheless, in a domestic environment, storage systems are more than able to make self-consumption easier. Here are some of the different types of storage.

Main energy storage systems

We will start with large-scale storage systems (those with the highest capacity that can store GW).

• Pumping stations: They use surplus energy to lift bodies of water. When demand increases, those bodies of water are released to produce hydroelectric power. It is an efficient and non-polluting method.
• Compressed air: Compressed air is stored underground using surplus energy. When demand increases, it is released and the pressure is used to generate energy.
• Thermal storage: This consists of using heat by means of materials with properties to preserve it. When more energy needs to be produced, it is released in a controlled manner in a steam cycle.

Now it is time to talk about storage systems in grids and generation assets (their capacity corresponds to MW).

• Flywheels: Spinning discs are used to conserve kinetic energy.
• Supercapacitor: They produce electricity through electrostatic charges, so they can quickly store and release large amounts of energy as required.
• Hydrogen Batteries: This enables constant use of energy from green hydrogen (obtained by the electrolysis process), through battery storage.
• Batteries: They contain chemicals that enable energy to be generated quickly. They are versatile, scalable supports and they are very suitable for storing surplus energy from renewable energies.

Boosting energy storage

As the different administrations become aware of the need to promote efficient energy storage, they have implemented a number of initiatives to make progress in this area. In 2020, the Ministry of Energy Transition and the Demographic Challenge published its Energy Storage Strategy, with the aim of increasing from the 8.3 GW currently available to a total storage capacity of about 20 GW in 2030 and 30 GW in 2050, in response to the estimated requirements for those dates. This has involved activating measures including aid for innovative storage projects.

Solar energy storage

By its very nature, solar energy is not always available to generate electricity. That is why it is essential to have an efficient storage mode that can guarantee taking advantage of surplus production in those hours when the sun does not shine.

The clearest example we currently have is that of photovoltaic self-consumption, where the surplus is not injected into the grid or wasted, but is stored to be used when needed.

According to a study by the Spanish Photovoltaic Union (UNEF in Spanish), batteries in self-consumption installations in Spain stored up to 1,382 MW hours of solar energy in 2022, an upward trend as a result of the improvement in efficiency and price of batteries.

Another way to make the most of that surplus energy is buy using virtual batteries. These enable you to accumulate the equivalent in euros of the kWh injected into the grid.

If you are looking to turn your energy around and opt for energy efficiency through photovoltaic energy, Endesa provides the solution that will be most suitable for you.