Text written in Basque and translated automatically by Elia without any subsequent editing. SEE ORIGINAL

Accumulation of energy

In order for renewable energies to be able to relieve fossil fuels as an energy source, it is essential, among other things, to develop ways of collecting energy. That is, collect the excess energy and then have the opportunity to use it.

At the CIC energiGUNE research center, several companies are collaborating in the search for a collection form for each energy source. We will learn about reversible dams, the energy collection of compressed air and hydrogen and lithium ion batteries.

Sun, water, wind. These are the new sources of energy that have been developing in recent years. They are slowly taking over fossil fuels. They are clean energy sources and do not run out.

Normally, the energy obtained from these sources is not sufficient to meet all needs, but there is often a surplus. The collection of this surplus to be used when needed has become a goal of energy experts and a concern of CIC energiGUNE. For this, they work with Basque companies that work in the energy field, such as Iberdrola, Sener or Cegasa.

The solutions are as much as the energy sources, i.e. they have found a response for each energy source.

The system of reversible dams is, for example, one of them.

Although it was used a century ago to collect surplus energy produced at night, this system is still in force today.

JESUS GOIRI; CIC energiGUNE: It's very simple. There are two levels, two lakes, one at the bottom and one at the top, which are emptied and filled according to the energy need.

To pump water from the lower level to the upper level, they use the excess energy produced when demand is lower. As demand increases, water is released from top to bottom and energy is generated.

From the point of view of efficiency, this energy collection system is very efficient, capable of collecting a lot of energy, but it requires large places to locate the dams and, currently, there are almost no such places around us.

The operation of the compressed air energy collection is similar to that of the reversible dam.

In such a system, a low speed motor uses the energy generated by the sun or wind to pump air to an underground reservoir. When necessary, air will be allowed to escape through a turbine to generate electricity.

As with reversible dams, the main problem is finding the right places.

JESUS GOIRI; CIC energiGUNE: In order to be economical, they require a large collection volume, which can only be achieved by making them underground. For example, evacuate a salt pit where compressed air is introduced into the aquifer(s). Old gas fields could also be used to collect energy by means of compressed air.

The location of solar installations is also a problem, as they require extensive calendar areas for installation.

Sener has built the first plant in the world that combines the technology of the central receiving tower with the thermal collection of molten salts in the town of Fuentes de Andalucía, Seville. This configuration guarantees an electricity production of 15 hours without sun.

distributed over 185 hectares, 2,650 heliostats—mirror panels—have been installed. In the center of all the panels there is a tower to collect solar energy. The mirrors reflect the solar energy and direct it to the receiver at the top of the tower. The salt crystals contained therein are heated to accumulate above 500 degrees in the tank below.

When power is required, the salt heat is removed from the reservoir. As it cools, it generates steam, moves a turbine, which moves the generator that generates power.

This solar plant can supply electricity to 25,000 homes.

Solar energy is still very expensive, as the investment required in infrastructure is high.

JESUS GOIRI; CIC energiGUNE: Solar plants are still relatively small compared to conventional energies, but they are gradually achieving modules of 50 megawatts, which together reach 200 megawatts. The main problem is the area that is needed, but the world is very big.

Cost is also a major problem for the most popular collection system, i.e. batteries.

There are two types of batteries: hydrogen and lithium ion. In the former, hydrogen is collected for later use in the generation of electricity.

With the surplus of energy produced during the day, hydrogen is obtained by electrolysis and accumulates in bottles. When energy is needed, it is used.

JAVIER PATIÑO; CEGASA: In the hydrogen battery, hydrogen is introduced on one side and oxygen on the other side, and an intermediate reaction is carried out. Leaving water aside, the electrons are separated from the water, and these electrons produce electricity.

This energy collection is used in places where the voltage must be guaranteed; if the electricity is interrupted, the batteries are automatically put into operation.

In lithium-ion batteries, energy is accumulated or released through electrochemical reactions that lead the electrons to the anode and cathode where they are connected to an electrolyte.

JAVIER PATIÑO; CEGASA: If you have both positive and negative terminals, and you put a charge or a flashlight in between, the ions will naturally flow from one side to the other, and at the same time, the electricity will also flow from one side to the other; these are the ions. This is how it is discharged. For charging, we put a voltage on the anode and the cathode. With this voltage we carry out the reverse process: we force electrons to go from one side to the other, as well as lithium ions. That's how we charge the batteries.

Lithium batteries are used in mobile phones, computers and/or electric cars.

The commitment to renewable energies makes it essential to develop energy harvesting systems that guarantee the supply of electricity even when energy is not produced.

JESUS GOIRI; CIC energiGUNE: The first solution is to reduce this type of energy as much as possible. But it will undoubtedly have to be linked to a type of accumulation.