Renewable energies

The formula for obtaining maximum performance and flexibility from renewable energies is to apply intelligence to consumption curves. This makes it possible to shift and adjust them as much as possible, and to integrate massive storage mechanisms to reach the last part of the curve, which are essential if a high penetration of renewables is to be achieved.

Fuels, whether solid (wood, coal), liquid or gaseous, are relatively easy to store and transport and can be managed when they are needed. In this sense, they are quite friendly. Electricity, on the other hand, has a particularity: it has to be consumed at the moment it is produced or it would be lost, dissipated.

Of course, this statement is an exaggerated way of expressing the great conflict of electricity generation, which needs to continually adjust production to demand, avoiding the loss of surpluses. Fossil fuel or hydroelectric power plants are used to do this when more energy needs to be added to the system on a discretionary, incremental basis, and renewables and nuclear have no scope to do so.

Electricity is a source of development, indispensable for many of the technologies of the future (electrification of transport, domestic appliances, heat pumps, etc.). But there is a problem: electricity generation currently accounts for 40% of global CO2 emissions. The technologies that appear to be key to providing more environmentally friendly solutions in the future depend on electricity, and the bottom line cannot exclude the emissions produced by the generation of this energy, which is still largely dependent on coal and gas (China, India, Germany, Australia and even Spain).

Electricity systems need to articulate a generation mix to maintain a balance in availability, including all types of power plants, fossil fuel, nuclear and renewables (including hydro).

The most desirable solution, from an environmental point of view, is renewable energy sources (in the electricity production process they do not generate CO2, which causes the greenhouse effect) and also from economic considerations (we do not have to pay for air and sun, as raw materials, as we do for oil and gas, although they also have a cost for their integration into the distribution network).

But this option has a hitherto insurmountable drawback: the wind blows when it is needed, not when it is needed. And the sun can become cloudy and certainly withdraws at night, precisely when electricity is most needed for lighting. Statistical estimates can be made of the hours of daylight and wind per year, to decide the most efficient sites, but assuming in any case that generation is intermittent and subject to factors that are impossible to control.

The formula to obtain maximum performance and flexibility from renewables is to apply intelligence to consumption curves, to shift them and adjust them as much as possible, and to integrate massive storage mechanisms to reach the last part of the curve, which are essential as a high penetration of renewables is sought.

The solution must be batteries or hydrogen. Batteries that store the surplus at times of peak production to distribute it when it cannot be generated. Or apply that excess electricity production to obtain hydrogen, which becomes a storable energy source, with various possible uses.

Battery technology is one of the great challenges for science and engineering. The three people who developed the lithium-ion battery, the basis for today's development of all kinds of mobile devices, from a lightweight smartphone or wireless headphones to electric cars, have just been awarded the Nobel Prize in Chemistry.

Stanley Whittingham, a British scientist, laid the foundations of research using lithium metal to make a battery that had a tendency to burn and explode. The American John B. Goodenough tried different chemical elements to make the cathode (negative pole) with lithium oxides and ions. And finally Japan's Akira Yoshino got the materials right to design a powerful, rechargeable battery that was viable for commercial exploitation, and was recognised as the inventor (and patent holder in 1983) of the technology that is still in use today.

The next phase is to scale up the capacity of the batteries, to charge, conserve and manage the amounts of energy that can cover the needs of industries and population centres for certain periods of time.

To do this, as Yoshino, who is now committed to improving batteries for the electric car, points out, it is necessary not only to find new solutions in materials and battery technology, but also to rethink strategies: "The solution will not come from the battery industry alone, but from the mix of other technologies such as the artificial intelligence, internet of things... When properly combined, they will provide the natural solution.

It should be emphasised that the operating times of stored energy devices that we are used to are misleading: a mobile phone can be in use for a whole day because the times when it is at full capacity are spaced out. With continuous demand it would last a few hours. A car with a combustion engine can usually be refuelled every one to two weeks, because daily use is also limited to relatively short periods. When you go out on the road for a long trip, you usually have to refuel after six to eight hours of driving...

The generic key to meeting these needs is to find a balance between the energy storage capacity (of whatever type), its duration in use according to the consumption requirement and the capacity and speed of recharging the system.

There are proposals to develop the flow battery, based on two electrolytes with different chemical compounds and separated by a membrane, which exchange ions in an attempt to balance their state of charge, allowing electricity to be alternatively introduced or extracted.

Another option is to continue exploring the possibilities of the current lithium-ion model. Or to look for formulas to replace the elements that make up the process with other materials that improve the efficiency of the process and do not depend on lithium and cobalt, which limit and make it more expensive. Cobalt, a controversial raw material, comes mainly from the Democratic Republic of Congo. Lithium, the lightest metal, is obtained from brines and the largest reserves are in Chile, Argentina, Bolivia and China. The competition is open.

Spain's role

Finding new mass storage solutions for electricity requires a combined effort of interdisciplinary teams combining laboratory research on materials and chemical processes, engineering, design and applications.

In Spain, there are companies researching options related to both replacing current battery materials, using lithium-sulphur and lithium-air combinations, and nanomaterials based on graphene. Graphene is already used in lithium-ion batteries to make electrodes, although the more ambitious goal is to develop a new type with graphene-polymer cells. Going one step further, research is underway in Spanish laboratories on an electroactive graphene nanofluid, which, being a liquid, could be refuelled in a similar way to how petrol stations work.

Experts highlight the paradox that, although Spain is a leading car manufacturing country, it has no capacity to manufacture the batteries needed for electric cars. A key element for the future of the industry.

The development of mass electrical storage, in order to bring renewables to maximum use in the energy mix, takes on an even greater perspective of interest.