We are indeed living in interesting and turbulent times. Everything seems to be moving at great speed, and more and more significant events are taking place on the world energy scene. Focusing on Spain, our country has advanced by leaps and bounds in the production of renewable electrical energy, especially photovoltaic energy. However, the management of these systems is often not optimal and part of the energy generated is underused.

Need for energy storage


Below, I would like to share two images obtained from redOS, the application of the system operator in Spain:

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It is truly amazing and admirable how the large orange band, representing solar energy, has increased enormously, while the ochre band, representing natural gas generation, has decreased. This represents a resounding victory in the process towards decarbonisation.


After the high prices caused by the energy crisis of 2022, the electricity market has managed to regain good stability, with more affordable energy prices, albeit with a noticeable difference. Previously, the most expensive hours were in the middle of the day (peak), due to higher demand, while the night hours were generally the cheapest (off-peak). In addition, energy tolls were more expensive during peak hours and lower during off-peak hours.


Following the large-scale development of solar energy, this situation has been reversed. Now, the middle hours of the day are the cheapest and even have negative prices (energy production prices), while the night hours are the most expensive, largely thanks to photovoltaics. Of course, this does not happen all year round, and energy such as gas is still needed during the days when the wind or sun cannot provide enough energy, although it is undeniable that there has been a great improvement in just a few years, and there are more and more months with extremely low prices and an energy mix close to 90% emission-free energy.


However, due to this situation, it is of utmost importance to improve grid management and to perfectly match supply and demand, always ensuring grid stability. There is no doubt that further expansion of renewable energy capacity will be necessary, as demand will increase as we electrify the rest of the economy (electric cars, heat pumps, etc.). However, one of the biggest challenges remains the ability to store energy on a large scale in order to match demand with production, secure electricity supply, maintain reasonable prices and use emission-free energy at every moment of the day.

Cold stores as storage

Energy storage remains a crucial challenge for the decarbonisation of the energy sector. Although a number of promising technologies have been developed and are being explored, a fully effective large-scale storage method has not yet been found. Available and potential technologies include lithium batteries, lithium-ferrophosphate batteries, molten salts, hydrogen fuel cells and even sand deposits. Probably, as in many other areas, the solution will not be unique, but a combination of these technologies, applying the most appropriate one for each specific case.


From Articae, we would like to highlight the possibility of using already built systems with a wide storage capacity throughout the national territory as a means of energy storage. We are referring to the cold rooms of various cold industries. In our country we have more than seven million square metres available for energy storage in cold stores (ALDEFE). 


In the case of negative cold storage (-15°C to -50°C), products often have to comply with a maximum temperature regulation to ensure their preservation, but the minimum temperature restriction is not as strict for certain foods. Therefore, one possibility is to subcool cold stores more than necessary during the hours when energy is cheapest and least polluting, which with a reduction of two to three degrees their storage capacity would be 2 GWh thermal. These hours usually coincide with higher ambient temperatures and higher energy demand. Subsequently, the stored energy will allow consumption to be reduced during the most expensive and off-peak hours.


The large amount of solid product stored and the thickness of the insulation in the cold rooms, both in the walls and in the ceiling and floor, turn these rooms into excellent thermal energy batteries. By combining these structures with photovoltaics, energy storage can achieve savings of 15% to 30%.


In addition, there are already thermal cooling batteries, which are widely used by the dairy industry, such as ice water basins. Previously, these ponds were used at night, but with the inversion of the price curve, they now have to adjust their operating patterns.

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Photovoltaic demand management

Hybridising photovoltaic generation with thermal batteries, such as cold rooms or ice water ponds, will reduce photovoltaic surpluses, a common problem in many industries nationwide. The installation of self-consumption systems with surpluses has grown significantly in both the residential and industrial sectors. In many cases, demand does not match solar production, which is bell-shaped, resulting in surplus production during the central hours of the day that must be fed into the grid, while the rest of the time it is necessary to consume energy from the grid. Although there may be compensation for the surpluses, this is small compared to the savings obtained by avoiding the use of energy from the grid. Thus, 20% of the surplus PV production is lost due to the lack of storage systems and administrative barriers for grid feed-in.


The idea of harnessing energy in the cheapest hours (or even for free if it has been generated with solar PV) to store it and use it in the most expensive hours is simple to understand, but not so simple in practice. The demand for cooling depends on many factors, such as working shifts, product seasonality, product rotation, loading and unloading schedules, door opening, and outside temperature, among others. These factors may sometimes be constant, but are subject to variations or disturbances throughout the day, depending on location and season.


In addition, it is necessary to highlight two very important aspects for energy storage: the hourly price of energy and solar radiation for photovoltaic production. Thanks to advances in predictive modelling using Artificial Intelligence (AI), solar radiation predictions are becoming more and more accurate and the amount of energy that will be generated each day can be known with high accuracy. Moreover, daily market prices can be known a day in advance. Add to this the ability to know in advance the loading and unloading schedules of products, production, and other data that is normally known to the property, and AI-powered energy optimisation is possible. By taking all these factors into account, significant savings can be made and energy bills can be reduced, improving the competitiveness of companies. Apart from the economic benefit, this optimisation allows each industry to better manage energy consumption and demand, adapting demand to production rather than the other way around. In this way, it is possible to increase the percentage of renewable electricity generated, reducing the environmental impact and the emissions emitted by the company.


There is no doubt that we face enormous challenges, and meeting them will require collaboration and improvement in all areas of society. Becoming more energy efficient and energy smart will build a brighter future for business and the planet.