The massive deployment of intermittent renewables to achieve the decarbonization targets set out in Paris Agreement by 2050, is arising power management concerns while integrating with the power system due to the variability and intermittency of their renewable energy sources. The implementation of energy storage systems will lead to more efficient energy management system since the generation will be decoupled from its final use, allowing a higher penetration of renewables, decentralizing the energy generation and empowering final consumers to define their own model of consumption.
To accommodate such intermittent power generation into the power system, it’s necessary to use any back-up system able to meet the energy demand independently on the availability of the renewable energy sources
To do it possible there are two different alternatives, either by using conventional power generation plants depending on fossil fuels, or by incorporating energy storage systems within the renewable energy system. Those storage systems allow intermittent renewables to provide energy as stable as conventional power plants and to decouple the energy generation from its final use, flattening the renewable power generation curve and minimizing the use of fossil fuels to meet the actual energy demand.
The inconsistency of power supply using intermittent renewables has strongly conditioned the penetration of renewables in different geographies due to the impossibility to properly manage the power system to the actual supply and demand of energy thus, consequently, more than 1% of the annual installed capacity of wind and photovoltaic is curtailed and not allowed to dispatch electricity at the delivery points, representing tens of TWh wasted worldwide every year .
However, to reach the global energy transition and decarbonizing targets set out in the Paris Agreement, a higher penetration of renewables is requested to achieve carbon neutrality by 2050 expecting an exponential growth of 300% in the electricity generation sourced by renewables , from 25% to 86%, reaching up to 40,500 TWh/year of electricity generated by renewables (see Figure 1).
Hence, the implementation of energy storage systems is crucial to make it happen
The development of these storage solutions must be efficient, sustainable, and completely aligned with the final consumers needs in terms of energy, providing electricity, heat or both, and in terms of costs. These storage technologies not only enable improvements in consumption levels from renewable energy sources, but also provide a range of technical and monetary beneﬁts to end-use consumers since they will be empowered to accommodate their energy needs to the most economic rate available.
Such empowerment is enhanced to an extent by integrating self-consumption solutions, generating enough energy to consume and store energy simultaneously when the primary renewable resource is available. Under this scheme, consumers increase energy resilience for their daily needs and become ‘prosumers’ since they produce, at least in a certain %, their own energy consumption.
However, different energy sources are likely to be stored but not all of them are as cost effective and operational for end-use applications as electrical energy. A wide array of storage technologies is available in the market to provide integrated and hybrid generation and storage solutions using 100% renewables resources
Electricity can be easily generated, transported and transformed but it cannot be stored as such, so it needs to be transformed into other types of energy such as thermal, chemical, mechanical, potential or kinetic. The most relevant storage systems used at commercial scale are:
- Thermal Energy Storage (TES): converting power to heat using materials specifically developed for this purpose such as heat transfer fluid (HTF) or phase change materials (PCM).
- Battery Energy Storage (BES): storing electricity in chemical compounds capable to generate electricity charge. Depending on the compounds, the technology used to charge/discharge energy may vary in terms of cost and performance.
- Fuel Cells: it’s a continuous chemical storage system. The most common application uses hydrogen as fuel.
- Hydroelectric Pumping: it’s the most efficient storage system for very largescale applications.
- Compressed/Liquid Air Energy Storage (CAES/LAES): using electricity to compress or liquefy air, reverting the process to recover power when requested. It’s also used for large scale applications.
- Supercapacitors: storing large amounts of electricity through electrostatic charges with no chemical reactions.
- Flywheels: it’s a mechanical storage system consisting of a metal disc that starts to spin when a torque is applied, so it converts electricity to kinetic energy.
Different technological approaches pursuing the same target: decarbonizing the energy matrix to reach carbon neutrality through renewable resources
The selection of the most appropriate technology will depend on the volume of energy they need to manage (large or small scale) and the services they must deliver to the final user (response, inertia, frequency/voltage control, etc). Considering this criteria, the following classification can be considered:
- Behind the Meter (BTM): Applications that happen on the ‘energy user’s side’. Most of the BTM applications are still grid-tied and maintain a connection to the utiliy to ensure energy supply under any circumstance.
- Residencial: commercial buildings and/or residential dwellings, providing reliable electricity and/or heat supply in existing or planned buildings at places with or without a grid connection.
- Industry: implementing integrated energy solutions (heat and/or electricity) to decarbonize any industrial process, getting independence from fossil fuels
- Front the Meter (FTM): Applications that happen on the ‘utility side’ and generate directly for the grid.
- Utility scale storage: Storage applications adapted to high volume of energy generation such us wind farms, solar complex, conventional power generation plants, etc.
Storage will definitely transform the power sector since it’s the only pathway to decarbonize the energy matrix through renewable resources. Generation and end-use consumption models will change, due to the decentralization of the power generation and the involvement of consumers (at any scale) in their own energy supply.
This empowerment of final consumers through renewables and storage applications, together with the effective energy management systems that incorporate these elements, will lead to a new era in the energy market, increasing the use of renewable energies, reaching lower electricity costs and relieving stress on the electric transmission and distribution system. Welcome to the ‘storage age’.
 Too much of a good thing? Global trends in the curtailment of solar PV, https://doi.org/10.1016/j.solener.2020.08.075.
 International Energy Agency. 2021. Net Zero by 2050: A Roadmap for the Global Energy Sector.
 IRENA (2019), Global energy transformation: A roadmap to 2050 (2019 edition), International Renewable Energy Agency, Abu Dhabi. https://www.irena.org/publications/2019/Apr/Global-energy-transformation-A-roadmap-to-2050-2019Edition