Renewable energy storage systems to power the future

Also in 2020, renewable energy sources made up 37.5% of gross electricity consumption in the EU. This was an increase from 34.1% in the previous year, with wind and hydropower accounting for more than two-thirds of the total electricity generated from renewable sources. In 2020, Sweden was leading the way in Europe, with 60% of energy coming from renewable sources. Following in their slipstream were Finland (43.8%), Latvia (42.1%), and Austria (36.5%).

According to EDF, renewable energy sources currently generate 26% of the world’s electricity and this is expected to be 30% by 2024. In June 2022, a report by the International Energy Agency (IEA) claimed that energy investment around the world would increase by 8% in 2022 to reach $2.4 trillion – the rise coming mainly in ‘green’ energy.

So, what exactly is renewable energy? Essentially, it is energy that is sustainable. Clean, affordable, and reliable, such energy can never run out, unlike non-sustainable sources such as fossil fuels, particularly coal which was the fuel of the industrial revolution.

The main types of renewable energy are solar, wind, hydro, tidal, geothermal, and biomass. Other types are ocean thermal energy and biogas. According to EDF, the amount of solar energy that reaches the earth’s surface in just one hour represents more than the planet’s total energy needs for an entire year. This sounds like the ideal solution. However, how much solar energy we can store and use depends very much on the weather and the time of day, on the solar yield. When the weather is windy, wind is an excellent source of renewable energy, and increasing numbers of wind farms are being built. However, these involve the installation of huge wind turbines which many people consider to be an eyesore, even when placed far out at sea. In addition, many experts are warning about the carbon footprint and end-of-life cost of wind turbines. Of course, wind energy strorage systems are also limited by the amount of wind there is at any one time.

In terms of development, the most advanced renewable energy resource is hydropower, which involves building dams or barriers and having a large reservoir to produce a controlled flow of water that drives a turbine. Hydro energy is not dependent on the weather but it does require large structures and substantial reservoirs to be created.

Tidal energy is similar to hydro energy except that it relies on nature to produce twice-daily tidal currents that are used to drive turbine generators. This means the energy source is not continuous but it is at least predictable. Geothermal energy makes use of the natural heat that sits below the earth’s surface and can be used to produce electricity or heat homes. However, its availability is not guaranteed, with Iceland generating far more of this type of energy than the UK, for example. Finally, biomass energy involves burning organic materials to produce electricity. This approach hasn’t been adopted as widely as the others, but it does present significant benefits in terms of the environment and overall costs because it converts agricultural, industrial and domestic waste into solid, liquid, and gas fuel.

While all the options mentioned above have their advantages and disadvantages, renewable energy storage has been the main challenge to make the most of this alternative energy sources. Renewable energy storage technology will come into its own when it is capable of offering a cost-effective way of capturing renewable energy and releasing it when it’s needed. 

There are essentially four types of renewable energy storage solutions: pumped hydro storage, thermal energy storage, mechanical energy storage and battery-driven energy storage systems.

Involves pumping water uphill, keeping it in a reservoir, and releasing it through turbines. According to the IEA’s Renewables report, over 50% of Europe’s new hydropower capacity in 2025 will come from pumped storage, especially in Switzerland, Portugal, and Austria. The same should apply in China sometime between 2023 and 2025.

Involves storing surplus energy, usually from renewable sources or waste heat, to be used later. Water, sand, and rocks can store thermal energy and the International Renewable Energy Agency estimates that thermal energy storage could reach 800 gigawatt-hours (GWh) of installed capacity by 2030.

Uses gravity or motion (such as a flywheel) to store electricity. Mechanical energy storage can also include compressed air or gas energy storage, which is heated up and expanded using a turbine.

It is widely recognised that the most efficient way to store – and deliver – energy coming from renewable sources is through battery-based renewable energy storage systems. The more battery storage for renewable energy that is available the less there will be a need for the conventional power sources of the past.

Atlas Copco energy storage systems offer silent operation and minimal maintenance, making them ideal for telecom installations in remote locations or on metropolitan construction sites. Operating as hybrid storage systems, they are perfect for balancing out peaks in demand and low loads. These renewable energy storage systems enable users to slash fuel consumption and greenhouse gas emissions by storing between 46kWh and 535kWh of renewable energy and delivering more than 12 hours of power with a single charge.

The most efficient systems using battery storage for renewable energy are based on rechargeable lithium-ion (Li-ion) batteries. These lightweight but high-density batteries have become the preferred option for many reasons, not least the ability of a 1kg Li-ion battery to store 150 Watt hours per kilogram (Wh/kg). A nickel-metal hydride (NiMH) battery typically stores between 60 and 70 Wh/kg and a 6kg lead-acid battery is only capable of storing around 25 Wh/kg.

If we compare Lithium-ion with lead-acid batteries, the first technology has a greater lifespan and better performance for unpredictable and variable loads and under high temperatures. Nickel-metal hydride performance overtime and under high temperatures is better than that of lead-acid batteries, but it is still weaker than what Lithium-ion can offer.