In the face of rapidly escalating climate change, the potential of renewable energy shines as a beacon of hope. Rising temperatures, extreme weather events and environmental degradation have made it clear that the shift to a sustainable energy system needs to happen as soon as possible. Clean energy sources such as solar, wind, hydro and geothermal – which produce little to no direct carbon emissions – are giving us a chance now to address the root cause of global warming and make it possible to build a sustainable future.

However, this path is not without its challenges. To harness the full potential of renewables, we must address the issue of renewable energy intermittency.

How Energy Storage Fits into the Picture

The cost of renewable energy technologies has dropped significantly over the past decade, now being the cheapest power option for most parts of the world. Up till a few years ago, renewable energy technology was prohibitively expensive, but if we are to make our 2050 net zero ambitions a reality, renewables would need to provide up to 90% of the world’s energy, led by wind and solar power.

However, wind and solar energy sources are notoriously variable, ranging in power output based on the weather conditions at any given time – low wind or cloudy skies mean less energy is generated. Power systems are not equipped to handle this level of fluctuation. Sending more energy than the grid can handle damages transmission equipment while insufficient energy supply causes power disruptions that can seriously affect vital infrastructure and services, such as traffic control and healthcare equipment.

To avoid this, energy grids must be actively managed to ensure a steady balance between power supply and demand; when demand changes, operators adjust the supply of electricity flowing into the grid. Here is where energy storage technologies can support intermittent renewable energy sources; when energy supply is greater than demand, excess energy can be stored for future use, and when demand is greater than energy generation capabilities, that stored energy can be tapped to cover the difference.

Exploring Energy Storage Technologies

Coal, oil and gas store a certain amount of energy in them that, when burned, is released in the form of heat (this process is also the one that releases greenhouse gasses into the atmosphere). This heat creates steam, which is used to drive massive electricity-generating turbines.

When developing energy storage technologies to support the large scale deployment of variable renewable energy, we are exploring ways to store excess energy during peak energy generation times, and release that energy when electricity demand is high. This needs to be done with minimal harmful emissions and byproducts released into the environment. Some innovative energy storage systems being developed are:

Mechanical Storage

Simply put, mechanical energy storage systems take advantage of kinetic or gravitational forces to hold energy in place until it is needed again. There are two main methods being tested in mechanical storage: flywheel and compressed air.

In flywheel energy storage, a large mass, or rotor, is rotated to high speed with excess electrical energy. When power fluctuates or is lost, inertia allows the mass to continue spinning and the resulting kinetic energy is used to generate electricity. While this technique is highly efficient with fast response times and a long lifespan, the density of energy that can be stored is low, making it more suitable for short-term applications.

For compressed air energy storage, large amounts of ambient air or gas is compressed and stored under pressure in an underground cavern or container. When electricity is required, the air is heated and expanded again, providing the force needed to drive electricity-generating turbines. While the technology has large storage capacities and is able to provide longer operation times, the initial investment needed to set these stations up is high in terms of cost and geographical complexities. However, compressed air energy storage holds a lot of potential to support the clean energy shift, especially because of its large storage capacities. Because of this, we are already seeing this technology being implemented on a large scale.

In California, USA, a 500MW advanced compressed air energy storage facility is being planned, with investors already signing years-long power purchase agreements, some worth up to USD1 billion. The project, by Hydrostor, will send compressed air through a shaft into underground caverns that are initially filled with water. This water will be pushed up into aboveground reservoirs and when power is needed, the water from the reservoir will be released, driving stored air up to be used in energy generation. The project also reduces system inefficiencies by capturing latent heat produced during the storage process to supply the heat needed to release the compressed air.

Battery Storage

Battery storage, or electrochemical storage, works by converting chemical energy into electrical energy and vice versa. For large-scale energy storage, lithium batteries are the most commonly found chemical batteries as they tend to work more efficiently, charge up quicker, weigh less and last longer than other battery options.

While battery storage may have smaller storage capacities than pumped hydro, they are far easier to construct and deploy. For this reason, lithium-ion batteries are the most popular energy storage option today, holding more than 90% of the global grid energy storage market.

For wide scale use, battery storage can be a little costly upfront, especially for homes and small businesses, and may require regular maintenance that involves technical skills. However, those with the necessary resources, such as energy companies and large corporations, are already investing in this technology to safeguard their power systems.

In Malaysia, national utility Tenaga Nasional Berhad (TNB) is tapping on that opportunity with its massive 65MW Battery Energy Storage System (BESS). The system will function at over 85% efficiency and will help regulate the frequency of electric current running through the grid, provide voltage control and improved power quality, and support the integration of renewable energy throughout the grid. More recently, Sarawak Energy Bhd launched a pilot 60MW battery energy storage system (BESS) to support critical grid services as well as optimize generation assets to minimize carbon emissions associated with coal power generation.

As the most readily available and advanced energy storage technology now, battery energy storage will be key to enabling the integration of renewables for the energy transition.

Thermal Storage

In thermal energy storage solutions, excess electricity is used to heat a medium such as molten salt, sand, water or metals. The heat stored in these systems can be used when needed, either directly as heat energy, or indirectly, to generate electricity.

Thermal energy storage has a number of benefits – first is that the storage tanks themselves can be filled with a variety of easily accessible materials. Thermal systems can also store more energy per unit volume compared to other batteries, and are uniquely long-lasting with little environmental impact. However, while the efficiency for storing and releasing heat energy is high, the efficiency drops when thermal energy is used to generate electricity. Thermal storage systems are also prone to energy leakage and can lose its stored energy over time.

While the technology is not mature yet, it has immense potential to drive the clean energy transition. Global heat production is responsible for a 39% of energy-related carbon dioxide emissions, so thermal energy storage could go a long way in helping us meet our emission reduction targets. Countries like the US and China are picking up on this and conducting wide-scale research and development into the technology – already, a 600,000kW molten salt thermal energy storage project is in the works in Qinghai, China.

Pumped Hydro Storage

Pumped hydro storage involves two reservoirs: an upper reservoir and a lower reservoir located at a higher altitude and lower altitude, respectively. The greater the difference in elevation between the two reservoirs, the more energy can be stored. When there is an electricity surplus, water is pumped from the lower to the upper reservoir. When there is a shortage of electricity in the grid, the water from the upper reservoir is allowed to flow back down to the lower reservoir, passing through turbines that go on to generate electricity.

Because the concept is simple enough, pumped hydro energy storage is easily scalable according to storage needs – from small-scale installations to massive energy storage facilities. In the US, pumped hydro is responsible for 93% of all utility-scale energy storage.

On the flip side of this technology’s potential to store massive amounts of energy is the high startup cost and the threat to aquatic life. However, pumped hydro is still a very viable option for energy companies and countries looking to boost their energy storage capabilities, and scientists are constantly finding ways to mitigate harm on the environment.

In recent developments, India will see the construction of two new pumped hydro storage facilities by Tata Power, with a combined capacity of 2.8 GW. In China, General Electric recently delivered on its contract to supply four 300 MW pumped storage turbines and other equipment for a 1.2 GW pumped hydro plant, which is now fully operational.

Working Together for a Sustainable Energy System

While each energy storage method has its own strengths and downsides, the unique characteristics of each system are able to complement each other to create a reliable and sustainable energy grid. Battery storage, although costly, can provide up to a few hours of energy as the most effective and readily available solution, followed by thermal storage, which would be able to provide enough energy for longer hours up to a couple of days. Then, with its massive energy storage capacities, pumped hydro storage would be able to provide energy for long-term durations.

Crucially, efficient energy storage and release systems will allow us to increase the presence of variable renewable source in the energy system and phase out our reliance on fossil-fueled power. Even beyond that, sophisticated energy storage systems also reduce energy generation costs as well as enhance grid reliability and energy security by decentralising energy generation and distribution, and providing a constant supply of power.

From a financial standpoint, besides creating jobs, widespread energy storage and renewable energy deployment will greatly benefit economic growth. On top of the economic benefits rippling from energy storage and renewable energy investments, increased energy independence also bolsters national security, safeguarding our future. With further advancements in energy storage technology, along with markets of scale, these solutions will likely pave the way for widespread renewable energy penetration and a successful energy transition.

Malaysia is one country that is taking the potential of energy storage seriously.

Malaysia is one country that is taking the potential of energy storage seriously. In its National Energy Transition Roadmap (NETR), the country has outlined several flagship energy storage projects under its Responsible Transition (RT) plans, such as a 2500 MW hybrid hydro-floating solar PV plant that will be developed at Tenaga Nasional Berhad (TNB)’s hydro dam reservoirs. This project innovatively uses existing hydro infrastructure to reduce investment costs and other technical challenges involved in building a new storage facility. The Malaysian Ministry of Natural Resources, Environment and Climate Change and the country’s Energy Commission will also be overseeing the development of a utility-scale energy storage system to enable higher penetration of intermittent renewable energy throughout the country.

Accelerating the Energy Transition

It’s true that energy storage is the perfect solution to the challenges we face in phasing out fossil fuels and phasing in renewables on a large scale. However, as of now, this is easier said than done. To get on track with our net zero emissions by 2050 goal, grid-scale battery storage needs to grow significantly. While energy storage technology has evolved in recent years due to the pressure to integrate renewables in our energy grid, achieving the scalability and cost reductions needed for wide-scale renewable energy deployment will require further investments, research and collaboration.

Flagship projects such as Malaysia’s 2500 MW hybrid plant and utility-scale energy storage plans are a big step in the right direction for the energy transition; the country intends to achieve 70% RE installed capacity by 2050. Testing the waters of energy storage now and developing innovative solutions will only accelerate the rate at which renewable energy can be incorporated into the grid on a large scale, allowing a successful phase out of coal-fired power. Besides strengthening and making the energy grid more flexible, these green projects will also enhance Malaysia’s competitive edge and catalyse growth in areas such as green mobility and green cities.

The realities of climate change are stark and demand immediate action from businesses and governments. Today, investing in energy storage solutions is not just a choice but a necessity to mitigate even more devastating impacts of climate change. At this juncture in our energy transition, opportunities to invest in renewable energy technologies are our chance to right past wrongs while still enjoying good returns – and if we intend to secure a sustainable future, it would be wise to strike while the iron is hot.