Renewable energy expansion needs an integrated sustainable storage solution, here’s how

Read in Hindi | In our fight against climate change, we are transitioning from fossil fuel energy to renewable energy, as our energy demands keep increasing. However, India's primary renewable energy sources, such as solar and wind, are intermittent i.e. they are dependent on weather conditions. In such a situation, how can we truly rely on these energy sources to provide 24-hour electricity? The answer lies in energy storage. And currently, the batteries, such as lithium-ion batteries, are the most widely known form of energy storage worldwide. Lithium-ion batteries have become a part of everyday life since 1991, powering everything from TV remotes, toys, and vehicles, to serving as backup power in homes. Similar to the way inverters are used in homes, there is an increasing discussion about lithium-ion batteries as storage systems for grid-level storage as well. The addition of storage is crucial for the energy transition towards increased renewable energy sources, as well as grid stability. For instance, at times when solar panels cannot generate electricity, stored energy can keep our cities illuminated. 

However, it's worth considering how many lithium-ion batteries would be required to provide a 12-hour power backup, night-time backup, to an entire town. Though, the cost of batteries has significantly decreased by 97% in the last three decades, establishing a grid-scale battery energy storage system requires substantial capital investment as the amount of batteries needed is significant. A study conducted by Lawrence Berkeley National Laboratory reveals that by 2030, the installation cost for a 1-MW/4-MWh capacity lithium-ion battery energy storage system at grid scale in India is projected to be approximately $103/kWh.

Currently, India relies on other countries for its lithium supply, as per data from the Ministry of Commerce, between April 2022 and January 2023, India imported lithium and lithium ion products worth 18,763 crores ($2.3 billion USD). Although the recently discovered lithium reserves in India may potentially lead to self-sufficiency in the future. Important to note, that lithium mining has significant environmental drawbacks. Specifically, mining one ton of lithium requires a staggering 2.2 million litres of water, contributing to adverse effects such as soil erosion, water depletion, loss of biodiversity, and disruption of ecosystem functions in the mining areas.

In such a situation, the question arises that if not lithium-ion battery, then what?

Different types of storage

There are numerous technologies being worked on as an alternative. In this article, we explore three: pumped-hydro storage, thermal storage technology/molten salt, and sodium-ion batteries.

Pumped-hydro storage

Sanjay Dubey, Principal Secretary of the Department of Energy and New and Renewable Energy in the Government of Madhya Pradesh, acknowledges that there is a need for storage in order to transition fully to renewable energy. However, he expresses his hesitation towards adopting battery-based storage due to its high cost. He says, 

"There is a potential for pumped hydro storage in multiple locations across Madhya Pradesh. There is an ongoing effort to establish such infrastructure. Exploring alternative options is also being considered, though no conclusive statements can be made until successful outcomes are achieved."

Navneet Tiwari, an employee of Narmada Hydroelectric Development Corporation Limited (NHDC), is currently collaborating with the Madhya Pradesh Energy Department on the Sanchi Solar City project. NHDC is setting up a 3 KW solar park, in the initial phase of the project, and then later set up a 5 KW solar park as well.

Tiwari highlights the establishment of an 11.2 GW pumped storage in Madhya Pradesh, which is already underway. NHDC is in the process of developing the Indira Sagar Dam at Khandwa and the 525 MW Pumped Storage Project at Omkareshwar, currently in the preliminary DPR (Detailed Project Report) phase. This project has the potential to generate 1,226.93 million units of energy during peak hours. Peak hours are basically the time of the day when the energy demands increase. This exact time window varies from region to region.  Additionally, another pumped-hydro project is proposed in Pench Valley, Near Chhindwara, Madhya Pradesh, mentions Sanjay Dubey. He adds the tenders have been floated for multiple such pumped hydro projects in the state.

Pumped hydro storage operates as a colossal, enduring battery, utilizing two reservoirs positioned at varied elevations. By harnessing solar energy, water is moved to the upper reservoir during daylight hours, and subsequently released at night to generate electricity. The underlying concept relies on the force of gravity.

The current global pumped hydro storage capacity is approximately 180 GW. Whereas, India's potential for pumped hydro storage, based on the Central Electricity Authority, reaches 119 GW. However, India's current installed capacity stands at a mere  4.7 GW.

Like any storage system, pumped hydro also has its drawbacks, such as its geographical limitations. This technology necessitates specific geographical conditions– like necessary elevation/slope around reliable water bodies– that are not readily available. Additionally, the time and capital investment required to make a pumped hydro project operational is substantial. For instance, the estimated cost for the construction of the Omkareshwar Pumped Hydro Project in Madhya Pradesh is Rs 4,200 crore.

There are other roadblocks as well, like lengthy construction periods, an unsustainable pricing model, and a scarcity of suitable sites with the necessary topography for their efficient operations beyond environmental concerns of displacement and ecological damage. The Ministry of Power drafted certain guidelines to push for pumped hydro-based energy storage.

In addition to Madhya Pradesh, the initiation of pumped hydro storage projects has also commenced in Maharashtra. Notably, an agreement has been recently forged between the Government of Maharashtra and Tata Power to establish a 2800 MW pumped storage project within the state. According to the National Electricity Plan for the year 2022-2032, India must escalate its reliance on renewable energy. By 2031-2032, the country's grid-based energy storage capacity should reach 411.4 GWh. This objective can be met by incorporating a 236.22 GWh storage battery energy storage system (BESS), in addition to accomplishing 175.18 GWh of storage through the Pumped Storage Project (PSP).

While PSP would rely on non-fossil and gravity to generate and store energy, it is essential to note that damming rivers is detrimental to the environment, and ecosystem. There are ways to make hydropower, and storage environment-friendly. However, relying only on PSP for energy storage will be not a smart long-term plan.

Chetan Singh Solanki, Professor at IIT-Bombay, and founder of Swaraj Energy Foundation says “Instead of investing in a big storage solution, it is better to store electricity in small units in a decentralized manner.”  Hence, investing in an energy storage mix i.e. diversifying the storage solutions should be promoted. 

Thermal storage technology: Steam/ Pressurised water

Kailash Cancer Hospital’s canteen, situated approx 30 km from Vadodara, Gujarat, serves at least 2000 meals a day. And, since April 2023, they have been utilising thermal storage technology to store solar energy for cooking everyday meals. The meals are cooked daily as part of the early morning chores, with little to no sun/solar energy availability. The technology is installed by Sunrise Concentrated Solar Power Pvt Ltd. This technology allows for the concentration of sunlight on a specific point, reaching temperatures of up to 1700 degrees, as explained by the CEO of the company, Pranav Gadhia. By heating water, the energy is stored in the form of pressured water by compressing it in a container to generate steam. This stored energy is later used to supply steam for ‘1-2 hours’ during non-sunshine hours.

This technology is currently in the pilot stage in Vadodara. This steam is being effectively used for various purposes including cooking, laundry, and sterilisation. As per our conversations, they can be scaled to educational institutions for their cooking/mess-related needs. Furthermore, the director of Sunrise Solar, Pranav Gadhia, envisions a future where electricity can be generated by rotating turbines through the stored steam. Thereby, converting the concentrated solar energy into electric energy.

Pranav believes that concentrated solar power has the potential to address the intermittent nature of renewable energy. This technology offers grid stabilization capabilities that can significantly contribute to our energy mix. Despite Pranav's disappointment with the government's lack of interest in supporting the research and development of this technology compared to solar PV solutions, he remains optimistic about their efforts and is confident of future success.

Thermal storage technology: Molten salt

In the state of Madhya Pradesh, Dr V K Sethi at RKDF University is experimenting to explore energy storage through Molten Salt. Dr VK Sethi, a retired professor, highlights that this technology involves heating halide salt using concentrated solar power. The heat stored in the salt can provide a power backup for 6 hours, whereas a Lithium-ion battery can only offer 4 hours of backup. Although, there is a significant drawback. India imports Molten Salt from America at a price of $3000 per kg. However, Dr Sethi expresses optimism about producing halide salt within India. He says, “It would drastically reduce the cost to $30 per kg.”

Solar energy is absorbed by molten salts in thermal storage, storing it as heat. A heat exchanger transfers fluid from the high-temperature tank to generate steam for electricity production. The fluid then returns to the low-temperature tank at a lower temperature.

Sodium-ion batteries

Sodium Salt, an essential component of your food, is now being recognized as a superior storage option. Over ten companies worldwide are set to commence commercial production of sodium-ion batteries by 2024-25. India, too, is making significant advancements in this field. AATRAL-ESP, a Chennai-based startup, is actively working on a sodium-ion storage system. The CEO, Subhadra Rajendran, decided to embark on this journey after witnessing the destructive environmental impact caused by lithium and cobalt mining. Subhadra emphasizes the sustainability and eco-friendliness of their sodium batteries, which are made solely from indigenous and locally sourced raw materials. Sodium possesses chemical properties similar to lithium and is abundantly available in our surroundings. Hence, unlike lithium, sodium doesn’t have to be mined.

When discussing the advantages of sodium batteries, Subhadra emphasizes their exceptional safety and cost-effectiveness. She adds,

"Unlike lithium batteries, sodium batteries do not pose any risks of overheating or fire. Moreover, sodium batteries exhibit a broad temperature tolerance, ensuring optimal efficiency in temperatures as low as minus 40°C and as high as 60°C. Additionally, sodium batteries can be fully discharged, enabling users to utilize the entire energy stored within them."

One area where lithium-ion batteries outperform sodium-ion batteries is in terms of energy density. On average, lithium batteries have an energy density of 250 Whr/KG (watt-hours per kilogram), which is significantly higher compared to sodium batteries which usually range between 40 Whr/KG and 160 Whr/KG. Subhadra acknowledges this difference but states, "Through extensive research and development, we are actively striving to boost the energy density of sodium batteries and are optimistic about achieving a major breakthrough within the next few years."

While sodium batteries may not be efficient for lightweight storage in electric vehicles and small devices, they can prove to be immensely significant for grid-scale storage, as well as solar and wind farms. Subhadra enthusiastically agrees, stating,

"The primary objective of our company is to endorse sodium storage as both a grid-scale battery energy storage system and UPS technology. The use of sodium batteries in this context will prove highly advantageous due to their affordability and impressive lifespan of 15-20 years."

Reliance Industries has recently acquired Faradion, a UK-based startup dedicated to developing sodium-ion batteries, for $135 million. Furthermore, Reliance plans to invest an additional $35 million in Faradion to expedite the commercialization of their products, including batteries specifically designed for electric vehicles. 

While closing the conversation Subhadra highlighted, “There are very limited companies working in the sodium-ion battery development field, and we need more companies for effective technology to come through in time”

Conclusion

In the quest for renewable energy, various energy sources are combined to create an energy mix. Similarly, to ensure adequate capacity, it is imperative to promote diverse energy storage technologies. The Energy Storage Roadmap for India, prepared by the India Smart Grid Forum and NITI Aayog, highlights our comprehensive evaluation of various storage technologies. However, it is the constant advancements in lithium-ion battery technology and the fierce price competition that make it the foremost preference for India.

However, if we fail to consider alternative options, we could encounter new challenges in the next 10-20 years, taking into account the environmental harm lithium-ion batteries cause. As we make this transition to combat climate change, we are simply trading one problem for another. We will be facing mountains of waste from discarded photovoltaic cells and lithium batteries in the future. 

Questioning India’s climate mitigation, and renewable energy expansion plans, Chetan Solanki says, 

“We have to understand this from a broader perspective. The way we are increasing the amount of renewable energy in the grid… we have to understand the motive behind this. Are we thinking of foreign exchange (international commitments) or is it to reduce carbon emissions or is it to create decentralised energy generation and strengthen local communities? Unless we understand this, we can’t answer the right questions”

In addition to energy storage, another considerable challenge associated with renewable energy is grid transmission. For an efficient transition to clean energy, and eliminating coal-based energy, the transmission grid must undergo significant upgrades utilizing state-of-the-art technologies and innovative solutions However, implementing these advancements will require a substantial amount of capital investment. In the third article of this series, we will delve into India's preparations to address the transmission-based challenges.

This is the second of three articles series on India’s renewable energy expansion, and storage system. This story is produced with the support of the Earth Journalism Network story grants

Keep reading

• Part One: Sanchi solar city, utility-scale solar system, and the looming storage problem 
• Part Three: India’s Renewable Energy Expansion Posing Threats To Its Grid Stability 

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