By Jyoti Parikh, Executive Director, IRADe
In the Indian power system, the challenges of transitioning from fossil fuels to renewables, such as solar, wind and hydropower, are increasing as its share in the grid grows. The capacity from renewables has already reached nearly 43 per cent, with the aim of reaching close to 50 per cent by 2030 and over 70 per cent in the future. As no nature-based renewable energy source (RES) is consistently available for 24 hours, uninterrupted round-the-clock power supply will increasingly rely on readily available storage. There are several energy storage solutions, but at the grid level, battery storage and hydropower are the most reliable and significant. Battery storage is typically used for a few hours, though recent advancements have enabled its deployment at the grid level. However, it faces challenges related to dependence on rare chemicals, which require prospecting, mining, extraction and recycling or disposal after discarding to avoid their accumulation. For many decades, river-based pumped hydropower energy storage (PHES) has been the primary solution, offering reliable energy storage. However, its expansion comes with challenges such as land acquisition, disruption to agriculture and downstream farmers, potential social protests, and most of all, uncertainties due to droughts and floods, which are expected to increase in the future.
Storage systems are critical in the renewable energy ecosystem, with multilateral banks and philanthropic foundations setting up global storage partnerships to drive adoption. National governments are actively promoting storage solutions, domestically exploring lithium and rare elements or forming partnerships elsewhere.
Recently, a more controlled solution has emerged, called off-river pumped hydropower storage (ORPHES), also known as closed-loop PHES. This system consists of two reservoirs at sufficiently different heights, with only one requiring enough water supply to start operations. The falling water drives the turbines, which can be pumped up with other RES in their idle time. One of the reservoirs requires an abundant supply of water initially, after which, the same water can circulate to generate power with 80 per cent efficiency, requiring only the make-up water for evaporation losses. This is a controlled situation, not depending on the vagaries of nature, ensuring reliable water supply across all seasons. As it does not depend on seasons, it can provide a consistent power supply throughout the year and even serve as a baseload source, if needed. It is safer, easier and cheaper to build as it does not rely on naturally flowing water, eliminating concerns about droughts and floods as the stored water is recirculated. Moreover, it relies on domestic resources, without requiring foreign materials or imports, making it more cost-effective. At approximately Rs 4 billion per MW, it is significantly cheaper than river-based hydro plants, which cost Rs 6 billion per MW. Satellite data analysis by scientists at the Australian National University has identified numerous potential sites for this system worldwide. One reservoir can be located near an ocean or river (not necessarily on them), while the second can be situated in defunct mines, lakes, plains, etc., as long as the two reservoirs are at sufficiently different heights.
Globally, the potential for ORPHES measured by satellite data is significant, but suitability must be verified at the ground level. China is currently the most active country in this space, aiming for a substantial capacity by 2030, with 14 GW already in place and plans for 71 GW in the future. The US and Japan currently have 27 and 23 GW respectively. In India, the pioneering 900 MW project was set up by SJVN Limited at Purulia, West Bengal, in 2008. Recently, interest in pumped storage has picked up momentum. Enthusiasm is so high now that even the private sector, which is usually risk-averse, has shown interest by submitting as many as 75 proposals amounting to 92 GW, whose terms of reference are approved. Among these, 44 schemes of 60 GW have completed surveys and investigations. If they reach completion, India can be the second largest country in this technology space. The Central Electricity Authority has prepared the draft guidelines for this segment. This solution aligns more closely with the principles of Atmanirbhar Bharat than other solutions.
Currently, it is being suggested that new renewable energy projects have up to 20 per cent storage capacity. These projects benefit from production-linked incentives and other support measures. However, more support is needed for ORPHES. To support this technology, the Ministry of Power has waived the central or state government’s approval to propose a project. With government support, it has the potential to scale up and bridge the gap between large pumped hydro and shorter-duration battery power. Integrating RES with storage options on a 24-hour basis requires a data-driven approach, artificial intelligence applications and differentiated pricing through active power markets. A reliable and interruption-free power supply is an essential component of India’s economic growth.