Co-locating solar and battery storage for reliable power supply: A techno-economic assessment

As India increases its use of renewable energy (RE), energy storage is becoming increasingly important. Storage allows renewable power to be supplied when it is needed, rather than only when it is generated. At the same time, RE procurement is moving towards more specific supply requirements, such as round-the-clock power, peak-power supply for set periods, and supply patterns that resemble conventional power generation.

As these requirements become more common, it is important to determine how solar power and battery energy storage systems (BESSs) can be combined effectively. Co-locating solar and BESS can make projects more efficient by allowing them to share land and grid infrastructure and use transmission capacity better.

To address this, the Center for Study of Science, Technology and Policy (CSTEP) developed a framework to identify suitable locations and determine the appropriate size of solar and BESS projects. The framework was applied to a 100 MW continuous power supply requirement in Karnataka, considering delivery periods ranging from 2 to 24 hours and different delivery time windows. This helped identify how solar and BESS can be planned together to meet different power supply requirements while balancing three important factors: reliability, cost, and unused RE.

• The most suitable combination of solar and BESS depends on how long power needs to be supplied and when it is required.
• Improving the reliability of supply generally requires more solar and battery capacity, which can increase project costs and, in many cases, the amount of RE that cannot be used.
• Simply minimising unused RE does not necessarily result in better overall performance. Configurations with the least unused energy can provide lower supply reliability at a higher cost.
• Reliability, cost, and the efficient use of RE need to be balanced when planning solar-plus-storage projects.

• Consider unused RE as an explicit factor when designing RE-plus-storage procurement.
• Use location-based assessments to identify suitable sites for co-located solar and BESS projects.
• Design power delivery requirements around actual system needs rather than using a one-size-fits-all approach.