Raychem RPG: Selecting the Right Energy Storage Systems for Solar Projects

Mr. Ashish Kumar, Lead Energy Storage, Raychem

Ministry of New and Renewable Energy (MNRE) has set a target of 175GW power to be generated from renewable sources by Year 2022. Renewable sources, especially solar and wind due to its intermittent nature require resiliency at both transmission and distribution level to ensure smooth integration and operation on the grid. Recently, plan released by Power Grid Corporation of India (PGCIL) entitled ‘Green Energy Corridors’ highlights topics such as Intra/Inter State transmission system strengthening, need for flexible generation, establishment of Renewable Energy Management Centre(REMC), forecasting etc. to address intermittency and variability aspects as well as grid integration issues of large scale RE generation.

There are potential problems associated with large scale integration of RE generation such as transmission and distribution congestion, transmission equipment deferral, need for spinning reserves, need for ancillary services (frequency regulation, voltage and reactive power support) and ramp rate control. We believe from global experience that energy storage system (ESS) when designed and implemented at various levels of grid can mitigate the problems mentioned above. Countries like USA, Canada and Germany etc. have already started with multi-megawatt installations of these fast responding, flexible and remotely controlled energy storage systems for applications such as frequency regulation, transmission support, ramp rate control and peak power shifting etc. on their grid.

The electricity cannot be effectively stored in its own form. It can be converted into another form that can be stored and converted back to its original form when needed. There are various ways to store energy. Common examples are electrochemical energy (batteries), mechanical energy (flywheel, compressed air), potential (pumped hydro), thermal (molten salt), chemical (hydrogen, synthetic natural gas), electrical (capacitor, magnetic fields). From an electrical standpoint, these energy storage methods act as load when energy is being stored and generation sources when energy is released.

The energy storage technologies can be further classified based on the application it is suitable for-

  1. UPS support – The role of UPS is to provide emergency backup in case of loss of main power to bring another standby power source online or to properly shut down the protected The power and energy rating of these systems are relatively small.
  2. Grid Support – The primary function of these systems is to make the grid more reliable and The power and energy rating varies with the technology.
  3. Energy Management – These are large scale applications of storage which supports the baseload generation and reduces usage of peaker

Energy storage is not new in India. Lead acid cells are widely used in residential sector for UPS and back up applications. Pumped hydro has been used for bulk energy time shift and energy management by power producers. Li-ion and flow batteries have got a lot of traction in the recent years due to steep decline in cost and advancement in technology. Li-ion batteries are more ideal for high power and short duration (15min to 4hour) applications such as frequency regulation, RE Integrations etc. Flow battery which is relatively new but with higher cycle life is ideal for long duration application (>4 hours) such as energy shifting. With the recent steep decline in Lithium Battery prices , we have seen a lot of ongoing/up-coming installation of battery based energy storage system with Li-ion batteries. In Lithium Ion mostly Li-NMC & Li-LFP technologies are leading the energy storage market and most of the key battery manufacturers have announced GWh scale expansion plan to cater the growing need. The important parameters of batteries that play an important role is technology adoptions are DOD, Cycle Life, Efficiency , Degradation , Self -Discharge , Foot-print , O&M cost etc. Further, for solar projects beside the battery technology the design topology of the project ie. AC Coupled, DC Coupled or Hybrid Coupled also play an important role in overall optimization of the project . Conventionally AC Coupled has dominated the energy storage market but in recent a few years DC Coupled design because of its unique advantages have created a lot of traction in the market.

Mr. Kapil Kumar, Head – Solar Technology, Fortum

India has an ambitious plan of 175 GW renewables by 2022, main challenge in achieving these targets could be the ability of grid to undertake renewables, there we believe storage has a key role to play . We have seen that during the last few months many solar + storage tenders have been released and many more large scale tenders are also expected in the upcoming years. So it becomes very important to select the right technology to build sustainable and profitable projects.

Selection of the storage system depends a lot on the application and requirement. Storage system for a fast response frequency regulation would be different from the storage system of energy shifting. There are various technologies available in the market each having its own advantages and disadvantages. Selecting the right battery application, designing an optimized system and operation strategy can be the difference between the make or break of the project. For the storage system coupled with solar projects, We do see that a DC-coupled system has certain advantages, because of its ability to capture clipped energy and reduce balance of plant costs due to the shared bi-directional inverter and the evacuation infrastructure. However, it does come at the cost of reduced flexibility in charging. Important parameters to be evaluated between different energy storage systems are capacity & power, depth of discharge, life cycle of batteries, round trip efficiency, storage system components life and warranty. While choosing the manufacturer it is also important to evaluate their track record and bankability in the long run. Apart from initial capex, O&M cost over project lifetime and after sales service are equally important criteria for the selection of manufacturer.


Mr. Amit Beriya, DGM – Energy Storage & New Products, Amplus Solar

Battery energy storage systems are gradually becoming viable for multiple applications in integration with Solar PV plants. In a developer model, sizing as well designing system becomes very critical for project viability. Although battery is the major cost component in an energy storage system, but the battery inverter, balance of plant and system controller plays a very critical role in performance. Battery system is versatile in

nature and hence the system size and design depend on the end application it is meant to serve. For example, if the application of battery system is to provide site power during grid outage a battery inverter capable of forming an island grid should be used whereas for an energy shift application cost of battery inverter can be saved by using only an On-grid battery inverter. With the right selection of the major components of a battery system – battery, power conditioning system (battery inverter) and the system controller, an optimized storage system can be selected to increase the commercial viability.


Mr. Sagnik Ghoshal, BD – Energy Storage, Subhasree Projects Pvt Lt.

As a turnkey Solution provider, Subhasree has to often work with the customers to select the right make and size of the system. This not only affects the overall working and usability of the solar solution as a whole, but also affects the economics of the system to a large scale.

The question we often ask our customers to ask when choosing products is – What are you looking to achieve out of the system being installed? If the answer is Energy Cost Reduction, it is usually a fine balance to obtain between the largest battery system that can provide you the longest solar storage and the overall economics of the project evaluated over a period of time. If the answer is Energy Backup, care must be taken to allow for the best systems and components to allow for the most reliable solution with the least after-commissioning support. We use our own energy monitoring platform to provide the customer near real-time updates regarding system status, battery management, remote system control, etc.

The primary areas of concern for any turnkey solution provider like ours is to ensure that we have the right partners, access to proper engineering assistance, robust system components and materials. Our partnership with RPG Raychem gives us access to their engineering expertise to provide the customers with the best, most- sustainable, value solution.




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