Driving India’s renewable energy growth, both solar and wind power are on the path to convergence. Owing to the complementary nature of the two sources of energy, solar-wind hybrid systems are more likely to provide consistent power supply and, therefore, achieve better grid stability. As a result, hybridisation will lead to the optimal utilisation of available resources as well as transmission infrastructure.
With the aim of boosting solar-wind hybrids, the Ministry of New and Renewable Energy (MNRE) recently issued the National Wind-Solar Hybrid Policy. The policy seeks to promote greenfield hybrid projects as well as brownfield expansions of existing wind or solar projects to convert them into hybrid power plants. According to the policy statement, no additional connectivity or transmission capacity charges will be levied by the respective transmission entities for the hybridisation of existing wind or solar projects. Battery storage can be added to the hybrid project to reduce the variability of output power from a wind-solar hybrid plant. Additionally, all fiscal and financial incentives available to wind and solar power projects will be made available to hybrid systems. Among the states, Gujarat is leading on the hybrid power policy front and has released its Wind-Solar Hybrid Policy along the lines of the central policy.
The market for solar-wind hybrids is at a nascent stage and various studies are being conducted to analyse the scope of the technology. The challenge of adding new capacity to existing power plants without an increase in transmission capacity has often been discussed.
A study was carried out by Gensol Engineering to understand the effect of adding solar capacity to an existing wind farm. Three hybridisation scenarios were considered for capacity addition to the 300 MW of wind power at an existing site to analyse the comparative loss in energy, keeping the transmission capacity constant.
The study concluded that an addition of 50 per cent or 150 MW of solar capacity would not cause much overloading of power, with negligible energy loss of 0.04 per cent as a result of the backing down of the plant. Meanwhile, adding 225 MW of solar capacity would lead to a probable loss of energy of 0.33 per cent and a further addition of 300 MW of capacity would lead to an energy loss of only 1.89 per cent. Hence, the backing down of power, which may be necessary due to the limited transmission capacity of the existing power plant, does not lead to substantial energy losses in any of the cases. The benefits of utilising the existing power infrastructure (transmission lines and substations) to its full extent, therefore, clearly overshadow the estimated loss of energy that may result from hybridisation.
Another case was studied to analyse the shadow effect of wind turbines over a solar power plant at a proposed solar-wind hybrid power plant with capacity of 22.5 MW in Jamgoda Hills, Madhya Pradesh. Post the study, 2.87 MW of solar capacity was removed due to shadow impact, and a total of 16.5 MW of solar capacity was proposed. Reduction in evacuation costs with the use of AC and DC coupled systems were also analysed. It was concluded that in a DC coupled system, AC switchgear and cable installation are not required, leading to a 20-25 per cent reduction in costs. In comparison, in an AC coupled system, savings in evacuation infrastructure lead to a 10-15 per cent reduction in costs.
The way forward
With more hybrid tenders coming up, the solar-wind hybrid market is expanding. In April 2018, Hero Future Energies commissioned India’s first large-scale hybrid project in Karnataka, adding 28.8 MW of solar energy to an existing 50 MW wind farm. The Solar Energy Corporation of India has announced plans to issue a tender for the development of 2 GW of solar and wind energy capacity.
A lack of clarification over the selection of technologies under hybrid schemes and regarding the cost of excess energy exported to the grid are hindering the development of the sector. Expensive energy storage technology is also a significant challenge faced by the segment.
Going forward, a robust regulatory framework for metering methodology, forecasting and scheduling, grant of connectivity and sharing of transmission lines for wind-solar hybrid systems is required.
Based on a presentation by Anmol Jaggi, Founder, Gensol Engineering