There are various innovative solutions that help meet power requirements through renewable energy generation. In the solar segment, for instance, there are rooftop, ground-mounted, hybrid and floating solar systems. New blends of technologies are also emerging to make renewable energy more reliable as a source of power generation. In hybrid systems, renewable energy sources are blended with each other, with conventional power sources, or with energy storage solutions. Thus, as the demand for renewable energy and its share in the power generation mix is increasing, new innovations are being introduced for better grid integration of these energy sources.
Solar, storage and microgrids
The demand for power has been growing across all consumer segments – commercial and industrial (C&I), residential and agricultural. With more renewable energy generation capacity being installed to meet this demand, a large quantum of infirm or intermittent power will have to be fed into the system. To balance this power, energy storage solutions are needed. Energy storage applications can provide multiple power back-up, frequency regulation and voltage support to the stakeholders. Solar power generation can be complemented with a diesel generator set, an energy storage system, or a combination of both. Energy management systems are typically set up through AC coupling.
A hybrid set-up consisting of solar plus storage can have a wide range of applications in the C&I segment, which include power backup, time-of-use billing, peak load shifting, power stabilisation and improvement in the quality of power. This, in turn, helps optimise energy supply, save diesel, reduce the energy bill and minimise the carbon footprint.
Mini- and microgrid solar systems with battery bank supplies can be very useful for smaller and more independent set-ups. They supply electricity to meet the daytime requirements and charge batteries. These systems include energy management systems and battery management systems. The microgrid set up by SunSource in 2013 at Buddha Public School, in Bahraich, Uttar Pradesh, has 100 kW of installed solar power generation capacity and 300 kWh of lead-acid battery storage capacity. Recently, SunSource has taken up a project for developing solar microgrids on the Lakshadweep islands (1,400 kW) as well as a high terrain project of 2,000 kW in Himachal Pradesh. L&T has also set up a microgrid at its headquarters in Chennai.
Wind plus solar
Wind-solar hybrids offer an opportunity to combine the benefits of wind and solar power. India has a considerable potential for both these sources. The states of Gujarat, Andhra Pradesh, Rajasthan and Maharashtra have a particularly favourable environment for setting up such hybrid projects. The market enthusiasm for wind-solar hybrids has been quite promising, with about 11 GW of tenders issued or planned and about 3 GW of capacity awarded already. The economics of wind-solar hybrids also seems favourable.
While the levellised tariff expected by the market for hybrids lies in the range of Rs 2.60-Rs 2.80 per kWh, the tariff range expected for hybrids combined with energy storage is Rs 3.60-Rs 4 per kWh. These tariffs are expected to decline further as technologies become cheaper over time owing to economies of scale. Hybrids optimise energy generation by leveraging the synergies of two renewable energy sources. That said, even the most optimal blend yields an annual capacity utilisation of 30-40 per cent only. Further, the capex of solar plants is lower than that of wind, but having a solar-heavy portfolio will lead to a greater need for storage during non-solar hours and overall energy generated will be lower. Thus, the renewable energy portfolio in a hybrid should ideally be wind dominant.
One of the major challenges faced by wind-solar hybrid projects is the lack of good sites for projects. Although co-located plants have benefits such as better utilisation of transmission infrastructure, land and balance of systems, these are limited to locations with good wind and solar resource availability. The co-location of wind and solar equipment will also require a single point of grid connection. The transmission network will have its own constraints in handling the extra power being generated from these plants and will require more permissions and approvals. Another challenge is posed by stringent clauses on capacity utilisation factor (CUF) and scheduling requirements. Meeting the power curve demand effectively is also a key hurdle. This is difficult since the solar output is maximum between 11 a.m. and 3 p.m. and the wind output is highest during early morning and evening, whereas the power peak demand occurs between 6 p.m. and 9 p.m. Renewable power generation peaks during the daytime and load demand peaks during late evenings.
Several efforts have been made to address the issues of intermittency, limited hours of supply and low capacity utilisation of renewable power plants to make them more attractive for state-owned power distribution companies. These include a scheme proposed by the Ministry of New and Renewable Energy (MNRE) to sell renewable and thermal power together in a “bundle” to provide firm, uninterrupted electricity supply to buyers. In the past year, the Solar Energy Corporation of India has issued peak power and round-the-clock hybrid power tenders, which has been a significant step in improving the quality of power supply of energy generated through renewable sources.
Apart from this, energy storage is being promoted for balancing variable renewable energy generation owing to its advantages over fossil fuels such as lower operating cost, near-instantaneous response and zero direct emissions. The government has announced plans to launch an incentive scheme for the promotion of new champion sectors with a focus on advanced cell battery storage and solar PV manufacturing in order to make India more self-reliant. The emphasis of this scheme will be on cell manufacturing as it aims to reduce India’s reliance on battery cell imports and substitute it with domestic manufacturing. The government may also come up with a suitable performance-linked fiscal incentive programme to incentivise advanced cell chemistry manufacturing in India.
The way forward
The difference in generation and demand often leads to curtailment of renewables. If excess energy during the generation peak is stored and used during the demand peak, curtailment could be avoided. However, storage systems may lead to additional cost pressures. The demand for energy storage generated by increasing renewable penetration, growth in electric vehicles, and transition to smart grids is expected to drive down battery prices, further pushing the industry towards storage. As per L&T’s outlook, the battery price may drop to $109 per kWh by 2025, as compared to $200 per kWh in 2019. In order to develop a better understanding of the economics related to renewable energy and storage projects, a software system called Comprehensive Market Evaluation Tools for Storage (CoMETS) has been developed to help technology and project developers evaluate and optimise energy storage resources for stand-alone as well as integrated renewable energy applications. Such tools will help in creating more efficient renewable power projects combined with energy storage, providing smooth and reliable power in the years to come.
Based on presentations by
Randeep Bora, Vice President, New Business and Tendering, SunSource Energy; Shaji John, Head, Business Development Domestic and Global Markets, Renewables Business, Larsen &Tourbo; Rahul Walawalkar, President and Managing Director, Customized Energy Solutions India, at Renewable Watch’s Solar Power in India conference