Distributed power generation is very important to the power system network. It helps bridge the gap between supply and demand, and increase the efficiency and production of power. Distributed power generation based on renewable sources of energy plays a significant role in the Indian power sector. Distributed renewable power generation systems are units that produce small clean power near the end-consumers. Such systems strengthen the power supply and reduce the emission of carbon dioxide during the process of energy generation. It reduces the loss of energy arising from line losses, enhances voltage stability and provides system security, thereby increasing the quality of power generation. The size of a distributed generation system typically ranges from less than a kilowatt to a few megawatts.
According to the National Research Development Corporation, and its partners, the Council on Energy, Environment and Water, and the Skills Council for Green Jobs, investing in distributed renewables is important for the country. Some of the benefits of decentralised generation are employment opportunities, equitable energy access and distribution efficiency. For instance, more people were employed for installing 3.8 GW of rooftop solar capacity than for installing 26.2 GW of utility-scale solar in the past five years in India. Micro- and minigrids, rooftop solar systems and micro hydroelectric projects generate electricity in remote villages and rural areas, making power accessible to those who need it most. The small-scale nature of such projects also supports the entrepreneurship model. Further, small-scale microgrid systems require a short gestation period, and enable fast and easy capacity additions when required.
By generating electricity close to the point of consumption, distributed renewables can minimise transmission and distribution losses. Almost 20 per cent (some say up to 35 per cent) of the electricity generated in India is wasted or stolen, leading to severe financial distress for distribution companies. This can have implications for the entire energy sector. Recently, there have been several cases where power discoms have delayed or defaulted on their payments, and in a few cases, are even considering renegotiating their existing solar power purchase agreements. Further, as India looks at electrifying transport in a big way, the demand for electricity will become more distributed. This presents a strong case for investing in distributed renewables such as solar-powered charging stations for cell phones and electric vehicles, etc. Distributed generation systems can also reduce the peak demand, and offer an effective solution to the problem of high peak load shortages.
With India planning to add a massive 500 GW of renewable energy capacity to its electric grid by 2030, it is critical to plan what kind of grid architecture will support this level of renewable integration. In places where grid expansion is prohibitively expensive, off-grid renewables are economically viable. In addition, multiple decentralised nodes of power generation enhance grid resilience. In contrast, in a centralised grid, a single failure can take down the entire system, as seen in the 2012 power blackout, which plunged the population of 670 million into darkness.
In distributed generation systems it is easier to maintain power, voltage and frequency levels as compared to a centralised system. They also offer the possibility of combining energy storage and grid management systems with reduced grid congestion. Further, the agricultural sector consumes about a fifth of the electricity generated in India. Agriculture in India largely relies on rainfall and subsidised grid electricity, which is often supplemented with polluting diesel-based pump sets for irrigation. To reduce the reliance on diesel, government programmes such as the Kisan Urja Suraksha evam Utthaan Mahabhiyan ( KUSUM) at the central level and the Suryashakti Kisan Yojana in Gujarat have been launched to provide incentives and subsidies to help farmers transition to solar-based irrigation. Decentralised agro-photovoltaic (PV) systems combine agricultural and solar generation to provide clean energy for agriculture and improve land use efficiency, while creating jobs in the rural economy.
Technologies for distributed power generation and key enablers
Decentralised generation systems are very flexible. They are based on both renewable and non-renewable energy sources. Decentralised generation technologies include reciprocating engines, microturbines, combustion gas turbines, fuel cells, solar PV, wind turbines, biogas and waste-to-energy. The deployment of rooftop solar PV systems has increased significantly in recent years. In distributed solar applications, small PV systems (5-25 kW) generate electricity for on-site consumption and are interconnected with low voltage transformers on the utility system.
Distributed storage has gained momentum as well. For example, behind-the-meter storage business models allow consumers to store the electricity generated by rooftop solar PV power plants and consume it later when needed or sell it to the grid. Also, smart meters, network remote control and digitalisation, IoT, and broadband communication infrastructure are all fundamental enablers of services associated with distributed energy sources.
Role of distributed power generation in the smart grid
Decentralised generation systems are a natural extension of smart grids. On-site decentralised power generation helps in reducing peak loads, thus enabling better system management of the central grid. In the future, both smart microgrids and smart decentralised systems will be able to sell their generation back to the utilities from which they buy the power, thus creating an additional revenue stream. This will help utilities reduce the need for massive investments in building new high voltage transmission lines to carry renewable power from far-off plants to towns and cities. Local solar, wind and biomass generators, fuel cells, and other decentralised generation systems are much more convenient sources of power as they cut down the line losses associated with long-range transmission.
A key feature of microgrids is their ability to seamlessly separate and isolate themselves from the utility during a grid disturbance with little or no disruption to the loads within the microgrid. The microgrid can automatically resynchronise itself when the grid returns to normal functioning, and reconnects itself to the grid, in an equally seamless manner. It also reduces carbon emissions and supports sustainable livelihoods.
In November 2019, Tata Power and the Rockefeller Foundation launched TP Renewable Microgrid Limited with plans to set up 10,000 microgrids in India by 2026. The new unit is expected to provide clean energy to nearly 5 million households, directly impacting the lives of 25 million people over the next decade. The microgrid operator also intends to provide ancillary microenterprise services to benefit communities besides building, owning and operating microgrids across the country.
Some of the important policy initiatives to promote decentralised solar applications have been the Ministry of New and Renewable Energy’s (MNRE) Off-grid and Decentralised Solar Photovoltaic Programme and the Pradhan Mantri KUSUM scheme. The latter is aimed at ensuring reliable daytime power supply for irrigation and reducing the subsidy burden on discoms. Apart from helping farmers save on power costs, solar pumps are expected to help them earn revenue by selling the excess energy from solar plants to the grid. The implementation of PM-KUSUM started in 2019-20, with a target to install 1.75 million stand-alone solar pumps by 2022. The scheme is aimed at promoting the use of solar energy in the agricultural sector. This is expected to be carried out by installing new solar pumps, setting up grid-connected ground-mounted solar power plants and extensively solarising the existing pumps. The guidelines of the scheme were issued in July 2019.
The MNRE also issued draft guidelines in May 2020 for the implementation of off-grid solar power plants under the renewable energy service company model. Central financial assistance will be available for up to 90 per cent of the benchmark cost. Under the programme, off-grid solar power plants of individual size up to 25 kW can be installed in areas where grid power has not reached or is not reliable. Such plants are aimed at providing electricity to government schools, hostels, panchayats, police stations and other public service institutions.
The way forward
To conclude, decentralised power generation close to rural load centres can help address the energy crisis facing rural India. Further, a well-thought-out policy framework for distributed renewables can ensure sustainable and equitable energy access for all.