Breaking the gridlock

In the race to reduce greenhouse gas emissions, so as to reach the goal of net-zero, the role of renewable energy such as wind and solar has been discussed in earlier articles. In addition to producing renewable energy, its transmission, distribution and storage is also of critical importance. The whole network of transmission and distribution lines is also referred to as a power grid. This becomes even a greater challenge because wind and solar farms are located in remote areas where the old transmission network has not reached. Further, wind and solar energy are not a constant source of power like coal-fired power. Hence, ‘evacuating’ electricity from such places often requires laying of fresh transmission and distribution lines. In addition, the storage of electricity produced from renewable sources is also equally important, because of the variable nature of the energy produced (wind doesn’t blow all the time and the sun shines only during the day). Another challenge is that wind and solar plants are not uniform and can vary from a large farm to small generation units. This also has to be factored in while connecting them to the existing grid.

Grid flexibility, energy storage and microgrids

The three challenges of variability of power, remoteness of plants and the variety of project size can be addressed by grid flexibility, improved energy storage and microgrids.

Grid flexibility can be improved by supply side solutions, better demand management and improved storage. The supply side solutions are basically implemented by the operators of the grid, which involves supplementing wind and solar power with other sources such as hydro power or nuclear power. There are other tools, which involve the operators setting shorter pricing intervals and setting shorter wind or solar power schedules (which means that the wind or solar power scheduled output is set in close time proximity to the forecast of wind or solar output). Other tools involve the use of digital tools in managing dispatch loads and schedules and frequency regulation.

Another way to improve grid flexibility is to improve storage of power through better batteries and pumped storage projects. Pumped storage projects involve the pumping of water to a reservoir at a height during off-peak hours (when electricity demand is low) and releasing it to cascade down with gravity onto a turbine, during peak hours (when electricity demand is high). Molten salts are also used to store electricity and act as batteries. Molten salts are heated to high temperatures and the heat is stored. During peak hours, this thermal heat is used to turn turbines and generate electricity. Molten salts are often used as thermal storage units in solar power plants. The Noor1solar power project in Dubai uses both pumped storage and molten salt plants for storage of electricity.

Grid flexibility can be improved with demand management solutions as well. This is done by providing incentives to consumers to shift consumption to off-peak hours. This involves cheaper tariffs at off peak hours and payouts to consumers willing to reduce demand for periods when supply-demand balancing is most required. There are other digital tools as well that enable appliances to work more efficiently, which helps in smoothening out imbalances.

Another way to get around the complexity of operating large grids is Microgrids. A microgrid is basically a smaller version of the larger grid, which has different energy sources such as solar, wind and biomass as well as storage mechanisms and load management systems. This has the added advantage of lower transmission losses and more flexibility. Microgrids have a great usage in developing countries where large grids are absent and in remote areas where transmission and distribution lines have not been able to penetrate.

Conclusion

Grid flexibility, energy storage and microgrids are an important part of the newly emerging energy infrastructure. These have become important in the transition to a world where renewables such as wind and solar are forming a greater part of the energy mix. Since wind and solar are variable sources of electricity as compared to the old steady sources of coal and gas, and the existing grid was made to transport steady electricity, grid flexibility has become critical.

The writer is Additional Chief Secretary, Department of Mass Education Extension and Library Services and Department of Cooperation, Government of West Bengal