The power sector is undergoing a transformation with the mainstreaming of alternative energy and the decentralisation of power from centralised to interactive smart grids. Smart grids constantly interact with power consuming devices, while drawing real-time data from them to detect faults, respond to peak demand and sharp variations in demand and supply, improve reliability and reduce usage as well as costs for consumers.
The integration of renewable energy into a smart grid would help the grid become more efficient, predictive and self-healing in case of power outages. A smart grid would be able to immediately transfer the load from the affected area and allow communities to draw from their local renewable energy plant. However, the integration of these sources is challenging, given the variability of power generation from these sources, the location dependence and the unpredictability associated with solar and wind energy.
Since wind and solar power generation is highly dependent on weather conditions, the output of power also suffers from the same unpredictability. The inability to predict cloud behaviour and wind speeds restricts operators from managing the machines as well as the power to be generated. Therefore, it is difficult to schedule solar or wind energy into the grid as it is uncertain whether the committed load will be supplied or not. An increase in the gap between the demand at the grid and the supply from these sources leads to an increase in the cost of power, as the operator often has to draw power from other sources to fill the gap to avoid transmission line outages. Improvements in atmospheric observation and numerical weather prediction models, and stochastic modelling techniques can thus be used for improving the forecast accuracy of renewable power, besides the use of weather forecasts by premier forecasting agencies that enable them to communicate near-accurate data for better scheduling with the smart grid system.
Variability is the variation in output from renewable energy sources despite no uncertainty. Therefore, even if there is no cloud cover predicted and the wind is expected to blow at optimum speeds, there could be a variation in the power generated from these sources. Consequently, voltage fluctuation at the grid during the integration of power that can vary by the second could lead to extensive damage to the equipment and the entire system.
Smart grid systems employ a number of technologies to avoid such variability. Frequency regulation could be done by automatic generation control signals on a per-second basis or spinning reserves could be employed that would come into action as soon as the voltage goes below a specified mark. In addition, voltage support can be used to increase the voltage as required by the system in the absence of optimal generation from renewable sources, or in case of a complete system shut-down, black-start capacity can be employed to restart the system. Reactive power support and power factor controls can also be provided through a combination of switched capacitor banks and power electronic based transmission technologies such as static var compensator and static synchronous compensator.
Typically, renewable sources of power generation are deployed in remote locations with nearly no ready grid access. Therefore, for integration into the smart grid network, crucial transmission resources will need to be developed from scratch. Since the infrastructure is being built specifically for integrating renewable power into the grid, flexible AC transmission equipment such as thyristor controlled series compensators can be installed.
The variability and uncertainty associated with renewable energy can be eliminated with the help of energy storage technologies. A growing trend, energy storage can facilitate smoother integration of renewable energy into the smart grid by allowing the power generated to be stored for days and weeks in the battery, to be drawn from as and when required. However, the high cost of storage currently impedes its penetration in the market. For better integration, large storage would need to be used, which would drive manufacturing and economies of scale for large-scale batteries, leading to lower costs.
The integration of renewable energy into the smart grid network utilises advanced digital technologies that can communicate with and operate the system with higher accuracy and greater control over the input from various sources. However, the challenges need to be addressed and regulatory measures strictly adhered to in order to ensure smooth integration of these sources into the mainstream grid.