Flexible power plants are electricity generation facilities that can quickly adjust their output in response to changes in electricity demand or fluctuations in renewable energy sources. These generating stations are designed to accommodate fluctuating demands for electricity and to balance out the intermittent nature of renewable energy sources. Increased use of solar and wind power, for example, has prompted utilities to seek more adaptable power facilities. The amount of energy produced by renewable sources such as solar and wind can shift based on factors like the time of day and the weather. To prevent instability and blackouts, the electrical grid needs to strike a balance between supply and demand.

Importance of flexible power plants

Load balancing, frequency responsiveness and voltage response are the three primary services that contribute to the reliability of a power grid. Some of these functions can currently be performed more efficiently by renewable sources coupled with battery storage than by a traditional power system. For instance, renewables may provide frequency control by reducing or storing power production, and they can also adjust reactive power (and hence voltage response) even while not providing real power. As more traditional power plants go offline, the need for a quick frequency response service increase, and batteries alone can currently perform frequency response better than conventional sources.

The problem is that the available capacity of dispatchable renewables or battery storage systems cannot meet the fluctuating demands posed by the residual load curve. Therefore, traditional dispatchable sources, with the help of some demand response, must continue to provide the bulk of a power system's residual load flexibility. For instance, the total dispatchable renewable capacity of a power plant (hydro, pumped storage, bioenergy and geothermal) may be about 5.5 GW, but fluctuations in the residual load may ramp up to 18 GW in six hours; therefore, in this certain re-dispatchment scenario, most of the residual load flexibility is handled by fossil gas-powered facilities.

Aims of flexible power plants

Flexible power plants can quickly ramp up or down their electricity generation to match fluctuations in demand or compensate for changes in renewable energy output. This ability to respond rapidly is known as "grid flexibility" and its main aims are:

• Reduced time to launch and starting expenses: With less time spent starting up, the facility may begin operating at full capacity right away. The operational flexibility of a plant is greatly enhanced by a quick start-up. Frequent maintenance costs and large fuel consumption costs are two examples of the startup costs.
• Reduced minimum load and enhanced efficiency at partial loads: The bandwidth of flexible power plants such as thermal plants is increased by operating them at lower loads, allowing for more operational flexibility. The fuel efficiency of some power plants drops dramatically at low loads; enhancing their flexibility requires addressing this issue.
• Reduced minimum required uptime and running time: A plant can respond more quickly if the amount of time it has to be kept running after startup or closed after shutdown can be minimized.
• Faster ramp rate: The ramp rate of a plant is the rate of changing net power during operation. Plants with faster ramp rates can respond more rapidly to changes in system demand.

Requirements for conversion to flexible power plants

• Software: Modifications to the plant's control system and operational infrastructure via installation of optimization software will increase component operational flexibility (for example, turbines etc.).
• Hardware: Improvements to the power plant's ramping rates and part-load efficiency, as well as reductions in the minimum up- and downtimes of the plant, would be the result of engineering upgrades designed to lower the minimum load. All aspects of the plant's operations and technological constraints must be taken into account throughout the upgrading process.
• Roles and responsibilities of stakeholders: There is a need to examine current plant operations and locate potential areas for adaptability. In order to maximize earnings, power plants might take part in day-ahead, intraday and balancing markets. In order to encourage existing power plants to adopt flexible operation, governments might provide financial incentives.
• Requirements of regulators: Minimum load and ramping rate limits are two examples of laws that encourage power plants to operate with more flexibility. In a highly variable renewable energy system, new ancillary service items that are valued in this system can provide income for flexible power plants. The temporal granularity of wholesale markets should be increased so that prices are more reflective of current market realities. Flexible operation of thermal facilities is encouraged by new policies that aim to update take-or-pay contracts.

Conclusion

Flexible power plants aim to reduce time to launch and starting expenses, reduce minimum load and enhanced efficiency at partial loads, reduce minimum required uptime and running time and bolster ramp rate. Modifications to the control system and operational infrastructure through optimization software can increase operational flexibility. Engineering upgrades designed to lower the minimum load can also improve plant performance. Stakeholders must examine current plant operations and identify potential areas for adaptability. Governments can provide financial incentives to encourage existing power plants to adopt flexible operation.