Flexibility (Power System)
Flexibility: Concept Definition
According to the International Energy Agency, the flexibility of a power system refers to "the extent to which a power system can modify electricity production or consumption in response to variability, expected or otherwise"[1]. Another source described it as "the modification of generation injection and/or consumption patterns in reaction to an external signal (price signal or activation) in order to provide a service within the energy system" [2].
Flexibility: Why It Matters
Load balancing is not the only service a power system must perform flexibilty. There are many other services the operators of a power system must consider to make the grid stable. The three main services for the reliability of a power system are: load balancing, frequency response, and voltage response.
Renewable sources, together with some battery storage, can already perform some of these services better than a conventional power system[3]. For example, renewable sources can supply reactive power (and therefore voltage response) even when they are not giving real power, and batteries can perform frequency response better than conventional sources[4]. Currently a renewable power source integrated with a battery storage system is already cost competitive to some conventional sources[5], and such implementation will boost the reliability of the grid.
However, current capacity of dispatchable renewables or batteriers is not enough to cover variations of the residual load curve. So the residaul load flexibility of a power system must still be performed mainly by conventional dispatchable sources, with the aid of some demand response.
Flexibility: Supply Side
Conventional Flexible Power Plants
Battery Storage
Interconnection
Better interconnections between grids can also ease some of the flexibility demand to neighboring grids. The more flexible dispatchable power plants are well connected in the system, the less ramping any single power plant will need to perform. Interconnections can also bringdown the wholesale electricity prices of the neighboring grid because electricity production with higher marginal costs can be reduced.
However, conventional electricity sources may choose to export electricity rather than ramping down shutting down more often when interconnection is better. This causes a difficulty to reduce conventional electricity generation to full potential. For example, people have been suggesting that brown coal electricity generation in Germany could have dropped by 37%, should there be no electricity export and all the additional residual load flexibility was performed by brown coal power plants[6].
Flexibility: Demand Side
Ways to Improve Flexibility
Technical Measures: Retrofit and New Design Mindset
Market Measures: Real Time Markets and Incentives
Apart from retrofitting existing conventional power plants or build new ones under a new design mindset, the electricity market can also boost the flexibility of the overall system, if designed properly.
References
- ↑ International Energy Agency (IEA), Harnessing variable renewables., Tech. rep.;fckLR2011
- ↑ "Flexibility and Aggregation Requirements for their interaction in the market". Available at:fckLRhttp://www.eurelectric.org/media/115877/tf_bal-agr_report_final_je_as-2014-030-0026-01-e.pdf
- ↑ "Powering into the Future: Renewable Energy & Grid Reliability". Available at: http://www.mjbradley.com/sites/default/files/Powering_Into_the_Future.pdf
- ↑ http://reneweconomy.com.au/tesla-big-battery-moves-from-show-boating-to-money-making-93955/
- ↑ http://reneweconomy.com.au/coal-dies-super-cheap-renewables-plus-battery-storage-82743/
- ↑ https://twitter.com/energy_charts/status/927154958243450881
