A constant criticism of variable renewables surrounds its ability to provide firm power during grid events, such as frequency response and demand side response.
In Europe, wind has demonstrated its ability to perform these roles, often cheaper than conventional power. The industry is now calling for policies to support this further.
A new report in the US has, however, said more research would be required for wind and solar, to play such roles.
The report, Ancillary Services in the United States: Technical Requirements, Market Designs and Price Trends, was backed by the American Wind Energy Association (AWEA).
It was carried out by Electric Power Research Institute (EPRI), which conducts research and development for the nation’s utilities.
EPRI said a closer look is needed into uncertainties of forecasts of wind and solar power so that they can provide ancillary services to help grid operators maintain a reliable electricity system.
Investigations are needed into the economics of wind and solar providing the services compared with that of conventional forms of electricity generation.
Further research is needed into forecasting, relying on ‘closer to real-time’ markets for ancillary services, and how to manage periods when forecasted production does not meet actual output.
There is an out-dated misconception that wind and solar, because of their variability, cannot provide ancillary services or that they increase the costs, said AWEA’s John Hensley. That is not the case, he said.
The grid is undergoing a massive transformation with increasing amounts of renewables and gas-fired generation in the mix.
US electricity generation from renewables surpassed that of coal in April 2019, according to official government data.
Therefore, wind and solar will have an increasingly important role in helping maintain the operational reliability of the power system and they are well-positioned to do so.
Hensley said resources such as wind are discriminated again by outdated rules. The ancillary services needed nowadays are also not the same as have been needed in the past century.
In addition, ancillary services have always been compensated, he added.
The technical capability of wind and solar to provide the majority of ancillary services, including regulating reserve, contingency reserve, fast frequency response, voltage control, and even ‘black start’ — to recover from a total or partial shut-down — has been previously demonstrated by a number of studies, noted the authors.
But it remains rare for wind and solar to participate in US ancillary service markets.