LONDON -- We hear a lot about the need to balance variable renewables with gas or energy storage, in order to integrate them into the grid. But this week Europe’s solar sector has called for market rule adaptations that would allow solar photovoltaic (PV) installations themselves to offer balancing services to transmission system operators.
The European Photovoltaic Industry Association (EPIA) has proposed amendments to the Electricity Balancing Network Code currently being drafted by the European Network of Transmission System Operators (ENTSO-E). “As there is a balancing code in the making, we took the chance to highlight the main principles that should govern balancing markets across Europe to allow PV participation in future,” said Giorgia Concas, EPIA's policy advisor.
One of the main prerequisites for PV to be able to participate in balancing would be to allow for aggregation of distributed solar systems into larger portfolios covering areas as wide as possible, Concas said. A project (REserviceS, supported by Intelligent Energy Europe) in which EPIA participated examined the costs of providing ancillary services with PV and wind, producing a report which showed that the larger the portfolio, the lower the losses and levels of uncertainty, and thus the higher the amount of electricity that can be offered through ancillary services.
While some European TSOs are formulating new rules that will allow aggregated electricity, such as that from so-called virtual power plants, to participate in balancing markets, there is currently no Europe-wide framework and many TSOs do not allow PV to participate. Concas points out that experience with wind integration is more advanced than experience with PV. But with the code being drafted, “this is a key moment” for PV, she said.
EPIA also wants ENTSO-E to specify that packages of balancing reserve or energy (called “products”) can be smaller than current levels. This means TSOs would ask for less power so that amounts from distributed generators can qualify. And the trade body wants TSOs to accept offers for reserve that do not meet the certainty criteria currently in use.
“Because PV and wind are variable it is difficult to know in advance exactly how much energy they will produce at a certain moment in time,” Concas said. “So if a TSO procures reserve power ahead of real time, it should accept that the offer of the bid has an uncertainty margin – we say the confidence level should be lower than what is accepted today.”
This would mean that, in effect, TSOs would have to accept more risk. “Yes, this is challenging,” says Concas; “TSOs have to deal with security and therefore want to have as much certainty as possible.” On the other hand, she points out that accepting offers with lower certainty would increase market liquidity: by accepting lower confidence levels, TSOs would need to accept more offers, increasing the number of market participants.
Some changes to the rules would also increase certainty, EPIA says. “We want to highlight that if TSOs could not only procure reserve or balancing services a long time ahead of real delivery, if they could also ask generators to offer balancing services very close to real time, then of course the reliability of PV and wind offers would be much higher,” said Concas. EPIA wants the so-called gate closure time – the time by which all offers have to be submitted and after which it is not possible to adjust them – to be as close as possible to real time in order to increase the reliability of offers from variable generators.
Concas says EPIA will be discussing acceptable certainty levels with TSOs, and the industry needs to analyse the impact of lower levels. Today’s average certainty level is 97.5 percent, which is “very ambitious for us,” she says.
“I think it’s very important that our industry comes up with real on-the-ground data,” she continues. “It’s important to have more and more demonstration projects in PV, not only in the wind sector – with concrete data demonstrating that, even if the rules are slightly changed, the TSOs’ main concern, security, is not endangered.”
Looking to the future, Concas is optimistic about the potential for change, and sees a time ahead when the share of variable renewables will be very high in many areas of Europe. “If at one point we will be very important in the system, we will have to provide certain support, and therefore the rules should be adapted by then. And the earlier the better,” she said.
Lead image: Solar panel geometry via Shutterstock