Greece is imposing new restrictions on how quickly renewable - energy producers can raise or cut electricity output, addressing an emerging problem of the green-power transition: Too many generators reacting to market prices at the same time can threaten the stability of the grid.
The country’s energy regulator, known as RAAEY, has approved a methodology proposed by power-grid operator IPTO that limits abrupt changes in output from renewable plants connected to Greece’s high-voltage transmission system.
The rules follow incidents over the past two years in which renewable generators independently slashed production within seconds as prices in Greece’s day-ahead electricity market fell to zero or below.
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For an individual solar or wind farm, switching off production when electricity prices turn negative can make economic sense. For the power system, thousands of megawatts potentially responding to the same price signal can create a different problem.
IPTO warned that simultaneous reductions could result in a large and unexpected loss of generation, creating what it described as an extremely serious risk to the electricity system.
Under the new framework, renewable plants that independently decide to alter output - rather than responding to an instruction from IPTO or their market aggregator- will generally have to make the adjustment gradually.
Instead of suddenly cutting generation, plants will be required to change output linearly over a 10-minute period, subject to a tolerance threshold. The period will begin five minutes before the start of the relevant imbalance-settlement interval. The aim is to give the grid enough time to respond and prevent sudden mismatches between electricity supply and demand. There will also be financial consequences for generators that ignore the rules.
IPTO will be able to conduct sample compliance checks. If it determines that a plant changed output without an instruction and failed to follow the required 10-minute adjustment, the producer will face a noncompliance charge calculated partly according to the plant’s installed capacity.
The size of the penalty and the tolerance threshold haven’t yet been determined. The regulator has given IPTO three months to submit recommendations before the system becomes fully operational. Greece’s dilemma is increasingly familiar across Europe. Rapid growth in renewable generation is producing more hours of very cheap - or even negative - electricity.
