Batteries with 200 Wh storage per kW of solar capacity could mitigate curtailment in Spain

Academics at the Sapienza University of Rome and the University of Jaén have studied the energy and economic implications of the curtailment of solar electricity in Spain since the first known incident, in April 2022.

The researchers concluded the losses to NPV, and rise in LCOE caused by curtailment would justify the installation of batteries with up to around 200 Wh of storage capacity for each kilowatt of solar generation capacity. That would enable solar arrays to recover up to 80% of the curtailed energy and would justify capital expenditure of up to €47 ($55) per kilowatt. Larger batteries would recover more potential excess electricity but their significant cost increases would not be justified if they were to be used solely to mitigate curtailment.

Some 2.9% of Spain’s solar energy has been curtailed over the last two years, with that initial incident occurring due to a forecasting failure by grid company Red Eléctrica.

The paper “Energy and economic implications of photovoltaic curtailment: current status and future scenarios” – to be published in September in Sustainable Energy Technologies and Assessments – offers a first-of-its-kind national estimate of the economic consequences of curtailment and assesses how such incidents, which renewables generators are not usually compensated for, could affect solar project profitability.

The researchers used electricity generation, curtailment, and price data from October 2022 to September 2024 and applied a techno-economic model to calculate the impact of curtailment on LCOE and NPV and to assess battery viability.

The study identified critical curtailment levels which would render solar projects unviable and suggested guidelines for grid operators and policymakers.

Conclusions

In the last two years, curtailment has affected 2.9% of Spain’s solar energy. Some 2.5% of that volume related to excess energy reported a day in advance, meaning generators were not compensated for it.

Curtailment cost more than €107 million – or €146,400 per day – and drove the LCOE up 2.5%, or €0.001/kWh while reducing NPV 7.7%, or €27.10/kW.

Since April 1, 2024, Spain has experienced negative electricity prices during 5.5% of hours with a low of -€2.00/kWh, an average negative price of -€0.40/kWh and a median value of -€0.10/kWh. The authors of the curtailment study said every 1% rise in curtailment will raise LCOE 1.69% and reduce NPV 2.96%.

“A grid with high photovoltaic penetration will require power plants with high response capacity and sufficient storage capacity, neither of which has been adequately planned in Spain,” wrote the researchers. “Without these solutions, or a paradigm shift in energy consumption behavior, the curtailment rate is expected to increase to between 35% and 40%.”

From pv magazine España.