The leadership of renewable energies in the transition towards a decarbonized planet is now unquestionable. The exponential growth of their implementation without a corresponding reduction in the use of fossil fuels has produced some imbalances in the system. One of them is that occasionally more energy is produced than is consumed. Or that, due to fluctuations in the price of electricity, there are time slots in which prices plummet. Both situations can lead to what is known ascurtailment, an undesirable phenomenon that can be solved with a simple step that many countries are already taking: the development of storage.
Some people wonder how to deal with the intermittency of renewables, but very few question what happens when more is produced than is consumed. This is known as overproduction. The answer is clear: in the current system, energy from renewable sources such as photovoltaic or wind energy is wasted if it is not consumed. This is why curtailmenthas become one of the main concerns of producers, owners and investors of large installations.
What is curtailment
Energy curtailmentis an order by the responsible market operator for both large-scale photovoltaic and wind power plants as well as self-consumption installations to stop producing energy for a specific period of time. It occurs mainly for economic or grid capacity reasons, and in both cases, it is caused by a mismatch between supply and demand, i.e. times when electricity production significantly exceeds consumption.
These outages are closely related to the dreaded ‘duck curve’, a term defined in 2013 by the California Independent System Operator (CAISO), which already foresaw that the take-off of solar power would lead to a disruption in the system. A graph of daily electricity consumption shows that the highest demand occurs early in the morning and late in the day, inversely proportional to the peak hours of PV production.
Overproduction can have two consequences. One is that production exceeds grid capacity and the market operator is then forced to order large PV plants to shut down. The other is that the increase in supply does not match the increase in demand and prices plummet, leading to production at zero cost.
In both cases, a detrimental situation arises for the plant owner and, depending on what has been agreed, it can also affect the operation and maintenance (O&M) company by worsening the performance rate.
Causes of curtailment
According to the Australian energy market operator AEMO, curtailment is a phenomenon that is expected to increase. It even estimates that it will reach 20% of renewable energy production by 2050, about 50 trillion Wh (equal to 50 billion kWh), the equivalent of what renewables currently produce in Australia.
The main players in the PV sector are calling for increased investment and the creation of appropriate regulations to give storage the prominence it deserves and to avoid the increase predicted by the AEMO. However, in order to prevent its effects, it is necessary to take into account the conditions under which this phenomenon tends to occur.
- These are usually days with favorable weather conditions (very sunny or windy days), when energy production is high.
- Demand is low. In most cases, because it is during holiday periods or weekend days, when forced outages are common.
How to avoid curtailment
As we have already mentioned, the key to avoiding wasting the electricity already produced is to be able to store it for use when it is most appropriate, either at night in the case of photovoltaic or when there is no wind in the case of wind power. But there is also the option of arbitrage to regulate the grid according to supply and demand, which allows energy to be bought at times when production is cheapest and sold when prices rise.
Given the idea, the current energy market must begin to consider the need to incorporate battery systems (BESS) in any new renewable energy project and include them in existing installations to reduce the environmental impact and maximize their performance.
However, as associations of companies in the sector such as the Spanish Photovoltaic Union (UNEF) point out, a progressive generalization of storage cannot take place without investment incentive measures, in addition to stimulating grants and aid.