ACCIONA has become the first company worldwide to supply extra wind power to balance the electricity system when covering for technical constraints on transmission lines.
The fact that wind or solar radiation can vary at any moment, and therefore complicate forecasts of future available energy, has meant these technologies have for decades been seen as a problem in balancing the electricity system.
This view does not conform to reality, however, and ACCIONA recently reached a landmark by becoming the first company worldwide to provide adjustment services to the grid, by increasing wind power generation alone.
Such services are essential to the proper functioning of the grid, since electricity cannot be stored on a massive scale and, thus, all energy has to be produced the moment it is consumed. Any decoupling between offer and demand can, if it is not corrected on time, endanger the quality of the electricity supply. Renewable technologies can now participate, as of 10 February, in this kind of service via the system adjustment services managed by the System Operator — in this case, REE in Spain. The generating companies offer capacity or backup power that can be revised upward or downward — i.e., increasing or reducing existing output — to be managed the following day by the operator.
In this context, on 28 February this year, an important landmark was reached in the management of the Spanish electricity system. ACCIONA participated in it as the first company to offer balancing services exclusively based on wind energy capacity, requested by REE to solve technical restrictions in transmission lines by providing additional power generation.
Instead of the usual situation, where wind farms are required by the operator to limit their production, the opposite, a more complex scenario, came into play: within minutes, a series of wind farms managed by ACCIONA were told by REE to increase their generation capacity by a total of over 150 megawatts (MW). This was possible due to the technical capacity of the subsidiary, ACCIONA Green Energy Developments, which interacts with the market, and the ACCIONA Renewable Energy Control Center (CECOER), which remotely controlled the operation in constant coordination with REE.
As well as the service to resolve technical constraints, ACCIONA has also been accredited by REE for the provision of other system adjustment services, such as tertiary regulation and deviation management for winpower capacity of 999 MW (out of a nominal total of 4,735 MW in which ACCIONA currently participates in Spain).
Further down the line, the Company plans to set up other programming units based on wind power and to use other renewable technologies (outside of hydro power, which is already used for these services). As well as ensuring a greater penetration in the grid, the participation of renewable energies in system adjustment services will increase the level of competition in the markets, which will have a positive effect on the electricity price paid by consumers.
The electricity system has to keep a constant balance between generation and consumption to preserve the security and quality of the supply. The operator of the system — in Spain, REE — programs the operation of power plants from data provided by the market operator (OMIE), the system operation processes and demand forecasts managed by REE. Then it gives timely instructions for production to be adjusted to real-time consumption.
This process is carried out every day and against the clock — through highly regulated and complex procedures — such that the forecasting of programmed production and consumption is adjusted the closer the operation gets to real time. These are the main steps in the process:
From this final forecast, as the system is operated, REE issues instructions to generators so that they increase or reduce production (adjustment services or real-time regulation) in order to maintain the balance of the system at any moment.