The developer, Acres Energy, claims that in connecting its 17.5 MW wind project in Donegal to a 9 MW motor-generator set, it will act as a synchronous generator, rather than an asynchronous generator as with a typical wind farm. This acts as "glue", synchronising torque and system inertia to keep generators and the system together following a fault, says system operator Eirgrid. It anticipates a future shortage of this "glue" as more asynchronous wind farms connect to the system to meet Ireland's 40% renewables target.
Acres will be the world's first grid-connected example of this type of configuration. In agreeing to connect the project ahead of 3.5 GW of other wind projects waiting for a connection, the Commission for Energy Regulation (CER) has accepted Acres' and Eirgrid's assertion that it will be a research and development (R&D) project. "There is provision within the rules for an R&D case," says Dan Hannevig from Acres. Early connection will demonstrate to what extent such projects could provide a long-term solution to the potential shortage of "system glue" in Ireland, says Eirgrid.
In the first phase of the project, diesel generators converted to run on dimethyl ether (DME) from biomass will be connected to the motor-generator set. Later, de-clutchable DME-fuelled turbines will replace them to run the generator set. At the same time, a flow battery storage pack will be connected to the wind farm, in effect creating two backups to wind.
Hannevig hopes the project will be running by 2011. He explains that as the wind farm's interface with the grid is only via the rotary coupling, the turbines need not be grid code compliant. This opens up the field to cheaper turbines and, he says, he is talking to a number of suppliers.
The project, which has been five years in development, will be eligible for Ireland's fixed-price renewables tariff. Hannevig points out it has not received any R&D support from the government or its sustainable energy agency.