Alqueva is a pumped storage hydropower plant equipped with four fixed-speed reversible pump-turbine units with a total installed capacity of 520 MW. The Alqueva demonstration in the XFLEX HYDRO project consists of evaluating three low-cost opportunities for improving the flexibility services of pumped storage plants.
The first opportunity aims to increase the current operating range of each unit in turbine mode. Numerical fluid dynamic and structural dynamic simulations were performed by the University of Stuttgart especially focused on part load, deep part load and speed no load operation where very complex unsteady hydrodynamic phenomena occur. Leveraging these numerical results and measurements performed 10 years ago and site measurements performed over the last year, GE implemented its latest damage evaluation methodology to demonstrate the possibility of significantly increasing the operating range in turbine mode; opening with few restrictions an operation from zero to 100% of the rated power. In addition to this, an analysis of the various transient modes (start-ups, sequences from synchronous condenser modes to pump or turbine mode, etc.) has also been performed by GE enabling the identification of major opportunities for damage savings. GE proposed a global damage model for the whole operation of the machine.
The second opportunity consists of the implementation of GE’s new smart digital control, the Advanced Joint Control (AJC), which follows the Smart Power Plant Supervisor (SPPS) methodology developed by EPFL for the project. The AJC aims to optimise the efficiency of the units by considering the needs of the electricity market, as assessed by EDP’s trading division, and the units’ capabilities. It is expected to maximise the units’ efficiency (i.e. water savings), reduce wear and tear and improve start-up and stoppage manoeuvres. This will, ultimately, lead to reducing the water used for each MWh dispatched and lower operational costs.
Currently, the AJC software and hardware are under development by GE in close collaboration with EDP. The final stage of the demonstration of this tool will occur in late 2022.
The third opportunity consists of operating the plant in Hydraulic Short Circuit (HSC) mode, which enables regulation of the power in pumping mode. This means that the plant can participate in ancillary system services markets when in pumping mode. Two field test campaigns to monitor the new possible range of operation were successfully conducted by EDP and GE in June and November 2021. Preliminary results seem to indicate no hydraulic, mechanical, or electrical risks or potential issues for operating the plant in this new mode of operation. However, detailed results of the campaigns will be finalised in the first quarter of 2022.
The official demonstration phase is due to start later in 2022.