WEMAG AG is a German clean energy and natural gas utility. In addition to selling power and gas nationally, it also operates a regional distribution grid in western Mecklenburg, northern Brandenburg and Lower Saxony through its subsidiary WEMAG Netz GmbH. WEMAGs’ wind-swept grid already has an installed renewable generation capacity of more than 800 megawatt (MW). In 2014 these assets generated more than 100 percent of the energy volume distributed to consumers in the 8,600 km² grid area.
The increasing volume of clean, but intermittent, energy feed-in to the grid disrupts the short-term balance between production and consumption. Such fluctuations must be compensated for through the use of positive, or negative frequency regulation power.
If renewable energy penetration on a grid rises above a relatively low threshold, such control power cannot come from conventional thermal power plants, which need to run at about 60 percent of their production capacity to have enough upward and downward flexibility. This so-called “must-run” capacity clogs grids and forces renewable generation units to be taken offline.
Younicos built a 5 MW/5 MWh battery power plant for WEMAG. Located in the Schwerin district of Lankow, the battery park is housed in a hall the size of a school gym. Inside, 1,600 battery “trays” contain 25,600 lithium manganese-oxide cells that can store and release energy within milliseconds. Five medium-voltage transformers connect the units to the grid and boost the current from 480 volts to 20 kilovolts and back down as needed.
Younicos’ Y.Q software platform is at the heart of the system. It includes AC battery management (ACBM), battery power plant management (BPPM) and a SCADA-integrated energy management system. Together, these software systems control the battery cells – both in the interplay of the individual units, as well as the entire array’s interaction with the grid. This software architecture ensures three critical results. First, the software enables the battery park to automatically provide necessary services at any time. Second, it guarantees that the batteries are always full or “receptive” enough to charge and discharge as required. Third, the software optimizes the lifespan of the batteries by keeping the lithium-ion cells in their “comfort zones” as much as possible.
In late 2016, WEMAG decided to enlarge their battery park. With this upgrade, the utility’s storage resource will double its power output from 5 MW to 10 MW, while the energy capacity will increase from 5 MWh to 15 MWh. An additional 1,254 battery modules, or 27,588 cells, will be installed in a second building.
The battery park earns its keep by competing in primary frequency regulation markets. In addition, Younicos is currently upgrading the battery system’s functionality to make it capable of black starts, full islanding mode and integrating renewables in grid restoration scenarios.