Most of the older wind turbines (WTGs) receive extremely low feed-in remuneration after the expiry of the feed-in tariff under the EEG. Therefore it makes sense to feed the electricity directly into adjacent consumption centers such as production plants. The catch is that the grid connection may have to be altered. Another challenge in this scenario is the fact that then also the old WTGs must comply with the new grid connection rules like the country-specific „Network Code Requirements for Generators“ (NC RfG). 20 years ago, only the large power plants were responsible for grid stability. The low feed-in capacities of the decentralized regenerative generators were taken off the grid in the event of any grid disturbance. The wind turbines only had to run with a maximum power factor, an externally controlled active and reactive power was not necessary. Also, the response to grid frequency changes were only the responsibility of the large power plants.
How can these old WTGs continue to be operated economically in terms of sustainability? One solution could be to supply industrial customers directly, whose energy requirements can be covered in part by these WTGs. By eliminating procurement costs and grid fees, both sides, the producer and the consumer, can benefit.
The incentives to merge the two partners are high due to the difference between the low feed-in remuneration of the depreciated wind turbine and the high electricity tariff of the consumer. Why is this possibility not already being practiced everywhere? Even if the wind turbine is connected directly to the plant, it is considered a new grid connection. This means that the current grid requirements must now also be met. delta energielösungen technischer anwendungen GmbH, as a planner for regenerative and decentralized energy in cooperation with FREQCON GmbH, the leading German manufacturer of frequency converters and control systems for renewable energy systems, has brought a concept to market readiness, which makes the old wind turbines fit for the new tasks.
“After clarifying the economical aspects for a prototype,“ says managing director Axel Hollmann of delta, “the more than 20 years of experience with old and new wind turbines helped me to describe the critical operating points. With the help of FREQCON – another long-standing player in the renewable industry – we have now found clear interfaces to get a series product on the way.”
“The grid services must be provided proportionally to the maximum amount of electricity that is fed into the grid“, reports Mr. Klosse, also managing director of delta. “We are able to adapt the different local requirements in order to find the optimum in specific cases.”
“delta energy lösungen technischer anwendungen GmbH” is a company founded in 2019, which emerged after 17 years from a planning office for electrical medium and high voltage systems. Its employees combine expertise from various areas of renewable energies even before the introduction of the German Renewable Energy Sources Act. The employees have also been involved in the development of measurement and certification guidelines for years. Most recently, a short-circuit simulator for testing the grid stability of the latest generation of wind turbines was completed (FRT test system). The employees of the company are dedicated to ensure a complete and secure supply by means of renewable energies.
FREQCON is a pioneer of modern converter technology introducing full-scale power converters for wind turbines to the market in the early 1990s. Power converter and control systems designed and manufactured by FREQCON allow efficient and reliable grid integration of renewable energy sources such as wind, solar and energy storage systems.
From kW to multi-MW system solutions from FREQCON are used both for grid-connected systems as well as island grid systems. Today over 45 GW of installed capacity rely on products and solutions designed and manufactured by FREQCON. The development and production of high-quality, reliable and innovative solutions is part of the quality principle of FREQCON GmbH.