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Dynamic Power Management

Project summary

Within the FLOW program, TenneT has initiated the project Dynamic Power Management. The aim of this project is to reduce the cost of offshore wind energy by introducing an integral approach on the combined system of wind farm and grid connection.

The goal of this project can be summarised as follows:

1. Improved utilisation of the grid connection 
Dutch government policy strives to lower the cost of offshore wind. An important part of these costs is made up of the grid connection. These costs are "socialized" and are often not fully included in cost optimizations. The central project idea is to increase the capacity factor1 of the cable, either by adding more wind turbines or by using a cable with less nominal capacity and providing monitoring and control to safeguard the electrical connection against overloading.

2. The participation of wind energy in balancing and providing ancillary services
Current renewable subsidy schemes and market mechanisms prioritize renewable sources and wind energy over traditional energy sources. The balance between energy production and energy consumption is realized through conventional energy sources. At higher penetration levels of wind energy, the importance of wind energy contributing to balancing and providing ancillary services will increase. This project investigates the possibilities of a “power plant approach” for offshore wind.

The project Dynamic Power Management is oriented around three themes:

• In Dynamic Grid Management, the grid connection capacity is recognized to be variable, depending on the ambient temperature and load history of the cable. This opens options to increase the utilization rate of the electrical infrastructure. 
• In Market Interaction, it is investigated how offshore wind energy could increase its value by participating in other markets, such as markets for ancillary services. 
• In Development of Dynamic Wind Farms, four options are analysed to reduce the cost of energy and to increase the predictability of offshore wind energy. 

The results obtained are summarised around these three themes:

Dynamic Grid Management
Analyses show that for Dutch wind farm projects, the short term cable capacity is only 2% larger than the long term cable capacity. For the German situation, this potential is larger due to different environmental permission limits which drive the cable design.

Market interaction
It was found that significant additional revenues can be made by providing specific products on the market for ancillary services. Adjustment of the market design would further increase the potential additional revenues.

Development of Dynamic Wind Farms
It was found that a lower power density tends to lead to lower cost of energy, and that this will lead to reduced financial risk during low-wind years. It was also shown that proper storm control leads to between 0.5% and 1.0% more energy yield. Furthermore, predictability can be improved through reduction of direction dependency, by placing turbines in curved, discontinuous or nonparallel rows. It was also established that a modest level of overbooking to compensate for nonavailability leads to a reduced cost of energy, which is estimated between 0.2% and 0.5%.

Finally, accurate modeling and simulations are essential to provide realistic figures for the Annual Energy Production (considering wake losses, electrical losses, and failure losses) and the Levelized Cost of Energy. The optimizing techniques used in this work offer project developers a tool to optimize for multiple design goals through an integrated and automated procedure and should become part of the standard practice in the offshore wind industry.

Based on the above results, the overall project objective was to establish clear recommendations and input for the Set of Requirements for the development and engineering of a 300MW demonstration project (Leeghwater) and a 900MW Far and Large off-shore wind farm. However, these specific cases have become obsolete due to the new Dutch government policy to cluster offshore wind farms into five clusters of 700MW, located close to shore. Therefore, it was decided to translate the project results and recommendations to the new policy.

The project results contribute to:

Reduced cost of energy
The reduction of cost of energy is estimated at 0.7 to 1.5%. It is shown that this is achieved by applying storm control and by introduction of a modest level of overbooking. Furthermore it is shown that the use of turbines with lower power density, the cost of energy tends to be lower as well.

Reduced risks
It is shown that the financial risk for the project developer due to low wind periods is can be reduced significantly by the use of wind turbines with low power density. For a power density of 300 W/m2, this risk is reduced by 26% compared to a power density of 550 W/m2. This may well lead to lower interest rates, which translates into lower cost of energy.

Additional benefits
It is shown that offshore wind energy can generate additional earnings and reduce market system costs by participating in the Negative Tertiary Control Reserve Market. In this way, offshore wind energy contributes to the stability of the energy system.