(45c) Techno-Economic and Environmental Optimization of Wind Farm with Energy Storage Systems

The growing concern of climate change induced by energy consumption form fossil fuels, has led to a worldwide focus on the use of renewable energy sources such as solar and wind to fulfil the growing energy demand. Wind energy is one of the most promising renewable energy sources with an estimated total of 2-6 TW globally accessible, which can fully satisfy the current electricity consumption of the whole world which is estimated to be around 2.3 TW [1]. However, the discrete generation and inherent uncertainty in wind power cannot be overlooked. The integration of an Energy Storage System (ESS) is being considered as a promising solution to overcome the problem of intermittency.

Facing challenges in designing and operating wind farms with energy storage systems, we propose a systematic methodology to minimize the relevant costs. A receding horizon optimization, as a supervisory layer of economic model predictive control (EMPC), provides a macro-scale scheduling of the whole wind farm and energy storage components, which regulates the trade-off between power output and life-cycle performance. Furthermore, individual pitch controllers of wind turbine are designed to mitigate effects from vibrations and fatigue loads on its main flexible components such as the blades, tower, and drive shaft. A management system for ESS is also integrated for flexible adaptation of energy storage technologies.

In this paper we detail the holistic approach from the wind farm and ESS modeling and optimization, to wind turbine aerodynamic and structural models with appropriate control strategies. A case study is discussed thoroughly combining an offshore wind farm (OWF) and multiple innovative low-cost battery technologies. OWF is an emerging technology to utilize wind energy on a large-scale, but faces more complicated weather conditions than onshore systems leading to higher operational and maintenance costs. The rich offshore wind resources are located far away from the end load and require coupling to high capacity transmission lines. Additional ESS can mitigate transmission congestion, perform frequency control, and defer or avoid transmission and distribution upgrades. The wind farm with ESS needs to be deployed as an integrated system taking its operational, economic and environmental impacts into account. It is demonstrated how the proposed methodology is applied to an OFM constituted by 5-MW and 1.5 MW wind turbines in a real environment, with a properly sized ESS, in various scenarios of feed-in-tariff or other incentive schemes. The results show significant benefits in the overall economic, environmental and social performance for not only the wind farm owners, but also the overall energy supply structure. The simulation results using the Fatigue, Aerodynamics, Structures, and Turbulence (FAST) wind turbine simulation tool developed by NREL [2] prove the adopted control strategy is able to further reduce the unbalanced loads acting on the rotor compared to the traditional PI control method with reduced computational efforts, making it suitable for real time implementations. The environmental issues in wind farm and ESS development are also discussed.

[1] International Energy Agency (IEA). Key World Energy Statistics. 2016.

[2] Jonkman, J., Butterfield, S., Musial, W. and Scott, G., 2009. Definition of a 5-MW reference wind turbine for offshore system development. National Renewable Energy Laboratory, Golden, CO, Technical Report No. NREL/TP-500-38060.