Grid connected Offshore Wind and Energy storage (GOWES)

WHY

Generating renewable electricity on a large scale brings challenges for the energy system. Traditionally, electricity production followed demand, but renewable energy depends on weather and is intermittent by nature. By 2030, there could be frequent overproduction during windy or sunny periods and, at other times, underproduction when it’s windless and cloudy. Flexible demand is needed to keep the energy system balanced, and sometimes production will need to be reduced if demand can’t keep up.

The Netherlands will face major challenges in balancing offshore renewable electricity. There are various ways to improve flexibility and reduce curtailment. Promising options to improve system efficiency are combining wind farms with floating solar panels and introducing electrolysers and energy storage. Offshore storage (like ‘offshore batteries’) could allow energy to be stored at the production location and used later. This would enable a more consistent electricity supply for hydrogen production and provide hydrogen for industries and power stations when renewable supply is low.

Onshore storage is also an option, especially to prevent grid congestion, but it has limitations, particularly in a densely populated country like the Netherlands. Offshore storage is gaining interest, with recent Dutch offshore wind tenders including flexibility requirements. As indicated in a recent Letter to Parliament, future policies may promote co-locating wind farms with storage.

The consortium believes further exploration of offshore storage applications is essential before making decisions. This may provide wind farm developers and solution providers with insights into offshore storage's practical and economic aspects. Case studies will focus on wind farms as planned in the Dutch North Sea to ensure the results are useful.

WHAT

We will study two upcoming wind farm sites: Ten Noorden van de Waddeneilanden (TNW) and Doordewind - site I. These sites were selected because they are relevant for future developments and have interesting characteristics. TNW has a capacity of 700 MW and will include 500 MW of offshore hydrogen production. Doordewind, being larger and with a capacity of 2000 MW, aligns with the expected maturity of offshore storage solutions in the future.

The study will answer the following key questions:

• How can offshore storage improve flexibility for the Dutch energy system?

• What additional value can offshore storage bring to wind projects (e.g., new revenue streams or business models)?

• Which storage technologies are best for specific markets, and what cost goals (€/kWh) need to be met?

Two offshore storage technologies will be examined for comparison:

1. Hydro-Pneumatic Liquid Piston Technology by FLASC, identified by Seaway7 as having high potential, and

2. Offshore li-ion batteries are widely used onshore but need adaptation for offshore use (marinisation and installation). Li-ion is chosen because most data (costs, efficiency, lifespan, energy density) is already available, and any missing information can be provided by partners and reviewed by stakeholders.

We will develop an economic model of the two different wind farms and the different types of storage systems. Using TNO’s EYE model, a day-ahead wholesale model for the Dutch market, we will evaluate several scenarios, which will be based on the Renewable Energy Directive (RED III) and the Dutch routekaart electrificatie. For the scenarios - including a reference case without storage or conversion -we will predict the variation in the Levelised Cost of Energy and net present value of the wind farm by varying the size (MWh) and capacity (MW) of the storage systems. During the project, the model will be updated to deal better with the real-world operational characteristics of the new offshore storage technologies.

The study will be executed by TNO and Seaway7 and supported by various GROW partners, who can contribute with relevant knowledge.

EXPECTED RESULTS

The study will result in a Levelised Cost of Energy (LCoE) model for the entire offshore system at the substation metering point. The model will consider various storage capacities, with the reference point being the LCoE of the system without storage.

It will determine the optimal storage size, measured in both MWh and MW, in relation to the wind farm size for two energy system scenarios based on power market model simulations with TNO's EYE model. Additionally, we will present the net present value of the system for both scenarios with and without storage. We will also examine how introducing more storage systems into the electricity grid impacts the overall system performance and outcomes.

We will provide recommendations on incorporating storage into the energy roadmap to improve flexibility. The results will be shared publicly through web and LinkedIn campaigns. Based on the project’s insights, we will suggest follow-up actions.