Wind Turbine Energy Storage

Could a Wind Turbine Store Its Own Energy Inside Its Transmission?

Wind turbine energy storage tackles wind power’s biggest weakness. Turbines generate electricity when the wind blows, not when demand calls for it. Conventional wind farms simply feed power to the grid as it arrives. However, a University of Nottingham concept called WindTP takes a different route. It builds energy storage into the turbine’s own power transmission.

WindTP stands for Wind Driven Thermal Pumping. Professor Seamus Garvey invented it in 2013. CNR contributed CAD and mechanical design work to the programme. That work is not recent, but the engineering remains highly relevant. This article explains how the idea works.

The Problem With Conventional Wind Power

A conventional turbine converts rotor motion into electricity straight away. The power reaching the grid therefore follows the wind, not demand. This mismatch creates real problems for grid operators. Wind output can peak overnight, when demand is low. It can also fall away during periods of high demand.

Battery storage offers one answer. However, grid-scale batteries remain expensive, and they wear out. Therefore, engineers have long sought a storage method that costs less and lasts longer.

How WindTP Works

WindTP replaces the usual path from rotor to generator with a closed gas circuit. Special compressors connect directly to the rotor. They draw gas from a low-pressure side at about 20 bar. Then they push it into a high-pressure side at about 500 bar. An expander lets the gas fall back to 20 bar. As it does, the expander drives the generator.

The compressors are deliberately very efficient and lose little heat. Consequently, the gas leaves them roughly 2.5 times hotter in absolute terms. The expander works in the opposite direction. Gas enters it about 2.5 times hotter than it leaves.

Direct drive also removes the need for a gearbox. That matters, because gearboxes see some of the highest loads in any turbine.

Storing Energy as Heat

Here is the clever part. Heat exchangers on both sides of the circuit connect to two thermal stores. A hot store takes heat from the high-pressure gas, or returns it. A cold store does the same job for the low-pressure gas. By moving heat in and out of these stores, the system banks energy or releases it. The designers stress that this is thermal storage, not compressed air storage.

The system can run in seven modes. In the simplest mode, wind power passes straight through to the generator. In other modes, the stores charge or discharge. One mode even charges the store from the grid, using no wind at all. In every mode, gas keeps circulating, compressed from 20 bar to 500 bar and expanded back again.

Why Stored Energy Changes the Picture

According to the WindTP team, the system can typically store 25 to 100 hours of rated turbine output. They also state that the marginal capital cost of that storage is under 1% of an equivalent battery’s, with a much longer lifetime. These are the developers’ own figures.

The main attraction is dispatchability. A wind farm with storage can choose when to release power. It can hold energy during quiet periods and generate during peaks. Furthermore, the same machinery handles both transmission and storage. This saves capital, and it avoids converting mechanical power to electricity and back again. As a result, a wind farm becomes a schedulable source rather than an intermittent one.

The Engineering Challenge

Turning the concept into hardware demands precise mechanical engineering. WindTP uses liquid-piston compressors and expanders. Each stage uses oil moving back and forth in pipes. Control valves open and close at carefully timed moments. The machines run slowly, which suits high efficiency. They must also rank among the most efficient compressors and expanders in the world.

Heat adds a further difficulty. Extremely hot gas sits close to hydraulic oil. Floating thermal spacers and thermal gaskets keep the two thermally apart. They must also seal against pressures up to 500 bar. Therefore, every seal, spacer and structure demands careful design and analysis.

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Where CNR Fits

CNR contributed CAD and mechanical design to the WindTP system. CNR also built and tested hardware in its own workshop for a related energy storage project that applied a similar principle.

Work like this reflects the engineering CNR delivers across energy, aerospace, automotive, defence and research. Concept development, CAD, mechanical design and hands-on testing all sit together. Novel systems also create new testing needs, which our article on wind turbine testing explores. If your programme needs that mix of skills, that experience is where the conversation starts.