Utility Week

UTILITY WEEK | JUNE 2021 | 13 Speical report on storage addressed when designing a turbine for use with hydro- gen, the rst being its higher reactivity and ame velocity when compared to natural gas: "That pushes the ame closer to the burner, so the ame is shorter and there is a risk that you get a ashback and that the ame eats itself into the burner and damages it." The second main issue is the higher ame tempera- ture: "If the combustion gases are not perfectly mixed, you get local hotspots and that increases the NOx emis- sions." Zindel says new burner designs are therefore required for 100 per cent hydrogen. The pipes feeding fuel into the turbine also need to be changed, with di‚ erent sizes and materials, as well as the auxiliary systems, including re protection and com- bustion monitoring. That said, most of the turbine itself can be kept the same: "Outside of the combustion chamber and the fuel system, there is not really any change required so you can continue to use the compressor, you can continue to use the turbine sector. The generic set-up of the gas tur- bine itself is not an„issue." Zindel says new plants can be designed to be hydro- gen ready with relatively little upfront cost, signi cantly limiting the cost and disruption of future retro ts. Whether retro ts will make sense commercially for exist- ing plants is less clear cut and will depend on their e† - ciency and remaining lifetime. Siemens has already begun testing redesigned burn- ers and will start trialling a small 100 per cent hydrogen turbine at a paper mill in France in 2023. Zindel says he expects to be able to run medium and large turbines on 100 per cent hydrogen by the end of the decade, although commercial operation at scale depends on how quickly the market develops. The newest CCGTs can generate power at percentage e† ciencies in the low to mid 60s and Zindel says this is also achievable with hydrogen. He says this would result in a roundtrip e† ciency, from power to hydrogen and back to power again, of slightly below 40 per cent. Mechanical energy storage Pumped hydro storage Pumped hydro storage works by transferring water between two reservoirs at di‚ erent heights, pumping it uphill to store energy and releasing it back down to gen- erate. It is currently the largest source of storage in the power sector, providing more than 2.8GW of generation capacity and 24GWh of storage capacity spread across four plants in Scotland that were built from the 1960s to 80s – Dinorwig, Ffestiniog, Cruachan and Foyers. The roundtrip energy e† ciency of pumped hydro storage is speci c to each plant but typically averages between 70 and 85 per cent. In October last year, SSE Renewables received con- sent from the Scottish government to build Britain's rst new pumped hydro storage plant in a generation. The Coire Glas facility, named aŸ er the valley which will be dammed to form the upper reservoir, will be able to store 30GWh of energy, with water being dropped by a height of 500 metres to nearby Loch Lochy. continued overleaf Skeleton Technology's ultracapacitor Highview power's liquid air storage system

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