Can hydropower help ease Europe’s energy crisis?

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Te Loire, the longest river in France, was an apocalyptic scene this summer. Parts of the river network had completely dried up by mid-August; the rest was reduced to a problem. It had happened before but this year the timing was particularly bad. Energy prices had risen after Russia invaded Ukraine. Nuclear power production in France has been hampered by maintenance, repairs and low water levels in rivers used for cooling. And in mid-August, France’s river-powered hydroelectric plants produced just half the electricity they would normally produce in August (based on an average of the previous three years). That pattern played out across much of the continent. In 2023 gas prices will hardly remain high and the European energy crisis will continue. Could hydropower ease the problem next year?

There are three types of hydropower plants. Run-of-river plants use the flow of water to drive generators. They usually provide a constant flow of energy but as they do not store water for long periods of time they can only provide power that is generally in line with the flow of the river. The other two types of hydropower plant are more flexible. Reservoirs attached to hillsides provide storage that can be used when needed. And pumped storage plants are reservoirs that act like rechargeable water batteries: they push water up into a reservoir when power is free, usually at night, and let it down when high demand. Reservoirs and pumped storage can therefore help reduce peak prices by replacing gas-fired power plants when needed.

Europe’s hydroelectric plants generated 712TWh in 2021, about 16% of total electricity generation (see first chart). But so far in 2022, hydropower generation has fallen below 112TWh so far, compared to the same period last year, when drought hit the continent. Over the past 12 months the water level has been low in large parts of France, Spain, Italy and southern Norway. In Italy the shortage has been particularly severe. The run-of-river plants did not have much water to play with, and reservoirs were not filled to their normal levels (see second and third tables).

But it is not just the weather that has prevented power generation in 2022. Reservoirs started the year with lower than normal levels. When deciding how much water to release, storage hydropower plants take current and future electricity prices into account. In the second half of 2021, electricity prices began to rise sharply across the continent as gas prices rose. That may have encouraged plant operators to generate more electricity to make a profit, draining reservoirs below their normal level and leaving less capacity to generate power beyond 2022.

Fortunately, the outlook for 2023 is better. The last two weeks have been uncomfortably wet. That has helped to replenish reservoirs in most countries, although there is still a way to go in Italy, Spain and Portugal. The three-month forecast for Europe predicts a slightly warmer winter and just a little drier than normal. That should help too. And policy makers have responded too. Switzerland, for example, has bought parts of the water in reservoirs so that it has a backup power source in case of gas shortages in the winter. Portugal ordered 15 dams to suspend electricity production to replenish reservoirs; recent rains have allowed some of them to restart. Even the Loire and its tributaries are slowly recovering their normal water levels, to help generate as much electricity as possible in 2023.

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