One would suspect that hydro-electricity is a key example of renewable energy. Is it? And more important: is it sustainable?
Belgium does not comprise mountains or fjords. Instead we use a pumping plant in Coo-Trois-Ponts.
It uses electricity from the grid to pump water from a low reservoir uphill to an elevated reservoir,
with the intention to use it later in Frances turbines for peak production.
This type of conversion is not production, but rather a storage facility intended for grid stabilisation.
The efficiency is around 75%, which is even less than
the efficiency of a wall battery pack. One quarter of the input is simply lost. There is nothing renewable about it.
In mountainous countries, hydro means using rain collected behind a dam to drive a turbine.
This is truly a free energy source. It converts potential energy, supplied by the sun
in the form of evaporated sea water, into electricity. Not using the rain water accumulated behind the dam, would be a pure waste.
However, the capacity depends on the rain quantity. In dry periods, the level runs too low to operate. Norway produces over 90% of its
electricity in this way, but currently (2022) suffers from an extremely dry season.
But there is a bigger, long-term problem behind the horizon. European hydro plants not only depend on rain, but to a large extend also on melting snow and ice.
It appears now that the hydro capacity is being computed based on the mass flow of the melt water. Unfortunately, the melt water is based on
frozen capacities that were established centuries ago, and are currently no longer maintained. Less fresh snow combined with melting glaciers
limit the future capacity. This means that the availability of hydro-electricity
will fall, rendering the dams and turbines useless.
Tough luck, so. As the current production is based on tapping a decreasing melt water capacity, hydro-electricity is not sustainable.