Renewable Energy Challenge
In 2019, the share of electricity in final energy consumption was 19%, which according to Bloomberg could grow to 49% in 2050. This means a massive increase from 79 EJ to 192-194 EJ mainly driven by wind, solar and nuclear power . Surprisingly the Bloomberg report does not mention hydropower, which in 2019 accounted for a third of all final energy consumption generated by modern renewables. One wonders, what the role of hydropower could be in the decarbonization race. How big a challenge the road to net zero in 2050 is, illustrates the fact that the share of modern renewables in total final energy consumption in 2019 was just 11.2%, while fossil fuels attributed 80.2%, and others 8.7% .
Having lived in the Netherlands in the Rhine/Meuse/Schelde delta and near the North Sea for many years, and currently residing in Switzerland, I have witnessed the tremendous force of water. Hydropower uses that energy to produce electricity or to power machines. Did you know that close to 60 percent of Swiss produced electricity already comes from hydropower ? However, in countries with less elevation than Switzerland, seas with tides and currents, but also rivers and lakes have a potential for hydropower as well. Let’s review how and where hydropower can generete and store energy and how cost-effective it is.
According to Fred Ferguson, CEO of Waterotor Energy Technologies from Ottawa, Canada, water is both a powerful and a cost-effective clean energy source. His company develops innovative water rotors that extract energy from rivers, ocean currents, and tidal flows. According to Ferguson, hydropower is “830 times more powerful than wind” and it also “flows continuously”, as opposed to wind and solar energy . Waterotor power generators extract energy at an average cost of CAD 5-10 cents per kWh, compared to the average electricity price worldwide of CAD 18.7 cents (source: ovoenergy.com 2020). 
As the Waterotor story shows, hydropower can be generated in rivers, lakes, seas or oceans. A Quantum Tech HD clip reviews some interesting technologies :
Anliatec Technology 2-50 kW micro turbines in rivers and irrigation canals
Landustrie 4m x 6m hydropower screw turbines
Nering Industries 3 m x 1 m water wheels
Ocean Power Technologies moored sea buoys with a sliding top that moves with the waves
OpenHydro Group (out of business) vertical 2 MW sea bed turbines with 16 m diameter
JAG Seabell Co. 0.4-44 kW ultra low micro hydro turbines
Turbulent Hydro enclosed Hydro turbines for rivers and canals that don’t disturb wildlife
Waterotor Energy Technologies water rotors for slow moving water
The water reservoirs in the Swiss Alps enable a more or less continuous flow of hydropower and even allow for energy storage. Some turbines not only generate electricity, but in reverse mode also pump water to higher reservoirs, that can feed the turbines during times of peak electricity demand. Could it also be possible to apply these principles in flatter landscapes? In the Netherlands, when in winter, spring or even summer, the amount of water in the rivers exceeds its capacity, the so-called ‘uiterwaarden’ bring relief. These winter beds are elevated parallel rivers that fill up once the dike of the main river overflows and are emptied into the river once its level sinks. Raising the height of the summer dikes and installing two-way, lockable turbines could be an additional source of clean energy and energy storage. Couldn’t uiterwaarden-like reservoirs be an energy and overflow option for more countries?
As about 71 percent of the earth’s surface is water, hydropower has a huge potential to be a main contributor to decarbonisation. Even the tiny Netherlands has 6000 km of rivers/canals and 450 km of coast line, excluding the Dutch islands. Recent innovations like the Waterotor power generator prove that electricity prices can be very competitive. Governments can support the energy transition to hydropower by stimulating innovation, by regulation, and by infrastructure investment. See the recently published ‘San José Declaration on Sustainable Hydropower’ of the IHA (International Hydropower Association) . What if every ship would be equipped with reversible turbines that, once anchored or docked, could generate electricity? What if all rivers could have fixed or floating rotors and turbines? What if every oil rigg and offshore windmill could be equipped with hydropower turbines? Or, even better, what if underwater turbines and rotors could be installed in every river or canal, and at every coast? After all, who wouldn’t prefer the visual aesthetics of underwater equipment to windmills?
Hydropower has many advantages: water resources are wide spread around the world, technology is robust, proven and increasingly efficient, energy generation is flexible, operating cost are low, and plant life is longest. Its environmental impact is low and better than windmills. Special attention is given to protection of fish by creating parallel passes to turbines. Recent innovations have brought smaller, more affordable solutions allowing a deeper market penetration. Digitization further increases hydropower productivity, efficiency, integration and security. Therefore the hope that hydropower will be a major contributor to the energy transition seems realistic, a role that might be even bigger than anticipated.
 REN21; Renewables 2021 Global Status Report, Figure 2
 https://www.forbes.com/sites/robertreiss/2021/06/28/canadian-companywaterotorhas-designed-new-disruptive-clean-tech-to-produce-low-cost-electricity-from-slow-moving-water/ CAD = Canadian Dollar