Following up my roundup of renewable energy sources, it’s now time for a look at water power (also called hydropower and hydraulic power) and its main uses.
Please note: Although tidal power and wave power are also forms of water power, I think they’re interesting enough to merit their own posts later. In this post, I’ll focus on other ways to generate useful power from water.
The most used renewable energy source
Water power is, by far, the renewable energy source that is the most used in the world. At the end of 2006, around 60% of the world’s renewable energy was generated by hydropower. This number combines both small and large scale installations.
A few countries even get the majority of their electricity generated by water power, with the top three being Venezuela (about 67%), Brazil (about 85%) and Norway (about 98%).
Using water power
Roughly speaking, water power can be utilized in the following ways:
- By using the movement of flowing or falling water to drive or move something.
- By exploiting the salt concentration difference between river and ocean water.
- By exploiting the temperature differences between shallow and deep waters.
Flowing or falling water/Hydroelectricity
This is the most common way to tap into water power. A waterwheel or turbine is placed in the water stream. The water’s motion turns the waterwheel or turbine, producing some kind of useful movement or conversion to electricity. Some examples of this are:
- Waterwheels powering mechanical machinery (in an old-fashioned flour mill, sawmill, factory or similar).
- Water stored in a dam, being let out in a concentrated flow to drive a turbine that generates electricity.
- Water being forced to form vortices by obstacles in rivers. The vortices drive turbines that generates electricity.
Salt concentration difference/
Osmotic power
Several techniques for utilizing the salt concentration difference between river and ocean water to generate electricity, but the most common one is so-called “pressure-retarded osmosis”.
That sounds terribly complicated, but the principle is relatively simple: Salty ocean water and freshwater are pumped into a tank. Separating these two types of water is a semi-permeable membrane. As the freshwater is drawn across this membrane, pressure builds in the tank. This pressure is then used to drive a turbine.
Norwegian power company Statkraft has been developing this technology over the past 10 years, and now reckons they could use it to generate about 10% of Norway’s total energy need.
UPDATE: Statkraft has now opened the world’s first osmotic power plant at Tofte in Norway.
Temperature difference
This technology relies on the temperature difference that exists between the surface water and bottom water in the ocean (or other large bodies of water) to generate energy. The cold bottom water and warmer surface water is used to power a heat engine, such as the Sterling engine.
Next up: Wind power
That concludes this summary of water power uses. Being a summary, it merely skims the surface of the existing possibilities. Future posts will look closer at the various technologies and products that are available.
If you think I’ve missed something, or want to comment on anything else, let me know in the comments section below. Next up for a similar look is wind energy and the various ways to harvest it.
This post was tagged with: hydraulic power, hydro, hydroelectricity, osmotic power, water power