In the next 20 years the installed capacity of hydropower in Europe will increase by around 86 700 MW. This is one result of a recent study by Trend Research, a German market research firm that assessed the hydropower potential of 18 European countries.

While only limited development of hydropower is possible in Sweden and Finland, a considerable expansion can be expected in Turkey, Austria, Switzerland and Romania.

Especially in Western European countries, the main potential lies in replacement, modernization and reactivation of existing hydroelectric power stations. Another approach is to construct small hydropower plants. Currently, there are many new technological ideas.

For example, the water vortex power plant (pictured). The first water vortex power plant of the Genossenschaft Wasserwirbelkraftwerke in Schöftland/Switzerland has been operational since November 2009. In this system, water from a river flows into a round, 6.5 m wide rotation pool. The draining outlet is located in the middle of the basin. The flowing water creates a vortex into which a slowly rotating rotor is placed. The power plant operates at a flow from 0.8 to 2.5 m3/s and with a height of fall of 1.7 m. It provides an average output of 10 kW, corresponding to an annual electricity production of 90,000 kWh, enough to supply about 20 homes with renewable energy. The rotor of the water vortex power plant turns with 16 to 22 revolutions per minute. It is permeable, so small flotsam and fish can pass safely through the system, both upstream and downstream. A water vortex power plant costs around 260,000 euros.

Another example is the moving, over and under flowing hydropower plant. The company Hydro-Energie Roth has developed a movable underwater power plant that can be installed into existing dams with only minor changes. The turbine and the generator are combined in a mobile machine housing. The so-called power house is placed under water in the flow direction, so that it can be washed over and under ‑ a new feature that increases the energy output and simultaneously serves the flood protection. Depending on water conditions, the power plant is pivoted, whereby an opening is released below the power plant. This makes it possible to lower the water level in front of the weir, for example in case of floods. Furthermore the silt at the riverbed can pass through without any additional structure. This solution improves the ecological balance of the impoundment and counteracts the silting of the dam area. At low water the lowering of the power house is used to gain the maximum energy. The construction is particularly environmentally friendly, because fish can pass over and underneath the powerhouse. The engineers have been thinking of the migration of fish against the current, too: Through a step-like fish passage, the animals can overcome the distance. According to the company the costs of the plant are about 30 percent less than of a comparable conventional system, but it produces eight percent more power. After a pilot plant that went into operation in 2009, two commercial power plants of this type have been built in Germany, a third is under construction. The largest of these has a capacity of 500 kW. It is expected to generate approximately 2.75 million kWh of electricity a year. This corresponds to the power consumption of more than 600 four-person households. Capital expenditures amounted to 3.8 million euros.

The third example is the electrical buoy. This is a mobile hydro power plant from the Austrian company Aqua Libre. It is equipped with a rotor with a horizontal axis in a funnel-shaped flow channel. The whole system floats free in the river, tethered by ropes. The current-buoy does not require dams or dikes and can always be positioned at the point with the best flow. The company currently has two versions on offer: a small power buoy with a rotor diameter of 1.5 m and a large one with 2.5 m. The rated power of the small turbine is 15 kW, the large turbine has a capacity of 40 kW. The buoy, fixed at the riverbed, requires a flow rate of 2.2 m/s. The annual output of the small buoy is approximately 100,000 kWh, the large buoy produces about 250,000 kWh. Including installation and grid connection the 40 kW unit costs 250,000 euros. The turbine rotates so slowly that fish are not injured.

The final example of innovative small hydro models is the wing-flow power plant. Through the beating of their wings and fins, birds and fish produce a forward force that speeds up the water or the air in the opposite direction. Scientists at the University of Kassel have reversed this principle; they have built a wing that is moved by the stream of flowing water in a hydro power plant. The energy is transferred by a lever arm to a crankshaft, which drives a flywheel and a generator. The aim is to construct a flexible, environmentally friendly power plant that efficiently converts the kinetic energy of the water into electricity, with minimal investment and operating costs. Currently, however, only a very small prototype exists with 2 watts. A larger testing facility with a capacity of about 100 watts is under construction.


 (picture: water vortex power plant.jpg)