From the upper part of the reservoir, the flow descends through the channel, along the way rotating the turbine connected to the generator – this is the principle of a regular power station operation. If the station is a pumped storage, water can also be pumped to the upper pool. This is a common scheme: there are more than 150 HPSs in Russia alone, and the percentage of hydropower in the country is about 20 percent.
Together with solar energy and wind, water resources are considered renewable energy sources. The scientists are searching for alternatives to dams and opportunities to use water for energy generation in a more diverse way.
Ebb and flow
In July, the media reported on the development of a tidal power plant project in Kamchatka. According to the plan, the station will be located in the Penzhinskaya Bay of the Sea of Okhotsk, the energy from which will be used for the production of hydrogen. The resumption of the project, which was first considered back in the Soviet years, is associated with a proactive low-carbon agenda. According to calculations that were carried out back in the 1970s, the capacity of a tidal power station can be up to 100 GW. If the project is implemented, the station can become the second tidal power station in Russia.
The first and so far, the only tidal power station in Russia was built during the Soviet Union. The experimental tidal power station was finished in 1968 on the Barents Sea shore. Nowadays, it is preserved as a monument to science and technology.
Tidal power stations are built in the places of the greatest tides. It is the water level difference that allows us to generate energy – according to calculations, for economic expediency it makes sense to build a tidal station in areas where the sea level fluctuates by at least 4 meters. For example, the Penzhinskaya Bay has one of the highest tides observed – higher than 13 meters.
A tidal power station is a dam that is built in the sea bays or at the mouths of flowing rivers. After the reservoir is blocked, a pool is formed where the water level fluctuates depending on the tide height. Turbines with generators are installed in the dam culverts, working in both directions under the influence of water pressure.
Tidal power stations use a stable and inexhaustible source of energy, do not pollute the environment with emissions, and are potentially safe for the population. The disadvantages of tidal power plants are the high cost of construction, unstable energy supply, and relatively low efficiency.
On the tides
Giant red water snakes made of metal off the coast of Póvoa de Varzim in Northern Portugal provide electricity to thousands of households. The Pelamis Wave Energy design is named after a marine inhabitant – the Pelamis platurus snake, which spends its entire life in the water. Like a reptile, the devices do not leave the water and look like they bend on the waves.
Almost 150 meters long and three and a half meters in diameter. Several sections are connected by hinges; when the floating structure bends at the joints, hydraulic pistons pump oil, rotating the generators. The structures connected by cables provide the total power to the shore.
However, this is not the only system of the wave power plant. Another solution – a pipe placed in the path of the waves. The incoming water turns the turbines transmitting the momentum to the generator. In a similar system, the turbines are rotated not by water, but by air, which the water pushes out of the closed space of the pipe. Alternative designs use the pumping force of the wave: floats mounted on a single shaft swing on the waves, driving the turbine into motion.
Wave energy is an infinite and safe source of energy. At the same time, individual designs of wave power plants are potentially considered as wave dampers that can protect the coastal zone. With obvious advantages, the share of wave energy in the world remains at a low level: according to estimates, only about one percent of all energy is extracted from wave energy. The first experimental wave generators in Russia were launched in 2014 in Primorsky Krai.
On one side of the aquarium, there is a seawater, on the other – freshwater; in the middle, there is a membrane, permeable to water molecules, but not to salt. In such a system, freshwater will begin to seep through the membrane in an attempt to balance the concentration of the solution on both sides of the membrane. This is a physical process called osmosis: Greek for “push” or “pressure.” The osmosis effect was discovered by the French physicist Jean Antoine Nollet in 1748. And after two and a half centuries, the effect started to be used to generate electricity.
The tanks with seawater and freshwater of the osmotic power plant are separated by a modern membrane. The idea of creating an OPP was suggested back in the 1970s, but then the materials did not allow making a membrane, on the one hand, strong enough not to break under pressure, and on the other hand, with sufficient throughput so that the osmosis process would not be delayed for a long time.
The only experimental osmotic power plant to date was launched in Norway in 2009. Freshwater, mixing with saltwater through the membrane, creates a pressure that is sufficient to rotate a turbine. Waste seawater, diluted with freshwater, is discharged back into the sea, from where seawater is abstracted again.
The osmotic power plant does not need the sun or wind, does not produce greenhouse gas emissions, and generates stable and regular power. However, its location is very limited – the construction site of an osmotic power plant requires constant access to both sea- and freshwater.
Photo on the homepage: altenergiya.ru