The great Nikola Tesla many times in private conversations argued that people everywhere are surrounded by energy, it just needs to be able to use. Mankind has gone along the easiest path, taking from nature the most calorie-rich substances and burning them. The effectiveness of resource use is not high, but few people think about it, although Mendeleev pointed out the proportionality of the benefits of burning oil and banknotes. Nevertheless, from time to time, the learned world remembers the past experience or comes up with something new. So there are fields of windmills with generators, solar batteries, tidal and geothermal power plants, other sources of energy using natural forces, which are now almost completely wasted.
Energy of natural forces
Wind, waves, lightning, hurricanes, tornadoes, volcanic eruptions represent large-scale movements of masses and energy of air, water, heat and static electricity. If it is possible to learn to take away from nature even a part of its strength for the needs of our growing civilization, then for the future of mankind one can be calm. Otherwise, with growing consumption of non-renewable resources, their depletion is inevitable. Someday coal, oil, gas, uranium, plutonium and other minerals will run out, and there will be a planetary energy collapse. One of the possible ways out of the prospective crisis is rightly considered to be tidal power plants. As their name implies, they consume the energy of huge masses of water flowing from one part of the World Ocean to another with a certain periodicity.
What is the tide?
From time to time, the level of the sea rises and falls, people have known for a very long time. With this phenomenon faced the ancient seafarers. Having once led their ships into a cozy lagoon and trying to get out of it again into the sea, they suddenly ran aground, which had not been recently. There were legends about spirits moving underwater reefs, rocks, beating about the stem by the wave of mermaids and other fascinating myths. Soon the strand again disappeared somewhere, and the ships moved on. The discovery of astronomical regularities led to the realization of a mutual connection between the concept of the water level and the lunar phases. All explained the law of universal gravitation. Water was attracted to the Moon at the time of its approach to the Earth with a force inversely proportional to the square of the distance between the cosmic bodies. In terms of physics, tidal power plants should be called lunar. They use the energy of water movement, which in turn draws power from the only natural satellite of our planet. The sun, by the way, also contributes to this process, although it is further than the Moon, but the mass of the luminary is much larger.
Tidal mills, British and Pomors
Intuitively, mankind has learned the energy of tides long before the discovery of Newton's laws. Electric generators were not there, either. But the mills worked with might and main, the millstones of which were turned by wheels with blades, lowered into the water where the sea waves behaved most actively. Usually the place for the construction of similar food processing facilities was selected by ancient millers in the bays with a narrow neck. There, water flows turned unmoved mechanisms particularly effectively. There was a tide - the direction of rotation is one, and at low tide - another, the opposite, and the grain does not care how the millstones rotate, it is grinded in any case. At their core, tidal mills were the same windmills, only they worked not in the air, but in the water environment. These devices functioned in the British Isles already in the XII century, their appearance in Russia on the White Sea is known from the chronicles of the XVII century. Perhaps Pomors used the English experience when they saw these mills during their trade missions, but it is possible that they themselves thought it out, they were talented.
After fundamental discoveries in the field of theoretical electrical engineering, the question of practical industrial extraction of a new type of energy came to the fore. Rotate the generator shaft could steam machine, hydraulic screw axis or any other mechanical source with torque.
The simplest solution was a dam, similar to a water mill, using the difference in level potentials. In the XIX century, steam engines were also used widely, as were internal combustion engines. In 1913, the world's first experimental tidal power plant was built. The principle of operation of this energy source is still used today. The power of the generator, mounted in the Dee bay near the Liverpool port, was small, 635 watts, but it was not a bad start.
In 1935, Americans who were averse to innovation tried to build a more powerful aggregate of "free" energy, they invested a fair amount in the project, but the venture turned into a failure. The relief of the seabed has not been sufficiently studied, the soil has "swam", and efforts to isolate the water area of Passamakwodi Bay (East Coast of the USA) have been in vain.
But experience is always useful, experiments, even unsuccessful, are of benefit. In the course of the work, the engineers found out the necessary and sufficient conditions under which tidal power stations can work, in particular, a minimum level difference. It was four meters. Naturally, the more, the better, but if less, then it is not worth undertaking the construction of PES.
It is quite obvious that at low tide and high tide the direction of water flow through the turbine screw will be different. Moreover, the intensity of rotation also varies depending on the level of the working fluid in the energy-accumulating basin. In the design of turbines, these features of the concept of the engineers had to be taken into account. The generator shaft completely stops at the two "dead" points, which limit the duty cycle. Rotation starts only when there is a difference in levels, it is not important, positive or negative, as all tidal power plants work. Pros and cons are co-located in any systems and machines invented by people, nothing is perfect. It is important to correctly assess the advantages and disadvantages.
Than good PES for ecology
The main advantage lies in the fact that these stations do not need fuel, which means that there are no combustion products either.
The second plus is also very important. Whatever happens, and whatever cataclysms happen (earthquakes, tsunamis, volcanic eruptions, aircraft crashes, bomb strikes, terrorist attacks, etc.), the worst thing that can happen is the destruction of the working unit and the generator with the substation. Other consequences, such as a fuel spill, a radioactive coolant and something else terrible can not be due to the absence of dangerous technological agents.
The third positive side, which favorably tidal power from hydroelectric, for example, is the principle work that lead to respect for the fish wealth of the country. Part of the plankton, of course, dies with the passage of the intakes, but not more than one-tenth (for comparison: the passage of the blades of hydropower plants does not stand up from 83 to 99% of the aquatic microfauna, the main feed of fish).
Fourthly, the ice situation practically does not affect the operation of PES.
Fifth, the salinity of water remains almost unchanged.
And the sixth ecological moment is that the inevitable structural disturbances of the bottom arising during the construction are fully "healed" in two years with the complete restoration of the life of the hydrobiosphere.
The only tidal power station in Russia and the French PES "Rance" have shown by their examples that the prime cost of the "energy" produced from "water" is the lowest. In addition, the productivity of enterprises in the highest degree is stable and does not depend on any political or macroeconomic shocks. The work of PES is affected only by the motion of cosmic bodies. The increase or decrease in the load levels and volumes of energy consumption by consumers also does not violate technological operating procedures.
The technology of construction, called floating, allows creating power units not in the place of the future work of the stations, but in coastal docks, and only then tow tidal power stations in the desired area of the world ocean. Thus, the installation process is seriously simplified.
The greatest amplitude of sea level is observed in the sea bays, in which natural semi-enclosed basins are formed by the coastal relief. The change in the direction of rotation of the turbine is technically realized by means of a variable pitch of the blades, in other words, by their rotation relative to the axis of rotation. Typically, turbines have the ability to switch from generator to pump mode, depending on the situation and the phase of the process cycle. The main disadvantage, which is the uneven performance, is offset by a common unified power system, part of which are tidal power plants. Advantages and disadvantages of this technology in comparison still persuade power engineers and ecologists in favor of PES.
Why are there not enough of them?
If everything is so wonderful, then why are the coasts of all the continents not saturated with these wonderful, environmentally friendly, harmless and non-dangerous, but very useful facilities? Why does mankind still smoke in the atmosphere with fuel oil, coal and other exhausts, risk the new Chernobyl and Fukushimi, destroy the blades of turbines of hydroelectric power stations and slow the movement of rivers, leading to environmental disruption? Greenpeace insisted that modern needs of the inhabitants of the planet, together with enterprises five thousand times, can only be covered by tidal power plants. In the world, however, they can be counted on the fingers.
Expensive and Beneficial
The fact is that they are very costly. Each PES costs as much as 150% more than the HPP of the same capacity. The cost of ruined fish and environmental damage is not considered. It is possible to treat the organization of Greenpeace differently and not support its activities in all ways, but it is probably worthwhile to listen to the opinion of its members. And some have already done it.
The share of energy currently provided by all tidal power plants in the world is negligible, but it tends to grow steadily. Now there are a little more than a dozen of them, they have different capacities, but only the principle of action unites them.
Here is their list with specification of the characteristics, country and year of commissioning:
Another five operating Chinese stations were not included in the list due to low power.
At the same time, experts estimate the total potential of hydropower energy in a million megawatts, obtained without the burning of organic fuels or nuclear reactions.
Kislogubskaya tidal power plant worked until the complete wear of the aggregate and in 1994, was subjected to conservation, but in the beginning of the third Millennium it was decided to reconstruct for the purpose of conducting experimental studies. The issue of alternative receiving huge amounts of energy the leadership of the Russian Federation pays serious attention, despite the high cost of construction of industrial units.
The only tidal power station in Russia is just a base for technology development. There is a project for the construction of the world's largest Penzhinsky energy node in the Sea of Okhotsk with a total capacity of 135 GW. It is supposed to be used for obtaining huge amounts of hydrogen, necessary for obtaining synthetic organic fuel, which does not form harmful chemical compounds during combustion. This project requires serious investments, but promises to give an effect whose significance today is even difficult to assess.
The question of when exactly the Penzhinskaya tidal power station will be built in Russia remains open.