by Yakov ULANOVSKY, Dr. Sc. (Tech.), President of Signmet Scientific-Production Group of Companies
Yunys KASHFRAZIYEV, Cand. Sc. (Tech.), Dubna International University of Nature, Society snd Man
According to International Energy Agency (IEA), with the current energy consumption expansion (and it's redoubled every 10 years), available coal reserves will be sufficient for mankind for 250 years, oil resources, 40 years, and natural gas stock, 65 years. Against the background of oncoming deficit of traditional fuel resources many countries aim at using renewable energy sources, develop technologies of their production. Wind-power engineering, the most safe for people and environment, arouses particular interest. Its resources are extremely great and wide-spread, including in Russia. However, in Russia only use of autonomous wind power plants for work in local networks is economically sound for the time being.
Technically available total wind power is estimated at 53,000 TW/h a year, which exceeds the world consumption approximately four times. The USA, Denmark, Holland, Germany, India and Spain can use this resource best of all: more than 3/4 (three-fourths) of wind-driven power plants fall to their share.
The "Wind Power Monthly" magazine has published a review from which it's evident that by the end of 2005 total power of wind-driven power plants amounted to more than 17 GW, while sale of relevant equipment would amount to USD 13.4 bln in 2005 - 2009 only for coastal electric power plants. The dynamics of incremental cost reduction of wind power plant network is demonstrative: during 1981 - 2000 costs for their creation reduced from USD 2,600 to 800 per 1 kW due to rise in turbine power, improvement of their manufacturing process, and more thorough selection of place for wind-driven power plants location.
The analysis of wind power production conditions in the world shows: in the developed countries it's an independent, fast-paced industry, though specific cost of energy output exceeds the figures of hydroelectric and heat power plants. It is interesting that it is more developed in the countries importing oil, gas and other resources which wind doesn't replace but supplements*. In so doing, produced plants, mainly, network ones, are designated for operation in large energy systems. Finally, the states interested in wind energy development promote this process by introducing particular benefits.
PROSPECTS FOR NATIVE WIND POWER ENGINEERING
Unfortunately, in Russia this industry hasn't been created yet, though we dispose of considerable possibilities for its making, including those areas which lack centralized electric power supply. High average annual wind velocities are characteristic of Kamchatka, Sakhalin, Chukotka, Yakutia,
* See: P. Bezrukikh, "Prospects for Renewable Power Production," Science in Russia, No. 4, 2003, - Ed.
the coasts of Arctic Ocean, Gulf of Finland, the Black and Caspian seas.
Moreover, the first in the world wind-driven power plant - Balaklavskaya with a capacity of 100 kW - appeared in our country in the 1930s (unfortunately, it was destroyed during the Great Patriotic War). Production of various serial wind-driven power plants of 3 - 4 kW capacity started then. At the end of the 1960s it was discontinued, but at the end of the 1980s the idea of gradual replacement of organic fuel by renewable energy sources and, first of all, wind became topical for the USSR again. It was supposed that with steady business environment their use could have increased by 6 - 14 times. Today there are also plans of state support for domestic wind power engineering: several government regulations have been adopted. North Development Program has been worked out. However, it's still a long way to practical steps.
Nevertheless, today our country develops and manufactures wind-driven power plants, though in small quantities, pilot lots (many firms have no financial possibilities of arranging full-scale production that would allow to cheapen them and of certifying them). However, there are developments relating to new technological solutions, and this is a result of the search of a number of research, design organizations and some private enterprises.
Meanwhile, a number of firms from Germany, Denmark and USA already supply wind-driven power plants to Russia for several network wind power stations of not more than 15 MW for experimental operation. However, there are hardly any prospects for this direction in our country within the next 10 - 15 years. First, the price of energy produced by wind-driven power plants is 2 - 3 times higher than that of energy from traditional sources. Second, so far the country doesn't lack such resources as oil and gas. Third, work load of our power systems amounts to about 50 percent of their capacities. Fourth, there is no state support for the industry under discussion. And, finally, population and commercial structures are not ready for efficient use of energy, mainly, due to its low cost (when produced in network).
As to local power systems, the situation is different: presently, we have dozens of thousands of them and, as a rule, they are based on diesel electric generators. Vast distances and under-population in the most of the country's territory are in favor of development of these power systems. However, people living in remote villages, farms or, say, attenting to distant pasture-lands can't take advantage of electricity because of its high price due to the difficulties of fuel supply. Wind power engineering becomes competitive under these conditions. Wide use of autonomous wind-driven power plants is restrained only by their high prices - USD 3 - 5 per 1W which can be reduced only due to new technical solutions and organization of serial production.
What do we mean speaking about the making of native wind power engineering as industry? The opening of new and modernization of current productions, personnel training, creation of all-Russia standards and norms, certification centers. A market of wind-driven power plants is required. Service facilities must start operating. Finally, we can't do without advocating renewable energy sources. What shall we begin with?
In our opinion, within the next 10 - 15 years there is a need for developing and manufacturing autonomous wind-driven power plants for operation in local networks together with other energy sources. This would allow to occupy a niche which is vacant now in the world production: practically, they do not manufacture such plants in other countries. As to network wind-driven power plants, it is expedient to meet the needs in them through import. However, wind power engineering state development program supported by relevant legislative base must become the foundation. Introduction of benefits for manufacturers and customers of wind-driven power plants must become one of its main items.
THE LEVEL OF SOUND PRESSURE
At the end of the 1990s a department of wind power engineering was established in the structure of Signmet Scientific-Production Group of Companies (Moscow). Here work highly skilled engineers with many years' experience in this field, which has allowed them to develop several wind-driven power plants of original design for a short period of time. Two of them - SW-2/5 and SW-20 with power output of 5 and 20 kW, accordingly, were brought to serial production. At the heart of developments there are high technologies of defence industry owing to which they were given perfect consumer qualities. What problems did specialists have to solve when designing, producing and improving this equipment?
Despite the fact that till the 1930s there were more than two hundred thousand (!) windmills in Russia, and the fact that abroad wind-driven power plants are also widely used today, in our country such innovations often meet opposition. What are arguments of opponents of this industry? First, wind-driven power plants create unbearable noise, the tips of their blades allegedly move with supersonic velocity. Second, this power supply is not reliable as it depends on the whims of weather. Third, to locate wind-driven power plants, there is a need in alienation of considerable territories, ecological damage is possible, namely, irreparable harm will be done to populations of wild birds and insects. Certainly, the above mentioned isn't invention but there are problem-solving techniques.
Let's start with noise which, unfortunately, accompanies a great deal of human inventions. Any moving body while swishing causes a sound effect: thus, people when scampering feel noise in their ears. Here one should have in mind two things. It's well known that the less streamlined the form of body is the higher is sound pressure created by it. In modern wind-driven power plants aerofoil profiles with high quality of surface are used, which allows to reduce a level of noise to minimum. Our goods aren't inferior to the best samples of foreign and native equipment in this area.
And there is another thing. The quicker blades move, the more is sound pressure created by them. However, with rotational acceleration of wind wheel its technical characteristics improve. A great deal of mathematical models and experimental studies in our country and abroad have allowed to find the golden mean. It is established that if the tips of blades move slower than 70 - 80 m/sec (for information, sound velocity in the air is approximately 340 m/sec), the created noise complies with the most severe requirements-it does not exceed 60 dBA. Thus, the maximum working speed of rotation of SW-2/5 wind wheel 4.5 m in diameter does not exceed 160 rpm - blade tip does not move quicker than 37.7 m/sec. This is approximately twice lower than the limit accepted in the European countries.
A low-speed generator is installed in our wind-driven power plants, while speed increaser is absent. Accordingly, there is no noise usually created by this unit. During certification tests a level of noise from wind-driven power plant was 45 - 48 dBA, like during quiet conversation. Hardly anyone will be able to separate it from general background created by wind. For plants to start generating noises in infrasound field, they should be equipped with special devices like air buzzer: for example, specially designed fences should be installed in front of a wind wheel or behind it. It's evident from the above-mentioned that noise is not a serious argument against wind power engineering development.
WHIMS OF WEATHER
If traditional sources - thermal, gas turbine, diesel and nuclear stations - produce the required quantity of power depending on fuel supply, wind-driven power plants can only produce as much as one can "take" from wind stream at the moment. Unfortunately, it's impossible to accumulate wind like they accumulate water at hydroelectric power stations. A question arises: what is to be done when there is no wind? It's indeed choppy (let's remember weather forecasts).
Nevertheless, the wind is quite predictable and ruled by certain mathematical laws in each area of the earth surface. Long ago specialists carried out necessary research in all regions of the planet. There are such factors as average annual velocity of wind, distribution by months. It's known what time of day its velocity will be higher or lower. These factors are united in a special cadastre and can be obtained at the nearest meteorological station. Disposing of such information, one can create a power complex based on wind-driven power plants ensuring complete continuity of service of the consumer during the whole year. Certainly, ideally, apart from electric batteries and diesel electric generator which must provide the consumer with electric energy during no-wind conditions, wind-driven power plants should be supplemented by, for example, solar batteries. This approach will reduce a number of accumulators. Moreover, as a rule, no-wind weather occurs with clear sky. However, one should not doubt that wind-driven power plants will reliably provide houses with electric energy.
However, it is compulsory to observe some conditions. The most important of them is to correctly locate a plant. For this it is necessary to estimate the wind potential and
The effect of structures on the wind velocity along the wind wheel's axis.
class of openness of locality; to define whether there are shading objects nearby, at what distance they are located; to take into account availability of open water areas. The buildings located close to wind-driven power plants have an effect on wind velocity, at different heights to a various extent. At times we can observe a choppy change of its velocity and sharp change of wind direction (so-called stall whirlwinds). However, this is not all. When choosing a position for a plant, one should take into account the peculiarities of terrain streamlired by a wind: strange as it may seem, even on the most open territory one can find a place where there will be dead calm - so-called "wind shadow." The equipment's smooth operation will depend on how optimally it is located.
As it is known, the power of wind stream is in direct proportion to its velocity cubed. If with 1.5 m/sec it is 2 W/m", then with 3m/sec it will increase 8 times and will be 16.5 W, while with 6 m/sec - about 130 W (a man of average opportunities can have such a capacity for a long time). While with wind velocity of 12 m/sec, power of stream will a little exceed 1 kW. Certainly, it cannot be used entirely. Theoretically, approximately 59.3 percent of power can be transformed into useful power, while practically not more than 51 percent, which is reached with the wind-driven power plants developed by the engineers of Signmet Group. Thus, the plant SW-2/5 becomes efficient with the wind velocity of 3 - 3.5 m/sec, while with 9.1 m/sec its generator already develops power of 2 kW.
The enumerated data show that the aim of some manufacturers of plants to reduce the minimal working wind velocity is rather explained by psychology of human being than it has economic basis. Moreover, the reduction of wind stream velocity entails not only the fall of its energy, but also decrease in generator efficiency. If the manufacturer of wind-driven power plant states that its designed speed is 10 m/sec, then theoretically this plant cannot produce electric energy with wind velocity of less than 3.7 m/sec.
A few words about the days when the wind is slower than the minimum working speed of wind-driven power plants.
In Moscow Region where annual average velocity of wind is about 4 m/sec, duration of no-wind conditions (wind velocity is less than 3.7 m/sec) can last for about a week with a probability of 95 percent. Therefore, the capacity of electric batteries must be calculated for this period, which is quite realizable.
Unfortunately, to locate large network wind-driven power plants, considerable areas are required, and alienation of land is inevitable. However, when using small, autonomous plants, this problem does not exist. Say, the wind-driven power plant SW-2/5 will occupy 18 m2and in fragments. In this area it will need five points of 0.4x0.4 m located in the center and in the corners of a square with a diagonal of 6 m. In the rest of the territory it is quite possible to arrange a lawn or a vegetable garden. Even bushes of up to 2 m long will not impede the general work. The foundation of SWD-20 plant occupies the area of 16 м2. As its main part is below the ground level not less than 0.2 m, the territory of complete alienation is only 2 - 3 m2.
Does wind power engineering cause damage to populations of wild birds? Here it is worth making two examples. In the 1980s, to provide local fish-packing factory with hot water, more than 40 wind-driven power plants with a capacity of 4 kW of Scientific-Production Association Vetroen were installed in Saaremaa island (Estonia). This is a favorite place of nesting for gulls and other birds. The representatives of Danish test center Renzo watched how gulls and crows freely flied across a spinning wheel of local wind-power plants. Only three birds perished there during 15 years, having struck against the blades of wind-driven power plants (near power transmission lines this figure is several times higher).
Death of insects is the more serious argument. However, the same happens on highways. Moreover, observations of many years do not confirm the fact. Thus, in California in the area where a great deal of such plants are located, a number of insect-eating birds increased more than twice
for almost a decade (the end of the 1970s - middle of the 1980s). Therefore, there was enough food for them there.
THE ADVANTAGES OF AUTONOMOUS WINDPOWER PLANTS
Today, the wind-driven power plant SW-2/5 created by us has passed certification tests. Owners of private houses can use it: there will be enough energy to connect practically all household appliances-lighting, video and radioelectronic facilities, electric tea-kettles, irons, vacuum cleaners, washing machines, electric drills, etc. It will be useful for navigation, weather, radio-relay and other autonomous stations located in the areas which are remote from united electric network.
When developing this plant, we tried to optimize its main parameters for the areas with low potential of wind (annual average wind velocity of 4 - 5 m/sec): even then it is repaid within six years, and in the more windy regions this period is reduced to three and less years.
In summer of 2005, the storm with wind velocity of up to 28 m/sec came down on the town of Dubna, Moscow Region. Many dwelling houses and household structures were damaged, more than two thousand trees were felled down, high-voltage electrical line was destroyed - and a part of population was left without electricity for more than 6 hours. However, the SW-2/5 installed in our wind testing ground within the limits of the town remained in operation and stood the test honourably.
The plant described produces 20 - 30 percent more electric energy than the best world samples. Thus, under the conditions of Moscow Region it produces 2,581 kW/h per year (this figure does not amount to more than 2,000 kW/h with our competitors), that is 215 kW/h a month, meeting average requirements of a family of 5 - 6 persons living in a three-four room apartment. While in the more windy regions the SW-2/5 will produce much more electric energy the excess of which can be used for other household needs, for example, heating and getting of hot water.
As a rule, manufacturers use centrifugal regulators of speed of wind wheel rotation at small wind-driven power plants, where its blades or special loads are used as a detector element (in such cases very high demands are made on their constructive weight characteristics). To reduce the mass of the loads, some firms "place their stake" on high speed of rotation. For example, with the wind-driven power plant 2000 of CJSC SKB ATIC it reaches 800 rpm (nominally, 620 rpm) with wind wheel diameter of 3.12 m.
In the SW-2/5 proposed by us the blades act as a governor component of wind wheel, whose aerodynamic characteristics are sensitive parameters, and they can be controlled. This allows to stand speed fluctuations in a rather narrow band: it changes up to 8 percent even in cases of artificial interferences (cable breaking, sudden engagement of load of a size corresponding to electricity generating capacity). It is worth mentioning that the similar principle was applied even in the 1940s in an experimental wind-driven power plant designed by the Central Aerohydrodynamic Institute named after Professor N. Ye. Zhukovsky. However, due to complicated control mechanism they couldn't duplicate this system then. Today our specialists managed to design a wind wheel blade with aerodynamic parameters allowing to keep a simple mechanical part and reduce control to a minimum, which is significant for serial production.
Low speed of wind wheel rotation together with high quality of unit and device production increases reliability and endurance of the plant. Practically, one can do without maintenance service during the whole operating life: it is assembled, put into operation and then it operates without human intervention. One has to only control tension of the cables anchoring its tower. Their length changes as affected by temperatures, which means that in summer they shall be tightened up, while released in winter. As experi-
ments demonstrate, the SW-2/5 can operate for more than 15 years planned by the manufacturer.
Engineers have provided this wind-driven power plant with an "intellectual" charging device. It "looks after" the behavior of the plant, and when the power produced by it falls as a result of wind speeding down, it proportionally reduces charging current of accumulators, excluding overload and holdup. Owing to this technology, wind power, in particular, breeze, is used at the most. The charging device is combined in a power generating unit with inverter*, and at the output the consumer obtains single-phase current of 220 V, 50 Hz with the maximum power of up to 5 kW.
It should be noted that when creating the SW-2/5 some problems relating to gondola position holding in the direction of wind arose: gyroscopic force moments** emerging while the wind-driven power plant operated turned off the wind wheel from it. The matter is the gondola (reservoir for locating the facilities of automatic checkout and regulation of the system) was designed according to so-called "without rear end" scheme, with a flexible tower (these solutions significantly win with relation to the plant's weight), so it has low inertness. However, a way out was found: to reduce this effect, hydraulic oscillation dampers*** were introduced.
The described technical solutions were presented at EUREKA-2005 innovation exhibition in Brussels, and experts appreciated them - Signmet Group of Companies was rewarded with three gold medals and Grand Prix for the SW-2/5.
POWERFUL PLANTS FROM RUSSIA
Apart from small autonomous plants, we have developed powerful wind-driven power plants SWD-20, SWD-30 and SWD-40. They are designated for the consumers remote from electric systems and allow to produce qualitative electric energy with parameters of 230/400 V, 50 Hz, three phases. At that, construction SWD-20 (as well as SW-2/5) is optimized for the areas with low wind potential, while SWD-30 and SWD-40-with high one, that is with annual average velocity of wind of more than 6 m/sec. We hope they will be widely applied by the consumers who presently use diesel electric power units and are willing to ensure their smooth operation and save fuel.
These powerful wind-driven power plants should be used together with diesel electric generators and solar batteries, which guarantees high quality of energy by tension (220 V ± 5 V) and frequency (50 Hz ± 0.1) due to use of the inverter built on modern element base using semiconductor technologies. All the three plants can have different configurations, and, depending on customer's demands, operate autonomously.
They allow to create wind electric stations with a capacity of up to 400 kW capable to provide with energy remote weather stations with their infrastructure, frontier-guard stations and military garrisons, villages and other economic structures. Their annual electricity production is much higher than the data of the world best analogues. This is reached due to two technical innovations. First, plastic blades of high quality with special covering and particular aerodynamic and geometric parameters are used. Second, the latter is optimized by using original software and counting on the highest possible efficiency in the working range of wind velocities.
A few words about the construction of SWD-20, SWD-30 and SWD-40. These are horizontally-axial plants with a three-blade cone wind wheel which sets to wind independently. The latter is located behind a tower and fastened on a freely rotating gondola located in it. Its three-blade structure allows to significantly reduce wind-driven power plant vibration emerging from gyroscopic loads and, as a result, to improve reliability and mean life of the plant. The blades of wind wheel are rotating. Owing to them and horizontal position of an axis, the highest possible production of electric energy, major mean life, minimum weight and complete self-control are achieved. The researches have shown that this plant is more acceptable for work with isolated load.
So, gondola runs about a vertical axis and freely orientates downwind with the help of wind wheel. The loads created by them are taken and passed to the tower by the same unit which includes a current collector and damper of gondola angular displacement (meant to limit acceleration of movement and ensure stable orientation downwind of the gondola and wind wheel). The damper consists of 6 hydraulic cylinders (with a set of plain washers equipped with throttling* holes) and a plain washer controlling movement of pistons inside them.
Tower is a conical metal pipe consisting of three sections. In its bottom part there is a thermally insulated cabinet to locate a generating set and accumulator unit. On one side there is a staircase leading to the catwalk where operation with the equipment located inside the gondola is carried out and blades are inspected.
Technological breakdown of the wind-driven power plant into separate functional units of less than 6 m in size and mass less than 1,000 kg simplifies its moving (any mode of transport fits it), while assembly and erection can be done on-site without special equipment.
We hope that the simple, reliable and comparatively cheap wind-driven power plants developed by Signmet Group of Companies will be widely applied both in Russia and abroad.
Illustrations supplied by the authors
* Inverter is an electronic device transforming DC current into AC current. - Auth.
** Gyroscopic moment is one of the forces of inertia introduced to take into account an effect of movable system of reference rotation on a relative motion of the body-Auth.
*** Damper is a device taking up vibration energy. - Auth.
* Throttling means pressure reduction and, consequently, expansion of moving gas (liquid) when passing through the narrowing in a pipe or porous barrier. - Auth.
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