2.6. Wind energy application trends
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Electric power supply of remote decentralized consumers. The majority of industrial enterprises, cities, and settlements of the Murmansk region receive their energy from the grid of Kola Energy System. Contrary to these users, a large number of remote consumers in the area –small secluded settlements and villages, weather stations, beacons, border patrol quarters, and sites of the Russian Northern Fleet – are isolated from the grid and receive energy from independent diesel power plants (DPPs). The capacity of a DPP ranges between 8 to 16 kW and 300 to 500 kW. The total number of such installations in the region numbers a few dozen.
Because of their decentralization and significant distance to grid-based energy sources, as well as their relatively low power consumption, plugging remote consumers into the central power supply is economically inexpedient. This is why diesel power stations will remain the only energy suppliers for these consumers in the foreseeable future.
A DPP’s operation involves considerable costs incurred from burning expensive fuel. Diesel fuel prices are high not only because the fuel is of better quality than fuel oil, but also because its transportation is quite costly.
For instance, the coasts of the Barents and White Seas receive their diesel fuel deliveries by sea. Sea-going oil tankers unload fuel to coastal settlements as they cruise along the shoreline. If no berths can be used for unloading operations, the tankers are unloaded at offshore terminals with the help of small-size vessels. Transportation from the coastline to areas located further from the shore is performed by motor vehicles, tractors, sledge trains, and sometimes by air.
Due to the remoteness of these locations and their poor transport arteries, fuel prices increase by 30% to 70% in the coastal areas of the Kola Peninsula and by 150% to 200%, or even higher, in the more inaccessible inland areas.
Under these conditions, the use of wind energy converters can provide a sizable contribution to cutting high diesel fuel expenses. The degree of economizing depends on local wind potential and the diesel power station’s operating load. According to estimations, a wind energy converter operating in an area with favorable wind conditions can replace between 30% and 50% – and in the windiest places, up to 60% or 70% – of the hard-to-obtain fossil fuel. In the long run, introducing WECs will allow for a reduction in the total costs of producing and consuming electric energy.
Wind energy converters’ contribution to heat supply. The implication here is the potential use of WECs for the supply of heating to small towns and villages in windy areas that have centralized power supply, but experience difficulties with fuel deliveries. These are the favorable conditions that may warrant such application of wind energy converters:
1. Heating season in the Kola Peninsula lasts for nine months. That said, wind speeds in the winter are noticeably higher than in the summer. The peak in seasonal heat energy demand thus coincides with the energy output a WEC can provide.
2. After outdoor air temperature, wind is known to be the second classic parameter that determines the scope of heat consumption in a region. Application of WECs will allow transforming wind from a climatic factor contributing to increased heat losses into a full-fledged power source that will provide effective coverage of the population’s needs in heating energy exactly during windy periods.
3. It goes for most energy users that the share of heat consumption in their total energy usage is rather high – sometimes, reaching between 70% and 90%. With that in mind, WEC application will facilitate saving on expensive fuel, which has to be transported to the Kola Peninsula from as far as 1,500 to 2,000 kilometers.
4. Using wind power for heating purposes does not necessitate high quality requirements for the energy produced by a WEC. This allows for a simplification of WEC designs, making the installations cheaper and more reliable at the same time.
5. WEC application for heating purposes also provides the possibility to successfully withstand the main challenge of wind energy: the instability of wind exposure and, by extension, power production. Short-term fluctuations of the WEC’s capacity – those that last for seconds or minutes at a time – are evened out by the accumulating ability of the heating supply system. Prolonged fluctuations, which last over 20 minutes to several hours, can be leveled out by heat reserves accumulated in the buildings that receive the heating. Special accumulating systems or auxiliary heating sources running on fossil fuels can be switched on during longer wind pauses.
Fig. 2.12 demonstrates the correlation between increasing heat losses of a building and the speed of wind. It is clear that heat losses almost double as wind speeds grow. This correspondence, as well as the multi-year data on average daily outdoor temperatures and wind speeds, was used to compile a diagram of seasonal heat consumption variations under the conditions of the Barents Sea coast (Fig. 2.13). As follows from the diagram, wind increases heat consumption dramatically. During the winter months, this increase reaches 30%. At the same time, one notes the synchronicity of seasonal changes in average levels of windiness (that is, average monthly wind speed Vm ) and the changes in heating demand. This also can serve as an important premise for the application of wind as a heat energy source.
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Fig. 2.12. Proportionate correspondence between housing heat losses and wind speeds.
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Fig. 2.13. Seasonal changes in average monthly wind speed (1) and heat consumption, contingent on outdoor air temperatures (2) and wind (3), on the northern coast of the Kola Peninsula.
Heat energy demand of a building or a group of buildings is determined by the following expression:
| Q = q V cw (ty - to) | (2.1) |
where:
q is the specific heat parameter of the building, kW/m3·degrees;
V is the exterior volume of the heated building, m3;
Cw is the coefficient of increasing heat losses caused by wind (Fig. 2.12.);
and ty and to are room and outdoor air temperatures, degrees Celsius.
The volume and heat parameter of the building are constant values, which is why heat consumption depends primarily on the room and outdoor temperatures differential Δt = tr – to and on the allowance for wind counted in the heat loss coefficient Cw.
If heating supply is provided by the boiler house in conjunction with a wind energy converter of commensurable capacity, then a certain part of the heating load schedule will be covered by the WEC, and the rest by the boiler. During especially windy periods, the WEC can cover heating needs to a considerable extent, completely, or even produce excess heat energy. As for periods of cold, but less windy weather, almost all the heating load will depend on the boilers.
All the above can be seen in Fig. 2.14., which represents a fragment of the chronological cycle of a WEC’s potential contribution into the heating load supply. These calculations provide for cases when WEC capacity equals that of the boiler house: BT= Nwec/Nb = 1, where Nwec is the wind energy converter’s capacity and Nb is the capacity of the boiler house. The red black-dotted curve represents variations in heat demand at room temperature tr equaling +200C under windless conditions.
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Fig. 2.14. Fragment of the chronological cycle of a WEC’s potential contribution into the heating load coverage. Wind field of the Kola Scientific Center of the Russian Academy of Sciences at Dalniye Zelentsy,
1 – heating load curve, 2 – net utilized WEC power,
3 – excess WEC-produced energy, 4 – power produced by the boiler house
Taking the impact of wind into consideration, the real heat consumption curve will be higher (the stronger the wind, the higher it is). In the picture, it is represented by lattice line 1. In reality, energy offered by a WEC will rarely coincide exactly with the demand on the part of the energy user. It will happen more often that either the WEC’s energy output, represented in Fig. 2.14.by Position 2, will exceed demand and create excess energy (Position 3), or there will be a lack of energy needed to fully cover demand, and the hatched area of the load diagram (Position 4) will have to be covered by the boiler.
The share бh provided by a WEC in conThe graphic illustration of this dependence is provided in Fig. 2.15. It demonstrates that all other parts of the equation remaining the same, an increase in WEC capacity parameter BT)leads to an increase of бh as well, but this process is soon saturated. It reaches its limit, after which further growth in WEC capacity Nwec is economically inexpedient due to a need for excessive investment funds. Estimations conducted with regard to the wind conditions of the coast of the Barents Sea, have shown that a value within the range of 0.5 to 0.7 of a boiler’s capacity is optimal for the capacity envisioned for a wind energy converter. At the same time, the wind energy converter is capable of taking on the equivalent of 50% to 70% of the output provided by the fossil fuel that the boiler house runs on. sumer heating supply will be expressed as the quotient of the consumed yield of the WEC, integrated into the load curve, to the entire heat consumption volume. Synchronous analyses of data on outdoor temperatures (and, by extension, on heating demand) and on wind (energy offered by the WEC) have shown that the value of бh depends on the capacity of WEC Nwec, wind conditions (average annual wind speed Vy), technical parameters of the WEC (design speed Vd, at which the installation develops its design-based capacity Nwec), and the correlation between the capacity of WEC and that of the boiler (BT= Nwec/Nb).
Analytically, the dependence of бh on these factors is approximated by the following expression:
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The graphic illustration of this dependence is provided in Fig. 2.15. It demonstrates that all other parts of the equation remaining the same, an increase in WEC capacity parameter BT)leads to an increase of бh as well, but this process is soon saturated. It reaches its limit, after which further growth in WEC capacity Nwec is economically inexpedient due to a need for excessive investment funds. Estimations conducted with regard to the wind conditions of the coast of the Barents Sea, have shown that a value within the range of 0.5 to 0.7 of a boiler’s capacity is optimal for the capacity envisioned for a wind energy converter. At the same time, the wind energy converter is capable of taking on the equivalent of 50% to 70% of the output provided by the fossil fuel that the boiler house runs on.
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Fig. 2.15. Dependence of WEC share in the heating load coverage on the correlation of capacities BT= Nwec/Nb
The efficiency of wind energy application for heating needs can be increased by the use of heat accumulating systems which allow for the diligent conservation and timely and effective use of regularly occurring wind energy excesses, instead of discarding them as unnecessary energy. As a result, WEC contribution to heating supply increases in the winter by 5% to 10 %, and by as much as 20% to 25% during the cool northern summer. Heat accumulation makes it possible to avoid frequent use of the boiler houses. This facilitates the simplification of the heating system maintenance and relieves the burden of operation costs.
Large-scale application of WECs as part of the grid. Europe has accumulated considerable experience in using wind farms as part of national power systems. In Denmark, Germany, and Spain, the total capacity of wind parks numbers millions of kilowatts. One should keep in mind that large-scale wind energy development requires the absolute presence in the power system of other capacities that can provide the necessary flexibility: hydraulic, gas-turbine or pumped-storage power plants. The prospects for large-scale system-integrated wind power development in the Murmansk region are as impressive as in the countries mentioned. There are a range of factors facilitating the wide-scale inclusion of wind resources into the electric and heat energy balance of the region. Among these factors are: high wind potential, which makes it possible to expect bigger WEC output than in Germany or Denmark; winter wind power maximum, which coincides with the seasonal peak in power demand; the availability in the Kola Energy System of 17 hydroelectric power plants with a total capacity of 1,600 MW (including over 1,000 MW near the shoreline of the Barents Sea) and reservoirs with multi-year, seasonal and daily regulation, which will allow for accumulation of water reserves with the help of WECs during windy periods, and the use of this water when winds slacken. It is exactly the hydropower plants at the disposal of the Kola Peninsula that can create unique conditions for a wide-scale wind energy application.
Common sense dictates that system-integrated wind power industry is best to be developed first of all in areas with high wind potential, availability of roads for WEC delivery, and potential connection to the grid. It is preferable that such an area is located close to an existing hydropower plant or one under construction. In the Murmansk region, for instance, all these conditions are applicable to the area of the Serebryanka and Teriberka hydropower plant cascades [6, 16]. This is an approximately square area of 40 kilometers wide and just as long, at the top of which one will find the settlements of Teriberka and Dalniye Zelentsy, as well as the Serebryanka-1 Hydroelectric Power Plant and the 81st kilometer of the Murmansk-Tumanny highway (the Teriberka Exit). Estimations show if WECs are placed within a 3% area of this region – and they are installed in an efficient way that takes the local wind rose into account – then their total capacity will reach about 500 MW.
Power produced by the prospective wind parks of the Murmansk region can be transferred through existing transmission lines under a voltage of 150 kV or 330 kV. To prevent transmission overload, energy transmission can be performed under a compensation policy of sorts: Hydropower plant capacity will decrease during prolonged high wind periods. Thanks to such compensation, hydropower plants’ reservoirs can accumulate additional water reserves, transmission lines are not overloaded, and the “wind parks plus hydropower plants” system acquires fundamental operational characteristics. Furthermore, transmission lines receive a steadier load, which improves their economic efficiency.
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