Five most frequently asked questions and answers about wind turbines 

Last fall, after a ten-year break, the construction of a modern wind farm began again in Estonia. What has changed in wind turbine technology in ten years? How much electricity does one wind turbine produce? Andrus Zavadskis, Technical Manager of Utilitas Wind, answers these and other frequently asked questions about wind turbines. 

1. What has changed in wind turbine technology in ten years? 

Over the past ten years, wind turbine technology has advanced remarkably. Today’s wind turbines are bigger and more powerful and, because of that, they are also more efficient electricity producers. The bigger the wind turbine is, the fewer wind turbines we need to get the same amount of electricity. For example, the capacity of one turbine in the Paldiski wind farm, built ten years ago, is 2.5 MW. However, the turbines in the Saarde wind farm, which began construction in November, will have a capacity of 4.3 MW each. Thus, the nine wind turbines of the Saarde wind farm produce more electricity per year than the 18 wind turbines of the Paldiski wind farm. The Utilitas’ wind farms that are currently under development were designed with turbines that have over 6 MW of capacity.

In addition to the development of technology, society’s understanding of the need for renewable energy has also changed. Clean and environmentally friendly energy contributes to cheaper electricity prices and is also important for energy security and independence. Wind turbines are the fastest production equipment to install, in terms of renewable energy, and they provide energy throughout the year.

2. Why are wind turbines white in color? 

There are mainly three reasons why wind turbines are white: neutral appearance, safety, and technical durability. 

When seen from the ground, white is the most neutral color, i.e. the least striking, and it also reflects all other colors and light. But seen from the air, the white color helps wind turbines be more noticeable. This is important both for flight safety and for the safe movement of birds. In order to be visible at night, wind turbines are equipped with lights for flight safety. 

In addition, the white color helps to extend the life of wind turbines, because it reflects sunlight. Materials heat up due to solar radiation, and higher temperatures reduce the life of the equipment inside the wind turbines. Also, ultraviolet radiation damages materials over time, so it is beneficial to have most of the UV radiation reflected back from the surface of the wind turbine. 

3. How much electricity does one wind turbine produce? 

How much electricity a single wind turbine produces depends on its size, capacity, and location. Depending on the technology and wind conditions, the capacity factor of modern wind turbines is around 40% to 50%. In better locations with higher wind speeds (for example, offshore or on a windy coast), the capacity factor reaches over 50%. The capacity factor equates to the productivity of the wind turbine. If the wind turbine was able to operate at full capacity all year round, this would mean a 100% capacity factor. In reality, however, the wind does not constantly blow at full speed, which is why wind turbines have a lower capacity factor in reality. The capacity factor is calculated by dividing the annual actual production by the annual theoretical maximum production. 

For example, the total capacity of the Saarde wind farm, which will begin to operate in Pärnu this summer, is 39 MW, and the estimated annual production is about 135 GWh, which makes it the most productive wind farm in Estonia. The energy produced at the Saarde wind farm covers the annual electricity needs of all homes in Pärnu County, i.e. more than 40,000 households. 

Offshore wind turbines produce a certain amount of electricity almost continuously because they produce electricity at a wind speed of 3 m/s and at a height of a few hundred meters above sea level. Thus, one offshore wind turbine covers the annual electricity needs of nearly 20,000 households. Offshore wind turbines are three to four times more powerful than land-based wind turbines. An offshore wind farm with 80 wind turbines produces roughly 60% of Estonia’s annual electricity needs. 

4. What happens if there is no wind? 

Depending on the wind conditions, wind turbines produce energy with variable capacity but, luckily, they do not produce energy in isolation. Estonia has external connections for capacity that is bigger than Estonia’s electricity consumption at the coldest time of the year. The region of the Nordic and Baltic countries is large enough that there is never a complete lack of wind in the entire region at the same time. If it happens that a large number of wind turbines are down, for example in the summer, then solar and hydro plants still produce renewable electricity in the region. In addition, there are already storage and fast-starting reserve power plants in the region, and more will be built in the coming years. 

We have modeled the volumes of wind electricity production according to wind conditions since 2006 and found that by adding two offshore wind farms, new onshore wind farms and solar farms, and storage capacities in Estonia, we would be able to cover 95% of Estonia’s annual electricity needs with such a portfolio and to export it at certain times. In order to cover the remaining 5%, it is reasonable to have on-site reserve production capacities in addition to connections. Today, the solution is the existing oil shale boilers but, in the future, biomethane-based or cross-sector coupling solutions can be used (to produce hydrogen and heat from green electricity, charge cars, etc.). The need for reserves is in no way only related to renewable energy solutions – keeping certain capacities in reserve is always necessary for any combination of energy production capacities. 

5. Why do we need wind electricity? 

The more electricity we produced from renewable energy, the less we need to use gas and oil shale. Abandoning fossil fuels is necessary to slow down climate change and maintain a livable climate. As electricity consumption increases, for example, due to the growth of electric transport, methods must be found to produce electricity without fossil energy sources. 

In Estonia, the best way to produce clean electricity is wind turbines, because we live in a sparsely populated windy region and the wind blows just when we need electricity the most, i.e. in the autumn and winter. Also, the price of producing electricity from wind or solar power is cheaper since there is no need to buy fuel to produce the electricity. This is also important in conjunction with stock market logic: the more renewable energy there is on the market at a cheaper price, the lower the price of electricity will be for everyone.