General overview

Windmills have attracted mankind since ancient times. They were used to grind corn, to process wood, to pump water, etc. and after the oil crisis in ‘70s they returned as an interesting power source for electricity and as a favored way of reducing pollution caused by burning fossil fuels.

As any invention which at its time represented a difficult-to-understand and hard-to-accept step forward, it was greeted with suspicion. The evolution registered during the past 30 years has demonstrated that using wind to produce green energy has already become an industry with a significant impact upon the energetic systems and the plans for sustainable development.

Given the fact that wind power is an environmentally friendly and renewable energy source, developed countries in Northern and Western Europe, as well as USA and Australia have shown increased interest in it during the past decades. More factors have simultaneously contributed to the development of this field, such as: geographical position, scientific research and a strong political will for the implementation of cheap and environmentally-friendly energy sources. The goal set forth by The European Wind Energy Association for 2020 is to reach a level of 20% out of the total European energy production. Denmark is currently the only country close to this level.

This field became attractive to Romania in 2004, when one has passed the law allowing certain private companies to produce and supply electricity to be then introduced in the national network. There still are impediments mainly caused by too little publicity on the specific legislation; lack of a professional and accurate national map of wind atlas; lack of or underdeveloped infrastructure in certain high-potential areas; the current state of the national roads which do not allow or impede overweight transportation in the case of modern, high-capacity wind-turbines; insufficient financing sources as well as lack of financial support from the state.  

However, despite all these impediments, Romania is a market which shows interest in wind power. This interest is boosted by its geographical position and is demonstrated by the current production share (not enough covered) as well as by certain trans-national companies which are willing to implement some major projects in high-potential areas. 

Two factors play a major role in choosing the location: the complexity of the location and the extreme weather conditions. One should mention the fact that most turbines have an optimal efficiency in the range of 3-25 m/s wind speed, with a maximum output reached at 10-16 m/s. When the values fall out of this range the turbine stops automatically in order to avoid possible damage.

The operation principle of a wind turbine for industrial production is pretty simple: the wind force which powers the rotor of the turbine sets it into motion, while triggering a generator through a controller. The models differ from one manufacturer to another, whereas currently there are two major ways of powering the generator: the classical way (by means of a 2-shaft system with different speeds and a controller) and the direct way in which the rotor directly connects to an electric generator with a higher number of poles. The classical type is the most common one at present.

Likewise, there are two main possibilities to control the rotation speed of the rotor: the “stall control” using the aerodynamic shape of the blades or the “pitch control” turning around the blades entirely at almost 90 degrees. One also uses the “active stall” control, as an intermediate variant, yet on a narrower scale since it requires very large systems.

The opinions regarding the efficiency of each system in turn vary. In the first case, the construction is simpler and thus more reliable, whereas in the second case more complex and larger systems are needed. However, in view of the present technological progress it is hard to tell which system is the best one, although the tendency is to use the “pitch” control more. When choosing a turbine,   the criteria that prevail refer to efficiency, reliability and costs.

The dimensions of the turbines have also evolved, from outputs of 50 kw/h and 15 m rotor diameter in 1980 to 5000 kw/h and 124 m rotor diameter in 2003. In trials currently exist turbines which have a power output over 6 MW.

Maintenance costs are relatively low as compared to the initial investment and in time one shall develop turbines which require even less maintenance work. Generally speaking, two annual check-up and maintenance inspections are needed, and gearbox oil and cooling agent change is needed every 2-3 years, depending on the location and the manufacturer’s specifications. The average operating life of a wind turbine is around 20  years if prompt and correct maintenance is provided.

All wind turbines have their own wind measurement devices. Based on the recorded wind parameters, the computer performs the necessary adjustments for an optimal operation without the presence of a permanent human operator. As a rule, all turbines, organized as wind farms or not, contain remote control and inspection systems, thus providing for an easier management of the production units.
As any other motion equipment, it implies wear and maintenance costs. Looking at things this way, the investors should consider all aspects involved, given the extent of the investment and the relatively long pay-off period.

Despite the fact that Romania’s wind resources are considerably high; SEN (The National Energetic System) raises many technical problems that hinder the development of this field. In order to solve these problems one needs to carry out certain large-scale energetic research activities as well as to invest in updating and developing the SEN. A considerably large number of wind turbines, evenly installed all over the country, as well as the use of other alternative energy sources,  will ensure Romania’s independence from imports of expensive and polluting fuels and will offer a guarantee for a cleaner and healthier environment.