Wind turbines are one of the most versatile methods of generating renewable green energy. However since the start of their use, there always has been doubts about the amount of usable energy a windmill can produce. This scepticism increases especially on the windless days when the efficiency of the windmill is extremely low. However, recent advances have made it possible to modify existing windmills to deliver more power.
A windmill consists of a tall tower affixed with fan blades at the top to harness wind energy by converting it into useful work. With the help of a mechanical arrangement, this power is then converted into electrical energy. However, the size and capacity of a windmill varies in accordance with its application.
Increasing Windmill Efficiency
Wind turbines can become a more popular source of energy development in the future only if it competes with other contemporary sources of energy such as coal, natural gas, and nuclear power. Moreover, it should also be equal or better than other sources of renewable energy such as solar energy (see Concentrating Solar Power Technologies) and bio gas. Also, the process of production should be as cost effective as possible.
It is very important that the power produced by a windmill have a greater standard of quality. The design of the blades and the turbine play an important role in a windmill’s performance. The design should satisfy the load requirements and generate energy at the lowest cost. This can be done by optimizing the performance characteristics of the windmill. Power output versus wind speed or power output verses rotor angular velocity are two important characteristics that are taken into consideration during optimization. Enhancing this improves the overall quality of the power produced.
One more aspect by which a windmill’s performance can be improved is by giving importance to the wind’s kinetic energy that the windmill utilizes. The wind turbines’ potential can be improved by optimizing three main parameters – cut-in, rated, and furling wind speeds. By doing this, usable energy can be maximized even from the lowest wind speeds. This would not only provide substantial increase in efficiency but also reduce the wastage of energy.
Energy output from the windmill often fluctuates due to the variation in wind speed. In order to smooth this power fluctuation batteries/capacitors should be provided to store electricity on days with good windspeed. This energy is used on windless days to prevent blackouts and smooth the power supply.
Another way of increasing wind mill power is by exploiting the inertia of the wind turbine rotor. Recent advances have allowed putting a braking control mechanism that adjusts the rotor speed so that the incoming wind power is greater than the average power. This arrangement increases the rotor speed so that it can store excess energy as kinetic energy without utilizing it in generating electricity. This stored energy is used when there is a drop in the wind power generated. The method also captures more wind energy and also improves the overall efficiency.
Windmill efficiency can also be improved by increasing the tip speed ratio. The tip speed ratio of a windmill depends on the design of the blades. Optimum blade shape depends on the type, size, and brand of the windmill. The different types of blade shapes are:
- Flat blades
- Wing shape, with one edge rounded and other tapered
- Both the edges of the blade are tapered
- Both the edges are rounded
Efficiency can also be increased by surface coating the blades with protective elements.