Renewable Energy sources-Why Wind Turbines are best bet

History of Wind Turbines

Renewable energy sources first harnessing. Historians believe the first use of wind power was as early as 5000B.C when sailors on the Nile River depended on the power of wind for propulsion.

At about 1000 AD the Persians were the first to harness wind energy to pump water and also use the wind resource to boost their food production, they used the wind to grind their grains.

In Europe, the harnessing of wind energy was realized in about 1300 AD. The Dutch people are famously known to have used wind energy to help them out in reclaiming flooded land to use for agriculture and human settlement.

The United States became the first country in the early 1980s to generate electricity from a wind turbine. The turbine was rated 1 megawatt.

During about the same period, California became the first state in the United States to develop a wind farm leveraging Federal government incentives. The wind farm generated 1000 megawatts enough electricity to power about 200,000 homes in California.  

Turbine Efficiency growth 

Wind turbine efficiency has tremendously improved from the 1980s to the present day compared to other renewable energy sources. This efficiency can be directly attributed to the increase in the size of the turbines, improvement in research and development of turbine parts and systems, and improvements in manufacturing. Turbine parts can now be manufactured at record time to meet demand and supply requirements in the wind power industry.

Advancement in material science has enabled the creation of stronger materials like fibreglass and resin which are used in the manufacturing of the turbine’s blades and the nacelle. Turbines are exposed to the vagaries of weather and therefore have to be very durable to withstand this degradation for about 25-30 years of operations.

Major Turbine Types

There are two major types of Turbines, vertical wind turbines, and horizontal wind turbines.

Vertical wind turbines can also be referred to as vertical axis turbines and have blades that are attached to the top and the bottom of a vertical rotor. A common example of a vertical axis wind turbine is the Darrieus wind turbine panted by the French engineer Georges Darrieus in 1931.

Horizontal axis wind turbine is the majority in the world. They have 3 blades installed which rotate in the presence of wind like an aircraft propeller

Turbines can be classified as small-scale turbines or large-scale turbines A typical large-scale wind turbine is one that has a Rotor diameter ranging from 50m to 100 m. It produces power between 1 and 3MW. When compared to large-scale wind turbines, small-scale wind turbines are those which have their rotor diameter ranging from 3m to10m and have a power capacity of 1.4–20 kW.

Turbine  parts:

Blades enable the rotation of the turbine generator when exposed to wind flow. They are three in number

Hub-This component holds the three blades in position and allows the twisting of the blades-pitch to maximize the speed of the turbine with regards to the optimum production of electricity.

Nacelle-This is the space where the generator is housed and other electrical components

Tower-The tower holds the three blades at the right position where the wind pressures are adequate enough to generate electricity. At such positions turbulence that might impact the optimum generation of electricity is averted. Towers are usually made up of steel.

Turbine Operation 

For a turbine to operate, it must be facing the direction of wind flow. How does a turbine orient itself to the wind direction? The turbine rotates the nacelle and the hub in the direction of the wind. The action to rotate in the right direction is due to the wind vane mounted at the top of the nacelle. The wind vane determines the direction and speed of the wind. This information is fed to the computer system onboard the nacelle. The computer instructs the nacelle to yaw towards the direction determined by the wind vane.  

While in the right direction the blades are able to twist according to the wind speed to generate two types of forces-A lift force acting perpendicular to the direction of the wind speed; and drag, acting towards the wind direction. A combination of these forces causes the blade to spin. The hub is connected to the gearbox through the drive shaft. The gearbox multiplies the rotation of the blades by about 100 times which translates to 1500 revolutions per minute. The kinetic energy from the wind is now converted to electric energy by the generator in the nacelle.

The electricity produced then travels from the nacelle to the base of the tower to the adjacent step-up transformer. This transformer steps up the electricity to a higher voltage which is then transmitted to the substation. The substation further steps up the voltage to the specified value required for transmission to the national grid which is responsible for distribution to the final user.

Renewable energy sources,Wind turbine unit Cost reduction due to high efficiency 

Turbine efficiency has been improving over the years since the first wind Turbine began operations in 1979 in the USA.

In terms of the unit price reductions due to this efficiency, the price of wind power has tremendously reduced from 40cents/KWh to less than 5cents/kWh in 2022.

This efficiency can be attributed to the following technological advancement in wind power generation by turbines:

Optimization of the blade aerodynamic properties with the blade adopting a curved shape as opposed to the earlier flat shape. The curved shape operates on the sample principle as an aeroplane wing which facilitates high-speed airflow above the wing and low-speed airflow below the wings. The difference in pressures causes the turbine to rotate. Normally the blade’s revolutions per minute (RPM) are between 12-20 depending on the wind speed and power rating of the turbine.

SCADA system Controls

With the increase in computing power, computers have been integrated as part of the turbine control and operations systems.

As part of the turbine’s intelligent system, the turbine can be able to autonomously track the wind direction and be able to orient itself-yaw, to that direction of the prevailing wind.

To maximize the rotation of the blades also known as pitching, the blades can twist along their horizontal axis from 0-90 degrees through the complex computer systems installed on the turbine. 

The control team can also manipulate the operations of the turbine from the substation and from anywhere on the globe through a complex SCADA system.

Conclusions

Improvements realized in manufacturing and material science have enabled the production of durable materials like steel, aluminium, fibreglass, and resin metal alloys which form the supply chain of turbines. This has facilitated mushrooming of wind farms all over the world with China taking the lead in the number of total installed turbines followed by America.

In terms of Turbine efficiency, there is an upper limit calculated by German physicist Albert Betz. Betz established that no matter how first the wind is blowing the maximum kinetic energy that can be converted to electrical energy is 59.3% of the wind’s energy.

Wind power has the lowest power cost rating of less than about 5cent dollars per Kilowatt hour. A single commercial size turbine rated 1.5-2 megawatts can power up to 500 homes.

Climate change activists have suggested the transition from fossil fuels to renewable energy sources to avert a global warming catastrophe.