Sun is playing a significant part in the formation of winds, as suns thermal energy, through convection, heats earth’ surfaces. The differences in surface temperatures are causing the emergence of wind. Hence, as long as there is the sun, there will be wind.
The first-ever wind turbine, to generate electricity, was installed in 1888, in Cleveland, Ohio, and was designed to run at a peak capacity of 12 kilowatts (kWp). This marked the beginning of electricity generation from winds. Windmills and turbines take advantage of the kinetic energy that comes along with moving air, which is then convicted to electricity via the rotors and generators. Before going into greater detail of how efficient this process is, we need to distinguish between two significant terms: (i) wind turbine efficiency and (ii) wind capacity factor.
Wind turbine efficiency is the amount of kinetic energy converted into electricity. In contrast, wind capacity factor is the average power produced, in relation to what it could generate if always running at full capacity. E.g. a three-megawatt wind turbine produces an average power of one and a half megawatts; then its capacity factor is 50% (1.5/3 = 0.5, i.e. 50%). This factor though varies from place to place, and even from year to year.
Due to laws of physics, theoretical wind efficiency is limited to 59.6%, which is the maximum capability to which kinetic energy can be trapped inside wind turbines. Due to further limits caused by the way generators and turbines are engineered, an average of 35-45% of the winds “moving energy” is trapped, at present.
Nonetheless, let’s have a look at how efficient that is compared to other utility energy sources. Coals energy efficiency only lies around 29-37%, underperforming winds energy efficiency. Gas is competing for heads on with between 32-50% of its total energy being transformed into electricity. The top performer is nuclear power, with a capacity factor of 92.5%. Even other renewable energy sources, such as hydropower, claim higher capacity factors than wind plants, yet solar photovoltaic lags a bit behind with only ~26%.
Another factor that needs to be considered is the intermittency of winds resulting in uneven generation of power. Therefore, the grid has to balance energy supply obtained from wind turbines continually. With technological advancement and new projects for building additional wind farms, this intermittency is more comfortable to handle.
So, what is it that makes wind farms and energy generated from wind attractive? Two factors, costs & it’s carbon-free production. In 2017, the average costs to produce an MWh were highly dependent on the specific country’s regulations and natural circumstances. For onshore windfarms Mexico and Canada showed record-breaking bids of EUR 14.20 and EUR 23.00 respectively, touching ground within worldwide market prices. Germany in comparison had their lowest onshore bid at EUR 38.00, and an average of EUR 47.30, while neighbour France awarded bids averaging at EUR 65.00, dropping 21% from the year before. In Germany, offshore bids, auctioned at cost, at EUR 46.60 per MWh are genuinely higher than onshore bids. This is due to lower levelized costs of electricity (LCOE) for onshore windfarms, as of significantly lower EPC- and O&M-costs.
With evolving technology and the expansion of total capacity of wind farms, especially offshore, overheads are set to decline further. With only 20% of the total expenditures being operational, the other 80% are capital outlays caused by the installation itself, wind turbines are set to be competitive, over the course of their lifetime.
Speaking of progress in the wind energy sector, turbine towers and their rotors are starting to reach impressive heights and diameters. Standing at 260m tall, a rotor of 220m and blades of 107m tall, wind turbines unleash a maximum capacity of 12 MWp. This record-breaking turbine generates a total of 67 GWh gross p.a., which can power 16,000 households. Generally, wind energy contributes up to 5.5% of the global electricity demand.
What other aspects would YOU like us to look at more deeply for the next time when it comes to wind electricity?