Hot summer: A disadvantage to wind energy

As the global economy continues to expand, there's a growing demand for an increased reliance on renewable sources. However, hot summers make popular renewables such as wind energy less efficient, which is a huge disadvantage.

In 2023, approximately 116.8 GW of new wind power capacity was connected to power grids globally, marking a 50.5% increase compared to 2022 (Figure 1). The leading markets were China, India, and the U.S.

When considering climate change, our attention often centers on shifts in temperature rather than potential changes in near-surface wind speed. However, this factor is crucial for a power system dependent on wind energy, determining the efficiency of the wind turbines.

Figure 1: Source

Related: Germany reaches a record high in the installation of renewable energy

Hot temperature causes energy loss

According to Berkeley Earth's analysis, the estimated global mean temperature in 2023 was 1.54 ± 0.06 °C above the average temperature from 1850-1900, commonly used as a pre-industrial baseline (Figure 2). That is an increase of approximately 12.4% compared to the previous record high observed in 2016.

Figure 2: Source

Since 1850, the ten warmest years have all occurred within the last decade. The global mean surface temperatures (land and sea) diverged 0.77°C to 1.18°C from the 20th-century average between 2014 and 2023.

The NOAA recently declared that the Earth’s average land and ocean surface temperature in 2023 was 1.18°C higher than the 20th-century average of 13.9°C. That made the year the warmest on record since 1850.

The trend of increasing temperatures is expected to persist, with NOAA indicating a 99% probability that 2024 will rank among the five warmest years on record.

The alarming consequence is that the increased global temperatures and the build-up of dust can affect the efficiency of wind turbines and lead to higher maintenance demands, energy losses, and operational expenses. This is a huge disadvantage for wind energy.

A team studied the combined effects of adverse conditions on the performance of each 2-MW turbine in the 10-MW Shagaya wind farm in Kuwait. Their two years of analysis revealed that dust build-up on ventilation systems and equipment inside the nacelle triggers reduced efficiency of turbine power during high temperatures.

The high temperature between 40–44 °C was also a primary contributor to energy losses of about 1.2% annually.

Related: Maximizing energy efficiency with solar-powered windmills

High temperatures are a disadvantage for wind energy

Renewable energies are capable of generating sufficient power for the countries that adopt them as fossil fuel alternatives. However, during hot summer, many countries experience warm and windless months, leading to inconsistent electricity production from wind farms.

Scientists from the University of Reading in the UK and National Grid analyzed wind data between 1980 and 2018. They revealed that the amount of wind power made in 2018 was less than the average of 21% made over the last 38 summers.

Similarly, in 2021, the UK-based power company SSE reported that its renewable assets generated 32% less power than anticipated due to low speed and dry conditions between April and September.

The condition is more worrying as the latest IPCC reported a reduction of 0.063 m/s in global mean land wind speed (excluding Australia) every decade between 1979 and 2018. The report also projected a decrease in average wind speeds across Europe by 8%-10% due to climate change.

Is windier the better?

Selecting a windier place is very important. A site complimenting an annual average wind speed of 7 meters per second (m/s) or higher is believed to be highly suitable for wind turbine installation.

However, even locations with wind speeds as modest as 5.5 m/s can prove feasible with larger wind turbines. Except for the natural dependency on weather and wind speed, two main things generalize the efficiency of turbines:

• Hub Height: A wind turbine’s hub height refers to the distance from the ground to the center of its rotor. Since 1998–1999, the hub height of wind turbines has increased by 73%, reaching approximately 98 meters (m) by 2022. In the U.S., the average hub height for offshore wind turbines is expected to reach 150 m by 2035. The latter is equivalent to the height of the Washington Monument. These taller turbine towers are to harness more wind energy, capitalizing on the fact that wind speeds typically increase with altitude.

• Rotor Diameter: The rotor diameter of turbines, representing the width of the circle covered by the rotating blades, has also undergone significant growth over time. By 2022, the average diameter had surpassed 130 m—exceeding the length of a football field. Larger rotor diameters enable turbines to cover more area, capture increased wind, and generate greater electricity output, even in regions with relatively lower wind speeds.

Figure 3 shows how much power a wind turbine can generate with a certain hub height and rotor diameter. For example, to generate 6 MW, a turbine needs a hub height of 100 m and a diameter of 150 m.

Figure 3: Source

Operational challenges of the bigger turbines

While the trend follows toward larger turbines, there are some limitations. One challenge lies in the transportation and installation as they lack flexibility once constructed.

Figure 4: Source

Cost is another of the biggest hurdle. Rising commodity prices have disrupted the trend of declining costs. Despite a decade of consistent cost reductions, the production of wind turbines and grid power is becoming more expensive.

Although wind turbine prices have fallen steadily from USD 1,800 per kW in 2008 to USD 770-850 per kW in 2021, GlobalData indicates that the average per-MW cost has risen by 37.2% between 2020 and 2022 (Figure 4). Turbines represent approximately half of the total cost of a wind project.

Additionally, rising costs of labor, land leases, and components are affecting every sector. Figure 5 suggests that the nacelle (generator, gearbox, and brakes) is the most expensive part of a wind turbine, followed by blades and rotor at 20%.

Figure 5: Source

Related: Energy security concerns lead to more coal production

Wind power is one of the key renewable solutions to our energy needs. However, the recent wind drought serves as a strong reminder of its variability and the necessity for diverse investments to ensure reliable energy in future.

Integrating wind power with other renewable sources like solar and hydropower will be crucial to consolidate the disadvantage of hot summer for wind energy when wind generation is low.

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