Are Wind Farms Causing Fires Like the Tragic One in Maui Last Year?

The University of Sidney’s Sydney Institute of Agriculture (School of Life and Environmental Sciences) recently made a very interesting submission to an Australian Senate Committee on the subject of wind farms and their effects on drying out land and enabling fires. The report is titled “Understanding Wake Effects from Offshore and Onshore Windfarms: A Need for Research on Downwind Meteorology and Rainfall, Rates of Evapotranspiration and Drying on Land and the Risk of More Intensive Wildfires,” and may be found in full here.

Provided below is my condensation of the submission (emphasis added):

Abstract

Despite almost complete ignorance of their meteorological effects, engineered wind turbine plants have been enthusiastically adopted worldwide as a source of renewable energy. But is this source of electrical power renewable if it slows the laminar windflow, inducing turbulence and chaotically affecting wake meteorology?

Published evidence of aerial or satellite measurements shows that while extracting wind energy, turbines create turbulent wakes, slowing airflow at hub height and releasing heat, two effects potentially raising wake pressure and inducing convection. Warmer, turbulent air increases rates of evapotranspiration and therefore increases landscape dryness, depending on predominant wind direction.

Field and laboratory studies show that such dryness of soil and vegetation will increase the risk of more intense local wildfires…

Introduction

Windbreaks have been long known to provide shelter from impacts of winds. A well sheltered zone behind a break with low permeability to air flow is typically warmer and more humid, with the ascending turbulent wake zone cooler and dryer than an unaffected control flow. Figure 1 illustrates such wakes caused by an offshore windfarm, the meteorological conditions favouring precipitation releasing latent heat proportional to the rate of condensation of water in a saturated atmosphere.

Figure 1

Evidence for Turbulent Properties of Windfarm Wakes

While onshore windfarms do not significantly affect global wind speeds or patterns (Li et al. 2023), there is published evidence that windfarms do affect local wind speeds tens of kilometres downwind, requiring them to be well separated. Moreover, they generate their own characteristic turbulence independent of any turbulence existing in their wind inflow, as shown in wind tunnel experiments…

Miller and Keith (2018) showed for stable night conditions a significant warming effect at 28 operational US wind farms using MODIS satellite detection. They also concluded that this warming could exceed warming avoided by reduced carbon emissions…

Wang et al. (2023) showed in China that windfarms dried surface soil significantly, both temporarily and spatially. Bodini et al. (2023) using measurements of airflows made on aircraft that turbulence from wind turbine plants reduced axial air speed as much as 30% downwind at hub height to at least 30 km. The turbulent eddies in air flow, delaying axial wind speed, naturally increase the probability of evaporation by greater exposure of soil and vegetation…

Novel research on wind turbines (Kennedy et al. 2023) using least action modelling,; Kennedy and Hodzic (2023) have proposed that air in laminar flow in anticyclones releases vortical latent energy as heat when made turbulent by surface friction. This explains our interest in the effect of turbulence of drying the landscape.

Using this novel least action method to successfully estimate maximum power from wind turbines, we predicted (Kennedy et al. 2023, Table 5) that a 70 turbine 105 MW windfarm might cause turbulent heating of wake air up to 3 °C, if all heat released was contained in a stream about 100 m high and a kilometre wide.

Using the Penman-Monteith equation we estimated the enhancement in evapotranspiration to be 5% at 25 °C ambient temperature. With slower turbulent winds, a 10% increase in drying could occur, sustained if wind direction and laminar flow strength is maintained.

While this prediction is hypothetical, it can be tested under field conditions. While wind droughts with speeds insufficient to generate power from wind farms occur, depending on direction, the wake drying effect of such turbulence is cumulative, with the water evaporated transported elsewhere…

Curing of grass is a function of the proportion of dead material in the grass, contributing significantly to fire spread.  In summer, grass curing may be close to 100 percent elevating flammability. Grasses, commonly found adjacent to wind turbines, are most susceptible to constant dry wind where dead fuels can dry out quickly. Once the dead fuel moisture drops below about 20% of the oven dry weight there is both a greater probability of ignition and fires can also spread very rapidly, even under light winds. To the extent that windfarm wakes increase … the drying of vegetation for many kilometres, they will intensify general effects of high temperatures and drought in warm areas…

The Tragic 2023 Maui, Hawai Wildfire

About 20 percent of Maui's electrical power is derived from windpower and more is planned. A devastating wildfire occurred in August 2023. The August 8th-9th wildfires in Hawaii resulted in the United States' deadliest wildfire recorded. The coastal and upcountry fires caused widespread destruction and loss of life, predominantly in the coastal town of Lahaina. The Lahaina fire was speculated to have been from downed power lines, which sparked and ignited dried vegetation in areas experiencing moderate (01) to severe (02) drought conditions, according to NOAA…

The distance involved for drying of vegetation and human structures to Lahaina is 13 kilometres. Our hypothesis of warming and enhanced evapotranspiration from turbulent airflow well prior to the fires could increase the flammability of the landscape by a significant factor. Fire intensity is highly responsive to dryness, given that the major cooling effect of evaporation is limited, allowing unimpeded combustion.

Although local wind roses are sometimes dominated by local topology, the predominant turbulent airflow clearly disposes the landscape leading up from the windfarm directly to Laihana. No other townsite in Maui is at so much risk from a tinder-dry situation. The theory that the fire was initiated by sparks from strong winds bringing down a power line recorded as a flash is consistent with this hypothesis…

Conclusion

The chaotic meteorological effects of windfarms from wake turbulence is significant. More intense wildfires in North America reported in recent years, are often in regions with installed wind turbine plants. 

#Australia #Climate #Wind #Wakes #Fires #Maui

Hat Tip. R.C.