Wind power has been part of the story of two different storms.

Critics of renewable energy blamed South Australia’s high penetration of wind power for a state-wide blackout in the wake of a spate of tornados. Partisan bickering about the feasibility of wind power started immediately and continues.

On the other hand, Hurricane Harvey slammed into a part of Texas with several wind farms. One continued to operate normally throughout the storm. The rest were back online within days. No one blamed wind energy for making the crisis worse.

What can we learn from the contrast?

The South Australian tornados

South Australia gets almost 40% of its electricity from wind energy.

On September 28, 2016, South Australia suffered seven tornados.

They destroyed three transmission lines and more than twenty towers.

South Australia had thirteen operating wind farms at the time. Nine, representing 445 MW of generation, stopped working.

Subsequently, the interconnector between South Australia and the rest of the country shut down to protect the national grid.  Within minutes, the entire state blacked out. Not until October 11 was electric service fully restored.

The Australian Energy Market Operator (AEMO) regulates gas and electricity. It investigated and issued its final report in March 2017.

When voltage dips too low, turbines can’t operate correctly. They have “low-voltage ride through” settings to compensate. Normally, low-voltage events occur infrequently. But other settings protect the turbines by shutting them down if too many events occur in a short time.

It appears that some of the wind farms simply left the factory default settings in place. And AEMO admitted that it knew nothing about this safety feature.

Ten wind farms suffered between three and six ride-through events within two minutes. All the turbines at five farms, set to allow a maximum of ten in that time, continued to operate.

Most or all turbines at nine other farms, however, shut down. Three were set to allow five events, and experienced six. Five were set to allow only two. The AEMO report doesn’t specify a pre-set limit for the ninth.

Therefore, all the wind farms operated correctly for their settings. AEMO had authorized the turbines, but never noticed their built-in protections. So no one determined appropriate settings.

In the face of this incompetence, the South Australia blackout provides no evidence against the feasibility of wind power.

Hurricane Harvey

Texas has the most wind energy capacity of any state, about 21 gigawatts, about a quarter of installed capacity in the entire US.

Most windfarms are in western Texas and therefore safe from the storm.

But the south power zone has 3.6 gigawatts capacity, including 2.1 gigawatts directly on the coast.

Wind turbines typically shut down if wind speed reaches 55 miles per hour. When wind turbines encounter excessive wind, the blades disconnect from the rest of the mechanism. They can safely pinwheel without damaging anything. The poles will pitch and yaw in the wind.

Some analysts feared that the coastal wind farms would fail. They predicted that it would take several days for the wind to die down enough for them to restart.

Harvey made landfall on August 28, 2017 as a Category 4 hurricane. Coastal wind farms, along with all of Texas’ fossil fuel infrastructure, shut down and evacuated before the storm hit.

It inflicted major damage on the oil and gas industries. Gas prices spiked nationwide. Refineries and petrochemical plants released toxic pollutants into the air and water. Fossil fuel operations won’t quickly return to normal. The environmental impacts will therefore last longer than the high gas prices.

Landfall occurred about 20 miles from the Papalote Creek Wind Farm outside Corpus Christi. Wind speeds measured more than 130 miles per hour when it struck. Even so, they registered only 90 miles per hour (Category 1 strength) at the wind farm.

At least one windfarm operated continuously during the storm. All but one of the ones that shut down got back online by August 31. Papalote Creek could not resume operations until local power lines were fixed on September 1.

No one has questioned the feasibility of wind power after Harvey.

Implications for the future feasibility of wind power

Regulatory incompetence contributed heavily to the South Australian blackout.

It was not a factor in Texas. It appears, though, that siting of the coastal wind farms kept Harvey from wreaking havoc on the wind farms.

Hurricanes rapidly lose power the further inland they get. It also helped that closest wind farms were on Harvey’s west side. Hurricanes usually cause the most damage on the east side of the storm

According to Justin Sharp of the American Meteorological Socitey’s renewable energy committee, turbines won’t start to fail until winds reach 140 miles per hour.

At that speed, the wind will shear off the blades and cause them to crash into nearby towers. He estimates the chance that a wind farm directly on the Texas coast will face wind speeds that high at 15%.

No one has yet calculated the probability of offshore wind farms encountering a direct hit from a major hurricane. But Harvey has proved that current technology works well for conditions likely to occur at onshore wind farms.

So far, the US has offshore wind farms only off Rhode Island. The North Sea has extensive wind farm development, but it doesn’t suffer tropical storms.

A major hurricane would destroy offshore windfarms with current technology in storm-prone areas of American coasts. Offshore wind farms will therefore remain vulnerable until some new design can withstand such strong winds.

Critics take aim at the feasibility of wind power and other renewable energy only when something doesn’t work. It appears that, in the US, anyway, hurricanes won’t give them anything to complain about. At least, not until someplace depends on offshore turbines with today’s technology.

Sources:
Gas prices spike but Texas wind farms — and grid — hold steady after Harvey / Tina Casey, Triple Pundit. September 5, 2017
Harvey set to overpower wind in state generating the most / Brian Eckhouse, Chris Martin, and Ryan Collins; Bloomberg News, August 25, 2017
In big test of wind farm durability, Texas facility quickly restarts after Harvey / Russell Gold, Wall Street Journal. September 1, 2017
Texas Wind Turbines Survive Hurricane Harvey / Reve: wind energy and electric vehicle review. August 30, 2017
Wind energy’s viability: lessons from an Australia blackout / David Guion, this blog. July 27, 2017

Photo credits:
Wattle Point wind farm. Public domain from Wikimedia Commons
Downed transmission tower. Source unknown
East Somerton wind farm. © Copyright Stephen Craven and licensed for reuse under this Creative Commons Licence
Sheringham Shoal wind farm. Public domain from Wikimedia Commons