Welcome to July’s edition of the Technology Buzz! This month, we’ll peruse recent developments that turn windows into smart windows. And seeing as it’s beach season and time for building sand castles, we’ll delve into the perils facing off-shore wind installations and what researchers are learning about them.
Self-Powered Smart Glass for Smarter Windows
Existing smart windows can electronically vary their tint to reduce lighting as well as heating and cooling costs. Retrofitting this technology into an existing building is expensive and labor intensive because additional wiring must be installed. But what if a power supply came already built in to a smart window? You could just remove the old one and swap in the new one without worrying about additional wiring. It would save time, reduce labor, and most of all, save money.
—Or what if there was a peel-n-stick film a consumer could apply to their existing window glass from inside their home and then control it with your phone?
Princeton University researchers have developed a smart window that selectively absorbs near-UV wavelength light to supply the power. By only using solar cells that work at this wavelength, the cells can be transparent. The cells were made using organic semiconductors using a similar method that organic light-emitting diode (OLDED) manufactures. By using near-UV wavelength light instead of infrared, the window is able to generate more electricity without the problem of heat building up. Tinting is controlled by electrochromic polymers which turn the windows from transparent to dark blue, capable of blocking out 80% on incoming light.
The research team has all ready started a new company, called Andluca Technologies. A flexible film version for a peel-n-stick application is one of their ultimate goals. Sound way too sci-fi? Actually, this kind of window film technology has been around for a while. The difference is that prices remain high and some smart window films require an external power supply.
Worse Things Happen at Sea
It’s oft said the sea is a cruel mistress. And when it comes to building anything out in her great blue depths, there’s reason for apprehension.
When Block Island, the first off-shore wind farm in US waters, officially switched on May 1, 2017, it was no stranger to storms at sea. Earlier in March, it faced wind speeds between 55 mph and 70 mph that forced it to feather its blades and wait out the storm. While Block Island sailed through the rough weather shipshape and Bristol-fashion, the farm’s location a few miles off Rhode Island means it’s not likely to have the severe conditions of other proposed wind farms in the Gulf of Mexico or along the Carolinas. Namely, Category 5 hurricanes.
New University of Colorado Boulder-led research asserts that current engineering of utility-scale offshore wind turbines are unlikely to withstand hurricane-force winds. For example, in 2014, the National Renewable Energy Laboratory (NREL) led research groups to develop a baseline design for a hurricane-resilient wind turbine designed to withstand a maximum wind speed of 52 meters/second.
In their study, UC researchers relied on high-resolution computer simulations to see the wind flow of a Category 5 hurricane where wind speeds are in excess of 157 mph or 70 meters/second. While current hurricane wind estimations put wind speeds near the storm’s eyewall at 55 meters/second, simulations showed they could reach 99 meters/second or 221 mph. Simulations also showed the change in wind direction across a wind turbine could be as much as 55 degrees between the tip of a blade and its hub, subjecting the blade to bending and twisting.
Researchers hope their findings could be used to help wind farm developers improve design standards.
But it’s not only high speed wind that might stalk off-shore wind farms. There’s also the waves themselves. And the most sudden, unpredictable, and devastating is the rogue wave. Rogue or freak waves are not entirely understood but some contributing factors include swells that reinforce and build each other and shortened wave frequency where the period between waves shrinks allowing waves to join and focus their energies together, making them steeper and taller.
Rogue waves have been known to reach 60 feet or more —even on days with little or no wind. Storm-driven giants aren’t that rare, but how often they occur isn’t understood, either. The first scientifically measured rogue wave struck a Norwegian oil platform on New Year’s Day 1995. It was measured by a laser-based rangefinder to be 85 feet tall from trough to peak. While rogue waves are “not expected in the Gulf of Mexico”, Hurricane Ivan generated a nearly 91 foot tall wave that was 600 feet long in the Gulf in 2004. More recently in April, 2014, a suspected rogue wave struck the oil rig ENSCO 8506 about 130 miles from Galveston, TX. The wave was big enough to knock the platform 55 feet off its position and damage one of three watertight chambers in one of the unit’s six ballast columns. Thankfully, no one was injured and the rig was not drilling at the time.
To better understand the formation of rogue waves and possibly begin getting a handle on how to predict their likelihood, an international team of researchers gathered at the University of Turin in Italy where they used a special circular tank (or flume) to study and break down the statistics of wind-generated waves that create rogue waves. Starting with still water, a group of fans blew across the surface for two hours, generating an erratic wave field across the surface. Wave height was measured throughout the experiment. Measurements showed that as waves grew, rogue waves developed naturally. Researchers found that the probability for the occurrence of steep, high waves was higher than expected. While previous theories put them occurring once every thirteen hours, researchers found conditions where they would occur as often as once every hour.
While off-shore wind turbines are able to feather their blades and wait out a wind storm, there’s very little they can do to hold up against a 100 foot tall wall of water. If the turbine is operating normally, there’s just not much to do when a 100 foot tall ocean wave suddenly emerges out of the briny blue and heads straight for it. Research into how off-shore wind turbines might survive rogue waves is still only just beginning.