Wind energy is on track to overtake hydropower in electrical generation this year in the U.S. This is good news, though it may have done so sooner if costs allowed. That’s not to say wind is cost-prohibitive. In fact, the opposite is true.
Wind-generated energy has become one of the most economical sources of renewable energy in the country. The cost of wind has fallen by nearly 70% since 2009, dropping 7% in 2018 alone, according to investment firm Lazard. And in most of the U.S., it is cheaper to build a new solar or wind farm than to keep an existing coal plant running.
Nevertheless, the construction of conventional foundations, towers, blades, and turbine components do sport a price tag — one that can easily be beaten by certain unconventional wind generators, such as kites and flags.
According to an early energy-kite developer, Makani (which means “wind” in Hawaiian), wind energy has the potential to power the world 100 times over, yet only a small percentage of the world’s electricity comes from wind. There are a number of reasons for this but permitting, materials, construction, and transportation costs certainly factor in. (Makini was founded in 2006, acquired by Google in 2013, and this year made into a subsidiary of Alphabet, a multi-national conglomerate headquartered in California.)
To make wind power more accessible, Makani developed a giant energy kite that uses a wing tethered to a ground station to harness utility-scale wind-generating electricity. Its kite flies autonomously in loops, as the wind moves through it, generating electricity that is sent down a tether to an electric grid.
This “turbine” without a tower and blades is substantially less costly to transport, build, and maintain. It may also benefit from higher altitude wind and greater aerodynamics to optimize wind generation.
Researchers at the University of Carlos III in Madrid (known as UC3M) have been working on the accuracy of kite power — or what they call, Airborne Wind Energy Systems or AWES. Like kite energy, AWES consist of airborne airfoils tethered to ground-mounted generating stations. The low cost and portability mean it is possible to transport and install these systems quickly and easily.
“AWES are disruptive technologies that operate at high altitudes and generate electrical energy,” said Gonzalo Sánchez Arriaga, Ramón y Cajal research fellow at the Department of Bioengineering and Aerospace Engineering at the UC3M, in a press statement. “They combine well-known disciplines from electrical engineering and aeronautics, such as the design of electric machines, aeroelasticity, and control, with novel and non-conventional disciplines related to drones and tether dynamics.”
UC3M has developed a flight simulator for AWES, which can optimize system design and performance at a given location. This software is free to download and accessible to other research groups. In addition, the UC3M team created a flight testbed for AWES, composed of two kites with data-recording features (to track the system’s speed and position, for example). The experimental data has validated different software tools and key system parameters of the AWES.
On a smaller scale, at least in relation to generating power, researchers at the University of Manchester recently developed flags that can harvest electrical energy using wind and solar power. The flags use flexible piezoelectric strips, which let the flag generate power through movement from wind, and photovoltaic cells for solar power.
So far, the flags are capable of powering remote sensors and small-scale portable electronics, which according to the scientists, can be used for environmental sensing such as to monitor pollution, sound levels, or heat.
The aim of the study, according to the Manchester team is: “To allow cheap and sustainable energy harvesting solutions, which can be deployed and left to generate energy with little or no need for maintenance. The strategy is known as ‘deploy-and-forget’ and this is the anticipated for model that so-called smart cities will adopt when using remote sensors.”
Dr Andrea Cioncolini, co-author of the study, added: “Wind and solar energies typically have intermittencies that tend to compensate each other. The sun does not usually shine during stormy conditions, whereas calm days with little wind are usually associated with shiny sun. This makes wind and solar energies particularly well suited for simultaneous harvesting, with a view at compensating their intermittency.”
The research has been published in the journal Applied Energy. Although it’s unlikely such unconventional turbine designs will take over the typical tower and blade wind-power landscape, the greater the available options to harness the wind, the better.