Giant Turbines To Harness Large Wind Potential

50MW wind turbine blades, longer than two football fields, could revolutionize offshore wind energy output.
Published: Tue 09 Feb 2016

Wind energy is one of the world’s fastest growing sources of energy. It now supplies about 2% of global energy needs and that number could rise as high as 10% by 2020.

2014 was a record year for the wind industry as annual installations crossed the 50 GW mark for the first time. More than 51 GW of new wind power capacity was brought on line, a sharp rise in comparison to 2013, when global installations were just over 35.6 GW. In 2014 total investments in the clean energy sector reached a high of USD 310bn (EUR 277bn), according to the Global Wind Energy Council.

The search for the best design to harness this great energy potential is ongoing. We wrote recently about the bladeless turbine [Bladeless Wind Turbines To Cut Energy Costs by 40%] which has been designed to cost less as far as manufacturing, installation and transportation is concerned and noise levels would also be reduced. Now, it is thought that a mammoth size wind turbine blade is the way forward.[DOE Throws Money Behind Larger Wind Turbines.]

A low-cost offshore 50MW turbine with wind turbine blades of more than 200m (650 feet) in length-that’s two and a half times longer than any existing wind turbine blade today-could help the world harness the full potential of offshore wind energy. This is according to Sandia National Laboratories, a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corp., for the US Department of Energy’s National Nuclear Security Administration, which has been given the task of creating these giant blades.

Developing the 50MW turbine blade

According to Todd Griffith, lead blade designer on the project and technical lead for Sandia’s Offshore Wind Energy Program, exascale turbines take advantage of economies of scale.

Sandia has been working on wind turbine designs for a while now — including 13MW systems using 100m blades, which are the basis for Sandia’s Segmented Ultralight Morphing Rotor (SUMR) designs, a new low-cost offshore 50MW wind turbine.  

During extremely fast wind speeds, the blades are stowed and aligned with the wind direction, reducing the risk of damage. At lower wind speeds, the blades spread out more to maximize energy production.

50MW wind turbines are a long way off, but according to Sandia, “studies show that load alignment can dramatically reduce peak stresses and fatigue on the rotor blades.” This would not only reduce blade costs, but eventually lead to the mythical 50MW wind turbines.

The benefits of a larger wind turbine blade

Developments like these are critical to the offshore wind industry.

While countries could have large offshore wind energy potential, offshore installations can be costly. Larger turbines will help to capture more energy at a more affordable price.  

Conventional upwind blades are expensive to manufacture, deploy and maintain beyond 10-15MW. They have to be rigid to avoid fatigue and eliminate the risk of tower strikes in strong gusts of wind. The stiff blades are heavy, and their mass, which is directly related to cost, becomes even more problematic at the extreme scale due to gravity loads and other changes, explains Mr Griffith.

Sandia’s segmented designs will save money when it comes to production, transportation and installation because the long blades are manufactured in segments. The blades are positioned downwind, and the segmented sections bend in the wind while retaining segment stiffness.

“At dangerous wind speeds, the blades are stowed and aligned with the wind direction, reducing the risk of damage,” explains Mr Griffith. “At lower wind speeds, the blades spread out more to maximize energy production.”

Larger turbines also reduce carbon footprint  

A 2012 Swiss study, The Bigger the Turbine, The Greener the Electricity points out that larger turbine blades can actually reduce our carbon footprint. The study shows that for every doubling of the size of the turbine, global warming potential per kWh (is) reduced by 14%. The study was conducted by Marloes Caduff and associates at the Zurich Institute of Environmental Engineering in Zurich, Switzerland.

The researchers claim that there are two main reasons for the benefits of larger turbines. Firstly, producers now have the knowledge to create massive blades with great efficiency.

Secondly, materials today allow the manufacturing of large turbines without a corresponding increase in mass. Blades can therefore be bigger and capture more wind while the tower and other parts remain unchanged.

According to the researchers, the combined effects of these reasons allow for bigger and better turbines to be produced without using significantly more materials or drastically increasing transportation and assembly costs.

In fact, the increased size of the turbines actually saves materials by reducing the number of total turbines needed to produce the same amount of power.

Not all down to size  

Currently, wind turbine manufacturer, Vestas has developed an off shore model called the V164-7.0MW which can generate 7MW of energy with its massive 80m blade length.

The capacity for turbines like the V164-7.0MW has only developed recently and it seems certain that bigger and more powerful wind producers will be possible in the future, especially since scientists and engineers have the knowledge and ability to combine sophisticated controls and advanced technologies with massive turbines.

Further Reading

Environmental Science and Technology- Wind Power Electricity: The Bigger the Turbine, The Greener the Electricity?