Wednesday, June 29, 2016

Wind Farms and Advancements in Turbine Technology

By Sage Ertman, Policy Intern

Based on recent data collected by NCSL, legislatures in 29 states have adopted Renewable Portfolio Standards (regulation mandating increased production of energy from renewable sources); and another eight states have at least set goals (instead of mandates). The growing recognition of climate change and its devastating effects on our planet has spawned a global movement to combat it. The technologies that have allowed us to harvest energy from renewable sources continue to expand and develop as more people see the value of investing in a sustainable future. Huge leaps have been made across the board in finding increasingly efficient means to harvest this energy at even greater capacities. Wind energy technology, for example, is starting to see some major upgrades.

Wind energy is the fastest-growing source of electricity in the world. The entire globe’s installed capacity for wind power was 35,467 megawatts (MW) in 2013, while the United States alone achieved a capacity of almost 75 gigawatts (GW), or 75,000 MW, by the end of 2015. As costs go down and efficiency increases (and also hopefully because people realize how important it is for our environment and our future), investment in renewable energy will continue to climb. In fact, Deepwater Wind recently broke ground on the US’s first offshore wind project near Block Island, off the coast of Rhode Island. The project is expected to create 300 construction jobs, and when complete, it will boast five turbines that will produce 30 MW of power. Though this is a relatively small project, the Block Island Wind Farm will not only provide electricity to all the homes and businesses on the island, but will also generate additional power that can be fed back to the mainland grid via an undersea transmission line. The hope is that this project will spark some momentum to take advantage of offshore wind development. A 2010 study by the National Renewable Energy Laboratory (NREL) estimated that the total potential for offshore wind development within 50 miles of shore is more than 4,150 GW, while the total potential for onshore wind development was estimated to be 11,000 GW. To put that into perspective, the total installed wind capacity across the entire US as of 2015 was only about 74 GW.

Taking a look across the pond, DONG Energy is planning the world’s largest offshore wind project in the North Sea off the east coast of the United Kingdom. For this project, to be commissioned in 2020, DONG plans to install 170 turbines for a total capacity of 1.2 GW. That is nearly twice the size of the next largest offshore wind farm and will provide enough electricity to power over one million homes in the UK. There is also potential to expand the project and install up to 3 GW of capacity.

The offshore turbines used in the DONG project will be mounted to the seabed. These types of turbines require relatively shallow depths to develop; however, that means depth constraints allow us to access only a very small portion of our offshore wind capacity. Floating wind turbines, on the other hand, have the advantage of not being restricted by depth requirements, allowing greater access to valuable and more consistent offshore wind resources. They also allow the turbines to sit much farther offshore which minimizes visual pollution of the coastal skyline. For these reasons, Statoil, a leading Norwegian energy company, has plans to install the world’s first floating wind farm 15 miles off the Scottish coast later this year. Five wind turbines will be built, each with a 6 MW capacity, for a total capacity of 30 MW. The turbines will be stabilized by large steel tubes filled with ballast, which will be tethered, rather than affixed, to the seabed by long cables. Though the power produced by the project will be nominal, the excitement comes from taking steps to blaze a path for others to follow.

In addition to advancements in offshore wind farming, we have seen some major leaps in rotor blade technology as well. In 2015, the Fukushima Offshore Wind Consortium unveiled the world’s largest offshore floating wind turbine 12 miles off the coast of Fukushima. Though it is also larger than any fixed offshore wind turbine. Part of the Fukushima FORWARD project, this 7 MW turbine is one of three turbines destined for this location. A 2 MW turbine was installed in 2013, and a final 5 MW turbine is scheduled to be installed this summer. The largest turbine has 80-meter blades with a total rotor diameter of 164 meters (nearly the length of two football fields). While larger turbines allow for more energy production, the additional size and weight make reliability a real concern.  That is why a new project emerging from Denmark, spearheaded by LM Wind Power and Adwen, has the wind community anxiously waiting. The two companies have teamed up to produce the world’s largest rotor blade (video here), measuring 88.4 meters. The blade is specially designed for new 8 MW turbines that Adwen hopes to have in production by 2018.

However, Adwen’s accomplishment will likely soon be overshadowed by a project underway in the US. With funding from the US Department of Energy, researchers from Sandia National Laboratories are working to develop a revolutionary new wind turbine that will put the Fukushima and Denmark turbines to shame. For the new design, each blade will stretch a whopping 200 meters (this time longer than two football fields). That is roughly 2.5 times as long as the blades used in either the Fukushima or Denmark projects described above. This means the diameter of the rotor span, including the hub, will exceed 400 meters (roughly 4.5 football fields). Standing next to such a behemoth would certainly be awe-inspiring. This massive turbine is projected to yield a capacity of 50 MW, utterly blowing away the competition (pun intended). But that isn’t all they have planned.
Sandia Lab's new blade design

In a Sandia Labs News Release, Todd Griffith, the project’s lead blade designer and technical lead for Sandia’s Offshore Wind Energy Program, recently touched on some design problems the team had to overcome: “Conventional upwind blades are expensive to manufacture, deploy and maintain beyond 10-15 MW. They must be stiff, to avoid fatigue and eliminate the risk of tower strikes in strong gusts. Those 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.” The Sandia team solved this problem by using segmented blades, so that “at dangerous wind speeds, the blades are stowed and aligned with the wind direction, reducing the risk of damage.” This new design uses downwind blades, as opposed to traditional upwind blades, “bio-inspired” by the way palm trees move in storms. The offshore turbines must be able to withstand hurricane winds at speeds over 200mph. Though the project is still only in its design phase, this incredible innovation provides a glimpse into just one project seeking to blaze a path for others to follow.

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