Armed with Science: The Navy’s Indoor Ocean

As many teams mentioned during the Wave Energy Prize Team Summit in April 2016, the Finalists are incredibly excited to test their 1/20th-scale WEC prototypes at the nation’s premier wave-making facility, the Naval Surface Warfare Center’s Maneuvering and Seakeeping (MASK) Basin, at Carderock, Md. With testing beginning in less than two weeks, let’s take a closer look at this unique facility, which was featured in the official U.S. Department of Defense science blog, Armed with Science, last year. More »

Wave Energy Prize Program Update: A Look Back at Our First Year, a Look Ahead at Achieving Our Goals

By Alison LaBonte, Ph.D.

Program Manager, Marine and Hydrokinetic Technologies, Wind and Water Technologies Office, U.S. Department of Energy

June 2016 image.png

In 2012, the U.S. Department of Energy (DOE) realized that revolutionary advancements in wave energy were needed for it to play a significant role in our clean energy portfolio, making wave energy a great candidate for a public prize competition. The Wave Energy Prize is not your average research and development program: compressed timelines spark rapid innovation, resulting in revolutionary technology development.

Before we opened registration for the Wave Energy Prize, our team set an aggressive goal to double the state-of-the-art energy captured per unit structural cost of wave energy converters (WECs). With this goal came a number of program objectives, which are to:

  • mobilize new and existing talent,
  • conduct a rigorous comparison between device types,
  • advance the understanding of pathways to achieve long-term levelized cost of energy goals, and
  • attract investors and create a strong foundation for future funding opportunities

So far, we’re achieving these ambitious objectives. A year ago, 92 teams registered for the Prize, three times more than we expected. Of these, 66 turned in technical submissions, which were evaluated by our panel of expert judges to identify 20 Qualified Teams. Most teams that registered were not previously known to DOE. Seventeen of the 20 Qualified Teams’ completed the initial small scale testing phase, and only two of the nine teams selected for the final phase of testing have received any funding from DOE in the past.

In April, I updated the MHK community gathered at Waterpower Week in Washington, D.C., on the progress of the Prize during a panel discussion on innovation. So far, most of the teams have met the aggressive timelines for the Prize, which puts DOE in a great position to achieve the remaining objectives. To meet the requirements for Technology Gate 2, the Qualified Teams built 1/50th-scale model devices, tested them at university facilities around the country, and conducted significant numerical modeling studies in just four months.

The nine Finalist and two Alternate Teams have put forward diverse WEC designs, which include two submerged areal absorbers; four point absorbers; two attenuators; and three terminators. And in these designs, we’re already seeing technical innovations in the areas of geometry, materials, power conversion and controls. Some of these include:

  • adaptive sea state-to-sea state control,
  • wave-to-wave control,
  • power absorption in multiple degrees of freedom,
  • optimized float shapes and dimensions for energy absorption for broad bandwidth of wave frequencies,
  • survival strategies such as submerging beneath the surface for extreme storms,
  • use of structures and materials that are cost effective to manufacture, and
  • flexible membranes that react to the wave pressure over a broad area.

Waterpower Week attendees saw some of these innovations firsthand when they met the Finalists and Alternate Teams during the Wave Energy Prize Showcase in which the 1/50th-scale models were on display.

Industry stakeholders are taking notice, and the public’s awareness of wave energy is increasing because of the teams’ efforts in the Prize. In just over a year, more than 100 news stories have featured the Prize, including in outlets like Popular Science, The Weather Channel and National Geographic. The Prize’s website has hosted more than 23,000 visitors, and its social media channels have logged more than a half million impressions. This increased awareness of the potential contribution of wave energy to the nation’s renewable energy mix will exist long after the Prize ends, and will likely set the stage for future private-sector investments and government funding opportunities.

It’s an exciting time to be in the wave energy community. The teams are putting the finishing touches on their 1/20th-scale prototypes, which will be rigorously tested at the U.S. Navy’s MASK Basin from August through early October. Follow our teams’ progress at waveenergyprize.org, and save the date for November 16, when winner(s), if any, will be announced!

Why is the development of wave energy converters so challenging? Part 2: Extracting energy from waves

Development of wave energy converters

So, how exactly can we exploit this resource?

The Wave Energy Prize received technical submissions detailing 66 unique WEC concepts.

A very small number of these couldn’t work, but the overwhelming majority were concepts that could exploit, to differing degrees, the fluid motions of water particle motions. While some of these concepts were variations on ideas seen before, that is still a very large number of different ideas. At present, the means of exploiting wave power seems only constrained by the imagination of the inventors.

And that is a challenge; one that the Wave Energy Prize is, in part, endeavoring to address.

If one thinks of the development of modern wind turbines 30 to 40 years ago, there was also a plethora of competing wind turbine designs, each hoping to become commercially competitive.

Over time, as the science, engineering and economic understanding has matured, it became possible to identify optimum approaches to the exploitation of the, essentially, linear wind flow into electricity. All turbines now are generally three-blade, horizontal-axis turbines, with a gear box and generator. More modern designs are now using permanent magnet generators, and maybe even novel hydraulic systems. Even then, the principal power absorption mechanism was essentially the same for all wind turbines – linear fluid flow into horizontal mechanical rotation (we do, however, see some small vertical axis turbines in niche applications).

At present, the means of exploiting wave power seems only constrained by the imagination of the inventors.

The same is true of tidal stream turbines, and also aircraft and car designs. Over time, the science and engineering, along with the design tools and test facilities available, lead to a science-backed consensus regarding optimum configurations. Optimum configurations might change as new materials and components become available, but changes are systematically made through an understanding of their impact on a turbine’s techno-economic performance, arising from good knowledge, understanding and information (this can also relate to cars or planes.)

The exploitation of low-speed fluid oscillations created by ocean waves, imparting very high linear or rotational forces/torques, which need to be converted to (generally) high-speed linear or rotational motion in a generator (doing so cheaply and reliably, while being survivable) is just not as well understood within the science community.

Hence the very large number of wave energy conversion concepts we see in the Wave Energy Prize, and throughout the world.

It is possible that there is no single solution that is optimal, or that there are several optimal solutions, dependent on many factors, such as site conditions, water depth, distance to shore, etc.

The exploitation of wave power faces other very significant challenges, perhaps ones that aren’t faced by wind turbines or tidal stream turbines – the most important of these is survival.

Potential wave power sites off the West Coast of the United States have annual average wave energy fluxes in the region of 20-30 kWm-1 of wave crest length. In severe winter storms, the peak power can be multiple times higher than this, perhaps as high as 1MWm-1 (an increase by a factor of 30-50 over the average wave energy flux). This provides significant challenges to the structural design and consequent capital cost, or requires survival strategies, such as diving, submersion, or perhaps even removal to shore. And these typical winter storms are not as strong as the survival conditions to be met for the “100 year wave” or rogue waves, which will be even more demanding.

Wind turbines operate in a relatively narrow range of wind speeds, and simple survival strategies are possible when winds exceed operational limits; they feather their blades to minimize the forces on the turbine. Furthermore, the forces imparted by water with a density of ~1000kgm-3 are so much larger than when the fluid is air. Tidal stream turbines are also frequently not exposed to the severe storm conditions or wave energy potentially encountered by WECs. Besides, the environmental conditions seen are far more predictable and the ranges are not so extreme.

Interestingly, deep-water waves are also intrinsically more survivable than near-shore ones, as near-shore devices could well be exposed to severe breaking waves in harsh storm conditions, which would likely lead to catastrophic failure. In severe storms, big ships head away from the shore and out to deep water for the same reason.

The exploitation of wave power also creates other challenges that are not normally as onerous for wind turbines and tidal stream turbines. These include:

  • This is straightforward for onshore and relatively straightforward for shallow-water offshore wind turbines. Tidal stream is more challenging, due to the high-speed water currents in commercial sites, but still relatively close to shore, and not at very significant water depths. For WECs in deep water, this requires multiple mooring systems, potentially remotely operated vehicles and divers, possibly operating many miles from the shore base for marine operations.
  • This requires access in potentially hostile and dangerous environments, with weather window constraints.
  • Some WEC concepts are intrinsically directional in their approach to exploiting wave power, whereas wind turbines and potentially tidal stream turbines have easy strategies for orienting the system towards optimum flow conditions for energy extraction.
  • Marine debris and biofouling. With many wave energy concepts located at the surface of the sea where the wave energy is greatest, they are potentially more vulnerable to damage caused by marine debris, such as shipping containers, ropes and fishing nets. Biofouling is also far more prevalent at the surface or near the surface, as this is where the biological activity is greatest.
  • Other uses of the sea. WECs potentially have greater impacts on other users of the sea, such as those in shipping, fishing and recreation. Many wave energy concepts have some freedom to move, but tidal or wind turbines are essentially static devices that are constrained by moorings. This uses up a large surface of the sea, and increases the potential for collisions.
  • Non-linearity. Wave energy theory is linear, which is an approximation that holds only for small waves. In practice, the waves themselves and the interaction of the device with them is likely to be non-linear, potentially requiring very significant computer power to even understand how the device might react to the waves, or accepting uncertainty in performance and maybe life-time of the device.
  • Breaking waves. This is not really a great concern for deep-water WECs, with the possible exception of rogue waves or in survival conditions. However, breaking waves impart huge slamming forces on structures and their moorings, leading to potentially catastrophic failure.

All in all, a very difficult environment to design for and survive in.

Whatever the solution is that emerges from the Wave Energy Prize and other U.S.-based and global development activities, to be successful we need to see large increases in the absorbed power, with high bandwidth and adaptability to different sea states, and maybe even wave-to-wave control, with greatly reduced capital expenditure, reliability, survivability, and maintainability.

The Wave Energy Prize Purse and Seed Funding

Wave Energy Prize Cash Purse

Why participate in the Wave Energy Prize? Teams will be competing for more than $2 million in prizes and seed funding.

The prize purses available to the winner(s) of the Wave Energy Prize will be:

  • Grand Prize Winner: Team ranked the highest after testing of the 1/20th scale WEC device model at the Carderock MASK Basin – $1,500,000
  • 2nd Place Finisher: Team ranked second after testing of the 1/20th scale WEC device model at the Carderock MASK Basin – $500,000
  • 3rd Place Finisher: Team ranked third after testing of the 1/20ht scale WEC device model at the Carderock MASK Basin – $250,000

To be eligible to win a monetary prize purse, a team’s 1/20th scale device must achieve a threshold of 3m/$M Average Climate Capture Width per Characteristic Capital Expenditure. The judging panel will rank all teams whose devices achieve the threshold and assess their overall performance using the Hydrodynamic Performance Quality (HPQ), outlined in Section 6 of the Wave Energy Prize Rules.

The Wave Energy Prize will also provide seed funding to the Finalists (up to $125,000) and Alternates (up to $25,000) determined at the end of Technology Gate 2. This seed funding will be provided to the Finalists and Alternates for costs associated with the building of the 1/20th scale model to be tested at the MASK Basin, as well as costs associated with the shipment of the 1/20th scale model and participation in the testing process.

Four Teams Already Registered for Wave Energy Prize

Wave Energy Prize - Registered Teams as of May 4, 2015

Four teams—from Alabama, California, Colorado and Texas—are already registered for the Wave Energy Prize! Read each team’s profile and proposed wave energy converter (WEC) device type, and learn more how U.S. teams and their partners can innovate and compete for more than $2 million in cash prizes: http://waveenergyprize.org/teams