Advancements in wave energy technology (WEC) have been slow, mainly because of the harsh marine environments WECs must operate in, as well as the complex regulatory requirements. Tiffany Plate at NREL explains itâs why the U.S. Department of Energy and NREL have collaborated on the Small WEC Analysis tool, publicly available online. Its purpose is to provide baseline information about the performance of different types of WECs in various ocean settings. The tool can compare four common WEC models: attenuators, oscillating surge WECs, single-body point absorbers, and two-body point absorbers. Wave environments vary hugely, so every location will have its own optimal solution. The ability to model and predict energy capture should help accelerate design cycles or avoid a faulty concept from the start.
Surfers know the power of a single wave. So does a ship in the midst of a storm. And thanks to a new tool developed by National Renewable Energy Laboratory (NREL) researchers, so does anyone designing a wave energy converter aimed at harnessing that power.
Wave energy converters, or WECs, come in many shapes and sizes and create different amounts of energy in different types of waves. That means a WEC that performs well in the big waves of Californiaâs Humboldt Bay will not necessarily be efficient at capturing the energy of the low and slow swells in North Carolinaâs Outer Banks.
âWave energy is not like traditional energy sources where you put in this much fuel, and you know, you get this much power,â said Jim McNally, a technology innovation, modelling, and assessment engineer at NREL. âThere are so many variables that you need to account for in order to get a real estimate.â
Filling the information gap
To account for these variables, researchers from the U.S. Department of Energyâs Water Power Technologies Office and NREL collaborated on the recently developed Small WEC Analysis tool, an online, publicly available graphical user interface. The goal of the site is to provide baseline information about the performance of different types of WECs in various ocean settings.
The tool was designed to make it easy for users to compare four common WEC models:
- Attenuatorsâmulti-segment devices that float parallel to ocean waves and rise and fall, creating a flexing motion that drives turbine rotation or a hydraulic pump
- Oscillating surge WECsâdevices that have a vertical flap affixed to the seabed, which generates energy from the back-and-forth motion of waves
- Single-body point absorbersâsimple buoys connected to the seabed that create energy from the up-and-down motion of waves
- Two-body point absorbersâbuoys attached to a âheaveâ plate on the seabed that resists the motion of the buoy, which in turn creates energy.
âThere are many different types of WECs,â said McNally, who led the development of the tool. âBut these concepts represent the most popular mechanisms that inventors ideate when designing their own.â
The need for this information came into sharp focus when competitors in the American-Made Waves to Water Prize began modelling their concepts for wave-powered desalination devicesâand researchers from NREL and other national laboratories were asked to judge their feasibility.
âThere wasn’t any really good information on the performance of smaller wave energy devices out there,â said Scott Jenne, a marine energy systems engineer at NREL who initiated the Small WEC Analysis Tool project and served as principal investigator for the Waves to Water Prize. âYou can’t really do a techno-economic feasibility assessment unless you know something about the device performance. To me, this tool was a critical first step.â
That means the tool is also helpful for researchers and funders looking for a baseline measurement that indicates the amount of energy a particular WEC is expected to produce.
Say a decision-maker from the U.S. Department of Energy or the Testing Expertise and Access for Marine Energy Research program receives a request to fund or test a new WEC from a university or entrepreneur. âWith WECs, there are a number of ways to estimate the amount of power theyâll produce, but oftentimes, these estimates arenât entirely accurate,â McNally said. âThe decision-makers needed an interface where they could quickly look up an estimate and be able to see if a proposal is in the ballpark.â That information helps those decision-makers evaluate whether the innovation is worthy of funding or lab testing space.
A groundbreaking interface
For the first time, the Small WEC Analysis tool enables users to compare different WECsâ performance on an apples-to-apples basis. âYou used to have to dig through different documentation on different types of WECs at different locations,â McNally said. âHere you can really see how a machine will work in certain environments.â
How does the tool work?
Letâs say a developer is interested in installing a group of attenuator WECs off the coast of Maine. They will first need to identify the average wave height and length at their locale using a resource such as NRELâs Marine Energy Atlas or the National Oceanic and Atmospheric Administration’s National Data Buoy Center. Then they will review how much energy an attenuator can produce in that sea state. Not enough energy to meet their needs? Maybe they would get more energy out of a different size attenuatorâor compare it to another kind of WEC, such as a point absorber, which may better suit their purposes and location.
Having this information in a publicly available interface, along with historical data, is vital for anyone in the wave energy world, which includes startups, universities, and researchers. âSomeone may look at the data and say, âWeâre going to need a bigger boat,ââ McNally said. The energy estimates found within the tool can either help accelerate an inventorâs design cycle or prevent them from wasting time on a faulty concept from the start. This information just helps close the design loop, McNally added.
The future of Small-Scale Wave Energy
Because of the harsh marine environments WECs must operate inâand the complex regulatory requirements imposed on device deploymentsâadvancements in wave energy technology have been slow.
But the U.S. Department of Energy Water Power Technologies Officeâs Powering the Blue Economy initiative seeks to change that. Projects in the initiative are accelerating WEC technology to fulfil small-scale needs. For example, wave-powered desalination devices being invented through the Waves to Water Prize are helping to provide drinking water in disaster relief scenarios or to remote coastal communities. And the Ocean Observing Prize inspired competitors to utilise WEC technology to develop devices that could greatly expand ocean and hurricane monitoring capabilities, which could, one day, eliminate the need for diesel to be shipped to research buoys or boats.
Although they may not be huge, small-scale WECs could help meet the needs of small communities and projects, and the data found in the Small WEC Analysis Tool will help identify the best WECs for the job.
Want to dive deeper into the toolâs functionality? Watch the R&D Deep Dive: Small WEC Analysis in the Palm of Your Hand webinar recording to learn more, then explore NRELâs marine energy research and related tools.
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Tiffany Plate writes for NREL
This article is published with permission from the National Renewable Energy Laboratory