Wave+Energy+Collectors

toc

Wave Energy Converters (WEC) are a group of clean energy generating devices that harvest energy from ocean waves.[1] While finding alternatives to fossil fuels has been a topic of interest in recent years, the concept of a WEC is not a recent idea. Patents for WEC devices were created as early as 1799, and by 1973, there were already 340 patents for WEC devices. [2] As time goes on, the need for a reliable and efficient WEC increases. It is estimated that, at most, there are 750 [|Terawatt hours] of harvestable wave energy lost on the shorelines around the world.[3] On top of this, wave power is available throughout the entire day. WEC’s are able to collect energy about 90% of the time whereas solar and wind energy converters are only able to collect energy about 30% of the time they are operational.[4] That being said, there are already several wind and solar power plants around the world but no large scale WEC plants have made a debut. Before that an happen, several improvements on current WEC technology need to be made in order to improve efficiency, cost, and impact. In order to make these improvements, extensive testing and modeling must be done on several different designs of WEC’s in order to perfect how humans harvest electrical energy from the ocean. [5] = Current Implementations =

Wave Dragon
The Wave Dragon, originally deployed in 2003, is one of the first WEC to undergo research and testing. The Wave Dragon uses [|convergent hulls] (see fig 1) to direct waves to the main body. The waves will bounce off of the convergent hulls and be directed into a collection tank inside the Wave Dragon. Once enough water is held inside the collection tank, it is slowly emptied and the water goes back into the ocean. By utilizing the potential energy stored in the tank of water, the Wave Dragon is able to utilize [|low pressure head turbines] to generate electrical energy. This form of WEC is referred to as an overtopping. [6] Although the Wave Dragon is still just a prototype, the design is still one of the most efficient [7] of all WEC’s. The current implementation of the Wave Dragon is just a 1:4.5 scale model, and is only used for testing purposes. When scaled up properly, the Wave Dragon will be able to produce anywhere in between four and ten megawatts of power [8], and can be deployed in arrays with several other over-topping WEC’s in place. This would allow a substantial amount of power to be generated, and would be comparable to power plants using fossil fuels to generate power. Furthermore, the Wave Dragon can be placed anywhere in waters 25 to 40 meters deep[9]. When compared to most WEC’s that need to be placed on shorelines, this is both an advantage and a disadvantage. With little need for specific environmental conditions, overtopping WEC’s can be implemented in many areas of the world to produce electricity.

Azura
The Azura was initially launched for testing off of the coast of Oregon in 2012[10]. A similar prototype was later built of the coast of Hawaii in order to be connected to the power grid. Currently, it is the only WEC connected to the power grid in North America, and is serviced by the Northwestern Energy Innovations company. The Azura lives in a 30 meter deep test site generating about 20 kilowatts of power.[11] The tests supply scientists and engineers alike with valuable information regarding the use of this WEC. Using this information, the Department of Energy wants to create a full scale model of the Azura. It will operate in 60 meter deep water and produce about one megawatt of power for the grid. [12] Both the proposed upgrade and current prototype fall into a group of WEC’s called floating point absorbers, characterized by their ability to float on the ocean surface. Most floating point WEC’s have two portions: one portion floating on the top of the ocean and a second portion that is stationary(See fig 2). As the waves carry the floating portion around, a generator will be actuated and generate electrical energy. [13] The benefit to using this type of WEC is the size. Compared to the extremely large and heavy Wave Dragon, the Azura is much more compact. So while the Wave Dragon will produce more power per unit, the Azura can pack more units in a given space. However, due to the continuous back and forth motion of the Azura, it will need more servicing.[14]

= Environmental Impact =

Considering and understanding the environmental impact of WEC’s is a limiting factor regarding moving WEC’s from the research sector into the commercial sector. When deploying a research WEC, the environmental impact is relatively tiny when compared to that of an array of WEC’s due to the area of water the array would take up. For this reason, the EU requires an Environmental Impact Analysis, or an [|EIA], to be conducted. Some criticize the EIA due to its bureaucratic nature[15], but nevertheless, an EIA serves as both a public service and an applied science in order to methodologically decide if an emerging technology will not harm the environment it exists in (See fig 3). [16] Although meagre data exists on arrays of WEC’s, the threat WEC’s could pose on [|benthic vegetation and fauna] is concerning when considering the entire ecosystem as a whole. [17]

Sicily
Using a case study of a floating point WEC located in Sicily, researchers analyzed the impact of a WEC on [|wave climates], [|plankton] , [|pelagic fish species] , [|invertebrates] , and [|ornithological species] .[18] Specifically, they examined the effects of noise pollution, visual impact, insertion of chemical pollution, and barriers to marine navigation WEC’s pose on the environment during their installation, testing, and uninstallation.

Marine Environmental Impacts

 * Wave Climates: Researchers are lead to believe WEC’s will not have a large effect on wave climates.
 * Plankton: While the floating point WEC may alter the movement patterns of plankton, researchers conclude that there is currently insufficient data to quantify this effect.
 * Pelagic Fish Species: Due to the shelter from predators a floating point WEC provides, as well as a place for food resources to gather, the WEC would act as a fish aggregating device.
 * Invertebrates: Only invertebrates belonging to the [|phylum][|Cnidaria] were found to be affected by the WEC. The long stinging tendrils characteristic to this phylum may become lodged in the WEC, and researchers are unsure if this is a major or minor problem.
 * Ornithological Species: Researchers concluded that birds may use the WEC as a roosting area.

Visual Impact
The visual impact of the WEC was found to be both beneficial and detrimental depending on the use case. If placed on a coastline, a WEC will obscure the view of the ocean from the land, but also poses as a waypoint for boats and other ocean vessels. A reflector or some other navigational instrument may be placed on the WEC to aid boats navigating back to land. The researchers concluded that the negative effects on the landscape are minimized when a WEC is placed 1.5 kilometers away from the shoreline

Noise Impact
Noise pollution was found to be almost nonexistent for a floating point WEC. However, for any WEC that uses a turbine as the main source of generating energy, there will be noise generated underneath the water, but turbine WEC’s were outside the scope of this research.

Toxic Emissions
For marine installations, the main source of toxic emissions comes from internal fluid leaks or from paint dissipating into the ocean. For the floating point WEC used in this study, neither of these issues were problems.

Scotland
Another study, focused on the environmental impact floating point WEC’s posed on seabirds, was conducted in Scotland. Scientists believe the way seabirds acquire energy would be changed by installing several WEC’s around the world. Possibly by scaring away possible food, taking up space where the birds could hunt, or in some other way we cannot easily determine[19] By using data on several different points of reference, researchers assessed what impacts WEC’s will make and which bird species will be impacted the most by:
 * Risk of Collision Mortality due to Structures
 * Exclusion from Foraging Habitat due to Behavioural Constraints
 * Benefit from Roost Platform
 * Benefit from Fish Attraction Device Effect or Biofueling
 * Disturbance by Structures
 * Disturbance by Ship Traffic
 * Habitat Specialization

By analyzing these seven factors, researchers were able to estimate which birds would most be affected by the placement of large arrays of WEC’s. They found that three species in the Scottish region of the world fell into “moderate vulnerability”, 19 species fell into “low vulnerability”, and 16 species fell into “very low vulnerability”. [20] Although this study was just performed for the Scottish region of the world, the method the scientists used could easily be applied to many different regions of the world. That being said, we cannot be sure of these finding either as they are mostly speculative. The best recommendation is to proceed with caution as we develop better WEC devices. = Conclusion =

Wave energy converters are an exciting and rapidly developing sector in the field of clean energy. Their use will allow us to generate upwards of 80,000 terawatt hours of energy, if not more. [21] While those numbers by themselves are extremely enticing, there are large steps to be made before we will be able to harvest that energy. The WEC’s must go through many more rounds of testing in order to mechanically be able to harvest the energy, as well as, many more environmental tests in order to be sure we are not hurting the planet more than helping it. Research on WEC’s is extensive, but much more needs to be done before we use wave energy in the same way we use wind or solar. = References =

[1]A. J. Garrido et al, "Sliding-Mode Control of Wave Power Generation Plants," IEEE Transactions on Industry Applications, vol. 48, (6), pp. 2372-2381, 2012. [2]A. Clément et al, "Wave energy in Europe: current status and perspectives," Renewable and Sustainable Energy Reviews, vol. 6, (5), pp. 405-431, 2002 [3]Minerals Management Service, Renewable Energy and Alternate Use Program, U.S. Department of the Interior, "Wave Energy Potential on the U.S. Outer Continental Shelf", US Govt., 2006. [4]A. J. Garrido et al, "Sliding-Mode Control of Wave Power Generation Plants," IEEE Transactions on Industry Applications, vol. 48, (6), pp. 2372-2381, 2012. [5]Falcão, A. F. de O, "First-Generation Wave Power Plants: Current Status and R&D Requirements," Journal of Offshore Mechanics and Arctic Engineering, vol. 126, (4), pp. 384, 2004. [6]S. M. Wang et al, "The Overview of Wave Power Generation," Applied Mechanics and Materials, vol. 614, pp. 141-144, 2014. [7]Z. Zhou et al, "Permanent magnet generator control and electrical system configuration for wave dragon MW wave energy take-off system," in 2008,. DOI: 10.1109/ISIE.2008.4677255. [8]Y. Lin et al, "Review of hydraulic transmission technologies for wave power generation," Renewable and Sustainable Energy Reviews, vol. 50, pp. 194-203, 2015. [9] J. P. Kofoed et al, "Prototype testing of the wave energy converter wave dragon,"Renewable Energy, vol. 31, (2), pp. 181-189, 2006. [10]Northwestern Energy Innovations, "Background", NWEI, 2013. [11]Office of Energy Efficiency & Renewable Energy, "Innovative Wave Power Device Starts Producing Clean Power in Hawaii", Office of Energy Efficiency & Renewable Energy, 2018. [12]Department of Energy, "Capturing the Motion of the Ocean: Wave Energy Explained", Department of Energy, 2015. [13]M. Faizal, M. R. Ahmed and Y. Lee, "A Design Outline for Floating Point Absorber Wave Energy Converters," Advances in Mechanical Engineering, vol. 6, pp. 846097, 2014. [14]A. Kolios et al, "Reliability assessment of point-absorber wave energy converters," Ocean Engineering, vol. 163, pp. 40-50, 2018. [15] C. Wood, Environmental impact assessment: a comparative review. Harlow, England; New York, N.Y.: Pearson/Prentice Hall, 2003. [16]M. Cashmore, "The role of science in environmental impact assessment: process and procedure versus purpose in the development of theory," Environmental Impact Assessment Review, vol. 24, (4), pp. 403-426, 2004. [17]V. Franzitta, A. Viola, M. Trapanese, e D. Milone, «A Procedure to Evaluate the Indoor Global Quality by a Sub Objective-Objective Procedure», Adv. Mater. Res., vol. 734–737, pagg. 3065–3070, ago. 2013. [18] A. F. de O. Falcão, «Wave energy utilization: A review of the technologies», Renew. Sustain. Energy Rev., vol. 14, n. 3, pagg. 899– 918, apr. 2010 [19]R. Langton, I. M. Davies and B. E. Scott, "Seabird conservation and tidal stream and wave power generation: Information needs for predicting and managing potential impacts," Marine Policy, vol. 35, (5), pp. 623-630, 2011 [20]R. W. Furness et al, "Assessing the sensitivity of seabird populations to adverse effects from tidal stream turbines and wave energy devices," ICES Journal of Marine Science, vol. 69, (8), pp. 1466-1479, 2012. [21] A. Viola et al, "Environmental impact assessment (EIA) of wave energy converter (WEC)," in 2015,. DOI: 10.1109/OCEANS-Genova.2015.7271679. = Hyperlinks =


 * Terawatt hours: []
 * Convergent Hulls: []
 * Low Pressure Head Turbines: []
 * EIA: []
 * Benthic Vegetation and Fauna: []
 * Wave Climate: []
 * Plankton: []
 * Pelagic Fish Species: []
 * Invertebrates: []
 * Ornithological Species: []
 * Phylum: []
 * Cnidaria: []