Wave power could be one of the world’s most abundant source of renewable energy, as oceans cover more than 70% of the earth’s surface and hold onto a large amount of energy. But what needs to be done so that the world’s oceans can become attainable, sustainable energy resources? And how can wave power become competitive with other energy technologies?
Until significant amounts of money are invested into wave power research & development, this renewable resource with such enormous potential may take decades to catch up with where solar and wind energy were in 2010. The difficulties in harnessing wave power include saltwater erosion of energy-collection devices and the haphazard way that wave action rolls, bobs, and converges from multiple directions. Both of these impede wave power harvesting, among a number of other issues.
Then again, the vast possibilities to harness wave action provide a compelling allure for scientists, researchers, and designers. They have to figure out solutions for wave energy production that are practical, economic, safe, and environmentally friendly. That’s all, right?
Wave Power 101
Why do waves occur? Uneven heating of the earth by the sun produces winds blowing from high- to low-pressure zones, thereby creating sea surface waves. In essence, the wind transfers energy to the waves.
The ocean waves transport energy over long distances — sometimes thousand of miles — before reaching a shoreline. Ocean water is in continuous motion because it is driven by the surface winds, but spatial gradients in temperature and salinity of the world’s oceans contribute to differences in our ability to harness wave power.
In general, large waves are more powerful. With high power density, waves could be a source of clean energy with the capacity to serve as a very low-cost energy source. In order to figure out if waves can become energy sources, researchers look at the temporal and spatial variability of the ocean as a resource. That means they analyze how waves vary over time and if waves, when measured at different locations, exhibit values that differ across those locations.
Indications so far are very positive. In the U.K., for example, the Carbon Trust says tidal and wave power could meet 20% of the country’s total energy needs.
And then there’s the marine domain itself. Several marine environmental factors come into play. What effects of wave energy extraction on the marine and coastal environment would occur, and are these effects harmful or helpful?
To capture wave energy, wave energy converters (WECs) harness the power of the waves. Challenges to fully harnessing wave power fall into the two broad domains of engineering and environment.
Why is Wave Power Considered Such a Valuable Form of Renewable Energy?
Ocean energy has greater predictability and availability than other renewable energy sources. Tides are predictable in time-frames, and waves have a forecast horizon up to three times more than wind, according to Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO), which uses science to solve real issues. The devices that capture wave power do not produce any harmful emissions or greenhouse gases. As a result, wave energy doesn’t pollute, is a secure energy supply, and allows companies and governments to obtain economic growth independent from resource usage.
Wave power is less variable than other renewable energy sources and is a concentrated form of renewable energy. Wave power devices can generate electricity on site and transmit it through deep sea cables to land. Others pass the wave energy along to land, where it is converted to electrical energy.
The proximity of favorable wave energy sites to ultimate end users is significant, thereby minimizing transmission issues. Notably, approximately 60% of the world’s population lives within 35 miles of a coast. Uninterrupted and continuous, wave power could be an enduring suppliers of the world’s future needs.
Canada is keenly aware that, in order to meet its 2050 emissions target — which is an 80% reduction on 2005 levels — calls for a massive ramping up in the generation of non-emitting electricity. Bryson Robertson supports wave power generation for British Columbia, especially, saying that there is only a 15% margin of error in an average four-hour wave forecast, “while wind and solar in the Pacific Northwest are closer to 77% and 86%, respectively. … This makes wave energy more reliable and therefore easier to integrate into the electricity grid.”
The U.S., too, looks like it’s getting much more serious about developing its vast wave energy potential. Researchers have been working at several relatively modest sites in Hawaii and the Pacific Northwest, and now the Energy Department has announced funding for a $40 million utility scale test site in the waters of the continental US, off the coast of Oregon.
Arguments against Wave Power
A central challenge to harnessing wave power is its complexity. Many designs have been attempted but several obstacles stand in the way of full and pervasive implementation. Believe it or not, one of the big problems with waves is that they have too much energy!
A huge problem has been developing a system that is robust enough to cope with the extreme conditions of the open waters and the enormous hundred-year wave. Why is a hundred-year wave so important to wave power collection? It is a statistically projected water wave which has a height that is, on average, met or exceeded once in a hundred years for a given location. Because it is a projection for the most extreme wave which can be expected to occur in a given body of water, this wave is generally considered as a model for designers of oil platforms, offshore structures, and now WECs.
The marine underwater world is lively and lovely, with different zones and organisms. Wave power structures will inevitably be colonized by sessile, or immobile, animals and algae, which may be different from those of surrounding marine environment. Thus, introduction of artificial structures has the potential to change local diversity of the adjacent fauna.
Environmental factors of concern, according to Langhamer at Uppsala University, Sweden, can be divided into abiotic (e.g., water and air quality), biotic (e.g., marine flora and fauna), and socio-economic (e.g., restricted areas, visual impacts). As environmentalists and climate change activists, we always have to be sure about nature conservation interests, either in terms of loss of species or habitat, barriers, or threats to particular species.
Will WECs offer better marine environmental protection from predation, new food sources, and increase feeding efficiency? Or will they introduce new species and patterns of competition, predation, and parasitism?
Another — and possibly the most significant — barrier to wave power generation is cost. When competing against more advanced clean technologies such as wind and solar, wave power generation can be hard to justify. Several wave power innovators continue to struggle to attract sufficient investment. Jason Busch executive director of the Oregon Wave Energy Trust — a non-profit group dedicated to helping advance the industry — says that there are too many variables, such as the price of natural gas or eventual passage of a carbon tax, to apply the experience of wind or solar power to a different technology and time period.
High costs and the very challenging ocean environment are proving to be barriers to wave power development, but obstacles are likely to be overcome, especially if governments are willing to contribute a greater share of the development costs.
Types of Wave Energy Converters (WECs)
The designs of WECs have not yet converged on a common system. Several classes of WECs in development are assessing the power of the waves. Some devices generate the electricity on the spot and transmit it via undersea cables to shore, while others pass the mechanical energy of the wave along to land before turning it into electrical energy.
The current array of buoy-type wave energy devices can be roughly divided in two types. In one type, the working parts are unenclosed. Benefits to this style of device include shedding the weight and expense of an outer hull, but anti-corrosion measures have to be increased. The kelp-like bioWave and the US Navy-backed StingRAY are two examples of that type. The other type hides all the goodies within a fully enclosed hull, which is now on its way to commercialization.
Here are some different styles of WECs that are currently being tested across the globe.
Wave power generators that were attached to foundations on the seafloor are used in the Lysekil Project.
Concrete foundations were chosen for function, compatibility, durability, and stability. The goals of the Project were to valuate the wave energy concept from physical, technological, economic, and ecological perspectives. The ecological results provide an emerging picture of the interactions between wave energy converters and the marine environment. Conclusions thus far point to the capacity of wave energy converter to enhance biodiversity in degraded marine habitats. Thus, it seems possible that the overall effect of wave energy converters on marine fauna will be positive, although large scale deployments and a longer time-scale will add more data and information to this conclusion.
Tidal turbine technologies extract energy from the tidal currents, which occur due to the gravitational pull of the moon and sun. When the tide rises, water flows past the turbines in one direction then is reversed when the tide falls. Turbines are located individually or in configurations. Tide turbine technologies do not restrict the flow of water, so their environmental impact is minimal.
Ocean thermal energy technology vaporizes warm sea water, and relatively high pressure vapor turns a turbine. Warm sea water can also be used as the working fluid in an open cycle system. Here, a fraction of the warm sea water is evaporated by passing it through jets into a chamber with lower pressure than the saturation pressure for the sea water temperature.
A “magic carpet” serves as an artificial ocean bottom with multiple applications. The device can feature thin rubber or elastic composite carpet stretched across across a grid of cylinders and double-action piston pumps. The carpet adopts the up-and-down wave motion of its waters and subsequently moves the attached piston pumps to produce hydraulic pressure with multiple applications.
Special buoys can convert the sea’s waves into megawatts (MW) and capture the energy embedded in ocean swells. Ocean Power Technologies deploys test devices to improve buoy-based technology. Through periodic full-scale ocean performance validation, this buoy system is attempting to provide cost-effective and environmentally-sound wave power generation and management technology. To do so, it integrates technologies in hydrodynamics, electronics, power conversion, energy storage, and intelligent computer control systems to maximize the extraction and conversion of the natural energy in ocean waves.
Those are the same principles that most wave power generating companies need to coalesce in order to capture the power of waves as a virtually unlimited renewable energy source.
Pilot Wave Power Projects
The constantly churning oceans that cover most of the Earth offer an inexhaustible source of clean energy. The amount of recoverable energy embedded along the continental shelf of the United States, for example, could reach to nearly a third of all the electricity the country uses in one year, according to estimates from the Electric Power Research Institute.
Wave energy possesses unique characteristics that offer an advantage over other renewables such as wind and solar energy, and several pilot projects are attempting to overcome challenges to harnessing wave power. Here are some of the fascinating and innovative wave power projects that are currently underway around the world.
- Carnegie Clean Energy (CCE) offers a combination of wave, solar, wind, battery storage, and desalination via microgrids. Microgrids are ideally suited to islands, off grid communities, and locations at the edges of existing grids.
- Carnegie Wave Energy has received a grant for the first international development of a wave power project. The first phase of the project is a 1 MW development. Development of the first phase is expected to be commissioned in 2018. It will be followed soon after by a phase planned for 2020/21, which will deliver a subsequent 15 MW commercial wave array.
- Britain has 35 out of the world’s nearly 130 wave energy and tidal stream device developers, which include Aquamarine Power and Marine Current Turbines.
- Scotland-based Pelamis Wave Power produces an offshore wave energy converter that looks like a colorful sea snake. Named for the species Pelamis platurus, the device spins on a chain to face wave direction. According to the National Geographic, five floating tube sections are linked by universal joints that flex in two different directions as waves roll down the machine’s serpentine length. Each joint houses cylinders that resist the wave-driven movements and pump hydraulic fluid to power onboard generators, sending electricity to shore via underwater cables. The Pelamis handles dangerous storm swells by simply passing through and under them.
- AquaHarmonics has won a $1.5 million grand prize to support the development of wave energy converters. The U.S. Department of Energy’s (DOE) Office of Energy Efficiency and Renewable Energy announced the winner of the Wave Energy Prize, which is an 18-month design-build-test competition that assesses early stage wave energy technologies by comparing a wide range of device types and evaluating them against a threshold requirement for high energy capture.
Wave power can eventually making a meaningful contribution to our global energy supply. Yes, there are obstacles, but these are a small price to pay for harnessing this immense source of clean, predictable energy. Especially if used in combination with other renewable energy sources, wave power can become a core method to reversing anthropogenic climate change.
Top photo credit: Foter.com