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Learning From The Past: Three Generations Of Wave Energy Development

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Learning From The Past: Three Generations Of Wave Energy Development

When observing wave energy’s past, it could reasonably be argued that there have been three generations of modern development in this sector. From the 1970s to the present day, there have been many ups and downs in our efforts to make wave energy commercially successful.
 
Wave energy devices have undergone multiple iterations over the past century. These have experienced problems and blind spots that the next generation of wave energy converters work hard to solve.

Technological Challenges

The purpose of a wave energy converter (WEC) is to produce renewable energy by converting mechanical energy derived from the ocean’s waves into electrical energy used to power homes and businesses.
 
Ocean waves are an extremely attractive renewable energy source. They are consistent, being available 90% of the day on average, and tend to peak when other renewable energy, such as solar, is low. Furthermore, the global wave resource is huge and in the US alone, sufficient to provide 25% of electricity demand.
 
While the resource may be consistent, ocean waves tend to have a high degree of variability. This means that the height of one wave to the next can vary significantly, as can the time between each wave. This variability is one of the main challenges faced when developing machines that can efficiently and reliably harvest the power of ocean waves.
 
A second major challenge faced is the environment itself. Saltwater is highly corrosive, and few materials can survive without problems. Steel, one of the most common materials in marine structures due to its low cost, is especially prone to corrosion and requires paint and constant maintenance to prevent problems. 
 
Any machine that can survive in the marine environment, adapt to varying wave conditions, and produce high-quality electricity will be a complex system, and likely to contain many moving parts. Complexity is not necessarily bad, but can potentially lead to more wear and tear over time, requiring frequent preventative maintenance. Without careful design to mitigate these challenges, wave energy converters can quickly become expensive and require a lot of money to maintain. 

First Generation

Modern interest in alternative energy surfaced as a result of the 1973 oil crisis. The Organization of Petroleum Exporting Countries (OPEC) imposed oil embargos which caused oil prices to surge. As a result, many countries began looking for alternatives to fossil fuels. 
 
One such device that was thought to be a possible gamechanger at the time was known as Salter’s Duck. This was a wave energy converter developed by Professor Stephen Salter at the University of Edinburgh. Experimentally, the device was shown, in ideal conditions, to be able to convert more than 90 percent of the waves into mechanical energy.
 
Salter was not the first or only person working on wave energy at the time; several other efforts were in place worldwide. Unfortunately, Salter’s Duck and this generation of wave energy converters never came to fruition due to economic conditions and an inability to secure funding. Once oil prices started to drop in the 1980s after the embargo ended, the enthusiasm for alternative energy began to dwindle. This was, at least in part, due to a rising desire for nuclear power, with opponents arguing that wave energy was not economically feasible.

Second Generation

In the 1990s, interest in renewable energy began to resurface due to the increase in price and volatility of oil, the increased dependency of developed countries on foreign oil, and growing focus on the climate. 
 
An understanding of the effects of carbon dioxide emissions on our environment began to settle in the minds of many, which helped spur the development of the first modern commercial wave energy prototypes.
 
The Pelamis P750 was arguably the world’s first commercial wave energy device. It consisted of a series of floating cylinders linked by hinges that drove hydraulic generators to produce electricity. In 2008, the Aguçadoura Wave Farm in Portugal became the world’s first commercial wave energy array when three Pelamis P-750 machines were connected to the grid. The Pelamis concept was inspired by the Salter's Duck and conceptualized by one of Salter’s former students at Edinburgh.
 
However, these first three generators had to be recovered after only four months due to technical problems, which were never fully resolved. The 2008 financial crisis prevented additional funding needed for repairs from being sourced and led to the project being shut down. The second generation of Pelamis WEC, the P-2, was launched in 2010, resolving many earlier issues. However, Pelamis Wave Power was unable to find additional investment, and went into administration in 2014. 
 
Another wave energy converter of this generation was the ‘Oyster,’ developed by Scottish firm Aquamarine. The machine consisted of a bottom-mounted flap that generated power. Aquamarine completed two full-scale grid-connected deployments of Oyster machines in Orkney, Scotland. Unfortunately, the technology performance was not enough to inspire further investment, and the company went into administration in 2015.  

Third Generation

Since this time, technology in the wave energy sector has made many technological advances.  Having learned from the mistakes of past systems, it seems that the remaining issue when it comes to further development is financing. Previous generations of WEC’s have been unable to reach a competitive cost of energy and have been too costly to maintain, leading to the ultimate abandonment of years of research and development. The recent rapid evolution of technology has enabled engineers to find new ways to boost power and significantly reduce the maintenance costs of wave energy converters.
 
One such next-generation device is the Triton WEC, designed by Seattle-based company Oscilla Power. The Triton is an evolution of what’s known as a two-body point absorber. Oscilla has used previously impossible optimization and modelling tools to develop a ‘multi-mode’ point-absorber system that can harness the energy in all directions while successfully adapting to its varying intensities. The Triton can also automatically submerge just below the surface when experiencing extreme waves. The use of advanced materials and composites in the design significantly reduces the need for maintenance, making it a reliable system.

Technology Convergence

There is an almost mind-blowingly large number of different concepts and approaches for wave energy converters. These have ranged from the simple to the bizarre, to the impractical, and are typically divided into general categories: Oscillating water columns, point absorber systems, terminators, oscillating wave surge converters, attenuators, rotating mass, overtopping devices, etc. In fact, Since the mid-1900s, there have been over 1,000 patents issued for different wave energy converters (WECs) each with their own unique technology and design. 
 
Unlike the wind energy sector with the universal three-bladed wind turbine, or solar power that utilizes photovoltaic (PV) panels, there is no universally accepted technological convergence in the wave energy sector. Although, there appears to be some convergence towards point absorbers for the leading competitors. In 2016, the DoE’s Wave Energy Prize saw more entrants in the ‘point absorber’ category than any other.
 
Technology convergence will allow research and development to aggregate around a central theme, speeding up development and consequently helping the adoption and acceptance of wave energy. 
 
“Certain environments and geographies will always favor certain concepts; there will be niche applications for any technology subset. However, for utility-scale wave power, we believe that while there are a few different ways to make very efficient point absorbers, the performance demonstrated by the Oscilla Power Triton ultimately has more advantages than using active/reactive control systems,” said Tim Mundon, V.P. of Engineering of Oscilla Power. 
 
The application of ocean waves as a renewable energy source offers a practical solution to reducing fossil fuel use. This emerging technology still requires funding to broach the final commercial hurdle. Yet, it has, at least, now made the technological advances needed to put it within striking distance of solar and wind energy.

Image courtesy of Oscilla Power

 

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