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Wave Energy Introduction

Wave power is the transport of energy by ocean surface waves, and the capture of that energy to do useful work — for example for electricity generation, desalination, or the pumping of water (into reservoirs).

Wave energy is different from tidal energy, which is energy captured from tides. Tides are the result of gravitational forces that the sun and moon exert on the earth. Waves are the result of wind blowing over the sea.

Compared to renewable energy industries such as wind, solar and biofuels however, the wave energy industry is relatively new and some even consider it to be in its infancy

Wave Energy Potential

Research reveals that wave energy is a suitable renewable energy resource for certain coastlines in Australia, the United States, the United Kingdom, the Pacific Islands, Japan, China, Western Europe, South America and Africa. The International Energy Agency (IEA) estimates the worldwide potential for electricity production from wave energy technology to be 10 percent to 50 percent of the world’s yearly electricity demand of 15,000 TWh, depending on the expected load factor and wave regime. 

The most intense wave energy locations are found between 30^o and 70^o latitude in the northern and southern hemispheres. The UK, Portugal, Spain and Norway in particular harbour excellent resource. According to the Carbon Trust report Future Marine Energy (2006), the UK’s exploitable wave resource has been estimated at 50 TWh/year – enough to meet around 14% of UK electricity demand. An estimated 30% of Portugal’s electricity demand can be met from wave power. The Atlantic and Pacific coastlines of North and South America also offer excellent resource and commercial opportunities.

The potential market for wave energy is worth about $1 trillion worldwide, according to the World Energy Council, a nonprofit research organization. In the United States alone, wave technology could supply 6.5 percent of the nation's energy.

Wave energy technologies are the most heavily researched and funded sector in the ocean power industry. The potential to bring renewable electricity to a significant percent of the world’s population living within 60 miles of a coastal area is a key factor driving the outsized development of wave energy technologies.

A Global Wave Energy Resource Assessment

Source- Andrew M. Cornett

Canadian Hydraulics Centre, National Research Council

Ottawa, Ontario, Canada

Wave Energy - How it works

For wave energy conversion, there are three basic systems

• Channel systems that funnel the waves into reservoirs
• Float systems that drive hydraulic pumps
• Oscillating water column systems that use the waves to compress air within a container.

The mechanical power created from these systems either directly activates a generator or transfers to a working fluid, water, or air, which then drives a turbine/generator.

Among the above, float systems are the most popular.

The majority of companies developing wave energy technologies are working on devices called point absorbers. Point absorbers resemble offshore floats / buoys used for marking channels and collecting environmental and meteorological data. These devices are preferred over other types of wave energy devices because of their ability to absorb energy from oncoming waves in all directions. These devices bob in reaction to multi-directional ripples. Other wave energy devices are designed to absorb oncoming energy from only one direction or dimension in space.

Such multidirectional absorption, however, poses some problems. For instance, unless the wave energy is tuned to the wave climate in which it is submerged, energy will not flow smoothly through the power-take off system. Companies in the wave energy field are developing advanced tuning systems to tackle this issue.

It should be noted that different companies are experimenting with a variety of float systems, each having different designs and shapes.

Here’s a description of how the Pelamis Wave Energy Converter (WEC) works (The WEC is a snake-like float): WEC is a concept for extracting energy from ocean waves and converting it into electricity, direct hydraulic pressure or potable water. The system is a semi-submerged, articulated structure composed of cylindrical sections linked by hinged joints. The wave-induced motion of these joints is resisted by hydraulic rams that pump high-pressure oil through hydraulic motors via smoothing accumulators. The hydraulic motors drive electrical generators to produce electricity.

Regional Scenario for Wave Energy

The United Kingdom has led the development of the wave energy industry. As easrly as the 1970s, the U.K. Wave Energy Program provided £60 million in funding for wave energy research. A professort from the University  of Edinburgh (Prof. Stephen Salter) spearheaded most of the research, developing a prototype that laid the foundation for many of the current technologies. His device, called the Duck, reportedly absorbed 90% of the   energy incident on the device, and achieved conversion efficiencies of close to 90% at costs that were comparable to grid electricity costs. The country’s wave energy program was disbanded later, but the design and engineering advancements introduced by Prof. Salter provided the groundwork for future wave power research.

As a result of its geographical advantages, the potential for small wave projects seems highest in the UK, where wave power density is high and much of the wave energy research is centered. Other major countries with a direct interest in wave energy are Japan, Norway, Portugal, Denmark and USA. Some estimates suggest that these countries could derive a significant percentage (10-30%) of their total electric energy requirements from wave energy. 

Data and Statistics 

Wave Energy Status and Trends 

Current contribution of wave energy

Currently, wave energy contributes insignificant amount to the world’s electricity generation.

An independent market assessment estimated the potential world-wide wave energy economic contribution in the electricity market to be on the order of 2,000 TWh/year. That is about 12% of world electricity consumption (based on 2009 data) and is comparable to the amount of electricity currently produced world-wide by large scale hydroelectric projects. The potential world-wide wave energy contribution to the production of electricity is estimated by IEA (International Energy Agency) to be between 10 and 50% of the world’s yearly electricity demand of about 16,000 TWh.

The future of wave energy will depend on the efficiencies of the technologies under development. Capital cost will be a primary determinant in the success of wave energy. Other cost variables also play a significant role. Unplanned O&M costs, especially in the event of system failure related to ocean storms can increase the cost of energy significantly. Thus, investing the development of robust devices able to withstand heavy seas and high winds will likely continue to be a primary investment driver in this industry.

There have been estimates that investments of over £500 billion would be necessary for wave energy to contribute 2000 TWh per year worldwide.

Wave Energy Companies

* Fred. Olsen is a shipping company started in 1848. It entered into wave energy business in 2004

Source: Greentech Media and the Prometheus Institute for Sustainable Development

High Cost - Wave power is currently very expensive to produce. Between the high costs of devices needed to harness the power of the waves to the expensive efforts behind efficient generation of power from waves, it may be some time before the price of wave power can be competitive with power generation from coal or nuclear power plants.

Variable Energy Supply - The energy supply depends on waves and their intensities, which are variable. Even in the most active wave areas, there are many days with little wave activity. On days that have good wave activity, wave levels can vary. Resolving intermittency problems to attain reliable energy output can double and even triple the cost of power.

Limited Locations - While waves cover virtually every mile of water on the planet, economically accessible wave power is found only in coastal areas. Some areas are better than others and the best resources tend to be found only in the specific regions.

Design Bottlenecks - As wave power is scattered and the size of individual waves is limited, all designs are necessarily modular. Harnessing wave energy probably will not be done with a few, very large generators. Large-scale use of wave energy will likely involve thousands of small generators. Wave power is more energy dense than wind power, but it is still diffuse. Research data for the US shows that even in high wave energy dense areas such as the Pacific Northwest, one can expect energy production rates of about 1.5 MW for every 100 feet of shoreline occupied by generators. By comparison, a large fossil fuel plant of 1,000 MW capacity would occupy about two hundred acres. Installing a similar capacity using on shore wave power would occupy over 12.5 miles of shoreline; and that’s in the best areas like the Pacific Northwest.

Effects on Marine Life - The effects of wave energy systems on marine life are not fully known, and these could prove to be bottlenecks

Requirement of High-strength Device - One of the most challenging problems is the construction of devices that can withstand wave attacks over and over again. Designing and building a machine that can last for years despite being mashed by pounding waves is a difficult task, and may make or break the future of wave power.

Technology Development - The development process primarily consists of three phases. It begins with small-scale prototype devices that typically have a low capacity. Successful devices lead on to larger capacity prototypes, at this stage outside funding from government or private investors is possible for the most promising devices. The final stage, representing the culmination of development is the production of full-scale grid connected devices that will, in some cases, be deployed in farm style configurations. Only few prototype wave devices are close to entering the final stage and commercial deployment.

Despite the fact that a number of wave energy devices are getting closer to full-scale deployments, the fact remains that little real-world operational experience has yet been gained. Large-scale demonstrations are required in order to test survivability and efficiency issues that have not yet been resolved. It is difficult to assess potential of a system until it is tested in its final state.

A tiny proportion of all wave energy concepts are realisable to a commercial level. Drawing together, resources will ensure that the devices that do progress stand the best chance possible of succeeding. The SME (Small and Medium Enterprises) dominance of the sector is a barrier to development, as limited resources in many cases limit progress. These small companies are, in most cases, unwilling to collaborate as they naturally wish to protect their investment.

The European Commission - The aim of the commission is to strengthen the development of the markets and technology for ocean energy in the European Union. It has promoted cooperation between leading organisations and institutes, via the formation of a Thematic Network (www.waveenergy.net ) and a Coordinated Action (www.ca-oe.net). It has made direct contributions towards developing particular technologies, including: shoreline OWCs at Pico in the Azores, the Wave Dragon (www.wavedragon.com), the Wave SSG (www.waveenergy.no) and the SEEWEC (a multinational project to build a device containing an array of wave energy floats, www.seewec.org/).

The International Energy Agency - In 2001, the International Energy Agency (IEA) formed an Implementing Agreement on Ocean Energy (www.iea-oceans.org), which is the IEA’s mechanism for providing a framework for international collaboration in energy technology R&D, demonstration and information exchange.

The European Marine Energy Centre - It provides four test sites in 50 m water depth for wave energy devices, each with its own subsea cable, as well as a monitoring station and other facilities (www.emec.org.uk). The Centre has hosted a number of wave energy devices (as well as tidal current devices at a nearby site) and is proving pivotal in establishing wave energy as a reliable energy source (e.g. allowing developers to demonstrate their technologies in real sea conditions, coordinating activities around performance measurement and design standards).

•  Wave energy efforts worldwide - http://cesenet.org/documents/wave_country_notes.pdf
• Ocean wave energy - http://ocsenergy.anl.gov/guide/wave/index.cfm
• Wave Energy Today - http://waveenergytoday.com/
• WaveEnergy Centre - http://www.wavec.org/