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Ocean waves are generated by wind passing over the surface of the sea - a process which often begins many hundreds or thousands of miles from shore.

The first windmills in Europe appear in sources dating to the twelfth century. These early European windmills were sunk post mills. The earliest certain reference to a windmill dates from 1185, in Weedley, Yorkshire, although a number of earlier but less certainly dated twelfth century European sources referring to windmills have also been adduced.

The first windmill used for the production of electricity was built in Scotland in July 1887 by Prof James Blyth of Anderson's College,

Tidal stream generators look and work like underwater wind turbines. As opposed to using the rising and falling movement of the tides, tidal stream generators take advantage of the fast moving sea currents (tidal streams), which flow when tides are moving in and out. These tidal streams cause the turbines to rotate, turning the generators which generate electricity. Tidal stream generators have the advantage of being much cheaper to build, and do not have as much of an environmental impact as a tidal barrage. The turbines turn relatively slowly, hence do not affect sea life. This is different to tidal barrages which can disrupt fish migrating up rivers from the sea.

Tidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into useful forms of power - mainly electricity.

Earth is composed mainly of bodies of water---about 71 percent of the earth's surface is water. Ninety-seven percent of that is found in the oceans. Because the earth's surface is curved, the sun heats it unevenly. This causes winds to blow across the water and generate waves. The sun and moon also exert their gravitational pull on the earth, triggering wave-producing tides. Wave motion energy can be harnessed and generated into electricity.

Wave energy conversion takes advantage of the ocean waves caused primarily by interaction of winds with the ocean surface

According to studies, an economically competitive geothermal power plant can cost as low as $3400 per kilowatt installed.

Estimated cost of hydrogen per kilogram in a variety of scenarios With all of this in mind, here are the cost estimates per kilogram (which each include $1.25 for taxes): Hydrogen from natural gas (produced via steam reforming at fueling station) $4 – $5 per kilogram of hydrogen Hydrogen from natural gas (produced via steam reforming off-site and delivered by truck) $6 – $8 per kilogram of hydrogen Hydrogen from wind (via electrolysis) $8 – $10 per kilogram of hydrogen Hydrogen from nuclear (via electrolysis) $7.50 – $9.50 per kilogram of hydrogen Hydrogen from nuclear (via thermochemical cycles – assuming the technology works on a large scale) $6.50 – $8.50 per kilogram of hydrogen Hydrogen from solar (via electrolysis) $10 – $12 per kilogram of hydrogen Hydrogen from solar (via thermochemical cycles – assuming the technology works on a large scale) $7.50 – $9.50 per kilogram of hydrogen As mentioned above, a cost of hydrogen of $4 to $12 per kilogram is equivalent to gasoline at $1.60 to $4.80 per gallon.

Hydrogen as the Main Fuel of the Future Over the last decades hydrogen, (H2) has gained more and more attention as an environmentally friendly fuel and storage medium. Combustion of pure hydrogen produces only water as exhaust. Hydrocarbon and carbon oxide emissions can only come from motor oil in the combustion chamber. Nitrous oxide emissions result from the nitrogen content in the air and increase exponentially with the combustion temperature. By using H2 in fuel cells, practically no pollution occurs. In this respect, hydrogen offers emission levels that are much lower than existing and future standards.

Hydrogen is the most common of all elements in the universe.

The desire for a long-term transition to a hydrogen society is mainly based on the need to reduce polluting and climate-affecting emissions and the concern about depletion of fossil fuel resources. Today about 90 % of the world's energy consumption is covered by fossil fuels, and most of this comes from a limited number of regions in the world. Even if hydrogen will be used on a large scale in the future, there is still a need for an energy source to produce it. Renewable energy technology such as hydro electricity, wind, wave and solar power are in principle available, but are not yet mature for mass production and/or fully developed. 

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Ocean waves are caused by the wind as it blows across the sea. Waves are a powerful source of energy.

How it works There are several methods of getting energy from waves. One of them works like a swimming pool wave machine in reverse. At a swimming pool, air is blown in and out of a chamber beside the pool, which makes the water outside bob up and down, causing waves.   At a wave power station, the waves arriving cause the water in the chamber to rise and fall, which means that air is forced in and out of the hole in the top of the chamber. We place a turbine in this hole, which is turned by the air rushing in and out. The turbine turns a generator.

Once you've built a wave power station, the energy is free, needs no fuel and produces no waste or pollution.

Presnell explained that wind speed and duration help in determining the size and frequency of ocean waves. Another factor is called "fetch," referring to the span of water over which a breeze blows, and the longer a fetch, the more energy a wave can build up.