Part 2

• Look through the text and choose an appropriate title to it:

1. Wave Energy Commentary

2. Wave Resources

3. Global Distribution of Deep Water Power Resources

As the waves move to shallower waters they can be modified by in­teracting with the sea bed in various ways, including:

Shoaling' — the height of a wave varies with the depth of water in which the wave is travelling. In very shallow water this can result in an increase in wave height or shoaling. This results in increased energy and power densities in shallower waters close to shore.

Friction and Wave Breaking — as waves become steeper²they can break, thereby losing both height and energy in turbulent water mo­tion. In shallower areas friction between the water particles and the sea bed can result in energy loss.

Refraction — as the waves propagate into shallow waters near to the coast, the wave fronts are bent so that they become more parallel to the depth contours and shoreline.

Diffraction³ - this is analogous to optical behaviour of light, lead­ing to waves bending around and behind barriers.

All these types of behaviour are dependent on the detailed variation of sea bed topography and can lead to the focusing of wave energy in concentrated regions called "hot spots". However, wave power levels close to shore are generally much less than those in deep water (e. g. around the UK wave power level at 20 m water depth is about one-

third of those in deep water). Outside the tropics, storms are usually more intense and frequent during winter, which results in wave power levels being higher in that season. Therefore, wave energy provides good seasonal load-following for those regions where peak electricity de­mand is produced by winter heating and lighting requirements (e. g. northern Europe, western Canada and north-west USA).

Wave energy was the subject of considerable research in the 1970's (as a response to the oil crisis) but the effort was much reduced through­out the 1980's. More recently there has been a resurgence⁴ of interest in developing wave energy for commercial use, with significant work being undertaken in numerous countries. This work is leading to more reliable and efficient devices, with corresponding improvements in the economics of wave power generation. It appears that this is a tran­sition time for several technologies as they move from theoretical as­sessment and small-scale tests to large-scale demonstration and com­mercial schemes. Many energy and engineering companies are starting to show a growing interest in these technologies. As a result, it is envis­aged that within the next five years wave energy will start to play an increasingly important role in complementing other renewable and conventional energy technologies.

1 - обмеление; 2 — круче; 3 — преломление; 4 — возрождение

• Answer the following questions using the information from the text.

1. What results in increased energy and power densities in shallow­er waters close to shore?

2. What are all these types of wave behaviour dependent on?

3. What is the future of wave energy?