Beginning in 1986, a simply-constructed wave power plant was built in Norway, where it was operated for about twelve years. The plant was on the island of Toftestallen near Bergen, and it was intended as a demonstration project for interested groups. The TAPCHAN (TAPered CHANnel) directs the water from the incoming waves into a channel which rises and narrows, then empties into a raised basin. The water then flows steadily from this reservoir back to the ocean. In the process, it can power a conventional low – pressure turbine. The channel of the prototype plant had a 60 m wide opening on the incoming wave side and was between 6 und 7 m deep. The reservoir was at a height of 3 m above sea level. The incoming waves were steepened by the trumpet shape of the channel, so that they overflowed its banks, allowing the water to flow from the sides of the channel into the reservoir. The reservoir was lower than the end of the channel, preventing the water from flowing back out.
DISTRIBUTION OF THE AVERAGE WAVE POWER
The TAPCHAN in practice even exceeded by a small amount its planned output of 350 kW maximum power and 2 GWh annual energy production; this is so far a notable exception for wave energy power plants. Operating problems arose from earthslides after strong rainfall, pieces of rock flushed into the channel by the sea, and damage to the channel walls. In contrast to these constructional difficulties, the power generation with a standard water turbine caused no problems. However, there were no follow-up projects – probably because reserving large coastal regions for such storage power plants would not be economically feasible. Coastal regions are exploited today in so many diverse ways that the integration of new, area-intensive uses would hardly be enforceable.
In retrospect, one sees that the basic concept of this plant, i. e. providing electric power continuously and as required, is today relevant only for island systems. Large power grids, in contrast, can accept the fluctuating power generated by wave plants. Such systems are therefore currently being developed further with much smaller water storage basins, which do not “smooth out” the power output so effectively. Two examples of such projects are the Norwe
gian Slot-Cone-Generator, a land-based system , and the European WindDragon, a floating system (see Fig. 2).