System for protecting coastal land from rise of surface of the sea

Abstract

A system for protecting a coastal land from a rise of the surface of the sea, wherein offshore dams and caissons containing pump-turbines are provided in such a manner that the caissons and dams extend in parallel with the coastline of the land. Partition dams are provided so as to connect the offshore dams and the coastline together to make ponds. The water level of each pond is kept lower than a preset level, which is several meters lower than an average level of the surface of the ocean, by an operation of the pump-turbines and avoiding not only the submergence of the coastal land due to the rise in the sea level caused by global warming, but also expanding the area of offshore land. A high-efficiency pumped storage power generation is conducted in which the development of tidal energy and seawater pumped storage power generation are combined with each other by carrying out tidal wave pumped storage power generation, in which the head of a water turbine is lager than the head of the pump, and which comprises lowering the water level of the pond to a level lower than the preset level by an operation of the pump at low tide during nighttime, and introducing seawater from the ocean into ponds by an operation of the water turbine at high tide during daytime to increase the water level of each pond up to the set level, whereby economical efficiency is given to the system equipment.

What is claimed is:  
     
         1 . A method for driving a pump-turbine comprising the steps of: 
 driving a pump during nighttime when the sea level of the offshore sea is lower than an average tidal level in order to pump water from a pond until the water level of the pond is lowered by several meters from a preset level; and    driving a turbine during daytime when the sea level of the offshore sea is higher than the average tidal level in order to raise the water level of the pond up to the preset level, whereby increasing an efficiency of power generation of the pump-turbine to about 100%.