| 摘要 |
In ordinary so-called pumping power stations for converting inexpensive night electric power to expensive day electric power, operations are normally carried out between two large stores, for example a high-lying lake and the sea. Use is then made of what is in fact a constant level difference. High conversion efficiency is also obtained then, because the efficiency is roughly 90% in both turbine operation and pumping operation, that is to say a total of 0.9x0.9=0.81, that is 81%. With a cavity 2 in the earth's crust, for example an abandoned mine with a considerable drop to the bottom and a large volume, it can be used as a lower collecting store if it lies at least in part below the level of the surface of a nearby lake or sea. However, such poor conversion efficiency is obtained that it is not viable to operate in the same way as in an ordinary pumping power station, that is to say with the turbine pump positioned on the lower level on the bottom of the mine. Nor is it suitable, from the control point of view, to use a synchronous generator/synchronous motor for electricity generation or pumping back. The present invention indicates a method of solving the problem and of using inexpensive existing stores for pumping power station operation with good profitability. Turbine pumps are positioned at a number of levels in the mine, but preferably at two levels, for example 1/3 from the bottom and in the centre of the cavity, depending on how the area varies in the cavity. It is then possible to achieve good efficiency over the entire working range in both turbine and pump operation. Use is preferably also to be made of a standard asynchronous motor which can work as both a generator and a motor, because simple regulation is then obtained of the electric power which it is desired to deliver to the network in the daytime. The dimensions of the cavity are to be accurately measured as a function of the height in the cavity so that optimum use is made of the drop and the cavity is optimally used for energy production in the daytime. This is because it is also important to have maximum power and a large quantity of kilowatt hours available precisely during the highest electricity consumption peaks, which are usually 4-5 hours per day, because the electric power which is delivered then, peak power, can command a very high power charge in addition to the high kWh price in the daytime. <IMAGE> |
