GB2327241A

GB2327241A - Tidal pumped storage power generation

Info

Publication number: GB2327241A
Application number: GB9723875A
Authority: GB
Inventors: Kinno Hitoshi
Original assignee: Earth Science Laboratory Corp
Current assignee: Earth Science Laboratory Corp
Priority date: 1997-07-10
Filing date: 1997-11-13
Publication date: 1999-01-20
Anticipated expiration: 2017-11-13
Also published as: FR2765920B1; JPH1129921A; GB2327241B; CA2241686A1; GB9723875D0; FR2765920A1

Abstract

A tidal pumped storage power generation arrangement in a tidal bay leaves a tideway 1 extending from the mouth of the bay to the innermost end thereof, and comprises a waterway defining adjacent basins enclosed by barrages on the tideway side and at mutually adjacent sides with pump-turbines at the tideway side. The basins (4,8,9..) may be used for ebbtide power generation and basins (5,6,7...) for flood tide power generation. The water level of the basins is further elevated for ebbtide generation and further lowered for flood tide generation at night by using electric power from the national grid.

Description

MULTIPLE TIDAL PUMPED STORAGE POWER GENERATION ARRANGEMENT AND METHOD OF CONSTRUCTING THE SAME AT TIDAL POWER SITE This invention relates to a multiple tidal pumped storage power generation arrangement, free of sluices, harnessing both a pumped storage power and a tidal power, and to a method of constructing the same at a tidal bay site capable of tidal power generation.

Hitherto, a tidal power generation plant has been run using a single basin at one bay, for example, as in the Severn Barrage Project,U.K (General Report, Energy Paper Number 57, Dept. of Energy, London: Her Majesty's Stationary Office, 1989); and a tidal pumped storage power plant using two basins at one bay was known in the art, for example, as described in UK Publication No. 2145165A.

With the former case, the basin for power generation was built by closing a tidal site, for example, a bay, creek, or the like at both shores thereof with a barrage (31 in Figs. 1 and 3).

When the building of a basin of a larger capacity is intended with the advance of construction technology, it will be necessary to build a new larger barrage (32 in Figs.l and 3) outside the previous barrage (31), which means that the previous barrage becomes useless.

This fact caused to delay the decision making of whether to construct a tidal power generation plant, or not.

Another problem is that the annual output energy from a tidal power generation plant is proportional to the area of a basin multiplied by second power of the mean tide range, and even if the size of a basin is made larger, the mean tide range at the barrage site is smaller, as a result of which the output energy is not so much increased for that size enlargement.

It is a further problem that the maximum output of turbines is determined by a maximum tide range occuring at spring tide, but the output of the turbines at neap tide is reduced to about 1/4 the maximum output.

Still further problem consists in the troublesome manipulation of sluices. For instance, at ebb tide generation mode, the manipulation is repeated twice a day, wherein the sluices are opened to fill flood tide to the basin every one power generation is finished and the sluices are closed directly before ebb tide begins.

The sluices are not only laborious to manipulate, but also make the mean tide range small and act to attenuate the output energy because the sluices are closed in haste while the water level of the basin is not fully elevated when the ebb tide begins. Moreover, the construction cost of sluices is more expensive than that of barrages, and consequently, it is desirable that sluices be dispensed with.

In order to avoid the foregoing problems, the invention is designed to provide a multiple tidal pumped storage power generation arrangement free of sluices by dividing a bay ranging from its mouth to its bottom into two or three waterways, one of which is used for a tideway and the other of which is used for sluice-free basins for power generation. The basins are built each by enclosing a basin with a barrage that extends along the tideway and a barrage that extends squarely to the tideway, and installing a caisson mounted with a pump-turbine to the former barrage so as to face the tideway. One half of the basins is for ebb tide power generation mode and the other half of the basins is for flood tide power generation mode.

Accordingly, this invention is designed to provide a multiple tidal pumped storage power generation arrangement keeping a natural tidal range by constructing a power generation arrangement for a single basin and ebb tide generation mode and then, a power generation arrangement for a single basin and flood tide generation mode while operating the previous power generation arrangement, or vice versa, thus constructing power generation arrangements one after another in sequence to ultimately complete the multiple tidal pumped storage power arrangement composed of a plurality of power generation arrangements and attaining a maximum tidal energy.

According to one aspect, the present invention resides in a method of constructing a multiple tidal pumped storage power generation arrangement, which comprises dividing a bay site capable of tidal power generation into at least two waterways, one of which is a tideway extending from a mouth to a bottom of the bay and the other of which is a space for at least one series of basins for power generation keeping a natural tidal range; surrounding each of the basins with both barrages at the tideway side and at mutually adjacent sides and installing a caisson internally mounted with a pump-turbine at the tideway side, the basins being grouped into at least one basins operating at a single basin and ebb tide generation mode and at least one basins operating at a single basin and flood tide generation mode.

According to another aspect of this invention, a tidal pumped storage power generation arrangement is provided, which comprises at least one basins for a single basin and ebb tide generation mode and at least one basins for a single basin and flood tide generation mode, installed adjacent to one another so as to face a tideway of a tidal bay site, wherein the basins are operated at nighttime in such a manner that the water level of the former basins is elevated up to a specified level which is higher than a maximum level at spring tide by nighttime electric power of grid, thus maximizing a water head of the turbines and the water level of the latter basins is lowered to a specified level which is lower than the datum level by nighttime electric power of grid, thus maximizing a water head of theturbines, whereas at daytime, both the basins perform tidal pumpedstorage power generation by use of the water heads at an efficiency of 100% or more, whereby a continuous power generation is enabled at a maximum output of each turbine for 11 to 12 hours.

In a preferred embodiment, the bay site is divided into two or three waterways. The one waterway (an example of two waterways) or central waterway (an example of three waterways) is used for the tideway to keep a natural tidal range. The rest of waterways is used for a plurality of power generation arramgements each having a relatively small-scale output (e.g.,on the order of one million kW).

In dividing the bay site into waterways. first, for example, the bottom of a bay is applied to one basin, which is, in turn, surrounded by barrages and a caisson mounted with a pump-turbine to construct one tidal power generation arrangement. Then, a next basin is constructed likewise into a next tidal power generation arrangement, while running the first tidal power generation arrangement. Ultimately, the division into the waterways is completed and a multiple tidal pumped storage power arrangement is thus completed.

That is to say, a pump-turbine is mounted within the caisson and installed to face the tideway, with its electric power line having input and output connected to the land electric grid. When the water level of the tideway becomes higher than the mean sea level, the water level of the basin is elevated to a specified maximum level (e.g., a maximum level at spring tide), irrespective of spring tide and neap tide by pumping operation by the use of nighttime electric power without using sluices. At daytime conventional operation for ebb tide power generation is possible at a maximum output even at neap tide.

This is called a single basin and ebb tide pumped storage power generation arrangement.

Next, a single basin and flood tide pumped storage power generation arrangement will be constructed. A pump-turbine is installed at a deeper place than the ebb tide power generation arrangement since the the water level of the basin is used at a lower level than the mean sea level. The ebb tide power generation arrangement and the flood tide power generation arrangement are not necessarily installed adjacent to each other, but the position relation of the both may be chosen optionally.

The flood tide pumped storage power generation arrangement is operated so that when the level of the tideway becomes lower than the mean sea level, the basin lebvel is lowered to a specified limit which is lower than the datum level by running the pump by nighttime electric power of the grid. The lowering degree depends on the depth at which the pump-turbine is disposed, and consequently. the pumpturbine is disposed at a deepest possible place (30 meter or less beneath the mean sea level).

By combining the basin of the ebb tide pumped storage power generation arrangement called higher pond" and the basin of the flood tide pumped storage power generation arrangement called "lower pond", it is possible to generate, at daytime, electric power keeping each maximum output continually for 11 to 12 hours. Here, the water levels of the higher pond and the lower pond are made sufficiently higher and lower, respectively, than the natural tidal level by nighttime pumping operation, so that the heads due to the turbines are larger than natural heads, which results in an increase of artificial mean tidal range and accordingly, attaining a generating efficiency of 100% or more. The combination of daytime tidal energy portion (kWh) in addition to the pumped storage energy portion enables to obtain an annual output (kWh) of about two times the purchased nighttime energy (kWh). One reason why the generating efficiency is improved is that the pumps are operated at a smaller head (for example, when lowering the water level of the lower pond at nighttime, the water is evacuated from the pond to the sea with the pump at a lower level than the mean sea level by taking advantage of the performance that the smaller is the head of the pump, the larger the flow rate under the same shaft power condition).

In the ebb tide power generation arrangement, when the water level of the tideway becomes higher than that of the higher pond at nighttime when the pumps are not used, the rotary shafts of the turbines are released to free rotation, instead of using sluices, to assist sea water in refilling into the higher pond thereby to enable to reduce the perchased nighttime power.

The preferred embodiments of this invention will be hereinafter described in more detail with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic plan view of a multiple tidal pumped storage power plant constructed at a tidal bay site; Fig. 2 is a transverse sectional view of the plant of Fig. 1 taken along 11-11 line of Fig. 1 showing the relation between the depth of the bay and the installation depth of the pump-turbines, and the upper and lower limits of the water levels of respective basins at ebb tide pumped storage power generation mode and at flood tide pumped storage power generation mode, respectively; Fig. 3 is a transverse sectional view taken along m-m line of Fig. 1 showing the slope of the mean tidal range from the mouth to the bottom of the bay.

Referring to Fig. 1, a bay A as a tidal power site faces the ocean B and extends from a mouth A1-A2 of the bay to a bottom A3 of the bay. The mean tidal range (the difference between ebb tide and flood tide through spring to neap) is gradually increased from the mouth toward the bottom of the bay A in a slope of 34 to 35 as shown in Fig. 3 relative to a datum horizontal line 33. The bay A is divided into a tideway 1 extending at the bay shore side of Al to A3 and a waterway 2 extending at the bay shore side of A2 to A3, where a series of basins 4 to 9 for power generation are adapted to be built in sequence thereby to ultimately form a multiple tidal pumped storage power generation arrangement 3.

Here, the basins 4, 8, 9 are used for ebb tide power generation mode and the basins 5, 6, 7 are used for flood tide power generation mode.

Each basin is enclosed by barrages 11 and the bay shore of A2 A3, and the barrage 11 facing the tideway 1 has a caisson 12 mounted with a pump-turbine 13.

In one example of a bay A as shown in Fig. 2, its sea bottom (dotted line) is shallow near the mouth of the bay and is deeper at the middle place of the bay as shown at A4. A deep bay place that has a depth of 30 meter or more from the mean sea level is not suited for tidal power generation and is advantageously used for a tideway.

This is because the construction cost of barrages is proportional to the second power of the depth. Taking the fact that a deep place of the bay is not always its center place into account, it is better to make a narrowest possible tideway 1 by linking deeper places of the bay, which enables to allocate a greater area to the basins.

At flood tide power generation mode, it is desirable that the pump-turbines 13 of the basins 5,6,7 be installed at a deeper position 25 of within 30 meter below the mean sea level as shown in Fig. 2, and thus it is possible to construct flood tide power generation arrangements in series, insofar as a balance in the power output (kW) between ebb tide and flood tide power generation modes is eventually kept.

The operation of the tidal pumped storage power generation arrangement of the invention will be explained by way of example of one higher pond (e.g.,4) and one lower pond (e.g.,5): In the ebb tide power generation arrangement, the water level of the basin 4 is, at nighttime, elevated to a maximum specified level 22 (for example, Z meter above the mean sea level 21) by pumping operation irrespective of spring tide and neap tide, whereas at daytime power is generated to produce a turbine power (kW) such that the water level of the basin 4 may be changed from 22 to 21.

In the flood tide power generation arrangement, the water level of the basin 5 is lowered to a minimum specified water level 23 (e.g.,2 X Z meter below the mean sea level 21) by pumping operation at nighttime irrespective of spring tide and neap tide, whereas at daytime, power is generated to produce such a turbine power (kW) that the water level of the basin 5 may be changed from 23 to 21. Here, the reference numeral 24 designates a datum depth, which is a depth (Z meter) from the mean sea level 21 at a minimum water level at spring tide.

As described above, the invention has advantages what follow: 1. Even when a plurality of tidal pumped storage power generation arrangements are constructed in series, the provision of the tideway extending from a mouth to bottom of a bay enables to keep a natural tidal range. Consequently, it is possible to construct many relatively small-sized tidal pumped storage power plants, with the result that a maximum energy of the tidal power site can be extracted.

2. The basins 4 to 9 form each an independent tidal pumped storage power plant constituting a pond (called here a higher pond or lower pond) for pumped storage power generation coupled with the ocean (tideway 1). While running one tidal power plant after its construction, it ispossible to undertake the construction of the next power plant, thus constructing power plants one after another, and consequently, it becomes possible to make a long-term construction plan. This enables to secure ample annual budgets.

3. By taking advantage of cheap nighttime electric power of the grid, the water level of the higher ponds is elevated up to a specified maximum limit for the ebb tide generation mode and the water level of the lower ponds is lowered to a specified minimum limit for the flood tide generation mode irrespective of spring tide and neap tide. As a consequence, it is possible to generate power every day at daytime for 11 to 12 hours at each maximum power output by availing themselves of a time difference of 6.2 hours between the ebb tide generation phase and the flood tide generation phase (one tide cycle is 12.4 hours).

4. Since the natural tidal range is amplified by operating the pumps at nighttime, the efficiency of the pumped storage power generation output portion is more than 100% even if the mechanical efficiency is estimated to be 70%, seeing that the output energy (kWh) is proportional to the second power the mean tidal range. In addition to this, a daytime output energy portion by tidal power generation is obtained. An overall output energy obtained from one basin is thus about 2 times that of the existing single basin type tidal power plant, which contributes to the reduction in the construction cost per kWh.

5. No sluices are used except for locks for ships, which reduces the construction cost. Even where any sluice is necessitated, the pumpturbines will do merely by releasing their rotary shafts to a free rotation state, since their conduit tubes serve as a Venturi tube type sluice.

Claims

Claims:

1. A method of constructing a multiple tidal pumped storage power generation arrangement harnessing tidal power and pumped storage power at a bay site capable of tidal power generation while keeping a natural tidal range, which comprises dividing the bay into a tideway extending from a mouth to a bottom thereof and at least one waterway, extending along the tideway at one side and at least one shoreline of the bay at the other side; and building a series of basins for tidal pumped storage power generation in the waterway, said basins being adjacent to one another and being enclosed each by barrages both at the tideway side and at mutually adjacent sides and installed each at the tideway side with a caisson mounted with a pumpturbine.

2. A method as claimed in claim 1, wherein the basins are used for mutually reverse tidal power generation modes, the one being at least one first basin for a single basin and ebb tide power generation mode and the other being at least one second basin for a single basin and flood tide power generation mode.

3. A method as claimed in claim 1 or 2, wherein the tideway is disposed intermediate between two waterways, one of which extends along one shoreline of the bay and the other of which extends along the other shoreline of the bay.

4. A method as claimed in any of claims 1 to 3, wherein after either of the first and second basins is first built in the waterway, the other basin is subsequently built while operating the previous basin, thus building basins one after another, whereby the multiple tidal pumped storage power generation arrangement can be operated earlier even by only one basin and ultimately is completed to be operated at a maximum power.

5 A multiple tidal pumped storage power generation arrangement comprising first basins each having a pump-turbine and operating at a single basin and ebb tide generation mode; and second basins each having a pump-turbine and operating at a single basin and flood tide generation mode, said first basins and said second basins being installed at a tidal bay site capable of tidal power generation at its waterway opposite to a tideway extending from a mouth to a bottom of the bay so as to be adjacent to one another, wherein the pump-turbines of the first and second basins are operated, at night-time, by night-time electric power of grid to elevate the water level of the first basins up to an upper limit at spring tide and to lower the water level of the second basins to a lower limit, thus increasing the water heads of the turbines; and to generate, at daytime, tidal power at a maximum output of the turbines by harnessing the increased water heads, whereby power generation is enabled at an efficiency of 100% or more continuously for 11 to 12 hours.

6. A multiple tidal pumped storage power generation arrangement as claimed in claim 5, wherein the annual sum of an output energy from the pumped storage generation and an output energy of the tidal power

6. A multiple tidal pumped storage power generation arrangement as claimed in claim 5, wherein the annual sum of an output energy from the pumped storage generation and an output energy of the tidal power generation is about twice the night-time imported energy from the electric grid.

7. A method of constructing a multiple tidal pumped storage power generation arrangement, substantially as herein described with reference to the accompanying drawings.

8. A multiple tidal pumped storage power generation arrangement, substantially as herein described with reference to, and as shown in, the accompanying drawings.

Amendments to the claims have been filed as follows Claims: 1. A method of constructing a multiple tidal pumped storage power generation arrangement harnessing tidal power and pumped storage power at a bay site capable of tidal power generation while keeping a natural tidal range, which comprises dividing the bay into at least two waterways, extending from a bay mouth toward the innermost bay, including a tideway and at least one waterway as a space for basins; and building a multiplicity of basins for tidal pumped storage power generation in the waterway so that said basins may be adjacent to one another and be enclosed each by barrages at the tideway side and at mutually adjacent sides, said basins being installed each, at the tideway side, with a caisson mounted with a pump-turbine.

2. A method as claimed in claim 1, wherein the basins include a first group of basins used for a single basin type of ebb tide power generation mode and a second group of basins used for a single basin type of flood tide power generation mode.

3. A method as claimed in claim 1 or 2, wherein the bay is divided into three waterways, wherein the central one is for the tideway and the other two waterways extending along shorelines are for spaces for the basins.

4. A method as claimed in any of claims 1 to 3, wherein the basins are built one after another in a manner that after one basin of the first and second groups of basins is first built in the waterway, the other group of generation is about twice the night-time imported energy from the electric grid.

basins is subsequently built while operating the previously built basin until completion of the overall arrangement, whereby the multiple tidal pumped storage power generation arrangement can be operated at maximum power when ultimately completed.

5. A multiple tidal pumped storage power generation arrangement comprising a first group of basins each forming a single basin type of power plant operating at ebb tide generation mode and a second group of basins each forming a single basin type of power plant operating at flood tide generation mode, said first group of basins and said second group of basins each having a pump-turbine, said first group of basins and said second group of basins being installed at a tidal bay site capable of tidal power generation at its waterway extending, along a tideway, from a bay mouth to an innermost bay so as to be adjacent to each other, wherein the pump-turbines of the first and second groups of basins are operated, at night-time, by night-time electric power of grid to elevate the water level of the first group of basins up to an upper limit and to lower the water level of the second group of basins to a lower limit, thus increasing the water heads of the turbines; and to generate, at daytime, tidal power at maximum output of the turbines by harnessing the increased water heads, whereby power generation is enabled at a high efficiency and continuously.