GB2039330A

GB2039330A - Energy conversion devices

Info

Publication number: GB2039330A
Application number: GB7900955A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-01-10
Filing date: 1979-01-10
Publication date: 1980-08-06

Abstract

An installation for the conversion of tidal energy comprises a tank (T) in which floats an inner tank (T1) containing water ballast. With rising tide the tank (T) is filled through inlet (7) with sea water through an intake pipe (9) and valve (8), thus raising the floating tank (T1). At high tide the valve (8) is closed and an outlet (6) opened to drain the tank (T) at a controlled rate into a lagoon (L). The tank (T1) accordingly falls and via hydraulic pumping rams (10) drives a turbine. The lagoon (L) has lock gates (2) which are opened to drain the lagoon (L) at low tide. Again, three outer tanks may be sequentially arranged in vertically-stepped fashion, the upper tank being filled from a river, or by a pump in a pumped energy storage system. <IMAGE>

Description

SPECIFICATION Energy conversion devices This invention relates to devices and installations for converting hydraulic potential energy into useful work or energy. It is particularly, but not exclusively, applicable to offshore and inshore devices and installations for converting tidal energy into useful work.

According to the invention a device or installation for converting hydraulic potential energy into useful work or energy comprises a tank or container, a bouyant body able to float on the hydraulic liquid within the tank or container, a controllable inlet for the tank or container to allow the liquid to flow thereinto to a higher level thus raising the bouyant body which floats on the liquid, an outlet which can be opened to allow the liquid to drain from the tank or container so that the level therein falls, and energy conversion means coupled to the bouyant body and operative to obtain useful power from the resultant falling weight of the floating body.

Preferably said bouyant body is also a tank which may contain water or other ballast to provide the maximum operative weight consistent with flotation at the lowest liquid level. Thus the invention conveniently provides an outer tank provided with said inlet and outlet, which may be controlled by valves or lock gates, and a ballasted inner tank which floats in the outer tank. Guide rods or cables may be mounted in the outer tank to guide the floating tank for vertical motion as the liquid level risesorfalls, and the outlet from the outer tank may drain into a lagoon or other volume with a horizontal crosssection which is large compared to that of the outer tank.As the invention is applied to the conversion of tidal energy, the inlet and outlet of the outer tank of an inshore installation are preferably both below minimum tide level with an intake pipe leading from the sea and the lagoon discharging back into the sea at low tide, through a valve and discharge pipe or lock gates.

The outer tank may be one of a plurality of functionally similar tanks arranged in parallel and draining into the same lagoon, although in a preferred embodiment a plurality of inner tanks are employed floating in the same outer tank or container. Alternatively, the outer tank may be one of a plurality of such tanks sequentially arranged at different levels with each upper tank draining into the one immediately below. This latter arrangement is particularly suitable for inland use with the uppermost tank fed, for example, from a river or stream.

Said energy conversion means may, for example, employ direct mechanical, hydro-mechanical or hyd roelectrical transmission. In the mechanical case a cable connected to the floating tank may transmit the movement thereof to turn an overhead transmission shaft which is coupled through step-up gearing to an electrical generator, for example. Hydraulic transmission may be achieved by a hydraulic ram arrangement connected between the bases of the two tanks so as to be extended when the floating tank rises and operating as a pump, hydraulic fluid which is displaced when the floating tankfalls being utilised, for example, to drive a turbine.

The invention will now be further described with reference to the accompanying drawings which illustrate, by way of example, four installations in accordance with the invention. In the drawings: Figure 1 is a diagrammatic plan view of a tidal energy conversion installation; Figure 2 is a sectional view on the line II - II in Figure 1; Figure 3 is a perspective practical detail view of a second embodiment; Figure 4 is a corresponding detail view of a third tidal energy conversion embodiment; and Figure 5 is a diagrammatic view of an inland installation which may be fed by a river or stream.

The installation of Figures 1 and 2 comprises in plan view a U-shaped masonry wall 1 set into the shore line with the open end of the U, which faces out to sea, closed by lock gates 2. A lagoon is formed between the lock gates 2 and a partition wall 3, this lagoon having a level concrete floor 4 which is at the minimum tide level experienced at the coastal location concerned. The volume contained behind the wall 3 provides an inshore outer tank Twithin which is disposed a row of floating inner tanks T1 to Ts floating on the sea water contained within the tank T which has a concrete base 5 lower than the bottom of the lagoon Land thus also below the minimum tide level.

A valved outlet 6 drains the tank T into the lagoon Land each floating tank is ballasted, normally containing water ballast, to provide the maximum working weight which is consistent with a draught allowing the inner tanks to float when the water is at minimum level. The tank T has an inlet 7 controlled by an intake valve 8 which connects to an underground intake pipe 9 out to sea, the inlet 7 being below the bottom of the lagoon Land hence also below the minimum tide level.

Each floating inner tank is associated with an energy conversion means employing hydraulic transmission, utilising a ram arrangement 9,10 com- prising a base block 9 fixed to the bottom of the tank T and from which extend rows of vertical hydraulic rams such as 10. The ram bodies 1 0a are fixed to the block 9 and the ram piston rods 10b are connected to the corresponding inner tank. The rams operate with a valved pumping action; when the floating tanks rise with the water level the rams extend and draw in water through an inlet duct 11, which water is subsequently discharged when the water level falls through an outlet duct 12. If necessary the extension of the rams 10 may be assisted by return springs fitted within the rams.The duct 12 leads via pressure control valves to a turbine house (not shown) in which the potential energy of the floating tanks is converted into useful work, for example the turbine driving an electrical generator. To increase the flow the duct 12 may be coupled to similar ducts from other tank installations, the total flow feeding the turbine.

The operation of the embodiment described is as follows. On a rising tide the intake valve 8 is opened, so that sea water floods into the tank T lifting the five floating tanks T1 to T5 within it, and this continues until full tide is reached at which point the intake valve 8 is closed so that thereafter movement of the floating tanks is completely independent of sea level.

The valved outlet 6 is opened to drain the tank T which discharges into the lagoon L so that the floating tanks T1 to Tg commence to fall and between them provide a completely controllable moving weight the energy of which is transmitted hydraulically by the ram arrangement 9,10. It will be appreciated that the extent to which the outlet 6 is opened will determine the rate of fall of the floating tanks and hence the rate of conversion of their potential energy at high tide.

The above cycle of operation is repeated at the next full tide, and the described installation may be one of several such installations which are operated sequentially so that the conversion of tidal energy spans the tides. Thus a constant source of power can be provided.

The lagoon L has a cross-section such that the tank T can drain into it completely without a substantial rise in the level of the lagoon, as any rise correspondingly reduces the potential energy which is available. At low tide the lock gates 2 are opened to drain the lagoon, after which they are closed so that after the next high tide the total lagoon volume is available and hence the maximum tidal energy can be converted for a given height of tide.

The floating tanks T1 to Tg are guided for solely vertical movement by means of guide rods which are not shown in Figures 1 and 2 but are as will shortly be described with reference to the alternative offshore embodiments of Figures 3 and 4 in which the vertical guide means are shown. Referring now to Figure 3, this shows a fabricated offshore outer tank T with a valved outlet 20 connected to an outlet pipe running to a lagoon (not shown) which is constructed inshore. The tank T is installed at a determined location offshore, chosen so that at the known minimum tide level for that part of the coast the water in the tank will be deep enough to allow for the draught of an inner tank T,. One side of the tank T is in this embodiment provided by lock gates 21.

On a rising tide the gates 21 are opened to provide rapid flooding of the tank T, and they are then closed at high tide. The outlet 20 is disposed at or below the minimum tide level.

The operation of this embodiment is the same as that of the earlier two figures, an open-topped inner floating tank Tn being shown the movement of which is guided by the aforesaid guide means. These means comprise four tensioned guide rods which extend vertically upwards from the base of the tank T and are engaged by sliding guide rings such as 23 mounted on the tank Tn adjacent the four corners thereof. As in the first embodiment the tank Tn is coupled to a turbine through a ram arrangement 9,10 with ram bodies 1 0a fixed to a ram base block 9 and the ram piston rods 10b connected to the bottom of the floating tank. In this case the ram arrangement for a floating tank consists of four parallel rows of five closely spaced rams 10.The inlet and outlet ram ducts are as before denoted by the reference numbers 11 and 12.

Such offshore tanks can be prefabricated, complete with rams, valves, etc., at a convenient dockyard and floated out to the required location where they are sunk and secured to the seabed. For maintenance and overhaul the tanks can be refloated and taken back to the dockyard, meanwhile being replaced by substitute tanks.

The embodiment of Figure 4 is similar to that just described in that one side of the offshore tank T, which in this case is of masonry construction, is provided by lock gates such as 30. An open-topped floating ballasted tank Tn is again guided for vertical movement by guide rods 22 and rings 23, in this case each rod being engaged by two vertically spaced rings 23. This embodiment is operated in the same manner as that of Figure 3, but the energy is transmitted mechanically rather than hydraulically.

To this end a cable 24 extends from the top of the tank Tn and passes around a horizontal transmission shaft mounted in bearings at the top of the tank T.

The arrangement is such that as the tank Tn falls it turns the shaft (not shown) which is coupled through step-up gearing to provide useful power, for example driving an electrical generator.

Figure 5 illustrates a sequential arrangement of three outer tanks T, T' and T" disposed in a stepped fashion. Each of these tanks contains a floating ballasted tank T1, T1, or T1", and the tank T has a valved inlet 40 while each outer tank has a valved outlet 41,41' or 41". Each inner floating tank is associated with its own ram arrangement 10. 10' or 10" for energy transmission and to drive a turbine as described in connection with the two earlier embodiments employing hydraulic energy transmission.

The tank T is filled with water through the inlet 40 from a river or stream, if such a suitable water energy source is available, or alternatively by a pump. Thus the installation can suitably form part of a pumped energy storage system. The controlled outlet 41 of the tank T discharges directly into the tank T', filling the latter while the potential energy of the floating tank T1 is converted by the ram arrangement 10. When the tank T' is full the valved outlet 41' is opened to discharge into the bottom tank T", the middle tank ram arrangement now driving the turbine until the bottom tank T" is filled, whereupon the last outlet 41" is opened and the bottom ram arrangement drives the turbine.

It will be appreciated that while the middle and bottom tanks are involved in energy conversion the top tank T can be refilling. Moreover the tanks can be drained sequentially at a rate matched to the top filling rate and such that energy conversion is uniform and continuous.

Claims

1. A device or installation for converting hydraulic potential energy into useful work or energy, comprising a tank or container, a bouyant body able to float on the hydraulic liquid within the tank or container, a controllable inlet for the tank or container to allow the liquid to flow thereinto to a higher level thus raising the bouyant body which floats on the liquid, an outlet which can be opened to allow the liquid to drain from the tank or container so that the level therein falls, and energy conversion means coupled to the bouyant body and operative to obtain useful power from the resultant falling weight of the floating body.