GB2577340A - A tidal energy-harvesting unit - Google Patents

Abstract

A tidal energy-harvesting unit 10 comprises a chamber 20, eg built into the face of a sea cliff, having aperture(s) 40 along the lower edge of its seaward side to let sea water enter and exit the chamber 20 and at least one opening 80 in the upper part of the chamber 20 for trapped air to exit or enter depending upon whether the tide is rising or falling. A housing 30 is mounted on the chamber 20 and contains the exit of the opening(s) 80; rotor(s) or turbine(s) 50 driven by air displaced or drawn in through the opening(s) 80; a generator 60 powered by the rotor(s) or turbine(s) 50 to provide electricity to an external electricity consumption system, and an outlet and/or inlet 90 connecting the rotor(s) or turbine(s) 50 to the atmosphere outside the housing 30. The generator 60 and the rotor(s) or turbine(s) 50 are directly coupled together and the electricity can be set at a predetermined voltage and amperage.

Description

A ti dal energy-harvest i ng uni t The present invention r el at es to a ti dal energy-harvesting uni t usi ng both ri si ng and falling ti dal water f or produci ng el ectri ci ty at a pr edet errri ned voltage and armer age to be fed into an external el ectri ci ty consumption system Pr evi oust y proposed systems such as wave and wi nd systems f or produci ng energy face numerous chal I enges.

Wt h regard to W nd syst errs, sea-borne W nd turbi nes are costly to erect and suffer sal t-water corrosi on. They are al so di ff i cult to rrai ntai n and servi ce as they can be I ocated many rri I es out to sea, whi eh does not provi de f or easy access al I year round. Especial I y, duri ng storrry +mat her and excessive vssi nd speed, they can be shut down f or safety reasons and t hey can be a hazard to shi ppi ng and of I -rig supply vessel s. They f urt her affect t he envi ronrrent by their vi sual prof i I es.

W t h regard to wave syst errs, sea and wave hei ght movements are seasonal and subrrerged rrechani srrs have not yet provi ded si gni f i cant progress.

W t h regard to barrage syst errs, t hey are rrai ntai ned at a vast capital cost and often disruptive to fishing, shi ppi ng and nature. Thei r associ at ed under-water turbi nes are subj ect to salt-water corrosi on and t here are al so f ew sui t abl e sites inhere t hey can be effective.

Syst errs f or producing energy using ti dal forces have al so been proposed. As i nconi ng tide ri ses, i t di spl aces ai r corm-ens ur at e W th its own vol urre, si rri I ar I y an out goi ng tide pul I s down at rrospheri c ai r to repl ace its vol urre as i t recedes.

Si Each cubi c net re of seawater di spl aces one cubi c net re of ai r. If, however, t hat di spl aced ai r could be t rapped by causi ng t he incoming ti de to rise within a seal ed charter, t hen a 5 rret re hi gh ti de woul d produce 5 cubi c rret res of compressed ai r f or each square rret re of floor-space i n the seal ed chanter. Wien t hat sane ti de recedes f romt he seal ed charter, it WI! draw i n anot her 5 cubi c net res of at rospheri c ai r through an apert ure i n the charter. This rreans that i n each corrpl et e ti dal cycle, each square rret re of t he charrber woul d generate 10 cubic rret r es of ai r f I ow under pressure.

A t i dal energy-harvesting system usi ng this t echni que has been proposed i n t he t i dal power p1 ant of US Pat ent No. 4, 098, 081. This syst em corrpri ses three charrbers anchored to t he sea bed i n whi ch, ai r corrpressed by tidal forces, i s used to drive t urbi nes to generate rrechani cal or electrical power.

However, this syst em has t he di sadvant age t hat over t i rre, sl i ght rroverrent or subsidence of t he separated charrbers anchored to t he Si sea bed ni ght uncouple t he pi pe-work t hat erranat es from t he t op of t hose charrbers. Furt her rrore, t he whole syst em and its rrachi nery i s overcorrpl i cat ed and thus I i kel y to be rrore difficult and expensive to rrai ntai n.

It is an ai m of the present invention to provi de a tidal energy-harvesting unit whi ch addresses these di sadvant ages.

Accor di ngl y, a first aspect of t he present invention i s directed to a ti dal energy-harvesting unit corrpri si ng: a charrber i n whi ch at I east one si de of t he chanter has one or nore apertures al ong its I ower edge to I et sea water enter and exi t t he chanter and at I east one openi ng i n t he upper part of t he chanter f or t rapped ai r t o exi t or enter dependi ng upon Met her t he tide i s rising or f al I i ng; and a housi ng rrount ed on t he charrber contai ni ng: o the exi t of t he at I east one openi ng, o at I east one rotor or t urbi ne, whi ch i s connected to the at I east one openi ng, driven by ai r di spl aced or drawn i n by water rroverrent i n t he charrber passi ng through t he at I east one openi ng, o a generator powered by t he rot or or t urbi ne suitable to provi de electricity to be fed to an external electricity consurrpt i on syst era o an out I et and/or i nl et connected to t he at I east one rot or or turbine and t he at rrosphere outside t he housi ng, i n Mi ch t he generator and t he rotor or t urbi ne are di rect I y coupl ed together and t he electricity can be set at a predeterrn ned voltage and amperage.

The present i nvent i on provi des a regul ar and predeterrn ned energy source through a si rrpl e and cost-effective I and-based system Mi ch can be easi I y mai ntai ned. As t here i s no di rect cont act bet ween sea water and rrachi nery, t he system of t he present invention i s al so protected from corrosi on and i s non-di sr upt i ve to t he envi ronrrent. A further advantage of t he Si, present invention i s t hat t he system can never be acci dental I y or suddenly over! oaded Mi ch ITi ght I ead to a rrechani cal breakdown.

Advantageously, t he charrber can be positioned at a seasi de site so t hat at hi gh ti de t he internal ceiIing of the chanter preferably i s above spring hi gh ti de I evel by about hal f a metre.

Preferably, t he si des and rear of t he chamber nay be on land or rock.

In a pref erred errbodi rrent, it is al so possible to build a chanter into a sea-cliff face.

Thi s provi des t he advant age t hat a I and-based const r uct i on W I I be able t o be satisfactorily servi ced al I year round.

At t he start and end of each ti dal rroverrent, t here is a slack ti de hi ch i s a period Men t he rrovi ng water i s sl ow.

Mi I e this phenorrenon I eads t o a rri ni rra I generation of electricity, a f urt her advantage of t he present invention i s t hat t he slack tide i s cancelled out by t he regularity of t he Si, el ectri ci ty supplied by the system and its ti rri ng i s known i n advance.

Advantageous! y, t he ti dal energy-harvest i ng uni t corrpri ses only one rotor or turbi ne driven by air di spl aced or dram i n by water rroverrent i n t he chanter and entering t he housi ng from a first openi ng connecting t he chanrber t o t he housi ng, passing through t he rot or or turbine and exiting t he housi ng by an out I et during a rising ti de, and driven by air dram i n by water rroverrent i n t he charrber and ent eri ng t he housi ng by an i nl et and exiting t he housi ng by a second openi ng connecting t he rotor or t urbi ne to t he charrber during a falling tide i n which cont rol rreans cl ose t he i nl et and second openi ng during a rising ti de and cl ose t he outlet and first openi ng during a falling tide. This system i s a si rrpl e xney of generating electricity by usi ng both rising and falling ti dal water.

Pr ef erabl y, t he cont rol rreans i s a val ve rrechani sm corrpri si ng one or nine val ves arranged at t he ent rance or exi t of each openi ng, i nl et and out I et and cont rol I ed by t he control rreans conf i gured t o cl ose t he different openi ngs, i nl et and out I et of t he t i dal energy-harvesting uni t at cor r es pondi ng tide t i rre. An advantage t o this arrangerrent i s t hat t he system can be turned on and off at short notice to match the electricity derrand.

Advantageous! y, t he t i dal energy-harvesting uni t further corrpri ses one or rrore safety val yes. This provi des t he advantage to r el ease t he pressure int he charrber whenever t he ti de i s too hi gh or when t he system i s not requi red.

Preferabl y, the el ectri ci ty current i s carried from the generator to t he external el ectri city consurrpti on syst em over I and by cabl i ng.

In anot her errbodi!Tent, t he t i dal energy-harvest i ng uni t further corrpri ses one or rrore wind power-sources erect ed on t he t op of t he charrber or housi ng. This provi des t he advantage to use t he sane overl and cabling f or both power sources, to rrove t he generated electricity to t he ext ernal electricity consunrpt i on system In anot her errbodi rrent, t he t i dal energy-harvest i ng uni t f urt her corrpri ses a hel i cal I y driven power source i n t he apertures of t he charrber. This wi I I enable it to capture t he energy from t he water f I owA ng i nt o and out of t he charrber. -9 -

I n anot her errbodi rrent, t he t i dal energy-harvest i ng uni t further corrpri ses one or rrore wave power-sources connected to t he t i dal energy-harvest i ng uni t.

I n anot her errbodi rrent, t he t i dal energy-harvest i ng uni t f urt her corrpri ses one or rmre purrped trot er/ energy storage syst em added t o t he t i dal energy-harvest i ng uni t.

Preferably, t he tidal energy-harvesting uni t is rrade of non-corrosive rrat eri al. This wi I I provi de t he advantage to prevent t he det eri or at i on of t he syst em by at rrospheri cal I y sal t Si. part i c I es.

A f urt her aspect of t he present invention i s di rected to a syst em f or rri ng a cl uster of rmre than one tidal energy-harvest i ng uni ts independent to each of her. This provi des t he advantage to rrat ch t he electrical requi renrents of a srral I corrrruni ty, a large city or t he requi rerrents of t he external electricity consurrpt i on syst em as each uni t has its own generating capacity. A further advantage i s t hat single uni ts -10 -can be cl osed down i ndi vi dual I y I eavi ng t he of her units to continue generating el ectri ci ty f or rrai ntenance servi ces f or exarrpl e.

An exarrpl e of a ti dal energy-harvesting system i n accordance wi t h t he present invention wai I I now be di scussed her ei nbel ow i n r el at i on to t he accorrpanyi ng drawi ngs, i n whi ch: Fi gure 1 i s a cross-sect i onal vi ew of a ti dal energy-harvesting unit according t o t he present invention; Fi gure 2 i s an enl arged and rmre detai I ed vi ew of Fi gure 1 during a cycle f or a fl ood ti de; and Fi gure 3 i s an enl arged and rrore detai I ed vi ew of Fi gure 1 during a cycle f or an ebb tide.

Fi gure 1 shows a ti dal energy-harvest i ng unit 10 corrpri si ng a seal ed concrete chanter 20 and a housi ng 30 locatedd on directly on t he flat top of t he charrber 20. The seaward-f ng si de of t he charrber 20 has, i n this case, f our apertures 40 al ong t he I over edge to I et tidal water i n and out. The housi ng 30 contai ns a rotor 50, an el ectri cal generator 60, two openi ngs 80A; 80B exiting into the housing 30 f rom the chanter 20, an out I et 90A and an i nl et 90B passing through t he exteri or i n t he housi ng 30. The i nl et 90B i s covered by a cone 95 t o protect t he i nl et from t he weat her. The t i dal energy-harvest i ng uni t f urt her corrpri ses an exhaust safety valve 105A located on t he top of the chanter 20 next to t he housing 30.

1Ahenever a tide starts to rise, the ai r in the charter 20 i s forced outwards/upwards through an openi ng 80A i n t he top of t he charter 20 by vi rtue of the ri si ng sea-water enteri ng t he apertures 40. The ai r W I I be pi ped into and through a I ow-pressure rot or 50 Mi ch wi II, in turn, spin t he generator 60 bef or e exiting t he housing 30 by t he out I et 90A.

Si rri I arl y, y'kienever t he ti de starts to ebb and yvat er exits t he apertures 40 i n t he chanter 20, valves ( not shown i n the di agrarr) al I ow at rrospheri c ai r to enter through an i nl et 90 B -12 -and to be sucked downwards spi nni ng t he rotor 50 once rrore as i t repl aces t he exiting water.

In this errbodi!Tent, el ectri ci ty can be generated by both t i dal rroverrent s.

Figure 2 shows a rot or 50 with several bl ades 55 located i n t he housi ng 30 connected t o t he ai r rroverrent system through pi pes 70. Each openi ng ( 80A; BOB), out I et ( 90A) and i nl et ( 90B) of t he ai r rroverrent system i s controlled by a valve ( 1; 2; 3; 4) posit i oned i n t he pi pework between t he openi ngs ( 80A; 80B) Si and t he rotor 50, and bet ween t he out I et ( 90A) and i nl et ( 90B) and t he rotor 50 i n t he housi ng 30. A cont rol unit 110 i s I ocat ed i n t he housi ng 30 next to t he rot or 50 to enable t he cl osure and openi ng of t he valves t o cont rol electricity product i on during t i dal mwenents. Duri ng an i ncorri ng tide, ai r i s expel I ed outwards from t he charrber 20 and forced t hrough t he rotor 50 as t he wei ght of t he i ncorri ng sea water enters through t he apertures 40 of t he charrber 20. Val ves 2 and 3 are closed by t he cont rol -13 -unit 110 i n order to channel air through t he outlet 90A. Two pi pes 115A, 115B I ocat ed at t he top of t he chanter 20 each asi de of the housi ng 30 by about half a net er provi de addi ti onal ai r exhausts 105A; 105B f romt he chanter 20. They enable r el ease of t he pressure of t he chanter 20 Wien t he ti dal energy-harvesting system i s shut down. Each pi pe 115A, 115B contai ns a safety val ve 10, 20 positioned at the exit of the exhausts 105A, 105B. The i nl et 90B i s covered by a cone 95 t o protect t he i nl et from t he +neat her.

Si. Figure 3 shows the sarre drawl ng as i n Figure 2 operating Wien the ti de i s falling. Wien at rrospheri c air i s drawn down by vacuum pressure through i nl et 90B to t he rot or 50 by t he we' ght of t he sea water recedi ng through t he apertures 40 of t he chanter 20 as the ti de ebbs. Val ves 1 and 4 are closed by control unit 110 i n order to I et air exiting the rot or 50 pass through t he openi ng 80B into the chanter 20.

-14 - Suitable sites f or t he installation of a tidal energy-harvest i ng unit can be shorelines Mere t he ti dal range i s great est, shorelines Wii ch have a rocky base, shorelines Mere t he i rrrredi ate hinterland i s rrerel y a few rret r es hi gher than t he hi gh tide I evel, exi sting harbours t hat have becorre di sused or derelict, espl anade areas of existing coastal cities whi ch night be extended seaward, or cliff f aces of rock were t he sea st ri kes at t he base. This I i st of suitable sites i s non-exhaust i ve. The chanter can be seal ed and especi al I y can be rrade of Si rei nf or ced concrete. This al so can be of any length or breadth provi di ng its hei ght matches t he hei ght of t he I ocal ti de.

Claims (14)

1. -15 -Cl ai rrE 1. A tidal energy-harvesting unit corrpri si ng: a charrber i n Wii ch at I east one si de of t he charrber has one or rrore apertures al ong its I over edge to I et sea water enter and exit t he charrber and at I east one openi ng i n the upper part of t he charrber f or t rapped ai r t o exit or enter dependi ng upon whet her the tide is rising or falling; and C) a housi ng rrount ed on the charrber cont ai ni ng:CDo t he exit of t he at I east one openi ng, 0 o at I east one rot or or t urbi ne, whi ch i s connect ed t o t he at I east one openi ng, driven by ai r di spl aced or drawn i n by water noverrent i n t he chanter passi ng through t he at I east one openi ng, o a generator power ed by t he rotor or t ur bi ne suitable to provide el ect ri ci ty t o be f ed to an external electricity consurrpt i on system -16 -o an out I et and/or i nl et connect ed to the at I east one rotor or turbi ne and t he at rrosphere outside t he housi ng, i n Mi eh the generat or and the rotor or t urbi ne are di rect I y coupl ed together and t he electricity can be set at a predeterrri ned voltage and arrperage.
2. 2. A t i dal energy-harvesting unit accordi ng to CI ai m 1, i n Mi ch the chanter i s positioned at a seasi de site so t hat at N-- hi gh ti de t he internal ceiIing of the chanter preferably i s 1-11, above spring hi gh ti de I evel by about half a net re.O
3. 3. A t i dal energy-harvesting unit accordingg t o CI ai m 1 or CI ai m 2, i n vkii ch t he si des and rear of the chanter!Tay be on I and or rock.
4. 4. A ti dal energy-harvesting unit accordi ng to any precedi ng CI ai m i n vkii ch t he chanter i s bui I t into a sea-cliff face.-17 - 5. A ti dal energy-harvesting unit accordi ng to any precedi ng CI ai m i n which i t corrpri ses only one rotor or turbi ne driven by ai r di spl aced or drawn i n by water mwerrent i n the chanter and entering t he housi ng from a first openi ng connecting the chanter to t he housi ng, passi ng through t he rotor or turbi ne and exiting t he housi ng by an out I et during a rising ti de, and driven by ai r drawn i n by water rroverrent i n the chanter and enteri ng t he housi ng by an i nl et and exiting the housi ng by a second C) 1- openi ng connecting the rot or or turbi ne t o t he chanter during a N-..CDSi falling tide i n whi eh cont rol means close t he i nl et and second
5. CDopeni ng during a rising ti de and close the outlet and first openi ng duri ng a falling ti de.
6. 6. A t i dal energy-harvesting unit accordi ng to CI ai m 5, i n whi ch t he control rreans i s a val ve rrechani sm corrpri si ng one or fluor e valves arranged at t he entrance or exit of each openi ng, i nl et and out I et and control I ed by the control rreans conf i gured -18 -t o close the different openi ngs, i nl et and outlet of t he ti dal energy-harvesting uni t at corresponding ti de t i rre.
7. 7. A t i dal energy-harvest i ng uni t accor di ng t o CI ai m 5 or CI ai m 6, whi ch f urt her corrpri ses one or nrore saf et y val ves.
8. 8. A ti dal energy-harvesting uni t accordi ng to any precedi ng Cl ai m i n which t he el ectri ci ty current i s carried from t he generat or to the external elect ri city consurrpti on syst em over ^ I and by cabl i ng.* 9. A ti dal energy-harvesting uni t accordi ng to any precedi ngOt Si, CI ai ch furtherr corrpri ses one or rrore vu nd power-sources
9. Oerect ed on t he t op of t he charrber or housi ng.
10. 10. A tidal energy-harvesting uni t accordi ng to any precedi ng CI aim whi ch further corrpri ses a hel i cal I y driven power source i n t he apertures of t he charrber.
11. 11. A tidal energy-harvesting uni t accordi ng to any precedi ng CI ai m whi ch further corrpri ses one or rmre wave power-sources connect ed to t he ti dal energy-harvest i ng uni t.
12. -19 - 12. A tidal energy-harvesting unit accordi ng to any precedi ng CI ai m Mi ch further corrpri ses one or ntor e purrped water/energy storage system added t o t he t i dal energy-harvesting unit.
13. 13. A tidal energy-harvesting unit accordi ng to any precedi ng CI ai m i n will ch t he t i dal energy-harvesting unit i s rmde of noncorrosi ve mit eri al.
14. 14. A system form ng a cl uster of mire than one tidal energy-harvest i ng units independent to each other accordi ng to any precedi ng CI ai m