Let­ters

Popular Mechanics (South Africa) - - Contents -

I thought you might be in­ter­ested in a South African first in wind mo­tors (rather than purely wind-driven tur­bines). Ro­to­sail is a patented tur­bine in­ven­tion (RSA patent ap­pli­ca­tion 2016/00808) that is con­cep­tu­alised as a wind mo­tor rather than purely a wind gen­er­a­tor. It could be con­nected to a me­chan­i­cal, pneu­matic, hy­draulic or elec­tri­cal sys­tem. It is en­vis­aged as DIY kit mod­els at one end of the spec­trum and, pos­si­bly, large grid-feed­ing mod­els, the size of oil-stor­age tanks at the other. The lat­ter may be barge-mounted in the North Sea, or power a weath­er­sta­tion in Antarc­tica.

Ro­to­sail in­cor­po­rates the tried and tested con­fig­u­ra­tion of hol­low hemi- cylin­dri­cal shells, overlapping and ro­tat­ing about a ver­ti­cal axis. The prin­ci­ple is in­cor­po­rated in many pro­pri­etary units cur­rently avail­able on the high-tech mar­ket. Ro­to­sail pos­tu­lates the prin­ci­ple of mount­ing a ro­tat­ing space-frame turntable on the ver­ti­cal axis shaft with the hemi- cylin­ders mounted on sec­ondary ver­ti­cal mount­ings on the turntable, hav­ing lim­ited ro­tat­ing abil­ity in or­der to close com­pletely or to be ex­tended fully or staged at any in­ter­me­di­ate point. In prin­ci­ple, there is no limit to the size of the shells.

The ad­just­ment is pow­ered by an on­board gen­er­a­tor, recharge­able bat­ter­ies and elec­tric drives, com­manded ei­ther man­u­ally, by a stan­dard re­mote ra­dio con­trol (sim­i­lar to those that op­er­ate TV sets or garage doors) or au­to­mat­i­cally by pre-set com­put­erised pa­ram­e­ters, re­lated to wind ve­loc­i­ties, ro­ta­tional speed, time, du­ra­tion or any other loaded pa­ram­e­ter. This func­tion could also be achieved, in cer­tain cir­cum­stances, by on­board pneu­mat­ics or hy­draulic cir­cuits.

In the fully closed po­si­tion, the unit is cylin­dri­cal and stream­lined and could be de­signed to re­sist even hur­ri­cane­force con­di­tions. It is fun­da­men­tal to th­ese over­rides that frontal area and ro­ta­tional speed would vary and be bal­anced, in or­der to main­tain power out­put at a given level, thereby min­imis­ing or elim­i­nat­ing vi­bra­tion, noise and down­stream tur­bu­lence such as cre­ated by pro­pel­ler-type wind­mills. It is an­tic­i­pated that, bear­ing in mind the unique prop­er­ties in­her­ent in Ro­to­sail, a fairly sim­ple gath­er­ing and spilling of wind would re­sult, although de­fin­i­tive test­ing is not yet com­plete.

Har­ness­ing of wind-power is po­ten­tially pos­si­ble 24/7 all year round, al­most ev­ery­where, whereas so­lar power is avail­able dur­ing day­light hours only (dur­ing win­ter, in high lat­i­tudes, that can be one or two hours in 24). Wind power can de­liver AC or DC power, as op­posed to so­lar power, which can de­liver only DC and re­quires in­vert­ing con­ver­sion.

That there is an abun­dance of sus­tained wind-power is ev­i­dent in the fact that, un­til the ad­vent of steam, wind was the pri­mary source of power for driv­ing pumps and ma­chin­ery, other than run­ning wa­ter, brute man­power or draught an­i­mals. In our con­tem­po­rary en­vi­ron­ment, wind farms gen­er­ate con­sid­er­able quan­ti­ties of power, but suf­fer from the draw­backs of high cap­i­tal cost. This is partly due to the need to el­e­vate the hor­i­zon­tal shaft axis for the blades to clear the ground. Power gen­er­a­tion and con­trol equip­ment are sit­u­ated high above the ground, cre­at­ing lo­gis­ti­cal prob­lems and con­sid­er­able ad­di­tional cost. An ad­di­tional com­pli­ca­tion is the need to ad­just for di­rec­tional vari­a­tion of the wind, with the re­sul­tant ad­di­tional cost and on­go­ing main­te­nance needs, plus the fa­cil­ity of ad­just­ing the pitch of the tur­bine blades.

Pre­lim­i­nary cal­cu­la­tions for Ro­to­sail in­di­cate that one square me­tre of frontal area would pro­duce 1 kw of “work” at a wind ve­loc­ity of 10 m/sec (36 km/h). De­fin­i­tive test­ing is not yet com­plete.

An­tic­i­pated sav­ings in cap­i­tal cost range from sig­nif­i­cant to huge, re­sult­ing from the con­cept’s sim­pli­fied de­sign and the pos­si­bil­ity of rel­a­tively un­skilled lo­cal man­u­fac­ture. In­stal­la­tions would be far less in­tru­sive than con­ven­tional wind tur­bines and could be sited on waste ground such as land­fills and rugged moun­tain sites. In­stal­la­tions might even be sit­u­ated above fac­to­ries and high-rise build­ings with­out sig­nif­i­cant in­tru­sion. Off­shore in­stal­la­tions could be barge-mounted rather than on the sea-bed, with sig­nif­i­cant sav­ings in ini­tial costs and on­go­ing ser­vic­ing costs.

Other pos­si­ble ap­pli­ca­tions range from hy­brid pow­er­ing of ship­ping to ex­pand­ing the range of to­tally bat­tery-pow­ered road ve­hi­cles us­ing in­de­pen­dent self-pow­ered “pit-stops” that might bridge desert ar­eas, such as the Ka­roo, where peren­nial air move­ment is a norm. KEITH HONEYMAN CAPE TOWN

Work­ing model shows Ro­to­sail tur­bine open (top) and closed.

Plan view of open­ing se­quence.

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