IND: signingforJobs Figure 2: Airfoil Efficiency relative to Tip-speed Ratio I I designed to exrracr energy from the wind most efficientlv at a narrow. range of tip-speed ratio, as illustrated in Fig. 2. in_ stead of hydraulically rotating the blades to change iheir angle-of-attack for greater efficiency in higher wiids or to feath,er the blades in gales, as is common i-n today,s compli_ cated and costly rotor-hub designs, the familiar ,',stallingl' phenomenon was pur ro work. With ,.rnmouable blades iet to get the most power out in a narrow band of windspeeds, the wind.mill au_tomatically slows in higher winds as its blades rapidly get less efficient in sucking-off energy from the wind_ stream..lnstead of complex and hence expensive blade-feathering mechanisms, tbe feathering task itsetf is eliminated, as the interaction of wind and airfoil do the work almost narurallv. Simplicity need nor preclude scientific sophistication.6 , Emergency stop.ping, in case of potentiai lubricarion problems or disconnection from the eleitrical grid, is handlej by a simple brake flap on the tip of each bladel shown in Fig. 3. Or, as Juul explains, Tbe .b.lade llaps (1) constitute l2.percent of the surface area oi the.blades_and are, under normal'operatin[ conditi|ns oy tn,e hiU, an integral part ol'tbe blades. Eacb ol the"flaps is lixed io a tubul lar c.arrying rud (2) ubich will, when actuated by"the a.utomatics ol'.tbe mill, trauel about 3OO mm alony tbe lonpitudinal axis ol tlte bladc and moue in a link-mutioi tS) l" ihe lixed oart ol. tb.e blade. B.t' tbis mouement, the brake IIap i, t-ir,tri o'iiit' 6O degrees t,ut uf'tbp plane of tbe blade, tius counteractina the remlin.i;t1q.par.t oJ tbe blade and bringing the mill to a d"ead st-op.. I he br,,Re llaps are gouerned by a hydraulic sen)o_motor l5) rn connection witb tbe mill system of automatics. When tbe mill starts, tbe sento-motor witt itull tbe"brake llaps into uorkl_ iyg positio.n. Wben it stops, .the Zentrilugal poiei wiil loii the flaps out into braking position.T . Here the simple centrifugal forces naturally produced by the wind turning the blades provides the fail-iafe power foi an effccrive bral<ing sysre m. If the oil lubrication sysrem fails to properly cool vital bearings, another ingenious mechanism w,rrking on a temperature rise stops the wind-turbine before damage results, Betueen the bore (6) in tbe lixed spindle-.and the rotating oil pipe system oftlse hub,_a sellrtighteninf snlfing box (7) is iniertei.' Co,nn11t,ing uitls.tbe oil prissure fipe oj' tie spindle is a safety uatue.eJ), saateLl by a stopper rnade of a metal uhicb wil! melt a.t 110 degre,es C. In case oJ'beating of tbe spindle, due to deJects in the. bearings, .tbe siopper ditt".rnelt ind let out tbe oit, tbus st0pping tbe mill.8 Simple, workable, understandable, inexpensive. Often the most appropriate solutionio a problem is to totally ignore the supposed problem. preseni day wind_ machine designers pay much- atrenrion to bringing the power down the rower from a blade-hub-generaror .o'nfigur"tion which is usually set on a rotating tirntable. The conven_ tional wisdom says "slip rings," and we 've had all manner of them, engineered to rhe nth degree. Gedser just avoids them: Tbe ,cables to the &enerdtor as aell as the contiol cables are carrted to the machine cabin tbrougb a rubber tube fixed in the floor of the c.abin and lreely ,rrp"id"d in-;i, ;;:;;, so tbat it atu stand being twisted ten tutns eitber way uithout being damaged. .ln tbat.way tbe use ol'slip rings for cable connection to tbe cabtn hds been auoided. Experienle sbows tbat the yawing will cause, a.nnually, only aboui IO turns, clockuise. . In the touer-is placed a relay (3 I) connected witb a cord that pa,sse,s a pulley a.nd is uound round tbe rubber tube (3O) so as to disconnect tbe control cables, thereby stopping the' yauing,mecbanisn gyd the mill, in case the iobtes'get tuo manrl turns lt tbe monthly inspectio.n the miil .if necesTary_is turned bdck tbe.opposite ?ay, by manual operation i1.the yauinr mecnontsm, unttl tbe cord round the rubber tube hds'been -un_ uortnd.9 One need not say more. Yet there is more of this mechanical sensitivity, Anothe,r cord k also Jastened to tbe rela.y. It is connected witb a,loose.ly placed weight tb-at will lall offits stand and influence the relay, thus stopping the mill,-in ciie abnormal uibra'tions occur in the tower. 7O Lou D.ivone, manag€r of ERDA's Wind Energy program Branch, visited the 2o0kw Gedser and put it this wa/, J-oe^lSauino of NASA-Lewkl, Jean !Fisher ol F.L. Smidtb 6t LO.l anat I TDere tn tbe top ol tbe cab there, leaninsub asainst t h e. s o m e u h a t ru s ty e I e c ti i: al ge n e ro t o, i n d' i ;; ; ;; ;"" i, ;;;; ;; ?:::F tryblu"t:ed.by. the heigbt, when we sai soinetbin[ ind started to laugh. And then we stopped lor a minute andToohed 4t eactJ otber and decided tbat maybe ue sbould not be laushins 1nd ryaltbe tbe.desig;er ol'thk michine -i, oiii-i*i,t';;3""'" smart, I.turned to Joe and I said I uould tike to git a selarate cost astimate l'or putting that component ", tnf tb6i,i iirl;rr. As you can sec, tlJe automatic sbut.rll.deaice Ior tbe Gedser mill is a pipe that comes up liom the lloii and iiii, iiur,,a ro*" equrpment, and on the top ol'the pipe there is a cup in which l-!t.1!1M: uuersized bari. ibat tbti t, ,u""iriri'i.v o ,t,ios to an otd-Iasbtoned Square-D type switch on tbe wall.'When tlie
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