Sorry my fault, what I meant to say it that we try to achieve a running speed of about 1000 rpm in most situations, in the example I illustrated the rpm is around 1800rpm not 1000rpm.
The reason for my mistake is that I suggested we make the client a special with a large Pelton rotor of up to 0.5m in diameter to keep the speed below 1000 rpm. This would require 50 plastic spoons and only cost the client an extra $300NZ and with so many spoons wear rate would half (though cost twice as much to replace them). All the client would need to do is make a very large casing, we can only go up to 30 spoons inside our standard casing size, I prefer 24 spoon 240mm PCD rotor where possible. The client as always opted fort he cheapest option, we offer a 30 day money back trial on our standard product, this does not apply to a special so the customer decided to try a standard unit against my advice. Though at 130m head I was also keen to try it and observe what happens regarding wear rate. The casings are made such that two Pelton turbines can fit inside a DHL jumbo box when packed. We offer a deal to customers that if they buy two turbines we pay for the freight to your address as a discount. This works out at about $700 US each delivered. Alternatively we can get 3 kit set Pelton turbines in a DHL box, you make the casings yourself. This way you pay only for two units plus freight. We supply the third as a discount. This work out at $1000 US delivered. So for $333 US you get all you need to make a good PMG Pelton turbine (the only catch is you have to buy 3 at a time). All you need to do it make up the casing and modify the Smart Drive rotor as per our instructions, alternatively for an extra $200 US we modify all 3 kits here. When you move the rotor out the speed will increase and you keep doing this until you locate the point of peak power conversion. All we need to do is supply a smart drive that is close to what is required and be able to generate more power at the rpm required to allow for a drop off when the magnets are move out. If any body is interested in the test results for the smart drive including efficiency curves, I can email them to you. The smart drive runs very well at about 1000-1200 rpm, this is normal for most of our clients. This means that our rotor size is OK for about 60m of head. The Smart Drive is designed to run in a washing machine, the large plastic rotor is not balanced and for speeds above 1200 rpm we find that it is necessary to balance them. In lower head turgo applications say with 3m of head the smart drive will run at 400-500 rpm. With 4 x 32mm jets and a 150mm PCD rotor at this head you can generate over 300 Watts. It is this application where we tend to use turgo turbines. Normally the head is 3-10m with maximum flows around 20-25 L/s. It is just coming out of winter in NZ where flow rates are much higher. Many of these high head little streams almost dry up in summer, so for some times of the years the client only has 0.25 L/s. We have Pelton running from 10m to 130m with the same plastic spoons. We made a 0.5 rotor for a client once who only had a theatrical power output of 35 watts. With a large low speed rotor at 10m head we managed to get him 10 Watts. This is an extreme example, PV panels would be cheeper but this client already had PV and wanted to give it a go. It is always going to difficult to maintain efficiency at very low output powers. The client was very happy with it. Hope this answers your queries Regards Michael Lawley ----- Original Message ----- From: Max Klohn To: [EMAIL PROTECTED] Sent: Wednesday, November 03, 2004 3:40 AM Subject: Re: [microhydro] Abrasion and surface hardness El mar, 02 de 11 de 2004 a las 05:38, Michael Lawley escribi�: > Hi, > > To answer your questions. Below is data relayed to me by the client, I'm not convinced about the accuracy of the data but here it is. > > Original unit was running at 131m on the gauge, 24- volt battery system. > The client has opened up the jet measuring the exhaust water and current flow to the batteries. It seems a bit erratic to me so there is probably some experimental error here. Our agent called in recently and advise that his measurements were at best approximate, but is gives a general picture. > > Results below are for a worn bronze Pelton rotor > 2.5mm jet, 0.25 L/s, 1.5 amps, 36 Watts, 11% > 2.77mm jet, 0.3 L/s, 4 amps, 96 Watts, 25% > 3.0mm jet, 0.35 L/s, 7 amps, 210 Watts, 47% > 3.17mm jet, 0.40 L/s, 11 amps, 264 Watts, 52% looks quite good (way too good?) performance for a car alternator. why did he use so small nozzles? it seems he has at least 1 l/s available in his stream > > The only result we got back for our turbine was with 5.1mm jet on the same installation > delivering 30 amps at 24 volts. > > 5.1mm jet, 1 L/s, 30 amps, 720 Watts, 56% not bad... some efficiency gain. > > > We find that running a large rotor keeps the rpm down, the losses to air friction and bearings are less at a lower rpm. We still run the Pelton rotor at its optimum rpm and the Smart Drive magnetic rotor can be moved in and out to alter the running speed until you achieve maximum output. > My understanding is that (at least for Pelton runners) that there are optimum nozzle-to-bucket and nozzle-to-p.c.d. (10-11%) relationships that one should not stray too far. Is it the case too for Turgo runners? or is this arrangement more tolerant? > I cannot agree that there is any rotor efficiency loss, if you run it at its optimum speed (a little under half the theoretical jet velocity) the rotor will maintain efficiency. > with 130 m head you have a Vjet around 50 m/s, and if you go with a 1000 RPM generator you'd need a runner with about 40 cm p.c.d. to match vjet/2. What is the pcd of your turgo runner? Best regards, Max > Regards > > > > Michael Lawley > Renewable Energy Engineer > EcoInnovation > 671 Kent Road > R.D.1 > New Plymouth > New Zealand > > Phone: (NZ) 06 752 2765 > Web site: www.ecoinn.co.nz > email: [EMAIL PROTECTED] > > > ----- Original Message ----- > From: Max Klohn > To: [EMAIL PROTECTED] > Sent: Tuesday, November 02, 2004 2:32 AM > Subject: Re: [microhydro] Abrasion and surface hardness > > > > Hi Michael, > > a "large", low RPM rotor at such high head and low flow? what is the % > efficiency penality you get from that choice? > > I agree from my own experience that car alternators are quite > inefficient, so the smartdrive efficiency gain should compensate for the > rotor efficiency loss. Just for curiosity, how much power was your > client getting before and now? > . > Max > > El vie, 29 de 10 de 2004 a las 17:33, Michael Lawley escribi�: > > By way of example, we recently supplied a turbine on a site with a 135m of head, flow 0.5-1 L/s. > > > > The turbine the clients been using for the last 2 years had a bronze Pelton rotor made in the USA using a car alternator. The bronze rotor has been all but worn away after 2 years of continuous use. Also the car alternator needed the brushes replacing every 6 months and overhauling every 12 months. With a small PCD rotor it was running at about 2500 rpm. After 2 years of running the bronze rotor is very badly worn and unusable. > > > > We supplied this client a plastic Pelton rotor turbine on a trial basis to see what would happen. The rotor PCD is much larger as it is only running at 1000 rpm on a smart drive PMG. > > > > After 50 days on test the client has decided to purchase the turbine, he has indicated that some wear has occurred but is happy with the unit. After talking to the client most of the wear occurred when he was doing high flow tests. We has a 100mm line (way to large for the low flow he has most of the time). When he opened up the line with a larger jet accumulated grit/slit in the line started to move and sand blasted the rotor for may hours (the line is long and it took time to clean out). His view is that most of the wear occurred at this time as up to this point there was no noticeable wear on the spoons. > > > > We normally only approve them up to 100m of head. You can see from this example that 135m might be pushing it. Even if the spoons only last 6 months, 4 sets are still only a fraction of the price of the bronze unit. In fact he could buy over 10 sets of replacement spoons for the price of one bronze rotor. If you always have a spare set on hand then it is not a problem. It will not be long before we see Chinese injection moulded Pelton spoons that will make even our ones look expensive. > > > > Metal spoons have advantages but the labour component required to polish and balance them means that there are expensive to make in developed countries with high labour rates. Injection moulding on the other hand takes about 10 seconds a shot. > > > > For most clients in the 20-70m range (that we commonly supply) we have not had any reports of wear problem and we have enough of them out there to have heard of a problem if it existed. We wouldn't give a 2 year warrantee if we thought they wouldn't do the job. > > > > > > > > Regards > > > > > > > > Michael Lawley > > Renewable Energy Engineer > > EcoInnovation > > 671 Kent Road > > R.D.1 > > New Plymouth > > New Zealand > > > > Phone: (NZ) 06 752 2765 > > Web site: www.ecoinn.co.nz > > email: [EMAIL PROTECTED] > > > > > > ----- Original Message ----- > > From: Marc de Piolenc > > To: [EMAIL PROTECTED] > > Sent: Friday, October 29, 2004 1:52 PM > > Subject: [microhydro] Abrasion and surface hardness > > > > > > > > I'm a little disturbed at the assumption, evident in > > many recent messages, that a hard surface is > > necessarily more resistant to abrasion than a soft > > one. This is not correct, and people on this list in > > particular need to be aware of that. > > > > When a hard abrasive particle hits a hard surface, it > > loses nearly none of its kinetic energy, and in a > > turbulent stream may strike the surface again and > > again, each time spalling or scraping off a small > > amount of material. > > > > When it hits a soft surface, it tends to lose energy - > > essentially embedding itself temporarily. This can > > often result in LESS wear on a soft surface than on a > > hard one. The ultimate useful application of this > > property is in an industrial process called lapping, > > in which a soft tool (the lap) charged with an > > abrasive, is used to remove material from a much > > harder workpiece. > > > > It is therefore incorrect to assume that a plastic > > turbine bucket will necessarily have less wear in it > > than a metal bucket of the same profile. It MAY be so > > - not all soft surfaces have the property of resisting > > wear - but that must be substantiated by test. Surface > > hardness is only one of the relevant parameters. > > > > Best, > > Marc de Piolenc > > Iligan City, Philippines > > > > > > > > __________________________________ > > Do you Yahoo!? > > Yahoo! Mail Address AutoComplete - You start. We finish. > > http://promotions.yahoo.com/new_mail > > > > > > > > > > > > Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! > > > > NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. 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If not, please register free of charge and be exposed to the microhydro community world wide! > > > > NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. The microhydro-group does not endorse products or support the advertisements in any way. > > > > More information on micro hydropower at http://microhydropower.net > > > > To unsubscribe: send empty message to [EMAIL PROTECTED] > > Yahoo! Groups Links > > > > > > > > > > > > > > > > > > > > > > > > > Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! > > NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. 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