Greetings Hugh et al, increasing the size of the Darrieus is helpful with regards to the costs of the unit to a certain extent. There are some companies on the market that propose large Darrieus schemes, however, they do not have any operational. http://www.bluenergy.com/ is one company and the other is Gorlov who is everywhere on the web. Myself, i have come up with a distributed generation scheme for larger power generation schemes. So in this method you would have a number of turbines operating on a water as working fluid system and providing power through a larger generator on shore. I beleive the larger Darrieus rotors have some significant problems with the mechanics offshore. Further dialogue on this is welcome if people are interested. Regards, Steve Gregory Alternative Hydro Solutions Ltd.
> -----Original Message----- > From: Hugh Piggott [mailto:[EMAIL PROTECTED] > Sent: Thursday, August 19, 2004 4:12 AM > To: [EMAIL PROTECTED] > Cc: Nando; Dennis Buller; Steve Gregory > Subject: Re: [microhydro] Aquair Submersible Generator > > > At 2:47 AM -0400 17/8/04, Lewis Burgess wrote: > > > >So does everyone agree, as Dennis pointed out, that increasing the > >capacity of Aquair-like generator is very costly and that this is the > >main reason why it is not used widely for power generation for rural > >communities? Does this also apply to the Garman and Darrieus turbines? > > It is nonsense to say that the cost of permanent magnet alternators > increases exponentially with size. In fact if you double the number > of magnets and double the number of coils then you can get 8 times as > much power at the same rpm, and with the same efficiency. > > Larger turbines tend to have lower rpm and this offsets the > advantages, but permanent magnet technology would still be quite > viable if you want DC output. However, larger systems are usually AC > based and would tend to use gearboxes and induction motor or > synchronous alternator generation. the friction in the gearbox and > the cost and maintenance issues are less significant on larger > systems. > > > >Finally, given the information above, is it feasible, given today's > >technology, to design a free-flow or submersible turbine that can > >generate 25kW and still be small enough to fit the site specification > >described above? I still have a glimmer of hope. > > I could not follow the site spec. but you have to realise that the > site is what governs the available power and I have a feeling that > the site is too small and the power just is not there. There > certainly are 30 kW stream turbines. For example the underwater > electric kite. I was given this data 3 years ago: > > > Based on our experience with the kinetic turbines, our > pre-commercial single 10 ft diameter RIVER turbine is producing: > > Water velocity, Vo= Maximum Power, kW > Maximum Thrust, lbs > > 4 knots / ~ 2 m/sec 33.5 kW 7,622.9 lbs. > 4.25 knots / ~ 2.125 m/sec 40.1 kW 8,605.6 lbs > 4.5 knots / ~ 2.25 m/sec 47.6 kW 9647.8 lbs > 4.75 knots / ~ 2.375 m/sec 56.0 kW 10,749.5 lbs > 5 knots / ~ 2.5 m/sec 65.4 kW 11,910.8 lbs > > > > Our new Tidal design has an output approximately 8-10 % lower > because of the efficiency of the bi-directional design. > > http://uekus.com/ > > > > -- > Hugh > > Scoraig Wind Electric > http://www.scoraigwind.co.uk/ > > [Non-text portions of this message have been removed] > > > > > > 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. 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 > > > > > > ------------------------ Yahoo! Groups Sponsor --------------------~--> $9.95 domain names from Yahoo!. Register anything. http://us.click.yahoo.com/J8kdrA/y20IAA/yQLSAA/FGYolB/TM --------------------------------------------------------------------~-> 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. 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 <*> To visit your group on the web, go to: http://groups.yahoo.com/group/microhydro/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
