Splynk: Like you say, you are just asking an impossible question (how long is a piece of string!),
A survey is needed to determine the best way to perform your needs and as shown by the various studies that you seemed to read -- you do not describe them -- the cost varies considerably indicating that the problem and its magnitude is determined by the site conditions. Excavations may be a good percentage of the total costs, as well as, the weir intake and debris filtering for this site ( my guess ). With a 2 meter head and 27 M^2/sec the channel would be around 4.25 square meters minimum, though one needs to determine the river water velocity at the site and site conditions. Total efficiency may vary toward a lower value that needs to be considered in the determination of the water volume needed. Most of the experts will not dare to suggest solutions due to the lack of proper information. Regards Nando ----- Original Message ----- From: "splynk" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Sunday, May 16, 2004 6:19 PM Subject: [microhydro] Low head hydro costs Hi, I'm interested in a run of the river scheme with a potential of at least 300kW. It consists of a 2m head, 45 degree straight concrete weir with flat river banks. Assuming 75% total efficiency, this means a flow of 27 cumecs would be needed through a turbine (the scheme would be capital rather than flow limited, such that 300kW should be possible for most of the year, apart from flood conditions causing the head to drop/disappear). Looking at various studies on the net, the assumed cost/kW for microhydro schemes vary considerably from less than �1000 ($1750) to over �3000. This isn't very helpful, so I would appreciate any figures the group could suggest for the breakdown of a typical low head scheme. I know its an impossible question (how long is a piece of string!), but perhaps someone can offer some typical breakdowns between the civil works/turbine/trash-racks/generators and controls/management and consultancy for this type of scheme. (I can get estimates for grid connection costs). I'm assuming that lower cost fixed pitch propellor turbines would be appropriate rather than expensive kaplans given the capital rather than flow limitations. Also being in the UK my understanding is that fine pitch screening would be required (don't want the cormorants to go hungry!) - given the capital limitations I'm assuming a manual rather than automatic trash rack cleaning solution would be appropriate). I am assuming that the civil works costs are likely to dominate - particularly for a low head scheme, and probably the hardest to estimate. Obviously a site survey would help considerably but I'm only at the stage of considering if this is remotely feasable. In this case I expect that access and excavation conditions should be benign (clay/shale - no rock) so I'm guessing that a large part of the cost would be for sheet piling to prevent water ingress into the excavation. Is this a reasonable assumption? What about possible solutions avoiding the need for sheet piling - eg. (please don't laugh too violently - I'm not a mechanical/hydraulic engineer!) dropping precast channel sections into a flooded excavation and pumping mass concrete underneath? How big a channel would be required to be excavated for the head and tailraces and turbine for that 27 cumecs flow? I'm assuming that a .1m (5%) head loss might be reasonable, but as I'm not a hydraulic engineer, any suggestions? Thats quite enough for one post, so please accept my thanks in advance for any suggestions/advice/well-deserved-ridicule you may wish to offer, Splynk Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? 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