Robert,
There may be other people in the group who can answer your question with more practical examples. However, according to your last assumptions i.e. no load and 100% efficiency (nolosses due to friction etc.) the wheel turns so that the tangential velocity is exactly the same as the water velocity and no power is produced. If the wheel was driven faster than the water then power would be used up. Conversely if a load is attached the wheel moves slower than the water and will generate power. The maximum kinetic energy available per second (i.e. the power) is 0.5 mv^2 (half the mass times the velocity squared). In your example the volume of water passing a point is 3m x 1m x 2m (if I suggest a water velocity of 2 m/s). This is 6 tonnes (or 6000 kg) per second. 0.5mv^2 = 0.5 x 6000 x 2 x 2 = 12000 Joules or since it is every second Watts or 12 kW. I guess the efficiency would be highest at a particular rpm for a particular velocity although I expect efficiencies of much less than 50% in this type of set up. Kind Regards, Martin *********************************************** Martin J. Leahy DPhil (Oxon) CPhys MInstP FRAMI Millstream Energy The Millstream Abbeyfeale Co. Limerick IRELAND Email: [EMAIL PROTECTED] TEL: 00353 61 213056 Mobile 086 6055572 FAX: 00353 61 202423 *********************************************** -----Original Message----- From: Robert Vitale [mailto:[EMAIL PROTECTED] Sent: 03 November 2004 15:38 To: [EMAIL PROTECTED] Subject: [microhydro] energy estimation from flow rate Mr. Leahy, I saw your response and was hoping to ask a follow-up question. I am in the business of making metal waterwheel and people all the time are asking me how much power would a stream paddle wheel produce. Can you help me simplify you answer below to an example. If I wanted to figure out the Power (kw) or just HP of a paddle wheel with a given flow rate (any number will do) with a flat paddle (one paddle at a time in the water) lets say 3 meter wide by one meter deep. (We are dealing with the pressure of the mass of water on the surface of the paddle are we not?) How would you figure out the potential power. If the paddle was rounded to cup the water (side to side) would that change the power number. Are there other variables I need to include that I have not stated, If so, please assume some working numbers for an example. Another assumption, Again, I am not sure this makes a difference, but lets say the wheel is not attached to any device and it has a no load situation on the axle. For now lets say the eff of the wheel itself is 100%. I realize I have asked a lot and Thank You in advance for your time just to look at this question. Sincerely, Bobv Robert Vitale www.waterwheelfactory.com -----Original Message----- From: Martin.Leahy [mailto:[EMAIL PROTECTED] Sent: Tuesday, November 02, 2004 7:14 AM To: '[EMAIL PROTECTED]' Subject: RE: [microhydro] Newbie question: energy estimation from flow rate Most waterpower systems require that you concentrate most of the practical head (fall) between the entry (high) point and the exit back to the stream (low point). i.e. one is attempting to harness the potential energy of the water falling from high point to low point. [Harnessing the kinetic (speed) energy is a different and less used approach] Power available is then: Power (kW) = flow (m3/s) x head (m) x g (m/s^2) x overall efficiency where g is the acceleration due to gravity. or say power (kW) = flow (m3/s) x head (m) x 7 The units one buys and sells electricity are kWh (i.e. the number of kW times the hours of operation at that power level). Cost effective systems will usually have a 30-40% capacity factor (i.e. the power output in an average year would be nameplate power x hours in the year x 0.4). You need to measure the head, and the more (financial/time) risk you take the more confident you need to be about the accuracy of the head and flow you measure! Regards, Martin -----Original Message----- From: Mohammad Jahangir Khan [mailto:[EMAIL PROTECTED] Sent: 01 November 2004 14:08 To: [EMAIL PROTECTED] Subject: [microhydro] Newbie question: energy estimation from flow rate Hi Is it possible to measure the energy/power available from a free- flowing water stream ? The flow-rate is given in m3/s. Thanks. J. Khan 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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