Pedal Power and Micro Hydro

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Pedal Power and Micro Hydro

This is a quick summary of my talk and shop tour at the Farm Hack event Sunday April 29, 2012

Pedal Power
Pedal power is useful for off-grid and small scale applications.

our website and video:
Pedal Power Engineering
also check out:
Maya Pedal

Power output for humans
50 Watts (easy effort- can maintain for hours)
100 Watts (strenuous effort- can maintain for minutes up to 1 hour)
200-500 Watts (intense effort- can maintain for seconds up to 1 minute)
Helpful tips
flywheel helps with momentum (mass x radius x velocity squared) heavier and faster is better
chains are more efficient for low speeds (less than 1000rpm) but v-belts are easy and ubiquitous
humans pedal 50-100rpm
gearing is needed (grain grinding 90rpm, electric generators 1,000rpm, blenders 10,000rpm)
permanent magnet DC motors are also generators (like in a treadmill)
find cheap/free parts on craigslist/ebay or in dumpsters (old bikes, exercise equipment, etc)

Micro Hydro

Small and micro scale hydro power is the most cost effective (and best energy return) renewable energy source by an order of magnitude.

Helpful resources:
Rocky Hydro
Stream Engine
Build it Solar DIY Hydro Projects
Low Tech Magazine Boat Mills

Site survey:
measure head: elevation drop from top to bottom (of spring or stream)
measure flow rate in gallons per minute
potential power (Watts) = head(ft) x flow(gpm) / 10

Case study Full and By Farm:
Pre-existing spring fed water on farm
head height 100ft (elevation)
existing 2in pipe distance 1500ft
flow rate 5.5gpm (gallons per minute)
power output 75Watts
power output per month 53kWhr
water pipe was existing, hydro system cost $400

I will post more details on the Tools section of this site, and feel free to contact me for any more details, questions or help with your project: andy[at]

Dorn's picture

Thank you so much for your tour and posting this information - do you think that you might be able to start a tool wiki for the microhydro systems? I think it would be a good repository for folks starting out on projects - I think I mentioned that I think that micro hydro coupled with a gassifier(or whatever other power source is abundant on site) powered water pump(direct drive or electric) might be a way to even out power storage/generation needs in a farm application - ie. water stored in large farm cistern used to store excess power from generator with microhydro to generate on-demand power when needed. I am thinking about hill side storage ponds etc. which could also double for irrigation and animal watering storage. I would love to work up some numbers on a few case studies...

will do- I've dreamed about pump storage- it seems efficient and simple enough to fix and as you say multipurpose- nearly perfect!

Louis's picture

Hey Andy,
Is there a tutorial or bill of materials or pictures of that portable micro-hydro unit?