4 ms·

To borrow a phrase from Sheldon Brown, "As always, Bill Mollison has the answer." :) (for those unfamiliar with what I affectionately call the "Perma-cult": ht

To borrow a phrase from Sheldon Brown, "As always, Bill Mollison has the answer." :) (for those unfamiliar with what I affectionately call the "Perma-cult": https://en.wikipedia.org/wiki/Bill_Mollison https://en.wikipedia.org/wiki/Bill_Mollison) >So, it seems as though hydropower is not as clean as we once thought. But that’s isn’t a good reason to be ripping out dams. Hydropower generation often replaces much dirtier sources of energy, such as coal and even natural gas. In addition, dams provide us a wide range of public benefits such as flood control, recreation, and water management. It sounds like the Permaculture strategy of disfavoring singular large dams (huge concrete construction projects) and favoring smaller "farm dams" (cheap earthen construction) is the way to go. The smaller scale means more surface area:volume, increasing the equilibrium oxygen level in the water and reducing methanogenesis. Also, the typical Permaculture dam construction practice is to scrape off and conserve all the topsoil from the inside of the dam. This should further reduce methane production (which also represents squandered biomass, ie stored carbon). This technique is practical on the scale of a farm dam, but totally impractical for a huge reservoir. Farm dams have cost advantages in flood control and water management over monolithic dam projects, since they're near to the big consumers of water (farms). So the largest diversion canals and tunnels never need to be built. Simple gravity-fed water run through plastic pipes serves for irrigation purposes, so it improves on-farm water security. >groundwater storage may be a ‘cleaner’ alternative. Groundwater recharge basins are regularly maintained to have less organic matter at the bottom, since it can clog the percolation of water into groundwater aquifers beneath. In addition, recharge basins are shallower than man-made reservoirs and periodically become empty during dry periods when less water is available to recharge groundwater. This periodic drying out helps keep soils aerated, whereas man-made reservoirs can stay inundated with water for longer periods of time. I wonder how "groundwater recharge basins" differ from swales (long on-contour ditches)? They also intercept large quantities of runoff and divert it to recharging groundwater. They also require minimal earth movement, since it's a small surface feature compared to farm dams. Swales can also feed into dams, dramatically increasing their total catchment and infiltration capacity (since before the dam overflows, it floods and soaks the length of the swale). https://www.youtube.com/watch?v=E79C9tdcgEA https://www.youtube.com/watch?v=E79C9tdcgEA http://permaculturenews.org/category/earthworks-earth-resources/dams/ http://permaculturenews.org/category/earthworks-earth-resour...

internaut 10y ago
Small hydroelectric is extremely efficient. You can get efficiencies of above 80%. In larger installations 90% or more. It's expensive but beats the shite out of solar and wind over time. You can also, if you have an application for physical energy, roughly double the output. In addition almost all energy storage capacity for the grid is pumped storage from hydroelectric stations. I think it is massively overlooked merely because most people are interesting in scaling and these people overlook the fact that A: most things do not scale and B: long term maintenance matters. You can run a hydro plant with next to no maintenance for 100 years. I can't think of anything close to it and they can easily be fixed or repaired. It annoys me that micro and small hydro aren't talked about more.
- nkurz 10y ago
  You can get efficiencies of above 80%. In larger installations 90% or more. You can also, if you have an application for physical energy, roughly double the output. Could you explain the apparent contradiction? How are you calculating a 90% efficiency such that it's possible to get another 90% of "physical" energy?
  - internaut 10y ago
    Sure. With a hydroelectric turbine you can produce electrical power (by black magic as far as I'm concerned) or mechanical power. There is a terrific documentary called Ben's Mill on such a mechanical application here: https://www.youtube.com/watch?v=l2KJbRHO76s https://www.youtube.com/watch?v=l2KJbRHO76s That will explain visually how mechanical power can be coached into performing useful work. It's also worth watching just to see the cows reaction to their new water vessel at the end, they are like animals out of Disneyland. Mechanical power when converted to electrical power undergoes a drop in performance (similar to other power conversions, something is lost). There is a fascinating article here on the subject, I quote: "The hydro power installations in use today are actually less efficient than those of earlier centuries" "Direct hydropower is at least twice as economically viable as a hydroelectric operation with the same rate of energy production." http://www.lowtechmagazine.com/2013/08/direct-hydropower.html http://www.lowtechmagazine.com/2013/08/direct-hydropower.htm... Also take a look at this: http://www.lowtechmagazine.com/2013/09/power-from-the-tap-water-motors.html http://www.lowtechmagazine.com/2013/09/power-from-the-tap-wa... That is hacking if I ever saw it! I intend to construct a micro hydroelectric plant myself, so ask away if you've any questions. I love the idea of marrying up old school technology with modern technology. I also have a terrific idea for lighting using heliostats, which combines tech literally thousands of years old with the latest in machine learning.

internaut 10y ago

Small hydroelectric is extremely efficient. You can get efficiencies of above 80%. In larger installations 90% or more. It's expensive but beats the shite out of solar and wind over time. You can also, if you have an application for physical energy, roughly double the output. In addition almost all energy storage capacity for the grid is pumped storage from hydroelectric stations. I think it is massively overlooked merely because most people are interesting in scaling and these people overlook the fact that A: most things do not scale and B: long term maintenance matters. You can run a hydro plant with next to no maintenance for 100 years. I can't think of anything close to it and they can easily be fixed or repaired. It annoys me that micro and small hydro aren't talked about more.

nkurz 10y ago
You can get efficiencies of above 80%. In larger installations 90% or more. You can also, if you have an application for physical energy, roughly double the output. Could you explain the apparent contradiction? How are you calculating a 90% efficiency such that it's possible to get another 90% of "physical" energy?
- internaut 10y ago
  Sure. With a hydroelectric turbine you can produce electrical power (by black magic as far as I'm concerned) or mechanical power. There is a terrific documentary called Ben's Mill on such a mechanical application here: https://www.youtube.com/watch?v=l2KJbRHO76s https://www.youtube.com/watch?v=l2KJbRHO76s That will explain visually how mechanical power can be coached into performing useful work. It's also worth watching just to see the cows reaction to their new water vessel at the end, they are like animals out of Disneyland. Mechanical power when converted to electrical power undergoes a drop in performance (similar to other power conversions, something is lost). There is a fascinating article here on the subject, I quote: "The hydro power installations in use today are actually less efficient than those of earlier centuries" "Direct hydropower is at least twice as economically viable as a hydroelectric operation with the same rate of energy production." http://www.lowtechmagazine.com/2013/08/direct-hydropower.html http://www.lowtechmagazine.com/2013/08/direct-hydropower.htm... Also take a look at this: http://www.lowtechmagazine.com/2013/09/power-from-the-tap-water-motors.html http://www.lowtechmagazine.com/2013/09/power-from-the-tap-wa... That is hacking if I ever saw it! I intend to construct a micro hydroelectric plant myself, so ask away if you've any questions. I love the idea of marrying up old school technology with modern technology. I also have a terrific idea for lighting using heliostats, which combines tech literally thousands of years old with the latest in machine learning.