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Hydropower is the name of power derived from the energy of falling water. Water falling 2 meters or more can be used to generate electricity.
   Under 2 m, costs increase, returns and efficiency diminish and in consequence, these sites are usually unused. There are a few ways of using these sites, hydram pumps, waterwheels, etc. For various reasons, these are rarely used.
      The PULSER PUMP is another way of using this power. Perhaps it suits your site and your intended use. If you are in doubt, look up air lift pumps. Airlift pumps are old technology but still in use today. Mostly for pumping water from very deep underground. Water supply utilities, and industries which use lots of water commonly use them. Similar physics governs the blowing of feed into farmers storage bins from trucks.
 The pulser pump works in broadly the same way. There is enormous benefit to be had from such a Simple system. Dig the hole, put in the pipes, divert part of  the stream through it and pump! It works automatically.
  I will describe only the pumping of water and the pumping of air for aeration in detail. However there are many possible uses. I will provide you with only a general idea of what to do in those cases.

                                                         INTRODUCTION
 

Pulser pumps use the power of falling water  directly to pump water or air.
The pulser pump is cheap to make and to install, it has no moving parts ,  it is reliable,  needs little maintenance and it  improves the water quality in the river or stream in which it operates.
 They can be used in flatter areas, with heads of half meter or more and flows as low as 250 liters per minute (lpm). We recommend 500 lpm minimum. 

 Warning
 Use a contractor and machines. I was stupidly risking my life. My brother Edward died (aged just 20) on Sunday 21st May 2000 in a far less risky situation. Please don't take any risks with your life.
 see working model figures
 

                               How it works
 

Stage one                                   Water falling in a waterfall carries air bubbles  below the surface in the next pool and they quickly return to thee
surface. In the pulser pump, the ''waterfall'' occurs in a vertical pipe and the water flowing into the pipe blocks the return and forces the bubbles deeper into the pipe. The bubbles continue down until they enter a chamber where they separate from the water.  The water returns to the surface via an exit pipe  and the air (under pressure due to the depth) collects in the chamber. Energy from the falling water is now stored in that air.
Stage two                                     The air from the chamber returns to the surface via a small diameter pipe. The pipe contained water some of which falls back through the air as it rises but much of  it  is carried to the top and  forced out of the pipe by the rising pressurized air.  As water and air leave the pipe at the top, they are replaced at the bottom and a dynamic equilibrium is set up. It is hard to believe that 2.5 meters of air pressure can be used to pump water 3 meters, 4 meters or even 8 meters higher! Fall back makes it all possible.
Imagine the air pushing a column of water 2 meters long all the way up the pipe. No problem there because the air column pressure is equal  to a column of water  2.5 meters high. Once it reaches the top and is expelled, water rushes in to the bottom to replace it and the cycle repeats itself. 
Stage two  (inclined pipes)       The pipe taking the air away does not need to go straight up. If it rises at an incline, it  works too.  This can mean a shorter simpler all underground  system. In this case, the air blowing in the pipes makes waves in the water in the pipes. If the wave is high enough, it blocks the pipe and travels rapidly through it. It isn't as efficient as going vertically, it needs larger bore pipes but if it delivers enough water for your needs, then why not?

HIDDEN BONUS!!!!!!
 This type of pump acts as a water treatment plant in the river itself! This is a very useful aspect. Can anybody quantify its worth to the environment?      HERE is how it works:
As the stream water passes down the pipe mixed with the tiny air bubbles, gas exchange takes place under ideal conditions. The  bubbles are tiny, the water is turbulent and the pressure is increased. Not only is the water well oxygenated under these conditions, also volatile nitrogen and sulfur compounds transfer to the air bubbles. Therefore the river becomes oxygenated and cleaner and fresher!   A better life for fish and other freshwater animals.  The calm well oxygenated water at the exit will be a refuge for water creatures during pollution events which typically reduce the oxygen levels.
 

You can pump :
Liters per minute                    Head  X  lpm at dam ÷ vertical height  X  0.1
liters per hour                         Head  X  lpm at dam ÷ vertical height  X  6
liters per day                           Head  X  lpm at dam ÷ vertical height  X  144

     I have done the figures in this way because although the pump works all day, if you want to use the water rapidly at certain times, then you must have enough storage capacity.

WORKING MODEL     Approx. Flow 260 liters per minute of water , head 0.5 m, going 2.5m deep and pulsing to 3.6 m gave 4 liters per minute. The same setup gave 1.5 lpm at 5 meters high. This was with a split process pump using 10 cm (4 inch) pipes for the stream water and using 19 mm (3/4 in)  for the pulsed water delivery. The efficiency decreases like this as one pumps higher. On the other hand, 2 stages to 7 meters will give about 2 liters per minute with  the same setup. Going deeper also increases the efficiency. Perhaps you have an abandoned well that you can use?  Less pipes are used in that situation and the well will not be filled in.  The working model in the example has just entered its second decade! It is in the hole in the Scary picture.  Apart from cleaning the sieve occasionally, there has been no maintenance. If you can dig deeper, you should get a similar efficiency at a similar height/dept ratio.
Once again, I recommend a  larger flow than this, and the use of 15 cm plastic pipes or bigger.
 

          MEASURING THE FLOW
1    Chose a fairly straight part of the stream where the cross section is approximately rectangular.
2    Place 2 poles in the stream  2, 3, or 4 meters apart.
3    Time a piece of wood floating down the middle between two poles. Repeat twice and divide the total
      seconds by three.   (Seconds)
4    Formula       depth (cm)  X   width (cm)   X distance between the poles (meters) X 4.5 ÷ seconds
                            This  will give you the flow in liters per minute

          MEASURE THE HEAD
  Head refers to the distance that the water will fall from the surface of the water in front of the dam to the surface of the water behind the dam .   You should measure this distance with a spirit level or a water level.  You can simply siphon water through a garden hose over the dam.  Once the water  flows through the hose, simply raise the end until the water no longer flows.  Then measure the distance from here to the surface of the water under the dam. The distance should be 50 cm or more.
  If you are making the dam from scratch, then you should get advice from fisheries people,  (and someone with engineering experience if it is more than 0.5 m high).
  Remember,  these things should pay for themselves with their work done.      Home Page
 

                                          YOUR SITE  ................  WHAT IS IT WORTH?

We will assume that you use the pulser pump throughout the year.. (My figures, below,  are calculated from  figures in an edition of  Scientific America  which was all about energy efficiency).

What is it worth?   I will give the value per year in kWh of electricity replaced, in coal saved and in savings in production of carbon dioxide. If you wish to include the environmental benefit of oxygenating the river, it is roughly equal to the figures for air pumping.  Of course, you get no economic benefit from this. It is,  if you like, your   gift to the environment. In London, the Thames river is oxygenated  with big electric air pumps to produce this same effect.

                                          YOUR SITE       POTENTIAL SAVINGS PER ANUM
                                                        Pumping water

                     kW of electricity saved per year      Head X  liters per minute ÷ 2.28

                     kilograms of coal saved per year      Head X  liters per minute ÷ 3.72
                     CO2 reduced by        kg per year     Head  X liters per minute  ÷ 1.79

                                                        Pumping air

                    kW of electricity saved per year       Head X  liters per minute ÷ 0.76
                    Kilograms of coal saved per year      Head X liters per minute  ÷ 1.24
                    CO2  reduced by        kg per year     Head   X liters per minute  ÷ 0.55
 

Below is an overview of several ways of setting up the system. (Not to scale).  Use it to estimate material costs.    It should give you a rough idea of how much pipe you will need to set up the system in one of the different ways. I recommend No.3 (for lots of reasons!), No.2 is the simplest, but the pipes to the user are generally bigger (more expensive),  No.1 may need guy wires to hold up the pipes, cost that in, and if the head is more than 1.5 meters, No 4,  a hydram or a low head hydroelectricity setup may be an option for you. Be sure that they will be  much more expensive to build, but that they definite options at 1.5m or more.
 

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