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Questions regarding portable solar pumping in an agricultural setting.

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  • Questions regarding portable solar pumping in an agricultural setting.

    Hello all, I was wondering if I might pick your collective brains on the subject of solar pumping solutions.

    Now, I'm working on a project to provide a portable, renewably powered irrigation system for farmers in northern India as somewhat of a personal challenge. I chose the design route in university and as such know pretty much less than nothing about renewables apart from a few basics that I have picked up from MacKay's 'Sustainable Energy- Without The Hot Air'.

    The basic outline of the project calls for the unit to be:
    [LIST][*]Low cost (sub $1,500 per unit)[*]Portable (via Ox cart, so I would estimate sub 100Kg AUW)[*]Capable of irrigating 1Ha of land per day[/LIST]

    My back of the fag packet calculations have lead to a rough estimate that a 0.75kw pump, pumping continuously for an 8hr work day at 120l/min will produce a total discharge of around 57m^3/day or a total coverage of around 0.005m/Hectare. Now, even I know that this is unlikely as with array output losses due to mismatch and cable and diode losses and efficiency losses through the pump itsself. And this is without taking account of the significant start up surge the pump is likely to produce. But it is, after all, only a maximum upper estimate.

    To power this pump, if I am correct in thinking, I would require a minimum of an 0.85kW array to account for some of those losses, an inverter (if the chosen pump is AC) and a control unit and, most likely, some form of back up via battery to fill the gap on voltage losses.

    My issue with all this would be that I fail to see, with all this equipment, how exactly one could stick to the original criteria. Being that even a basic set-up is likely to be somewhat less than portable and somewhat more than the maximum $1,500 unit cost. Which is probably why, when looking at other submissions, the maths is very optimistic and the costing non-existant.

    So, I put it to yourselves, have I got my sums completely backward? Am I barking up the wrong tree? Should I look somewhere [I]other[/I] than solar for this particular application? Or should I consider other ways to utalise its strengths (I was thinking about using high pressure steam to run a pump and in turn use a small solar array to power a heating element, but with even a domestic kettle running at around 3kW I don't see that as particularly probable either)?

    Thank you.


  • #2
    I see no way of doing this. $1500 might get you 300 gallons a day depending on lift/head and pressure needed. But that is only 1/50 of the 15,000 gallons you want.



    • #3
      You are going to have to up that from $1500 to $60,000
      MSEE, PE


      • #4
        That was my thinking. For reference here is the original brief from Greenpeace.

        As noted in the OP most of the current submissions seem to be lacking any serious figures either financial or mathematical. Hence my reticence to fully believe some designer's claims ie. a sub $1000 per unit cost for 72m^3/day discharge on a 1.2kW array? Really? My quick costing brought that in at least $8000 and even then that probably wouldn't have produced an effective solution.

        As such, I'm now exploring non-PV solar solutions, Sterling Engines and the like...but the losses across various actions and processes are scaring me already (and these fora are not the place to discuss them).
        Last edited by EOT; 10-14-2013, 02:02 PM. Reason: Forgot my link.