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Irrigation from solar power.

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Posted by manubrian on February 4, 2009, 6:15 pm
 
hi, I don't know if I have the right group for information on this
subject. Firstly may I point out that I am not at all technically
minded and any answers will have to take this into account!

I live in S W Turkey and help run a small market garden and plant
nursery. We are based in a small traditional Turkish Village and rent
a field with an area of about 6000 sq metres. The aim is to grow
vegetables that appeal to ex-pat English and other Europeans but that
are not readily available to buy locally. Our market research suggests
a strong demand with a premium price and a good scope to expand sales
beyond the immediate resort areas. Currently, all of our produce is
organically grown.

The problem is the water supply. The traditional method is to divert
water from irrigation canals and run this down the furrows. This is
wasteful because a lot of water evaporates and some areas become
flooded while others are dry. There is not enough water, so it is
rationed and can only be used on certain days of the week. This is
both inconvenient and impractical. It is also time-consuming; to cover
6000 sq metres takes about 8 hours of hard manual labour. It is also
impossible to plant seeds or small seedlings as these are just washed
away by this method.

I believe an irrigation system would address most of these problems
and think a solar powered system would be ideal; when the sun shines
the crops need water. At last we come to my question. What equipment
would I need to supply sufficient water via a drip system to my crops.
The field comes with a 30,000 litre capacity cistern fed by a natural
spring?

I also have the following supplementary queries;
1. Would it be possible to install a (variable) timer to govern fow
and what additional materials would I need?
2. Some crops need more water than others. Could I vary flow to
certain points?
3. How adaptable would the system be if i wanted to expand?
4. Would it be possible to connect to the grid and sell back surplus
electricity to the supplier?
5. Could I harness any surplus power to supplement my domestic reply?

Sorry about the long preamble but I hope it explains the problems we
have here with this issue. Hope someone has the time to help.

Brian.


Posted by Russ in San Diego on February 4, 2009, 10:16 pm
 

That's a huge question, very little of which can really be answered
here.

You need to figure out just how much water you will need to move.
Drip irrigation is an excellent way to go, but there will be
significant capital (for filters, hoses, emitters, timer, valves, pump
(s), solar panels, charge controller, and batteries) and labor expense
(to design and install the aforementioned) to set it up.

You should figure out how much water you will need per watering cycle,
and then see if you can build a tank that is sufficiently above ground
level that gravity can provide adequate pressure for the emitters.  I
would then install a pump that can fill the watering tank from the
cistern.  The pump, along with timer and valve, would be powered by
the solar PV system.  The pump capacity is determined by how big the
watering tank is, and how much time is available to fill it.  Ideally,
most of the pumping happens during the daytime, minimizing the amount
of battery capacity required.

I suspect you want the timer only to run the refill pump -- which
should incorporate a "tank full" cutoff sensor.  You might want to
make the dispensing valve manually operated, since you don't want to
over- or under-water your crop.

Or you could get rid of the watering tank concept and pump directly to
the drip irrigation system, but then you'd probably have to make the
pump and batteries bigger.

You should probably start by googling for "rural drip irrigation" or
some such.  I wouldn't be surprised if Israeli universities had a lot
of relevant information for you.  I'm just a city slicker electrical
engineer, and have no experience in these matters.  My ramblings above
are just musings about how I would approach the problem.

Once you know how much power you need, you could come back here and
try again.

Posted by Morris Dovey on February 4, 2009, 11:25 pm
 manubrian wrote:


At http://www.iedu.com/DeSoto/Projects/Stirling/Dyne.html  (photo at
bottom of page) you can see the original prototype of a directly solar
powered (non-electric) pump engine that's intended for exactly the
application you describe.

If that looks interesting to you, click on the "Up" link for a menu of
related pages.

HTH

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

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