Eco - Practical Solar
Solar pumping solution for irrigation @ Mer Sober Galicia
For water source depth up to 30 Meters
Existing, tested and running:
Existing well 5 meter lift. Total lift 7.5 meters to storage tanks = 2 x 1000L. We installed a solenoid type pump able to withstand prolonged dry run with a small panel of just 12W.
Its a complete kit, just irrigation tubing and tanks to add.
Delivering >400L / day.
Pump kit (10m) just 450 Euros. Total cost < 600 Euros - No mains power - No running costs - Highly flexible, adaptable and movable.
Impatient? You can fast forward as follows:
About various pump types (Impeller, diaphragm, solenoid..)
Hydraulics can be boring and complicated. The important things to know are, water can't be compressed and the surface on connected systems will level regardless of distance.
If you need to level unsighted areas simply use a clear tube of required length, fill with water and the level at both ends will be the same, even if you have to go through a window etc, just make sure no air is in the tube.
Now the crunch part. Static pressure (water doesn't move) is the same regardless of pipe run!
A straight pipe down 10 meters will have a static pressure of 1Bar or 14.7Psi.
A 200 meter pipe with a fall of 10 meters will have 1Bar or 14.7 Psi.
That's static! The actual usable pressure and flow depend on the pipe diameter and length. Within high flow installs friction, diameter, bending etc. influence the usable (actual) water pressure and flow, not so in slow systems, they operate at very near static pressure.
So two tanks at 200 meter distance, same height, will fill equally, but it may take some time.
Next is the maximum lift or head of water. It is exactly that - head of water -. A pump designed to deliver 10 meter lift at sea level will pump water to 10 meter height, but there will be no flow!
It is important to look at delivery curves of various heights.
It is also important to look at the maximum lift required at any point in a given or planned system.
For submersible pumps the head of water is measured from the surface of the water source up.
Allow for seasonal change and potential dry run!
Pipe runs for slow flow at 1/2" (garden hose) should be calculated at about 1 meter lift per 100+ meter of pipe. In our install we can disregard this as we have buffer tanks.
Just the basics. Impeller pumps have, well an impeller, that turns in a chamber and pushes the water. To do this raw power is required. The higher the voltage the easier it is to generate this. Thus DC (direct current) photovoltaic powered pumps of this type are fairly limited or require large power and expensive panels. DC motors may wear out faster, always look for brushless. Look at MTBF Mean time between failure or expected life time in hours. 200 days at 10h = 2000h!
Diaphragm pumps have a vibrating surface in the chamber and flow valves thus pushing the water. For a low lift 1-4m these are usable as they can be photovoltaic powered but higher lifts come at a steep price, higher pressure requires higher power = expensive panels.
They are not forgiving to dry run and may choke on dirt.
Solenoid (piston) pumps. Very few moving parts, by generating electrical fields a piston is forced up pushing water. These systems do run slower the less power but still push the water to full height, just less of it. With a bit of electronics (boosters and capacitors) such pumps can start at very low power levels. You may see the typical pulsing water flow. These pumps can achieve amazing lifts and flow on a small solar PV panel and are highly efficient. Usually dry run capable.
Installations are either submersible or surface mount. On surface mount you have to deal with maximum suction and than maximum lift. Just standing them outside in the rain is also not one of the best ideas and forgetting winter maintenance (drain), a good frost may well split the whole pump. These are mainly mains and require inverters.
Submersible and specifically well pumps are design for remaining in the water, deep enough and no winter protection is needed. Submersing absorbs any sound, thus these are "silent" running.
A note on your normal well pump. These are multistage turbo pumps, fairly power hungry (1500W+). They are not very forgiving being run in start stop mode. It is advisable to install a larger expansion vessel so that the pump runs for at least 45 seconds before switching off, otherwise you may say good bye to your motor sooner than later. Dry running is also not a good idea.
Photovoltaic panel efficiency has improved but it is a slow process. Unfortunately quite some energy is required to produce them, that at present can't be helped.
Please be aware that these panels loose efficiency when hot. Cells placed less dense and on a white background absorb less heat. Full sunlight at lunch time really heats the panel(s) up and the efficiency goes down, a slight angle towards afternoon or morning sun gains maximum efficiency.
They are still expensive and if more power is required it is often better to use an array of equal and preferably standard cells as should one fail even under warranty its usually much cheaper and easier to replace. The kit we're using comes with white backed cells 12W module(s) about 20 x 50 cm - 8" x 13" - that all that is needed and the system works happily under overcast conditions, produces less water but then there is less demand in those conditions.
If you have lawns and / or large fields a sprinkler maybe unavoidable. High pressure >3Bar and a medium flow are required.
Evaporation is a big problem. Spray watering also may require chemicals as plants become more susceptible to fungus and mildew, watering with such systems during the day may also burn the leaves as the droplets form lenses.
Using high flow systems often lead to runoff, as the water cannot penetrate the ground fast enough.
Watering a poly tunnel or green house and small patches or areas for plants and fruit are easier to manage. Watering directly to the roots or very close by on the ground, single or clustered plants, avoids evaporation and also saturates the ground much easier using less water. There is no burning and less problems with fungus and mildew as there is no dampness near or on the leaves / fruits.
One way of measuring or guessing just how much water one requires is to count the amount of watering cans that are usually schlepped around (5-8L each), or measure the flow of your watering hose per minute and stop watch the total time it is used.
Well water is often very cold, ours is 6C, this can come a shock to plants.
Such irrigation systems are ideal for using simple gravity and as the flow is slow the water has time to penetrate the ground and not run off. Using buffer tanks also allows for refilling at low flows as well as for example during the day, whilst watering is done early morning and late evening. Ideal for using solar.
The existing main well, close to the house, requires a 5 meter lift. We have another existing well app. 200m from the house with a 3 meter lift. I'm undertaking to dig yet another in between but still about 70 m from the house with an expected lift of 3-4 meter.
For the existing green house / poly tunnels and the planned future extension we need water.
The existing well pump is power hungry, requires mains and the pressure / flow is much too high. We require water directly to the roots at low flow at a total of 3-500 litters per day.
We are lucky as we sit on high water table, but the below detailed solutions work for up to 25m. We are testing a solution with a special solenoid pump that delivers 55 meter head on 180 Watt but 240Volt. Lower and it becomes more expensive, there is a specialised US pump that does to 100m on a solar panel.
Digging trenches, putting in cable, installing sophisticated controls is simply not an option.
Going green or looking for alternative solutions is not cheap! The cheap DC pumps either don't have the life span and easy maintenance, they simply do not provide the lift or require large panels (50W+).
They are OK for water features, but do not expect them to last. 200 days at 8h = 1600h use per year. Please read the small print.
Looking at the pump selection:
As said above standard centrifugal pumps (the ones with the impeller) do not have the lift, durability or require large panels.
Diaphragm pumps are the next best choice. these are susceptible to dirt and most are very complicated to maintain, also requiring larger panels to run prolonged.
Solenoid pumps have few moving parts, with a current booster can run at low frequency and low power but still deliver the full lift! Some toys are readily available but I wanted a serious sustainable pumping solution with absolute minimum fuzz.
I found a supplier in Germany who has exactly what I wanted.
Solenoid (piston) well pumps with lifts of 10, 20 or 30 meter and a delivery rate between 300 - 800L day.
These are well pumps with a diameter of 6cm and are well engineered. The body is stainless steel, moving parts are just a solenoid driven piston, two springs and a valve.
The delivery quantity depends on: Pump type (10/20/30m), Sunlight, actual lift and distance.
As I write this part, early lunch time, we have the 10m pump installed, the pump is happily delivering 1L / min into our tank nbr.1, about 20 meters from the well.This tank is connected and gravity feeds a secondary tank a further 70 meters away. As this one is slightly lower a simple float valve (toilet replacement) stops
From both tanks irrigation is run, again gravity fed. In the poly tunnel single plants (tomatoes) and plant groups are gravity fed from small pipes from a central irrigation tube.
The tanks, by the way, come from swimming pool maintenance companies, they get their chemical delivered in these and are often happy to sell the empty ones rather than ship them back. I paid about 50Euros each. Clad in shade netting with climbers planted around, they will just disappear from sight.
For irrigation tubing and parts go to your local building merchant, they usually have all this as well and it's much, much cheaper than in DIY stores. 100Meter 1/2" black 27-30Euros.
Tip: Filling these with hot water it's easy to fit them and bend them tightly.
10m - max delivery height - complete system (panel, pump, filter, etc.) 450 Euro
20m - max delivery height - complete system (panels, pump, filter, etc.) 575 Euro
30m - max delivery height - complete system (panels, pump, filter, etc.) 700 Euro
Presently I have 1 10m kit available here in Galicia / Spain.
Other systems will be shipped directly from Germany, expect about 25 Euro shipping.
Tanks, additional tubing etc, should be source locally.
Yes, unfortunately this is not cheap, but once one starts calculating overall costs of complete systems it starts to look very attractive.
No mains wiring, highly flexible & independent, peak delivery exactly when required, no sudden demands on wells or other water sources & eco friendly.
For more information or if you wish to order such system please do not hesitate to contact us here at LifeInGalicia
Obviously if you stay in our beautifully restored house to rent (next door) or simply visit us and look over the garden and maybe pickup a nice plant from our nursery, you can see it for yourself.
Want to know more, want to see it virtually, want to stay – visit us at LifeinGalicia.com Correspondence from Mer Sober Galicia.
PS July/2012 I have now run one of the pumps for 3 full years, with minor maintenance (cleaning) and through summer and the harsh winter conditions - no problem.
PPS May I recommend you quickly glance at the article - Tourism Ribeira Sacra - Does it exist? -