Wednesday, April 20, 2011

POWER TO THE PEOPLE!

It has arrived:  everything, panels, pumps, tools.  Needed: some intern/volunteer/local pay scale  expertise to team up with our rural community.


This apparatus will work so she doesn't have to work so hard or walk so far.  Solar coming soon to a mountain zone near you!


The apparatus will have a component that can charge other items as well.  We plan to ship at the end of the summer, si Dieu vle.





















































PHOTOS:





One of the glorious huge solar panels to be shipped to Haiti;

Bos Eric gathering data;

the pyrroheliometer, gathering sunlight;

one of the two pumps that will go the distance.
















APRIL 18, 2011 - Eric writes:


I recorded voltage produced by the solar panel and insolation (energy in sunlight) while the restricting valve increased pressure on the pump, simulating various heights. I also should have recorded current and voltage at the pump (on the output side of the controller); maybe next time. The attached graphs show the values for a 15 minute period. As load increases, voltage drops down to the 24 volts set by the controller. I suspect a 180 watt panel would still have a voltage above 24 V, where this 150 W panel can't maintain a higher voltage.

The voltage graph has a text box showing pressure values, and volume output measured by the old-fashioned bucket and watch method (no electronics!). At 80 psi, volume is still above the rated 1.4 gallons per minute. At 100 psi, the volume is only about half the rated output, meaning the pump has slowed down (but not stopped!). I tested it to 110 psi (where the hose bulges enough to show we need higher quality materials) in a later data set but didn't measure volume. The equivalent heights in feet are:
psi ft H2O
10 22
40 90
80 180
100 225
110 247

The pyrheliometer measured wide changes in solar energy, corresponding to clouds and people passing by and shading it. At one point (around 850 seconds into the test) I asked some visitors to block the sensor with their hands, which reduced insolation to zero (no surprise). In space, the sun provides about 1000 watts per square meter; air is not as transparent as we think, so at Earth's surface it is typically 750-800 watts/m2. Most of our measurements were between 200 and 600 W/m2. A few were over 1000, probably because extra light was reflected off something shiny into the sensor.

David was concerned enough about wind loading to ask me to tie the tripod legs to the cement blocks, which I did. This helped keep it upright in today's earthquake, as well as wind. I calculated the pressure and force of various wind speeds on the panel, and the moment, or tendency to tip over. A Sharp panel is rated at 50 pounds per square foot, which a 140 mile-per-hour hurricane just reaches. I suspect the bolts have a safe limit around 300 pounds, or a 70 mph wind speed. To keep the tripod from tipping over, a ton of weight is needed on the upwind leg at 140 mph. If 70 mph is taken as a reasonable maximum with the tripod upright, 500 pounds weight per leg is needed; this can be done with well-made footings covered with stones or packed dirt. If the wind is over 70 mph, they should fold the tripod and lay it flat.

-Eric

****************
http://wiki.contesting.com/index.php/Wind_load_calculations
For sustained wind speed: Force = A × P × Cd A = projected area of the item P = wind pressure (lb/ft^2) = .00256 x V^2 (V= wind speed in mi/hr) Cd = Drag coefficient = 2.0 for flat plates. For a long cylinder, Cd = 1.2.
A, ft2 12 height 11
Cd 2 base 6.5

speed P F moment, lb-ft anchor weight, lb
10 0.256 6 68 10
20 1.024 25 270 42
30 2.304 55 608 94
40 4.096 98 1081 166
50 6.400 154 1690 260
60 9.216 221 2433 374
70 12.544 301 3312 509
80 16.384 393 4325 665
90 20.736 498 5474 842
100 25.600 614 6758 1040
110 30.976 743 8178 1258
120 36.864 885 9732 1497
130 43.264 1038 11422 1757
140 50.176 1204 13246 2038

APRIL 20, 2011- Notes from Bos Eric


I measured voltage at the panel output and at the pump input, and current flowing through the pump (graphs attached) with pressures from 0 to 120 psi. There is still water being pumped at 120 psi (264 feet rise) but not a useful amount. Voltage X current = power in watts. The panel produced up to 120 watts (vs. its rated 150 watts); some loss could be from clouds, but David Coale had said it might have a small defect, which would account for some or all the 30 watt difference. The graphs look funny at 80 psi, with the pump consuming more power than the panel put out; this is because of a 5 minute time difference between the two voltage measurements; a cloud covered the sun during the panel voltage measurement. The same happened measuring no-load "off" (open circuit) voltage, which was 41 volts before the test and 38 volts afterward. After this test, I disassembled everything and brought it home. All in all, I think we tested it well enough to be confident it will do the job.

Randy asked about shipping weights. Each system will ship in 2 boxes of 40 - 50 lbs each: the panel in one, and everything else (except pipe) in the other. Here are the requirements for buying EMT pipe locally:
3 each 1 1/2 inch (actually 44.2 mm diameter) EMT, 10 feet (3.05 meters) long
2 each 1 inch (29.6 mm diameter) EMT, 10 feet long (cut into 5 foot lengths)
6 each 3/4 inch (23.4 mm) EMT, 10 feet long (cut into 7 and 3 foot lengths)

If the panel does not have to be on a tripod, but can be lower to the ground, I have a design for a simpler 4-leg A-frame structure to hold it. This would use 2 pieces 1 1/2 inch EMT, 1 piece 1 inch and 2 pieces 3/4 inch.




April 20, 2011: Randy Writes
You can see the light blue painted fasteners Eric made at the Tech Shop especially for the tripod. I tried to insert a close up photo of them in this blog, and it started throwing all other photos out. But: these are original, home-made, hand-made and...pretty neat!

So one non-technical task remains: All this sophistication, and all this technology and still a problem. How to ship these to Haiti, efficiently? Anyone got room in their private plane or...?
Please send your ideas and contributions to the Cause at http://www.causes.com/causes/529435
In God we trust...and hope! Thanks!

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