Wednesday, May 28, 2014

Using Portable Solar Panels to Create a Needed Product

Crop Coefficients - Paso Panel


Using the Paso Panel to quickly measure the canopy shaded area and 
estimate vineyard irrigation crop coefficients

Introduction
The Paso Panel is a simple device which is used to measure the midday canopy shaded area of
 trellised grapevines. This measurement is of interest because it can be used to calculate the irrigation
crop coefficient (Kc). The midday canopy shaded area can also be useful as a quick non-destructive measure
 of general vine vegetative growth, for example in evaluating the relative growth due to different fertilizer
 treatments or rootstocks. 
Paso Panel in field

Operation
The theory behind the operation of the
Paso Panel is that the electrica
l current produced by the solar panel is
proportional to the amount of direct 
sunlight striking the panel; thus, 
as the solar panel surface area is
increasingly shaded by the vine
leaf canopy, it produces proportionally 
less current.
Powerfilm chart
There are several important requirements for using the Paso Panel correctly:
1. The measurements can only be taken with clear sky conditions. Clouds can be present elsewhere
 in the sky, but not directly between the solar panel and the sun; any obstructions of the direct sunshine
 to the solar panel will lead to erratic readings and significant errors. Note that airline contrails disrupt the 
sunlight in the same way that clouds do.

2. Measurements should only be taken near solar noon; in California, solar noon in the summer occurs at approximately 1:00 pm (the shift in time from noon is due to Daylight Savings Time). It is suggested to only

 take measurements between 12:30 and 1:30. East-west oriented rows will be less affected by changes
 in the shaded area due to straying outside these time constraints as compared to north-south oriented rows.

3. The device needs to be held uniformly level, and the solar panel surface needs to be kept free of dust

 and debris.

4. Position the panel as close as possible to the underside of the canopy; the farther away the canopy is

 from the panel, the greater the possible error.

5. Any inadvertent shading of the panel needs to be avoided, such as that caused by the shadow

 of the person operating the panel. Orient the panel to avoid any such shading.

6. The switch which completes the electrical circuit should only be engaged very briefly 

(about 1 second per reading). This switch short-circuits the solar panel; if it is engaged for excessively
 long periods in bright sun, the solar panel wiring will burn out, as the solar panel was not designed to be
 short-circuited like this. Please heed this warning to avoid having to buy an expensive replacemen
solar panel.

7. Under windy conditions, the canopy shaded area will change somewhat as shoots and leaves move

 around. This will cause the current readout on the digital multi-meter to fluctuate accordingly.

Videos

Construction
The Paso Panel consists of three main components:
1. A homemade frame with carrying handles

2. A PowerFilm™ brand solar panel

3. A common digital multi-meter
There are many possible ways to construct a device similar to the Paso Panel; my current design made
 the best use of my available materials. Your materials, tools and construction skills may make a different
 design more practical. Photographs of the device under construction are available below in the "Downloads" 
section.
The lightweight frame is made from common extruded aluminum available at most hardware stores.
For the large sizedPaso Panel, the overall length is 8 feet (2.4 m). The frame is 1 foot (0.3 m) wide for all versions.
The device  can be made in different sizes, to fit different canopies and row spacings; in the photograph below the large sized  device is on the left, while a smaller sized device for narrow rows is on the right. 
The two handles are oriented to
 place the device at a comfortable height directly underneath the canopy when held by the user.  The frame also incorporates a bubble level, to help the operator ensure that the device is held uniformly level for all readings.
Different sized panels


The rollable solar panel I used is the PowerFilm™ brand, model number R15-1200 for the larger sized device.
 The more recent versions of the PowerFilm™ rollable solar panels have slightly different dimensions than the
 versions I used when developing the original Paso Panel; your design will therefore have to be adjusted
 accordingly based on which panel you use. For the most current information on these panels, see the
 manufacturer’s website here.
The digital multi-meter is a commonly available instrument; it is important that the device have the ability to
 read electrical current of sufficient range. I use a model rated up to 10 amps. The simple wiring diagram of 
the device is shown below. The two output wires from the solar panel are connected directly to the digital
 multi-meter, with a momentary pushbutton switch that completes the circuit only when the switch is depressed. 
This switch is located in the rear carrying handle. I use a switch from Napa Auto Parts,
 part number ECH STB6301
Paso panel diagram

Wiring diagram. The digital multi-meter is configured according to the manufacturer's instructions to read 
electrical current (10 amps in this example). If you set up your multi-meter incorrectly,
 you can easily burn it out.

Downloads:

Field measurement protocol
Step 1: Take a “Full Sun” reading
Hold the Paso Panel with the same orientation and at the same height as will be used when taking the 
shaded area readings in the vineyard. Press the switch momentarily and view the electrical current value
 on the screen of the multi-meter. Record this value.
Step 2: Take the “Shaded” readings
Immediately after recording the “Full Sun” value, begin taking the “Shaded” readings. Hold the panel level and perpendicular to the vine row, directly beneath the leaf canopy, and press the switch to view the electrical
 current value on the screen of the multi-meter. Take as many readings as necessary to accurately characterize
 the area of interest. These readings should be done quickly over a period of only a few minutes; if your needs 
require readings over a longer time period, break the measurement into separate short sequences, each with its 
own separate “Full Sun” reading preceding the corresponding “Shaded” readings. It is very important to do this,
 because the “Full Sun” reading is used as a reference value in the calculations, and the magnitude of the 
“Full Sun” reading will change throughout the day.
To facilitate rapid readings when working alone, use a digital voice recorder with clip-on microphone to record 
all readings verbally; after finishing the field measurements, play back the recordings while
seated at a computer and type the values directly into the spreadsheet which will do the calculations.

Calculations
The calculations are most easily explained in several steps. In practice, the computer spreadsheet listed
 above will handle all of the calculations.
1. Determine the shaded percentage of the solar panel
  • Shaded percentage of solar panel = [1 – (Shaded reading/Full Sun reading)] * 100%
  • (Note that the “Shaded” reading above is the average of all shaded readings for the plot)
2. Determine the shaded percentage of the field
  • Shaded percentage of field = Shaded percentage of panel * (Panel length/Row spacing)
3. Calculate the crop coefficient
  • Kc = (0.017 * Shaded percentage of field) – 0.008

Example calculation
Assume that the “Full Sun” reading was 1.7 Amps, and that the ten “Shaded” readings were 
1.0, 1.1, 1.1, 1.2, 1.0, 0.9, 0.8, 1.0, 1.1, and 0.9 Amps. The solar panel length is 5.75 ft, and the row
 spacing is 10 ft. What is the Kc value?
Step 1:
  • Average of the ten shade readings = 1.01 Amps
  • Shaded percentage of the solar panel = [1 – (1.01 Amps / 1.7 Amps)] * 100%
  • Therefore, shaded percentage of the solar panel = 41%

Step 2:
  • Shaded percentage of field = 41% * (5.75 / 10)
  • Shaded percentage of field = 23.6%

Step 3:
  • Kc = 0.017 * 23.6% - 0.008
  • Kc = 0.39
An important note when attempting to measure crop coefficients in the field using this method:
By definition the crop coefficient value represents the relative water use of a crop which 
is fully supplied with water. If measurements of the midday canopy shaded area are
 taken in a vineyard
 which is not fully supplied with water, then the shaded area will likely be smaller than it would 
otherwise be, and the calculated crop coefficient value will likewise be smaller. This discrepancy
 can be reduced by taking measurements during periods when the leaf canopy has reached ful
l size and while vine water stress is minimal; in many winegrape vineyards this occurs in the
 late spring 
around the period of bloom and fruit set. Later measurements after deficit irrigation regimes have
 been applied may lead to different values which are less representative of the true crop 
coefficient value for that vineyard. 
For further information on the theory of using canopy shaded area for estimating
 the crop coefficient, see the following journal article, which is available online at this link
Williams, L.E. and J.E. Ayars. 2005. Grapevine water use and the crop coefficient are
 linear functions 
of the shaded area measured beneath the canopy. Agricultural and
 Forest Meteorology, 132 (3-4)
 p. 201-211

To simplify information, trade names of products and/or company names may have been used. No endorsement of named
 products and/or companies is intended, nor is criticism implied of similar products and/or companies which are not mentioned.

Monday, May 5, 2014

Personal Portable Solar Power...Smart, simple & Cool!
















  1. Sustainability:maintaining ecological balance: exploiting natural resources without destroying the ecological balance of an area. 
  2. Sunlight: also called sunshine,  solar radiation that is visible at the Earth’s surface. The amount of sunlight is dependent on the extent of the daytime cloud cover. Some places on the Earth receive more than 4,000 hours per year of sunlight (more than 90 percent of the maximum possible), as in the Sahara; others receive less than 2,000 hours, as in regions of frequent storminess, such as Scotland and Iceland. Over much of the middle-latitude region of the world, the amount of sunlight varies regularly as the day progresses, owing to greater cloud cover in the early morning and during the late afternoon.


  Solar energy is renewable, environmentally friendly and, by itself, free. The one drawback of course is that it requires modern technology to convert the sun’s energy into something we can use, and the upside is that no fossil fuels are needed to create a sustainable source of electricity when it comes to solar power
  
  Going off the grid, growing your own food, recycling, up-cycling, re-purposing, alternate energy, going green, coop gardens, buying local, farmer's markets, water collecting, and so much more is starting to finally take a hold of our cities, towns and communities, and right in the middle of all that is portable solar power! The idea of using the power of the sun to create a sustainable source for electricity leaves me awe struck every time. Just the thought of how far we have come and far we can go with creating an affordable, viable way of lighting our homes & schools, charging our technology & cars and so much more endless possibilities with free energy from sunlight should be exciting to everyone. 

  So the bottom line to get started is this: We need solar panels to harness the power of the sun, which brings into light the different types of portable solar options you have to choose from. A lot of the misconception is that solar panels are these huge cumbersome things that go on your roof top only, not the case! All you need to do is start with portable personal solar charging kits, so light they fit in your backpack, motorcycle tail-bag, panniers or bike basket. Starting small is a simple step in the right direction, outfitting yourself with a portable solar charger is great for things like your smart phone, MP3 player, GPS, tablets, photography camera batteries, laptops etc. You can purchase all different sizes that will charge your phone to a fridge. 

Brands such as PowerFilm, and Global Solar make sizes that weigh less than 1 Lb. and can fold up into your backpack. Solarland and Wagan make larger ones that can sit outside your tent, trailer, cabin or house and light your camp lights, charge your GPS, phone, and give you some tunes or your kindle for a little light reading. 






Solarland pictured above and Global Solar on the tents are 2 ways of setting up your larger solar sized options. 





This is an example of a PowerFilm in use on a camping trip to charge up the phone while having coffee. It folds up to about the size a magazine. 





PowerFilm on a backpack to charge
up your device while exploring. 


And if you really want to do some 
major Solar Charging then go for the big
power with a California PC Wolf Pack



  
PowerFilm charging while riding.











So all in all find the right size for your needs & activity.
Whether it's lounging in the sun in the back yard & listening
to tunes, taking it with you to the beach, using it for
camping creature comforts or at a house, cabin or base camp,
there is a size just right for you!

Learn more at www.CaliforiaPC.com  we are ready to help
you pick out just the right one!

1-877-487-1213 or orderinfo@CaliforniaPC.com for inquiries.