Author Topic: Some solar energy topics and other related things.  (Read 9248 times)

Jon

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Some solar energy topics and other related things.
« on: June 21, 2010, 12:51:28 PM »
This guy invented an idea of how to make a solar tracker.  It uses a common drill (cordless I guess).  Thing is, it has good potential for solar power applications.    Also, I'm not sure if it's just a demonstartion model since I didnt see any light sensors, but it's understood it would need them.

Solar Tracker


Gabriel

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Re: Some solar energy topics and other related things.
« Reply #1 on: June 21, 2010, 03:29:10 PM »
Looks pretty cool. It will be neat to see it when it's finished. It looks like the solar panel is homemade too.



BackyardWorkshop

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Re: Some solar energy topics and other related things.
« Reply #2 on: July 02, 2010, 05:30:16 AM »
When I was buying my Parallax micro controller I saw that they have a DIY solar panel kit http://www.parallax.com/

Also the Harbor Freight 45 watt solar kit is on sale this weekend for $159! http://www.harborfreight.com/45-watt-solar-panel-kit-90599.html?utm_source=multi&utm_medium=email&utm_campaign=2610B

I think I'm going to get one :)
Check out my CNC projects (and more) at http://www.backyardworkshop.com

Gabriel

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Re: Some solar energy topics and other related things.
« Reply #3 on: July 02, 2010, 12:04:29 PM »
I actually just finished making a 50-60 watt one myself. I bought the solar cells off of eBay and soldered them together into a panel. I should have pictures up on my site before too long.

You can get the panels a lot cheaper that way, but it can be a lot of work to solder them together if they aren't already tabbed, as I have found out. It is the very definition of tedious.

It's pretty easy to get them already tabbed, they just cost a little more.

I was pricing the cells on eBay just a couple of days ago and found a batch that amounted to 1000 watts worth of cells for $622. They were already tabbed too.

Buying 1000 watts worth of panels on eBay costs $2750, so the cells are obviously a lot cheaper.



Last night I put together a way to get real time power usage from my electric meter by using an Arduino, photoresistor, and a laser light. It basically just counts the number of times the disk spins over a certain period and calculates the power usage from that. I still have a little bit of coding to do to get it to graph the data, but it is mostly finished. It's pretty fun.

The data should make it easier to figure out what I would need should I try to go completely off the grid.

Jon

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Re: Some solar energy topics and other related things.
« Reply #4 on: July 09, 2010, 10:20:57 PM »
Some nice stuff on the home page here about maximizing efficiency of a heliostat.  One other way to squeeze out some more power at low-efficiency angles is to make the mirror larger, but it also has some potential problems, for example for safety the target needs to have a backing sun shield probably, for safety, especially if multiple mirrors are being used.  Maby can squeeze out an effective daily efficiency of perhaps 5% to 10% more.  

[ update , 7-11-10 ] Ok, I meant efficiency of the system when the heliostat mirror is not directly in line with the Sun - this is when the rays strike the mirror "straight on",  but they are now at an angle, and like Gab. said there is less surface area of the mirror when the mirror is at an angle and it "gathers and reflects" less total light energy.  At these times, a slightly larger mirror can help the system.   Also, a reminder here that the Suns rays expand a bit after leavig the surface of the mirror.  This is because the Sun is not a point source of light at all, but is a fairly large "point" in the sky (half a degree big I think).
« Last Edit: July 11, 2010, 12:14:39 PM by Jon »


Jon

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Re: Some solar energy topics and other related things.
« Reply #5 on: July 11, 2010, 11:37:53 AM »
Here is a website that shows the current locations where the Sun and Moon are directly overhead on the Earths surface.
http://www.timeanddate.com/worldclock/sunearth.html
This site shows the max tilt to be 23.26 degrees (which might have to be used in the formula I show below, the commonly used value of 23.5 is like an average value).  It also shows the current solar latitude value which is good for solar projects.  I have a formula for this that seems to be very close and I'll try to post it here and then maby you can compare to any formula that you already have:

Current Solar/Sun Latitude =  Earths Current Angle = 23.45 sin (0.98630137  x  Day Since March 21 Equinox)

The reasoning behind this formula is based on that the Earth's yearly (365 days) tilt process seems to be sinusoidal in nature.  It tilts very vast at first and continues to slow down and practically stops (first day of summer or winter) and then the Earth tilt changes direction.  

The mathematical argument for the sin function is based on 0 to 360 linear values only.   Using a range of 0 to 365 (technically its near:  365.2422 - tropical year)  would result in a close value, but a closer value is had by converting or modifying 365 with a multiplying factor so that the result is converted to a range of 0 to 360 only.  Here is how this factor value us found:

       360/365 =  0.98630137  

An extra note about this value; you could say that if the Earths orbit around the Sun was exactly a circle (it practically is almost) that it goes around the sun at almost 1 degree a day.

Here is an article on "Earths Tilt":  http://en.wikipedia.org/wiki/Earths_axis
« Last Edit: July 19, 2010, 04:56:20 AM by Jon »

Jon

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Re: Some solar energy topics and other related things.
« Reply #6 on: July 12, 2010, 11:13:21 PM »
Using the above tilt value you can set up a system that needs tracking of the Sun.  The axis of the system will rotate at 15 degrees per hour and is perpendicular to the Sun through the day.  Basic formula (let me know if you think it is wrong, etc) is:

90 degrees - Your Fixed Latitude (Angle)

However due to the continual tilt of the Earth, your "effective latitude" with respect to the Sun or our orbit plane/solar plane must take account for this current tilt value.  I believe this is the maximum angle (elevation) of the Sun for that day:

90 degrees -  (Your Fixed Latitude Angle + Current Solar Latitude Angle)

So the Sun will then appear to rise in the east at 0 degrees elevation and rise up  to the above value at your local solar noon time.  I'm sure theres a bunch of advanced formulas etc about all this, but this is what I know so far and will have to update this as it goes I guess.


It also appears that the "solar latitude" value for the Earth can also be used to tell where the Sun will rise and set with respect to true east and west.
« Last Edit: July 13, 2010, 11:20:13 AM by Jon »

Jon

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Re: Some solar energy topics and other related things.
« Reply #7 on: July 13, 2010, 10:00:34 PM »
(continued)

As to why 90 degrees is used in the above equation, here is a simple example to verify its use.
At the equator on March 21, the Sun is directly overhead at solar local noon, and the Solar "latitude" is 0 degrees.
The angle of elevation from the horizon to the Sun (or between the horizon and the Sun) can only be 90 degrees,
like a right angle.  The rotating axis (like for a parabolic trough solar water heater) of a solar collector tracking would be parallel to the ground in this instance, hence at:

 90 degrees - the max angle of the sun for that day.

And for the example just discussed the angle would be 0 degrees with respect to the ground (inthe north direction).

As an extra note:  You dont have to track the sun exactly in both the horizontal and vertical directions with a trough system.  There could be some slight losses if you dont track it so great in the vertical direction, as one YouTuber told me.  I think to overcome any slight losses, just make the trough mirror/reflector larger where needed so that the entire collector (usually a pipe or vacuum tube type) receives light throughout the year.   This reduces the system complexity and cost, however it also reduces efficency somewhat since the mirror is technically not gathering all the light it could of if it were perpendicular to the Suns rays.
« Last Edit: July 14, 2010, 11:12:15 AM by Jon »

Jon

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Re: Some solar energy topics and other related things.
« Reply #8 on: August 05, 2010, 04:59:49 AM »
Here's a simple method I thought of to setup/aim the mirrors of a solar array for solar cooking:

Easy Method To Set A Mirror Into A Desired Position - Sphere And Socket Method


This is not a motorized or automatic array, but something cheap to use and experiment with.  Basically the spheres are to be glued into a fixed position hence a fixed focus of sunlight energy concentration.  The mirrors can be made moveable by any means necessisary/available, perhaps velcro strips, or some kind of setscrew scheme adjustments.  This would allow a new common focus location for all the mirrors of the array.

For each and every mirror of the array, simply drill the necessiary hole in the support board; hopefully its not too thick and if it is too thin, you can use strips of thicker wood as braces along the back of the support board.  Lots of ideas can be put into this one.


Can use the above to make something like:

New Solar Oven Cooker System With A Bottom Metal Heat Plate (Dual Purpose).wmv


This is good in an urban area where burning a fire is prohibited because of fire hazard and smoke problems, but can still use it anyplace.
« Last Edit: September 11, 2010, 10:44:10 AM by Jon »

Gabriel

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Re: Some solar energy topics and other related things.
« Reply #9 on: August 05, 2010, 10:14:33 AM »
Looks pretty cool.

I think that it might be particularly useful if someone wanted to "chain" together several smaller mirrors to be controlled with only two motors.

Jon

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Re: Some solar energy topics and other related things.
« Reply #10 on: August 06, 2010, 11:18:54 AM »
I guess, then the spheres would need to be able to rotate, probalby on some roller bars.  Probably 4 needed for each sphere I'm guessing - like an arcade "trackball" or something.  The main use for this array above was for experimentation and solar cooking, and it would be nice if a motorized one can be made, but only if its better/easier/cheaper than the existing methods (maby some kinds of bars or pipes connecting each mirror making them "ganged" together in unison).  The basic idea of the drawing was to make "fixed" mirrors that don't move, or atleast can be "fixed" to new targets manually.  The suupport board that the mirrors ("solar mirror array") are on will be the only thing that is to be moved (by hand or some other non motorized method) to keep the concentrated ray onto the receiver.  That is, the individual mirrors are not moved in relation to the support board.   I envisioned people using this only for (temporary) cooking (maby up to an hour or two), and maby some other type of heating.  I mean temporary here since it's not motorized.  If it were motorized then more things are possible, but that was not the original intent.  The original intent of the design was for something simple and cheap that just about anyone might consider.
« Last Edit: September 03, 2010, 12:05:49 PM by Jon »

Jon

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Re: Some solar energy topics and other related things.
« Reply #11 on: August 25, 2010, 01:23:13 PM »
This is a nice video I found on YouTube that is mostly about the basics of measuring solar energy, some of this I already figured out when I was thinking about solar air heating; basically that a square centimeter receives about 0.1W (a tenth of a watt)
in good sunlight conditions, and a soda can will produce about 5W of heat after some expected
losses, etc.

If the vid does not play then copy and past the link into YouTube.  It appears the vid. is allowed to be
embedded for the internet, otherwise, for YouTube,  watch?v=12Zj7Bux5Bs

Energy from the Sun


<object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/12Zj7Bux5Bs?fs=1&amp;hl=en_US"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/12Zj7Bux5Bs?fs=1&amp;hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>
« Last Edit: October 07, 2010, 04:40:28 PM by Jon »

Gabriel

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Re: Some solar energy topics and other related things.
« Reply #12 on: August 29, 2010, 05:43:44 AM »
That's a really informative video.

I was thinking about making a pyranometer so that I could try and log the output from the sun for my location, and a device like that would come in really handy when the time came to calibrate it.

Here's is a link to the DIY pyranometer I was looking at. http://www.pages.drexel.edu/~brooksdr/DRB_web_page/construction/pyranometer/pyranometer.htm 


Here's a link that shows a similar project. http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/
The link gives isolation data at various locations in the U.S. for various types of solar tracking machines and stationary solar collectors.

Pretty neat stuff

markV6

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Re: Some solar energy topics and other related things.
« Reply #13 on: October 07, 2010, 08:32:53 AM »
Hi,

Here is another interesting heliostat site: www.heliostaat.nl

It has the schematics included, i cannot find the software

Mark

Gabriel

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Re: Some solar energy topics and other related things.
« Reply #14 on: October 07, 2010, 09:57:10 AM »
Hello mark, and welcome to the forums!

I don't see the software either. Looks like he used some really nice hardware though.


Gabriel