Saturday, April 30, 2011

Thermal Camera Examples and Lessons Learned (so far)

I recently talked myself into buying a thermal imaging camera -- I've wanted to get one for quite a while, but the $5K+ prices just put them out of reach.  But, FLIR came out with the I series of entry level thermal cameras last year, and then dropped the price quite a bit recently -- it was too much -- I succumbed and bought the I7 model.  They are still not cheap -- the I3 with 60 by 60 resolution is $1200, and the I7 I bought at 120 by 120 resolution was $2000. 

The FLIR entry level thermal cameras
I've had the camera for about 2 months now, and have put together a page with some initial experiences, some hints on using these cameras, some example pictures that I thought were interesting, some lessons learned, and a "review" of the I7 camera and software -- all here...

The camera basically measure IR (heat) radiation from the objects you are taking the picture of.  The camera software uses the IR radiation levels and your estimate of the emissivity of the object to estimate the surface temperatures of the object.  The camera converts the temperatures into a colored image where each temperature maps to a color shade. 

The camera produces images like this:
Thermal image of Kristy the dog.
As one quick example...

My main reason for buying the camera was to be able to get an understanding of temperatures on the absorber and glazing of solar collectors with an eye toward making changes to the collector to improve heat output.  This is something that is hard to do with ordinary instruments as its really helpful to know what's going on all over the absorber surface, not just in a few points.  For my camera with 120 by 120 resolution its kind of like being able to place 14000 thermocouples on the absorber -- amazing!

This is an image of a backpass style solar air heating collector.

Backpass style solar air heating collector.
As you can see, it shows the surface temperatures of the full absorber from where the cool air enters in the upper left down the serpentine path through the internal baffles and out the lower right.
You can see immediately that there are places where the absorber is running much hotter -- these correspond to pockets of dead air where baffles are not working well.  In these areas, the absorber just heats up until it can lose most of its heat out the glazing, which makes the collector less efficient.
I don't know of any other way to get this kind of detialed picture of what's going on.

Anyway, there is quite a bit more at the link above -- have a look.

Gary April 30, 2011

Friday, April 29, 2011

Detailed Pictures of Grid Tied PV Array at Craters of the Moon National Monument

On a recent vacation trip we stopped at Craters of the Moon national monument.  The visitor center at Craters had a nicely done grid-tied solar electric array.  I thought that the array showed some nice construction detail, and took quite a few pictures. 

The pictures below  show a sampling of some of the construction details that I thought might be helpful to people building PV installations.  The link below goes to many more pictures showing construction detials.

I might add that Craters of the Moon has a lot more interesting things to look at than PV arrays, but I figure those things are covered in a lot of other places :)  The drive up from Twin Falls Idaho along US 93 and then Idaho 33 toward Craters of the Moon was exceptional.

Nice simple mount system using galvanized steel pipe.
Standard industrial fittings couple the rack pipes togehter.
While this array is fairly large (50 KW!), it is modular and similar to ones you might put on your house. 
Lots more pictures showing the details of the Craters PV Array construction...

The string inverter makes for simple wiring and is mounted right on the rack verticals.

Gary April 29, 2011

Thursday, April 28, 2011

Series of Articles on DIY LEDs

Backwoods Home Magazine is just finishing up a good 3 part series of articles on LEDs by Tim Thorstenson.
The articles provide a good understanding of LED basics and are easy to understand.

The articles might be of particular interest to those who want to experiment with building your own LED lights from components.

This is the link to part one of the three parts...

Gary April 28, 2011

Tuesday, April 19, 2011

Heat Transfer in a Solar Air Heating Collector Made with Gutter Downspouts

An interesting solar air heating collector design to come up recently is made from ordinary aluminum gutter downspouts.  The downspouts are laid out side by side to from the collector absorber.  The downspouts are all connected to air supply and return plenums run along the top and bottom of the collector.  Air is forced through the collector and picks up heat from the sun heated gutters.

This is a picture of a downspout collector from Scott's site...
Amoung the advantages of the downspout collector are that 1) there is no forced airflow against the glazing, which tends to reduce heat loss out the glazing, 2) the plenum and downspouts provide for an even distribution of air over the full absorber surface and minimizes hot spots with poor circulation, and 3) the heat transfer area from absorber to air (a bottleneck in many solar air heating collector) is good due to the large heat transfer surface area of the downspouts.

But, the last advantage of lots of surface area to transfer heat from downspouts to air is only true if the heat from the sun side of the downspout gets conducted around the sides and back to warm them up.  This test was done to see if that happens -- that is, is there really good heat transfer around the full circumference of the gutter section so that heat is transferred to the air by the full surface.

The not very ambitious test setup consists of 3 downspout tubes connected to an air supply plenum.  Air is supplied to the plenum by a small fan, and the temperatures of the front ant the back of the gutter tubes is measured with a thermal imaging camera (my new toy instrument).  Here is a picture of the setup.

The insulation panel on the back is to better simulate the actual collector environment -- it is quickly removed before taking the temperatures on the back side.

These are thermal images of the front and back while the collector is in operation.

Front of the collector

Back of the collector
Its pretty clear just from the images that quite a bit of heat does make its way around the sides and back, and while they run a bit cooler than the front, they are still quite a bit hotter than the airflow and that some heat transfer is taking place around the full periphery.  So, this seems like a plus for the downspout collector.

More details and analysis on the test of the downspout collector here...


Wednesday, April 13, 2011

A Little Testing on the Effect of Shadows on PV Array Output

There was a question on the Greenbuilding List the other day about whether shadows from a nearby power line would drop the power output form a PV array significantly.  I did a little bit of testing using my PV array and some pipes to simulate shadows, and thought the results were interesting enough to pass along.

My PV array is 10 modules and uses the Enphase micro inverters, so each panel has its own inverter, and the power output from each panel can be indepenently tracked.  So, I used pipes to make simulated wire shadows on some panels while using the output from the unshaded panels as a control.

PV array with 4 of the panels shaded.
Closeup of "wire" shading.
In a nutshell, its possible to get some pretty serious power drops when you use relatively lareg simulated wires that are pretty close to the panel (as in the picture just above), but when the wire diameters drop down to a bit over half an inch the effect (at least on my panels) becomes small.  As the distance from the panels to the wire increases, I believe the effect will become even smaller as the shadows appear to fill in with distance.

Here is the grand result showing power output form all of the panels for the two tests (big wires and small wires):

There is a lot more detail at the link below, with actual power drops for the eight different shading conditions I looked at.

All the details on PV array shading from power lines...

Another small shading investigation done earlier...


Sunday, April 10, 2011

Simple Stuff

I just saw a YouTube video on a nice, simple, efficient setup for washing the laundry by hand...

I really like nice simple solutions -- I think we tend to make things much more complicated than they need to be and end up being slaves to or labor saving junk.

So, here is a list of a few of my favorite simple ideas and projects.

Bubble Wrap Window Insulation...

Just spray a little water on the window, and apply bubble wrap.  Instant R1 added.

Electric Mattress Pad to Save Heating Fuel...

An electric mattress pad keeps you warm at night and allows you to turn the thermostat down further and still be very comfortable.  Simple and easy and saves a surprising amount of energy...

 Hippo Rollers...

 One of my all time favorite simple solutions!

 Judy of the Woods...

 I think Judy has if figured out.

 Eight Simple Projects that Cost $380 and Save $900 a year...

 You can spend $40K on a PV array and save 10,000 KWH a year, or you can spend $380 on projects like these and save 10,000 KWH a year.  Why do so many people choose the PV at 100 times the price for the same saving?

Got any simple projects/ideas you would like to add???

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