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

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

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

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...

Gary

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...

Gary

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???

Gary

Earthbag Construction

I added a new (small) section on Earthbag home construction here...

This was prompted by seeing a TV program on the home of Kelly and Rosanna Hart in Colorado.  Its an earthbag house that they constructed themselves over a three year period.  The house is beautifully done with with each room hand crafted for its purpose.

The home uses a lightweight volcanic rock for the bag fill in order to increase the insulation value.  I'm still not clear on what the actual R value of the walls/roof are -- anyone have a good source of information on this?
It would be nice to know how cold a climate this type of construction makes sense in.

The outer covering of the house (over the earthbags) is papercrete.  An interesting house to say the least.

Beautifully handcrafted interior.

Total cost of the house was $49,900 including land and a solar electric system!  Dirt cheap (sorry).

The EarthbagBuilding.com and the Earthbag Building book that are listed are both quite good  -- lots of hands on material.  The EarthbagBuilding.com website is run by Kelly Hart.

The TV program mentioned above is Offbeat America, season 3, episode 1 on The Travel Channel -- it has a nice 10 minute tour of the house.

Gary

Cristian's Earth Sheltered Passive Solar Home in Romania

Cristian is an engineer in Romania, and has designed, built, and lived in this passive solar, earth sheltered house for two years. 

The house is very carefully laid out to make maximum use of space and and the solar heating and lighting opportunities.

 The house features:

1. Earth sheltering on three sides with a carefully designed PAHS style insulation umbrella that uses the surrounding earth for thermal storage.
2. Passive solar gain through the south triple glazed windows.
3. Active solar through several Trombe walls integrated into the south wall.
4. An extensive earth tube system that pre-heats incoming fresh air and recovers heat from outgoing stale air.
5. A carefully designed back up wood heating system.
6. Solar water heating
7. Provisions for solar electricity.

The house has a very light and open feeling.

The house is located at 45 degrees north latitude and has a serious winter -- the total heating bill for the past two winters has been $70 worth of wood -- about 0.6 cords.

Cristian says it took about 50 versions to get to this final design, and I can believe it -- it shows a lot of careful design work.

This shows the PAHS type insulation umbrella being installed.  This
basically allows earth around the house to act as thermal storage for the house.

Diagram of the layout for the insulation umbrella, drainage tubes, and earth tubes.

 All the details on the design and construction of Cristian's home...


Thanks very much to Cristian for sending in this detailed description of the house!

Gary 

Solar John in Wyoming with Automatic Solar Shutters

On the way back from Denver we happened to stop at a Rest Area in Wyoming along I25.   The rest area is one of 19 solar rest areas that Wyoming built quite a while back.

South glazing on solar Rest Area in Wyoming

Placard showing all the solar features of the rest area.

The rest areas have bunch of solar features (see placard just above),  but the one that caught my eye was the fully automatic thermal shutters. 

The automatic shutters.

It has always been a bit of a problem in passive solar homes with lots of south facing glazing that while the south windows pick up a lot of useful heat when the sun is shining, they lose a lot heat when its not shining.  While there is normally still a good net gain even with the large night time losses, its still a big improvment in performance if some kind of insulating shade or shutter can be used to reduce heat loss at night.  The problem is that many people are just not up for raising and lower shades or shutters twice a day.

These very simple and automated shutters would be one way to take care of the problem.  The shutters apparently use a set of two cylinders to do the work.  One cylinder is mounted on the sunny side of the shutter and the other on the shady side.  The two cylinders are connected by a tube.  There is some fluid inside the system that partially fills one of the cylinders.  When the sun is shining, some of the fluid in the sun facing cylinder vaporizes which drives the rest of the fluid from the sun side cylinder to the shade side cylinder.  The shutters are carefully balanced with their center of gravity very close to the point the shutters pivot about.  So, the transfer of the fluid from the sun side to the shade sides shifts the center of gravity enough so that the shutter pivot open.  When the sun goes away, the opposite happens.   Simple and clever.

A few more pictures and details here... 

Have you got any ideas for automated window insulating devices?  -- please leave a comment.


Gary

Solar Heated Stock Tanks -- Reducing Drinking Opening Heat Loss

The solar heated stock tank project has been a good success with quite a few people building them and reporting good results. 

A solar heated stock tank.

The one remaining problem is that there is still a significant amount of heat loss out the drinking opening, and when you get extended periods of no sun and lots of wind and cold, there can still be enough ice accumulation to be a problem.   BUT, it looks to me like Art has worked out a good solution to this problem.

Art uses canvas awning material to make a sort of shield that reduces heat loss from the large open water surface down to just the area of the drinking hole itself -- see the pictures below.  Art reports that with this technique the tank can go several days of sunless, cold, and windy Wyoming weather without a problem.  Ice still forms in the drinking opening itself, but the horses can easily push the ice out of the way and get to the water -- the canvas is soft enough and slick enough that the ice does not freeze to it.

Using canvas shield to insulate the water surface.

Art's tank

More details...

Thanks very much to Art for sending this in!

Gary