Build-It-Solar Blog

Hi,

I've moved the Build-It-Solar blog to a new home:

www.BuildItSolarBlog.com

I was having a lot of trouble with the old blog creation software and with its subscribe function, and decided it was better to change than to fight it.  The new blog software is the Google/BlogSpot offering, and just seems ever so much easier to deal with.

So, please reset your bookmark, and, if you were subscribed to the old one you will have to subscribe to the new one.  Sorry about the hassle, but I think this will work out much better in the long run.

I was able to move all the old posts and comments over to the new blog, so all the history should be there.

Please let me know if you have any problems with the new one. 

I will keep the old blog up for a couple months, but I won't be adding anything to it.

Best,

Gary

I've been doing some simple testing of thermosyphon solar heating systems that make use of our two homemade collector designs.   The idea being to see how these collectors would perform in a thermosyphon system and just to learn more about thermosyphon systems.

For thermosyphon systems, the heated water storage tank is placed above the collector.  The inlet of the collector is connected to the bottom of the tank, and the outlet of the collector is connected to the top of the tank.

 

As sun heats the water in the collector, it becomes less dense and rises out the top of the collector and into the tank.  The water leaving the collector is replaced by cold water from the bottom of the storage tank.   As long as the sun continues to heat the water in the collector, a circulation loop is setup in which water flows continuously out the bottom of the tank, through the collector, and then back into the top of the tank. 

 

When the sun goes off the collector, the water in the collector cools, and circulation no longer occurs since the water in the collector is more dense than the tank water and naturally stays in the collector.

 

So, in this system, the circulation is all by natural forces -- no pumps needed.  And, the control is automatic -- no controllers needed. 

These systems are very simple and are widely used in some parts of the world.

The two collector configurations I tested include the collector that uses PEX tubing with aluminum heat transfer fins, and the configuration that uses copper tubing with aluminum heat transfer fins.  Here is the performance log for the copper tube collector (click for full size):

All the details on the test are here:

Details for the PEX tube collector thermosyphon system...

Details for the copper tube collector thermosyphon system...

Please read all the details from the links above if you have an interest in this, and maybe you can help answer some of the outstanding questions.

But, the tentative bottom line appears to be:

- The collector that uses the PEX tubes is probably a bad choice for this thermosyphon application.  The collector temperatures observed would likely result in a short life for the PEX tubing.

- The copper tube collector with the top/bottom manifolds and vertical risers worked well, and would likely be a good candidate for a homemade collector in a thermosyphon collector.  There were some anomalies that showed up in the performance logging -- maybe you have an idea what is causing these?

Gary

April 22, 2010

 

 

The Mother Earth News folks have a strong interest in a solar air heating collector that works in conjunction with a regular window.  This is based on the long term popularity of the "Heat Grabber" collector that MEN published a number of years back.  While the Heat Grabber has been popular and works well, it does suffer a bit from limited collection area and, also because it sticks out from the building, which does not fit some situations.  So, the MEN folks are interested in anyone's ideas on how to improve the design.

 

The link below is my rough first prototype effort at a solar air heating collector that could be installed over a regular window.  The idea is to use the existing window to get air into and out of the collector.  This avoids any need to cut holes in the wall for vents.  It also makes it feasible to just install the collector over the winter.  Some design "challenges" remain.

So, have a look, and if you have any ideas to improve this design or have an alternative design, please leave a comment, or email them in.

Details on the prototype over/around window collector...

The first cut prototype over/around window collector.

The air ducting and screen absorber for prototype collector.


Gary

Kenneth has incorporated some very nice and new features in his innovative solar space and water heating system -- including:

• Folding collectors that allow more collector area for winter and less for summer
  
  
• Some unique new tools for collector making, including a homemade "Tee Puller', and new designs for forming and clamping the collector fins to the collector tubes.
  
  
• Use of a surplus stainless steel bulk milk tank for heat storage.

The system is built using the Solar Shed concept, meaning its a separate building that acts as both a storage or garden shed, supports collectors and provides space for the heat storage tank.

A few hightlights below, and 5 pages of construction detail here...

Folding Collectors
The two pictures below show the folding collector feature. 



The top photo shows collectors folded out for winter -- 8 active collectors.
The bottom photo shows collectors folded in for summer -- 4 active collectors (along with Kenneth).

Homemade Tee Puller
Kenneth made a tool for drawing a Tee out of a copper collector manifold part -- this allows the collector risers to be connected to the manifold without using reducing Tee fittings or brazing.

Bulk Milk Tank for Heat Storage
Kenneth used a 750 gallon surplus stainless steel bulk milk tank for heat storage.
The tank is mostly buried (to allow drainback from collectors) and insulated with 4 inches of polyiso insulation.

Gary

Here are three areas where significant energy might be saved in a home with fairly simple systems.  One has to do with using some of the heat in the hot air up in your attic, and the other two have to do with recovering some of the heat we waste in showering.

Regular showers are a major waste of energy.  Typically we spend about 3 KWH heating water for a shower, and then send about 85% of that energy right down the drain.  It amounts to about 300 KWH for a family of 4 per month.

Using The Heat In Your Attic
This page looks at some of the ways that all that heat up in the attic might be used productively.  This includes recovering heat for domestic water heating, space heating, pool heating, and cloths dryer air preheat. 
Some of these look fairly practical (to me).

I've been logging the temperatures up in my attic for about 6 months and the plot of these temps is included.  We live in a very cold climate, and it still looks like there is some potential.

Details here...

Recovering Heat From Shower Water Drain Pipes
This page looks at all the energy we send down the drain when taking a shower, and in some of the ways that are currently out there to recover some of that energy. 
It considers one (as far as I know) new method, which is basically to rearrange the drain plumbing to retain the shower water in the homes heated envelope long enough to recover the heat in the water for space heating. 
Some ways of doing this, the resulting energy saving, and a small test to examine the potential of this method are discussed.

It may seem like there is not really much potential here, but for heating climates, the potential energy saving for a family might be of the order of 1200 KWH a year.

Details ...


A Very Energy (and Water) Efficient Shower Design
This is a look at a shower design that was looked at for potential use on very long range commercial jet airplanes.  It is a very efficient design both from a water use and energy point of view.  It may not be for everyone, but have a look.

Details...

So, I'm particularly interested in whether you think any of these ideas have some merit and are worth pursuing (or not). 
Or, maybe you have some of your own "Out There" ideas you would like to share?

UPDATE: Turns out Kenneth has built and uses a recirculating shower... 
Kenneth's interest were more in getting long showers with very high flow (6 shower heads) without breaking the bank on energy use.  Its a nice simple design.

Note that Kenneth has also done a very nice Solar Shed project that does both solar space and water heating -- hope to have the details on this up soon.
Thanks Kenneth!

Gary

Pop Can Collector From Sweden
A very nicely done aluminum pop/beer can collector.  Lots of attention to detail, and lots of good assembly pictures.  In Swedish, but the pictures plus Google translator make it quite readable.
Pop can solar air heating collectors force room air through connected columns of black painted aluminum soda cans.  The sun heats the pop cans and the heat is transferred to the air.  The even distribution of airflow and large heat transfer area should make them efficient collectors.
Details here...

Update on Chad's Solar Heating System
Chad has made a number of changes to his solar water and space heating system.  He has also logged and measured the performance of the system.

All the details and performance graphs...

This is a very impressive less than zero energy home.  It uses a combination of reasonable size, excellent thermal envelope, very efficient appliances, some passive and some active solar heating, and a PV driven mini-split heat pump for additional heat and cooling.

The end result is a true zero energy house that can be built within a reasonable budget.

I cover a few of the highlights below, but all the details on the house are in the article here...

Performance
The monthly performance chart below speaks for itself.  For the year 2009, the house produced significantly more energy than it used.


Highlights
Double stud, R42 walls insulated with cellulose insulation.
R100 cellulose attic insulation.
Triple glazed R5 windows with R7 interior thermal shutters.
Very good infiltration sealing.
Emphasis on south windows for solar passive gain.
Concrete slab floors for heat storage thermal mass.
Solar water heating
Solar air heating collector to for additional space heating.
Exceptionally efficient appliances and lighting.
Heat recovery ventilation system.
Efficient mini-split heat pump for heating and AC.
4.9 KW grid-tied PV array supplies all electrical power and then some.



Total cost of the house without land is $180,000.

Solar Hot Water

Now is a good time to study up on, and start building a solar water heating system, so you can get it in this summer.
There are several high quality DIY designs that cab be built for inside of $1000. 

 Many solar water heating downloads
 




Solar Greenhouse or Sunspace

 A place to grow some plants, produce some free heat for the house next winter, or just a nice place to sit and have a cup of coffee with the newspaper. 
 Many Solar Greenhouses and SunSpaces  -- ranging from $20 to $200,000.

Tom Sullivan built a couple large water heating solar collectors.  To reduce the work involved in making the heat absorbing fins that go on the collector tubes, Tom built a very nice press to stamp out fins.

Tom has decided to make these fins available as a product from his UP Truck Center business.  He is offering fins to fit 1/2 inch and 5/8 inch tubing in lengths from 24 inches to 34 inches.  He also offers a sort of super fin option that achieves more wrap of the fin around the tube.  The prices are very reasonable, and I think this is a good option for anyone wanting to save some time on building the fins.

Here is the web page describing all the options and some notes on how best to install the fins...

Tom is a long time friend of Build-It-Solar, and has sent in detailed descriptions of some of his very well done solar projects...    Thanks Tom!



Gary

This is just a collection of some interesting (at least to me) items added tot he site over the last week or so....

Harvesting Fresh Water From Fog
Areas with regular daily fogs (e.g. some coastal areas) can harvest impressive amounts of fresh water from the fog.  Nets catch the fog and then channel droplets from the fog into a catch basin. 



Details...