Monday, September 27, 2010

Our Solar Heated Stock Tank In Mother Earth News!

The new issue of Mother Earth News (October 2010) has a full article on the solar heated stock tank we built for our neighbor's horses.

Lori and Kevin commissioning the new Solar Stock Tank

In cold climates, keeping the water in livestock tanks from turning into a solid block of ice can be a real challenge.  One common solution is to use an electric stock tank heater -- this works, but the down side is that with the typical uninsulated metal stock tanks the heat loss and energy uses are huge.  In our climate during cold weather, you can easily spend $3 a day in electricity just keeping a tank ice free.

The insulated tank enclosure with south glazing.
The Solar Stock Tank design encloses an ordinary galvanized stock tank in a well insulated box.  The south face of the box is double glazed with impact resistant polycarbonate glazing.  The south wall of the stock tank is painted black and absorbs the solar radiation quite efficiently.  The insulation and double glazing reduce nighttime heat loss.   The tank can be used without a heater in all but the most extreme weather.
Lori, Darby, and Princess.
Its a pretty straight forward DIY build.  The energy savings can pay back the cost of the tank materials in as little as a couple months.  There is also a large saving in CO2 emissions associated with not using the electric heater.

The online version of the Mother Earth News article...

Very detailed information on the tank construction and performance ...

Other DIY solar and efficient stock tanks people have sent into Build-It-Solar...

If you know of other tank designs, please let me know.


CO2 Released When Making or Using Products

I've been looking around for a simple source of information on what the CO2 emissions associated with using certain materials are.
The site is the best I have found so far for providing this kind of information in a usable format.

They offer this table that summarizes CO2 emissions associated with many materials and activities...

Small sample from the table.
If you know of other good sources for this kind of information, please let me know.

More references and calculators on CO2 emissions and energy use for activities...
(e.g. -- did you know that the QE2 gets 0.0075 mpg?)


Friday, September 24, 2010

Sandy's $1K Solar Water Heating System On Prince Edward Island

Sandy describes in detail his new $1K style solar water heating system. 

The collectors mounted to side of house.
The collectors use a unique horizontal riser arrangement that makes better use of the copper tubing for horizontal layouts.   The collector mounting to the house is by a hook and eye arrangement that makes for minimal impact on the siding.

The tank heat exchanger PEX coil being wound on a form to
space the coils out for better heat transfer.

Very nice tank arrangement -- looks a lot better than mine :)
Note the small SwiftTech pump mounted on the side -- uses only 18 watts.
The tank is very nicely done, and might be a good model for people who will have tanks located where they are visible and need to look good.  Sandy uses a 300 ft coil of 3/4 inch PEX for the heat exchanger, and took the time to rewind the coil for better separation of the individual coils to improve heat transfer.

All the details on Sandy's Solar Water Heating System...

Lots more DIY solar water heating system plans and examples...

This solar water heater is a part of Sandy's overall plan to reduce energy consumption and CO2 emissions -- other parts include a new efficient boiler for space heating, upgraded insulation, a Prius, and more efficient appliances -- maybe we can talk Sandy into a report on how the whole program effects their energy use.


Monday, September 20, 2010

Philip's Fiji Island DIY Thermosyphon Solar Water Heater

Philip lives on the beautiful Pacific island of Fiji, where the scenery is stunning, but the utility rates are on the high side.
This picture just knocks me out -- wonder if Fiji needs another solar guy?
Philip worked out a nice and simple warm climate thermosyphon solar water heating system.    The system is very simple: no pumps, no heat exchangers, no differential controllers, no anti-freeze.   Just a PVC storage tank located above the collector, and the thermosyphon effect does all the rest.

The PVC solar heated water storage tank.

The thermosyphon collector.

The total cost was only $250 US.

Philip provides the details on how he designed and built the thermosyphon system...

Much more on DIY solar water heaters for climates from the Artic to Fiji...

 Gary  September 20, 2010

Thursday, September 16, 2010

A Large Solar Space and Water Heating System in Iowa

This is a very nicely done system by Thom that provides both solar domestic water heating and solar space heating.

The 200 sqft, homemade collector with twinwall glazing.
This is a drain back system with the 300 gallon heat storage and drain back tank located about 50 ft from the collectors in the house.  When the sun is off the collector and the circulation pump is not running, the water in the collector drains back to the tank in the house for freeze protection.

The collectors are modeled after the $1K Solar Water Heater design in which aluminum fins are thermally bonded to copper pipes.  This design provides 96% of the performance of commercial collectors at 1/5th the price.
Thom bonding collector fins to copper tubes.

The lines between the collector and the heat storage tank are run in a trench through the yard.  As the picture shows, the pipes are packaged up in XPS styrofoam insulation to reduce heat loss.

Insulated pipes going into the heat transfer trench.
The tank is an EPDM lined and well insulated plywood box.   It holds about 300 gallons.  While this kind of design may initially give you some pause, it is a well proven design that goes back to the 1980's and has a very good track record. 

Thom is using the system for both domestic water preheating and for space heating.  The domestic water preheat is accomplished by running the cold water supply through a 300 ft coil of PEX pipe that is immersed in the tank.  This is a very effective preheat system that is 100% efficient for most water demands, as the water in the pipe gets preheated to full tank temperature.  A 2nd copper pipe coil heat exchanger supplies water for space heating to a radiant floor.  Depending on the details of the plumbing, it may not be necessary to use the copper pipe coil -- some have just pumped hot water directly from the tank, through the radiant floor and them back to the tank.

The EPDM lined tank with the two heat exchanger coils.

 All in all, quite a nice system :)
Thanks to Thom for documenting it so well.

I feel a bit of a part of this system myself, as Thom and I exchanged a record number of emails during the project.  Its really nice to see it up and running :)

Thom experienced some start-up difficulties with the system, and I have to admire the way he handled working through these -- things don't always go smoothly, and after putting quite a bit of effort into building a system, it takes some real discipline to work your way through unexpected start-up problems.  Thom has done a good job of documenting these.

All the details on the system on Thom's website...

Similar systems on Build-It-Solar...


Sunday, September 12, 2010

Greg's Pop-Can Solar Air Heating Collector

Greg's solar air heating collector uses recycled aluminum soda pop cans for the absorber. The pop cans have the tops and bottoms drilled out, and are assembled into vertical columns that the air passes through. 
In operation, the black painted soda pop cans are heated by the sun, warming the air that is flowing up through the cans.

Greg's finished pop-can collector
 A manifold at the bottom evenly distributes room air to all the can columns, and a similar manifold at the top of the collector collects the heated air for distribution back to the room.
Lots of cans!

The combination of uniform air distribution to the whole collector and the large amount of heat transfer area from the cans to the air makes for an efficient collector. Greg's collector also uses Twinwall polycarbonate glazing -- this is a type of double glazing that reduces heat loss and increases the efficiency of the collector.

Detail of upper manifold.

 Greg sent in a very detailed (22 page) description of the full construction process with lots of pictures.

All the details on Greg's pop-can solar air heating collector here...

Thanks very much to Greg for documenting and sending in this project!

Lots more solar space heating projects here...


Saturday, September 11, 2010

Nicely Done Pipe Coil Style Solar Pool Heater in Tuscany

This is a nicely designed and carefully constructed solar pool heater for a swimming pool in Tuscany.

Quite a bit of detail is provided on the construction and the performance.  
The plumbing arrangement is particularly flexible.

The measured performance data indicate that the pipe coils achieve the same efficiency per square foot of area as conventional rubber mat style pool heating collectors.

I think that a trip to Tuscany to do field research on this is required :)

Closeup of one of the pipe coils.

The plumbing layout for the pipe coils.
Direct link to all the details on the Tuscany pool heater...
Thanks very much to Steve for suggesting this.

Quite a few other DIY Pool heating collector detailed descriptions...

The Build-It-Solar solar pool heating page...


Wednesday, September 8, 2010

Full Scale Test of Evapro/Radiation Cooling System

These are the results for the first full scale test of the Evapro/Radiation cooling system that I experimented a bit with last year.

This cooling scheme uses trickles of water down a surface that is pointed at the cold night sky.  The water trickling down the surface is cooled by a combination of radiation to the sky and evaporation of some of the water.  The cooled water is saved in a "coolth" storage tank for use on the next hot day.  For climates like ours which normally have cool nights even when the days are hot this works well.  Surfaces that are free to radiate to the night sky will cool significantly below ambient air temp, so the water can be cooled below the ambient air temperature.  

This full scale version uses the North roof surface of my Solar Shed as the cooling radiator to cool a 430 gallon tank of water during the night time.   When cooling is needed in the house during the following day, the cooled water in the tank is pumped over to the house and through the radiant floor heating loops in the house for cooling.
The solar heating side of the Solar Shed

 The same water storage tank and radiant floor loops that are used for heating in the winter can be used by this system for cooling in the summer with very little new work to be done.  Even the controls are unchanged except to switch from heat mode to cool mode.  So, you can basically add the cooling function for only a few dollars and a few hours of labor.

The cooling side of the Solar Shed in operation.
Normally this would be done  at night.
The picture above shows the Solar Shed in cooling mode.  Water from the "coolth" tank is distributed along the ridge line by a pipe with small holes.  It trickles down the roof surface, cooling it down in the process.  The cooled water is then collected by the gutter at the bottom, and routed back to the cooth tank.  Really simple, but the combination of cooling due to both radiation and evaporation is quite effective -- several times more efficient than conventional AC. 

We had such a cool summer here this year that I really did not have much motivation to get the full scale system set up, and only ended up with one hot day of testing.  But, I've received quite a few questions on the system, so I thought I would pass along the results from the one day test.  I plan to do more for next summer.

The link just below gives quite a bit of detail on how the test went, but the quick summary is that we were able to collect quite a bit of coolth in the tank efficiently, and that it kept our house comfortable through our one day (96F) heat wave.   The estimated COP of the system is about 22 (roughly SEER 75) -- several times more efficient than conventional air conditions. 

All the details on the full scale test of evpro/radiation cooling system... 


Tuesday, September 7, 2010

Determining Solar Collector Flow Rate

This blog entry deals with picking the best water flow rate for the solar collectors in a solar water or spacing heating system.

There are a lot of recommendations around on what the flow rate through water heating solar collectors should be.

These are some of the recommendations floating around out there:
- Heliodyne recommends a range of 0.025 gpm/sf to 0.075 gpm/sf
- SunEarth recommends 0.025 gpm/sf for their collectors
- Solar discussion groups often talk about 0.02 to 0.03 gpm/sf a good number.
So, what is the "best" number, and what are the tradeoffs?

In a nutshell, if you set the flow rate too low, then the collector will run  hotter than it should, and this will result in larger heat losses and a less efficient collector.  On the other hand, setting the flow rate too high results in a larger pump and larger pipes than are really needed, and this increases both the initial and operating cost of the system.

The table below shows the reduction in collector efficiency and heat output as the flow rate is decreased from a high flow level:

All the details on how these flow rates are arrived at here...

Details on sizing a pump to deliver a given system flow rate ...


Thursday, September 2, 2010

Our Prius Goes Over 100K Miles -- Savings Todate $10,400!

Our Prius just ticked over 100K miles a couple days ago.

I've chronicled our experiences with the Prius on this page...

I used the calculator on to estimate the total savings to date.  I compare the Prius to our other car, which is a Honda Pilot -- its the car we would be driving if we did not have the Prius.  The Pilot is also not too far from the US fleet average.

So, the savings for the first 100K of Prius vs Pilot are:
  • 3467 gallons of gasoline
  • $10,400 in gasoline costs
  • 33 tons of CO2
Truly amazing numbers -- if we keep the car as long as we did our last car, the savings in gasoline costs will probably pay the full initial cost of the Prius!

I know people tend to either love or hate the Prius, but just from an engineering standpoint, its an amazing accomplishment. If we could get the US fleet average just up to what a Prius already gets, we would not have an oil import problem, and it would make a significant dent in our Carbon problem.

Added Sep 4: based on some questions, added this page that compares hybrids to non-hybrids over a 100K miles distance -- including fuel costs.  Also the costs for some big cars/SUVs/trucks.

More stuff on efficient vehicles..   +

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