Saturday, July 28, 2012

Comparing the Performance of Two DIY Solar Water Heating Collectors -- CPVC vs Copper

Scott Davis has come up with an innovative and simple design for a solar water heating collector that uses CPVC pipes for the risers -- its easy to build and performs well.

Scott and his prototype CPVC collector.
The collector uses closely spaced CPVC riser pipes which are silicone bonded to a flat aluminum absorber sheet.    This makes for and easy and fast build.

I did a side by side performance test of Scott's design compared to the established DIY collector design that uses copper riser tubes spaced about 6 inches apart with thicker grooved aluminum fins to transfer heat into the riser tubes.  In this test, the CPVC design performed within 5% of the copper/alum collector, which I think is very good.

The side by side test of the two collectors.
There are a number of pluses and minus associated with the CPVC design compared to the copper/alum design -- things like cost, ease of build, performance, durability, and tolerance for stagnation temperatures are all important.  Which design works out best will depend on your situation -- I've tried to provide a little data on how the collectors compare in all these areas.  

I would be most interested in hearing your thoughts on the comparison and which collector you think would work out for your situation.

Full details on the performance and stagnation tests, construction, IR pictures, etc. for the two collectors...

Closer view of the test CPVC Collector.

IR image of the CPVC collector in operation
If you go ahead and build a CPVC collector, please let me know how it works out for you.


Tuesday, July 24, 2012

A New Heliostat for an Innovative New Application

There is an interesting new heliostat being offered for a low enough price to be of interest for building home systems.  The heliostat is made by Light Manufacturing Heliostats.

The heliostat has an area of 2.3 sm (25 sqft) .  The mirror is a stretched, reflectorized film to keep the cost and weight down.  Prices from about $1300.

Details on the Light Manufacturing Heliostat here....

The same company offers a unique application that uses their heliostats to provide heat for rotational molding of plastic parts (like large water tanks).  This solar thermal rotational molding system appears to be simple and cost effective, and (to me) represents some truly innovative thinking in bringing solar to a large industrial processes in a very energy efficient and cost effective way.

Diagram of solar thermal rotational molding system.
In the system, multiple heliostats focus their beams on the mold to provide the large amount of heat needed for the process.  The heliostats can support multiple molds by simply refocusing the heliostat beams on mold as needed.

The first video on this page provides a rundown on how the heliostat heated rotational molding setup works...

Heliostats can be put to many innovative uses -- I've assembled a few of them here...

Be sure to look at this one at the link above:
"ROME (Reuters) - A village in the Italian Alps is finally basking in winter sunlight thanks to a giant mirror installed on a mountain top to reflect the sun's rays into the main square."


Sunday, July 15, 2012

Making Good Use of Mountain Pine Beetle Killed Trees

This is a good and interesting video from Peter Brown about a local Bozeman, MT company that is salvaging trees killed by the Mountain Pine Beetle.

Distinctive blue coloring of beetle killed pine.

It turns out that the fungus that the beetle infects the pines with leaves a blue stain in the wood  that makes for very attractive color patterns on the boards when sawed by an experienced sawyer.

The beetle killed wood's structural properties are unaffected by the beetle infection, and the wood can be used for a wide variety of purposes.  The blue staining gives it a distinctive look that has made it popular for furniture and doors.

A great example of making good use of local materials that would otherwise go to waste.

Neil Wilbert of Beetle Kill Boards with his portable saw mill.

Makes very nice furniture.

See the story  on Peter's Video Blog...


Saturday, July 7, 2012

DIY Solar Water Heating for 7 Unit Apartment

This is Micah's DIY solar water heating system for a seven unit apartment building in Iowa.

Collectors solar preheat water for apartment building.
The system is a drain back system similar to the $1K systems, but larger to accommodate the 7 units and with a few design changes to match the situation.

The solar heated water storage tank located inside the building's utility room right behind the collectors, which makes for nice direct plumbing.

The collectors.
The collectors are glazed with twinwall.  Note the very nice job of trimming and flashing the collector glazing.

The tank is a non-pressurized combination drain back and solar heat storage tank that is constructed with OSB and lined with EPDM rubber membrane.

Drain back and solar heat storage tank.  

Nice simple plumbing using PEX and SharkBite fittings.  These are the valves that allow the solar water preheat to be bypassed if desired.

Micah's day job is in Nepal, and he has some interesting comments on solar in Nepal.

Solar water heaters everywhere in Nepal

Download all the details on Micah's 7 unit apartment solar water heater...


Tuesday, July 3, 2012

Cooling Without Power

I know there are a few million people out there now in hot weather and without power due to the storm.

Here are a few ideas on cooling without electricity that are quick to implement and might be helpful during the hot weather power outage.

If you know people who are without power in hot weather, please pass on these ideas to them.

- Stop window solar heat gains during the day.  Windows that face south, east or west are major sources of solar heat gain that tend to cook the house.  Its critical to stop this heat gain from heating the house.

The best place to stop the solar heat gains is outside the windows with external shades -- this keeps the heat totally out of the house.  If you are working from the inside of the house, closing blinds (especially if they are reflective) is helpful.   Putting aluminium foil against the window would be much more effective in that it efficiently reflects both the visible and IR in the sunlight back out the window.

An easy and quick to install set of external shades like these can make a huge difference...

More on window shading here...

- Water the roof.  Putting a sprinkler on the roof to wet it down intermittently will cool the roof by evaporation, and therefore cool the attic.  The cooler attic will reduce the heat gain to the house.  Here is an example roof cooling system...

There are more examples in this section of the Cooling page on Build-It-Solar...

Example of a fancy roof cooler, but a sprinkler or two will do.

- Shade the house.  This may not be that easy to do on short notice, but anything that shades the exterior of the house will reduce heat gain.  Maybe a jury rigged set of Shade Sails?...

- Using cool basement air.  Some people have reported that circulating cool basement air to the living area can be quite helpful.  This is a simple example of Fran's system...  While this system uses a small fan, if you open a window in the basement and a window as high as possible in the house, the stack effect will tend to circulate the air even without a fan.  Or, I guess, you cold just move down to the basement?

- Ventilation.  In these days of Air Conditioning and powered everything, people tend to forget how effective night time open window ventilation can be.  Opening windows on opposite sides of the house in the direction of the wind is helpful.  In multi-story homes, opening windows low and high makes use of the stack or chimney effect to circulate more air.
If it cools off enough at night, using as much might ventilation as possible to cool the thermal mass of the house will make it more comfortable on  the following day...

If you can rig up a fan that is solar powered or car battery powered, this can help a lot with the ventilation.  Solar powered attic ventilation fans are available at a lot of hardware stores...

- Evaporative Cooling.  One simple form of evaporative cooling that has been reported to work pretty well if you have a concrete patio and a window above the patio where air is flowing into the house.  You wet the patio area down with a hose, and try to keep it wet.  The evaporation of the water cools the air before it enters the window.  The evaporation also adds humidity, so this will not be as effective if the humidity is already high.
Conventional evaporative (swamp) coolers require some power, but much less that conventional AC units for the same output, but, again, are less effective in high humidity areas...
Some evaporative coolers are solar powered -- an example...

Edit July8: Note the DIY solar powered evaporative coolers here...  This is something one might be able to make on short notice for cooling during an extended power outage.  It could be run directly off solar or a solar charged car battery.

Mist Cooling.  Mist cooling can be very effective for even fairly large outdoor areas.   Here is one DIY outdoor mist cooler...   Dripworks sells an inexpensive mist cooling kit...

- Cooling just your immediate area.  This section gives two simple schemes in which only your immediate sleeping area is cooled...  Very little power required.
If you can get ice, the water bed scheme might work with ice cooling?  Insulate around the outside to keep the coolth in the waterbed.

- Reflective roofs.  This is perhaps a bit extreme, but you could change your roof color to white...

There are dozens more cooling ideas on the Build-It-Solar Passive Cooling page -- many of these require no or minimal electricity to implement ...

If you know of any additional good cooling ideas for emergency power outage situations, please add them in the comments, or email me -- Gary...

If you try any of these methods, I'd like to hear how they worked out for you.

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