Monday, October 31, 2011

A $1K Solar Water Heating System AND Open Source Differential Controller

Nathan did a really nice job of building and documenting his solar water heating system.  

The system is an offshoot of the $1K solar water heating systems with some useful new design features.
The twinwall glazing is a very nice look.
The system uses the usual 300 ft coil of PEX pipe as the heat exchanger, but Nathan recoiled the PEX for better heat transfer performance:
The 300 ft of PEX is recoiled into a two layer coil for
more water exposure to each coil.
Be aware that this recoiling can be a challenge -- think about about your method if you don't want to end up imprisoned in a coil of angry PEX.

Nathan also offers details and source code for making an open source Arduino based differential controller.
Arduino based differential controller.
Nathan has the Arduino based controller equipped with an Ethernet shield.  This allows the Ardduino to log data directly through his router to an free online logging service called -- there is no need to have a PC running 24/7 for this kind of logging, and it gives you access to the data from anywhere -- very nice!

All the details on Nathan's website....

For more on the $1K solar water heater and dozens of other DIY solar water heaters...


Thursday, October 20, 2011

Recycled Bulk Milk Tanks for Solar Heat Storage

Tom uses recycled bulk milk tanks from dairy farms for solar heat storage in some of his solar installations.
Bulk milk tank reborn as solar heat storage tank.
These tanks are made from stainless steel, and will provide a very long life.  The tanks already include some insulation of some of the surfaces.  The tanks are typically in the 300 to 500 gallon range, and the price of the used tanks is about $1 per gallon.

Heat Exchangers mounted in bulk tank.

Tom has provided some details on using these tanks...

Tom's very interesting renewable energy website...


Saturday, October 15, 2011

A Very Nice Small Solar Greenhouse on a Budget

Andrew designed and built this small solar greenhouse using mostly materials from the local Habitat Restore.

Solar greenhouses use a variety of features such as double glazing, insulation for non-glazed exterior surfaces, added thermal mass, and passive ventilation systems to reduce or eliminate the need for backup heating and for powered ventilation.

Andrew's design incorporates all of these, and he provides some summer and fall temperature and humidity logs to show how the greenhouse is doing.

Inside view showing water barrel thermal mass.

Performance plot for the greenhouse.

In addition to performing well, Andrew's greenhouse looks great!

All the details on Andrew's solar greenhouse...

Lots more on solar greenhouses and sunspaces here...


Tuesday, October 11, 2011

Bill's Large, Closed Loop $1K Style Solar Water Heating System

This is a very interesting $1K style system from Bill with quite a few interesting design variations.  Among the unique features:
  • Closed loop rather than drain back for freeze protection
  • Glazed with dual wall polycarbonate glazing.
  • A unique collector frame that uses EPDM rubber roofing for weather protection.
  • Using a custom made PVC tank liner instead of the usual folded EPDM liner.
  • Lots of detail on roof mounting the collector, including the site made collector hoist shown just below.
  • A unique design approach to handing differential expansion issues in the absorber design.

Bill's system with the first collector in place

Bill used a closed loop system because he was not able to maintain a good slope on the plumbing to and from the the collector.  This requires adding a 2nd heat exchanger to the tank that transfers heat from the collector circuit (which has antifreeze) to the storage tank which is plain water -- this is Bill's heat exchanger arrangement:

The collector loop and domestic hot water heat exchangers in the storage tank.
Another unique feature of the system is the that Bill used a custom made PVC liner instead of the folded EPDM liner.  This is a picture of the liner:

Custom PVC tank liner
This seems like a good way to go if you can get a competitive price on the liner.

I also like the special hoist that Bill made to get the collector up on the roof:
Custom made hoist to lift collector to roof.
These collectors are heavy, and Bill has several of them to get up on the roof -- the hoist will save a lot of work and be safer.

Go here for all the details on Bill's system....

Go here for the details on a hundred or so other solar water heating systems...


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