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Experimental Solar DIY Projects

Solar and renewable energy ideas and projects that look promising (or at least interesting).


One of the appealing aspects of the solar thermal area is that "garage inventors" can make meaningful advances.   Some of the factors that make it possible to keep coming up with new ideas and innovations in this centuries old field are:

  • Innovative ways of combining collection, storage, insulation, and distribution of solar energy

  • New ways to integrate solar features with architectural features

  • Opportunities provided by new materials

  • Opportunities provided by increasing prices in conventional energy sources

  • Opportunities provided by the pollution consequences of conventional fuels

If you have a concept that you think should be here -- please send it in!


Directory for this page:

Note: New section on measurement techniques for solar thermal experimenters.


 Solar Inventor Resources
New Inventions in Low-Cost Solar Heating

William Shurcliff

Click here for Extensive Extracts from this book

My all time favorite solar book.  Published in 1979, but still has many interesting concepts that are well described.  Out of print, but available at BookFinder, Amazon used books, etc. 

The picture here is one of a hundred concepts in the book, each interesting and well explained.

David Delaney's Site


This is David Delaney's site.  He usually has some new and interesting ideas cooking.
Phase Change Materials Homepage

And, from the EERE site:

PCM supplier

The latest on the application of phase change materials for heat storage.
Potential DIY Phase Change Material for Heat Storage


Nick Pine posted this note describing a phase change material for heat storage that was developed by George Lane some years ago.  It appears to have some potential for use as a low cost, home made heat storage material in solar heating systems.
Electric Bicycle Experiments


A large collection of experimental electric bikes and trikes.  Some with fairly detailed descriptions.
Backyard Inventor Projects   -- modest to moderate size projects that any of us could think about working on
Modified Trickle Down Collector (MTD)

Richard Heiliger's detailed description of the MTD he built ...



John Canivans website with MTD information ...

This is a new version of the Thomason Trickle Down Collector.
It uses less expensive materials, is easier to build, and may be more efficient.

Richard Heiliger provides a very detailed description of the MTD  he built, and also on some of the testing that John Canivan and he did to arrive at their designs.   
Full description ...

Solar Heated Livestock Watering Stock Tank Prototype

Details ...



This is a first cut at a livestock watering tank that is insulated and solar heated to keep the water above freezing.

The usual approach around here to keeping stock tanks from freezing is to use an electric stock tank heater, which uses a lot of electricity.    This approach might eliminate or greatly reduce the need to such heaters and the cost and GHG's that go with them.

Details ...

Optimal Solar Air Collector Design



Careful design of air collector baffles and fins may allow high efficiency solar air heating collectors that are still simple and cheap to build.

These collectors have the potential for 1 to 2 year paybacks on material costs in cold climates.

Horizontal Pond Domestic Hot Water Heater

Gary and Nick


An experimental concept for a domestic solar water  heating that uses a pipe coil in a glazed pond to collect energy.
The goal is to provide a full four season solar water heater with the simplicity and low cost of a batch solar heater.
It is looking promising, but still some issues to resolve.
Comments welcome.
SunCache Solar Water Heating -- Davis Energy Group


A little more here:



This is a soon to be commercially available, low cost, Integral Collector/Storage solar water heater.

It is said that it will cost substantially less than current solar water heaters, and will be available as a kit. 
The collector contains 50 gallons of water for thermal storage that remains in the collector forever.  Fresh water that is to be preheated passes through a copper pipe coil inside the collector to pick up heat from the thermal store.  It is somewhat similar in design to the Horizontal Pond collector above and to the "Hot Harry" collector shown further down this page.
Double Play -- An Experimental Solar Heating and Cooling System
Steve Baer

and the Zomeworks site

Roof Integrated Solar Absorbers: The Measured
Performance of “Invisible” Solar Collectors
Preprint (700K pdf)

Roof Integrated Solar Absorbers -- slides

Roof Integrated Solar Absorbers
Home Power magazine article, issue 102

This innovative system uses unglazed collectors that are integrated with the roof structure and a unique thermal storage system to provide solar thermal heating in the winter and radiation cooling in the summer. Amazing!

The pdf report provides detailed performance measurements from the FSEC & NREL.

Theoretical Evaluation of the NightCool Nocturnal Radiation Cooling Concept
Danny S. Parker
Florida Solar Energy Center (FSEC)

New report on the NightCool performance in test buildings:
Experimental Evaluation of the NightCool Nocturnal Radiation Cooling Concept: Performance Assessment in Scale Test Buildings,
Danny S. Parker, John R. Sherwin
Florida Solar Energy Center (FSEC)

Daily performance of the test buildings,


This is a simple, building integrated, cooling scheme that uses nighttime  radiation cooling from a metal roof to cool air in the attic space.  Attic air is then circulated into the living area to provide cooling.
A simulation model is used to predict performance in various climates -- the scheme works very well in dry areas, and fairly well even in very difficult moist-warm climates (e.g. Florida).
One of the attractive features of this system is that the roof is very conventional -- no massive ponds or moving insulation.
There is the potential in some climates to use the same metal roofing/attic system for space heating in colder weather.
The new test report shows the results for two 10' by 16' structures that were built to compare NightCool performance to conventional AC in Florida.  Very interesting and promising results.
Tests of a a simple dehumidification system using  desiccants are now underway.
The Rotating Solar Boiler

The Whole Story...


A new idea for low cost, high temperature solar collectors.
Simple Pool Heating Idea



This is an idea for a simple, cheap and efficient homemade pool heating collector.


Solar Shed for Space Heating House

Solar Shed



This idea uses solar collectors and heat storage tank installed in a multi-purpose outbuilding to provide space heating for the nearby house.
Evapro-radiative Cooling Thoughts


Full Story ...

This is exactly the same collector listed just above, but used for cooling instead of heating.  The idea is that at night water from a storage tank is pumped over the collector surface to cool.  The water cools by radiation to the night sky and evaporation.  The chilled water in the storage tank would be used for space cooling the next day.
And, some thoughts on practical cooling and heating applications using this scheme.     Full Story ...
Experimental Solar Collector Made from Twinwall Panel ...


This is an interesting idea for a collector.  It uses the channels in a Twinwall glazing sheet as flow passages for water.  Slotted pipes fit over the ends of the twinwall sheet to act as manifolds.
I'm a bit skeptical of the temperature capability, leak sealing, and life of this panel, but its certainly an interesting idea.
Finding a twinwall that holds up to long term exposure to hot water may be a issue -- GE says that polycarb does not.
(thanks to Brent for finding this)
The Quest for an R15 Thermal Window Shade Some thoughts on developing high R value thermal window shades.

Such shades have the promise of greatly reducing window heat loss, while still being convenient to use.

Details here ...

Combined Solar Collector and Window Shade


The Story


An insulating window shade that also acts as a solar collector, and that automatically transitions from one to the other depending on conditions.
Flow Organizer A try at the Saunders/Delaney/Pine  flow organizer.
The Integral Passive Solar Water Heater Book, David Bainbridge

Download this book

Even though the batch water heater design is an old one, I think there is a great deal of opportunity for improvement.  How about an all season, $300 solar water heater with a payback of one year -- this seems reachable to me with some refinement of the designs. 

This book is book is a great place to get up to speed on the potential.

This is a really fine book on all aspects of designing and building a wide variety of solar batch water heaters.

The book has a great mix of how-to and engineering design information -- great for builders and experimenters.

Thanks to David, the full content of the book is available here as a free download.

Low Tech Garage/Barn Heater (pdf)





An experimental idea for heating barn or workshop spaces.  Inexpensive and easy to build (honest!).


Solar Water Collector from CPVC Pipe

CPVC Collector Test



This is a try at a very easy to build and cheap solar flat plate collector that uses CPVC pipe, and extruded alum radiant floor heat spreaders.

Mixed results.

The Rutgers Solar Heating System for Greenhouses
Mears, Roberts, Simpkins, and Kendall
Rutgers University

The Rutgers Solar Heating System for Greenhouse - 1977 (0.8 MB pdf)

Greenhouse Solar Heating-1981 (2.5MB pdf)



A related paper on a solar home using a similar flooded subfloor heat storage scheme.

The solar collector shown here was developed in the 70's as a very inexpensive greenhouse heater.  It works well for situations in which only low temperatures are required (like greenhouses and pools).

While I do not know of anyone who has tried this as a pool heater, it seems to me it might work well, and it would be very inexpensive -- perhaps $2 per square foot?

The papers give information on a several greenhouse energy schemes, so you have to wade through all this to find the details on building the collector.  The collectors described in the paper a quite large, but could be scaled down.  Note that even though this is a very simple collector, there are details that you must get right for it to hold together -- so read all the construction notes.

If you build one of these PLEASE let me know -- Gary

A number of other interesting commercial greenhouse related papers at the Rutgers Horticultural Engineering Website:

Solar Closets and Sunspaces

Nick Pine and Paul Bashus



An interesting idea for coupling a low thermal mass solar collection area with a well insulated, high temperature  heat storage area that is used as a "solar battery" to heat the attached house during cloudy periods.
Grey Water Heat Exchanger In A Barrel

Nick Pine (with a little help from Gary)


Canada study and test of grey water heat recovery system for a residence ( 3 MB pdf)

An innovative version of a grey water heat exchanger that may be able to recover a large fraction of the heat that normally goes down the drain.  It is inexpensive and is constructed inside  a standard steel barrel.
The Amazing Heat Scavenger Experiment ... .pdf



An interesting and simple experimental setup to show the potential (and some of the problems) of capturing heat from grey water from the shower.
Integral Stagnation Temperature Control For Solar Collectors (pdf)
S.J. Harrison, Q. Lin, and L.C.S Mesquita
Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, Canada

SESCI 2004 Conference

A passive approach to automatically decreasing the stagnation temperature of solar collectors.  An air channel behind the absorber plate is used to ventilate the collector when the temperature exceeds a set value.   A valve at the top of the air channel opens automatically at a set temperature.


A scheme to use soap bubbles as insulation on greenhouses (or other structures) to prevent night heat loss.
Solar Bubble Build


Pretty detailed description of a building using the soap bubble insulation scheme.  An interesting site -- with some new ideas.

How to Build a Heliostat for Solar Heating and Lighting,
Rob, ...


Rob's heliostat -- reflects solar light and heat into a window in your house.
An interesting idea if your house is lacking in south windows.
Some detail provided on the construction.

Inflatable Heliostat

Download full report pdf (3.5 mb)

Mithra and Gary

Another interesting inflatable idea ...

An experimental, low-cost heliostat design that uses air pressure to focus and support the mirror.


Paper on PV powered irrigation system has a unique(?) combination of fixed reflectors and 1 axis tracking to increase PV panel output

Helikson, Haman, and Baird

The Paper (pdf)



This paper on a PV powered irrigation pumping includes an interesting scheme to increase PV output.  It has fixed reflectors on each side of the PV panels, and a single axis tracking system to point the entire rig toward the sun.  The reflectors are said to increase panel output by 33% (not counting the tracking benefit).

Does this seem like a good idea?

Solar Heated Home Using An Attached Greenhouse and Woodburning Stove

David Mears

The Paper (pdf)


A short article in Live Science on David's house

This 1981 paper with a 2004 update describes a solar heated house with a "flooded subfloor" thermal storage area. 

Seems like an interesting concept.  Test data for a real house is provided.

Papercrete Construction


PaperCrete is a building material made from a mixture of recycled paper, sandy dirt, and a little cement.  It has an R value of 2.8 per inch, good strength, and is lightweight and inexpensive.   While PaperCrete has been around quite a while, it has just started to be used for home construction, so this is for adventurous experimenters.
Roof Sprinkler Cooling System,

Full Details ...


Roof sprinkler system lowers roof temperature and cooling bills by keeping the roof cooler through water evaporation.

Added a description of another similar system 3/6/07
Simple Engine Driven By Low Level Heat,
Deluge, Inc.

DOE article:

A simple engine that uses low level heat (180F) to expand the CO2 to drive a piston.  


From The Energy Blog

Interesting New Projects
Drake Landing  -- Community with Solar Seasonal Storage for Water and Space Heating

Modeling of Borehole Storage: (pdf)

New Alberta community uses 2300 sq meters of solar thermal collectors to collect heat in the summer for use in the winter.  Heat is stored in a field of 144 boreholes, and distributed by a common heating loop serving the 52 houses.
Vertigro Oil From Algae

On "The Energy Blog" ...


This looks like a pretty simple way to get sustain high growth rates and oil production from algae?

The video has the best description of the process.

MIT's Warm Light Wall System



An interesting solar wall/window construction that was used on the MIT Solar Decathlon entry.
The wall uses a layer of aerogel insulation (which transmits light) and a glass block that is apparently filled with water to act as thermal mass.  It appears to have an insulation layer on the inside as well (to control the heat transfer rate to the interior?).
It may provide some combination of solar gain, light, and storage in one unit.   As usual with solar decathlon projects, its hard to find any details or performance -- if you find something, please let me know.
Road Energy System -- solar heating from your parking lot



A system from Invisible Heating Systems Ltd that embeds plastic pipe in asphalt pavement to recover heat.
No detail on what weather conditions lead to successful heat recover, but maybe they will tell us how its working out in a while.  Seems like it might work well for public swimming pools with large parking lots?
Magenn Power Air Rotor System

An Helium inflated wind generator



An interesting idea for a helium inflated wind generator.
Night Sky Roof Water Spray Cooling system

EERE report (pdf)

ORNL gov report

The first link above provides the most complete design information, and describes three different roof spray system designs. 
While these papers seem to be aimed primarily at commercial applications, residential applications may well be workable, simple, and energy efficient.
Most beneficial for dry climates.

"This innovation spray-cools water on the roof at night and applies the cooled water to reduce subsequent cooling loads. On clear nights, the sky is much colder than outdoor air, contributing to high water cooling rates through a combination of evaporation and sky radiation. Overnight, NightSky systems can typically cool a large storage volume (preferably two gallons per square
foot of roof surface) to a final temperature as much as 12 degrees below the minimum night air temperature."

Seems like a very promising way to reduce the energy cost of cooling.  The 5600 sqft prototype described in the first link achieved an EER of 149.

It seems like this system while currently used for commercial buildings is simple, and might well be adapted to cooling a residence??  The first link gives some useful design guidance on cooling per sqft, tank sizes, ...

Solar Thermal Electric Power Plant




A new solar thermal electric power generation installation in Nevada with some improvements.


Michael has shows some interesting concepts in home/building design.  Some of these have the potential for good energy efficiency -- as in the Home-Scape pictured here.
Mobile Window Thermal Test (MoWiTT) Facility




An interesting test rig to measure the side by side performance of two test windows under actual field conditions.
Interesting New Products
Solarcentury solar thermal and solar electric roof tiles ...


The data sheet, brochure, and video show pretty good installation detail.

An interesting new UK product.  These are standard roof tiles that are solar collectors.  There is a solar thermal version that heats water, and a solar PV version that generates electricity. 
The thermal versions appear to come in pre-plumbed horizontal runs of several tiles.

(thanks to Doug for finding this) 
Advanced Thermal Solar System With Heat Storage For Residential House Space Heating (pdf)
Kazimierz Szymocha

SESCI 2005 Conference


An interesting concept for a solar wall heater.  The absorber has integrated heat storage in the form of Phase Change Material.  The objective is to store heat during the day in the PCM, and let the PCM warm the wall that the collector is mounted on at night -- this reduces heat loss through the wall.  More...
Hot Harry

Gough Industries

download Hot Harry pdf

This Australian design has some features in common with the Horizontal Pond scheme just above, and some new features.  The case is rotationally molded PE, it incorporates two layers of glazing with a transparent honeycomb material between them for insulation.  The sun heats the bath, and transfers heat to an immersed coil of copper pipe.  The prices seem on the high side given what looks like a cheap manufacturing process?
Combined PV - Air Collector as Heat Pump Air Pre-heater

H. A. Zondag

Download details pdf

An interesting idea to use the normally wasted heat from PV panels for thermal heating.   Should about triple the useful energy output from the PV panel.
Sunflower 250 -- Concentrating PV,
Energy Innovations


An interesting concentrating PV design.  First deliveries for early 2007.

"Now standing at a little over five feet square and five feet high, the 25X Sunflower™ is able to meet our targets for both energy generation and cost. Each of the 25 1'x1' mirrors is separately aligned, and yet all are attached to and moved together by an undercarriage controlled by just two motors. The receiver is approximately the size of one mirror and contains a collection of small cells that are wired together to produce electricity. It is backed by fins that dissipate heat and keep the cells operating within 30°C of ambient temperature at all times."
Home CoGeneration Units

Honda Version:
Honda Micro CHP Home Cogeneration System

Article on home CoGeneration:

The Marathon Version:

Infinia: ...

An assessment of CHP from

Some early testing in US:

Home cogeneration systems offer the possibility of putting the waste heat produced when generating electricity to a useful purpose (heating your home).  The end result could be some cost saving, and an about 30% reduction in green house gas production.
As seems to be usual with any new technology to reduce energy use and pollution; availability and adoption in the US is slow.
Whisper Gen  -- CoGeneration



Another residential cogeneration system that comes in either an on-grid AC version or and off-grid DC version.
The website provides quite a bit of detail.
Not currently available in the US?
Some Test Results
This  just a place to put the results from some random tests that were run to settle some burning issue.
Effect of edge gaps on the performance of insulating shutters and shades,
William shurcliff,
Thermal Shutters and shades, 1980

Details ... (pdf)

Some simple tests that William Shurcliff did for his book Thermal Shutters and Shades to determine how tight insulating shutters and shades need to fit in order to not have excessive heat loss.

Extracted from "Thermal Shutters and Shades", William Shurcliff
with permission.
EPDM Collector Test

Details Here ...


This is a test I did some time back in trying to see if a collector absorber constructed from EPDM (rubber) sheet would work for my Solar Shed project.

While the results were not good enough to use it on the Solar Shed, they were not totally discouraging, and I think that the idea has some promise. 
There have been successful commercial collectors made from EPDM in the past, so there is probably some combination that works.   A lower tilt angle would also help with the water spread problem.
The appeal of an EPDM collector is that the cost could be south of $3 per sqft -- compared to $30 per sqft for commercial collectors.
Transmittance of Corrugated Glazing

The Test


Do the corrugations in corrugated glazing (e.g. SunTuf glazing) reduce the solar transmittance compared to flat glazing?
Here is a little to test to find out.
Temperature Stratification in Tall Rooms




This little test was done to settle a "discussion" about how much the hot air tends to rise and stratify at the top of a tall room.  You may be surprised by the answer.


Flow Organizer




A try at the Saunders/Delaney/Pine  flow organizer.
Radiant Floor Heat Spreader Plates Test

Heat Spreader Plate Test

DIY Press to make Heat Spreader Plates


A little test to determine how best to install heat spreader plates for radiant floors.
Shower Temperature Drop



I'm sure you were dying to know how much the water cools from the shower head to the shower drain -- here is the answer.
This drop is of interest because it is heat that cannot be recovered using a grey water heat exchanger:
Shower Temperature Drop

A shower design that might reduce the temperature drop:


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