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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:
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.
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| Solar Inventor Resources | |
|
New Inventions in Low-Cost Solar Heating William Shurcliff |
 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 http://freespace.virgin.net/m.eckert/index.htm And, from the EERE site: www.eere.energy.gov/consumerinfo/factsheets/db3.html 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 http://electric-bicycle-experiments.com/
|
 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 | |
|
A $6/sqft solar collector using Copper tubing and
Aluminum fins
Gary This collector is an offshoot of the collector just below. It uses the same scheme to transfer heat from the aluminum fin to the heat transfer tubing, but copper is used instead of PEX for the tubing. This adds a modest amount to the cost per sqft, but provides performance that is quite close to all copper commercial collectors. |
The fin to tube thermal connection is similar to the collector above, but copper is used for the tubing instead of PEX. This provides performance within 4% of an all copper collector in an easy to build package. Extensive build, testing, and performance information is provided...
|
|
A $4/sqft solar collector using PEX tubing and Aluminum
Fins
Gary
There has been a lot of interest in a collector that uses PEX tubing rather than copper to convey the heat transfer fluid. Here is a cut a collector that does this -- with careful attention to the PEX/fin joint, it can perform surprisingly well. |
 This
is a cut at a solar water heating collector that uses PEX tubing instead of
copper to convey the heat transfer fluid. The fins are aluminum,
and a lot of effort was put into attaining a good thermal bond between the
PEX and aluminum. Testing
indicates that the collector performs at 84% of and all copper
commercial collector at about 1/7th the price.
Extensive build, testing, and
performance information is provided... |
|
A $1000 solar water heating
Gary
This is a cut at a system that performs well, lasts a long time, and is
easy to build. |
 This
is a cut at $1000, cold climate, high performance, long life, low
maintenance, and easy to build solar water heating system.It combines one
of the two collector designs just above with a very simple drain back
scheme. A unique heat exchanger that is inexpensive and very efficient
is used. |
| Modified
Trickle Down Collector (MTD) Richard Heiliger's detailed descriptions of the two versions of MTD collectors he built ...
|
 These
are two new versions of the Thomason Trickle Down Collector from
Richard Heiliger.They use less expensive materials, are easier to build, and are likely to be more efficient. 
Version 2 This design uses all metal construction with a felt coated metal absorber, and a metal frame. The emphasis for this design is on high durability and long life.
Both designs are well thought out, perform well, and are described with
great "how-to" detail (more than 80 pages of construction detail all told). |
|
Solar Heated Livestock Watering Stock Tank Prototype
Gary |
 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. |
|
Optimal Solar Air Collector Design
Gary |
 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 -- Harpiris Energy
Detailed information and manuals for SunCache:
SRCC OG-300 certification results for CA zone 3:
This design was developed by the Davis Energy Group in an effort to lower the price of solar water heaters. The unique design allows more use of plastics resulting in a lighter and less expensive design. |
 This
is a soon to be commercially available, low cost, Integral Collector/Storage
solar water heater.The retail price for DIY installations is estimated to be $2200. The
collector has been SRCC certified, and will qualify for incentive programs
that require SRCC certification. There is a CARB program that CA
residents may want to check on. Note that the freeze tolerant temperature for this collector is listed as 20F, so it is not intended for cold climates. The testing indicates a savings for about 75 therms of NG per year for a family of 4. |
|
A unique solar water heating design using flexible
tubing compressed between absorber plates
Full details:
|
This new design uses silicone tubing that is compressed (squashed) between
two aluminum sheets. This is a unique approach to providing a good
thermal connection between the water carrying tube and the aluminum absorber
plate.
|
|
Double Play -- An Experimental Solar Heating and Cooling System Steve Baer www.homepower.com and the Zomeworks site
Roof Integrated Solar
Absorbers: The Measured |
Roof Integrated Solar Absorbers Home Power magazine article, issue 102 This innovative system uses
unglazed collectors that are in 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: 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
|
 A
new idea for low cost, high temperature solar collectors. |
|
Simple Pool Heating
Idea
Gary |
 This
is an idea for a simple, cheap and efficient homemade pool heating
collector.
|
|
Solar Shed for Space Heating House
Gary
|
 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
|
 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. |
|
Combined Solar Collector and Window Shade
|
 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
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) Gary
|
 An
experimental idea for heating barn or workshop spaces.
Inexpensive and easy to build (honest!).
|
|
Solar Water Collector from CPVC Pipe
|
 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)
|
 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: http://aesop.rutgers.edu/~horteng/ |
| Solar Closets and Sunspaces Nick Pine and Paul Bashus http://www.ece.vill.edu/~nick/solar/solar.html
|
 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 www.voltscommissar.net/ ... .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. |
|
http://www.tdc.ca/bubblegreenhouse.htm
|
 A scheme to use soap bubbles as insulation on greenhouses (or other
structures) to prevent night heat loss. |
|
Solar Bubble Build www.solarbubblebuild.com/build_images13.php
|
 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, www.IWillTry.org
|
 
Rob's heliostat -- reflects solar light and heat into a window in your
house. |
|
Inflatable Heliostat Download full report pdf (3.5 mb) Mithra and Gary |
|
|
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)
|
 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 oikos.com/library/papercrete/sandshouse.html www.papercrete.com/papercrete.html
www.northcoast.com/~tms/papercrete.html
|
  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, John
|
 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 |
| Interesting New Projects | |
| Drake Landing -- Community
with Solar Seasonal Storage for Water and Space Heating
Brochure: |
 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
|
 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
http://www.eebt.org/Trombe.html
|
 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 http://www.invisibleheating.co.uk/road-energy.htm
|
 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 http://www.magenn.com/index.php
|
 An
interesting idea for a helium inflated wind generator. |
| Night Sky Roof Water Spray Cooling
system www.pnl.gov/TechReview/whitecap/whitecap.html EERE report (pdf) http://www.davisenergy.com/NSFS10060.pdf The first link above provides the most complete design information, and
describes three different roof spray system designs. |
 "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 squarefoot 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. |
|
Solar Thermal Electric Power Plant http://pesn.com/2006/02/12/9600234_Schott_solar_thermal_plant/
|
 A
new solar thermal electric power generation installation in Nevada with some
improvements. |
|
MICHAEL JANTZEN Designer http://www.walrus.com/~ddprod/michaeljantzen/index.html
|
 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 http://windows.lbl.gov/facilities/Mowitt/Default.htm
|
 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 |
 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 |
 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
www.energyinnovations.com/sunflower250.html
|
 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:
Article on home CoGeneration: The Marathon Version: Infinia: An assessment of CHP from ToolBase.org: 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 http://www.whispergen.com/index.cfm
|
 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. |
|
Effect of vent
size on thermosyphon collectors ...
Gary |
 This
is a test of the effect of changing the size of the the inlet and exit vent
for a thermosyphon collector.The airflow through thermosyphon collectors is driven only by the buoyancy change of the air heated in the collector, and is sensitive to changes in the collector flow path. |
|
Small panel tests to compare collector designs
Gary |
 This
is a method for comparing the performance of alternative collector designs.
It does not require much in the way of instrumentation, and it appears to produce solid results. |
|
Large plastic pipe coil as heat exchanger
Gary |
 This
is a simple test of the thermal effectiveness of a large plastic pipe coil
used as a heat exchanger in a solar water heating system. |
|
Serpentine Collector Drain Back Testing, Gary
|
 This
is a quick test to evaluate how see how well a serpentine plumbed solar
collector will drain back once the pump is stopped.Basically the tests attempt to determine if a serpentine collector can be used in a drain back system. |
| EPDM Collector
Test
Gary |
 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
Gary |
 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
Gary |
 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
Gary
|
A
try at the Saunders/Delaney/Pine flow organizer. |
|
Radiant Floor Heat Spreader Plates Test
DIY Press to make Heat Spreader Plates Gary |
 A
little test to determine how best to install heat spreader plates for
radiant floors. |
|
Shower Temperature Drop
Gary |
 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: http://www.sunfrost.com/efficient_shower.html |
This
is a cut at a solar water heating collector that offers a combination of
high performance with a low cost per sqft, and an easy build.
tegrated 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!
An
experimental, low-cost heliostat design that uses air pressure to focus and
support the mirror.