Heliostats - reflect sun into your home for cheap heating

Samd

Samd

10 MW
Joined
Jun 28, 2011
Messages
3,750
Location
Ballarat, AU
I often get asked about whether solar panels are a good way to heat the home. As a result I'm always explaining that it makes little or no sense to convert solar energy to electricity and then to radiant heat given the losses at every step, so less than 15% efficiency is likely overall.

Heliostats however are a cheap way to beam the sun straight in.


Simple version:
http://www.iwilltry.org/b/projects/build-a-heliostat-for-solar-heating-and-lighting/

A whole forum dedicated to DIY Arduino based self adjusting units:
http://www.cerebralmeltdown.com/heliostatprojects/

And a small commercial unit (I recently purchased one) in order to get into it:
http://www.homeheliostat.com/

I'm about to move on to building a large unit using a reflective mylar blanket (ebay survival blanket) spray glued onto a plastic corrugated corfulte/correx panel to see if it works.

Hope the topic is interesting to someone...
 
yep, i like the idea of using mirrors to reflect natural daylight deeper into a structure for natural light.

using tracking heliostats is more difficult. but i found some mirror panels from a three mirror door bathroom vanity mirror and used the doors to reflect light into my basement on the north side. i have the mirrors hinged off the bottom of the basement windows so the light can enter through the over head skylights and is reflected into the basement. is is so amazing to get so much light inside from just a mirror.

i also have a gate on the end outside the carport next to the northside and i put a sheet of the foamboard with mylar on one side so it reflects light down the carport when the sun is low in the morning, deep in the winter when the light is needed most. that puts a ton of light into an otherwise really dark area on the north side in winter. summer is less of a problem.

i am a real believer in using direct solar sources and not having to use pv panels for the energy source.
 
There seems to be a lot of cheap second hand satellite dish actuators around one ebay these days, with people setting up manual pc controls.

I saw one guy using an old battery drill with some all threaded bar stuck in the chuck and a nut secured to the mirror board for a linear actuator - now thats a cheap solution.

I've been working on a cheap pc driven one using an old laptop inside my shed, with one of these to control:
http://www.pololu.com/catalog/product/1350

and six of these MG996R metal gear servos:
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6221

To give me a total of three smaller lightweight mylar heliostats that I can fix to my shed wall, and remotely control from a second pc inside my house.

Nice idea to mount your driveway reflector on a gate - you could swing it during the day with an actuator...
 
i figured it is easiest to do it manually. the biggest problem with big heliostats is the space needed. i am stuck here with a 50x100' lot from the 1905 plat of the city here. every square inch of my lot is already filled with house or driveway or carport or garage. i already cover about 2,800 sqft of my lot and my woodshed is about another 400sqft.

so i just tried to use the available options. my carport covers the basement windows on the north side so the ability to reflect light inside the carport and into the basement makes 100% difference in the available natural light in the basement. putting the skylights into the carport roof was the biggest thing i did.

i bot two more of the 46"x76" thermopane units for $40 on CL and am thinking i should use them for two more skylights to go with the 4 i have now, but instead i am gonna use them to replace some large single pane windows on the back porch to reduce the heat loss there in the winter.
 
Sounds really cool dnmun. You should post some pics...
 
I live in the city. I have a south facing back porch. I installed Low E passive solar glass(Lowe 179). This glass has only 2% transmission loss and that is much lower than Low E sold in your local home improvement center. It supplies 40% of the heat for the house. The only reflector I have is the snow , that reflects extra light into my southern facing windows. I am on a budget plan with a gas bill of $25 a month and about $10 is service charge. I will get rid of the rest of the bill with a pellet stove going online this winter and a pellet mill being built so I can convert saw dust , leaves and pine needles to pellets.
 
Still working on this. 3d printed some parts that mount into 90mm water pipe set vertically. Two servos and a 6 port 20 dollar controller (three heliostat capable). With an old laptop to drive it. Might build my own cheap solar concentrator station!
IMG_20130416_074959.jpg

Reflector made from $2 mylar sheet glued to the edges of a square aluminum frame and placed under a slight vacuum to focus. Can't wait to build the rest and try it out!
 
so the mirror is mounted on the white patterned block and the black motor inside there is adjusting the azimuth and the mylar mirror is mounted to that patterned block? and it rotates in the pipe and the pipe is mounted vertically out in the open? i think i follow it. this looks way over the top cool already.

how do you hold the mirror to start with but how to do the tracking is another. are there canned programs that will make the daily adjustments of azimuth and follow the sun up and down during the seasons?

how does it rotate in the pipe?
 
IMG_20130416_211912.jpg
This assembly sits inside the white tube plug in the first photo I posted yesterday. Its a standard pan/tilt turret config for holding cameras and the like found in robotics, but this is a tough but cheap design to bring the cost down. The final design will have screws to stop the plug rotating inside the tube.

I've printed my 76th model today for fine tuning and moving material around to make it durable/fit precisely. "Make a heliostat they said. It'll be fun they said". Better see this through.

The controller is 6 ports so I could control 3 heliostats from it (two each for pan/tilt).

There is a standard spreadsheet I have that maps sun's two angles vert/horiz then I plan to use some other code in the spreadsheet to take the average and position the servos (which are metal geared motors with position feedback).

The mylar is a 2 dollar 'rescue blanket' from ebay mounted to a square aluminium frame and vacuumed flat from board on the back. Well that's the concept.

Will keep you posted....
 
Some testing video...
http://www.youtube.com/watch?v=46kHioYJfaA
 
There are similar projects with many variations on the website http://www.builditsolar.com

I would recommend considering the solar hot-air collector, where the heated air circulates into your home. The hot air panel can track the sun, and insulated flex hoses (like the exhaust of a clothes dryer) can direct the in/out flow. The backplate of the solar hot-air collector was black-painted aluminum corrugated sheet-metal. The cover was glass or polycarbonate (because of the high heat). Cheap and easy to build. Another project used a PV-powered fan, when the sun was shining, the fan was blowing.

One of the projects was quite large, and it got so hot it was used to roast coffee on a commercial basis (a green energy powered garage-run small company). Just a thought...
 
Yeah the static solar collectors are a project for my shed wall. I accumulated several hundred soft drink cans only to recently discovered the design made from aluminium fly mesh is cheaper and more efficient. Doh.

The heliostat has different applications in some cases - I'm using mine to direct winter sun to fruit trees in an unused corner of the garden.
 
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