Stirlingengineforum.com

Tucson, AZ is the perfect loc. to utilize the sun to heat a Stirling Engine. Has anyone researched the problem of manufacturing a heliostat device for a reasonable price? I'm new to metalworking but have been a problem solver, home auto mechanic, installer, etc. for 40 years.

Hi pj, I was just thinking of this problem today (for a solar water heater. Here just north of the 45 parallel, there is quite a difference in sunshine hours winter to summer, so I was thinking about the different tracking speeds that would be required. I was wondering whether I should have continuos tracking, or should it move say hourly, if the latter it might be easy to set the different times, but I'll have to think a bit more on the subject. Might have to find an astronomer, they use tracking gear on their telescopes. Ian S C

Hi guys,

I'm into astronomy.
If you want to track the sun, a equatorial mount would help you a lot.
To be clear on the matter, speed summer or winter is the same. Only the position of the sun is a bit different in height.
For a few bucks you could buy such a mount. With a bit of luck there even is a motor to track the sun. If you'r a bit handy you could use the energy of a Stirling itself to provide the power to run that equatorial mount.
Using a reflective parabola the rays of the sun could be pointed at the engine's displacer cilinder . The power of these focused rays will give enough heat to run a small Stirling. I've seen some working models on youtube.
Hope it helps..

Chris
http://telescopemaking.be/forum

Check out http://www.redrok.com/main.htm. This is all about heliostats.

One idea that I quite like can be found at REUK.co.uk look for simple solar tracker concept, no fancy electronics, self powered.
Ian S C

Price is my greatest interest: So please look at a different approach to the parabolic at http://thermosolar.wikispaces.com/home
Such a linear catenary system may concentrate the sun up to X 200.
If you manage to rotate it along a vertical axis you can have a constant concentration on the focus line.

I just learned from the thread about the easy way to rotate using a photovoltaic cell. So that is solved too.
It isn't necessary to tilt the system in 2 directions. Only a rotation around a vertical axis is necessary.
You may put a vertical mirror at one end of the catenary in order to bounce back the lost radiation.
All the above are disclosed in documents that i hadn't the time to put on the above referenced site.
For any question contact me.

George Kourtis

Ian S C wrote:One idea that I quite like can be found at REUK.co.uk look for simple solar tracker concept, no fancy electronics, self powered.
Ian S C

I added a pair of 555 timers to the resistor driving comparator tracker. This allowed me to eliminate the "hunting" in the redrok design, as a cloud won't trigger energy wasting movement. Only when the tracking light sensor has been exposed for more than any specified time (20 seconds for me) will the first 555 trigger the second 555 to create a pulse for a specific duration to activate the drive. The second sensor tells the first 555 to reset its flip flop function and await input from the west pointing sensor. It will not turn east while active, since the sun doesn't back up across the sky. Simple variable resistors control both aspects and can drive either relays or solid state H bridge devices. I also modified my system so that if it was a cloudy day the tracker wouldn't bother. But if the sun comes out for that preset time it will track until the stop sensor is tripped, and then track as normal. At dark, yet another sensor tells the drive to return to face the next sunrise, and shuts down because of the cloudy day sensor. Overrun stop switches and back emf diodes are a good idea. I drive a quad opamp and 2 555 chips off 5V via a 7805.

I thought I'd posted my schematic here before, if not I'll find it and put it up. I think anyone can build one.

R

'Here is a version without 2 of the sensors installed. This is a simple east west version. I know I have one with the quad opamp shown, but I can't find it. This is sized to print to an 8.5X11 in landscape.

If there's any interest I'll keep looking or redraw the 4 sensor version.

R

My solar tracking mirror array or “death ray” as it is affectionately referred to by my friends is actually a heliostat. A heliostat is technically any device that tracks the movement of the sun, but most often the term refers to a device that orients a mirror to reflect sunlight continuously onto a specific target.