Crazy? mirror scheme

[desperate]

One last try..........

get hold of a copy of a copy of "Solar power" by J. C. McVeigh of brighton polytechnic Pergammon Press


all sorts of discussions about double cusp, sea shell, double parabolic, and various arrangements that work without trackiing as CS panels with ratios from 2:1 up to 10:1, it's a good read if a bit outdated.

[StBarnabas]

Hi Eric
I think this is more what you want. the previous contour plot was solar elevation.  The one below assumes the heliostat is due south of the water panel and 30 degrees below the panel. The light has to leave the heliostat at an a elevation of 30 degrees - of course it may well be different for your topology. What is plotted here is the normal angle - a flat plate will be 90 degrees to this.

[ericw]

Sean,

Yes that picture makes analysis much easier. I think that 30 degrees from the panel to the mirror is reasonable, if the mirror was any closer you would start to loose out because the reflected light would be striking the tubes at an angle too far away from the normal.

The problem arises with the maximum angle of tilt 45 degrees would be nice and would cover a large part of the day in summer. Unfortunate this would mean the 'high' edge of 2m square mirror would be 1.4 meters above the roof (rather more when tilting in the N-S axis is added) I feel that this is getting rather high both from the asthetic point of view and because the garage roof is not really that far below the panel it would overlap the bottom of the panel. 30 degrees might be possible but the gain would be much less.
If the mirror was at ground level I might get away with it but in an urban environment it would almost certainly suffer from excessive shading.

I'm coming to the conclusion that although it might not be as crazy as some things that have been advocated in the past on the forum it is unlikely to be practical proposition.

Many thanks for the sterling work on the calculations it certainly made things much clearer.

Desp
I will look up your references but I suspect they may well end up requiring a complicated shape or large area mirror.

[StBarnabas]

Eric

I understand the difficulty, the other problem of course is that unlike when you are directly tracking the sun it is more difficult to arrange a servo to lock on and adjust for errors. Shame it would have been really nice to implement such a system.

Regarding the calculations, no problem. I am still using your PIC one wire HalfBee slaves extensively. Indeed there will be considerable activity on that front over the coming months.

Sean

[echase]

I asked my supplier about this as I was thinking of painting a nearby wall white to reflect a little more sun. They said the flat plate collector was not specified to take more sun that standard UK sun so did not recommend it. I guess it OK if the pump is running but in the event of failure the panel would be damaged by the extra temperature it would reach.

[langstroth3]

Interesting thread, although can't say I understood it all. Many of the thin reflective strips between my Navitron tubes got bent with cats walking over the panels (!), and the snow last winter. So I took all the reflective strips off in the spring. I'm not sure whether it's made any noticeable difference, I've not crunched the data logs to check yet.

Logic says though that I'm not using the radiation that falls between the tubes, and isn't reflected back any more ?