Paint for solar cell reflectors

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Interesting idea, but the price of the solar cells is dropping, so it is be coming less and less cost effective to use augmentation methods. Remember, the cost of installation and materials is also a factor. Still, the cost of some white boards around the solar cell might not be too much.

Sunlight peaks in the visible, so most of the heating of the solar cell is there. Chopping out the longwave stuff would be (I'm guessing) a very small win.

One could try to cool the cells from below, somehow, but that's probably not worth the effort.

I buy my electricity from experts who know how to make it. Ditto my cars and my food.

Almost on topic is a lot better than the average post here.

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Sunlight at the Earth's surface may peak in the visible range, but infrared makes up some 50% or more. Don't dismiss the advantage of removing the in frared light on heating effects.

If it is practical for you, making your own electricity is one of the best things you can do for the environment. Also, you can schedule your power c onsumption to suit the availability of the power. Cars can be charged duri ng the peak time, clothes washed and dried, etc.

Besides fixed installations I was thinking about the small fold up cells that hikers and campers can carry. Adding a sheet or two of something like thin white poster board wouldn't add much weight or volume at all and if it gave an extra 20% or more with no downside might be worth it. Those users are already used to having to manually track the sun for max output, so fiddling with a couple of reflectors wouldn't be much of an additional burden.

The problem with reflectors or lenses is that you sooner or later need a sun tracker with all kinds of issues during storms.

As the solar cell cost drops, it is much easier to use sturdy mounted fixed panels. A fixed mounted panel will have a significant output for

On a sunny day (Sat, 3 Aug 2019 17:52:08 -0400) it happened "Carl" wrote in :

If you talk 'hikers' or even fixed setup it all depends on what you want to do with the electricity. If it is cooking, then maybe the most efficient way is to use a Fresnel lens, google 'Fresnel lens cooking' I have some small ones... foldable. Use the heat :-) Could one power a small sterling engine + generator with the Fresnel lens heat?

There is certainly some but the cooler air on the outside of the slats falls away from the box creating some turbulence. The same happened with observatory domes in the passive cooling days when they were painted with the brightest possible white known to man. At night the dome skin would supercool and cold air would drop in through the come slit.

Today we use active cooling and a paint that is still highly reflective but a semi grey looking mix of aluminium and white pigments. It is more or less neutral after dark so that the dome skin doesn't supercool.

This is nonsense. I have done this with solar cells and at the ambient temperatures prevailing in the UK ~10-20C you can pretty much double the output of a solar cell by placing it at the base of a hexagon of mirrors pointed at the sun ie. \_/. Such devices have been sold in the past for solar battery chargers since a factor of 2 improvement is worth having.

It is easy enough to do the experiment on a small or larger scale. The only snag is wind loading of the contraption and the need to point it at the sun more accurately for the mirrors to have maximum benefit.

Active cooling is essential if you try to push it any further than that even in the UK. I did once push a small calculator PV device with a 10x flux concentrator made out of two parabolic cylindrical mirrors with the focus of one at the base of the other. This excerpt is free access:

So you don't grow any of your own fruit or vegetables?

It has already been done. They tend to break with rough handling though.

Aluminised thin mirrors that fold out and lock in a hexagon. It gets you about a factor of two improvement if you keep it roughly pointed at the sun. It isn't that hard to DIY a suitable folding mirror arrangement.

Almost certainly since you can power some of them off a cup of coffee.

This is a particularly nice example with the large cylinder made of acrylic so you can see the large piston going up and down too.

Mine was made out of a piece of offcut mains gas pipe. They are cute but a bit tetchy to get working for the first time. Ice cubes on the top and fresh boiling water underneath is my choice of heat differential. It would work on a smaller difference if I gave it a good clean and relubricated it.

Tracking doesn't often pay back the additional complexity. Being able to adjust elevation to allow for the sun moving along the ecliptic in steps of 20 degrees is usually worthwhile if not mounting them on a roof.

And in the UK pointing them slightly East of due South is advantageous since fair weather clouds appear frequently on summer afternoons.

The ability to change the tilt is especially helpful if there is a possibility of snowing. When the panel is in a more upright position to better follow the winter sun,, snow will also easily slide down from the panel. Having snow on the panel would reduce electricity output :-) and in several tens kilograms of snow on the panel would be hard on the panel and support structures.

If a lot of snow can fall during the winter, mount the panels that the low end of the panel is sufficiently high from the ground so that the

of the panel.

t things you can do for the environment.

Power stations occupy a tiny percentage of our environment. If everyone diy ed power they'd take up far more total area. If you want to improve the env ironment, plant some food producing plants or build a house.

the power. Cars can be charged during the peak time, clothes washed and d ried, etc.

ll designed there is not much point for home users. More suited to massive loads like aluminium processing.

est things you can do for the environment.

iyed power they'd take up far more total area. If you want to improve the e nvironment, plant some food producing plants or build a house.

What does that mean, "build a house"? How does that help?

of the power. Cars can be charged during the peak time, clothes washed and dried, etc.

well designed there is not much point for home users. More suited to massiv e loads like aluminium processing.

Again, what do you mean about "professionally run power systems"? The poin t is solar power eliminates the carbon released by fossil fuel based power generation. The problem is finding ways to replace the fossil fuel when th e sun isn't shining. Not really a hard problem to solve. It's actually mo re an economic issue, getting the cost down... or accepting a higher cost t o accomplish a goal.

Some seem to think releasing carbon into the atmosphere is a good thing.

Added heating seems like a bad idea. An off-grid buddy of mine had ~50% of his 11kWs of BP Solar panels fail after ~7 years' service. They fail 'open' because the top-side metalization delaminates, which I've also seen in two panels personally. I suspect thermal cycling is the cause, but haven't any proof.

Cheers, James Arthur

Solar and wind economics depend on projected lifetimes. They are dominated by capital and maintenance costs. If the lifetimes don't meet expectations, the economics goes to heck.

Offshore wind will be especially interesting. The sea is brutal and maintenance will be very expensive.

best things you can do for the environment.

diyed power they'd take up far more total area. If you want to improve the environment, plant some food producing plants or build a house.

it improves the environment. A house on land is more useful than unused lan d. Your ideas of what improves the environment are so disconnected from realit y that you propose things that would in reality harm it.

y of the power. Cars can be charged during the peak time, clothes washed a nd dried, etc.

e well designed there is not much point for home users. More suited to mass ive loads like aluminium processing.

The large system that supplies most domestic mains sockets

sed power generation.

it's more complex than that

shining.

how is that a problem? In reality I mean

, getting the cost down... or accepting a higher cost to accomplish a goal.

Well it has been so far. It's saved vast numbers of lives. Billions.

NT

Land is never unused. Unless there is no wildlife there at all.

It's an incidental feature of the move to a more energy intensive economy.

We've worked out how to get that energy with burning fossil carbon and dumping coarbon dioxide into the atmosphere.

As long as we weren't dumping much carbon dioxide into the atmosphere it didn't matter, but the CO2 level is now up to 410ppm, from the inter-glacial norm of about 270ppm, and it is making a difference to climate all over the planet.

It isn't showing any signs of starting a population crash yet - more droughts and occasional poor wheat crops haven't yet been unmanageable - but it certainly has the potential to kill billions.