Mirrors to increase the power of solar panels?
Does anyone use mirrors to increase the power of solar panels?
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You should be careful with mirrors - they can easily "fry" your panels.
PV efficiency lowers with temperature, while solar hot water may boil in the panels if the mirrors add energy faster than the pump can move the water. |
Not mirrors per se, but my wife recently saw a YouTube video in which the Canadian homeowner stood his ground mount panels straight up in wintertime to take advantage of the strong reflected light from the snow to help compensate for his very northern location.
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It is well to get some extra high-temperature resistance in any ancilliary hardware, but the panels themselves are fine with heat, except for the reduced performance. So, output does not go up linearly with extra light unless you can maintain the temperature. This is not usually too difficult, so I'm surprised it was not used more when sun trackers were cheaper relative to panels.
There is one legend about the DOE getting a notion that it might be nice to have some standard component that would produce both heat and electricity. They shopped this idea around to the energy experts, and several oil companies were persuaded to try meeting the specs. After all the budget was allocated, a little company in Boston pointed out that they had been producing such a device for years. It was just a glazed box to collect hot air, but the sun also hit mylar cones surrounding solar cells. |
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To name a few... The output of a panel is related to something like the cosine of the angle of incidence. As the sun moves the output changes. You can keep the angle perpendicular with a two-axis sun tracker. If you try to use mirrors, how are you gonna arrange them? How are you gonna track the sun? A small change in incident angle decreases solar output by a small amount. But a change in the angle incident on the mirror can cause the energy to miss the panel entirely. Even a partial miss can decrease output dramatically. Then there's heat. If you've ever tried to start a fire with a magnifying glass, you have seen the effects of concentration. Somebody has to keep the mirrors clean. Mirrors work great when you have a bunch of them actively tracking and projecting/focusing the energy on a small boiler high in the air. |
I saw this video a few days ago, which basically agrees with what is said by others. Not really worth it.
YouTube video on using mirrors with solar PV panels. |
I've been thinking about this: The main problem with increasing PV output with mirrors is the penalty of additional heat.
I'm no expert, but PVs only convert certain wavelengths of light into electricity, and infrared (=heat) is not one of them. Also, each materials reflects certain wavelengths better than others. So, are there "mirrors" which reflect visible light but not heat? What materials could be used for this? |
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I'm strugglign to see how you could position mirrors to reflect onto panels that are on a roof facing upwards?
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At my lattitude the winter sun is barely over the southern horizon. To be at 90 degrees to the incoming sunlight my panels are mounted almost vertical on my south-facing wall. The ground slopes away from my south-facing wall. So the sun hits the slope to the south of my house and is reflected up onto my solar panels (tubes).
In a location where panels have to be mounted on the roof it would be much more difficult to refect additional light onto them. |
What about mounting the mirrors above the solar panels, facing down?
In such a way/angle that: - when the sun is low in the winter, it hits the underside and reflects to the panels, - when the sun is higher in the summer, the mirror partially shades the panels, helping reduce the risk of overheating. They could also be mounted vertically on the sides, focusing the sun from due south in the winter, but shading due east and due west on summer mornings/evenings. |
That sounds a good approach, if the mirrors could be mounted safely and firmly so they were not converted into a kite in the first high wind. Not impossible by any means, it would just need a bit of care.
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For 1 reflecting more light on solar panels voids their warranty. 2 unless you can reflect the light over every single cell you won't see any increase in output on traditional panels.
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After looking into it my idea is to enclose my pv array in a fenced in area with it’s inside walls painted white to “brighten” up the area.
A Mirrors reflection will cause a hotspot on the panel that over time could likely damage it. Using a softer reflective material like the white Tyvek ( very reflective ) or say flat white painted plywood would be safer (cooler) and likely still boost the lumens. I’ll test this theory using a diy Tyvek reflector this summer then test again in winter to compare in different temperatures. A 20% gain in the winter would be a big win |
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