How to Double Solar Panel Output for a few Pounds…

Recently I was being driven around by a bus when I noticed somebody’s house, which had two roof slopes, running directly opposite each other (at about 45 degrees steepness). One slope was almost totally covered in solar panels, the other was just roof tiles. Which got me thinking: Why didn’t the owner cover the other slope with metallic paint? (It’s about £30 for 5 litres) OR: (even better, but perhaps not quite as durable) Just: glue, aluminium foil, to the opposite roof slope?

Is there anybody here who can tell me why this wouldn’t greatly improve solar output? From what I understand (about how solar panels work) whilst they can only absorb certain frequencies of light (within the white light they receive) there isn’t really a limit to how much light they can process, barring of course extreme temperatures, causing material failures.

Anyway just thought this could be useful to anyone planning solar panels!!!

BTW: One Reason Why ET Might Not Have Contacted Us…

Installing solar panels in cold climates gives us Earthlings a bad impression, since: If you were ET, and you saw (government subsidised) solar panels in e.g. Britain’s cloudy Yorkshire, and then smokestacks of an e.g. South African coal powered station bathing, in sunlight, you’d think our species was pretty dense; wouldn’t you?
After all if CO2 emissions are bad wherever they occur, and if the point of subsidising solar panels is to get carbon free electricity (for money) then you’d expect countries closer to the equator to represent better value for money (even if it was still in the Western World, e.g. Australia) (coincidentally a country with one of the highest C02 emissions, per person, anywhere on the planet) en.wikipedia.org... (6.8 tonnes, per person, a year, above Russia!!)

Anyway; just a thought.

You can increase solar panel output several ways. Use a motorized tracking system to keep the panels pointed directly at the sun for the longest possible time. You could put mirrors around the edges set to focus more light onto the panel surface. Something that seems like it might work, but I have never seen or heard of would be to put the equivalent of a giant "magnifying glass" over the panel, shouldn't that really concentrate the light? The "lens" would have to me made specifically for the application, and the height would have to be well calibrated so I don't know if it would be worth it or not. Heck, maybe the reason I have never seen it is that the lens might cost as much or more than the panels?

The solar panels have a maximum of efficiency.

Once that maximum is reached it does no good to supply more light. They just need to be made more efficient.

If I get this right you saw a guys House with like a V shaped part of the roof, and he had solar panels on one side only. It really would all depend on where the Sun comes and goes with the best returns. If he only has them on one side for a reason maybe bc the otherside would be a shadow, or if the sun wasn directly above him, even putting mirrors wouldnt help the side with the solar panels because the light would reflect in a different direction horizontal to the panels instead of perpendiculer to the panels. Gosh I hope that makes sense sorry, I work with glass and solar panels.

Originally posted by Shadowalker
The solar panels have a maximum of efficiency.

Once that maximum is reached it does no good to supply more light. They just need to be made more efficient.

The oil companies will never allow a PV cell with more than 20% efficiency to reach market. They have a vested interest in keeping us slaves to oil.

The hotter a solar panel is, the more efficient it operates (more or less) - also, the greater the luminosity, the better the function. At least - this is for -most- silicon solar panels. Some of the newer 'green' varieties may break down under such extremes.

In either case - I recall some of the better solar power systems out there using a set of tracking mirrors to track the sun and then pass it through a lens and onto a small (about three by three centimeter) solar panel - with the mirror system being a square meter or more.

When I was working on our solar car team, we were contemplating using a similar system as a 'dorsal strip' - using lensing to take light from all directions and focus it along a narrow strip of solar panel. Being the perfectionist that I am - I was all for it, and other ridiculously expensive ideas that never made it past "yeah, that would probably work pretty well, if we could afford it."

I have expensive tastes.

Using less power is a much better alternative.Do you really need 2000watts to burn a piece a bread or nuke a can of spaghetti.

Like already stated, solar panels have a maximum efficiency. They can only absorb so much light, so giving them more light than they can handle doesn't do anything.

Originally posted by Aim64C
In either case - I recall some of the better solar power systems out there using a set of tracking mirrors to track the sun and then pass it through a lens and onto a small (about three by three centimeter) solar panel - with the mirror system being a square meter or more.

I don't think they focus the mirrors on a solar panel. They probably focus the mirrors on a small Stirling engine. Or other heat to electricity device.
en.wikipedia.org...

I live down by the Equator. My solar panels generate more energy on cloudy days. UV light is stronger on cloudy days.

Solar Panels need UV light to charge more.


You need to figure out how to increase UV light onto your solar panels, not visible light. Experiment with different paints to find one that reflects UV light. To amplify your Solar Panels.

reply to post by gift0fpr0phecy


It was a solar panel. Photovoltaics are more efficient at higher luminous intensities and higher temperatures, generally speaking. Thermovoltaics exist, but require a temperature difference to function, and are therefor impractical in most applications (not to mention their relatively low efficiency - usually such devices, often a Peltier junction, are used as solid-state cooling/heating devices).

NABCEP certified...for what it is worth????...jumping thou the UNION HOOPS NOW..

What one is trying to do is maximization the exposure to sun light in the visible spectrum. (I have the SUN POWER leading industry source power point presentation, contact me U2U for info or another alternative info i.e. KPMG energy audit), for a given array/panel display). If one could refract additional light/spectrum to be received by the panel, then it would increase the Watts received via panels put back into the Grid-tied system...all depends on the output specs of the panel selected.

The down fall of solar is that YOU/I have to play by THEIR system. It is very important to remember that the ENERGY Utilities are a subsidization monopoly of energy from, you guest it ...our national GOV.

Regards and Nameste,

-Chung

Originally posted by Aim64C
reply to post by gift0fpr0phecy

 

It was a solar panel. Photovoltaics are more efficient at higher luminous intensities and higher temperatures, generally speaking. Thermovoltaics exist, but require a temperature difference to function, and are therefor impractical in most applications (not to mention their relatively low efficiency - usually such devices, often a Peltier junction, are used as solid-state cooling/heating devices).

Friend:

Higher temps = lower outputs. Solar Panels are more electronic than one thinks. High temps equal more resistance.

Solar panels operate at greater efficiency at lower/freezing temperature. this is why one must understand and study the effects of electricity in a system.

Regards and Nameste

Assuming the angles were right, reflecting light from the opposite roof surface would, indeed, increase the potential electrical output of the PV panels. As opposed to some of the responses here, standard PV panels can and do generate higher outputs as the amount of usable light is directed into them.

The limiter however...and again contrary to some claims made above...is cell temperature. Above about 40 degrees Celsius, cell efficiency begins to drop off dramatically.

Various methods can be used to focus additional light onto a PV cell (including tracking), but over a certain concentration cooling becomes an issue. Without getting into a lot of detail here, there are technologies being developed that focus additional light while not allowing unusable wavelengths from reaching the cell itself (which would only have a heating affect).

There is a completely different kind of solar cell available now, known as a triple-junction cell, that is specifically designed to have much higher concentrations of light trained on them. These cells are typically only about 5 to 10 cm on a side (so, very small compared to standard silicon cells).

There are working systems now available, called CPV (concentrated photovoltaic) in the marketplace that use concentrations of 500 to 1,000 suns...and some coming to market soon that will exceed 1,500 suns. For these systems, cooling is definitely an issue...although not because the cells become inefficient at relatively low temperatures. It is so the cells don't burst into flames or melt.

Typically, these systems use something called a Fresnel Lens to concentrate the sunlight. The cells themselves use a much broader spectrum of light than do PV...and so are far more efficient. PV typically runs at from 11% to 18% efficiency, while CPV cells run at up around 38% to 41% raw efficiency.

CPV, however, does not function well (or nearly at all actually) in diffuse light conditions (like cloudy days)...so is very dependent on annual direct light conditions, and must typically use dual-axis tracking systems to try to keep the solar cells at right angles to the sun throughout the day.

Originally posted by mobiusmale
Assuming the angles were right, reflecting light from the opposite roof surface would, indeed, increase the potential electrical output of the PV panels. As opposed to some of the responses here, standard PV panels can and do generate higher outputs as the amount of usable light is directed into them.

The limiter however...and again contrary to some claims made above...is cell temperature. Above about 40 degrees Celsius, cell efficiency begins to drop off dramatically.

Various methods can be used to focus additional light onto a PV cell (including tracking), but over a certain concentration cooling becomes an issue. Without getting into a lot of detail here, there are technologies being developed that focus additional light while not allowing unusable wavelengths from reaching the cell itself (which would only have a heating affect).

There is a completely different kind of solar cell available now, known as a triple-junction cell, that is specifically designed to have much higher concentrations of light trained on them. These cells are typically only about 5 to 10 cm on a side (so, very small compared to standard silicon cells).

There are working systems now available, called CPV (concentrated photovoltaic) in the marketplace that use concentrations of 500 to 1,000 suns...and some coming to market soon that will exceed 1,500 suns. For these systems, cooling is definitely an issue...although not because the cells become inefficient at relatively low temperatures. It is so the cells don't burst into flames or melt.

Typically, these systems use something called a Fresnel Lens to concentrate the sunlight. The cells themselves use a much broader spectrum of light than do PV...and so are far more efficient. PV typically runs at from 11% to 18% efficiency, while CPV cells run at up around 38% to 41% raw efficiency.

CPV, however, does not function well (or nearly at all actually) in diffuse light conditions (like cloudy days)...so is very dependent on annual direct light conditions, and must typically use dual-axis tracking systems to try to keep the solar cells at right angles to the sun throughout the day.

Thank you for this.

Solar is not just putting panels on the roof. There is an actual mathematical science at this time to what can, and can't happen.

Regards and Nameste,

-Chung

Hello all

I own and operate a solar company, and design and manufacture solar tracking systems. The following are a couple of comments on the OP and responses so far.

I don't mean to be disrespectful, but higher temperatures - reduce - solar panel efficiency greatly. It is one of the great issues that affects productivity. In fact, the poster who mentioned that he lives near the equator and gets more power on cloudy days is probably seeing this effect. As mentioned, a solar panel has a maximum output, and once reached, more sun and therefore temperature decreases the output. At the equator you are probably getting sufficient insolation on a cloudy day to hit the peak of your particluar panel.

The OP's original point about relection works in theory, but the main issue is angle of incidence. Snow cover or a relecting pool make a measurable increase in production, but it is low, in the range of a few percentage, but still measurable. The problem with the two roof slope idea is that due to the angles involved very little extra sun would strike the panels, and the little that did would have a very high angle of incidence. The snow cover or reflecting pool has to be right in front of the panels, and really only works close to solar noon.

Concentrating solar systems use a huge mirror surface, say 400 sq. feet to reflect 1000 times the normal solar insolation onto a very tiny triple junction cell, say a few square inches. The cells, which are readily available from many suppliers, produce at about 28 percent installed inthe field. (Sun power produces a regualar polycrystaline cell that is pretty close to 20 percent in the field)

Due to the very high heat in concentrating systems, they usually have a cooling system to cool the cell. A lot of development is going into using that heat to power stirling engine type systems to produce extra power. In southern climates, many of the best systems actually forgo any attempt to use pv cells and just produce heat to drive a steam engine and generate power that way. The main reason is the loss of efficiiencyof pv cells due to heat.

I am in Canada, and my tracking systems produce electricity at a cost of around 4 cents per kWH over 100 years. The key to increasing efficiency is to cool the panels. Cooling is the key to increasing actual power produced in the field. In my case, it was a fluke of our design that we realized only after the fact was making a huge improvement. We only realized that after the systems had been up and running for over a year, and the production numbers were so high. My origianal design goal was to produce a system that would last for several hundred years with a minimum of maintenace. Obviously, the panels and inverters have to upgraded occassionaly to make that work.

Cost per watt is far more important that efficiency, anyway. The mass produced panels that have the best cost per watt to durability ration are regular polycrystaline ones, We are currently paying around $1.80 per watt on average, wholesale, and almost eveyone in the industry is forecasting that to drop to about $1 a watt within 12 to 18 months.

Solar is right now at parity with fossil fuels, although everyone is just waking up to that fact, if you have the right suppliers. Within 3 years or so as we progress further down the peak, solar will pass fossil and nuclear very clearly. It will be common knowledge by then that solar is cheaper than fossile fuels for producing electricity, and a huge switch will occur very rapidly. With 1/10 of the capital investment that has already gone into building either the installed base of Wal-Mart stores or McDonalds restaurants, our society can easily replace all of the 13 Terawatts of power humankind now uses over about 30 years. Enlightened political regions are beginning to invest in solar now to get ahead of the curve.

By the way, every US domestic military base is off grid.

Melyanna

Originally posted by Aim64C
Photovoltaics are more efficient at higher luminous intensities and higher temperatures, generally speaking.

Yeah, I'm certain that is incorrect as stated by others.

I'll go ahead and eat my foot on this one. I was relying on memory from a discovery channel show several years back. I forget what the show was, much less titles of devices. There was a focusing array, and the show stated that the photovoltaic junction became more efficient at higher temperatures and luminosities. Perhaps the show was incorrect, or perhaps there was more to it than I remember (such as the junction being a multijunction photovoltaic, which -is- more efficient at higher luminosities and temperatures -compared- to more generic types; which may have been remembered incorrectly).

Originally posted by sonofliberty1776
The oil companies will never allow a PV cell with more than 20% efficiency to reach market. They have a vested interest in keeping us slaves to oil.

Actually, that’s pap. If the vast amount of investment in solar power cannot get anything beyond a certain efficiency then that’s just the way it is. Appreciate it’s trendy to blame the woes, limitations and realities of “alternative energy” on the oil companies, but when there’s no evidence of the fact it gets a bit tiresome. Like a stuck record.

I think solar panels are more effective if pointed in the direction of the sun. As they struggle to “break even” where I live and their installation has to be subsidised by the tax payer, I would argue that they should not be installed if they are not commercially viable. Which is why they don’t get installed on the “wrong” side of the roof!

Regards

As to a magnafing lens:
Think of sunlight as falling rain. If the lens is the same size as the panel there is no gain. A mirror would do just as well for a lot less money.

Just booking my seat OP, thank you for posting this information. I guarantee it'll come in handy. 2nd ln




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