# Transparent solar panels?

## Main Question or Discussion Point

Transparent solar technology represents 'wave of the future'
https://www.sciencedaily.com/releases/2017/10/171023123526.htm

Date:
October 23, 2017

Source:
Michigan State University

Summary:
See-through solar materials that can be applied to windows represent a massive source of untapped energy and could harvest as much power as bigger, bulkier rooftop solar units, scientists report.

So, skyscrapers with windows made from this type of panel would be practical? Eventually would be practical? Will never be practical?

Last edited by a moderator:
DrClaude

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Thanks, mods.

jedishrfu
Mentor
The article said they are currently at 5% efficiency vs 15% efficiency of traditional solar panels and will become more efficient over time although it seems that 15% is perhaps the maximum achievable efficiency.

This chart shows the variance in efficiency numbers but its hard to say how truly efficient they are considering how companies will inflate it to compete better. Over time the efficiency drops as dust obscures the panel or the glass and you'll need to keep them clean. This article below says from 20% to 25% to 50% efficiency loss when panels are dirty.

http://www.solar-panel-cleaners.com/why-clean-solar-panels

The big problem will be convincing folks to change out their glass and how much in energy costs they will save. this may need a govt subsidy to get it going.

Sounds right, "bottom line" before "what makes sense".

anorlunda
Staff Emeritus
http://www.lightsonsolar.com/solar-basics-kw-and-kwh/

The link says 20 watts per square foot is typical of traditional panels. If we divide that by 3 as @jedishrfu said, we get about 7 watts per square foot. A 3x4 window is 12 square feet, so about 84 watts per window. For 5 south-facing windows per house, that is 420 watts, pretty good.

Given an average of 5 hours per day of full output, that is 2.2 kWh/day, which at $0.15/kWh saves you$0.33 per day. That assumes an unobstructed view of the southern sky. But in the future, you may save 10x that amount.

Nearly 50% of the US population lives in multi-family dwellings. For a high-rise south-facing apartment with much smaller window area than a house, perhaps 150 watts total, or \$0.11 per day. For an apartment on a north-facing wall (in the northern hemisphere), nearly zero.

In the state of Vermont where I live, the solar contractors tell me that they often get calls like this.

Owner: "I'm building a new mountain house and I want to go green with solar power."
Contractor: "Great. You are on the south facing slope of the mountain, correct?"
Owner: "Huh?"​

russ_watters and jedishrfu
jedishrfu
Mentor
For north facing properties they can install a few extra mirrors. :-)

anorlunda
jedishrfu
Mentor
That was a good analysis @anorlunda . I didn't consider the facing direction so much but that's definitely something to worry about. In Texas it seems the sun is always overhead and hot hot hot.

Brings new meaning to the saying of how people shouldn't throw stones at glass houses for fear of creating a power outage.

I wonder how much efficiency will be lost due to dirty windows and how much it will cost to clean them.

donpacino
anorlunda
Staff Emeritus
For north facing properties they can install a few extra mirrors. :-)

Or like this town in Norway that installed mirrors to get some sunlight.

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jedishrfu
jedishrfu
Mentor
Nice, this reminded me of a bed and breakfast in Sedona Arizona nestled in a canyon (Canyon Wren) with very little sunlight except for 10am to 3pm roughly.

One application that would be worth looking into would be greenhouses. The St. Louis Zoo has to feed all kinds of animals, and their exhibits as well, so they have a good bit of greenhouse acreage. Saving even 10% on their electric bill would be welcome. (Rich donor pays for the conversion.)

jedishrfu
donpacino
Gold Member
How transparent are they compared to a typical window?

Also I do not know very much about solar panels in general. Does anyone know if they actually decrease thermal energy from the sunlight?
I'm curious if these transparent panels will decrease the thermal energy delivered from sunlight to the room behind the window. If they do, and the panel is thick enough, one might not be able to rely on sunlight to help heat their houses as much, resulting in slightly higher heating costs?

note: I realize you might not know the answers to these!

russ_watters and jedishrfu
jedishrfu
Mentor
Some folks have used double shelled houses to handle heating. The glass windows are in the outer shell and systems are in place to capture or redistribute the heat where needed.

Here's one example:

http://www.enertia.com/introduction.html

with the addition of the solar glass you could replace or enhance your solar panel energy production.

Some folks have used double shelled houses to handle heating. The glass windows are in the outer shell and systems are in place to capture or redistribute the heat where needed.

Here's one example:

http://www.enertia.com/introduction.html

with the addition of the solar glass you could replace or enhance your solar panel energy production.
Didn't the "thorm wall" system use that concept?

jedishrfu
Mentor
I don't know, I've not heard of the "thorm wall" before.

I don't know, I've not heard of the "thorm wall" before.
It was in the '70s, I was home on leave from someplace I won't ever go back to. B-i-L was telling me that he was going to make the south wall of his house into a "thorm wall". An additional wall of glass would be added to the outside of the house and vents places at top and bottom. The idea was to heat the air and allow it into the house while cold are would be drawn into to replace it. Never happened, but it sounded interesting.

anorlunda
Staff Emeritus
This drawing from the link in #12 explains it well. Today it could be enhanced with computer controlled open/close, and voltage controlled transparency and even transparent solar panels. I once stayed in a hotel in Trondheim with this type of construction. It is a delightful way to heat/cool, but I have been warned that it is very expensive. With all those enhancements maybe double the price of a simple house.

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Noisy Rhysling
sophiecentaur
Gold Member
What would be the effect of one of these panels on the Colour of the lighting getting into the room? This link suggests that the Absorption varies with wavelength and that implies the light that penetrates would be bluish tinted (I think that's the right way round as longer wavelengths are absorbed).
Would the inhabitants accept this colour caste to the lights in all of their rooms?
But it appears from the picture of a panel that there is very little tinting. How is that achieved?

This drawing from the link in #12 explains it well. Today it could be enhanced with computer controlled open/close, and voltage controlled transparency and even transparent solar panels. I once stayed in a hotel in Trondheim with this type of construction. It is a delightful way to heat/cool, but I have been warned that it is very expensive. With all those enhancements maybe double the price of a simple house.

View attachment 214055
If you scale that down to just one wall of a single storey house you have what the B-i-L wanted to do back then.

And thanks for helping me prove I'm not nuts. :cheers:

russ_watters
Mentor
How transparent are they compared to a typical window?
Right. The concept of a "transparent solar panel" is basically an oxymoron. Someone proposed these in a project recently and I had difficulty stifling my laughter, but I managed.

sophiecentaur
For a few years I lived in southern Arizona and the first year my furnace went out. I had good exposure to the sun and decided to look into solar. I called a dealer and described my situation and was surprised by his answer. He said, "It's not worth it. The heating season is so short it's not worth the expense." I thought to myself, if it's not worth it in southern Arizona, where is it worth it. Is there a latitude in the U.S. that has a long enough heating season and enough sun to make solar heating worth it?

sophiecentaur
For a few years I lived in southern Arizona and the first year my furnace went out. I had good exposure to the sun and decided to look into solar. I called a dealer and described my situation and was surprised by his answer. He said, "It's not worth it. The heating season is so short it's not worth the expense." I thought to myself, if it's not worth it in southern Arizona, where is it worth it. Is there a latitude in the U.S. that has a long enough heating season and enough sun to make solar heating worth it?
He may have simply not wanted the job.

russ_watters
Mentor
For a few years I lived in southern Arizona and the first year my furnace went out. I had good exposure to the sun and decided to look into solar. I called a dealer and described my situation and was surprised by his answer. He said, "It's not worth it. The heating season is so short it's not worth the expense." I thought to myself, if it's not worth it in southern Arizona, where is it worth it. Is there a latitude in the U.S. that has a long enough heating season and enough sun to make solar heating worth it?
This thread isn't about solar heating it is about solar electricity.... I have actually never heard of solar being used exclusively for heating. Usually in that context it is for domestic hot water.

russ_watters
Mentor
Given an average of 5 hours per day of full output...
That is a common assumption for properly aimed panels, but for panels that are way off the optimal elevation, I bet it is high by a factor of 2.

anorlunda
Staff Emeritus
That is a common assumption for properly aimed panels, but for panels that are way off the optimal elevation, I bet it is high by a factor of 2.
Good point.

sophiecentaur