Cheap solar energy?

by Stephanie Chasteen on March 7, 2008

polymers_1by2.jpgI spent most of my PhD working on conducting plastics for making solar cells. The idea behind the plastics (or more specifically, conjugated polymers) is that they would be cheaper to make than silicon. They’re not very efficient, but they only have to be efficient enough to outweigh the cost of the substrate that they’re printed on. Conducting plastics can be ink-jet or screen printed, just like making a t-shirt. They’re still a ways out from commercial production though (5-10 years) because of their low efficiency (though this is improving), and also because they don’t last very long. Silicon’s a workhorse that way, it keeps making electricity for at least 25 years. The polymers only last about a year or so… they degrade when exposed to air or sunlight. What a drag. So, they may be a niche application (think temporary installations like billboards) unless that problem is solved.

I’ve written quite a bit about solar energy and its cost effectiveness, and also have a few activities you can use in your classroom on solar energy. You can check out my solar energy writing and activities. If you have any questions on this stuff, post it here — I answer my comments!

{ 2 comments }

Bryan April 11, 2008 at 9:15 am

Hi Stephanie,

I manufacture lampshades domestically in New Jersey. I want to start producing lamps domestically as well but I would love for them to be “green”. The look would be a very traditional line but the electric components would be energy efficient to do my part in saving our planet. I can do it where I use energy efficient components, and the customer can use an energy efficient bulb, but you still need to plug that in. On top of that, those bulbs have Mercury in them, which I believe will cause all kinds of other problems down the road. As I had mentioned to you before, I am totally green on the subject matter of Photovoltaic Solar Power (pun intended), but is there a way to light up a lamp using a solar panel that is not that cumbersome? Also, is there way to wire the solar panel so it can connect to a traditional light socket so a traditional light bulb could still be used. I was looking to light up an lamp using at least a 60 watt bulb.
My vision would be that the lamp would like like any other lamp you are used to seeing, with a wire coming out of the base, but instead of a plug being at the end, a small enough (not to be an eye sore) solar panel would be at the end of the cord.

Thank you in advance for your time and knowledge,
Bryan

sciencegeekgirl April 13, 2008 at 4:53 pm

Hi Bryan,

I don’t know the nitty-gritty electronics behind your question, but can say a few things about it. Realize that I’m not an electronics expert at all — there are probably things that can be done that I’m not aware of.

First, there are two ways you could do this:
1 – Directly convert incoming sunlight to lamp power using a transformer
2 – Store energy from the sun in a battery to be used on demand by the lamp.

I see problems with either method.

METHOD 1 – CONTINUOUS POWER CONVERSIN

You would have to convert the DC power from the solar cell to the AC power required for the lamp. This will result in a loss of power. I don’t know much about these transformers and their losses.

The sun puts out 1000 W per square meter. Let’s assume you lose 50% of the power through the transformer (you probably wouldn’t lose that much) and 90% of the power through the conversion process of the photovoltaic (that’s a reasonable number). So a square meter would give you about 50 Watts. That’s probably bigger than you would want. If the transformer is more like 90% effecient, then you would instead need a panel about 2/3 of a square meter. Even if that’s the size that you want, it would only put out that power when the sun is shining on it full strength (no windows in between, no clouds). So that might work, but you’d probably need at least some sort of capacity to store some energy to smooth out the energy flowing into your lamp, and you’d need a way to stick the solar panel outside, while having it tethered to the lamp. I don’t imagine you’d get enough power just from the ambient room light, but maybe you would, especially if it were buffered by some sort of battery (see below).

METHOD 2 – BATTERY

Probably a more practical way is to have the energy from the panel feed into a battery. This is how many rooftop systems work, they store the energy in batteries so it can be used on demand. This is good because when you want to use energy or light is often when the sun is not shining (nighttime). I don’t know much about battery technology. Those little solar yard lights must have some small battery, not some big lead acid battery, to keep them shining. Still, any battery technology is going to be less “green” than without.

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