Printing Solar Panels

By Kurt Cagle
January 15, 2009 | Comments: 9

solar-panels.jpgSolar power represents in many ways the purest form of energy available to our energy hungry culture. The sun's energy is endlessly renewable (well, for at least the next three billion years or so, at which point, we'll likely have too much of it), produces no greenhouse gases, and is available nearly anywhere.

The problem, of course, is that while the energy is there for the taking, converting that energy into a usable, transmissible form is a considerably more complex undertaking. Solar panels (properly, solar photovoltaic cells) traditionally have been expensive to create, require a fairly significant amount of area to generate meaningful energy and are usually fairly fragile. What's more, most contemporary (second generation) solar technologies tend to be relatively inefficient, converting only between 5% to 10% of the energy directed to them. As a consequence, solar's role has long been relegated to that of secondary power producers, ideal for providing power for an individual house but insufficient for larger uses.

A number of recent advancements in solar voltaics is changing this perception, however. Third generation photovoltaics use several differing techniques that seek to lower both cost and raise efficiency, with a goal towards exceeding the 30% efficiency limits that represent the upper edge of what's possible with second generation technology. One of the more intriguing of these is a novel use for inkjet printers.

In Germany, a partnership of two companies - solar cell manufacturer Roth & Rau AG and inkjet manufacturer Innovalight (or Sunnyvale, California, appropriately) is creating a new generation of silicon based solar cells that are quite literally printed - Innovalight has created a new generation of inkjet printer that sprays specially constituted silicon ink onto a thin plastic substrate, which are then incorporated into solar panels manufactured by Roth & Rau.

This process significantly lowers the overall cost of production of these panels, and because the printed layers of silicon can be made considerably thinner than corresponding first and second generation silicon, the process is able to convert more of the incoming sunlight into energy rather than have it get dissipated as heat.

The first pilot platform, installed at Innovalight, is capable of generating 10 megawatts of power, and the system could readily be scaled upward to generate potentially hundreds of megawatts in a full generator environment, enough to meet the power requirements of a smallish city.

While the use of silicon ink in this respect represents something of a breakthrough, thin film silicon voltaics are definitely becoming a growth industry. In December 2008, First Solar, of Tempe, Arizona, created its own 10 MW plant for use by Sempre Generation in Arizona, and more recently has won a contract to supply additional modules to Masdar City in Abu Dhabi.

High efficiency solar voltaics likely represent a turning point for the technology. Taking up only about 20% of the total area of older generation photovoltaics for the same power generation (and costing far less per MW generated), most contemporary solar installations also include advanced computer intelligence to better manage solar tracking and power generation and are taking advantage of high storage batteries and super-capacitors to store the power produced during the day and even out the power distribution load at night.

What this means in practice is that such solar installations are being increasingly seen as a viable alternative to traditional big power generation not just in high sun areas but even in cloudy regions such as Northern Europe or the Pacific Northwest. Moreover, these installations are more effective in building distributed power grids than large scale (and high cost) natural gas, coal or hydroelectric generators, with fewer of the environmental costs than any of these.

Kurt Cagle is online editor of O'Reilly Media. Feel free to subscribe to his newsfeed, or follow him on Twitter.

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There's a show called Ecopolis on the Science channel (no idea how that works out for non-US television viewers) that covered these new solar technologies. The show is incredibly informative, but be prepared for the cheesiest camera angles you've ever seen.

I also heard a statistic, probably from that show, that harnessed at full capacity, 10 minutes of the Sun's energy hitting Earth would power our current needs for a year.

It's boggling that this technology is so old, yet ostensibly so ill-developed into a mature resource.

This is one of those situations where you begin to appreciate the degree to which materials sciences (now known largely as nanotech) has evolved. The early ideas on solar panels in the early 1970s made use of the then new understanding about semi-conductors, but in retrospect much of that understanding was still very crude and limited.

I think some of the most interesting developments in the field have to do with quantum mechanics. Recent work in quantum biology has found that photosynthesis is in fact a quantum mechanical effect (not all that surprising when you think about it) and that much of the energy transference that occurs takes place because of quantum tunnelling. In plants, this equates to an efficiency of roughly 95%, compared to about 30% for the very upper end of even third generation solar technologies.

The other factor has been storage. Even a 10-15% conversion rate is rather astonishing compared to most other forms of power generation, but solar's weak point has always been the fact that it can only be used only during daylight hours.

Recently, though, you've seen a significant improvement in the area of high storage super capacitors, that are able to store a fairly large amount of power for longer and longer amounts of time. A combined supercapacity/battery system plays a big part in storing power capacity built up doing the day and then releasing some of that during the night.

The final piece is improved DC/AC systems. Most electrical systems were originally built as alternating current systems because they were powered by turbines, in which rotating inductors produced sinusoidal current distributions.

Solar power is a direct current (DC) system. While there's no real difference in power output delivered between DC and AC currents, we still have to deal with the legacy AC infrastructure, which means having transformers that can readily handle efficient DC to AC conversion.

Ultimately, it may prove more beneficial (and have fewer points of failure) of we could more to a pure DC power distribution system, but the infrastructure costs to do that would be prohibitive. Fortunately, at least for the interim, those transformers are also improving.

". . . if we could move to a pure DC power distribution system . . . "

I thought a DC distribution system more-or-less unworkable, because of the losses incurred in transmission. Isn't that the reason Tesla/Westinghouse's AC grid beat-out Edison's myriad local DC generating stations?

There were a combination of factors there, not least being transmission losses, and once this standard was set, inertia carried it forward. From what I understand, and I'll admit to not being an expert here, there have been significant improvements on both AC and DC transmission since then, to the point where a DC system could in fact prove viable, though again economically its unlikely to happen just given the prevalence of AC systems worldwide.

Kurt, Great post. I've been looking into third generation solar panels myself recently, but I'm glad you mentioned the companies involved in the process. I've done a Life Cycle Assessment of current 2nd generation solar panels and here's what I've discovered: It turns out that it requires 18 raw materials to manufacture a solar panel, and along the way production of a standard silicon-based solar panel produces 40-55 grams per kilowatt-hour of CO2 during the manufacturing time. This does not include the amount of fresh water used, CO2 from chemical processing or transporation, etc. Although an average solar panel lasts up to 25 years, it can capture up to 20-30% of the sun's energy and produces 9-17 times more non-polluting energy in its lifetime then used to create it, they're currently deemed as hazardous waste. This is due to high lead content and lack of recyclable materials. It's also estimated that by 2020, this developing industry will produce a growing PV waste stream. So, obviously things need to change, especially in terms of production and materials. Keep reporting the good news - because we really need new energy and it needs to happen quick. - Lee

I wasn't aware of the fact it goes 9-17. that's awesome. So why don't people use them more often?

I just read an article about putting solar panels all over the Sahara desert which could provide enough energy for the entire planet. If only goverments really cared.

i want to know, how can i do ?

Yes, I agree to Mr. Kurt Cagle. Solar power generator is a widely use equipment that is environmental friendly. I want to have an equipment like this in a near future so that I can contribute in removing pollution in our world.

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