Solar Paint

What if, instead of fussing around with installing solar panels on your roof, you could just paint your house with solar paint that generates electricity without the silicon integral to photovoltaic panels?

Fiona Harvey, in a story that appeared in the June 19, 2007 Financial Times, wrote that this paint is currently being developed by several different research groups.

She interviewed Sir David King, the UK government's chief scientific adviser, who told her, "I think solar paint is very interesting."

King recently singled out the technology as one with great potential to reduce the "carbon footprint" of buildings.

Ted Sargent, one of the leading investigators in this field, asked, in a CBC interview, "What if every surface was solar?"

Indeed.

Here's Mary Wiens's interview with Sargent.

Solar Revolution: Solar Paint

Ted Sargent is a pioneer in solar science. He's working on solar technology that could literally be woven into every aspect of daily life, from our clothes to our roads, using what is known as a spray-on solar cell. The implications for our energy systems are profound. As Ted says, "Solar energy is not just an exciting science problem, but an incredibly important human problem."

Ted is working on solar nanotechnology with the potential to make solar energy very cheap and allow society to collect it on a huge scale. Currently, solar technology costs more to build and install than most people are willing to pay. Solar panels, for example, the technology most commonly associated with solar energy, are installed on your rooftop. The cost of collecting one kilowatt per hour of solar energy (about a third of the electricity an average household uses on any given day) is about $11,000.

Not only are panels expensive to install, they capture only the visible portion of the sun's rays so they work only on sunny days. Ted's focus is the infrared portion of the sun's rays which accounts for more than half of all solar energy. What's more, infrared energy is available to us even in cloudy weather.

As with so many eureka moments in science, Ted's came while he was working on something else. He wanted to develop a camera that could see in the dark and was working on a sensor to measure infrared rays.

One day in the lab, a graduate student shone an infrared light on the sensor and watched it convert the energy from that light into electricity.

"The graduate student who was working on it came into my office," recalls Ted, "and says, 'looks like we've got a photovoltaic... something that can really do power conversion.'"

Together they began exploring the significance of their discovery. "Because there's something about infrared colors that's intangible. They're colours you and I can't see, so we don't necessarily appreciate them, but we recognize that half the sun's energy reaching earth, in fact a little more than that, is invisible to us. 'Infrared' means beyond red, so it's beyond what you and I can see but it's just as real as anything, any other source of power, and if we don't tap into it in our solar cells, then we throw away more than half of the sun's potential energy we could be using."

In fact, the potential is almost unbelievably huge. "Another way to look at that," says Ted, "if we could capture all the energy reaching us from the earth in one hour and turn it into electricity we could power the earth for a year."

Current technology captures only a fraction of that energy. Even the best plastic solar cells available capture only 6 per cent of the sun's radiant energy, none of it in the infrared spectrum. By focusing on the infrared portion, Ted is hopeful that new technology based on his research could someday capture up to 30 per cent.

The secret is "quantum dots," particles made from semiconductor crystals. They can be tuned to absorb particular colors of light, dots so tiny they can be dispersed in a solvent and then painted onto something else - a house, a car, even a sweater. Sargent imagines clothing that could be used to charge cell phones and laptops, electric cars powered by a solar cell on the roof or roadways covered with solar cells. "If only we could find a way to coat those kinds of structures," says Sargent, "to make building materials or paving material out of solar energy converters, we would have a massive resource we could then tap."

Ted figures the first practical applications of this research could be on the market within a decade but he's reminded almost every day by headlines about rising fuel costs and climate change that the solution is urgently needed.

"We're part of a race," he says. "We're running out of fossil fuels, and the cost keeps going up, and even if we're not worried about that problem, the deleterious prospect of using those fuels affect us every day. It's at the front of the newspapers. You can't help but think of the implications for the natural world, the implications for civilization, to capture the sun's rays in abundance."

That sense of urgency is echoed in Ted's conversations with his graduate students. "The passion that the PhD students and post-doctoral fellows bring to this work is remarkable," he says. "They're working twenty hours a day in the lab in order to get there."

And they push one another. "These kinds of considerations," says Ted, " how to get efficiency up, can we get another factor of 3 doing this, another factor of 10 doing that," are part of the talk during coffee breaks. "And every now and then in one of our meetings where we're making systematic progress towards this goal, I'll say, 'listen guys, this is great, and we're optimizing, but we need a revolution here. We need something to take us to next level.' Sometimes the grad students will say, 'Well, that's true but we just got a factor of 3 through systematic optimization over the last week. If we can give you another factor of 3 two times that's a factor of 10 and you know, that's a revolution. It's constantly on our minds."

That's not the usual chit-chat the rest of us have over coffee. But Ted says the work has changed him, and changed his experience of standing in the sunshine outside the John Galbraith building on the University of Toronto campus where he and his colleagues work.

"You go outside and stand in the sun and it beats down on you," says Ted. "I mean it's incredibly powerful. And you can't but wonder, surely there has to be enough energy there for something as small as the earth. And indeed there is. And it's been powering life forever. This is our only energy source. It's the sun that feeds plants that ultimately feed us. Clearly it's power is vast. And one that's largely untapped. And as scientists and engineers, it's incumbent on us to make sure it's something we can tap into that's practical."

Ted is convinced that when those problems are solved, solar energy will simply overwhelm our current reliance on conventional fossil fuels or nuclear energy. "Abundant, free and clean," says Ted. "Why would we do anything else. Well the answer is we haven't yet engineered our way through this. The limitations today are technological and ultimately that means they're human. And that's what engineers do. They break assumptions."

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Prefer to watch or listen to the interview?

No problema.

There a link to a video between the second and third paragraphs of the interview.