Making solar energy viable on a big scale

Two thick steel doors shut softly behind me. I’m not locked into this boxy, cell-like ‘quiet lab’ deep in the bowels of Bristol University’s new Centre for Nanoscience and Quantum Information, but it feels like I might as well be. A journalist could disappear here: no sound penetrates, and no one would hear my screams…

A constant stream of traffic drives past the centre, but the springs and dampers upon which this new building has been constructed ensure that very little noise, and virtually no vibration whatsoever, impinges on the finely tuned experiments on nanoparticles taking place in a series of quiet labs all along the basement corridor.

This small lab, however, is the stillest of them all: having been given the tour of the basement, I’m now standing in the quietest room in the quietest building in the world, and I can almost hear my heart beat. Losing all auditory references does funny things to your balance, and I lurch slightly as the double doors open to let me out. It’s a relief to hear the faint underlying buzz that indicates life as we know it.

The key factor

I’ve come to meet Dr Neil Fox who’s going to tell me how sunlight shining on diamonds can generate electricity. It’s theoretically possible, but doing it cheaply and consistently is the tricky bit. The heat contained in the sun’s rays, clearly, comes for free, but the problem with solar power to date, explains Fox, has been the cost and logistics involved in generating usable electricity on a large scale.

Storing the sun’s power tends to be done by using its rays to heat oil or a special salt mixture to a high temperature. This provides a store of heat that is used to drive steam turbine generators just like any conventional power station. Although the principle is sound, the construction and operating costs of utility-scale plants are not cheap.

Nanodiamonds, Fox explains, are one of the few materials that can absorb heat, and, while barely red-hot, emit thermionic electrons. By arranging for this thermionic current to be harvested, electrical power can be generated directly. Job done, it might seem. Well, not quite.

“They’re not very efficient,” he explains, kindly sketching a vastly simplified picture to illustrate for me the problems currently taxing his team. The potential for generating clean power cheaply and easily would be an amazing breakthrough, and it’s the central reason why Fox and his research assistant, Dr Kane O’Donnell, spend much of their lives closeted in a quiet lab in the basement getting up close and personal with a shiny silver scanning probe microscope.

It looks rather like an old-fashioned diver’s helmet. Curious, I peer through a little window into its innards. I don’t know what I’m expecting — given that a nanoparticle of diamond is unimaginably tiny, I’m hardly likely to see anything sparkly, much less an emitted electron dancing around. Images from the microscope are sent to O’Donnell’s computer: auditory and vibrational quiet is essential, he explains, to the accuracy of their results.

“There’s a similar microscope at UCL, but their lab is next to a tube line, so things can sometimes go wrong,” he says with a small grin. “What we’re doing is probing at the atomic scale. It’s like trying to position a needle above a particle at a distance of about an atom.”

The most infinitesimal shake can make the tiny diamond particles under scrutiny appear to jump the nano-equivalent of a continent’s width to the left or right, up or down. To prevent this, the section of the room where the microscope sits is a solid block of concrete several metres thick, which can be suspended on jets of air to isolate it from any noise or vibration. There are no phones in these labs, special non-buzzing lighting has been installed, and the only copper wiring permitted is that required to power computers.

Without this facility, adds Fox, it wouldn’t have been worth spending half a million euros on such a super-specified instrument. But the laboratory environment here allows his team to achieve a precision available nowhere else.

It’s rare, explains O’Donnell, for researchers in the physical sciences to be doing fundamental science and applied science in the same project, but the results of combining their brainpower could potentially make solar energy viable on a major scale. If nanodiamonds can be manipulated to make the cost per kilowatt cheaper, conventional energy companies would be far more willing to invest in solar power.

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