Solar’s future fantasies
13 Sep 2013 lucyejwoods
Just decades before the moon landing, space venture was preposterous science fiction. Submarines and robots were also once the preserve of the fantasists, not to mention the technological miracle now in everyday use – mobile phones.
From automatic doors, deep-sea discoveries, the automobile, air travel and escalators, Star Trek communication fantasies to H.G Wells’ lasers, science fiction leads to real-life innovation. The same is true of solar energy. Who would have dreamt 50 years ago that we would use the sun to produce electricity? That dream is now reality, but what next? Technology deficits in solar energy are all advancements waiting to happen, and some of science’s best brains are already working on solutions.
Here we look at five of the big ideas currently being pored over in the labs and ask experts the million dollar question: how far are these headline grabbing solar ideas from becoming reality?
Using organic cells, nanotechnology is a science enabling multiple manipulations of materials at a microscopic level.
Solar panels today reflect back too much light. Blacker modules are better at absorbing light, which is where nanotechnology comes in; by making microscopic ridges in panels, it increases their apparent blackness and absorption capability, and greatly increases efficiency. Successfully developing nanotechnology could improve module efficiency by up to 80% according to the Braun Research Group at the University of Illinois.
Nanotechnology is available now and being studied, tested and improved. However, the major challenge for using nanotechnology to the benefit of solar energy is getting the two technologies to merge; currently it is very tricky to apply a nanotech coat to a solar panel.
Markus Schaefer, vice president of European PV manufacturers, Voltec Solar, said: “An innovative approach is needed and is still not available. Once the right technology will be
[finalised], it may be the future technology, we hope for very high efficiency and very low cost.”
Also using nanotechnology, solar power may in the not-so-distant future be invisibly embedded in windows, flexible films or paint.
Solar panels requiring expansive rooftops and fields could be relegated to history, as experts shrink solar cells to miniscule proportions and enable then to absorb infrared as well as UV light, greatly increasing their efficiency. Such microscopic technology would allow solar cells to be transparently placed in windows and mixed in with liquids such as paint. Screens, walls, table tops…potentially any surface could be transformed into a platform for renewable energy.
Max Shtein, associate professor of materials science and engineering at the University of Michigan, says transparent solar would address the high installation costs of PV while simultaneously solving the need for a window and solar panel. “You’re also using existing real estate wisely; the taller the building, the better the value proposition,” he says.
The major snags preventing solar paint from lining shelves in the local DIY shop, according to
Shtein, are “efficiency and longevity”. Shtein explains further that if cells lack efficiency “the amount of solar electricity generated might not justify the expense of painting a side of a building”, and if the lives of the organic solar cells expire too quickly, “the expense of re-painting might make it impractical”.
But in commercial terms, Schaefer says solar paint is “without doubt a very attractive market”.
“Because of available surfaces, and the proposed technologies it promises to be very competitive,” he explains.
The efficiency of prototypes currently measures a lowly 5-8%, but two new product lines announced in September from the solar scientists at New Energy Technologies include
translucent solar panels. Shtein estimates a bit longer for liquid solar cells to take off. “It’s at least five years out, if not more,” he says.
Solar cells with multiple ‘layers’ or ‘junctions’ are designed to also utilise different wavelengths of light that single layer silicon misses. Targeting this shortfall is the ‘triple junction’ solar cell. Using three layers of photo absorbing materials – indium, gallium, and arsenide – can hugely magnify efficiency.
The Franhoufer Insititute for Solar Energy Systems (ISE) and semiconductor manufacturer, Soitec, have knuckled down in the labs to go one frontier further and develop a four-layered solar cell made by assembling two dual layered cells, and then welding them together. The gain from such a complex task is the prediction solar cells could reach an efficiency of 50% (for non concentrated light).
Schaefer has predicted multi-layered cells will “definitely take an important market share, but it may not become the largest technology in the future due to highest production price”. The cells are commercially available now, for a few hundred thousand dollars. It will be quite a while before you can grab these at your local DIY store.
Standard semiconductor solar cells use solar energy only to create electricity; trees, shrubs and plants are way ahead, using sunlight to create fuel. Mastering artificial photosynthesis could mean solar energy be used for a plethora of human essentials, from medical advancement to carbon based fuel production – rather than just electricity.
“By reverse-engineering the biological photosynthetic process, we could make it more efficient for making certain kinds of products, or we could develop systems that synthesise the kinds of valuable products not found abundantly in nature,” says Shtein.
Shtein explains how fuel can be produced after molecular-scale solar cells absorb sunlight and generate voltage, which “drives the flow of certain ions through cell membranes, which in turn runs nano-scopic chemical factories making molecules called ATP [adenosine triphosphate, an energy carrier lying in all living cells].”
In terms of widespread commercial availability, Schaefer says: “Biomaterials are really promising but we consider that the development may take some decades to become really competitive.”
Last, but by no means least, Japanese engineers at the global contracting firm Shimzu have almost literally gone for the pie in the sky, the moon on a stick – or to be more precise, the moon belted with solar panels.
Their proposed ‘lunar ring’ would place a belt of solar panels around the moon. Shimzu said uniting space technology with “virtually inexhaustible, non-polluting solar energy is the ultimate source of green energy” for the “infinite coexistence of mankind and the Earth”.
Earth’s adverse weather and troublesome oxygen and moisture in the atmosphere complicate solar energy generation, requiring “all kinds of extra encapsulation” of modules says Shtein. What could be simpler than beaming an overflow of radiant solar energy to earth from the moon?
Well, first there is the small matter of getting the thousands of kilometres worth of solar panels to the moon. “Lobbing any kind of mass toward the moon is quite expensive, and subjects the panels to cosmic radiation and dust,” says Shtein. He predicts this could be solved in a decade or two as solar powered satellites already orbit the planet.
Shipping raw materials to “build the panels on the moon” might make it easier, says Shtein, depending on what weighs more: ready-made panels, or a factory.
However Shtein points out that there is more than just scientific advancement needed for this idea to be realised; collective political co-operation on a global scale is required too, possibly flinging the idea light years into the future. Shtein estimates the lunar ring is a “stretch, even by 2035”.
So we have a while to wait before moon-based, multi-layered, nanotech painted, photosynthesis mimicking solar cells are as common as light bulbs and automatic doors