Achieving maximum solar panel energy transfer and storage

Achieving maximum efficiency

The key word here is efficiency. Efficiency to convert natural gamma radiation being pumped out by the sun into energy that can power homes, factories, and a million things more. The sun is no slouch in producing energy; every second our sun produces the same energy as about a trillion megaton bombs, or enough energy for almost 500,000 years of the current needs of our so-called civilization. In short, with the right advancements in heat and energy transfer, and we needn't worry about producing energy for a growing population. We have all we need.

Setting aside current fossil fuel infrastructure, which accounts for an unhealthy 98 percent of the world's current energy use, solar energy is hindered by cost and practicality. Although prices for panels, conductors and installation are reducing, they are still not on a par with coal and oil, which means companies seeking a competitive advantage look elsewhere. Secondly, solar energy is hindered by production, which means we're back to that word again; efficiency.

Harnessing the sun's energy into usable power for the masses isn't as easy as it seems, and means there is an arms race in certain scientific circles in producing a solar panel that can utilise the immense energy from the sun, and not lose this energy whilst transferring it into electricity.

The race to hit peak efficiency is hotting up (pun fully intended) and several companies have been sparing to maximise peak efficiency. In the news this week, a group of researchers from ISE have won the Fraunhofer Prize for record efficiency multi-junction solar cells, for work they accomplished last year, achieving record solar cell conversion efficiency of 41.1 percent. This trumps the previous recorded best of 20.7 percent, a recent accomplishment from Japanese energy company Sanyo.

Both panels work using silicon, but with clearly varying rates of success. For Sanyo, the efficiency was achieved by increasing the number of solar cell tabs from two to three and making each tab thinner. They also applied AG coated glass to the cells, which reduces the amount of scattering and reflection of light. The increase in energy conversion efficiency could make the solar modules useful in areas with less than ideal amounts of sunshine.

Drs Andreas Bett and Frank Dimroth from ISE, were able to record over 40 percent energy efficiency by using a metamorphic triple junction cell, which has three subcells of gallium indium phosphide (GaInP), gallium indium arsenide (GaInAs) and germanium (Ge), which are deposited by MOCVD in a stacked on top of each other. Each absorbs different wavelength ranges of the solar spectrum, boosting energy conversion efficiency.

Fresnel lenses at a distance of about 10cm focus incident sunlight onto the 3mm 2 cells, concentrating it by a factor of 500. The technology produces more power per area than conventional flat-plate PV technology, reducing the area of semiconductor needed.

"We substitute costly semiconductor material with inexpensive optics," says Bett.

The downside to the ISE panel is that it relies on concentrated optics, which means to gain maximum sunlight the solar panel would need to track the movements of the sun.

At 41 percent, the ISE panel is the most efficient panel for turning sunlight into electricity. This energy efficiency could potentially be doubled after Steven Novack of the Idaho National Laboratories unveiled a foldable solar panel that he claims is 80 percent efficient, but there is a catch; currently there is no way of transferring the captured sunlight into energy.

To obtain 80 percent efficiency, the team in Idaho utilise nanotechnology. The surface of the panel is printed with minuscule nano-antennae that capture infra-red radiation, the kind that the sun puts out in abundance, and is even available at night. However, with all the electrons pouring in to the panel from the surrounding light, there is still no way to capture them, and convert them to electricity, although the team at Idaho are already dabbling with tiny capacitors and AC/DC converters in the center of every tiny antenna in an effort to change this.

It's a crying shame, because capturing 80 percent of the sun's energy is not an easy task to accomplish, and something that could provide double the power output than is currently available.

The future is certainly bright for solar panel industry (another pun?), and with further advancements in capture and transfer, the conversion to alternative power and energy should be reasonably seemless. After all, the more efficient alternative energy is, the less the need for fossil fuels.

Relevant articles:

Solar energy efficiency could double using quantum dots | Nanosolar: Solar energy on a par with coal |Europe's push on offshore renewables | Europe: 100% renewable by 2050? | GE's next gen turbine set for Europe | Discussing Europe's energy future

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