I usually don’t spend a lot of time posting about solar panels (photovoltaics or PV) because the main problem is conversion efficiency and constantly hearing about the incremental improvements of fractions of a percent doesn’t really get the juices flowing for most people. There have been a couple very interesting developments of late, but they will need some time to move out of the labs and into something more practical for us trying to actually own some of this startling tech.

Helios Solar is a Denver based startup with a smart product which according to their PR is available for buying now (orders being shipped in spring), based on concentrated sunlight and ultra efficient solar cells. The aptly named SunCube is an aluminum box a little over a meter wide on each side (106cm to be exact) and standing 40cm deep; this box is subdivided into 9 squares mounted with 9 triple-junction gallium arsenide chips and lenses.

	Denver installation heliossolarcpv Roof-top testing

A little background first. Many have heard the statistic that the earth intercepts some 1000 watts of solar energy per square meter summed across the entire light spectrum, this sounds impressive but really it is a game of capturing a diffuse source.

That is why solar panels are flat; the cells (the parts that actually convert photons into electrons) must be oriented to intercept as much solar radiation as possible. That is also why ‘tracking’ turns out to be such a major deal; solar panels simply tilted toward the place where the sun is brightest at one time during the day/year discounts the cumulative energy produced during winter or morning and evening hours.

By following the sun’s path across the sky every solar panel instantly gains some 20-30% efficiency, too bad that solar panels are so big and heavy requiring major support structures to just hold them in place let alone the weight and cost of adding tracking.

Another way to increase the amount of energy each solar cell ‘sees’ is to concentrate the sunlight, essentially focusing a wide area down to the surface of the cell, again a major problem with this is the added weight of both the lens and its supporting frame. Tracking is critical for solar concentrators as optics dictate a very precise line from source to surface. Interestingly Helios Solar has realized that these seemingly difficult engineering ‘constraints’ can be made to work synergistically.

	Array in testing greenandgoldenergy Production plant in India powered by SunCubes

The SunCube has been designed to concentrate the solar radiation some 750 times down on to the special Emcore chips and produce 300 watts of energy for a conversion efficiency of 30%.

In doing this, the frame and tracking structure had to be made as light and strong as possible, but by using polycarbonate Fresnel lenses and a simple dual axis tracking system, the size (and therefore weight) of the high efficiency solar cells could be drastically reduced.

The chip maker, Emcore, is also in the business of making high efficiency solar cells for satellites where weight and longevity are crucial; however providing the cells for commercial production of the SunCube is a different matter which must have taken some work to get to necessary volumes.

These small cells (about 1cm2 instead of the standard 100-225cm2 of conventional cells) are made to be replaced within the SunCube housing which is a smart bit of forward thinking from Helios
Solar and essentially opens the product up for using
any triple junction cells that may come along in the
future as conversion efficiencies slowly improve.

	Side by side testing heliossolarcpv Spain's installation

There are a lot of concentrated PV (CPV) players coming to market now so it will be interesting to get some product feedback on how these special cells stand up to the increased temperatures produced by the lens, any mechanical/longevity problems with the tracking equipment and if the efficiency numbers can be realized in the real world. Helios Solar is also pretty optimistic with its energy production calculations claiming “$.04/kWh when local or state incentives are available”; no numbers attached to those ‘incentives’ for clarifications sake I’m afraid.

In the end the SunCube is an intriguing idea for cost and area optimization (greater conversion efficiency means less roof-top dedicated to capturing the sun), but when considering the competitor for cheap electricity is coal, maybe a different metric for calculating efficiency is needed. In this case the one can be had at the cost of digging it from the ground but once burned it is gone forever, the other is recyclable and upgradable, seems there should be a way to represent that economically.

Via: earth2tech.com