Australian company Green and Gold Energy has put a solar appliance called a Sun Cube on the market. The Sun Cube is an interesting and simple concept. It’s effectively a box with Fresnel lenses on one side and triple junction solar cells on the other. The appliance is mounted on a dual axis tracking system to ensure that the assembly is always pointed at the optimal location to absorb and focus sunlight onto the cells and the whole deal is controlled with an on-board microprocessor.

Here’s a picture of the appliance:


Recently GGE has announced that they’ve been able to get 35.4% efficiency from these units, see the graph below for data on the experiment. Update: May 14, 2007: the efficiency graph has been removed from Sun Cube’s web site, thus we are unsure if this claim still stands. We have contacted Green and Gold Energy directly and asked them to comment on this entry and contribute any material they see fit to assist in clarification.

Update to the Update: May 15, 2007: Greg Watson, CEO of Green and Gold Energy responded immediately to our inquiry. In a nutshell, G&G have changed business strategy from distributed solar installations to concentrated solar installations with utilities. This change was prompted in part as a means to better manage their intellectual property. Mr. Watson says he knows the change in strategy has caused some grief among early adopters, but this is the direction the company needs to pursue.


This could be a good option for home installations, we’ll watch GGE and the SunCube with interest.

Steve Years jogged my memory about solar thermal over the weekend with his blog entry about a 64MW facility coming online in Nevada this year.

Solar Thermal Plant operations illustration


As you can see from the illustration above, this is a binary power system where heat is transferred to a working liquid that carries heat to water which is then vaporized into steam and cycled through a turbine sent to a condenser for cooling and then it starts the cycle again. Since the sun only shines so much, there is a natural gas boiler that takes over at night and when weather conditions aren’t appropriate to enable a steady flow of energy to consumers.

Map of appropriate solar-thermal regions of the globe


Not only are solar thermal systems ready for primetime, they’ve been working for some time. The largest operator is Florida Power and Light who operates the largest plant, the 310MW Solar Electric Generation Systems (SEGS) is a set of 7 array plants in the Mojave Desert in California. Obviously this isn’t a 100% renewable system, but it is a step in the right direction combining natural gas with sunlight to do the heavy lifting during peak consumption.

The costs of solar thermal systems are still relatively high, around $3.9M per MW in the Nevada Solar One 64MW project. The technology is competitive with “clean coal” technologies, though it’s still a far cry from the $0.75M per MW for natural gas fired generation. But it’s a great step forward from photovoltaic systems that still cost somewhere north of $8M per MW.

One has to wonder if the solar thermal folks should be talking to the binary geothermal bunch and the chemistry already completed allowing power to be generated from 75 degree centigrade resources, that has to be more cost effective than the 400 degree centigrade solar thermal design specificiation.

Recently I ran across a reference to the Swiss company Flisom which is a 2005 spinoff of ETH Zurich (The Swiss Federal Institute of Technology.)

Traditional photovoltaic (PV) cells use monocrystalline silicon wafers to capture photons in sun light to excite electrons which are then directed to a conductor resulting in direct current. These PV cells are the prevalent technology installed in the marketplace today. Another variation on theme is to coat a silicon substrate with some sort of PV chemical mixture which then performs essentially the same process as pure silicon PV cells. The issue with these approaches is cost, manufacturing and material.

The latest research has revolved around nanocrystal, polymer, and photoelectrochemical cells. That’s where Flisom comes in, they seem to have figured out how to use the photoelectrochemical approach on a plastic foil substrate to harvest sunlight and convert it to direct current. The Flisom approach uses the Cu(In,Ga)Se2 compound (commonly called CIGS) sandwiched between a layer of Zinc Oxide (ZnO) on the top and Molybdenum (Mo) on the bottom. See a cross section of the material in the image below:



The efficiency demonstrated right now is 14%, which is pretty good for an emerging technology. If they can perfect this approach, the solar electric power landscape will change as the material can be cost effectively produced and all of the sudden common items like windows can become solar arrays inobtrusively and cheaply. That would be pretty cool…


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In this AP article it’s explained that a State Senator from Virginia is staying in solar-powered home designed by Virginia Tech engineering students. Frank Wagner is using this as a means to raise awareness of renewable energy and self-sufficiency by living in the house outside the Science Museum of Virginia. While the experience hasn’t been bug-free – during a 20F night the water supply froze – it has proven viable. This is a custom 800 square foot dwelling that is more of a prototype than anything else, but it’s great to see Wagner and the students make a public point on the subject.

Congrats to the folks out in Virginia for doing this, it’s a worthwhile exercise.


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A former Sun colleague, Jon Greaves, sent me this article a few days ago:

Norfolk Wildlife Trust now has an environmentally friendly
website, after a move this week to solar powered hosting.
Athenaeum who run EcologicalHosting.com are the only UK
based company to have an entire hosting infrastructure
powered from renewable energy sources, making it
low-impact on the environment.

Their main hosting is housed in a data centre in California.
Electricity from 120 solar panels capable of generating up
to 60 kilowatts of electricity per day provides all the power
for data centre offices, air conditioners and all computer
equipment.

By choosing to host their website with them, NWT is making
a commitment to the environment to protect the future.
Normal data centres obtain their main power from the local
grid supply, using up very large amounts of electricity that
has been generated from non-renewable sources such as coal,
gas or nuclear power stations. Solar hosting plays its part to
help prevent global warming, and so helps to preserve the
natural habitat of animals around the world.

Director of Athenaeum Jamie Simpson commented:
‘EcologicalHosting.com welcomes Norfolk Wildlife Trust to
our solar powered Internet service. Along with our other
clients they are showing the world that they care about the
environment and also making a statement that many
traditionally power hungry services like web hosting do
have viable environmentally friendly alternatives available.’

Director of Norfolk Wildlife Trust Brendan Joyce commented:
‘We are delighted to move our website to
EcologicalHosting.com, as it is another way of reducing
our impact on the environment. Our website has plenty
of information on wildlife and caring for the environment,
and now our website hosting matches our green philosophy.”

I found this fascinating and believe we’ll see more of this type of company. Power consumption is one of the largest expenses for hosting providers and when they can tap into renewables where the fuel is free, there’s a real competitive advantage to be had over the long haul. Another opportunity I see clearly is harvesting the tens of millions of btus that are exhausted from data centers. It’s not yet clear what the 20-25C resource is good for, but the person or persons who crack that nut will be very rich…


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