Global Solar Energy Grid - What’s Missing?
March 30, 2008 – 1:38 pmAs expected, there is some skepticism amongst visitors of SolarsBay.com as to the validity of the entire concept of buying and selling solar energy.
SolarsBay.com’s vision is multi-dimensional, as it predicts not only technological evolution, but also economical and social paradigm changes.
We are all used to buying energy from large utility companies. They set the price, they send us the bill, they kill the power when they want to (they will claim they do not have enough capacity). Buying energy from another person, who might live half way around the world, sounds crazy. But 20 years ago, who would imagined the Internet would enable us to watch a live video stream of a person connecting a (web)cam in his room and broadcasting his life to the entire world? The Global Solar Energy Grid is the Internet of Energy.
In this post, I want to focus on technology. I will try to explain exactly what technology we need to develop to enable the Global Solar Energy Grid.
The Solar Energy Grid is based on 2 main components - solar energy collectors (e.g. P.V. cells) that capture sunlight, and a medium to transfer the captured solar energy (e.g. fiber optic cables) on a global scale.
Stand-alone, the two pillars of the Grid have been in use for many years. Solar panels made from hundreds of P.V. cells are becoming household items in many places around the world. Fiber optic cables form the backbone of the Internet, transferring huge amounts of data and voice, converted to infrared light, over thousands of miles.
The price of these two components is constantly declining, as billions of dollars go into finding cheaper, more efficient materials to be used in P.V. cells and in fiber optics cables.
The Challenge
Why can’t we just take a solar panel, plug it to a fiber optic cable (that our cable company provides us, for example) and start selling our excess solar energy over the Internet?
The biggest problem is wavelengths. Current P.V. cells captures energy who’s wavelength cannot be transferred by fiber optic technology in use today. I will provide a short explanation about wavelength in fiber optics and in P.V cells.
Wavelengths
Solar radiation, which includes both energy visible to the human eye (what we call sunlight) and non-visible, is usually divided to several ‘regions’ of energy. These regions are determined by the wavelength of the energy in each region.
A word about wavelength - a wavelength is what it is: the length of the wave caring the energy from the sun to earth. The shorter the wave, the more energy the wave carries. The most challenging task the Solar Grid will face will be to transfer shorter wavelength energy over large distances. But we’ll get there in a moment.
Back to our solar radiation - one region of energy is in wavelengths between 400-700 nanometer. That is the range of visible light, red light located at the ‘right’ end, with wavelengths of about 700nm, while blue light is located at shorter wavelengths, about 400nm.
On the right hand of the scale, wavelengths longer than that of red light are called infrared light, ranging from 700 to over 10,oo0nm. We need to remember that in this longer waves, the level of energy is very low. And that is the problem with fiber optic cables, because this is the area where these cables work with maximal efficiency. Optical fibers can work at several different wavelengths, but most common wavelengths are 850, 1300 and 1550nm, all within the infrared range.
Why do optical fibers work at these wavelengths? If you try to transfer energy at shorter wavelengths than 600-700nm, a relatively high percentage of the energy is lost due to imperfections in the glass fiber optics are made of. I do not want to go into to many details as to why this is the case with optical fibers, but currently, these cables are used to transfer voice and data. For these purposes, using infrared light is just fine.
The good news is that when fiber optic technology first came out (around the 70’s), the loss of energy was at 99% over a distance of about 3,000 feet. Repeaters who’s role was to amplify the signal running inside the fiber had to be installed every few miles. In 1990, almost 20 years ago, AT&T was able to send a very strong signal over a fiber optic cable for a distance of 7,500KM without any repeaters! That’s an amazing improvement over a period of 20 years. Can we really believe that the great researches who made so many unbelievable leaps in technology cannot take another quantum leap in fiber optics technology?
As for the wavelengths P.V. cells can absorb - currently, the materials P.V. cells are made of can use energy from most if not all the visible light range (400-700nm). Infrared light does not yield enough energy to be converted to electricity. Converting UV light ( 3-400nm wavelength) would yield the most energy but due to their high intensity (we all know that UV light causes cancer) they are very difficult to capture-the shorter the wavelength, the higher the scattering and loss of energy.
As you can understand, the real challenge the Solar Grid vision is currently facing is that fiber optic cables cannot transfer energy captured by solar panels due to the shorter wavelengths P.V. cells are able to utilize. The breakthrough technology would have to allow the capture of U.V. energy using P.V. cells and then transfer of that U.V. energy over fiber optical cables for long distances with minimal energy loss.
One alternative to developing that technology might be using existing electrical grid to transfer the energy captured by solar panels. The current electrical grid can easily transfer much larger amounts of energy than solar panels will ever produce. However, current electrical grids have one major drawback - they are currently not global.
I hope I was able to answer some of the questions some visitors had in regards to how far is current technology from what is needed to create the Global Solar Energy Grid.
I would also be very happy to hear from all the experts out there on their views on the challenges the Solar Grid is facing.
