Technology Explanation – Simplified
(Think of “All Day Solar for Dummies”)
Special Note: By request, this opinionated solar primer assumes the reader has little prior knowledge of photovoltaics. We advise readers to try this explanation of the technology instead of spending their more valuable Internet surfing time locating and dusting off their old high-school chemistry textbooks.
At the most basic level, sunlight in the form of photons, strikes the silicon semiconductor material in the solar cell, knocking electrons* loose and creating a flow of electricity. Each photon of sunlight knocks loose one electron – that 1-1 relationship has been true since solar cells were invented by Bell Labs researchers in 1954.
Traditional calculations of efficiency values of PV (Photovoltaic – a fancy word for solar cells) are based on the assumption of 1000 watts per square meter of sunlight hitting the earth’s surface. So a 10% efficient cell generates 100 watts per square meter of sunlight, 15% efficiency is 150 watts per square meter, and so on.
What’s holding solar back?
Traditional silicon solar has hurdles to overcome in the following areas:
- “Too expensive” – without upfront subsidies and rebates, solar can’t really compete with the per kilowatt hour prices of coal or natural gas in the short term because solar is paid for at the time of installation and requires many years to payback.
- “Too heavy” – 30-50 pounds a square meter for solar includes a solid base of silicon solar cells covered by a thick sheet of protective glass.
- “Too limited in output” – averaging only 2.5 to 5.5 hours of daily solar output across the US due to cloudy, rainy conditions that limit the number of average peak hours available over the year.
- “Too inefficient” – market average efficiency for silicon solar cells is about 15%, or 150 watts per square meter; a typical modern house needs about 3,000 watts (or 3 kilowatts) per hour powered with about 20 square meter panels.
- “Too limited in supply” – even the world’s largest solar companies face long order backlogs that require prepayment, caused in part by silicon shortages and the large capital requirements to expand their production plants.
The 1st Generation of Photovoltaic Technology
A bulk silicon technology serving 93% of the market, and production methods haven’t changed much in the past two decades. These traditional crystalline silicon-based solar cells are a very reliable workhorse for output during this time as proven by its record of solidly delivering 25 to 30+ years of power without any real maintenance costs. Multiple layers of expensive semiconductors are now being used to form a multi-junction, higher efficiency solar cell with much more design complexity.
The 2nd Generation of Photovoltaic Technology
The alternative to bulk layers of silicon under glass is to use thinner and more flexible films of silicon (and other lightweight conductive materials) as the primary source of converting photons of sunlight to electricity. Because silicon is expensive to manufacture, creative new ways to manufacture and use less silicon and related conductive materials generates less output but a much lower production cost. These thin-film products are much lighter and more flexible, but are generally slightly less efficient per square meter of sunlight than the 1st generation silicon solar. Many thin-film start-up companies are getting publicity and money from investors who see a lower-cost way to capitalize on the solar industry’s 50% annual growth rate.
1st generation and 2nd generation solar cells have in common the 1-1 relationship between each photon of sunlight producing enough energy to force the output of a single electron to be used as electricity.
The 3rd Generation of Photovoltaic Technology
All Day Solar uses the same photon of sunlight to produce much more energy.
“The Pool Table Analogy”
When the sun is shining without clouds in the way, the energy from the sun is able to “knock loose” one electron per photon of sunlight based on the way 1st and 2nd generation silicon solar cells are designed.
With tiny nanocrystals called quantum dots or Qdots, the same photons of energy streaming from the sun are now capable of “knocking loose” multiple electrons per photon of sunlight, which the solar panel collects and converts into electricity.
We don’t actually expect you to try to remember your high school chemistry lessons of electrons and photons. The best explanation out there is the anaology the original developers of Qdots used to first explain their work to their friends – the pool table analogy.
For 1st and 2nd generation silicon solar, the photons of sunlight keep streaming down all day acting like a pool cue with just enough energy to knock one ‘silicon-based electron’ cue ball at a time to generate electricity on a continuous trickling basis. Only when the sun is shining is there enough energy to ‘knock loose’ the electrons into the pockets as a current.
1st and 2nd generation solar cells only use the visible part of the electromagnetic spectrum. Their “pool cue” only has enough energy for one ‘cue ball’ electron at a time, and can only “shoot at” electrons in the visible spectra.
1 Photon “Knocks Loose” Multiple Electrons
With 3rd generation technology, the Qdots can be blended to process not just the visible part of the spectrum, but also the infrared (IR) and ultraviolet (UV) spectra, which happen to have a much bigger range of energies than the visible spectra alone. Labs have produced as many as 7 electrons from a single photon of sunlight and there is potential for many more!
The photons of sunlight energy are powerful enough to keep producing multiple electrons all day and effectively operate in low light and shade situations dawn to dusk, 9-12 hours a day. This is possible due to the addition of IR and UV Qdots, especially IR dots that have proven themselves to be the best low-light performers in products like night-vision goggles. The new Qdot solar cells achieve results not possible with traditional solar, which is completely dependent on high energy direct sunlight available on an average of 2.5 to 5.5 hours per day in the US. The longer hours per day produced by IR dot output helps cuts the payback time in half!
Qdots are also extremely lightweight, much cheaper to make than silicon wafers due to chemical costs, and easy to make with simple screen printing methods.
To paraphrase the BASF ads: The SpartzLight – “We don’t make the solar… we make the solar better.” The SpartzLight is All Day Solar’s patent-pending technology that multiplies the 3rd generation Qdot solar cells performance gains by 3-5 times in reduced “footprint”. So if a new Qdot solar cell from any third-party developer hits the market and generates 10% efficiency or 100 watts per square meter, the addition of the SpartzLight will boost that number to 400-600 watts/m2, with only a slight increase in cost.
* This is not technically correct, but for the purposes of this primer, the electron-hole pair excitons that are freed can be thought of as electrons for simplicity’s sake.