Why do you think they call it dope, kid?
Why bet on solar power?
The technology is a durable, reliable source of energy. This last year added the best advantage-it’s now cheaper than competitive power. Tax and clean energy credits-money back to consumers-lower the price even as costs continue to fall.
For most, understanding how a panel generates power is simple. The sun shines and runs your TV. Look deeper to see how it happens and you might understand why solar will dominate the electric generation market in the US.
N and P Doping
Pure silicon, all by itself, doesn’t produce much electricity from sunlight. Doping, that is, strategically adding chemical impurities like phosphorus or boron to the silicon manufacturing process make the resulting crystals more conductive — ten million times more conductive. [pullquote_right]Pure silicon, all by itself, doesn’t produce much electricity from sunlight. Doping, that is, strategically adding chemical impurities like phosphorus or boron to the silicon manufacturing process make the resulting crystals more conductive — ten million times more conductive.[/pullquote_right]
Here’s how it works.
A solar panel has two distinct layers of silicon, one on top of the other. The sun facing side is doped with phosphorus, though other dopants can be used. Phosphorus has one extra electron compared to silicon and when combined, this outer electron can get knocked free by sunlight. This is the N, or negative doped part.
Boron has one less outer electron than silicon, creating a gap — a hole — where electrons naturally want to go. The electrons freed by sunlight want to run to this hole. This is called P, or positive doped.
By wire connecting the top and bottom sheets of N and P doped silicon, photons — light particles — hit the sunny side and send electrons scattering along the surface of the crystal to the waiting holes on the bottom. They flow from negative to positive just like a battery. The stream of electrons are harnessed to do work through the completed circuit.
The physical harvesting of electricity from sunlight, called photo voltaics (PV), is not reserved to silicon alone. A number of competing materials produce the PV effect. Among the attention-getters are crystals of calcium titanate also named perovskites. They’re cheap as the dirt they come from.
Another scheme involves roll to roll printing of organic polymer ink into thin film. In a process reminiscent of industrial news printing, these cells are made cheaply and fast. Perovskites and the thin films are promising candidates to someday replace present commercial solar cells, but they are competing against silicon technology that is proven and economic. The challengers, however cheap, are also presently far less efficient at converting sunlight to power. It’s hard to predict when any new technology becomes king of the hill. Day-by-day, engineers world-wide successfully hammer at the problem with consistent incremental gain. A pot of gold awaits the winners.
credit: “PVeff(rev141218)” by Greg Wilson and Keith Emery — National Renewable Energy Laboratory (NREL), Golden, CO. Licensed under Public Domain via Wikimedia Commons
Cost vs Efficiency
Even as labs across the planet improve efficiency and lower costs of promising hopefuls, refinements to light manipulation and concentration open new avenues in the quest for cheaper and better. Will there be a single winner? See the National Renewable Energy Lab chart comparing performance of competing PV schemes. It shows the breadth of research and gives a hint that success may be situational. Cells are often compared by cost per watt produced, but other factors like weight and size figure in when choosing power production for a space station versus, say, a remote third world health clinic. Don’t make the mistake of thinking lower efficiency impedes marketability. We may one day see every newly constructed surface covered in lower efficiency, cheap PV materials — like typing paper cheap.
Our planet is down to only 900 terawatts of combined petroleum and mineral energy reserves — good for the next 40 years or so. The earth receives 23,000 terawatts of solar power each year. Electricity from sunlight is dependable and always getting cheaper — a good thing since we’ll soon have no choice but to break our addiction to dirty, expensive legacy power.
The analogy of oil being ‘dope’ fits. It’s a quick fix with bad downsides and poor regard for the future. The present furious pace of technological growth in solar may finally allow our avarice to align with our better interests. The coming 17 trillion dollar US conversion to solar has a boomtown flavor that only the stodgiest of oilman can ignore.
by Todd Bierman for www.techinamerica.com. Thank you, Alisa.