Posted on 03/01/2006 5:25:16 AM PST by Mikey_1962
Energy security has become one of the hottest political topics in the last few years with the prospects of skyrocketing oil prices and shortages. Along with the looming dangers of climate change, the urgency of alternatives to CO2 emitting energy sources is becoming more obvious by the day. One of the most important actions to counter these challenges is the establishment of alternative energy sources such as solar energy. Latest research by South African scientists have taken us one step further to realising these goals.
Solar power has traditionally been differentiated into solar thermal and solar photovoltaic systems. The photo-voltaic effect is a phenomenon that depends on quantum physics, and allows specific materials to directly convert solar radiation to electricity. The photo-voltaic effect is used in solar panels, that have been powering spacecraft for decades and have recently been making their presence felt in supplying electricity to free-standing locations on earth, like telephone towers and pump systems on farms.
However, the panels available commercially today are almost all based on high-purity silicon as the photo-voltaic material, and these panels are much more expensive than the equivalent amount of coal, petrol or gas.
The only way to make photovoltaic energy more widely used, is to make devices (including solar panels) that are much cheaper than the current silicon-based devices. The most promising PV material identified to date is Copper-Indium-Gallium-Diselenide (CIGS).
CIGS is much more efficient than silicon at converting incident sunlight into an electric current: Less than one micron of CIGS absorbs more than 99% of available incident solar energy, compared to 350 microns of silicon to do the same job.
Despite the excitement around CIGS, significant cost savings compared to silicon were not achieved, despite 20 years of research. However, a new development has made the picture considerably brighter.
(Excerpt) Read more at scienceinafrica.co.za ...
200 gallons/day, 4 gallons per patron, 18 tons/month???
From Sept. 6,2004 Business Week:
"The solar-thermal strategy is roughly 30% efficient at turning the sun's heat into electricity -- about double the efficiency of photovoltaics. As a result, the thermal technique enjoys a pricing advantage. The giant solar-dish mirrors designed by Stirling Energy Systems Inc. could generate electricity for less than 8 cents per kilowatt hour (kwh) -- maybe even 6 cents, asserts David J. Slawson, CEO and founder of the Phoenix startup. Unlike photovoltaic panels, though, solar dishes aren't practical for homes. To work effectively, they need to be large -- too big to plant on a roof or even in a backyard. Stirling Energy's dishes are 38 feet across and 40 feet tall and generate 25 kilowatts, or enough juice for five or more homes.
The dishes are based on technology pioneered at the Solar Two "farm" in California's Mojave Desert, sponsored by the Energy Dept. Mothballed in 1999, Solar Two used 1,800 solar dishes in concentric arcs to reflect the sun's heat onto a central "power tower." That layout required a massive $150 million investment for 10 megawatts of capacity -- or $15 per watt. To reduce costs with a modular approach, Slawson has scrapped the tower. Instead, he mounts a miniature generator at the focal point of each dish.
When these power dishes enter volume production, expected around the end of 2006, Slawson predicts costs will tumble 90%, to $25,000 per 25-kilowatt dish. That would put the capital cost of a 10-Mw plant at $10 million, or $1 per watt. But Arizona Public Service Co., which is under a state mandate to generate 1.1% of its electricity through renewable resources by 2007, isn't waiting. It will install 10 dishes next year. And utilities in Nevada and California are haggling for 40."
My electric dryer uses over 3000 watts to dry a load of clothes in about 30 minutes; a clothesline in the yard in direct sun will do the same job in about an hour.
conventional silicon panels require up to seven years of electrical generation to make up for their production energy requirements
(greenies don't like that kind of talk - they think the panels fall from the sky)
(don't even mention the noxious CHEMICALS required for fabrication!!)
"If I kept copies of all the stories about novel new materials that will finally make solar economic, I'd have a stack as tall as me."
And you'd have to add an addition to your house to store them---with the attendant energy costs!
You bet, I'm sure many here would like to hear the up's and down's in installing a PV system.
Hence no expensive and massive batteries or inverters required.
Put me on the list - I'll buy too.
W are a reactive society, not proactive. We'll start to develop ANWR when we have a major oil supply disruption and only have to suffer for 10 years. Solar panels that work will be developed during this 10 year period when gas is $25/gallon
Don't forget your inverter losses. Typically 25% to 35%.
"Lots of large batteries will be be required for peak loads and conventional backup power for cloudy days.
"
Lots? Maybe not.
New batteries consisting of graphite sprayed on foam.
Supercapacitors.
Simple steam generators with multiple mirrors/fresnel lenses.
Roofing tiles that are solar panels and roof tiles.
And that is just the beginning.
The way I see it for about the price of a SUV I will generate my own primary electric using the grid for peak load and storage for night use. The battery bank is for emergency backup during grid outages. I'm not going to make a killing with this system, but I will have pre-paid my electric bill for the foreseeable future at the current rate. Also on those hot and sunny days the state and utility get the advantage of me pumping power into the grid during peak hours and pulling it back during non-peak hours.
About 12-15% due to the battery bank. Some inverters can pull off 95% or more efficiency w/o batteries.
"Where would you store the batteries to provide electricity at night?"
Best place is in a cold, DARK room.
"Where would you store the batteries to provide electricity at night?"
Best place is in a cold, DARK room.
That seems a bit low. Check the inverter's specs carefully. Power electronic companies are notorious for playing the "specmanship game". Check the fine print. Efficiency specs are the most notorious in this regard. Usually given at the most ideal line/load point.
The inverter I've selected spec's at 90%-93%, I'm thinking it's likely around 85 to 90% depending on load.
Soon the houses walls will be 'the batteries'.
Graphite sprayed over foam.
I headed a Power Systems group for a major defense contractor. Retired in 1995. We dealt with anywhere from 200 watt to 10,000 watt converters. The holy grail in converters/inverters was the efficiency number. So of course the best numbers were always in the brochures.
The best number I ever measured in a lab was about 85% at a ideal line and load condition. That was over 10 years ago.
Since you are converting directly from DC to AC those numbers may hold up. We were always going from 60 hz AC to 400 hz AC and visa versa which produced an extra loss component.
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