Whoah... Im 100% motivated by solar and EV's, but need to correct some overreach here...
> PV efficiency is already plenty [18%]. True, and anyone who thinks higher efficiency is just around the corner does not understand solar. We have had silicon 5%-15% efficiency for half a century (now being stretched to 18%) and now costing 1% of what it did 50 years ago. But, we have also had better than 25% solar cell efficiency for decades. BUT HOMEOWNERS WILL NEVER SEE IT. The high end stuff costs over 500 times as much per watt. But we use it every day in on satellites in space, because paying $5,000 for a $10 solar cell is worth getting twice the power for a $250,000,000 satellite. But you will NEVER see the cost come down to home applications.... Every time the high end efficiency goes up 2% (its now over 30% and approaching 40% in the lab), then the space industry with deep pockets abandon last year's model and switch to the new one. There is absolutely no market remaining that is big enough for last year's cells (that cost 500 times more to make) to have any pressure for the price to come down. Hence you will always see prices for the expensive high efficiency stuff ALWAYS stay high, and the cost for the 18% standard silicon continue to drop. > The insolation on the average single-family home's > roof at today's efficiency is virtually always > some multiple, generally some very significant multiple, > of the home's electricity use. I disagree there. Yes for someone in mild weather with no heating or air conditioning needs. Sure.... . But NOT for the typical modern non-FOSSIL FUEL BURNING all electric homes with AC and Electric Heat pumps... IE, if a home continues to burn fossil fuel for heat, Oil, and Propane, then we have not fully switched to renewables. If one is 100% electric (heatpump) and lives anywhere but the south or california, I think no one's "typical" roof can sustain our present life style. I know! I designed my solar system (bigger than my roof) to meet my electric load. But that was before I replaced the Oil heat with Geothermal. Then I had to DOUBLE my array, and at 17 kW it is twice the size of my roof. But I am a poor example, since my house is very old and poorly insulated (and in Maryland. Temps down to 8F last night). I think modern homes in fair climates with geothermal and a non shaded roof can approach 100% solar... > In many parts of the country, the payback time > for a complete off-grid solution is better than... No way for "off-grid"! You CANNOT go off grid without giving up 2/3rds of their solar investment or giving up 2/3rds of their energy lifestyle at the same price. There is simply no way to store "off grid" the double energy solar provides in the summer and save it for when it is needed most in the winter. I think what you MEANT TO SAY is that "payback time for a complete self-sufficient solar solutions is better than...." Because you have to have grid-storage to get the full benefit of solar. Here "self-sufficient" means you generate all of your annual energy from solar. But not that you can disconnect from the grid where you have to store it. Bob, WB4APR ---------------snipped from ----------------------------- That just means the system is under-sized. In such a case, either you should have spent more for a bigger system, or you knew what you were getting into and therefore budget your energy use accordingly. Low income households already face similar problems...do I pay the electric bill with the last $50 remaining on this credit card's limit, or do I use the money to buy groceries for the kids? > "Sorry, boss, I can't come in to work until this afternoon. Joe ran > the house flat with his welder last night, and I won't have enough > juice to charge my car until the sun comes up." If Joe's a contractor, he should be showing up with his own power supply (such as one of the many industrial EVs we've seen Bruce mention with their own power plugs) to run the welder in this future -- or, otherwise, first making sure that the site he's visiting has the spare capacity to power the welder. And if Joe lives in the home, it's his own damned fault. > Also, the cost of storage (lithium battery? what?) It's a big question today, but I suspect we'll have a clear winner in the next several years at the most. Nickel-iron batteries live longer than people but cost more than any other type of battery. Lead acids are pretty cheap but die after a few years and cost significantly more over a lifetime. But there may well be a market in EV batteries old enough to be less than optimal for vehicular use but still with plenty left in them for an off-grid system. I could see leasing / renting of battery systems becoming popular, with the company that owns the batteries responsible for ensuring a minimum kWh capacity of the pack in exchange for whatever fees they charge, similar to what we've speculated Tesla might offer with their car battery swaps. > would have to decline by, oh, I dunno, say, 90%? Nowhere near as much. In many parts of the country, the payback time for a complete off-grid solution is better than the payback time for money market funds and other financial instruments. That is, if you're invested in the stock market or especially your bank, you'll be wealthier at the end of a decade or three if you pull the money out and put it into an off-grid system. But that requires a significant amount (to most people) of available capital. But it also means that a business -- such as Solar City -- can afford to invest its own capital (or borrowed funds) to install such a system and become an ad-hoc utility and still make a marginal profit. That's with today's technology...and it's only getting better. > I have no idea whether such a quantum leap in PV and energy storage > tech is on the horizon. Absent one, though, I suspect your estimate of > "ten to twenty years" is probably a bit optimistic. But that's just it. It's doable _and_economical_ today, if you have the capital to invest. No more revolutionary breakthroughs are required to bring it to the masses; only gradual refinements of the types we regularly see and expect, perhaps coupled with some entrepreneurial innovation. Cheers, b& -------------- next part -------------- A non-text attachment was scrubbed... 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