> My point was that if the energy source is FREE, > people don't care how much it takes or what its efficiency is. > They'll use whatever is cheapest; not the most efficient.
Well, we completely disagree. We are talking about rooftop solar. The system to use that solar energy is NOT free. It costs, and it costs big. And only someone with tightly held obsolete beliefs would cling to outdated inefficient conversion of that solar energy only to heat. Solar Thermal is really, really dead for the average homeowner. You were correct 10 years ago, but by 2006 PV broke even with solar water heating and now PV wins hands down. Remember, in the last decade PV solar has come down in cost 10-to-1. How much usable energy you get out of the roof divided by how much solar energy falls on that roof is a definition of EFFICIENCY. > Most single-family homes probably *do* have enough roof area to provide > all their energy needs. Simply *not* true in most places! You are talking about "all". When you consider that "all" of our energy needs includes ELECTRICITY, HEATING, COOLING, and EV CHARGING, then there are VERY FEW average homes in America that can meet "all" of their energy needs only on their roof. Period. Go start covering your availalable roof with in-efficinent expensive thermal system, and STOP BURNING ANY OTHER FOSSIL FUEL for HEAT or DRIVING cars, and see how quickly you run out of space. You'll want PV if you do the numbers right on a year-round basis. Solar THERMAL costs more, is harder to install, requires more maintenance and delivers less (on an annual basis) in every way than the same area of today's PV (and heatpump technology). Do the math. Bob, Wb4APR -----Original Message----- From: Lee Hart [mailto:[email protected]] Sent: Wednesday, January 14, 2015 10:15 AM To: Robert Bruninga Subject: Re: [EVDL] EV Demand Response - (solar-thermal-NOT) Lee Hart wrote: >> I think the word you want is "return on investment"; not "efficiency". Robert Bruninga wrote: > Nope. Most people only have so much roof available for solar energy. > And it is not enough for our total energy needs. So it is very > important how much of that surface area you turn into retail value > energy and is very much an "efficiency" determination. You are still using "efficiency" in place of other figures of merit. Here, you're talking about economics; not efficiency. What does it COST, versus how much money can I GET for it. That's return on investment. Most single-family homes probably *do* have enough roof area to provide all their energy needs, regardless of the PV cell's efficiency. >> Efficiency measures how much energy you get out divided by how much >> energy YOU put in. > Yes, how much do you get out VERSUS how much the SUN puts in. My point was that if the energy source is FREE, people don't care how much it takes or what its efficiency is. They'll use whatever is cheapest; not the most efficient. They decide based on economics; not efficiency. > > Solar thermal makes sense if you want heat. > > It's really GOOD at making heat! > > Which I don't need 7 months of the year. But I do! I live in Minnesota, where we spend more on heat than we do on electricity. Do not assume that what is best for you is best for everybody. There is a place for both PV to make electricity, and solar thermal to make heat. -- Ingenuity gets you through times of no money better than money will get you through times of no ingenuity. -- Terry Pratchett -- Lee Hart, 814 8th Ave N, Sartell MN 56377, [email protected] _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
