Isn't it 8 LBS per gal? If I am not mistaken - the biggest factor in heating a pool is not the initial temp step (which is what you calculated) but the continuous and extremely large loss of heat to ambient due to evaporation and simply no insulation (unless you apply a cover every time you do not use it, which makes sense) but even then there is only a tiny bit of insulation, you are mostly removing the evaporation losses. Note that evaporation losses can cause the water temp to be *lower* than ambient if not constantly heated, similar to wind chill factor.
Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com Email: cwa...@proxim.com Private: http://www.cvandewater.com Skype: cor_van_de_water XoIP: +31877841130 Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 -----Original Message----- From: EV on behalf of Robert Bruninga via EV Sent: Sat 1/17/2015 8:12 AM To: robert winfield Cc: Electric Vehicle Discussion List Subject: Re: [EVDL] EV Demand Response - (solar-thermal-NOT-2) > there is 1 place at least solar thermal wins. Heating swimming pools! But all that rooftop thermal energy is doing nothing during fall, winter and spring? Does it help power the EV? It might be interesting to do some numbers. Im curious... You may be right. Pool thermal heat simply needs a lot of pipe on the roof and are pretty low cost...... But could we make these assumptions... Lets assume 19,000 gallons X 7 lbs/gal X 20 degrees = 2,660,000 BTu divided by 3400 Btu per kWh and we get about 780 kWh needed to heat that water over about 3 months?. (doing not much the other 9 months, nor doing much once the water is already hot). Now, a modest 600 watt solar PV array (just three panels) can also produce about 780 kWh per year. And cost about $600 (DIY) or about $2000 contractor installed. So how does the cost of the pool heater compare? How does the roof area of the thermal pipes compare to the 50 sqft of the PV? If PV and a heatpump water heater were used, you could heat the pool to that same amount with a SINGLE 18 sqft solar panel. How does that compare? Add another $1500 to the cost for the heatpump. The point is that the same roof area as the pool heater when used instead for PV, would not only heat the pool, but also power the EV's and power some of the house too (maybe). Im curious...? Thanks BOb, WB4APR On Sat, Jan 17, 2015 at 10:37 AM, robert winfield <winfield...@yahoo.com> wrote: > there is 1 place at least solar thermal wins. Heating swimming pools! I > accidentally got my 19,000+ gallon pool up to 99 degrees F last labor day > using only rooftop solar > otherwise, i agree about PV, having PV since 1999 > > ------------------------------ > *From:* Robert Bruninga via EV <ev@lists.evdl.org> > *To:* ev@lists.evdl.org > *Sent:* Wednesday, January 14, 2015 1:34 PM > *Subject:* Re: [EVDL] EV Demand Response - (solar-thermal-NOT-2) > > > 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:leeah...@earthlink.net] > 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, leeah...@earthlink.net > _______________________________________________ > 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) > > > > -------------- next part -------------- An HTML attachment was scrubbed... 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