Global warming?
in [Design]
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From: JosephKK on 13 Jan 2010 00:42 On Tue, 12 Jan 2010 09:47:32 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com/Snicker> wrote: >On Tue, 12 Jan 2010 18:28:41 +0200, Paul Keinanen <keinanen(a)sci.fi> >wrote: > >>On Tue, 12 Jan 2010 07:20:09 -0800, John Larkin >><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >> >>>Solar may make some sense, but individual rooftop solar makes a lot >>>less. The economy of scale is all wrong. >> >>Individual solar cells make sense mainly when used to run the air >>conditioning. In this case, both the production and demand are quite >>well synchronized. >> > >Can you actually generate enough power to run A/C, or must you still >draw from the power company? > > ...Jim Thompson Not usually. It might work for some larger, single story, well insulated buildings. Rough cut, solar cell efficiency 15%, 93 W/ft^2. 2000 ft^2 house, 1/3 of roof with solar cells (won't be over 1/2 without special design). 666 ft^2 * 92 W/ft^2 * .15 = 9 kW max peak. Over one days time averaged over a year ~= .636 * 1/2 * 9 kW ~= 3 kWh per day. Falls a bit short. But enough to noticeably help.
From: Paul Keinanen on 13 Jan 2010 01:38 On Tue, 12 Jan 2010 09:47:32 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com/Snicker> wrote: >On Tue, 12 Jan 2010 18:28:41 +0200, Paul Keinanen <keinanen(a)sci.fi> >wrote: > >>On Tue, 12 Jan 2010 07:20:09 -0800, John Larkin >><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >> >>>Solar may make some sense, but individual rooftop solar makes a lot >>>less. The economy of scale is all wrong. >> >>Individual solar cells make sense mainly when used to run the air >>conditioning. In this case, both the production and demand are quite >>well synchronized. >> > >Can you actually generate enough power to run A/C, or must you still >draw from the power company? Depends of the insulation of the house and the size of the panels :-). If solar energy is used only for heating or cooling, it might be a better idea to skip the PV panels that all have a low light to electric conversion efficiency and use thermal energy directly e.g. with evacuated tube solar collectors. In addition to heating, such thermal solar panels can also be used to run absorbtion heat pumps for cooling, since only about +90 C is required from the panel.
From: Phil Hobbs on 13 Jan 2010 13:59 On 1/13/2010 12:42 AM, JosephKK wrote: > On Tue, 12 Jan 2010 09:47:32 -0700, Jim Thompson<To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com/Snicker> wrote: > >> On Tue, 12 Jan 2010 18:28:41 +0200, Paul Keinanen<keinanen(a)sci.fi> >> wrote: >> >>> On Tue, 12 Jan 2010 07:20:09 -0800, John Larkin >>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >>>> Solar may make some sense, but individual rooftop solar makes a lot >>>> less. The economy of scale is all wrong. >>> >>> Individual solar cells make sense mainly when used to run the air >>> conditioning. In this case, both the production and demand are quite >>> well synchronized. >>> >> >> Can you actually generate enough power to run A/C, or must you still >> draw from the power company? >> >> ...Jim Thompson > > Not usually. It might work for some larger, single story, well insulated > buildings. > > Rough cut, solar cell efficiency 15%, 93 W/ft^2. 2000 ft^2 house, 1/3 of > roof with solar cells (won't be over 1/2 without special design). 666 ft^2 > * 92 W/ft^2 * .15 = 9 kW max peak. Over one days time averaged over a year > ~= .636 * 1/2 * 9 kW ~= 3 kWh per day. Falls a bit short. But enough to > noticeably help. That's quite optimistic. A good rule of thumb for average power/peak power over a year is 1/6, even for tracking collectors. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 email: hobbs at electrooptical dot net http://electrooptical.net
From: JosephKK on 13 Jan 2010 22:18 On Wed, 13 Jan 2010 13:59:40 -0500, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >On 1/13/2010 12:42 AM, JosephKK wrote: >> On Tue, 12 Jan 2010 09:47:32 -0700, Jim Thompson<To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com/Snicker> wrote: >> >>> On Tue, 12 Jan 2010 18:28:41 +0200, Paul Keinanen<keinanen(a)sci.fi> >>> wrote: >>> >>>> On Tue, 12 Jan 2010 07:20:09 -0800, John Larkin >>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>> Solar may make some sense, but individual rooftop solar makes a lot >>>>> less. The economy of scale is all wrong. >>>> >>>> Individual solar cells make sense mainly when used to run the air >>>> conditioning. In this case, both the production and demand are quite >>>> well synchronized. >>>> >>> >>> Can you actually generate enough power to run A/C, or must you still >>> draw from the power company? >>> >>> ...Jim Thompson >> >> Not usually. It might work for some larger, single story, well insulated >> buildings. >> >> Rough cut, solar cell efficiency 15%, 93 W/ft^2. 2000 ft^2 house, 1/3 of >> roof with solar cells (won't be over 1/2 without special design). 666 ft^2 >> * 92 W/ft^2 * .15 = 9 kW max peak. Over one days time averaged over a year >> ~= .636 * 1/2 * 9 kW ~= 3 kWh per day. Falls a bit short. But enough to >> noticeably help. > >That's quite optimistic. A good rule of thumb for average power/peak >power over a year is 1/6, even for tracking collectors. > >Cheers > >Phil Hobbs Thanks for touching up my rough cuts. I knew there were a bit optimistic. For real fun, try designing the electronics that feed the solar power back to the grid safely. It would have to be in phase and very low harmonics, handle peak power and marginal source power, and disconnect rather completely overnight.
From: John Larkin on 13 Jan 2010 22:29
On Wed, 13 Jan 2010 19:18:53 -0800, "JosephKK"<quiettechblue(a)yahoo.com> wrote: >On Wed, 13 Jan 2010 13:59:40 -0500, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: > >>On 1/13/2010 12:42 AM, JosephKK wrote: >>> On Tue, 12 Jan 2010 09:47:32 -0700, Jim Thompson<To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com/Snicker> wrote: >>> >>>> On Tue, 12 Jan 2010 18:28:41 +0200, Paul Keinanen<keinanen(a)sci.fi> >>>> wrote: >>>> >>>>> On Tue, 12 Jan 2010 07:20:09 -0800, John Larkin >>>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>> >>>>>> Solar may make some sense, but individual rooftop solar makes a lot >>>>>> less. The economy of scale is all wrong. >>>>> >>>>> Individual solar cells make sense mainly when used to run the air >>>>> conditioning. In this case, both the production and demand are quite >>>>> well synchronized. >>>>> >>>> >>>> Can you actually generate enough power to run A/C, or must you still >>>> draw from the power company? >>>> >>>> ...Jim Thompson >>> >>> Not usually. It might work for some larger, single story, well insulated >>> buildings. >>> >>> Rough cut, solar cell efficiency 15%, 93 W/ft^2. 2000 ft^2 house, 1/3 of >>> roof with solar cells (won't be over 1/2 without special design). 666 ft^2 >>> * 92 W/ft^2 * .15 = 9 kW max peak. Over one days time averaged over a year >>> ~= .636 * 1/2 * 9 kW ~= 3 kWh per day. Falls a bit short. But enough to >>> noticeably help. 666 square feet is a lot of solar cells. My next-door neighbor has sorta typical panels on his roof and I'd estimate a tenth of that. >> >>That's quite optimistic. A good rule of thumb for average power/peak >>power over a year is 1/6, even for tracking collectors. >> >>Cheers >> >>Phil Hobbs > >Thanks for touching up my rough cuts. I knew there were a bit optimistic. >For real fun, try designing the electronics that feed the solar power back to >the grid safely. It would have to be in phase and very low harmonics, handle >peak power and marginal source power, and disconnect rather completely overnight. And last for 20 years or so. John |