Solar cell
in [Design]
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From: Paul Keinanen on 18 Apr 2010 06:20 On Sun, 18 Apr 2010 01:43:09 -0700, Robert Baer <robertbaer(a)localnet.com> wrote: >eryer wrote: >> Hi, >> I want to realize (for hobby) a battery charger using solar cell. I've >> found this sensor >> http://www.clare.com/Products/SolarCell.htm >> Its output voltage is high and can be used without step-up transformer >> (like any typical solar cell). So, i can use >> * a typical solar cell (with millivolt output voltage) and a step-up >> transformer >> * this sensor >> For you, what is the best (performance) solution? > Well, for starters, solar cells can output around 1.3V with a >reasonable load - a lot more that "millivolt output". > Secondly, the current capability of those Clare "cells" is a bit >miserly. To be fair tho, that is expected with such dinky arrays. What material would produce 1.3 V ? Silicon cells produce about 0.6-0.65 V so quite a few in series are required for any usable voltage levels in power production. In any switchers with bipolar components, at least one junction voltage drop is lost in switch Vce voltage drops, thus at least solar cell should be added to a panel to compensate for the switcher losses. Thus the panel should have a high output voltage and hence a lot of cells, thus adding one or two cells to compensate for the switcher losses does not matter so much. With very low output voltage panels, some low Rds FETs may have to be used as switches and rectifiers.
From: mpm on 18 Apr 2010 08:35 On Apr 18, 1:56 am, Paul Keinanen <keina...(a)sci.fi> wrote: > On Sat, 17 Apr 2010 21:14:57 +0100, Dirk Bruere at NeoPax > > > > > > <dirk.bru...(a)gmail.com> wrote: > >On 17/04/2010 20:39, Jan Panteltje wrote: > >> On a sunny day (Sat, 17 Apr 2010 11:25:32 -0600) it happened hamilton > >> <hamil...(a)nothere.com> wrote in<hqcqu9$7v...(a)news.eternal-september..org>: > > >>> On 4/17/2010 10:41 AM, Jan Panteltje wrote: > >>>> On a sunny day (Sat, 17 Apr 2010 08:57:14 -0700) it happened Don Lancaster > >>>> <d...(a)tinaja.com> wrote in<82u42oFov...(a)mid.individual.net>: > >>>>> There is NO best solution. > > >>>>> All of photovoltaics is an outright scam to steal state and federal funds. > > >>>>> Not one net watthour of pv energy has EVER been produced! > > >>>> Bad day? > >>> Ok, the link now works. > > >>> Dons argument is what the non-green types have been saying for years. > > >>> It costs too much to develop and manufacture green technologies then to > >>> stick to the 'tried-n-true' fossil fuels. > > >>> He does have a point, the cost to early adapters will never be paid back. > > >>> But, I think we need to start somewhere, and PV solar needs to have > >>> money to continue to develop and innovate. > > >>> As time passes and science has the money to continue, they will get > >>> there. ( maybe not in my lifetime, but they will get there ) > > >>> hamilton > > >> Yes, there are for example investors in Europe planning a solar plant in the Sahara desert IIRC. > >> Billions have been raised, DC very high voltage lines to carry it all over Europe. > >> With all that unrest I think the biggest obstacle is a political one. > >> US has Mojave desert, would be a nice place for solar .. > >> but the same greens that want solar also want to protect the bugs and snakes that live there ;-) > >> Just wait until get get cold feet, they will change their mind. > >> OTOH nuclear seems to be the only real option right now. > >> And if 'electric cars' were to really happen, then all bets are off, > >> new grid, new power plants... > >> Dunno. > > >That's why Spain is the ideal location. > > The Desertec plan and the existing stations in Spain and US are based > on concentrated solar thermal power, not PV cells, apparently for > economical reasons. > > In solar thermal plants, the sun heats a fluid which then drives a > conventional gas or steam turbine. It would make even more economical > sense, if the excess heat available on the "cold" end of the turbine > could be used for something useful, such as running absorbtion > chillers or desalination plants. > > PV panels on individual houses will make economical sense only in hot > countries if the cost of energy changes on an hour or shorter bases. > During hot sunny afternoons, the electric consumption will reach the > annual peak due to air conditioning. > > Much of the power during those hours needs to be produced with simple > cheap gas turbines (used only a limited number of hours each year), > but the overall efficiency is low and they need to use more expensive > fuels such as natural gas or oil. > > If this extra cost during summer day hours is charged from the > consumers, it would make sense for the consumer to use individual PV > panels for running the air conditioning, thus avoiding buying > expensive peak electricity from the power company. In such cases there > would be less need to have an expensive inverter to feed power back to > the grid. > > Of course, simple thermal collectors could be used to drive an > absorbtion cooler, even if the cooler efficiency is lower than a > compressor cooler, this avoids the low efficiency light to electricity > conversion in PV cells.- Hide quoted text - > > - Show quoted text - I read a stat somewhere (not sure where, or how true it was, but...) If the US built 91 miles square (~ 8300sq mi) of solar-thermal, it would completely satisfy our energy needs, including enough to power all our cars once converted to electric / hybrids. I believe that figure also included upgrading the transmission lines. We have the desert southwest.... Do we have the will or desire? Maybe we should spend the trillion dollars or so, build this thing, and finally solve the US energy problem and geopolitical destabilization problem the oil dependency causes. Though I wonder if stopping the hemorrhaging of our wealth to oil rich nations doesn't bring its own problems.
From: Paul Keinanen on 18 Apr 2010 09:43 On Sun, 18 Apr 2010 05:35:25 -0700 (PDT), mpm <mpmillard(a)aol.com> wrote: >I read a stat somewhere (not sure where, or how true it was, but...) >If the US built 91 miles square (~ 8300sq mi) of solar-thermal, it >would completely satisfy our energy needs, including enough to power >all our cars once converted to electric / hybrids. In the tropics, that area would receive up to 21 TW of solar energy at most during noon n the summer. Assuming 40 % Carnot efficiency for the steam turbine, thus 8.5 TW of electricity could be produced. >I believe that figure also included upgrading the transmission lines. > >We have the desert southwest.... The US is not in the tropics, so as an annual average at noon, perhaps 7.2 TW could be produced. Due to air mass losses at low solar angles, at most 10 h/day would produce the nominal power, dropping the daily average to 3 TW. Omitting any cloudy days (concentrating power does not work when it is cloudy), still that claim sounds reasonable. However, there is not much point in building solar power that is larger than the day/night consumption variation, since then some means is required to store some energy for the night, making it expensive. A continental wide east-west electric transmission network makes more sense by extending the usability period with some hours, rather than trying to store the energy for the night.
From: dagmargoodboat on 18 Apr 2010 09:50 On Apr 18, 7:35 am, mpm <mpmill...(a)aol.com> wrote: > On Apr 18, 1:56 am, Paul Keinanen <keina...(a)sci.fi> wrote: <snip> > > PV panels on individual houses will make economical sense only in hot > > countries if the cost of energy changes on an hour or shorter bases. > > During hot sunny afternoons, the electric consumption will reach the > > annual peak due to air conditioning. > > > Much of the power during those hours needs to be produced with simple > > cheap gas turbines (used only a limited number of hours each year), > > but the overall efficiency is low and they need to use more expensive > > fuels such as natural gas or oil. > > > If this extra cost during summer day hours is charged from the > > consumers, it would make sense for the consumer to use individual PV > > panels for running the air conditioning, thus avoiding buying > > expensive peak electricity from the power company. In such cases there > > would be less need to have an expensive inverter to feed power back to > > the grid. > > > Of course, simple thermal collectors could be used to drive an > > absorbtion cooler, even if the cooler efficiency is lower than a > > compressor cooler, this avoids the low efficiency light to electricity > > conversion in PV cells. > > > I read a stat somewhere (not sure where, or how true it was, but...) > If the US built 91 miles square (~ 8300sq mi) of solar-thermal, it > would completely satisfy our energy needs, including enough to power > all our cars once converted to electric / hybrids. > I believe that figure also included upgrading the transmission lines. > > We have the desert southwest.... > Do we have the will or desire? > > Maybe we should spend the trillion dollars or so, build this thing, > and finally solve the US energy problem and geopolitical > destabilization problem the oil dependency causes. > Though I wonder if stopping the hemorrhaging of our wealth to oil rich > nations doesn't bring its own problems. The fast, easy, green thing to do is just conserve. We could save a third scarcely trying, with minimal technology or technical risk. Check out Amory Lovins' Stanford lectures--5 x 90 minutes--if you're really into it. They're excellent. http://www.rmi.org/rmi/Stanford+Energy+Lectures Or we could all go the Obama route and, you know, just all have less. Poor people have less energy, and, to some extent, vice versa. -- Cheers, James Arthur
From: Dirk Bruere at NeoPax on 18 Apr 2010 10:19
On 18/04/2010 07:56, Paul Keinanen wrote: > On Sat, 17 Apr 2010 21:14:57 +0100, Dirk Bruere at NeoPax > <dirk.bruere(a)gmail.com> wrote: > >> On 17/04/2010 20:39, Jan Panteltje wrote: >>> On a sunny day (Sat, 17 Apr 2010 11:25:32 -0600) it happened hamilton >>> <hamilton(a)nothere.com> wrote in<hqcqu9$7ve$1(a)news.eternal-september.org>: >>> >>>> On 4/17/2010 10:41 AM, Jan Panteltje wrote: >>>>> On a sunny day (Sat, 17 Apr 2010 08:57:14 -0700) it happened Don Lancaster >>>>> <don(a)tinaja.com> wrote in<82u42oFov7U2(a)mid.individual.net>: >>>>>> There is NO best solution. >>>>>> >>>>>> All of photovoltaics is an outright scam to steal state and federal funds. >>>>>> >>>>>> Not one net watthour of pv energy has EVER been produced! >>>>> >>>>> Bad day? >>>> Ok, the link now works. >>>> >>>> Dons argument is what the non-green types have been saying for years. >>>> >>>> It costs too much to develop and manufacture green technologies then to >>>> stick to the 'tried-n-true' fossil fuels. >>>> >>>> He does have a point, the cost to early adapters will never be paid back. >>>> >>>> But, I think we need to start somewhere, and PV solar needs to have >>>> money to continue to develop and innovate. >>>> >>>> As time passes and science has the money to continue, they will get >>>> there. ( maybe not in my lifetime, but they will get there ) >>>> >>>> >>>> hamilton >>> >>> Yes, there are for example investors in Europe planning a solar plant in the Sahara desert IIRC. >>> Billions have been raised, DC very high voltage lines to carry it all over Europe. >>> With all that unrest I think the biggest obstacle is a political one. >>> US has Mojave desert, would be a nice place for solar .. >>> but the same greens that want solar also want to protect the bugs and snakes that live there ;-) >>> Just wait until get get cold feet, they will change their mind. >>> OTOH nuclear seems to be the only real option right now. >>> And if 'electric cars' were to really happen, then all bets are off, >>> new grid, new power plants... >>> Dunno. >> >> That's why Spain is the ideal location. > > The Desertec plan and the existing stations in Spain and US are based > on concentrated solar thermal power, not PV cells, apparently for > economical reasons. > > In solar thermal plants, the sun heats a fluid which then drives a > conventional gas or steam turbine. It would make even more economical > sense, if the excess heat available on the "cold" end of the turbine > could be used for something useful, such as running absorbtion > chillers or desalination plants. > > PV panels on individual houses will make economical sense only in hot > countries if the cost of energy changes on an hour or shorter bases. > During hot sunny afternoons, the electric consumption will reach the > annual peak due to air conditioning. > > Much of the power during those hours needs to be produced with simple > cheap gas turbines (used only a limited number of hours each year), > but the overall efficiency is low and they need to use more expensive > fuels such as natural gas or oil. > > If this extra cost during summer day hours is charged from the > consumers, it would make sense for the consumer to use individual PV > panels for running the air conditioning, thus avoiding buying > expensive peak electricity from the power company. In such cases there > would be less need to have an expensive inverter to feed power back to > the grid. > > Of course, simple thermal collectors could be used to drive an > absorbtion cooler, even if the cooler efficiency is lower than a > compressor cooler, this avoids the low efficiency light to electricity > conversion in PV cells. Ultimately PV will win out for economic reasons. Right now a sq meter of PV costs the same or more then a square meter of LCD TV screen. As the tech matures you are going to see that sq m drop to around one tenth of that price ie around 10c per peak watt. -- Dirk http://www.transcendence.me.uk/ - Transcendence UK http://www.blogtalkradio.com/onetribe - Occult Talk Show |