On Thu, 19 Jul 2012 15:14:04 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>Tim Wescott wrote: >> >> On Thu, 19 Jul 2012 14:11:44 -0500, Tim Wescott wrote: >> >> > On Thu, 19 Jul 2012 14:50:00 +0100, Martin Brown wrote: >> > >> >> On 19/07/2012 14:29, Phil Hobbs wrote: >> >>> Martin Brown wrote: >> >> >> >>>> Current. They are in essence a bunch of high power diode PN >> >>>> junctions. >> >>> >> >>> I'd control them individually, or wire them in series. Compound >> >>> Peltiers have a nasty thermal instability, where they start getting >> >>> hotter as you go to higher current instead of colder. >> >>> >> >>> If you put them in series, they all see the same current, which along >> >>> with a spreader plate top and bottom) helps prevent runaway. If you >> >>> put them in parallel, the ones with higher delta-T will draw less >> >>> current than the lower delta-T ones, which gives you a nice >> >>> stabilizing action at low drive current. >> >>> >> >>> If you push them, or you lose cooling water to your heat exchanger, >> >>> the sign of the gain can invert and the whole thing turns to lava very >> >>> fast. (That can happen with individual control or series-connection >> >>> as well, but the melty ones can't hog current from the cooler ones, so >> >>> it isn't so unstable.) >> >>> >> >>> The other thing is that you have to allow the Peltiers to slide around >> >>> a bit as the cold plate cools down, because otherwise they'll crack. >> >>> So use Arctic Silver or a very small amount of very good thermal >> >>> grease on one side, and solder on the other. IIRC you can solder the >> >>> 30 mm ones, but not the 50 mm ones--it'll be in the datasheet. (Solder >> >>> is about 100x better than ordinary thermal grease.) >> >>> >> >>> I talk a lot about Peltiers in my free thermal chapter, >> >>> http://electrooptical.net/www/book/thermal.pdf . There's also an >> >>> incomplete draft that was intended to accompany the second edition, >> >>> which has some more stuff in it, at >> >>> http://electrooptical.net/www/book/draftthermal.pdf . >> >> >> >> Handy info thanks. Although the TECs are available their datasheets are >> >> often inadequate and miss out details needed for real world designs. >> >> >> >> Can I pick your brains for a slightly odd requirement? Ideally one that >> >> can be done with at most a pair of TECs one high temp and one normal. >> >> On paper they were rated for 3A and 14v or so each but in practice I >> >> was struggling in reverse to get 2v and a few mA out with a candle >> >> flame heated plate at 250C on one side and a slab of aluminium at -18C >> >> on the other. I gave up in the end as it was taking too long and safety >> >> concerns of very hot metal plates and children scuppered it in the end. >> >> >> >> The aim would be for an Xmas science demo to harvest some of the ~100W >> >> waste heat of a candle flame and drive a ~1W LED. This seemed a modest >> >> aim when I started out but in practice it proved impossible. To be any >> >> good the LED must be a *lot* brighter than the candle flame! >> >> >> >> I am guessing that to stand any chance I also need a fan assisted heat >> >> sink and to be authentic it must all be powered by the TECs. It is for >> >> a physics demo so hiding a button cell somewhere is just not on... >> > >> > You may do much better with a fan-powered Sterling engine. >> >> CANDLE-powered Sterling. Oops. >> >> > Or, for a complete demo, have one TE element complete with lots of hype, >> > and one "150 year old technology" Sterling engine for comparison... >> >> -- > >Of course, TECs are 60-year-old technology....Yup. My father designed a TEC refrigerator in the late '50s or very early '60s, complete with a solid-state power supply (string of Germanium DO-3 PNPs). I had a couple of them in the basement to play with when I was a kid. It was designed to go in a car but never made it past prototype. It got beat out by Styrofoam disposables. ;-)
Muliple Peltier elements: parallel or series?
Started by ●July 19, 2012
Reply by ●July 19, 20122012-07-19
Reply by ●July 19, 20122012-07-19
On 7/19/2012 12:25 PM, George Herold wrote:> On Jul 19, 11:44 am, Syd Rumpo <use...@neonica.co.uk> wrote: >> On 19/07/2012 15:45, Jan Panteltje wrote: >> >>> On a sunny day (Thu, 19 Jul 2012 14:50:00 +0100) it happened Martin Brown >>> <|||newspam...@nezumi.demon.co.uk> wrote in >>> <1gUNr.50376$iI7.22...@newsfe03.iad>: >> >>>> The aim would be for an Xmas science demo to harvest some of the ~100W >>>> waste heat of a candle flame and drive a ~1W LED. This seemed a modest >>>> aim when I started out but in practice it proved impossible. To be any >>>> good the LED must be a *lot* brighter than the candle flame! >> >>> I would use a thermocouple (or some i nseries) and a JFET oscillator with step up transformer. >>> JFET oscillators oscillate from about next to zero volts up. >>> Have not tried it on a thermocouple, but did try the low voltage JFET oscillator. >>> Only a few parts needed... >> >> I'd go with several thermocouples in series. The advantage over a >> Peltier is that you can have the cold junctions some way from the heat. >> >> Say use Iron/Constantan at about 55uV/K so for 1.8V at 200C you'd need >> about 160 thermocouples which is doable I reckon, probably many fewer >> depending on flame temperature. You can just twist the ends together to >> make the junctions, should last a while. >> >> Cheers >> -- >> Syd > > Hey, speaking of thermopiles I heard Hamamatsu has a new line of them. > http://www.hamamatsu.com/news/2011/2011_09_21.html > > I can't find a spec sheet or price though. > > George H. >Peltier Coolers are almost always totally worthless. Their delta T across the heatsink usually EXCEEDS their intended delta T drop See < http://www.tinaja.com/glib/hack68.pdf > -- Many thanks, Don Lancaster voice phone: (928)428-4073 Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552 rss: http://www.tinaja.com/whtnu.xml email: don@tinaja.com Please visit my GURU's LAIR web site at http://www.tinaja.com
Reply by ●July 19, 20122012-07-19
Don Lancaster wrote:> > On 7/19/2012 12:25 PM, George Herold wrote: > > On Jul 19, 11:44 am, Syd Rumpo <use...@neonica.co.uk> wrote: > >> On 19/07/2012 15:45, Jan Panteltje wrote: > >> > >>> On a sunny day (Thu, 19 Jul 2012 14:50:00 +0100) it happened Martin Brown > >>> <|||newspam...@nezumi.demon.co.uk> wrote in > >>> <1gUNr.50376$iI7.22...@newsfe03.iad>: > >> > >>>> The aim would be for an Xmas science demo to harvest some of the ~100W > >>>> waste heat of a candle flame and drive a ~1W LED. This seemed a modest > >>>> aim when I started out but in practice it proved impossible. To be any > >>>> good the LED must be a *lot* brighter than the candle flame! > >> > >>> I would use a thermocouple (or some i nseries) and a JFET oscillator with step up transformer. > >>> JFET oscillators oscillate from about next to zero volts up. > >>> Have not tried it on a thermocouple, but did try the low voltage JFET oscillator. > >>> Only a few parts needed... > >> > >> I'd go with several thermocouples in series. The advantage over a > >> Peltier is that you can have the cold junctions some way from the heat. > >> > >> Say use Iron/Constantan at about 55uV/K so for 1.8V at 200C you'd need > >> about 160 thermocouples which is doable I reckon, probably many fewer > >> depending on flame temperature. You can just twist the ends together to > >> make the junctions, should last a while. > >> > >> Cheers > >> -- > >> Syd > > > > Hey, speaking of thermopiles I heard Hamamatsu has a new line of them. > > http://www.hamamatsu.com/news/2011/2011_09_21.html > > > > I can't find a spec sheet or price though. > > > > George H. > > > > Peltier Coolers are almost always totally worthless. > Their delta T across the heatsink usually EXCEEDS their intended delta T > drop > > See < http://www.tinaja.com/glib/hack68.pdf > > > -- > Many thanks, > > Don LancasterNonsense. If you try cooling a CPU or a voltage regulator with one, you deserve what you get. But many kinds of instruments would be far harder to build without them. Oh, and of course the telecom infrastructure wouldn't work without them either, because Peltiers are what keep all the DWDM lasers from scribbling across neighbouring channels. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●July 19, 20122012-07-19
On 20 Jul., 00:59, "k...@att.bizzzzzzzzzzzz" <k...@att.bizzzzzzzzzzzz> wrote:> On Thu, 19 Jul 2012 15:14:04 -0400, Phil Hobbs > > > > > > > > > > <pcdhSpamMeSensel...@electrooptical.net> wrote: > >Tim Wescott wrote: > > >> On Thu, 19 Jul 2012 14:11:44 -0500, Tim Wescott wrote: > > >> > On Thu, 19 Jul 2012 14:50:00 +0100, Martin Brown wrote: > > >> >> On 19/07/2012 14:29, Phil Hobbs wrote: > >> >>> Martin Brown wrote: > > >> >>>> Current. They are in essence a bunch of high power diode PN > >> >>>> junctions. > > >> >>> I'd control them individually, or wire them in series. =A0Compound > >> >>> Peltiers have a nasty thermal instability, where they start gettin=g> >> >>> hotter as you go to higher current instead of colder. > > >> >>> If you put them in series, they all see the same current, which al=ong> >> >>> with a spreader plate top and bottom) helps prevent runaway. =A0If=you> >> >>> put them in parallel, the ones with higher delta-T will draw less > >> >>> current than the lower delta-T ones, which gives you a nice > >> >>> stabilizing action at low drive current. > > >> >>> If you push them, or you lose cooling water to your heat exchanger=,> >> >>> the sign of the gain can invert and the whole thing turns to lava =very> >> >>> fast. =A0(That can happen with individual control or series-connec=tion> >> >>> as well, but the melty ones can't hog current from the cooler ones=, so> >> >>> it isn't so unstable.) > > >> >>> The other thing is that you have to allow the Peltiers to slide ar=ound> >> >>> a bit as the cold plate cools down, because otherwise they'll crac=k.> >> >>> So use Arctic Silver or a very small amount of very good thermal > >> >>> grease on one side, and solder on the other. =A0IIRC you can solde=r the> >> >>> 30 mm ones, but not the 50 mm ones--it'll be in the datasheet. (So=lder> >> >>> is about 100x better than ordinary thermal grease.) > > >> >>> I talk a lot about Peltiers in my free thermal chapter, > >> >>>http://electrooptical.net/www/book/thermal.pdf. =A0There's also an > >> >>> incomplete draft that was intended to accompany the second edition=,> >> >>> which has some more stuff in it, at > >> >>>http://electrooptical.net/www/book/draftthermal.pdf. > > >> >> Handy info thanks. Although the TECs are available their datasheets=are> >> >> often inadequate and miss out details needed for real world designs=.> > >> >> Can I pick your brains for a slightly odd requirement? Ideally one =that> >> >> can be done with at most a pair of TECs one high temp and one norma=l.> >> >> On paper they were rated for 3A and 14v or so each but in practice =I> >> >> was struggling in reverse to get 2v and a few mA out with a candle > >> >> flame heated plate at 250C on one side and a slab of aluminium at -=18C> >> >> on the other. I gave up in the end as it was taking too long and sa=fety> >> >> concerns of very hot metal plates and children scuppered it in the =end.> > >> >> The aim would be for an Xmas science demo to harvest some of the ~1=00W> >> >> waste heat of a candle flame and drive a ~1W LED. This seemed a mod=est> >> >> aim when I started out but in practice it proved impossible. To be =any> >> >> good the LED must be a *lot* brighter than the candle flame! > > >> >> I am guessing that to stand any chance I also need a fan assisted h=eat> >> >> sink and to be authentic it must all be powered by the TECs. It is =for> >> >> a physics demo so hiding a button cell somewhere is just not on... > > >> > You may do much better with a fan-powered Sterling engine. > > >> CANDLE-powered Sterling. =A0Oops. > > >> > Or, for a complete demo, have one TE element complete with lots of h=ype,> >> > and one "150 year old technology" Sterling engine for comparison... > > >> -- > > >Of course, TECs are 60-year-old technology.... > > Yup. =A0My father designed a TEC refrigerator in the late '50s or very ea=rly> '60s, complete with a solid-state power supply (string of Germanium DO-3 > PNPs). =A0I had a couple of them in the basement to play with when I was =a kid.> It was designed to go in a car but never made it past prototype. =A0It go=t beat> out by Styrofoam disposables. =A0;-)you can get plenty of 12V TEC refrigerators/coolers but I don't think they have much if any smarts in them, they just say something like "up to 20'C below ambient" -Lasse
Reply by ●July 19, 20122012-07-19
On Thu, 19 Jul 2012 16:38:19 -0700 (PDT), "langwadt@fonz.dk" <langwadt@fonz.dk> wrote:>On 20 Jul., 00:59, "k...@att.bizzzzzzzzzzzz" <k...@att.bizzzzzzzzzzzz> >wrote: >> On Thu, 19 Jul 2012 15:14:04 -0400, Phil Hobbs >> >> >> >> >> >> >> >> >> >> <pcdhSpamMeSensel...@electrooptical.net> wrote: >> >Tim Wescott wrote: >> >> >> On Thu, 19 Jul 2012 14:11:44 -0500, Tim Wescott wrote: >> >> >> > On Thu, 19 Jul 2012 14:50:00 +0100, Martin Brown wrote: >> >> >> >> On 19/07/2012 14:29, Phil Hobbs wrote: >> >> >>> Martin Brown wrote: >> >> >> >>>> Current. They are in essence a bunch of high power diode PN >> >> >>>> junctions. >> >> >> >>> I'd control them individually, or wire them in series. �Compound >> >> >>> Peltiers have a nasty thermal instability, where they start getting >> >> >>> hotter as you go to higher current instead of colder. >> >> >> >>> If you put them in series, they all see the same current, which along >> >> >>> with a spreader plate top and bottom) helps prevent runaway. �If you >> >> >>> put them in parallel, the ones with higher delta-T will draw less >> >> >>> current than the lower delta-T ones, which gives you a nice >> >> >>> stabilizing action at low drive current. >> >> >> >>> If you push them, or you lose cooling water to your heat exchanger, >> >> >>> the sign of the gain can invert and the whole thing turns to lava very >> >> >>> fast. �(That can happen with individual control or series-connection >> >> >>> as well, but the melty ones can't hog current from the cooler ones, so >> >> >>> it isn't so unstable.) >> >> >> >>> The other thing is that you have to allow the Peltiers to slide around >> >> >>> a bit as the cold plate cools down, because otherwise they'll crack. >> >> >>> So use Arctic Silver or a very small amount of very good thermal >> >> >>> grease on one side, and solder on the other. �IIRC you can solder the >> >> >>> 30 mm ones, but not the 50 mm ones--it'll be in the datasheet. (Solder >> >> >>> is about 100x better than ordinary thermal grease.) >> >> >> >>> I talk a lot about Peltiers in my free thermal chapter, >> >> >>>http://electrooptical.net/www/book/thermal.pdf. �There's also an >> >> >>> incomplete draft that was intended to accompany the second edition, >> >> >>> which has some more stuff in it, at >> >> >>>http://electrooptical.net/www/book/draftthermal.pdf. >> >> >> >> Handy info thanks. Although the TECs are available their datasheets are >> >> >> often inadequate and miss out details needed for real world designs. >> >> >> >> Can I pick your brains for a slightly odd requirement? Ideally one that >> >> >> can be done with at most a pair of TECs one high temp and one normal. >> >> >> On paper they were rated for 3A and 14v or so each but in practice I >> >> >> was struggling in reverse to get 2v and a few mA out with a candle >> >> >> flame heated plate at 250C on one side and a slab of aluminium at -18C >> >> >> on the other. I gave up in the end as it was taking too long and safety >> >> >> concerns of very hot metal plates and children scuppered it in the end. >> >> >> >> The aim would be for an Xmas science demo to harvest some of the ~100W >> >> >> waste heat of a candle flame and drive a ~1W LED. This seemed a modest >> >> >> aim when I started out but in practice it proved impossible. To be any >> >> >> good the LED must be a *lot* brighter than the candle flame! >> >> >> >> I am guessing that to stand any chance I also need a fan assisted heat >> >> >> sink and to be authentic it must all be powered by the TECs. It is for >> >> >> a physics demo so hiding a button cell somewhere is just not on... >> >> >> > You may do much better with a fan-powered Sterling engine. >> >> >> CANDLE-powered Sterling. �Oops. >> >> >> > Or, for a complete demo, have one TE element complete with lots of hype, >> >> > and one "150 year old technology" Sterling engine for comparison... >> >> >> -- >> >> >Of course, TECs are 60-year-old technology.... >> >> Yup. �My father designed a TEC refrigerator in the late '50s or very early >> '60s, complete with a solid-state power supply (string of Germanium DO-3 >> PNPs). �I had a couple of them in the basement to play with when I was a kid. >> It was designed to go in a car but never made it past prototype. �It got beat >> out by Styrofoam disposables. �;-) > >you can get plenty of 12V TEC refrigerators/coolers but I don't think >they have >much if any smarts in them, they just say something like "up to 20'C >below ambient"Fifty years ago you couldn't. ;-)
Reply by ●July 19, 20122012-07-19
"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message news:500898F2.67E349F@electrooptical.net...> Don Lancaster wrote: >> >> On 7/19/2012 12:25 PM, George Herold wrote: >> > On Jul 19, 11:44 am, Syd Rumpo <use...@neonica.co.uk> wrote: >> >> On 19/07/2012 15:45, Jan Panteltje wrote: >> >> >> >>> On a sunny day (Thu, 19 Jul 2012 14:50:00 +0100) it happened Martin >> >>> Brown >> >>> <|||newspam...@nezumi.demon.co.uk> wrote in >> >>> <1gUNr.50376$iI7.22...@newsfe03.iad>: >> >> >> >>>> The aim would be for an Xmas science demo to harvest some of the >> >>>> ~100W >> >>>> waste heat of a candle flame and drive a ~1W LED. This seemed a >> >>>> modest >> >>>> aim when I started out but in practice it proved impossible. To be >> >>>> any >> >>>> good the LED must be a *lot* brighter than the candle flame! >> >> >> >>> I would use a thermocouple (or some i nseries) and a JFET oscillator >> >>> with step up transformer. >> >>> JFET oscillators oscillate from about next to zero volts up. >> >>> Have not tried it on a thermocouple, but did try the low voltage JFET >> >>> oscillator. >> >>> Only a few parts needed... >> >> >> >> I'd go with several thermocouples in series. The advantage over a >> >> Peltier is that you can have the cold junctions some way from the >> >> heat. >> >> >> >> Say use Iron/Constantan at about 55uV/K so for 1.8V at 200C you'd need >> >> about 160 thermocouples which is doable I reckon, probably many fewer >> >> depending on flame temperature. You can just twist the ends together >> >> to >> >> make the junctions, should last a while. >> >> >> >> Cheers >> >> -- >> >> Syd >> > >> > Hey, speaking of thermopiles I heard Hamamatsu has a new line of them. >> > http://www.hamamatsu.com/news/2011/2011_09_21.html >> > >> > I can't find a spec sheet or price though. >> > >> > George H. >> > >> >> Peltier Coolers are almost always totally worthless. >> Their delta T across the heatsink usually EXCEEDS their intended delta T >> drop >> >> See < http://www.tinaja.com/glib/hack68.pdf > >> >> -- >> Many thanks, >> >> Don Lancaster > > Nonsense. > > If you try cooling a CPU or a voltage regulator with one, you deserve > what you get. But many kinds of instruments would be far harder to > build without them. Oh, and of course the telecom infrastructure > wouldn't work without them either, because Peltiers are what keep all > the DWDM lasers from scribbling across neighbouring channels. >I think he implies that in his paper. Certain special applications are ideal for TECs. tm
Reply by ●July 19, 20122012-07-19
On Jul 19, 4:33=A0pm, "tm" <No_one_h...@white-house.gov> wrote:> "George Herold" <gher...@teachspin.com> wrote in message > > news:8439768c-44bb-4288-820d-b4a862190f10@n33g2000vbi.googlegroups.com... > On Jul 19, 10:47 am, "tm" <No_one_h...@white-house.gov> wrote: > > > > > > > "George Herold" <gher...@teachspin.com> wrote in message > > >news:68a5592b-2d41-467f-aa95-1748583a3e2a@s1g2000vbj.googlegroups.com... > > On Jul 19, 9:50 am, Martin Brown <|||newspam...@nezumi.demon.co.uk> > > wrote: > > > > On 19/07/2012 14:29, Phil Hobbs wrote: > > > > > Martin Brown wrote: > > > >> Current. They are in essence a bunch of high power diode PN > > > >> junctions. > > > > > I'd control them individually, or wire them in series. Compound > > > > Peltiers have a nasty thermal instability, where they start getting > > > > hotter as you go to higher current instead of colder. > > > > > If you put them in series, they all see the same current, which alo=ng> > > > with a spreader plate top and bottom) helps prevent runaway. If you > > > > put > > > > them in parallel, the ones with higher delta-T will draw less curre=nt> > > > than the lower delta-T ones, which gives you a nice stabilizing act=ion> > > > at low drive current. > > > > > If you push them, or you lose cooling water to your heat exchanger, > > > > the > > > > sign of the gain can invert and the whole thing turns to lava very > > > > fast. (That can happen with individual control or series-connection=as> > > > well, but the melty ones can't hog current from the cooler ones, so=it> > > > isn't so unstable.) > > > > > The other thing is that you have to allow the Peltiers to slide aro=und> > > > a > > > > bit as the cold plate cools down, because otherwise they'll crack. =So> > > > use Arctic Silver or a very small amount of very good thermal greas=e> > > > on > > > > one side, and solder on the other. IIRC you can solder the 30 mm on=es,> > > > but not the 50 mm ones--it'll be in the datasheet. (Solder is about > > > > 100x > > > > better than ordinary thermal grease.) > > > > > I talk a lot about Peltiers in my free thermal chapter, > > > >http://electrooptical.net/www/book/thermal.pdf. There's also an > > > > incomplete draft that was intended to accompany the second edition, > > > > which has some more stuff in it, at > > > >http://electrooptical.net/www/book/draftthermal.pdf. > > > > Handy info thanks. Although the TECs are available their datasheets a=re> > > often inadequate and miss out details needed for real world designs. > > > > Can I pick your brains for a slightly odd requirement? Ideally one th=at> > > can be done with at most a pair of TECs one high temp and one normal.=On> > > paper they were rated for 3A and 14v or so each but in practice I was > > > struggling in reverse to get 2v and a few mA out with a candle flame > > > heated plate at 250C on one side and a slab of aluminium at -18C on t=he> > > other. I gave up in the end as it was taking too long and safety > > > concerns of very hot metal plates and children scuppered it in the en=d.> > > > The aim would be for an Xmas science demo to harvest some of the ~100=W> > > waste heat of a candle flame and drive a ~1W LED. This seemed a modes=t> > > aim when I started out but in practice it proved impossible. To be an=y> > > good the LED must be a *lot* brighter than the candle flame! > > > > I am guessing that to stand any chance I also need a fan assisted hea=t> > > sink and to be authentic it must all be powered by the TECs. It is fo=r a> > > physics demo so hiding a button cell somewhere is just not on... > > > > -- > > > Regards, > > > Martin Brown- Hide quoted text - > > > > - Show quoted text - > > > Interesting, I take your question to be, "Where along the I/V curve > > is a TEC most efficient when run as a generator?" (heat to electric > > power.) > > That should be fairly easy to determine experimentally. > > > Perhaps you need more elements in series? > > > And how did you get the -18C? > > If this is in the winter time perhaps you'd allow for the cold end to > > be dunked into an ice bath... cooled with snow from the great > > outdoors. > > > George H. > > _______________________________________________ > > > It's been a while but I have worked with thermal electric generators (T=EG)> > that used propane and a catalytic heater as a power source. The unit wa=s> > made by Teledyne Energy Systems. I don't know if they are still around. > > > When I met with their engineers, I ask about the TEC make-up. They did =say> > that it was optimized to be a generator. It used different junctions th=an> > what was used for heating/cooling applications. I don't remember much m=ore> > other than it was made up of five modules, each running about 6 volts a=nd> > 2 > > amps. Overall, it did run at 28 volts and provided 50 watts of power. I=t> > consumed a 100 gal tank in about two weeks. > > > Please don't hold me to exact numbers, it was more than 20 years ago. > > > Regards, > > Tom- Hide quoted text - > > > - Show quoted text - > > Interesting thanks.... punching numbers... > 1 gal gas ~ 33kW*hr > 100gals =3D 3,300 kW*hr. > 50 watts for two weeks ~17 kW*hr > eff. ~ 0.5% > > George H. > > _____________________________________________________ > > Again, I may be mis-remembering the exact quantity of propane. It might h=ave> been 100 pounds. > > What do the numbers look like for 1000 gallons and one year? We used it t=o> run a mountain top microwave relay site with no commercial power within > miles. We refueled it in the summer. It lasted for more than 5 years unti=l> development brought power closer to the site (an old fire tower). The mos=t> important thing is to get the combustion products out of the shelter as a > lot of water vapor is produced. It sure beat solar because of the problem=s> with snow. > > I believe the efficiency was much better than 0.5 % , more like 5% or > better. > > Back of the envelope shows 13% > > Regards, > tm- Hide quoted text - > > - Show quoted text -Oh propane. I was getting my numbers from here. http://en.wikipedia.org/wiki/Gasoline_gallon_equivalent But don't worry about exact numbers George H.
Reply by ●July 19, 20122012-07-19
On Jul 19, 7:22=A0pm, Don Lancaster <d...@tinaja.com> wrote:> On 7/19/2012 12:25 PM, George Herold wrote: > > > > > > > On Jul 19, 11:44 am, Syd Rumpo <use...@neonica.co.uk> wrote: > >> On 19/07/2012 15:45, Jan Panteltje wrote: > > >>> On a sunny day (Thu, 19 Jul 2012 14:50:00 +0100) it happened Martin B=rown> >>> <|||newspam...@nezumi.demon.co.uk> wrote in > >>> <1gUNr.50376$iI7.22...@newsfe03.iad>: > > >>>> The aim would be for an Xmas science demo to harvest some of the ~10=0W> >>>> waste heat of a candle flame and drive a ~1W LED. This seemed a mode=st> >>>> aim when I started out but in practice it proved impossible. To be a=ny> >>>> good the LED must be a *lot* brighter than the candle flame! > > >>> I would use a thermocouple (or some i nseries) and a JFET oscillator =with step up transformer.> >>> JFET oscillators oscillate from about next to zero volts up. > >>> Have not tried it on a thermocouple, but did try the low voltage JFET=oscillator.> >>> Only a few parts needed... > > >> I'd go with several thermocouples in series. =A0The advantage over a > >> Peltier is that you can have the cold junctions some way from the heat=.> > >> Say use Iron/Constantan at about 55uV/K so for 1.8V at 200C you'd need > >> about 160 thermocouples which is doable I reckon, probably many fewer > >> depending on flame temperature. =A0You can just twist the ends togethe=r to> >> make the junctions, should last a while. > > >> Cheers > >> -- > >> Syd > > > Hey, speaking of thermopiles I heard Hamamatsu has a new line of them. > >http://www.hamamatsu.com/news/2011/2011_09_21.html > > > I can't find a spec sheet or price though. > > > George H. > > Peltier Coolers are almost always totally worthless. > Their delta T across the heatsink usually EXCEEDS their intended delta T > drop > > See <http://www.tinaja.com/glib/hack68.pdf> > > -- > Many thanks, > > Don Lancaster =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0voice ph=one: (928)428-4073> Synergetics =A0 3860 West First Street =A0 Box 809 Thatcher, AZ 85552 > rss:http://www.tinaja.com/whtnu.xml=A0 email: d...@tinaja.com > > Please visit my GURU's LAIR web site athttp://www.tinaja.com- Hide quoted=text -> > - Show quoted text -Hi Don, I've used TEC's successfully in two applications. Diode laser temp control. (done before) And controlling the temp of a permanent magnetic. The trick for the magnet was to just stabilize the magnet at whatever the room temperature is... and not try and drag it to any specific temp. (This is to do NMR and we can adjust the frequency to whatever the B field is.) As Phil H. said the great thing about TEC's is they 'go both ways'. George H.
Reply by ●July 19, 20122012-07-19
tm wrote:> > "Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message > news:500898F2.67E349F@electrooptical.net... > > Don Lancaster wrote: > >> > >> On 7/19/2012 12:25 PM, George Herold wrote: > >> > On Jul 19, 11:44 am, Syd Rumpo <use...@neonica.co.uk> wrote: > >> >> On 19/07/2012 15:45, Jan Panteltje wrote: > >> >> > >> >>> On a sunny day (Thu, 19 Jul 2012 14:50:00 +0100) it happened Martin > >> >>> Brown > >> >>> <|||newspam...@nezumi.demon.co.uk> wrote in > >> >>> <1gUNr.50376$iI7.22...@newsfe03.iad>: > >> >> > >> >>>> The aim would be for an Xmas science demo to harvest some of the > >> >>>> ~100W > >> >>>> waste heat of a candle flame and drive a ~1W LED. This seemed a > >> >>>> modest > >> >>>> aim when I started out but in practice it proved impossible. To be > >> >>>> any > >> >>>> good the LED must be a *lot* brighter than the candle flame! > >> >> > >> >>> I would use a thermocouple (or some i nseries) and a JFET oscillator > >> >>> with step up transformer. > >> >>> JFET oscillators oscillate from about next to zero volts up. > >> >>> Have not tried it on a thermocouple, but did try the low voltage JFET > >> >>> oscillator. > >> >>> Only a few parts needed... > >> >> > >> >> I'd go with several thermocouples in series. The advantage over a > >> >> Peltier is that you can have the cold junctions some way from the > >> >> heat. > >> >> > >> >> Say use Iron/Constantan at about 55uV/K so for 1.8V at 200C you'd need > >> >> about 160 thermocouples which is doable I reckon, probably many fewer > >> >> depending on flame temperature. You can just twist the ends together > >> >> to > >> >> make the junctions, should last a while. > >> >> > >> >> Cheers > >> >> -- > >> >> Syd > >> > > >> > Hey, speaking of thermopiles I heard Hamamatsu has a new line of them. > >> > http://www.hamamatsu.com/news/2011/2011_09_21.html > >> > > >> > I can't find a spec sheet or price though. > >> > > >> > George H. > >> > > >> > >> Peltier Coolers are almost always totally worthless. > >> Their delta T across the heatsink usually EXCEEDS their intended delta T > >> drop > >> > >> See < http://www.tinaja.com/glib/hack68.pdf > > >> > >> -- > >> Many thanks, > >> > >> Don Lancaster > > > > Nonsense. > > > > If you try cooling a CPU or a voltage regulator with one, you deserve > > what you get. But many kinds of instruments would be far harder to > > build without them. Oh, and of course the telecom infrastructure > > wouldn't work without them either, because Peltiers are what keep all > > the DWDM lasers from scribbling across neighbouring channels. > > > > I think he implies that in his paper. Certain special applications are ideal > for TECs. > > tmSetting up a straw man and then knocking it down is an old rhetorical amusement, but IMO it's beneath engineers of Don's calibre. Of course he's been in the biz for probably 50 years or more, and so feels entitled to take the occasional potshot from his porch, and who's to say that isn't OK. I bought a copy of his TTL Cookbook in about 1974, when I was 14 years old, and it helped me a lot back then, and for several years thereafter. I was also intrigued by his TV Typewriters, but since I couldn't type they weren't that compelling. They were really just a tease anyway, aimed at those of us who didn't have our own private PDP-10. However, saying that "Peltier coolers are almost always totally worthless", when in fact they enable most of modern communications and the Internet, is just plain nonsense, and needs to be called out. Maybe it'll improve Don's aim. ;) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●July 19, 20122012-07-19
"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message news:5008B5EA.D651DCA@electrooptical.net...> tm wrote: >> >> "Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message >> news:500898F2.67E349F@electrooptical.net... >> > Don Lancaster wrote: >> >> >> >> On 7/19/2012 12:25 PM, George Herold wrote: >> >> > On Jul 19, 11:44 am, Syd Rumpo <use...@neonica.co.uk> wrote: >> >> >> On 19/07/2012 15:45, Jan Panteltje wrote: >> >> >> >> >> >>> On a sunny day (Thu, 19 Jul 2012 14:50:00 +0100) it happened >> >> >>> Martin >> >> >>> Brown >> >> >>> <|||newspam...@nezumi.demon.co.uk> wrote in >> >> >>> <1gUNr.50376$iI7.22...@newsfe03.iad>: >> >> >> >> >> >>>> The aim would be for an Xmas science demo to harvest some of the >> >> >>>> ~100W >> >> >>>> waste heat of a candle flame and drive a ~1W LED. This seemed a >> >> >>>> modest >> >> >>>> aim when I started out but in practice it proved impossible. To >> >> >>>> be >> >> >>>> any >> >> >>>> good the LED must be a *lot* brighter than the candle flame! >> >> >> >> >> >>> I would use a thermocouple (or some i nseries) and a JFET >> >> >>> oscillator >> >> >>> with step up transformer. >> >> >>> JFET oscillators oscillate from about next to zero volts up. >> >> >>> Have not tried it on a thermocouple, but did try the low voltage >> >> >>> JFET >> >> >>> oscillator. >> >> >>> Only a few parts needed... >> >> >> >> >> >> I'd go with several thermocouples in series. The advantage over a >> >> >> Peltier is that you can have the cold junctions some way from the >> >> >> heat. >> >> >> >> >> >> Say use Iron/Constantan at about 55uV/K so for 1.8V at 200C you'd >> >> >> need >> >> >> about 160 thermocouples which is doable I reckon, probably many >> >> >> fewer >> >> >> depending on flame temperature. You can just twist the ends >> >> >> together >> >> >> to >> >> >> make the junctions, should last a while. >> >> >> >> >> >> Cheers >> >> >> -- >> >> >> Syd >> >> > >> >> > Hey, speaking of thermopiles I heard Hamamatsu has a new line of >> >> > them. >> >> > http://www.hamamatsu.com/news/2011/2011_09_21.html >> >> > >> >> > I can't find a spec sheet or price though. >> >> > >> >> > George H. >> >> > >> >> >> >> Peltier Coolers are almost always totally worthless. >> >> Their delta T across the heatsink usually EXCEEDS their intended delta >> >> T >> >> drop >> >> >> >> See < http://www.tinaja.com/glib/hack68.pdf > >> >> >> >> -- >> >> Many thanks, >> >> >> >> Don Lancaster >> > >> > Nonsense. >> > >> > If you try cooling a CPU or a voltage regulator with one, you deserve >> > what you get. But many kinds of instruments would be far harder to >> > build without them. Oh, and of course the telecom infrastructure >> > wouldn't work without them either, because Peltiers are what keep all >> > the DWDM lasers from scribbling across neighbouring channels. >> > >> >> I think he implies that in his paper. Certain special applications are >> ideal >> for TECs. >> >> tm > > Setting up a straw man and then knocking it down is an old rhetorical > amusement, but IMO it's beneath engineers of Don's calibre. Of course > he's been in the biz for probably 50 years or more, and so feels > entitled to take the occasional potshot from his porch, and who's to say > that isn't OK. > > I bought a copy of his TTL Cookbook in about 1974, when I was 14 years > old, and it helped me a lot back then, and for several years > thereafter. I was also intrigued by his TV Typewriters, but since I > couldn't type they weren't that compelling. They were really just a > tease anyway, aimed at those of us who didn't have our own private > PDP-10. > > However, saying that "Peltier coolers are almost always totally > worthless", when in fact they enable most of modern communications and > the Internet, is just plain nonsense, and needs to be called out. Maybe > it'll improve Don's aim. ;) > > Cheers > > Phil Hobbs > > --Well, saying "they enable most of modern communications and the internet" is a bit Algoreish in its own right. :) I have yet to see a 10 gig SFP long haul module that is cooled. I would guess a good bit of the Internet uses them. tm
