harnessing lightning, or not
in [Design]
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From: Winfield Hill on 12 Jun 2010 16:43 Bert Hickman wrote... > > Winfield Hill wrote: >> John Larkin wrote... >>> Winfield Hill wrote: >>> >>>> My Maxwell capacitors hard at work energy from harnessing lightning, >>>> see my post with photo, at the CR4 forum. >>>> http://cr4.globalspec.com/thread/55751/Lightning-Arrestor#comment579837 >> >>> Why not use the lightning to heat water? The impedance match is >>> potentially better, and it's easy to store hot water. We could >>> throw a neighborhood hot-tub party after every strike, every >>> 40 years or so. >> >> Aren't there serious problems with developing a high electric >> field in water? I mean, above about 1V it wants to break apart >> into H2 and O. And what about the electrode double layers? > > Win, > > For short (a few usec or shorter) pulses, water is actually a very good > dielectric. Because of its high permittivity (~80), water is often used > as the dielectric material in high voltage, low impedance transmission > lines and interim capacitive storage units used in high-energy pulsed > power systems, such as Sandia's ZR machine. The shorter the pulse width, > the greater the peak voltage that can be supported across a water gap. > An empirical relationship was developed by J. C. Martin under a uniform > E-field over a range of voltages, pulse times, and electrode area based > upon his work at Sandia: > > F = k*(t^(-1/3))*(A^(-1/10)) > > where: > F = the peak breakdown field (in MV/cm) > t = duration of applied voltage (in microseconds) > A = area (in square cm) > k = 0.3 for water (positive streamers – the normal case) > k = 0.6 for water (a special case where field enhancement is purposely > adjusted to cause streamers to form preferentially from the negative > electrode instead of the positive electrode) > > For example, positive streamer breakdown field (F) for a pair of 100 > square-cm electrodes in water, stressed by a 1 microsecond pulse should > withstand a field of ~189 kV/cm. If we used a 100 nsec pulse, this > increases to ~408 kV/cm, and to ~879 kV/cm for a 10 nsec pulse. YMMV - > media degassing (or outright pressurization) is essential to prevent > premature breakdown. > > Considerably more detail can be found in "High Power Switching" by > Ihor M. Vitkovitsky, ISBN-10 0442290675, “Introduction to High Power > Pulse Technology” by S. T. Pai and Qi Zhang, ISBN-10 9810217145, and > "High-Voltage Electrical Breakdown of Water" by M. Kristiansen and > L Hatfield, ISBN-10 1934939005. > > Breakdown behavior changes with longer (>10 microsecond) pulses, since > ionic conduction begins to alter the E-field distribution within the > gap. Metallic salts are often intentionally added to water to create > high power/high voltage aqueous dummy load and divider resistors for > pulsed power work. The electrolyte and end terminal materials must be > compatible for long-term stability. Some excellent on-line information > sources include a 5 page report from R. E. Beverly III & Associates and > a large (147 page) report from Sandia. > > http://www.reb3.com/pdf/r_appl.pdf > http://www.ece.unm.edu/summa/notes/ESDN/ESDN%205.pdf Thanks, Bert, awesome and inspiring information. And I enjoyed those reports. Hey, do you have copies of those books for sale? > Let me know when you want to begin using that cap to do some > serious EM metal-forming/con shrinking... :^) > > Bert It's high on my list as soon as H&H AoE III is finished. BTW, do you know about the water bridges? -- Thanks, - Win
From: Capt. Cave Man on 12 Jun 2010 17:42 On 12 Jun 2010 13:43:49 -0700, Winfield Hill <Winfield_member(a)newsguy.com> wrote: > BTW, do you know about the water bridges? Hehehe.. I have some Skylab videos on Laser Disc from NASA, of which one is titled "water bridges". Essentially 'fun with water and surface tension and surface adhesion in space'. Jeff's cousin? :-)
From: John Larkin on 12 Jun 2010 18:18 On Sat, 12 Jun 2010 15:29:53 -0500, Bert Hickman <bert-hickman(a)comcast.net> wrote: >Greegor wrote: >> What were these Maxwell capacitors originally built for? > >All sorts of high-energy pulsed-power applications. Typically, banks of >HV metal-cased energy-discharge capacitors are used to supply 10's to >1000's of kilojoules at 100's of kA - MA levels. Common examples include >pulsed magnetizers to charge rare-earth magnets, industrial >electromagnetic metal forming (and coin shrinking), What sort of switch would be used there? When I was a kid, I used to make banks of electrolytics (from old TV sets), charge them up, and dump them into coils using, pretty much, just wire contacts. They welded shut every shot. I could magnetize most anything. John
From: StickThatInYourPipeAndSmokeIt on 12 Jun 2010 18:36 On Sat, 12 Jun 2010 15:18:37 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Sat, 12 Jun 2010 15:29:53 -0500, Bert Hickman ><bert-hickman(a)comcast.net> wrote: > >>Greegor wrote: >>> What were these Maxwell capacitors originally built for? >> >>All sorts of high-energy pulsed-power applications. Typically, banks of >>HV metal-cased energy-discharge capacitors are used to supply 10's to >>1000's of kilojoules at 100's of kA - MA levels. Common examples include >>pulsed magnetizers to charge rare-earth magnets, industrial >>electromagnetic metal forming (and coin shrinking), > >What sort of switch would be used there? When I was a kid, I used to >make banks of electrolytics (from old TV sets), charge them up, and >dump them into coils using, pretty much, just wire contacts. They >welded shut every shot. I could magnetize most anything. > >John http://205.243.100.155/frames/shrinkergallery.html He has some how-to data there, IIRC.
From: StickThatInYourPipeAndSmokeIt on 12 Jun 2010 18:40
On Sat, 12 Jun 2010 15:18:37 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Sat, 12 Jun 2010 15:29:53 -0500, Bert Hickman ><bert-hickman(a)comcast.net> wrote: > >>Greegor wrote: >>> What were these Maxwell capacitors originally built for? >> >>All sorts of high-energy pulsed-power applications. Typically, banks of >>HV metal-cased energy-discharge capacitors are used to supply 10's to >>1000's of kilojoules at 100's of kA - MA levels. Common examples include >>pulsed magnetizers to charge rare-earth magnets, industrial >>electromagnetic metal forming (and coin shrinking), > >What sort of switch would be used there? When I was a kid, I used to >make banks of electrolytics (from old TV sets), charge them up, and >dump them into coils using, pretty much, just wire contacts. They >welded shut every shot. I could magnetize most anything. > >John http://205.243.100.155/frames/gallery/newgap5a.jpg |