<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">boB,<div> <div>I know I'm getting out of my league here but I'm so intrigued. Doesn't a LCB device work on a feedback loop that looks at the output voltage and current to a load and compares it to input voltage? Since we have two fixed values here, 29Ω resistance and 4.15A PV current, how can there be any excess voltage at the circuit input?</div><div><br></div><div>I can see that the PV modules should produce 1kW @ 500W/m2 IF the load allowed it. As Kent said, the resistance would have to change to 58Ω. On the other hand...if I don't understand the function of a LCB...operating the PV module at 170 Vdc would result in 5.87 amps while feeding a 29Ω load. </div><div><br></div><div>Counterpoint? Inquiring minds want to know!</div><div><div>
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><br class="Apple-interchange-newline">Larry Crutcher</div><div>Starlight Solar Power Systems</div></div></span></span><div>(928) 342-9103</div><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><u><a href="http://www.starlightsolar.com">www.starlightsolar.com</a></u></div><div><u><br></u></div></div></span></span></div></span></div></span><br class="Apple-interchange-newline"></span><br class="Apple-interchange-newline">
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<br><div><div>On May 19, 2012, at 10:16 PM, <a href="mailto:boB@midnitesolar.com">boB@midnitesolar.com</a> wrote:</div><br class="Apple-interchange-newline">
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On 5/19/2012 5:47 PM, Larry Crutcher, Starlight Solar Power Systems
wrote:
<blockquote cite="mid:31EC5436-9CFD-43A8-A0F1-9A58C51B659A@starlightsolar.com" type="cite">Good one, Mick. Here's the way I see it:
<div><br>
</div>
<div>For question one, I say yes, other than the obvious wire and
connection losses, because you are operating the cell(s) at the
peak power point.
<div>
<div><br>
</div>
<div>Since a PV solar cell is a constant current device and
your 29 ohm load did not change, reducing your Lab Light
source to 500 W/m2 can only affect the voltage and resulting
power. This means your load forces the voltage down to 120
volts resulting in 500 watts of power dissipated. You have
forced an IV curve shift of current AND voltage.</div>
<div><br>
</div>
<div>The LCB boosts current based on IV curve voltage. I don't
think an LCB can change anything in this scenario since you
have forced the circuit to operate at 120 volts and 4.15
amps.</div>
</div>
</div>
</blockquote>
<br>
<br>
<br>
Realizing that these LCB things run off the PV input because there
is no battery.... If an LCB outputs<br>
maximum current into a fixed resistance, (and therefore maximum
power), kind of like an MPPT<br>
charge controller does, then it ~should~ adjust its voltage "gear
ratio" to maximize the output <br>
current and power. <br>
<br>
At least I think the idea is correct, if the LCB was large enough
and high enough voltage operation<br>
for your application. But then again, I may be missing something
here too.<br>
<br>
<br>
boB<br>
<br>
<br>
<blockquote cite="mid:31EC5436-9CFD-43A8-A0F1-9A58C51B659A@starlightsolar.com" type="cite">
<div>
<div>
<div><br>
</div>
<div>Keep in mind that I'm a solar dummy. My logic may be
faulty.</div>
<div>
<div>
<span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; font-size: medium; "><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; font-size: medium; ">
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</blockquote>
<blockquote cite="mid:31EC5436-9CFD-43A8-A0F1-9A58C51B659A@starlightsolar.com" type="cite">
<div>
<div>
<div>
<div><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; ">
<div style="word-wrap: break-word; -webkit-nbsp-mode:
space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; ">
<div style="word-wrap: break-word;
-webkit-nbsp-mode: space; -webkit-line-break:
after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; ">
<div style="word-wrap: break-word;
-webkit-nbsp-mode: space;
-webkit-line-break: after-white-space; ">
<div>Larry Crutcher</div>
<div>Starlight Solar Power Systems</div>
</div>
</span></span>
<div>(928) 342-9103</div>
<span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; ">
<div style="word-wrap: break-word;
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<div><u><a moz-do-not-send="true" href="http://www.starlightsolar.com/">www.starlightsolar.com</a></u></div>
<div><u><br>
</u></div>
<div><u><br>
</u></div>
</div>
</span></span></div>
</span></div>
</span></span><br class="Apple-interchange-newline">
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<br>
<div>
<div>On May 19, 2012, at 12:35 PM, Mick Abraham wrote:</div>
<br class="Apple-interchange-newline">
<div>Hi, Wrenchies~</div>
<div> </div>
<div>Kindly educate me regarding PV behavior when the load
is a resistor. Here's a hypothetical situation:</div>
<div> </div>
<div>* Eight 250 watt PV modules (60 cells per module),
all connected in series for "peak" ratings of 240 volts
DC & 8.3 amps </div>
<div> </div>
<div>* Lab type cell temperature & illumination so
that the eight would truly pump 2,000 watts <strong><em>into
an ideal load</em></strong></div>
<div> </div>
<div>* A 240 volt AC heating element designed for 2,000
watt heat dissipation at 240 volts AC...that's about 29
ohms resistance for the heat element</div>
<div> </div>
<div>* Connect the PV string to the heat element, with
nothing in between except a fused disconnect.</div>
<div> </div>
<div>In the above situation, would the resistance of the
heating element be all that's needed to force the PV
array to operate near the "peak" wattage?</div>
<div>Would the heater actually get 2,000 watts to turn
into heat?</div>
<div> </div>
<div>+++++++++++++++++++++++++++</div>
<div> </div>
<div>Now consider the same cell temperature but half the
illumination. That's similar voltage but half the amps
at peak wattage. If this is sent into the same 29 ohm</div>
<div>resistor--again with no intervening electronics,
could we count on 1000 watts of heat?</div>
<div> </div>
<div>If the answers come up "no", would the
power throughput be helped by a SolarConverters
style MPPT pump controller (Linear Current Booster kinda
thing), assuming that one could be found to operate in
the 240 volt range?</div>
<div> </div>
<div>Thanks & Jolliness,</div>
<div><br clear="all">
Mick Abraham, Proprietor<br>
<a moz-do-not-send="true" href="http://www.abrahamsolar.com/" target="_blank">www.abrahamsolar.com</a><br>
<br>
</div>
</div>
<br>
</div>
</div>
</div>
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