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<body class='hmmessage'><div dir='ltr'>Thanks, David.<br><br>I have got some reply from other researchers that the Faraday loss is mainly resulting from the unwanted chemical byproduct during the electrolysis process, and thus they are not accounted as heat generation in the electrolyzer (Although some unwanted chemical reactions indeed release some heat).<br><br>This is the reason that the heat generation in the electrolyzer model Type160 is calculated as "Pely*(1-eta_e)" rather than "Pely*(1-eta_tot)".<br><br>Kind Regards,<br>Sunliang Cao <br><br><br><br><div><hr id="stopSpelling">Date: Thu, 20 Nov 2014 14:54:07 -0600<br>From: d.bradley@tess-inc.com<br>To: trnsys-users@lists.onebuilding.org; caosunliang@msn.com<br>Subject: Re: [TRNSYS-users] Question about H2 electrolyzer Type 160<br><br>
Sunliang,<br>
In the Type160 code, the equation for the heat generated by the
electrolyzer is qGen = nCells*Iely*(Vcell-Vtn)<br>
<br>
where Iely is the electrolyzer current, Vcell is the cell voltage
and Vtn is the thermoneutral cell voltage. The Faraday efficiency is
computed from:<br>
<br>
eta_f = idensity**2/(a1+idensity**2)*a2<br>
<br>
where idensity is the current density of the cells (Iely/Acell)<br>
<br>
I think that both the Faraday efficiency and the heat generated are
a result of the computation of the cell voltage and the stack
current. Therefore I think that the heat generation is correctly
computed and that the confusion may be in the definition of the
energy efficiency and the total energy efficiency.<br>
Kind regards,<br>
David<br>
<br>
<br>
<br>
<div class="ecxmoz-cite-prefix">On 11/20/2014 07:36, SUNLIANG CAO
wrote:<br>
</div>
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<div dir="ltr">Dear all, <br>
<br>
I have a question about the H2 electrolyzer model Type160. <span lang="EN-US">Shortly: Will the Faraday loss of the
electrolyzer be converted into heat in the electrolyzer?</span>
<p class="ecxMsoNormal"><span lang="EN-US"> </span></p>
<p class="ecxMsoNormal"><span lang="EN-US">In the electrolyzer
model (Type 160 written by Ulleberg) [1], there are three
efficiencies: eta_e, eta_F, and eta_tot:</span></p>
<p class="ecxMsoNormal"><span lang="EN-US">“eta_e” is the energy
efficiency of
electrolyzer without considering any Faraday loss, i.e. the
maximum theoretical
proportion of the electricity which can be covered to the
hydrogen energy
content.</span></p>
<p class="ecxMsoNormal"><span lang="EN-US">“eta_F” is the Faraday
efficiency: it is
the ratio of the real final produced H2 energy content to
the theoretical maximum
produced H2 energy content.</span></p>
<p class="ecxMsoNormal"><span lang="EN-US">“eta_tot” is the total
efficiency of the
electrolyzer: it is equal to “eta_e*eta_F”, and thus is the
ratio of the final
produced H2 energy content to the electricity consumed in
the electrolyzer.</span></p>
<p class="ecxMsoNormal"><span lang="EN-US"> </span></p>
<p class="ecxMsoNormal"><span lang="EN-US">In Ullerberg’s model [1]
(TRNSYS Type 160),
the heating generated by the electrolyzer is calculated by
the P_ely*(1-eta_e),
which hasn’t taken the Faraday loss into account. However,
according to the
energy balance, the Faraday loss must be somewhere, which
mostly in the form of
heat, so I doubt why the Faraday loss hasn’t been taken into
account in the
thermal part of the electrolyzer model.<br>
</span></p>
<p class="ecxMsoNormal"><span lang="EN-US"> </span></p>
<p class="ecxMsoNormal"><span lang="EN-US"> </span></p>
<p class="ecxMsoNormal"><span lang="EN-US"> </span></p>
<p class="ecxMsoNormal"><span lang="EN-US">Reference [1]: Øystein
Ulleberg, Modeling
of advanced alkaline electrolyzers: a system simulation
approach, International
Journal of Hydrogen Energy, Volume 28, Issue 1, January
2003, Pages 21-33. <a href="http://www.sciencedirect.com/science/article/pii/S0360319902000332" target="_blank">http://www.sciencedirect.com/science/article/pii/S0360319902000332#</a></span></p>
<p class="ecxMsoNormal"><span lang="EN-US"> </span></p>
<p class="ecxMsoNormal"><span lang="EN-US"> </span></p>
<p class="ecxMsoNormal"><span lang="EN-US">Thank you very much.</span></p>
<p class="ecxMsoNormal"><span lang="EN-US"> </span></p>
<p class="ecxMsoNormal"><span lang="EN-US"> </span></p>
<p class="ecxMsoNormal"><span lang="EN-US">Kind Regards,</span></p>
<p class="ecxMsoNormal"><span lang="EN-US">Sunliang Cao<br>
</span></p>
<p class="ecxMsoNormal"><span lang="EN-US"> </span></p>
<br>
</div>
<br>
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***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
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