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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">This response will target specifically the thermal tracking option for cogeneration systems, with regards to gas turbine engines/generators (GTG).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">FYI, based on data I have analyzed previously from a major GTG manufacturer (on the Southern West Coast), I think the issue is that GTG exhaust heat output
is not linear with electrical load. In other words, you can drop the electrical load on the GTG by 50% and still get ~ 77% of the thermal output that you get at 100% load. Thus, I’m not surprised at the results you are getting using the thermal tracking
option. The eQuest curves appear to be taking into account the non-linear relationship between GTG electrical and thermal output. However, I would step back and ask the question, does thermal tracking really work? In other words, if you have to significantly
drop your electrical output in order to match the thermal load, that may work inside eQuest due to the use of a theoretical curve. However, it may not work in the real world due to operational constraints. This varies by equipment, but what I mean by this
is the following. For example, manufacturers of the simple Brayton cycle gas turbine engines appear (to me) to not want the GTGs operated at less than 50% load for stability reasons, and I know they will not rate them at load conditions < 50%. It’s likely
that you couldn’t operate the GTG at these conditions because the GTG PLC controller would be programmed to override to protect the equipment. Thus, the controller may not allow the electrical load to go less than 50%, in which case you would be forced to
find a way to dump the excess heat, which is typically done via a diverter stack, which diverts exhaust gas around the Heat Recovery Steam Generator (HRSG).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">To summarize, my take is what eQuest is doing is correct. Your potential solutions could be the following:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><span style="mso-list:Ignore">1)<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Generate too much electric power and thermal energy; sell the excess electricity to the grid if you can, and waste the excess thermal energy through
a diverter stack that operates in conjunction with the heat recovery steam generator/heat recovery hot water generator.<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><span style="mso-list:Ignore">2)<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Downsize the GTG equipment to better match electrical and thermal capacity to loads, minimizing non-utilized heat output, and minimizing electricity
sold to the grid.<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><span style="mso-list:Ignore">3)<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Combination of the above.<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><span style="mso-list:Ignore">4)<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Use a different type of cogeneration equipment, such as a reciprocating engine or a micro steam turbine generator. Do you really have a gas turbine
generator, or do you have a reciprocating engine? A recip engine may have different thermal output versus electrical output characteristics that might work better in your favor. I’m not as familiar with the recips so somebody more knowledgeable in this area
would need to respond. <o:p></o:p></span></p>
<p class="MsoListParagraph"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">In practice, the sizing of cogeneration systems is quite tricky. I don’t think there is a perfect solution, but you strive for the best solution you can get
based on the loads you have and the available cogeneration equipment in the market, including consideration of their specific operation constraints. In general, the goal is to size the cogeneration equipment to match thermal loads, but it’s not possible to
get a perfect match, and therefore some heat will be wasted.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Your specific problem may be that you are trying to model a campus cogeneration system serving just the building for your project, in which case the loads versus
cogeneration capacity would be a complete mismatch inside eQuest. In that case, I think you would be better off ditching eQuest to model the cogeneration system and just roll your own spreadsheet based on data supplied from whoever is operating the cogeneration
plant, which is allowed per the USGBC DESv2.0 guidelines. For example, if you had monthly/annual “monitored” data on total electrical output, total gas input, total hot water output, etc. you could create a spreadsheet that satisfies the DESv2.0 guidelines.
My opinion is that this approach would be easier than wrestling with eQuest on cogeneration. The simplest solution, but least accurate but perhaps more cost effective for you, is to use the default CHP efficiencies on page 27 of DESv2.0 (i.e. Appendix D).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hope this helps.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Thanks!
</span><span style="font-size:11.0pt;font-family:Wingdings;color:#1F497D">J</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p></o:p></span></p>
<p class="MsoListParagraph"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<div>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:8.0pt;font-family:"Calibri","sans-serif";color:#339966"><o:p> </o:p></span></b></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#339966">JAH<o:p></o:p></span></b></p>
<p class="MsoNormal"><b><span style="font-size:8.0pt;font-family:"Calibri","sans-serif";color:#339966"><o:p> </o:p></span></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#339966">James A. Hess, PE, CEM, BEMP</span></i></b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><br>
Energy Engineer<br>
TME, Inc.<br>
Little Rock, AR<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Mobile: (501) 351-4667<o:p></o:p></span></p>
</div>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> equest-users-bounces@lists.onebuilding.org [mailto:equest-users-bounces@lists.onebuilding.org]
<b>On Behalf Of </b>Bishop, Bill<br>
<b>Sent:</b> Monday, June 17, 2013 8:08 AM<br>
<b>To:</b> DongEun Kim; equest-users@lists.onebuilding.org<br>
<b>Subject:</b> Re: [Equest-users] co-generation(gas-turbine generator) question !<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Kim,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The gas turbine generator is controlled by the settings in the electric meter to which it is assigned. The generator will match the required electricity consumption
(if it has the capacity) if you set the COGEN-TRACK-MODE to “Track Electric Load”. Setting the track mode to “Track Thermal Load” will control the generator to meet the hot water demand of the loop to which it is attached, and you only get electricity when
the generator is running to meet the HW load. If your heating demand is higher than your electricity demand, the generator will produce more electricity than can be used by the UTILITY meter and the surplus power is lost unless you also attach the generator
to an ELECTRIC-SALE meter. Setting the track mode to “Track Electric Load” should increase the fuel-to-electricity efficiency but then you will be wasting some of the recoverable exhaust heat.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><img width="479" height="360" id="Picture_x0020_1" src="cid:image001.jpg@01CE6B39.E30979C0"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Bill<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Franklin Gothic Medium","sans-serif";color:black">William Bishop, PE, BEMP, BEAP, LEED AP
</span></b><b><span style="font-size:10.0pt;font-family:"Franklin Gothic Medium","sans-serif";color:#006600">|</span></b><b><span style="font-size:10.0pt;font-family:"Franklin Gothic Medium","sans-serif";color:black"> Pathfinder Engineers & Architects LLP<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Arial","sans-serif";color:black">Senior Energy Engineer<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:5.0pt;font-family:"Arial","sans-serif";color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Arial","sans-serif";color:#1F497D">134 South Fitzhugh Street</span><span style="font-size:9.0pt;color:#1F497D">
</span><span style="font-size:9.0pt;font-family:"Arial","sans-serif";color:#1F497D">Rochester, NY 14608<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Arial","sans-serif";color:#1F497D">T: (585) 325-6004
</span><span style="font-size:9.0pt;font-family:"Arial","sans-serif";color:black">Ext. 114</span><span style="color:#1F497D">
</span><span style="font-size:9.0pt;font-family:"Arial","sans-serif";color:#1F497D">F: (585) 325-6005</span><span style="font-size:9.0pt;font-family:"Arial","sans-serif";color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><a href="mailto:wbishop@pathfinder-ea.com"><span style="font-size:9.0pt;font-family:"Arial","sans-serif"">bbishop@pathfinder-ea.com</span></a></span><span style="font-size:9.0pt;font-family:"Arial","sans-serif";color:black">
</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><a href="http://www.pathfinder-ea.com/"><span style="font-size:9.0pt;font-family:"Arial","sans-serif"">www.pathfinder-ea.com</span></a></span><span style="font-size:9.0pt;font-family:"Arial","sans-serif";color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Webdings;color:green">P</span><span style="font-size:14.0pt;color:green">
</span><span style="font-size:7.5pt;color:green">Sustainability – the forest AND the trees.</span><span style="font-size:18.0pt;font-family:Webdings;color:green">
</span><span style="font-size:14.0pt;font-family:Webdings;color:green">P</span><span style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:green"> </span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">
<a href="mailto:equest-users-bounces@lists.onebuilding.org">equest-users-bounces@lists.onebuilding.org</a> [<a href="mailto:equest-users-bounces@lists.onebuilding.org">mailto:equest-users-bounces@lists.onebuilding.org</a>]
<b>On Behalf Of </b>DongEun Kim<br>
<b>Sent:</b> Monday, June 17, 2013 5:19 AM<br>
<b>To:</b> <a href="mailto:equest-users@lists.onebuilding.org">equest-users@lists.onebuilding.org</a><br>
<b>Subject:</b> [Equest-users] co-generation(gas-turbine generator) question !<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hi All!<o:p></o:p></p>
</div>
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<p class="MsoNormal"> <br>
I have an urgent question for you!<br>
<br>
I am trying to model a gas-turbine generator (CHP) plant per the DES guideline Opt2.<br>
The CHP generates electricity using "track thermal load" and provides recovered hot water directly to a hot water loop.<br>
<br>
The problem is that the total electricity generated by the CHP plant is much less than it is supposed to be.<br>
(I put "HIR=2.5" for the gas-turbine generator as the electricity generation efficiency is 40%. However, the output shows that the total electricity generated is only 4% of the total fuel input)<br>
<br>
Does anyone have some thoughts on this?<br>
<br>
Any comment will be greatly appreciated!<br>
<br>
Thank you!!<br>
<br>
Kim<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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