EQuest Photvoltaic Module

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Has anyone successfully inserted a photovoltaic array into an eQuest
energy model? I found an example in the Dictionary, created a
photovoltaic module and an inverter and attached it to the EM1 utility
meter. However, the model's total energy consumption did not change with
this model addition. Since the model uses a Hawaii weather file, I am
thinking that there should be some reduction in energy consumption. I
have attached the inputs I used and the warning message I got from the
output file. Can anyone figure out what I am doing wrong? Thanks.

Kathryn Kerns

Kathryn Kerns's picture
Joined: 2011-09-30
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I think it depends on what reports you are looking at. I think eQUEST
reports the PV calculations after the plant calculations, so it will
show up in all your utility level reports (BEPS, BEPU, ES-D etc), but
not in your plant level reports (PS-F etc). So for instance when you
look at the eQUEST simulation results view, your parametric run reports
will show it in only a few limited places - the annual & monthly utility
bills, as well as the source energy in the building summary of the
parametric reports.

Hope this helps.

Vikram Sami, LEED AP

Vikram Sami's picture
Joined: 2011-09-30
Reputation: 0

Kathryn et al,

I looked into this a little more and here's what I understand:

The PS-E meter reports the end use consumption on the customer side of
the meter.

The BEPS Report reports end usage on the utility side of the meter. If
you have a generator (like a PV system) it prorates the electric
generation across all end uses, so this isn't an accurate representation
of the building energy usage. It's my understanding that this is why the
energy numbers in the results view come from the PS-E reports and not
the BEPU reports.

So if you want to get the electricity generated by your PV system, you
should look up the PS-H report for your array (not for the module).
Make sure you look under AC Output (not DC output) to get the
post-inverter output.

Your BEPU total kWh should equal to your PS-E total - your PS-H AC total
for the PV Array.

Vikram Sami, LEED AP

Vikram Sami's picture
Joined: 2011-09-30
Reputation: 0


I?ve done a small PV array that was more for classroom demonstration than actual electric generation; it had 10 small 170 W panels and one oversized 10 kW inverter for future expansion. The simulation showed that it produced a peak of 700 W and 81 kWh/yr (in Dallas), this is about what we expected since the panels were barely enough to reach the inverter?s minimum tracking volts.

Your inputs look reasonable for the most part, but here are a few things I would try:

? Make sure your array configuration is accurate. The ?Inverter Module PV Array? screen shot shows default values for the number of panels wired in series and parallel. This has a big impact on how the system operates.

? Double check the inverters? minimum input and tracking volts. You have both set to 200 V, but there is a minimum operating voltage and a minimum ?efficient? operating voltage. The performance curves won?t fit if the inverters shut down any time the minimum tracking voltage isn?t met.

? Double check your Short Circuit Temperature Coefficient. 0.05300 seems large (for example, the BP SX170B is 0.00065)

? Double check your Short Circuit current. 0.24 amps seems very small and implies the panels have a lot of resistance. I would expect it to be a little higher than the max power current.

? Under EM1, try setting the cogeneration track mode to simply ?track electric load?.

You can also check the PS-C report to see the array?s sum and peak outputs (should be negative values) for the year. It will also show you the hours for each part load range.

Also, I?m not quite sure if you?re including the utility rate screen shots because you?re trying to sell surplus electricity back to the grid. If so, you?ll need to set up a separate electric meter of type ?electric sale?. That?s a procedure that is a little long to explain, but it?s well covered in the documentation. Here are a few comments about what I saw in the screen shots:

? ?Custom Elec Rate? is not serving any meters. You?ll want to choose a meter under ?Electric Meters Served? for the rate to be applied.

? Your blocks all have one rate with a size of ?1?, so I assume you just want to apply a uniform rate to all kWh. In this case, you don?t have to set up blocks. You can put in the rate under ?Uniform Energy Charge? in the rate?s Energy/Demand tab. You can leave the Energy Charge Schedule undefined if it?s the same all year. In the same tab, you can fill out the demand charges by month.



Dakota Kelley's picture
Joined: 2011-09-30
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