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RE: [EnergyPlus_Support] Re: Economics and Demand Cost Calculations
A formal methodology for splitting demand charges across end uses was
prepared as part of the commercial building tax credits. See section
3.1 of the report at:
http://www.nrel.gov/docs/fy07osti/40228.pdf
These calculations are not supported inside EnergyPlus; you would have
to do them with postprocessing.
Input objects like the following can be used to report out the
components of demand at the time they occur.
Report:Table:Monthly,
Components of Peak Electrical Demand, !- Name
3, !- DigitsAfterDecimal
Electricity:Facility, !- VariableOrMeterName01
Maximum, !- AggregationType01
InteriorLights:Electricity, !- VariableOrMeterName02
ValueWhenMaxMin, !- AggregationType02
InteriorEquipment:Electricity, !- VariableOrMeterName03
ValueWhenMaxMin, !- AggregationType03
Fans:Electricity, !- VariableOrMeterName04
ValueWhenMaxMin, !- AggregationType04
Heating:Electricity, !- VariableOrMeterName05
ValueWhenMaxMin, !- AggregationType05
Cooling:Electricity, !- VariableOrMeterName06
ValueWhenMaxMin; !- AggregationType06
________________________________
From: EnergyPlus_Support@xxxxxxxxxxxxxxx
[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of boulder1259
Sent: Friday, August 17, 2007 4:22 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Re: Economics and Demand Cost Calculations
What I am trying to do is figure out what portion of the utility bill is
due to lighting,
HVAC, process, etc. (a common question from clients). The billing is
simple: demand and
consumption charges. Since demand charges are by far the largest part of
the bill, I
wanted an easy way to split these charges amongst the various services.
If I understand
you correctly, this isn't possible with the current version of
EnergyPlus.
Most of what you said about submetered charges not adding up to the
facility metered
charges makes complete sense. My mistake was that I wasn't thinking
about the
submeters as being actual meters. Any time demand charges are involved,
I would expect
the sum of the submeters and facility meter to differ because the demand
peaks on the
various meters are not likely not be coincident. Only if they were would
I expect the two
to be the same.
Thanks,
Greg
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx
<mailto:EnergyPlus_Support%40yahoogroups.com> , "Michael J. Witte"
<mjwitte@...> wrote:
>
> I am not sure I understand what you are trying to do. The energy and
demand
> charges within a given tariff will only be based on the specific meter
or sub-
> meter that is assigned to that tariff. If you want to calculate demand
charges
> for the building as a whole but then separate energy charges by
end-use, you
> would need a tariff connected to the facility electricity meter that
calculates
> only demand charges, and then tariffs connected to submeters that only
> calcaulate energy charges.
>
> Ultimately, I have to question your assumption that the submetered
costs will
> add up to the same value as the facility meter costs. This will only
be true
> if the rates are a very simple single charge for energy and for
demand, say
> $0.10/kWh for energy and $15.00/kW for demand. If there are any sort
of
> declining blocks or ratchets or other complexities to the rate
structure, they
> will not total to the same value. The use of separate tariff objects
in
> EnergyPlus is intended to be used when the building truly has meters
which are
> separately billed, such as a separate meter for space-heating
electricity.
>
> Mike
>
>
> On 13 Aug 2007 at 18:31, boulder1259 wrote:
>
> > I'm trying to figure out a way to apportion various building service
costs but
> > am not having much luck.
> >
> > When I sent up a tariff for facility-wide electricity charges (the
charges
> > include demand charges), EnergyPlus seems to produce reasonable
values.
> > However, if I try to do the same for the various building services
and then sum
> > them, the sum of the charges does not match the value of when I look
at the
> > building as a whole.
> >
> > I'm seeing that the electricity consumption charges can be summed,
but that the
> > electricity demand charges cannot. Apparently, the demand charges
for the
> > individual services (e.g., lighting) are not calculated from the
facility's
> > demand charges but rather independently.
> >
> > Do you have suggestions of how to split the electric bill into its
various parts
> > (e.g., lighting, pumps, fans, etc.)?
> >
> > Thanks,
> > Greg
> >
> >
> >
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov <http://www.energyplus.gov>
> >
> > The group web site is:
> > http://groups.yahoo.com/group/EnergyPlus_Support/
<http://groups.yahoo.com/group/EnergyPlus_Support/>
> >
> > Attachments are not allowed -- please post any files to the
appropriate folder
> > in the Files area of the Support Web Site.
> >
> > EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under
the
> > Documentation link and press the "search" button.
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
>
[Non-text portions of this message have been removed]
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