Hallo everyone,
I have a question about process energy.
My project is a mixed use for CS, contains office, laboratory, lobby, storage and corridor. The owner does not now the process energy in this building. The receptacle power densities are according to ASHRAE 90.1 User's Manual Table G-B, which were used in both baseline and proposed simulations. But the sum of receptacle power is under the process load, which is base on the process energy power and electricity rate.
I have just made the receptacle power in energy simulation in Baseline and Proposed Case, not the sum of process load. But in table EAp2-4 I put the calculated value, which through the 25 % Baseline cost, because I cannot prove the process energy.
Could you tell me, I am right in this situation or not?
Thank you in advance!
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Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
June 13, 2012 - 10:11 am
Not sure I completely understand but I'll try. Using the power densities in the User's Manual is fine. If your process energy cost is over 25% you don't have to do anything. If less than 25% just explain your input assumptions.
Yu Wang
Mechanical EngineerSCHOLZE Consulting GmbH
13 thumbs up
June 14, 2012 - 4:44 am
Thanks Marcus. But my question is not in this situation. I try to explain more clearly.
The owner does not now the process energy, therefore I have made the receptacle power in energy simulation in Baseline and Proposed Case according to ASHRAE 90.1 User's Manual according to ASHRAE 90.1 User's Manual (assumed 10 kWh). Then I simulate and I have the energy cost for Baseline Case (assumed 100 $, with electricity rate 1$/kWh). I cannot prove the process energy, therefore I use 25 $ as process energy cost. But if I calculate the process energy use with 25 $ and electricity rate 1$/kWh, then process energy is 25 kWh. It is more than 10 kWh, which is according to ASHRAE 90.1 User's Manual.
Please help me to find a way how to explain the difference between the 10 kWh (ASHRAE 90.1 User's Manual) from and the 25 kWh (25 % * Baseline costs).
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
June 14, 2012 - 6:01 pm
Sorry but I am not sure I understand.
The receptacle power from the User's Manual is entered in the model as Watts/square foot and then a schedule is applied to give you kWh as the modeling output. The electric rate is then applied ($/kWh) to get cost. I am not sure what you mean by "prove the process energy". Again the 25% is not a requirement. If less than 25% explain what you have modeled (User's Manual values) and how you have modeled it.
Yu Wang
Mechanical EngineerSCHOLZE Consulting GmbH
13 thumbs up
June 15, 2012 - 4:04 am
Yes. The receptacle power (kW) has been calculated with area (ft²) and receptacle power density (W/ft²), which is based on building type. The receptacle load was always with full load output during occupancy time in simulation model. The receptacle energy use (kWh) is output from simulation. I can calculate process energy cost ($) with receptacle energy (kWh) and electric rate ($/kWh), but it is less than 25 % baseline cost.
Can I use this calculation to explain, why the process cost is below 25% of the Baseline energy cost?
Or should I use 25% of the Baseline energy cost as process energy cost, because I have no information about process energy from owner.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
June 15, 2012 - 9:18 am
Yes just explain why you are less than 25%.
Do not use the 25% as process energy cost.