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HVAC Sizing and Load Calculations with EnergyPlus Cloud

Krishnan Gowri
April 9, 2015

As many of you know, the BPA team has been focused on improving EnergyPlus runtime and has achieved up to 20X faster simulation with the cloud.  In order to reach this goal, several input parameters were optimized and output reports were limited to annual building utility summary reports (ABUPS).  Based on user feedback and the immediate needs of designers, the BPA team has now added space heat gain summary (Figure 1) and zone load component summary (Figure 2) reports.  These reports provide the peak heating and cooling loads in all zones, and include a breakdown of the load contributions from various components such as people, lighting, equipment, envelope, and infiltration.  Designers can use these reports to identify the factors contributing to the peak design loads and for HVAC system selection and sizing.  If you have not tried EnergyPlus Cloud yet, join the project, give it a try and let us know how this report helps or not with your work flow.


Figure 1: Peak Space Gain Summary Report



Figure 2: Zone Component Load Summary Report

Krishnan Gowri

Krishnan Gowri is a product owner and subject matter expert with more than twenty five years of experience in building science, energy simulation and software development. Prior to joining Autodesk, Krishnan was a Senior Research Engineer at the Pacific Northwest National Laboratory where he led the Building Energy Codes software development team and Targeted E4 (Energy Efficiency Expert Evaluation) team. Krishnan graduated with his Masters and Doctoral degrees in Building Engineering from the Centre for Building Studies of Concordia University, Montreal, Que. In his spare time, Krishnan enjoys playing tennis, stringing racquets, umpiring matches, gardening and photography.


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  1. Avatarbenroberts



    Hi Krishnan,

    This shows useful results for cooling loads, but what about heating loads? Does Energy plus give you a steady state heating load, or is it quasi-dynamic (e.g. Degree Day)?


    1. Krishnan GowriKrishnan Gowri (Post author)



      Heating loads are also calculated based on design day hourly simulations to determine the peak heating load. It is using the heat balance method to calculate conductive, radiative and internal loads/infiltration into account, typical for hourly load calculation using EnergyPlus. The hourly simulations are done using sub-hourly timestep calculations of 15 minutes duration and do not use any steady state assumptions or degree-day/bin methods. The load calculation summary contains component loads breakdown to know the contributions from each envelope component and other sources making up the total heating load.