EnergyPlus

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  1. Thermal bridging

    Problem: EnergyPlus provides no method to describe thermal bridges in envelope components.

    Solution 1: A very basic approximation would be to allow independent parallel path calculations for the same construction (e.g., wood stud and insulation cavity).

    Solution 2: Develop adjustments to the conduction calculations for linear and point thermal bridges, similar to Psi factors.

    36 votes
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    in discussion  ·  9 comments  ·  Envelope  ·  Admin →
  2. Reuse shading calculations between runs

    Shading calculations are processing intensive and can take a long time for large models with a lot of shading surfaces.

    Once all design decisions for the geometry and envelope properties of a building are made, the effect of shading on the building should be identical between simulations (valid assumption?).

    If EnergyPlus could reuse these calculations between runs, a lot of processing time could be saved. Of course, EnergyPlus would have to detect that geometry and envelope have changed to force a recalculation.

    29 votes
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  3. Restructure EnergyPlus source code to parallelize computation

    The EnergyPlus simulation speed will be improved by enabling parallel processing on a computer with multiple-processors or multiple-cores. Restructuring iteration loops in EnergyPlus also has potential to speed up the simulation runs. This will improve run time for all buildings, but especially large and complex building models.

    29 votes
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    8 comments  ·  Performance  ·  Admin →

    Thank you for your suggestion. Improvements to simulation runtime are a high priority for the team, and parallelization would definitely help. However, restructuring the source code is a large endeavor. We will continue to target improvements towards this goal, but it will be an incremental effort.

  4. Modeling DOAS to AHU

    This feature develops the modeling and simulation approach for a dedicated outdoor air system (DOAS) connected to multiple air handling units (AHUs). Many buildings have a separate DOAS system that feeds outdoor air directly to individual AHUs on each building floor. Currently EnergyPlus can only model a DOAS delivering outdoor air directly to zones or to the inlet or outlet of some zone equipment acting as terminal units. This feature will allow a single DOAS to supply air to the outdoor air inlet of multiple air systems.

    26 votes
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  5. Calculate interior solar distribution for concave (non-convex) zones

    Problem: Full interior solar distribution isn't handled correctly for concave zones.

    Solution: Re-engineer the solar distribution and shading algorithms following some of the examples from computer graphics calculations.

    25 votes
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    in discussion  ·  2 comments  ·  Geometry  ·  Admin →
  6. Report Whole Window U-factor, SHGC, and VT

    Problem: EnergyPlus only reports U-factor, SHGC, and VT for center-of-glass. It does not report those values for the whole window.

    Rationale: It is very important for modelers to confirm that the window systems (glass layers, gas layers, frames, dividers, shades, etc.) have been input correctly and reporting standard rating values from EnergyPlus’s models is very helpful to close the loop.

    Solution: Add content to the fenestration summary report for whole window U/SHGC/VT. Calculate the whole-window metrics using procedures defined by NFRC and consistent with LBNL Window program. Correct any problems with how frame and edge-of-glass regions are input and modeled…

    24 votes
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    2 comments  ·  Envelope  ·  Admin →
  7. Occupant behavior modeling

    Energy-related occupant behavior in buildings is a key influencing factor of building performance. Daily interactions between building systems and occupants drive total energy use. Currently, occupant behavior is represented in simplified and pre-defined deterministic schedules or fixed settings and rules in EnergyPlus, resulting in deterministic and homogeneous results ignoring the stochastic nature, dynamics, and diversity of occupant behavior. Implementing the state-of-art occupant research achievements, such as obXML schema and advanced stochastic models, can extend the EnergyPlus capability in occupant behavior modeling. This may lead to better understandings on the interactions between occupant and building operations which is crucial to reduce…

    22 votes
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    2 comments  ·  Control  ·  Admin →
  8. Standardize simulation outputs in XML or JSON format

    EnergyPlus simulation results are currently stored in several different files with various formats. Putting the simulation results, including the summary reports, into a standardized data format such as XML or JSON can highly benefit the interoperability of EnergyPlus.

    20 votes
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    in progress  ·  5 comments  ·  Output  ·  Admin →
  9. Replace IDF with a standardized data format (e.g., JSON, XML, etc.)

    Problem: IDF is non-standard, non-extensible, and positionally dependent.

    Solution: Moving to a key-value pair style input (instead of positional) means:

    * Better handling of defaulting fields (no explicit blanks).

    * Long lists can be infinitely extensible (the schema doesn't need to specify fields for items 1-N, like the IDD does).

    * Transitions between versions of objects is handled more simply.

    20 votes
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    in progress  ·  6 comments  ·  Input  ·  Admin →
  10. Make "thickness" a property of the construction, and not the material

    Problem: For each different thickness of a material, I need to repeat the intensive properties (conductivity, density, and specific heat) in a separate Material object.

    Solution: The construction should specify two inputs for each layer: (1) a Material object reference (intensive properties only) and (2) the layer thickness.

    18 votes
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    2 comments  ·  Input  ·  Admin →

    We’re always looking for ways to make EnergyPlus more usable. We don’t have immediate plans to work on this as the current paradigm offers the same capability, albeit in a somewhat redundant manner. Once we address some higher priority usability issues, we’ll come back to this suggestion. Thank you for your suggestion.

  11. Modeling District Cooling / Heating systems

    EnergyPlus can report a building’s thermal loads as district cooling and heating loads. District heating and cooling (DHC) system loads can be entered as plant loads to simulate central plant performance. However EnergyPlus does not count the pumping energy or heat loss in the piping of DHC systems. Additional controls of DHC coupled with CHP are also needed in EnergyPlus to track either cooling, heating, or electrical loads. Modeling DHC systems is a key component of modeling urban systems.

    18 votes
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  12. Implement option for external shading calculations

    As stated in the feedback post “Reuse shading calculations between runs”, shading calculations are time consuming for large models with a lot of shading surfaces. In addition, the polygon clipping based algorithms that are used to determine shaded fractions also tends to be unreliable for complex geometry and results in several severe warnings. This limits applicability in shading device design and urban applications or require somewhat awkward workarounds with shading surfaces and transparency schedules such as suggested in this helpserve post (http://energyplus.helpserve.com/Tickets/Ticket/View/9310).

    In computer graphics there are OpenGL based methods (such as: http://www.ibpsa.us/simbuild2012/Papers/SB12_TS09b_3_Jones.pdf) that could drastically speed up shading simulations…

    18 votes
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    in progress  ·  1 comment  ·  Geometry  ·  Admin →
  13. Warm Start from Saved State

    Problem: Some applications of EnergyPlus for building operations would benefit from being able to restart from a state saved during a previous run of the same building. Currently EnergyPlus initializes loads at 23C and system nodes at 5C and then conducts a number of warm up days for transient conditioning. The runtime burden of those warm up days can be significant for some applications.

    Rationale: Increased performance (speed) for model predictive control that uses EnergyPlus in the control loop.

    Solution: Users could direct the program to save state at some point during the simulation and halt. The program could be…

    17 votes
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    in discussion  ·  4 comments  ·  Other  ·  Admin →
  14. Support complex window geometry with more than four verices

    Problem: If there are more than four vertices for Fenestration:Detailed object, E+ crashes,thanks to the IDF editor documenting this limitation. BIM tools that automatically generate Fenestration objects from gbXML fail when the windows are hexagonal or adjacent windows are combined in one object with multiple vertices.

    Solution: At the mercy of E+ dev team

    17 votes
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    0 comments  ·  Envelope  ·  Admin →
  15. Update LEED Reporting

    The current LEED Summary report helps users working with the LEED forms but it has not been updated much since it was created in 2006. It could be enhanced to provide more information that is needed for LEED submittals. This would help both users of LEED as well as GBCI reviewers. Many more details are needed by USGBC including the information needed for the Energy Performance Calculator and Table 1.4 spreadsheets. In addition, some of the current outputs from the LEED summary report could be revised to be more consistent with the requirements of USGBC.

    16 votes
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    in design  ·  1 comment  ·  Output  ·  Admin →
  16. cooled beam with VAV

    I would like to model cooled beam connectd with VAV system. It seems that the object AirTerminal:SingleDuct:ConstantVolume:CooledBeam can be connected only with a constant velocity system (CAV).

    16 votes
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  17. Demand Response Modeling

    Demand response strategies reduce peak electrical demand of building facilities, improve electrical grid stability, and facilitate integration of renewable resources. Implementing DR models in EnergyPlus can estimate the impact of DR strategies on the building HVAC operations and indoor thermal comfort. It can also support the evaluation of the DR strategies on the energy efficiency improvement at district scale or urban scale, and thus enhance the applicability of EnergyPlus in the analysis of large scale energy systems and power grid. In addition, it can facilitate the development of DR strategies with new HVAC technologies, such as the inverter technology within…

    15 votes
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    0 comments  ·  Control  ·  Admin →
  18. Improved Error Message Handling and Documentation

    Error messages (warning, severe, and fatal) are a source of confusion for many users as well as creating problems for interface developers. To improve the error messages, several improvements can be made:

    - An error number could be shown with each unique error message.

    - A new section in the documentation could show the next steps to take to resolve each type of error message. It would be arranged by error number.

    - The format of the error messages could be made more uniform.

    - The text of some error messages could be improved to be clearer

    - Error messages…

    15 votes
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    0 comments  ·  Other  ·  Admin →
  19. Spend several development cycles squashing long-standing bugs and paying off any tech. debt

    Lots of great new features and capabilities have been made available with E+ over the years, but there are still many lingering bugs that seem to pop up unexpectedly. When these bugs pop up, there is a detrimental effect on project timelines and our ability to rely on E+ to do the heavy engineering lifting.

    A good example is plant pumping systems; seems like the same types of issues are being reported by a number of users over the last year.
    https://github.com/NREL/EnergyPlus/issues/5892

    Also there appear to be some issues with sizing that get reported a lot; HW coils sizing to…

    15 votes
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    6 comments  ·  Other  ·  Admin →

    Thank you for the suggestion! Planning for EnergyPlus development cycles is often a balance of prioritizing:

    - new features,
    - bug fixes (short term fixes),
    - structural improvements to the code base (long term fixes),
    - performance improvements (i.e., make EnergyPlus faster), and
    - other usability improvements

    The team will take your suggestion to focus more on the priorities beyond new features into consideration.

  20. Buoyancy driven air flow in atrium-like spaces

    Currently EnergyPlus Air Flow Network does not offer much in terms of stack driven air flow in a high space, such as an atrium.

    However, these type of spaces do exist in many buildings. Besides, architects, and arguably building energy analysts in general, are very much interested to test the potential of stack driven natural ventilation as a passive cooling strategy.

    14 votes
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    in discussion  ·  1 comment  ·  Air Flow  ·  Admin →
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