EnergyPlus

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  1. CHN_Hong.Kong.SAR.450070_CityUHK cannot be downloaded

    CHN_Hong.Kong.SAR.450070_CityUHK weather file cannot be downloaded

    1 vote
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    0 comments  ·  Weather  ·  Admin →
  2. EPW Weather Data for Tegucigalpa, Honduras

    Hi. I would like that Energyplus could ADD the epw. weather file for the city of Tegucigalpa, capital city of Honduras. Other cities are provided, but the capital city not.

    1 vote
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    0 comments  ·  Weather  ·  Admin →
  3. ASTM C1340 convection algorithm for attic spaces

    The calculation of convection coefficients on the surfaces for spaces representing attics in EnergyPlus has been shown to have inaccuracies when compared to empirical data and building models that specialize in attics. The ASTM C1340 standard has a set of correlations for these convection coefficients that has been empirically validated. An EMS approach to implementing these convection coefficients is available, but it would be much more usable to have it incorporated as a new object in EnergyPlus.

    3 votes
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    0 comments  ·  Envelope  ·  Admin →
  4. Improve fan support in Airflow Network

    Improve fan support in AirflowNetwork, including support for the new system fan model, support zone-induced air flow by a constant volume fan (described in Zone_2007_06.doc), and support for dedicated supply fans.

    2 votes
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    1 comment  ·  Air Flow  ·  Admin →
  5. Airflow Network Duct Autosizing

    Autosize the ducts in AirflowNetwork based on Manual D. Automatically sizing ducts for desired flow rates will simplify specification of more complex models. NREL residential has a Manual J OpenStudio measure, so this could be done in OpenStudio, but the current feeling is that it’d be better in EnergyPlus

    2 votes
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    0 comments  ·  Air Flow  ·  Admin →
  6. Allow multiple air loops in the Airflow Network model

    The existing AirflowNetwork model only allows one air primary loop to calculate the energy losses for an air distribution system. This restriction makes the model only able to simulate energy performance with air distribution system losses in residential homes and small commercial buildings. Large commercial buildings are not covered by the model, because multiple air distribution systems, equivalent to multiple air primary loops in EnergyPlus, are expected. In order to make the AirflowNetwork model applicable to large building simulations, multiple air primary loops must be allowed.

    3 votes
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    0 comments  ·  Air Flow  ·  Admin →
  7. Improving Modeling of Refrigerated Open Vertical Display Cases

    Problem Statement: Supermarkets have one the highest EUIs (~50-60 kWh/sf-yr) in commercial sector. Open vertical display cases, especially, in medium temperature suction group, account for the largest refrigeration load in supermarkets. Studies have shown that 80% of the cooling load in these cases is attributed to the infiltration of warm/moist air from the sales floor across the air curtain into the case. Accurate modeling of the air curtain will improve the reliability of refrigeration power and energy use predictions.

    Rationale: Currently, infiltration is a user input in E+. Errors associate with this critical input can have significant adverse impact on…

    1 vote
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  8. Improved Documentation for Thermal Energy Storage Systems

    Create an application guide around thermal energy storage system modeling in EnergyPlus. Focus on how these systems should be built up topologically, controlled, where EMS hooks are most beneficial, how sizing interactions result in the final system size, etc. These systems are quite often used as a comparison to a baseline so keeping the context of creating a baseline and comparing the proposed TES system to that baseline would be important.

    1 vote
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  9. Alternate simulation initialization (warmup) options

    EnergyPlus “runs” the first day of the environment (starting with a set of hardcoded initial conditions: temperatures are initialized to 23C and zone humidity ratios are initialized to the outdoor humidity ratio) until the loads/temperature convergence tolerance values are satisfied (next two fields) or until it reaches “maximum number of warmup days”

    Other programs offer different initialization methods, such as a user-specified number of days to simulate prior to the simulation start date. Recent comparisons related to ASHRAE Std 140 development have shown that the impact on results in the first simulation month can be significant.

    1 vote
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    0 comments  ·  Other  ·  Admin →
  10. New single-duct constant volume air terminal without reheat

    The existing AirTerminal:SingleDuct:Uncontrolled is different from all other terminal units. It only has a single node (not an inlet and outlet) and it sits directly on the zone equipment list instead or being referenced by a ZoneHVAC:AirDistributionUnit object. This causes fits for interfaces, and it prevents this terminal unit from using the simple duct-leakage features in ZoneHVAC:AirDistributionUnit.

    Propose adding a new terminal unit type AirTerminal:SingleDuct:ConstantVolume:NoReheat that has an inlet and outlet node and sits under an air distribution unit. Then deprecate the old AirTerminal:SingleDuct:Uncontrolled object.

    Reference issue #4988
    https://github.com/NREL/EnergyPlus/issues/4988

    2 votes
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  11. 2 speed Operation with Air Economizer in UnitarySystem

    Current economizer operation in unitary system with multispeed fan does not impact fan speed. Economizer only operation is limited to low speed operation and economizer plus compressor operation is limited to low speed unless both compressors operate. Current energy codes require unitary equipment over 5 tons to have economizers with two stages of economizer only operation, first at low fan speed and then at high fan speed, and then to integrated operation. Three of three manufacturers checked run the fan at high speed when economizer and stage one compression are operating.

    For more details see issue [#6109](https://github.com/NREL/EnergyPlus/issues/6109)

    1 vote
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    0 comments  ·  Control  ·  Admin →
  12. Expand Autosizing for CHP

    Some input fields are not autosizable but it would be helpful if they were. For example the combined heat and power models have heat recovery plant connections but the plant flow rates are not autosizable making it difficult to use them in many models. Suggest to add autosizing to heat recovery in Generator:InternalCombustionEngine, Generator:CombustionTurbine, and Generator:MicroTurbine objects.

    2 votes
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    0 comments  ·  Input  ·  Admin →
  13. Improve the AirLoop:UnitarySystem object to support VAV fan control

    Currently, the AirLoop:UnitarySystem object does not support representation of variable-speed RTUs, even with the inclusion of EMS control logic. From emailing with the E+ team, my understanding is that this is an effect of the unitary system "not having an EMS actuator for flow rate, since the DX coils need to be modeled at full flow, and the unitary system needs to know the average flow rate over the time step (a function of PLR) so that it can model the DX coil with the correct flow." The only viable workaround for this is to pull the Fan:VariableVolume object outside…

    1 vote
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  14. Add/update Performance Data for key systems such as chillers, boilers, CHP, etc.

    The E+ performance curve datasets have not been updated for a long time and the available performance data seems to have mostly gotten in there due to the manufacturer's interest (guess) to provide that data set. In short, these performance data sets are in most cases generic and make the use of E+ for complicated systems such as combined heat and power, accurate part-load performance of chillers/boilers, multi speed coils, etc. inconsistent if not unreliable depending on the modeler's expertise.

    Many modelers have sheets or other simple tools to transform some datasheets to performance curves - it might be worth…

    2 votes
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    0 comments  ·  Performance  ·  Admin →
  15. Account for fan heat gain when sizing zone equipment cooling coils

    Fan heat gain to air increases the load experienced by cooling coils. Currently EnergyPlus accounts for this when sizing central cooling coils but it is not taken into account when sizing cooling coils in zone HVAC equipment. Suggest to improve Zone HVAC unit cooling coil sizing to account for fan heat in forced air units.

    2 votes
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  16. Central Plant Water to Water Heatpump with EIR Formulation

    The existing models for central plant water to water heatpump, HeatPump:WaterToWater:* are not formulated to be able to use the types of performance curves that are typically used in the industry. It is not possible to properly represent equipment performance characteristics with the current equation fit models and the parameter estimation model is not robust enough in practice.

    Suggest to add new models for water-to-water heatpump that are formulated using an EIR-type approach for unloading curves such as are used elsewhere in the chiller and chiller-heater models. The existing two models might be deprecated.

    2 votes
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  17. Interzone Air Wall

    Two separate thermal zones often have no actual wall separating them, for example open plan offices, or zones open to atria. It is not clear how to best, or if it is possible to, represent these so-called air walls in EnergyPlus. There is a need for a robust and straightforward way to model air walls without messy workarounds. Current workarounds all have different problems that are difficult for users to understand and adjust for. A new air wall feature that passes solar, daylight, interzone air, and connects interior thermal radiation would be a useful addition.

    2 votes
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    0 comments  ·  Geometry  ·  Admin →
  18. Allow User to Set Primary Airflow Rate Through AirTerminal:SingleDuct:Mixer Object

    The AirTerminal:SingleDuct:Mixer object functions well with respect to its goal to enable the connection of central air systems to the inlet side of Zone:HVAC equipment. One feature that would be helpful, however, would be the ability to set the primary air flow rate through the terminal. Currently, E+ just sets this value equal to the central air flow rate / # branches, which makes it impossible to apportion OA appropriately between non-identical zones. Based on examination of eio files, I do not believe that E+ even attempts to size the terminal unit, so it is also not currently possible to…

    1 vote
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  19. Size Zone Equipment properly (different coil types are wildly different)

    EnergyPlus does not size zone equipment coils correctly, especially non-chilled water coils like:

    - Heat pump coils
    - VRF coils
    - DX coils

    We have stopped reporting coil size outputs from E+ to users and instead report the load that the coil has removed from the space as the sizing because it is the only sensible and consistent output. Without this we saw coil sizes vary wildly by over 50% between systems for the same buildings.

    To reproduce, do this:

    1) Build a reasonably detailed model with a decent number of zones.
    2) Run the model with the following systems: …

    2 votes
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  20. Decide what the peak load actually is

    As a user, when I download the E+ sizing and loads report, I get a very confusing set of information for the zone as to what the peak loads are.

    On occasions there could be up to 3 peak cooling load numbers I could use for that zone:

    - Grand Total Peak Load Component
    - Peak Design Sensible Load
    - Estimated instant + delayed peak sensible load

    As a vendor that needs to provide a single number to the user, this is hopeless. Which value do we use? Which values were used for ASHRAE 140? There is no guidance.

    We…

    2 votes
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