EnergyPlus

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  1. Link Kiva ground heat transfer model to low temperature radiant model

    The recently added Kiva ground heat transfer model can be used to perform detailed ground heat transfer from basements and slab-on-grade floors. Currently there is no method in EnergyPlus for estimating the heat loss to ground from slab-on-grade radiant floors. In this proposed task the ground heat transfer model Kiva would be linked to the low temperature zonal radiant floor model. Research has shown that heat loss from slab-on-grade radiant floors can be significant and should be accounted for when modelling these types of systems.

    6 votes
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  2. Account for DOAS air when sizing zone units

    I cannot believe this is not a feature request but I could not find it so here goes.

    If you have a DOAS system in E+ (eg Fan Coils of any kind, radiators, etc) combined with a ventilation system, E+ does not currently take into account heating and/or cooling effects of the DOAS air when sizing the zone units (coils and fans)

    This is a gross error. It is very common in DOAS systems for the air to be conditioned for dehumidification, meaning that air could be supplied from the DOAS system as low as say 13C / 55F and…

    2 votes
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  3. 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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  4. 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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  5. Implement optimal start for all zone equipment

    Currently optimal Start is available only for air loop through AvailabilityManager:OptimumStart.

    It seems useful to link this algorithm to the zone thermostat to offer this functionality for all system (water loop and unitary equipment).

    2 votes
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  6. Fan coil sizing

    Fan coil sizing: we expect same size with different sizing:plant dT, but observed different sizes

    3 votes
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  7. Thermostatic Control of Ventilated Slabs

    Problem: One potential “deficiency” in the current EnergyPlus model for ventilated slab systems is that it does not attempt to control a zone but rather controls how and when the slab will receive outside or conditioned air.

    Rationale: There are some systems in Asia that use what looks like an EnergyPlus ventilated slab as the primary conditioning system within a space. The only reason why these systems cannot be modeling in EnergyPlus using the ventilated slab system is a control issue.

    Solution: Add a method of control to the current ventilated slab model that allows it to control the zone…

    2 votes
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  8. Enhance CO2 Modeling to include OA rate from zone equipment

    Problem: Although some ZoneHVAC equipments are able to bring outdoor air to dilute zone CO2 levels, the outdoor air introduced by zone HVAC equipments are not used to control zone CO2 levels.

    Rational: The zone equipments can bring the outdoor air to dilute indoor CO2 levels. These OA rates should be included in the total system level outdoor airflow rate to reduce the amount of OA rate entered in the OA mixer to maintain the setpoint conditions.

    Solution: Allow CO2 control for ZoneHVAC equipment in conjunction with AirLoop together.

    https://github.com/NREL/EnergyPlusDevSupport/blob/master/DesignDocuments/EnhancementList/HVAC_Zone_2010_01.doc

    3 votes
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  9. Allow OA Controllers to be used with ZoneHVAC equipment

    Problem: Zone HVAC equipment allows specification of outdoor air flow rate and also allows an OA Mixer. However, the OA flow rate is full flow while the unit operates and does not allow economizer operation.

    Rational: Zone HVAC equipment should allow economizer operation.

    Solution: Allow specification of OA controller with zone equipment.

    Context: Similar controls as provided with air loop equipment.

    Pros and Cons of Solution:
    + allows greater flexibility in control for zone equipment
    - OA controllers have at times led to maximum iteration problems

    3 votes
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  10. Control Low Temperature Radiant Systems on Thermal Comfort Models

    Problem: While EnergyPlus allows a large range of controls for low temperature radiant systems, it does not currently allow the control of these systems based on the results of the thermal comfort models which exist within EnergyPlus.

    Rationale: Thermostatic controls in EnergyPlus allow air-based systems to be controlled using the results of thermal comfort models as part of recent additions to EnergyPlus. Radiant systems use their own controls and thus have not had this option. This does not then allow direct comparisons between radiant and forced air systems for equivalent comfort and the user must adjust the radiant system controls…

    4 votes
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  11. Add Supplemental Heating Coil option to VRF Terminal Unit

    Problem: There is currently no way to include a supplemental heater in VRF zone terminal units.

    Rationale: VRF systems may not have sufficient heating power during extremely cold conditions and require backup electric resistance heaters in the terminal units. Heat pump systems may experience simultaneous heating and cooling loads and when in cooling mode the zones that lost the vote for heating could still heat with supplementary heat. Other air system heat pump equipment in EnergyPlus have supplemental heaters.

    Solution: Include supplemental heating coil option in ZoneHVAC:TerminalUnit:VariableRefrigerantFlow object

    Suggestion from legacy enhancement list (HVAC_Zone_2014_01)

    4 votes
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  12. Allow Heat/Cool coils in StandAloneERV

    Problem: Zone level heat recovery systems do not allow used of heating and/or cooling coils to pre-condition outdoor air.

    Rational: Zone level conditioning equipment do not allow heat exchangers as part of the configuration.

    Solution: Allow heating and cooling coils to be used with the Zone HVAC equipment Stand Alone ERV.

    Context: Similar to Zone DOAS equipment.

    Pros and Cons of Solution:
    + allows pre-conditioning of outdoor air used with heat recovery.
    - is duplicative of ZoneHVAC:OutdoorAirUnit

    1 vote
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  13. Zone Electric Storage Heater as ZoneHVAC Equipment

    Problem: No mechanism for energy storage other than water.

    Rational: Energy storage comes in other forms than water and are available off-the shelf.

    Solution: Add a heat storage unit as ZoneHVAC equipment.

    Context: Similar to ice storage where brick or other medium is heated during off-peak hours and used for heating during on-peak hours.

    Pros and Cons of Solution:
    + allows alternate energy source coupled with TOU rates to be used for heating
    + allows alternate solution for energy storage
    - can be modeled with electric equipment object, however, scheduling of when electricity is consumed could be difficult or require…

    1 vote
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  14. Modeling Exterior Seating Areas with High Temperature Radiant Heaters

    Problem: Buildings in a variety of climates use high temperature radiant heaters to provide comfort in outdoor areas during cooler seasons. While technical an exterior space, these areas are still part of the overall energy profile of the building and thus need to be modeled.

    Rationale: EnergyPlus does have a high temperature radiant heater model, but it does not have a way of using these for an outdoor area. Thus, these situations cannot be directly modeled by EnergyPlus.

    Solution: Add a model that looks at outdoor areas and how to incorporate the use of high temperature radiant heaters in these…

    1 vote
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  15. Implement SZVAV type controls for other zone level equipments

    Current E+ version handles SZVAV fan control implemented in fan coil units. Since its becoming a standard across the industry, it would be great if that functionality to be expanded to other zone level equipment's like VRF (when fan is ran in auto mode), PTHP, Unit Ventilator, PTAC and Unit Heaters.

    5 votes
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  16. Auto share zone sizing capacity for multiple equipments in a zone

    Hello,
    Currently, there no way to autosize zone load for multiple equipments in a zone. We need to hard sized each zone. For big spaces or conceptual design, it takes a lot of times. If we can make sizing number based on zone equipment quantity or one hard sized equipment tehn auto-multiple it, it should be a great feature

    1 vote
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  17. Set Type of Load to Size On at the Terminal Unit

    Currently in EnergyPlus you set the type of load to size on at the system itself rather than the terminal units, which adds rigidity to the sizing runs. Systems nowadays often utilize hybrid solutions where the air system is sized for ventilation at some zones and full load at other zones. My suggestion would be to set the sizing requirement at the terminal unit rather than the air system for greater flexibility. This would allow for sizing calculations of such hybrid systems to be performed without the need of post processing, which can be lengthy for large projects.

    1 vote
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  18. Fan:ZoneExhaust motor load

    Add options to assign the motor load to the exhaust airstream (current default), the space (if the zone exhaust fan is actually located in the zone), to the outdoors if the exhaust fan is located outdoors, or to another zone (if the exhaust fan is located in a mechanical room).

    1 vote
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  19. Allow evaporative coolers to cycle

    Problem: Many residential evaporative cooling technologies (e.g., swamp coolers) are controlled to cycle on and off to meet the load. As stated in the I/O reference, these units cannot cycle, meaning that their pumps run continuously even when the required airflow rate is close to zero.

    Solution: Give zone evaporative coolers the capability to cycle like unitary equipment.

    Context: See the second paragraph here: http://bigladdersoftware.com/epx/docs/8-3/input-output-reference/group-zone-forced-air-units.html#zonehvacevaporativecoolerunit

    1 vote
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