HVAC equipment (chillers, towers, water coils and DX coils) to cool data centers are operating at higher temperatures (e.g., supply air temperature and supply water temperature). EnergyPlus equipment models and performance curves are mostly designed/based on human comfort applications which usually have lower supply temperatures. There is a need to verify the accuracy of extending the existing HVAC equipment models and curves from human comfort applications to data center applications. This is a request from ASHRAE TC 9.9 and Standard 90.4.

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.

Problem: There are several coil object types that represent DX heating or cooling with different input fields, capabilities, and source code.

Rationale: Providing a single, generalized DX coil for both heating and cooling with all capabilities will enforce consistency.

Solution: Create a single DX cooling coil that covers:

- Coil:Cooling:DX:VariableRefrigerantFlow
- Coil:Cooling:DX:VariableRefrigerantFlow:FluidTemperatureControl
- Coil:Cooling:DX:SingleSpeed
- Coil:Cooling:DX:TwoSpeed
- Coil:Cooling:DX:TwoStageWithHumidityControlMode
- Coil:Cooling:DX:MultiSpeed
- Coil:Cooling:DX:VariableSpeed
- CoilPerformance:DX:Cooling
- Coil:Cooling:WaterToAirHeatPump:ParameterEstimation
- Coil:Cooling:WaterToAirHeatPump:EquationFit
- Coil:Cooling:WaterToAirHeatPump:VariableSpeedEquationFit

and the equivalent coils for a single DX heating coil.

Add a HVAC template for radiant zone terminal units. Currently (v8.7), if you want to implement radiant with DOAS, then you have to use a roundabout way of implementing it by first using the baseboard heat template and then replacing the objects. It would be nice to have the radiant terminal units as an option in the templates.

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.

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.

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.

EP-Launch Lite that is distributed on non-Windows installs of EnergyPlus is not functionally equivalent to EP-Launch on Windows. It does not support all the same utilities or options. EP-Launch has not had a significant GUI update in many years. EP-Launch would be rewritten to have a more modern GUI while supporting all the same utilities and options and would be made to be cross platform compatible.

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

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

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.

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.

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.

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.

This might belong in bugs. Forgive me if that's the case.

E+ does now supply DOA air to zone equipment BUT it is not done correctly because it divides the AHU air supply by the number of zones and just supplies that rate.

The air supplied to the zone should be based on the criteria set in E+, whether it's based on a constant rate set by the user or based on ventilation demand or whatever was used to size the total value. It should be apportioned by zone.

Otherwise the feature is effectively useless.