HLCP - FAQ

2008-06-14T02:30:00.000+05:30

What is EP and HLCP?

EnergyPlus (EP) is a simulation engine. Normally it is used in conjunction with a graphical user interface. HLCP (Hourly Load Calculation Programme) is a graphical user interface for designday and hourly load calculations for Indian cities.

What is WeDCo?

WeDCo means: Weather data and Design Conditions for India

How do I model Thermal zones?

This section provides a step by step outline that will help you streamline creating your building models for using HLCP.

Step 1: Plan Ahead

Some preliminary steps will facilitate the construction of your input file. The following checklist should be completed before you start to construct your input file.

Obtain location and design climate information for the city in which your building is located. If possible, use one of the weather files available for your weather period run.

Obtain sufficient building construction information to allow specification of overall building geometry and surface constructions (including exterior walls, interior walls, partitions, floors, ceilings, roofs, windows and doors).

Obtain sufficient building use information to allow specification of the lighting and other equipment and the number of people in each area of the building.

Step 2: "Zone" the Building

A building "surface" is the fundamental element in the building model. In the general sense, there are two types of "surfaces" in HLCP/EnergyPlus. These are:

Heat transfer surfaces and

Heat storage surfaces

The first rule of building modeling is, "Always define a surface as a heat storage surface unless it must be defined as a heat transfer surface". Any surface, which is expected to separate spaces of significantly different temperatures, must be defined as a heat transfer surface. Thus, exterior surfaces, such as outside walls, roofs and floors, are heat transfer surfaces. Interior surfaces (partitions) are heat storage surfaces if they separate spaces maintained at the same temperature and heat transfer surfaces if they separate spaces maintained at different temperatures. A discussion of how to define heat transfer and heat storage surfaces will occur in later steps. In order to correctly "zone" the building it is necessary only to distinguish between the two.

A "zone" is a thermal, not a geometric, concept. A "zone" is an air volume at a uniform temperature plus all the heat transfer and heat storage surfaces bounding or inside of that air volume. EnergyPlus calculates the energy required to maintain each zone at a specified temperature for each hour of the day. Since EnergyPlus performs a zone heat balance, the first step in preparing a building description is to break the building into zones. The objective of this exercise is to define as few zones as possible without significantly compromising the integrity of the simulation.

Although defining building zones is somewhat of an art, a few general rules will keep the new simulation user out of trouble.

The question is, "How many thermal zones should be used to model this building?" The inexperienced building modeler may be tempted to define each room in the building as a zone, but the thermal zone is defined as a volume of air at a uniform temperature. The general rule then is to use the number of fan systems (and radiant systems) not the number of rooms to determine the number of zones in the building. The minimum number of zones in a general simulation model will usually be equal to the number of systems serving the building. The collection of heat transfer and heat storage surfaces defined within each zone will include all surfaces bounding or inside of the space conditioned by the system.

Refer "Getting started.pdf" for an example of thermal zoning.

When the building was zoned our objective was to define as few zones as possible.

Step 3: Prepare to Construct the Building Model

Working from blueprints or sketches and following the guidelines in Step 2, the building zones were determined. It is recommended that the engineer sketch the building with its zones. Surface dimensions should be included in the sketch. Additional geometric and surface information is required before an input file describing the building can be constructed.
Compile surface and subsurface information.

Building information:

Building North Axis: This syntax simplifies building geometry specification by designating one wall of the building as the building's north pointing axis. The building model North axis is measured from true (compass) North. Surface facing angles (see surface information below) are then specified relative to the building north axis.

Zone information:
Wall height: This is entered once. All walls are assumed to be the same height. If the height for a given wall differs from the specified height, the wall length should be adjusted by the user to give the correct equivalent area. In certain conditions this may not be possible and you will need to resize each wall accordingly.

Surface information:
Base Surface Type: Heat Transfer/Heat Storage Surfaces may be of the following types:
wall, floor, roof, internal mass, or subsurface.

Construction: The type of construction of the surface (see previous table).

Subsurface information:
1. Subsurfaces are Windows, Doors or GlassDoors
2. Area: Area of the subsurface.
3. Reveal: For windows only, the distance it is inset from the outside surface of a wall.

Step 4: Compile Internal Space Gain Data

What are the outputs available from HLCP?

HLCP has three distinct and exclusive types of outputs.

Type 1: Design loads - Design loads for summer, monsoon and winter based on WeDCo ambient design conditions.

Type 2: Monthly loads - hourly loads are calculated for a 12 representative days corresponding to the 12 months of the year. Data for these 12 representative days are extracted from WeDCo.

Type 3: Hourly loads are calculated for the user selected period (days).

What HLCP would not do?

Dynamic Simulation by changing building parameters such as orientation, etc. (one could always do a kind of "manual" simulation by re-loading data with different parameters).
Input from CAD packages, and interfacing with the same.
Moisture adsorption and desorption in building elements, moisture load calculations, load calculations for cold stores, deep freezers (or calculations for DB temperatures below 18 °C, 60% RH and snow conditions).
Radiant heating and cooling systems, passive and solar systems.
Energy calculations, simulations and costs.
Sizing and optimizing cooling equipment.
Any special convolution required by a specific user.
Effect of heat recovery.
Interface with Linux, Macintosh, and link with TRNSYS, SPARK or other programs.
Effect of external shading such as adjacent buildings.

What are the features of HLCP over the conventional heat load calculations being used?

Self-shading of the building.
Wall and roof tilts.
Window external shading and reveal effects.
Treated fresh air.
Monthly loads.
Validated simulation engine.
WeDCo and BIS (Bureau of Indian Standards) design conditions.

Can I do heat loads for multiple buildings?

No. You would need to do separate runs.

Can I change the outside design conditions given for various cities?

No.

Can I import a CAD drawing into HLCP?

No.

What is a "building", System" and "Zone", "multiple zones" as defined in HLCP?

Energyplus input is from a thermal model made by the user, from the building geometry inputs. Output is of the thermal model only.

A "zone" is a thermal, not a geometric, concept. A "zone" is an air volume at a uniform temperature plus all the heat transfer and heat storage surfaces bounding or inside of that air volume. EnergyPlus calculates the energy required to maintain each zone at a specified temperature for each hour of the day. Since EnergyPlus performs a zone heat balance, the first step in preparing a building description is to break the building into zones. The objective of this exercise is to define as few zones as possible without significantly compromising the integrity of the simulation.

The minimum number of zones in a general simulation model will usually be equal to the number of systems serving the building.

Thermal model:
Sketched by HVAC engineer.
Zone has a common temperature.
Walls have a common height.

Definition:

Building Building has Floors (Systems)
Floor (System) Floors have Zones (Zones)
Zone (Zone) Zone has uniform inside conditions.

Multi-zone 1 Building
Building: "n" Floors (Systems)
"n" Zones

Block load: 1 Building
1 Floor (System)
1 Zone

Building is: A closed polygon.

Technically speaking, there is no limit to the number of Zones, Surfaces, etc. that EnergyPlus can process. The input routines allocate according to how many of these the user enters. Practically speaking, your simulation may take longer with more complex / larger numbers of these items.

Self-shading:

Self shading on the building walls by other walls, will only be considered if the building is entered as one system and one zone, as would normally be done, for an hourly load calculation, which as it is, is for a single zone only. Else, multiple zones are "unconnected" so to speak, and self-shading is not considered.

Can I change the calculated ADP temperature and will it reflect the re-calculated dehumidified air quantity?

Yes.

Why do we have to create a "Project Master"?

Please explain how the "schedules" feature is to be used in HLCP.
We are not doing the energy calculations; hence the holiday schedules are not provided. All the calculations can be done for the basic mode: 01 January is a Monday, and there are only 365 days in the generic year.

Could you list out what is not possible with HLCP at this version?

100% fresh air applications.
Moisture transfer applications.
Direct import of CAD data.

Why are film coefficients missing from the U value calculator?

EP calculates the film coefficient based on exposure, wind speed and wind direction.

What is the time-step being used in HLCP?

1 hour.

Is moisture conduction considered in HLCP?

No.

Can I consider any external wall as a shaded wall?

Yes.

How are psychrometric calculations done in HLCP?

By using a commercial psychrometrci programme.

People: What does the "Activity Level" describe?

Activity level is the amount of heat generated by one person.
The values are obtained from 2001 ASHRAE Handbook of Fundamentals, page 8.7, Table 4.

Curtain Glazing: How can curtain glazing be handled in HLCP.

The concept of curtain glazing is akin to a passive trombe wall system, which is a glazing + solid opaque wall. Currently, you would have to model this as a separate zone.

Should I measure the outside dimensions of walls, or the inside dimensions?

Size of the wall is always the internal measure, although we look at the wall from outside when describing vertices. As far as the simulation is concerned, the inside and outside measurements are identical from a heat-transfer perspective. So, one could argue that the average of the two is more appropriate to pick up the additional outside heat transfer.

What are the outputs available in an hourly load analysis? Could you describe the output of the hourly load calculations?

Zone Window Heat Gain[W]
Zone Window Heat Loss[W]
Zone Opaque Surface Inside Conduction Gain[W]
Zone Opaque Surface Inside Conduction Loss[W]
Zone-Total Internal Latent Gain[J](Hourly)
Zone-Total Internal Radiant Heat Gain[J](Hourly)
Zone-Total Internal Convective Heat Gain[J](Hourly)
Zone-Total Internal Lost Heat Gain[J](Hourly)
Zone-Total Internal Visible Heat Gain[J](Hourly)
People-Sensible Heat Gain[J](Hourly)
People-Latent Heat Gain[J](Hourly)
People-Total Heat Gain[J](Hourly)
Electric Eq-Total Heat Gain[J](Hourly)
Electric Eq-Radiant Heat Gain[J](Hourly)
Electric Eq-Convective Heat Gain[J](Hourly)
Electric Eq-Latent Heat Gain[J](Hourly)
Electric Eq-Lost Heat Gain[J](Hourly)

Are the inputs available as an output file?

Yes, in the form of a Comma delimited input file.

The file structure is as under:

1 Units;
2 System name, Zone name, Rotation;
3 Walls/Partitions, Surface Name, Orientation, Exposure, Temp Diff, Length, Tilt, Construction name, U value;
4 Windows, Surface name, Window Name, Quantity, Length, Reveal, Height, Construction name;
5 Shades, Surface name, Window Name, Shade name, Overhang projection, Overhang elevation, Right fin projection, Right fin offset, left fin projection;
6 Doors, Surface name, Door Name, Quantity, Height, Width, Construction name, U value;
7 Flat roof, Ceiling,Ceiling Name, Length, Width, Area, Tilt, Exposure, Temp diff., Const. name, U value;
8 Gable roof, Roof Name, Length, Width, Height, Area, Tilt, Exposure, Temp diff., Const. name, U value;
9 Gable roof skylight, GableRoof name, Sky Light Name, Qty, Length, Width, Const. name, U value;
10 Floors, Ceiling Name, Length, Width, Area, Tilt, Exposure, Temp diff., Const. name, U value;
11 People, Nos, units, activity, Schedule name;
12 Lighting Flourescent, Value, units, ballast multiplier, Fraction return air, schedule;
13 Lighting incandescent, Value, units, Fraction return air, schedule;
14 Ventilation per person, Rate / quantity, total, units;
15 Ventilation air changes, Rate / quantity, total, units;
16 Treated fresh air, Qty, DB, WB, RH;
17 Equipment Sensible, Total, Diversity Factor, Fraction lost, Units, Schedule;
18 Equipment latent, Total, Units, Schedule;
19 Infiltration, Value, Units;
20 Schedule Occupancy, value, value, etc.;
21 Schedule Lights, value, value, etc.;
22 Schedule Equipment, value, value, etc.;

Can we model a zone with a return air plenum?

Yes, in the next version. But only for a single zone. (block load),

The RA plenum option represents the case of return air being taken back in the void above the false ceiling. In this case, the roof load gets added to the refrigeration load, but since it is a return air load, it does not get added to the room sensible load, and therefore not considered for dehumidified calculation.

HLCP FAQ

HLCP - FAQ