Energy Simulation Software - A Beginner's Guide

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Energy Simulation Software A Beginner’s Guide
E g simulation software is used my to determine the energy use and energy cost ofbuildings. This Technology Update describes three types of energy simulation software and indicates how you can obtain more informatwn about these programs.

What is Energy Simulation Software?
Energy simulation software is used primarily to determine energy use and energy cost for existing or proposed buildings. In some cases, it is also used to estimate HVAC equipment sizes, to estimate peak power demands, and to disaggregate energy end uses in buildings. For energy conservation programs, this type of software is used to compare the energy use of a building before and after the installation of energy efficiency technologies. For both existing and new facilities, energy simulation software requires input information describing various architectural, mechanical, and electrical features of the building as well as detailed building and equipment operations. Typical input information includes the following: W Wall, roof, and floor characteristics
W Insulation levels
W Glass properties

W Type of HVAC systems W Lighting systems W Control systems for lighting, HVAC and other equipment W Miscellaneous receptacle loads

Hot water system
W Building and equipment operating hours

W Temperature settings W Uiiy rate schedules tlt

Input requirements for the available programs vary widely. Most programs have standard default input values to allow less detailed data entry.

Toll-free Hotbe 1-800-872-3568

FAX 1-800-872-3882

Electronic Bulletin Board 1-800-762-3319


Once this information is entered, the software (1)processes the information using weather data to simulate the thermal load characteristics of the building, (2) simulates the W A C systems and controls to estimate terminal system coil loads and primary system energy (utility) demands, and (3)derives overall energy use and cost for the facility. In most programs, this overall energy use is broken down into subcategories such as space heating, space cooling, fans, lighting,service hot water, and miscellaneous receptacle equipment. Typically, the software provides monthly breakdowns. Some also provide graphical output.

temperature range for each month. Bin weather data methodology simply counts the hours of occurrence of outdoor dry bulb temperature within bins. Bin weather data are used to model heating, cooling, and ventilation loads in a building. Unless combined with one of the other two methodologies, the modified bin methodology can not predict peak power demands. Its major advantages are its speed and simplified input requirements.

with power (from hourly simulation). Typical day software estimates hourly building energy requirements using several "typical days" (e.g., one typical week day and weekend day per month). Its principal advantages are its ease of use and ability to predict peak demand.

Availability of Energy Simulation Software
There are many public domain and proprietary software products available for energy simulation. The Table 1 provides information on some of the energy simulation programs currently approved for Energy Smart Design, a BPA-funded, utility-run program for new commercial building energy conservation. For each energy simulation program, the table indicates the name of the program, the simulation methodology used, and a contact name and telephone number for more information. The software package and methodology most appropriate for you depends on several factors. One is the complexity of the analysis and the degree of detail needed. 0thers include the availability of knowledgeable users, the complexity and ease o use of the prof grams, and the cost. None of the programs listed can be expected to produce accurate results for inexperienced users. The time

Hourly Simulation
Hourly simulation is the most sophisticated of the three methodologies. Hourly energy simulation software is typically used for more detailed analyses of building that have complex systems, schedules, and controls. In hourly simulation, complete, detailed calculations are performed for all 8,760 hours in the year (365days x 24 hours). The major advantages of the hourly simulation methodology are its accuracy, flexibility, and comprehensive results. Its principal disadvantage is that it requires detailed input, which means that using the methodology reliably is difficult and expensive.

Types of Energy Simulation Software
The wide variety of energy simulation software currently available cart be categorized by calculation methodology. Three differentmethodologies are in widespread use: modified bin simulation, hourly sirnulation, and typical day simulation.

Modified Bin Simulation
Modified bin energy simulation software is the most simplified of the three methodologies. It is usef l for evaluating less complex u building types such as small office and commercial retail. This methodology uses "bin" weather data. A bin represents a certain

Typical Day Simulation
The typical day methodology is a hybrid of modified bin and hourly simulation methods. Typical day methodology attempts to combine ease of use and speed (from modified bin methods)

Table 1

Partial List of Energy Simulation Software

ASEAM 2.1 COMPLY Trakload

I Modified bin simulation I Modified bin simulation I Modified bin simulation
Hourly simulation Hourly simulation Typical day Hourly simulation Hourly simulation Hourly simulation Hourly simluation Hourly simulation

ACEC Gable, Dodd, & Assoc. SRC Systems Lawrence Berkley Labs Acrosoft International Inc.

202-347-7474 41 5-428-0803 415-839-2700 41 5-486-5711 303-368-9225 513-228-2602 608-787-3926 916-363-8383 916-363-8383 800-842-5278 404-993-2406 51 2-490-7081 800-253-1794




The Trane Company ADM Associates ADM Associates BLAST Support Office Kyle Wilcutt
Ross F. Meriwether

Carrier Corp.


required to learn to use these programs can be subgtantial, and regular use is required if reliable results are to be expected. In general, the simplified programs are much easier to learn than are the detailed programs. The availabilf ity o well written documentation and technical assistance should also be a significant consideration when evaluating software. Other features such as on-line help and look-up tables will make using a program much easier. Your first

step should be to contact the manufacturer and request a demo diskette and/or literature. If possible, you should also speak with some current users of the software. The Electric Ideas Clearinghouse may be able to assist you with this. For more information on these software packages, you can call the Electric Ideas Clearinghouse at 1-800-872-3568. ClearingThe house has on file the documentation for some of these software

packages. On the Clearinghouse Electronic Bulletin Board, there are also a number of Special Interest Groups (SIGS) on specific energy simulation programs (Modem Access: 1-800-762-3319).

v Electric Ideas Clearinghouseis a
comprehensive information source for commercial and industrial energy users. It is operated by the Washington State Energy office and is part of the Electric Ideas technology transfer program sponsored by participating utilities and the Bonmille Power Administration. v Neither the United States nor the Bonmille Power Administration, the state of Washington,the Washington State Energy Ofice, nor any of theik contractors, subcontractors, or their employees make any warranty, expressed or implied, or assume any legal responsibility for the accuracy, completeness,or usefulness of any information, apparatus, product, or process disclosed within this publication. v Technology Update CH - 20 v Toll-freeHotline: 1-800-872-3568 Fax: 1-800-872-3882 Electronic Bulletin Board: 1-800-762-3319

U S Department of Energy. Architect's and Engineer's Guide to Energy .. Conservation in Existing Buildings, Volume One. DOE/RL/O183OP-H4.
April 1990. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. 1989 ASHRAE Handbook of Fundamentals. Chapter 28. Atlanta. 1989. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. ASHRAE Journal W A C & R Sofhoare Directory. Atlanta. 1990.

June 1992


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