ESim: ESim is a building energy simulation tool that combines powerful computational capabilities and graphics in an easy-to-understand user interface. It can be used for design, commissioning and retrofit-analysis purposes. Its unique capabilities make calibrating simulation models to measured energy consumption easier than ever before. It is appropriate for passive-solar, single-zone and large multi-zone buildings with sophisticated HVAC systems and controls.

All simulation tools must strike a balance between complexity and ease-of-use. Complicated simulation tools may require large amounts of input data, much of which must be estimated, and can quickly become unwieldy and difficult to calibrate. Simplistic tools may have difficulty capturing essential energy flows and can produce unreliable results. ESim seeks the middle ground. The computational algorithms are based on fundamental thermodynamic, psychrometric and heat-transfer calculations. However, data input requirements are the minimum necessary to model the major energy flows, control systems and equipment.

To simulate building energy use on an hour-by-hour basis, ESim uses TMY2 or WEA format weather data files. TMY2 files contain typical meteorological data for over 200 US cities and are available free-of-charge over the internet. WEA files contain a subset of the data in TMY2 files and can be created by ESim from TMY2 files, measured data and other sources. Use TMY2 weather data when making simulations runs to support the design of a new building. Use WEA files containing actual meteorological data when calibrating simulation results to utility bills or measured performance data in existing buildings.

ESim’s building load calculations consider heat exchange through the building envelope, solar loads, internal sources of heat and humidity, and air exchange. Solar radiation on each building surface is computed using the HDKR ansiotropic sky model. Energy-storage effects are considered using transfer-function and finite-difference algorithms. Primary equipment efficiencies take into account part loading and ambient conditions. The performance of important HVAC control systems such as night-setback thermostats, economizer cycles, hot-deck reset schedules and VAV controls can be simulated.

ESim produces both graphical and numerical output. Time-series, XY and three-dimensional graphics of simulated results and calibration data are automatically available at the end of each simulation run. ASCII files of numerical results are also created automatically for more in-depth analysis.

ESim simplifies the critical process of calibrating simulation results to a building's actual energy consumption by 1) creating hourly weather files from the actual average daily temperatures during the calibration period and 2) graphing both simulated and measured energy consumption on the same plot. These unique capabilities make calibration quicker, more accurate, and easier than ever before.

Download A Free Copy of ESim (About 4 MB, no user support or warranty provided)