What is EnergyPlus

EnergyPlus is the energy modeling engine that the US Department of Energy is betting the future of building modeling on. It replaces the DOE-2 engine that runs eQUEST and improved algorithms for modeling complex mechanical systems and building designs. The program is used for building energy analysis and thermal load simulation. There are a number of Graphical User Inerfaces (GUIs) that sit on top of the EnergyPlus engine, such as Simergy, OpenStudio and DesignBuilder.

EnergyPlus, DOE’s fully integrated building; heating, ventilation, and air conditioning (HVAC);
and renewables simulation program is one of the most robust simulation tools available in the
world today. It models building heating, cooling, lighting, ventilating, and other energy flows, as well as water. The program includes many innovative simulation capabilities, such as time steps of less than an hour, modular systems and plant integrated with heat balance-based zone simulation, multizone air flow, thermal comfort, water use, natural ventilation, and photovoltaic systems.

What it can do:

Integrated, simultaneous solution where the building response and the primary and secondary systems are tightly coupled (iteration performed when necessary)

Sub-hourly, user-definable time steps for the interaction between the thermal zones and the environment; variable time steps for interactions between the thermal zones and the HVAC systems (automatically varied to ensure solution stability)

ASCII text based weather, input, and output files that include hourly or sub-hourly environmental conditions, and standard and user definable reports, respectively

Heat balance based solution technique for building thermal loads that allows for simultaneous calculation of radiant and convective effects at both in the interior and exterior surface during each time step

Transient heat conduction through building elements such as walls, roofs, floors, etc. using conduction transfer functions

Improved ground heat transfer modeling through links to three-dimensional finite difference ground models and simplified analytical techniques

Combined heat and mass transfer model that accounts for moisture adsorption/desorption either as a layer-by-layer integration into the conduction transfer functions or as an effective moisture penetration depth model (EMPD)

Thermal comfort models based on activity, inside dry bulb, humidity, etc.

Anisotropic sky model for improved calculation of diffuse solar on tilted surfaces

Advanced fenestration calculations including controllable window blinds, electrochromic glazings, layer-by-layer heat balances that allow proper assignment of solar energy absorbed by window panes, and a performance library for numerous commercially available windows

Daylighting controls including interior illuminance calculations, glare simulation and control, luminaire controls, and the effect of reduced artificial lighting on heating and cooling

Atmospheric pollution calculations that predict CO2, SOx, NOx, CO, particulate matter, and hydrocarbon production for both on site and remote energy conversion

Simergy is DOE’s GUI interface project for EnergyPlus and is well funded.

Using EnergyPlus

EnergyPlus can be downloaded for free on the DOE website after giving them some of you information.

Prerequisite Experience Use EnergyPlus

EnergyPlus by itself is complicated to user because, by itself, it only interacts with text files. Therefore you have to know exactly what to tell EnergyPlus to get anywhere. A background in energy modeling and building systems is required. If you want to use EnergyPlus, but have limited experience, then one of the GUI interfaces might be a good option.

Who Developed EnergyPlus?

The US Department of Energy.

Where to get EnergyPlus Training?

Energy-Models.com is developing an introduction to EnergyPlus training.

EnergyPlus Development and Updates

The DOE has made a commitment to continually improving EnergyPlus, a necessity if they want energy modelers to use the project.

EnergyPlus is also tested extensively before each release. The three major types of tests that are currently conducted:

Analytical tests:
HVAC tests, based on ASHRAE Research Project 865
Building fabric tests, based on ASHRAE Research Project 1052
Comparative tests:
ANSI/ASHRAE Standard 140-2011
International Energy Agency Solar Heating and Cooling Programme (IEA SHC) BESTest (Building Energy Simulation Test) methods not yet in Standard 140
EnergyPlus HVAC Component Comparative tests
EnergyPlus Global Heat Balance tests
Release and executable tests