EnergyPlus

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Project website: http://energyplus.net/

DOE Technology Manager: Amir Roth

Principal Investigator: Luigi Gentile Polese

Performers:

  • National Renewable Energy Lab (NREL) – Golden, CO
  • Lawrence Berkeley National Lab (LBNL) – Berkeley, CA
  • Oak Ridge National Lab (ORNL) – Oak Ridge, TN
  • GARD Analytics – Arlington Heights, IL
  • Florida Solar Energy Center (FSEC) – Cocoa, FL
  • Energy Archmage Inc. – Nederland, CO
  • University of Illinois (UIUC) – Champaign, IL
  • Oklahoma State University (OSU) – Stillwater, OK
  • Big Ladder Software – Denver, CO
  • Objexx Engineering – Needham, MA
  • Fraunhofer CSE – Cambridge, MA
  • Empty Crate Software – Denver, CO

Partners:

  • Trane Inc. –  La Crosse, WI
  • Autodesk Inc. – San Rafael, CA
  • Carrier Corp. – Charlotte, NC
  • Sefaira (Trimble Navigation Ltd.) – New York, NY
  • Daikin USA – New York, NY

DOE Funding: $2,100,000 in FY17; $74,600,000 to date

Cost Share: $350,000 in FY17; $1,800,000 to date

Project Term: 1997 -

Funding Opportunity: Emerging technologies core funding

Related Projects: OpenStudio, Spawn-of-EnergyPlus, Method of Test for Energy Simulation, Lab RFP: Empirical Validation and Uncertainty Characterization, BENEFIT: Hybrid Modeling, BUILD: Grey-Box Models for Hybrid RTUs, SBV: Advanced PCM Model, AIA 2030 Commitment DDx, Scout

Project Objective

EnergyPlus™ is DOE’s open-source whole-building energy modeling (BEM) engine, the successor to DOE-2.1E. Under development since 1997, EnergyPlus embodies the state-of-the-art in BEM knowledge in a comprehensive and robust engine that is continuously maintained, thoroughly documented and fully supported. BTO releases two annual updates to EnergyPlus, one in September and one in March—version, 8.7.0, will be released March 31, 2017.

EnergyPlus implements detailed building physics for air, moisture, and heat transfer including treating radiative and convective heat-transfer separately to support modeling of radiant systems and calculation of thermal comfort metrics; calculates lighting, shading, and visual comfort metrics; supports flexible component-level configuration of HVAC, plant, and refrigeration systems; includes a large set of HVAC and plant component models; simulates sub-hourly timesteps to handle fast system dynamics and control strategies; and has a programmable external interface for modeling control sequences and interfacing with other analyses. EnergyPlus is tested according to ASHRAE Standard 140 methodology, which is currently being extended with measured data from well-characterized, highly instrumented test facilities. In 2003, EnergyPlus received an R&D 100 award.

Historically focused on commercial buildings, EnergyPlus has been expanded with modeling capabilities relevant to residential buildings and data centers. Residential enhancements include an improved ground heat transfer model, an improved infiltration model, models for residential equipment like integrated water-heating/air-conditioning heat-pumps (IHP), and a new model for duct heat loss. Data center enhancements include models for IT equipment and computer room air conditioners (CRAC)—the EnergyPlus team is developing these features in coordination with ASHRAE TC 9.9 in support of the 90.4 data center energy efficiency standard. Other recent additions include new physics-based models for variable refrigerant flow (VRF) air conditioning systems, expanded modeling of dedicated outdoor air systems (DOAS), and support for HVAC fault modeling and urban-scale modeling. A recent emphasis has also been on improving EnergyPlus execution speed. Over the past several versions, EnergyPlus execution time has been reduced by a factor of over two, with greater speedups on large models. 

Project Impact

EnergyPlus supports a variety of use cases including integrated design of new buildings and retrofits, design guide development, development of and compliance with energy-efficiency codes like ASHRAE 90.1, asset ratings like DOE’s Commercial Energy Asset Score, green certificates like USGBC’s LEED, performance documentation for financial incentives from utilities and governments, and dynamic applications like automated fault-detection and diagnostics (AFDD) and model-predictive control (MPC).

Arguably, the use case that contributes most directly to energy efficiency is integrated design. DOE tracks the use of EnergyPlus in integrated design via the American Institute of Architects (AIA) 2030 Commitment, a voluntary reporting program that in 2015 comprised over 150 architecture firms and almost 1 billion square feet in U.S. commercial new construction. Analysis of 7,100 projects submitted from 2013 to 2015 shows that EnergyPlus use has grown to 10% of modeled projects—61% of projects use BEM—and that projects using EnergyPlus average 51% EUI reduction over CBECS 2003 baseline, relative to 44% for projects using all BEM tools and 29% for projects using no BEM tools. Using these figures, we project that integrated design using EnergyPlus has the potential to save 800 TBTU a year by 2030.

EnergyPlus has had significant recent uptake by both end users and commercial vendors. The last several versions have averaged over 37,000 downloads per update. Recent years also saw the release of several new third-party tools and user interfaces, including offerings from Sefaira, Autodesk, and Trane. A more complete listing of EnergyPlus based applications and services can be found at the new Building Energy Software Tools Directory.

Supporting Resources

There are a number of support and feedback channels for EnergyPlus. Open, peer-to-peer support is provided via the UnmetHours forum—EnergyPlus developers and advanced users receive email notifications from the forum and most questions are answered within a few hours, if they have not already been asked and answered previously. An email-based helpdesk is available for more in-depth support about projects with privacy constraints. Several organizations offer on-line and in-person EnergyPlus training. A listing is available on the Building Energy Software Tools Directory.

New features can be suggested, voted on, refined, and tracked on the EnergyPlus UserVoice site. Bug reports can be filed and tracked on the GitHub issues page.

Recent Publications and Presentations