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Building Technologies

Energy Plus Hysteresis PCM Model

Company Name: NRGsim Inc.
Program Office: Buildings
Location: Portland, OR
Email: Jeremiah Crossett, CTO;
Award Amount: $100,000
Project Term: 12 months
Project Status: Active
Participating Lab(s): National Renewable Energy Laboratory


Effectively heating and cooling buildings often depends on how their envelopes — the materials that separate the interior from the exterior — function, including their insulating power and reflectivity. One method for increasing the energy efficiency of buildings is to incorporate phase change materials into building envelopes. These materials are similar to the gel heating and cooling pads that we use to treat aches and pains in that they can store — and release — large amounts of heat energy.

NRGsim provides energy modeling and software services, specializing in modeling phase change materials for building envelopes. Such modeling comes with several challenges, such as translating measured data into the model, capturing hysteresis effects, and handling subcooling effects, which are key in lower cost phase change materials such as salt hydrate. While NRGsim has produced a prototype model, it is in an older programming language, and thus requires updating to comport with the industry-standard EnergyPlus model supported by the U.S. Department of Energy.

These services have a high potential to succeed with very low risk. Preliminary work has already been completed with these services and NRGsim is currently using it in their tools. Working with the National Renewable Energy Laboratory will allow NRGsim's development team to complete documentation, perform tests to find deficiencies and issues with the code until it's satisfactory to make the services production ready. Once all code, documentation, and other supporting materials are complete, the code will be deployed with the next major release of EnergyPlus.


This project will allow the U.S. Department of Energy flagship simulation tool to more accurately model phase change materials in building envelopes, which is a key barrier for market adoption of this energy conservation measure. The energy modeling and software services that NRGsim will be providing through this voucher work will lower the barrier for engineers and other simulationists to evaluate the energy savings of building envelope phase change materials. The effectiveness of phase change materials has been previously researched and this task will be key in evaluating it in detailed building designs and large studies alike, fostering further market adoption and greater energy efficiency gains.


Buildings comprise nearly 40 percent of energy use in the United States and heating and cooling costs comprise the highest portion of electricity used in buildings. Helping developers and building managers reduce electricity costs and frees up capital for other investments and energy efficiency services are a growing economic sector in their own right. Accurate software simulations of energy use are critical for driving investment in energy efficiency.

Energy efficiency gains mean less strain on the grid and less fossil fuel energy being burned to supply electricity to buildings. Efficiency gains can shave peak power demand, in particular, when grid operators have to put their oldest — and most polluting — power plants online.

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