Modeling Breakthrough Allows Researchers To Account for Occupant Comfort and Assess Smart Building Technologies

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NREL Releases Open-Source OCHRE To Study Emerging Controllable Technologies Within the Home and the Impacts on the Grid

Homes across the country are incorporating new technologies, such as energy-efficient heat pumps, heat pump water heaters, electric vehicles, rooftop solar, and energy storage systems. The new devices are often equipped with cloud-connected controllers that can adjust the quantity and timing of energy consumption. With the popularity of smart thermostats and new electric water heaters equipped with connectivity as several states recently passed laws requiring it, connected devices are rapidly being installed in homes all across the United States. The controllable devices enable people to save on energy costs, reduce carbon emissions, and improve electric grid operations while remaining comfortable inside.

Connected appliances also provide substantial value to utilities, better ensuring supply always equals demand without having to build a new power plant. And, as utilities deploy more time-of-use rates, energy usage can be shifted from periods with higher electricity rates into less expensive time periods, which can save occupants money—but may also impact their comfort. It is a complex situation with multiple stakeholders. It is also a situation that more and more homeowners will find themselves in as new requirements pass and more technology is available in the market.

OCHRE

About five years ago, a group of researchers from across the National Renewable Energy Laboratory (NREL) looked at these trends and realized they shared a common, unaddressed need in tools across buildings, grid planning, and strategic analysis. “Everyone needed the same thing—a way to model smart building technologies and controllable equipment in homes,” said Jeff Maguire, research engineer at NREL. “And we all needed a way to integrate that model into our usual stream of work.”

“With the changes in how people are using energy, we need improvements in building energy models, which previously did not account for device controllability or impacts on occupant comfort,” Maguire said. That need sparked the idea for the Object-oriented Controllable High-resolution Residential Energy (OCHRE)™ model that simulates a variety of behind-the-meter equipment, ranging from just one home up to thousands of buildings connected to the grid simultaneously.

“OCHRE takes people into account in building modeling. Instead of simply assuming how an HVAC [heating, ventilating, and air conditioning] energy load would shift during an event, OCHRE considers how hot or cold the living space gets, and will account for if you run out of hot water,” Maguire added. “Load shifting can benefit the grid, but it only works if you make sure people are still comfortable. Done carefully and correctly, this is something everyone can do to reduce their bills while helping support more renewable energy.”

Without any direct funding, Maguire and co-principal investigator and research engineer Michael Blonsky “crowd-sourced” funds from different research projects across the laboratory that would benefit from the technology. “Without OCHRE, researchers would be left piecing together the variety of tools currently available, leading to simplified assumptions and possibly not the most rigorous approach to modeling and assessing the potential benefit of these new technologies,” Maguire explained.

From an Idea to an Open-Source Model

Fast-forward to 2023, OCHRE is now an open-source tool that models home energy consumption, both electric and natural gas, at a high resolution—down to a single minute. The model incorporates controllable HVAC equipment, water heaters, electric vehicles, solar photovoltaics, and batteries and allows researchers to create models across a diversity of buildings, including geographic and equity-based metrics.

“OCHRE’s temporal resolution is where it stands out, providing a more detailed assessment of impacts when connected to the grid,” Blonsky said. “The 1-minute time series and controls let researchers model HVAC cycling on and off, for example, where other tools will set it to a constant part-load value over longer time periods. This high level of detail is not available with other tools but is necessary to study load flexibility and the impacts of these emerging technologies.”

The ability to model the building’s thermal envelope, along with interactions between electrical and thermal loads for different control strategies, will allow decision makers to see how energy loads shift. OCHRE also allows users to rapidly develop and test new control strategies for devices, helping people determine what an optimal control might look like and what sensors would be required to implement said control. Understanding these trade-offs is important to avoid costly electric panel and distribution system upgrades and for connected communities of the future. OCHRE is Python-based and leverages capabilities from NREL’s established modeling tools, including EnergyPlus®, BEopt™, ResStock™, System Advisor Model (SAM), and Electric Vehicle Infrastructure-Projection Tool (EVI-Pro).

Users can access OCHRE and supporting documentation via GitHub.

Integrated Building Research

Built with cross-disciplinary use in mind, OCHRE seamlessly integrates accurate and controllable residential building models into a variety of different projects.

“OCHRE is truly a mix of a building modeling tool and a grid modeling tool, so grid experts don’t have to be building experts to see how building technologies impact the grid,” Blonsky said. “This gives grid researchers like myself an easy way to accurately depict the wide variety of homes across the country, rather than oversimplifying our building stock assumptions. I can specify the geography and building characteristics that I want, and OCHRE will do the building modeling for me.”

By integrating with ResStock, a large-scale residential energy analysis tool, OCHRE can simulate buildings based on income level and other equity-based metrics to help decision makers understand implications of funding programs, building codes, or emerging technologies.

Maguire added, “And as a building technologies researcher, I never thought about reactive power. But now with OCHRE, I’ve learned more about grid modeling and now we’re able to do more integrated and accurate research. One of the big benefits of this collaborative approach to developing the tool is we’re able to learn from each other.”

Next up, Blonsky and Maguire have their sights set on research in distributed energy resource aggregators, or virtual power plants. This growing field has complex modeling needs to aggregate thousands of homes and will benefit from OCHRE’s unique capabilities.

“We anticipate the prevalence of OCHRE only growing and hope to see it used in industry in the near future,” Blonsky said.

Published Work

Learn more about OCHRE and its capabilities through the following publications:

Explore NREL.gov for more information on Building Technologies, Grid Modernization, or Energy Analysis research.

News update from NREL.