House runs 100% on DC – Purdue University project

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Did you know that there is a silent war going on in your house? Alternating current (AC) comes from the grid, but many of your appliances and lights are powered by direct current (DC). Each time you plug in a TV, computer, or cell phone charger, the power must be individually converted from AC to DC – a costly and inefficient process. Purdue University researchers have proposed a solution to the problem by converting an entire home to run on its own efficient, DC-powered nanogrid.

The project to convert a 1920’s West Lafayette home into the DC Nanogrid House began in 2017 under the direction of Eckhard Grollthe head of William E. and Florence E. Perry mechanical engineeringand member of Purdues Center for High Performance Buildings. “We wanted to take a regular house and retrofit it completely with DC appliances and DC architecture,” Groll said. “To my knowledge, no other existing project has pursued an experimental demonstration of improvements in energy use using direct current in a residential environment as comprehensively as we have.”

The first few years were spent renovating and upgrading the infrastructure and adding energy improvements such as insulation and new windows. correct solar provided a full installation of solar panels on the roof, while industrial partners supplied new equipment and HVAC systems.

Then came the difficult part.

“Distributing DC power widely through a 21st-century house is really new territory,” he said Jonathan Erz, a 2020 Purdue Ph.D. Graduate who served as the project’s lead researcher. “You can’t just go to the hardware store and buy DC breakers or other critical distribution systems. We had to build this infrastructure from scratch.”

Purdue researchers, in collaboration with Rectify Solar, have developed a patented distribution system that allows the home to integrate both DC power – from solar panels, wind turbines or battery storage – and AC power from local electric utilities. The system is also modular, so it can grow and adapt to different sizes of homes and businesses by integrating multiple power sources.

“Creating the 380 volt DC load center has definitely been a challenging and rewarding experience,” said Phil Teague, co-founder and CEO of Correct LLC. “We took inspiration from biomimicry and the brain’s neural connections and added intelligent technologies and control mechanisms. The transition to DC can simplify homes, buildings and the power grid as a whole. This project helped me realize that DC is not just the future, it always has been.”

Why direct current?

AC power has been the dominant infrastructure in the world’s power grids since the late 19th century, when Thomas Edison’s dream of a DC-based electrical infrastructure lost to George Westinghouse’s AC system in the “War of Currents.” But while the “war” appears to be over, two recent developments have prompted researchers to re-examine the benefits of DC. The first is the increasing availability of renewable energy sources – solar panels and wind turbines – and energy storage in large battery packs for home use. These devices are all DC in nature, so a DC-based home infrastructure makes it possible to deliver this energy with almost no waste or inefficiency.

The second development is a series of extreme weather events that have exposed the fragility of the US power grid. Winter snowstorms in Texas and extreme heat in the Southwest have caused brownouts and power outages to become more frequent.

“The United States grid is like one of those marble balancing games where you tilt the table so the marbles don’t fall off. However, if you tilt in one direction to save a marble, the rest can fall off,” Ore said. “If suddenly too many households are requesting additional energy for heating or air conditioning, the grid can become very unbalanced trying to respond.

“A DC home can potentially be self-sufficient for a short period of time by generating its own renewable energy and off-grid using on-site stored energy. This ultimately minimizes the load on the outer network in emergency situations. Events like the Texas storm are perfect examples of how a DC home can benefit individuals and the community.”

A 1920’s home in West Lafayette, Indiana was converted to run entirely on direct current (DC). PhD students live in the house full-time while Purdue researchers (from left) Eckhard Groll, Jonathan Ore and Alex Boanta monitor the energy efficiency of its self-contained DC nanogrid. (Photo by Purdue University/Jared Pike)

A living laboratory

Purdue’s DC Nanogrid House is a “living laboratory”. Graduate students live in the house full-time to provide hands-on feedback on its comfort and usability. They installed sensors in each room to detect when people are present so the HVAC system only conditions the air where it’s needed.

“This gives us the opportunity to both conduct cutting-edge research into energy saving opportunities and observe the potential benefits in a truly real-world environment, rather than just relying on simulations,” said Groll.

This is the second living lab that Groll set up near Purdue’s campus to follow his example ReNEW houseresearching technologies for net-zero energy, water and waste.

emerson supplied the control software and the system. “It’s not surprising that the next-generation energy solutions that are driving the future of sustainability are being dreamed up and realized by the next generation of innovators,” said Bob Yeager, president of Emerson’s power and water business. “We’re proud of the role our Ovation software and embedded automation technologies are playing in making the visions of student innovators a reality, and excited to see how a new generation of thinkers will use our digital foundation to maintain grid resiliency and… create more resilient, sustainable communities. ”

Other industrial partners at the DC Nanogrid House include Carrier Corp., duke energy, Edison from Southern California, Rheem Manufacturing, Trane Technologies, Whirlpool Corp., Ingersol Rand, Daikin Global, Marshall DC lightingand Regal Rexnord Corp.

“It was really amazing to see the interest in it,” Ore said. “We only started this project as a proof of concept. However, as our country has more and more network problems, companies are actively trying to integrate our work. People are interested in it from all sides: from the electrical side, from the thermal side, from the automation and management side. This is a perfect testbed to experiment with these technologies.”

Purdue innovators have worked with that Purdue Research Foundation Technology Commercialization Office to patent this technology. The researchers are looking for partners to further develop their technology. For more information on licensing and other opportunities, contact OTC’s Dhananjay Sewak at [email protected] and quote the trackcode 2021-ORE-69439.

writer: Jared Pike, [email protected], 765-496-0374

Additional Reporting by: Kelsey Lefever, Christy McCarter

Source: Eckhard Groll, [email protected]


 

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