Home Science & Technology The house runs on 100% direct current electricity, a Purdue University project

The house runs on 100% direct current electricity, a Purdue University project


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

A project to transform a 1920s West Lafayette home into a DC nanogrid home began in 2017 under Eckhard Grohlch of William E. and Florence E. Perry Mechanical engineeringand a member of Purdue’s Center for high performance buildings. “We wanted to take an ordinary house and completely modernize it with DC appliances and DC architecture,” Grohl said. “To the best of my knowledge, no other existing project has attempted to experimentally demonstrate the improvement of energy consumption using DC electricity in residential areas as extensively as we have.”

The early years were spent renovating and upgrading the infrastructure, as well as introducing energy-enhancing measures such as insulation and new windows. Rectify Solar provided a complete installation of solar panels on the roof, and industry partners supplied new appliances and HVAC systems.

Then came the hardest part.

“Large-scale DC power distribution through the home in the 21st century is truly uncharted territory,” said Jonathan Ruda, Ph.D., from Purdue in 2020. graduate who worked as the project’s lead researcher. “You can’t just go to a hardware store and buy DC circuit 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 integration of both direct current power from solar panels, wind turbines or batteries and alternating current from local power grids into the home. The system is also modular, so it can grow and adapt to different sizes of homes and businesses by combining multiple power sources.

“Building the 380 VDC load center has certainly been a challenging and rewarding experience,” said Phil Teague, co-founder and CEO of the company Rectify LLC. “We used biomimicry and the neural connections of the brain as our inspiration, and added smart technology and control mechanisms. Switching to DC can simplify homes, buildings and the grid as a whole. This project helped me realize that DC is not only the future, it always has been.”

Why DC power supply?

Alternating current has been the dominant infrastructure in the world’s electrical grids since the late 1800s, when a “current war” saw Thomas Edison’s dream of a direct current-based electrical infrastructure lose to George Westinghouse’s alternating current system. But while it may seem like the “war” is 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 – as well as energy storage in large home batteries. All of these devices naturally run on DC, so a DC-based home infrastructure allows for the delivery of this energy with almost no waste or inefficiency.

The second event was a series of extreme weather events that exposed the fragility of the US electrical grid. Winter snow storms in Texas, as well as intense heat in the Southwest, have caused power outages and outages to become more common.

“The United States grid is like one of those ball-balancing games where you tilt the table so the balls don’t fall. However, leaning to one side to save one ball can cause the others to collapse,” Orr said. “If too many homes suddenly start requiring extra energy for heating or air conditioning, the grid can become severely unbalanced as it tries to respond.

“The DC home can potentially sustain itself for short periods of time by generating its own renewable energy and being disconnected from the grid with on-site energy storage. This ultimately minimizes the load on the external network in emergency situations. Events like the Texas storm are a great illustration of how a DC home can benefit people and society.”

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

A living laboratory

Purdue’s Nanogrid House is a “living lab.” Graduate students live in the house full-time to offer real-world feedback on its comfort and usability. They installed sensors in each room to determine whether people are present so that the HVAC system only conditions air where it is needed.

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

This is the second living lab Grohl has established near Purdue’s campus ReNEWW Housewhich explores technologies for zero energy, water and waste.

Emerson software and control system provided. “Next-generation energy solutions that will drive sustainable development in the future are envisioned and realized by the next generation of innovators,” said Bob Yeager, president of Emerson’s Power and Water Division. “We are proud of the role our Ovation software and integrated automation technologies play in bringing the visions of student innovators to reality, and are excited to see how a new generation of thinkers will use our digital foundation to keep the network stable and build more sustainable and resilient communities. »

Other industry partners for the DC Nanogrid House include Carrier Corp., Duke Energy, Southern California Edison, Manufactured by Rheem, Trane Technologies Company, Whirlpool Corp., Ingersoll Rand, Daikin Global, Marshall DC Lightingand Regal Rexnord Corp.

“It’s been really amazing to see the interest in it,” Orr said. “We started this project as a proof of concept. But as our country experiences more and more problems with the network, companies are actively trying to integrate our work. People are interested in it from all aspects: from the electrical side, from the thermal side, from the automation and control side. It’s the perfect stand to experiment with these technologies.”

The Purdue innovators worked with Purdue Research Foundation Office of Technology Commercialization to patent this technology. The researchers are looking for partners to continue developing their technology. For more information on licensing and other opportunities, contact Dhananjay Sevak of OTC at dsewak@prf.org and specify the track code 2021-ORE-69439.

Writer: Jared Pike, jaredpike@purdue.edu765-496-0374

Additional reporting by Kelsey Lefever, Christy McCarter

Source: Eckhard Grohl, groll@purdue.edu


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