A team of researchers at Purdue University are retrofitting a 1920s home to run completely on DC current.
A 1920s-era home in West Lafayette, Indiana, has been converted to run entirely on direct current (DC) power. Graduate 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 nano-grid.
Image: Purdue University photo/Jared Pike
While most homes run on alternating current (AC) power because that’s what comes from the utility lines from the grid, researchers at Purdue University decided to switch a home over to all direct current (DC) power.
Why? Back in the late 1800s Thomas Edison had a dream of a DC-based electrical infrastructure, but that dream lost to George Westinghouse’s AC system. In recent years, however, with renewable energy sources generating DC power, it would make a home more efficient if the electricity did not have to be converted to AC.
“We wanted to take a normal house and completely retrofit it with DC appliances and DC architecture,” said Eckhard Groll, the William E. and Florence E. Perry Head of Mechanical Engineering, and member of Purdue’s Center for High Performance Buildings. “To my knowledge, no other existing project has pursued an experimental demonstration of energy consumption improvements using DC power in a residential setting as extensively as we have.”
The project to transform a 1920s-era West Lafayette, Indiana home into the DC Nanogrid House began in 2017 under Groll’s direction. The first years were spent renovating and upgrading the infrastructure, and they added insulation and new windows to increase the home’s energy efficiency.
Rectify Solar provided a full installation of solar panels on the roof, while industry partners supplied new appliances and HVAC systems. The 14.3 kw rooftop solar system brings the all-electric home to net zero. Rectify installed Panasonic panels, inverters from CE+T America, and a POM Cube 20 kw/h battery system.
“Large-scale distribution of DC power through a house in the 21st century is really uncharted territory,” said Jonathan Ore, a 2020 Purdue Ph.D. graduate who served as the lead researcher on the project. “You can’t just go to the hardware store and buy DC circuit breakers or other critical distribution systems. We had to create this infrastructure from scratch.”
Purdue researchers, in collaboration with Rectify Solar, developed and jointly own a patented distribution system that enables the house to integrate both DC power from solar panels, wind turbines or battery storage with AC power from the local utility.
“The creation of the 380-volt DC load center was definitely a challenging and rewarding experience,” said Phil Teague, co-founder and CEO of Rectify LLC. “We used biomimicry and the neural connections of the brain as our inspiration, and added smart technologies and control mechanisms. Transitioning 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 was.”
“A DC-house can potentially sustain itself for short periods of time by generating its own renewable energy and detaching from the grid through the help of on-site stored energy,” said Ore. This ultimately minimizes the strain on the outside grid in emergency situations. Events like the Texas storm are perfect illustrations of how a DC-house can benefit individuals and the community.”
To monitor the DC home for its comfort and usability, graduate students are living in the home full time. They’ve installed sensors in every room to detect whether people are present so that the HVAC system only heats or cools the areas of the home that are in use.
“This gives us the opportunity to perform both cutting-edge research on energy-saving opportunities and observe its potential benefits in a truly real-world setting, rather than just relying on simulations,” Groll said.
“It’s been really amazing to see the interest in this,” Ore said. “We started this project as just a proof of concept. But as our country experiences more and more issues with the grid, companies are actively seeking to integrate our work. People are interested in it from every aspect: from the electrical side, from the thermal side, from the automation and management side. This is a perfect testbed to experiment with those technologies.”
Purdue innovators have worked with the Purdue Research Foundation Office of Technology Commercialization to patent this technology. The researchers are seeking OEM partners to continue developing their technology and to take it to market.
As a result of this project, Phil Teague will be speaking at RE+ in Anaheim next month about this project on the topics of “DC is the Future, It Always Was”, and “DC Microgrid Design-Build Lessons Learned”.
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More articles from Anne Fischer
Let me see if I understand this. These folks have completely retrofitted a house to run on dc that required replacing all the electrical appliances and breakers for achieving some level of added efficiency. This seems to be a perfect example of just because you can do something, it doesn’t mean that it’s a good idea.
It makes complete sense! Most of our lighting (LED) can be run easily on DC – most of our electronics are purely DC, and we have to plug in transformers to reduce the AC voltage to the 5-24v most of these devices use, or to charge the batteries. Motors are more and more commonly DC, and any appliance or tool that uses one can be retrofitted easily. Panels generate DC, batteries store DC. What doesn’t make sense is letting someone patent any of this, or adding any barriers to developing this further. We should be developing standards that encourage the adoption of DC in all new construction, or remodeling.
Exactly. It can all be done. What doesn’t make economic sense is retrofitting an entire existing electrical residential and commercial infrastructure.
You must have no experience with 100 year old homes – to make them efficient, they generally require a substantial amount of work – insulation in walls and ceilings that never had any, replacing heavily corroded old plumbing, and even removing old knob-and-tube wiring ( and the occasional gas lighting fixture) and replacing it all with safe/modern systems. It makes far more sense to do these retrofits with an eye towards the future – and that includes solar, batteries, and even DC wiring.
Yes, many devices today are in fact DC. However, lighting, electronics, variable speed DC motors, PV modules/strings, batteries all use, generate or store energy at different voltages. A TV or computer monitor may require 400 VDC, while lighting may be 24 VDC, and small devices 5 VDC. A PV string might be anywhere from 50-450+ VDC. You’ll still need DC/DC conversion everywhere, which if I understand correctly is part of the reason AC distribution won in the first place: ease of voltage conversion using transformers (along with the inherent safety of AC). Is DC/DC conversion that much more efficient than a AC/DC inverter? I’m not saying it’s a bad idea, but there’s not enough information here to understand how these nuances will be addressed or what the net benefit will be.
If DC becomes economically feasible by its own accord, fine. Don’t be stupid and make some dumb declaration like “we will be all DC by 2050”. Let the market decide. Don’t use my tax dollars to make your dream dictate come true!
As a proof of concept — these are university researchers after all — this is a great idea. (Now, trying to convince builders to do this on new construction, that’s a much, much harder problem!) One thing not mentioned is what DC voltage they are running. Seems to me they are replacing all the old AC/DC converters with new DC/DC converters to get the right voltage. Is that still a win?
No need for the high voltage battery plant. There are hundreds ( perhaps thousands) of off grid cottages and homes that are running with only 12V DC wiring. Most of what we need in the way of electric powered devices have useful DC varients. Refrigerators and freezers are available in 12 or 24 Volt DC. LED lighting of course is available in 12 volt DC as are various fans and water pumps to run the other mechanical systems. Basically, anything that can be powered off of a “cigarette lighter” outlet is applicable. No exotic battery plant is needed either. 12 Volt deep cycle, either old fashioned lead acid or the pricier ( but cost effective Lithium Iron) batteries can be scaled to you needs. One important detail is to wire the house with #10 wiring for most circuits and #6 for the higher amperage devices like refrigerators.
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