A team of Purdue University researchers are converting a 1920s home to run entirely on DC.
A 1920s house in West Lafayette, Indiana was converted to run on direct current. Graduate students live in the house, and Purdue University researchers (left to right) Eckhard Grohl, Jonathan Ole, and Alex Boanta monitor energy efficiency.
While most homes are powered by alternating current (AC) because that’s the mains power line, researchers at Purdue University decided to convert the entire home to direct current (DC) power.
Why? Back in the late 1800s, Thomas Edison dreamed of an electrical infrastructure based on direct current, but that dream lost out to George Westinghouse’s alternating current system. However, in recent years, since renewables generate direct current, it will make homes more efficient if the electricity does not need to be converted to alternating current.
“We wanted to reinvent it with DC devices and DC architecture,” said Eckhard Groll, head of mechanical engineering for William E. and Florence E. Perry and a member of the Purdue University Center for High Performance Buildings. “To the best of my knowledge, no other existing project has used DC power in residential applications as extensively as our pilot demonstration of energy improvement.”
Under Groll’s direction, a project began in 2017 to convert a 1920s house in West Lafayette, Indiana into a DC Nanogrid home. The first few years were spent repairing and upgrading the infrastructure, adding insulation and installing new windows to improve the energy efficiency of the home.
Rectify Solar provided the complete installation of the rooftop solar panels, while industry partners provided new HVAC appliances and systems. Rooftop solar panels make all-electric homes zero. Correction of installed Panasonic 330 panels with 14.3 MWh per year, inverters from CE+T America and POM Cube 20 kWh lithium iron phosphate system with 12.5 kW continuous power.
“In the 21st century, large-scale DC-to-home distribution is really uncharted territory,” said Jonathan Ore, 2020 Purdue Ph.D. PhD student serving as the principal investigator of the project. “You can’t just go to a hardware store and buy DC circuit breakers or other critical power distribution systems. We have to build this infrastructure from the ground up.”
Researchers at Purdue University partnered with Rectify Solar to develop and co-own a patented power distribution system that allows homes to integrate DC power from solar panels, wind turbines or AC batteries from the local utility grid.
“Creating a 380 volt DC load center was certainly a challenging and rewarding experience,” said Phil Teague, co-founder and CEO of Rectify LLC. “We took inspiration from biomimicry and the neural connections of the brain and added intelligent technologies and control mechanisms.” . Switching to direct current can simplify homes, buildings, and the entire grid. This project made me realize that DC is not only the future, but always has been. ”
“A DC home can support itself for a short period of time by generating its own renewable energy and decoupling it from the grid with energy stored on site,” Ore said. This ultimately minimizes the load on the off-grid in emergencies. Events like the Texas hurricane are great illustrations of how D.C. homes can benefit individuals and communities. ”
To ensure the comfort and affordability of a DC home, graduate students live in the home full-time. They installed sensors in every room to detect the presence of people so that the HVAC system only heats or cools the parts of the house that are in use.
“This gives us the ability to conduct cutting-edge research into energy saving opportunities and observe their potential benefits in real, real-world conditions, rather than just relying on simulations,” Grohl said.
“It’s amazing to see people interested in this,” Ore said. “We started this project just to test the concept. But as there are more and more network problems in our country, companies are actively looking to integrate our work. People are interested in this from all sides: from the electrical side, from the thermal side, from the point of view of automation and controls. It’s the perfect testbed for experimenting with these technologies.”
Purdue Innovators partnered with the Purdue Research Foundation’s Technology Commercialization Office to patent the technology. The researchers are looking for OEM partners to continue developing their technology and bring it to market.
As a result of this project, Phil Teague will talk about the project next month at RE+ in Anaheim on the topics “DC is the future, it always has been” and “Lessons learned from DC Microgrid design and build.”
This content is copyrighted and may not be reused. If you would like to partner with us and reuse some of our content, please contact editors@pv-magazine.com.
Let me see if I understand this. These people have completely converted the house to run on DC, which requires replacing all appliances and circuit breakers to achieve some extra efficiency. This seems like a perfect example, just because you can do something doesn’t mean it’s a good idea.
That’s your opinion. I have been living in my home in DC for 25 years and the future is lower cost and higher efficiency. Another great thing is that this is the nominal voltage of an EV battery, so EVs can be charged at a low cost and used as storage for home runs. Solar power, small wind power, etc. can directly charge the battery. Many air conditioners must be variable speed, many run on DC because they have universal inputs or are usually designed specifically for DC. Others run on 48V DC for the home. You may need to add or replace wiring, but in older homes this is usually easy and time consuming anyway. Rated voltage 380 VDC DC is also a good voltage for creating small microgrids without expensive inverters and losing their no-load current.
It makes sense! Most of our lighting (LEDs) can easily run on DC – most of our electronics only run on DC and we need to plug in a transformer to bring the AC down to the 5-24V that most of these devices use, or to charge batteries . Motors are increasingly using DC motors, and any appliance or tool that uses a motor can be easily upgraded. The panel generates a constant current, and the battery stores a constant current. It does not make sense to patent someone or create any barriers to further development. We must have standards that encourage the use of direct current in all new buildings or renovations.
Exactly. All this can be done. What doesn’t make economic sense is to upgrade all existing electrical residential and commercial infrastructure.
You shouldn’t have experience with 100 year old houses – they usually require a lot of work to be effective – walls and ceilings have never been insulated, badly corroded old pipes replaced, or even old handles and pipe wiring (and sometimes gas pipes) removed. ). light fixture) and replace it with a safe/modern system. It makes more sense to make these modifications with an eye on the future, including solar power, batteries, and even DC wiring.
Of course, many years ago I had a 12V DC battery powered kitchen light. This way I have lighting even if the power goes out. I can charge the battery with solar power or cheap off-peak power. But the biggest impact is a slight undervoltage. Using a buck converter, I can turn off the 9V lighting. This reduces the required power to less than 1W. This way I can increase the amount of light available during a power outage. Although this turned out to be the case, I use it at 9V almost all the time. I have integrated a switch so I can choose if I want to run on 11.5V or 9V regulated voltage.
As a child in the 1940s/50s… Calcutta (now Kolkata) and a few other cities and places in India also only had 240V DC…. All appliances run on DC… I remember we had a DC refrigerator that used a small electric heater…​​…instead of a compressor (Kelvinator…??). )… The rest is DC. . Light bulbs, electric stove/heat pump, radio (there was no TV back then)… nothing new…
Maybe the Egyptians (at the time of the construction of the pyramids) also used direct current … because they found containers there that looked like batteries …
Just a word of caution…if you touch the DC wire…either it will knock you back (negative wire..??) or “don’t let go”..(positive wire..??)..so be careful. ..
Yes, many devices today are actually DC. However, lighting, electronics, variable speed DC motors, photovoltaic modules/strings, batteries all use, generate or store energy at different voltages. A TV or computer monitor may require 400VDC, lighting may require 24VDC, and a small device may require 5VDC. The PV string voltage can range from 50 to 450+VDC. You still have to do DC-to-DC conversion everywhere, which is one of the reasons AC distribution wins in the first place, if I understand correctly: simple voltage conversion with transformers (and the inherent safety of AC). Are DC/DC conversions more efficient than AC/DC inverters? I’m not saying this is a bad idea, but there isn’t enough information here to know how to account for these nuances or what the net benefit is.
If DC becomes economically viable on its own, that’s fine. Don’t be stupid and make stupid statements like “We’ll all be DC by 2050.” Let the market decide. Don’t use my taxes to make your dreams come true!
Since 1995, DC itself has been (at least for me) cost effective. Even with the ridiculously high price paid for panels at the time, it was a good deal, as the alternative was to use a gasoline generator for the cab. The data center is a niche market, but a large one on a global scale, as most developing countries are not connected to any network other than large centers. I don’t think the markets and industries that support DC need external support. College students use it as an exercise rather than a proof of concept because the project has no practical application. (I’m pretty sure)
As a proof of concept – after all, these are university researchers – this is a good idea. (Now, trying to convince builders to do this on new construction is a very, very difficult problem!) One thing that wasn’t mentioned was the constant stress they were working on. It seems to me that they are replacing all the old AC/DC converters with new DC/DC converters to get the correct voltage. Is it still a win?
@Nick Mitchell “It seems to me that they are replacing all the old AC/DC converters with new DC/DC converters to get the correct voltage. Or win?
Your switching power supply is a DC/DC rectifier and it would be a miracle if it wasn’t more efficient. Although the effectiveness of the circuit depends on the design and selected components. And if you have/use an old transformer (unswitched) AC power supply, it’s pretty inefficient. Everything is more efficient.
There is no need for a high-voltage battery factory. There are hundreds (maybe thousands) of stand-alone cabins and homes that only run on 12V DC wiring. Most of the electrical equipment we need has a useful DC option. Refrigerator and freezer available with 12 or 24V DC. Of course, LED lighting can be used at 12 volts DC, and various fans and water pumps can also be used to run other mechanical systems. Basically anything that can be unplugged from the cigarette lighter outlet will work. There is also no need for an external battery plant. 12V deep cycle, whether it’s an old lead-acid battery or a more expensive (but economical lithium-iron) battery that can be scaled to suit your needs. An important detail is to use #10 for most circuits and #6 for high current devices like refrigerators.
exactly! Just like we have 110V or 220V wiring standards, different plug shapes with different amperage, we can have a simple 12V and 24V DC standard with a few different plug types (not so many!) . We can even build in transformers to fit into existing junction boxes that fit standard USB A or C outlets. I admit we still need to cook and heat but maybe the heat pump will work, maybe induction will to work – I don’t claim to be EE, but the 12V DC system is all around us and applying it in our home comes down to me seems very logical to say that we don’t have to start with the complete invention of the bicycle
I believe there are manufacturers of 24 and 12 volt DC heat pumps! Pasting a link is really immoral, sorry.
I’m happy to try to follow this (no engineering/electrical experience) because I want (!) more (!) than the already amazing and fast PV development :: I also want to participate in something like -using- cultural change in addition to new science. The parameters that utility developers and financial companies give us about what we should want and what is available in the real world are often mostly related to how the real world fits in with the preferred business model and works with the preferred business model that provides desired profit. Please continue this story.
I use the appropriate fuses to connect all 12V DC to the battery compartment of an APC or Belkin UPS box so that AC desk lamps, computers and monitors, and other low power devices can use the converted 12V DC battery to supply AC power to the UPS. . Plug the UPS into a remote controlled wall outlet to return to AC power when the battery is low. The air conditioner uses 3000W pure sine wave inverters, each with #2 parallel copper conductors to protect against power surges while cycling. The 8000W solar panel and 8000Ah marine RV deep cycle battery cover all but the first four burner ranges for the 220V 5200W electric clothes dryer and 220V cooker still running on mains. Since most cheap household appliances (e.g. toasters, blenders, microwave ovens) are made with AC power, and everything that uses DC power sells for 800% more, DC-to-AC conversion will become the norm for the foreseeable future.
If it is only one upgrade, say 30 such city/city block upgrades, a block with its own micro-DC grid can eliminate all inverters in every house except for the micro-grid or macro-grid. Touchpoints that bring together the energy resources of the community and use these resources. for microgrid ancillary services, regional wholesale market resources (FERC 2222), and scheduled DC fast charging for block-electric vehicles. Could this be a step towards energy democracy, a project mentioned in the DOE’s “Energy Barn” concept?
When I built my house in 1990, I used 12-volt lighting – from 12-volt lead-acid batteries and a couple of solar panels. Initially we used 10 watt halogen bulbs and then some 12 volt compact fluorescent bulbs. We are now fully utilizing a 12V LED downlight (and still using the same panel) powered by a 200Ah LiFePO4 battery. As someone mentioned above, it’s great if there are utility outages because all the lighting is available. We have a separate small 12V switchboard to provide isolation from the mains. I think it makes sense to always install LED lighting systems this way. It seems a little pointless to connect the lighting circuit to mains voltage and then install small transformers on all (LED) lights!
If you take the time and money to connect your own domain controller, you will be able to use it additionally. Most people are unaware that you can buy straight 12 ->24 DC refrigerators (not to be confused with the 2 way and 3 way units for motor homes). Most people are unaware that you can buy straight 12 ->24 DC refrigerators (not to be confused with the 2 way and 3 way units for motor homes). Most people don’t know that you can buy DC refrigerators from 12 to 24 (not to be confused with two- and three-way motorhome refrigerators).大多数人不知道您可以直接购买12 -> 24 直流冰箱（不要与房车的2 路和3 路单元混淆）。 12 -> 24 直流冰箱（不要与房车的2 路和3 路单元混淆）。 Большинство людей не знают, что вы можете сразу купить холодильник DC 12 -> 24 (не путать с 2-х и 3-х сторонними холодильниками для жилых автофургонов). What most people don’t know is that you can immediately buy a DC 12 -> 24 refrigerator (not to be confused with 2 or 3 sided RV refrigerators). They are not fancy, the largest I have seen is 16 cubic feet, but you can always use multiple units and they also make DC freezers. There are at least 2 manufacturers whose products are distributed in North America. The only problem is that they draw 5 amps DC while your flashlights draw milliamps. Therefore, large equipment may need to be connected with 8 AWG, 6 AWG, or even 4AWG wire if the line is longer than 55 feet. Fan in the bathroom? Yes, there are blocks for 12 volts. ceiling fan? Yes, 23 volt devices are available. Irrigation or water feature pumps are available in 12 and 24 V DC.
What type of heating/cooling is in this house? If it has a ground source heat pump, I’m surprised it’s not a completely, or almost completely, standalone setup.
By submitting this form, you agree to the use of your data by pv magazine to publish your comments.
Your personal data will only be disclosed or otherwise shared with third parties for spam filtering purposes or as necessary for the maintenance of the website. No other transfer will be made to third parties unless justified by applicable data protection laws or pv is required by law to do so.
You may revoke this consent at any time in the future, in which case your personal data will be deleted immediately. Otherwise, your data will be deleted if the pv log has processed your request or the data storage purpose has been met.
The cookie settings on this website are set to “allow cookies” to give you the best browsing experience. If you continue to use this site without changing your cookie settings or click “Accept” below, you agree to this.