AC power vs. DC power: Both are necessary in our everyday lives and switching between the two causes a great deal of strife in electronics. Why do we need both?
As some of you may or may not know, there was a long standing battle between the two types of power raging back in the 1880s between two giants. The proponents of this war knew that whoever won would determine the future of the power distribution in the United States and possibly the world. In the first corner was Thomas Edison and his company that would eventually become General Electric; Edison wanted the world to run on DC. In the other corner was Westinghouse Corporation, funded by George Westinghouse and led (intellectually) by Nikola Tesla. Westinghouse represented AC power and would be the eventual winner. You can read more about the battle HERE, but I thought it would be interesting to point out that this battle eventually became a political one. Edison even started fighting dirty, secretly funding the invention and use of the first electric chair powered by AC, in order to give some bad press.
AC of course won out over DC as the power distribution of choice, mainly because of the ability to have large generators in a central location and then transmit the power efficiently over power lines to homes and businesses. DC would have required local generators on every street or even every home, which was not possible nor economically viable at the time.
Hang on a second though…a DC generator on every home…sounds familiar…where have I heard about something like this before? Oh right, solar power. However, even more interesting than the fact that solar power produces DC power output is that any kind of storage will have to be in DC. So THAT means if you have any kind of renewable energy resource on your premises (wind, geothermal, any kind of generator which will have an AC output) and it’s not continually supplying power to your home, you will likely need to store it somewhere (assuming you are not selling power back to the power company, which is the case in some areas still and a must in the remote areas). Further, barring any possibility of storing AC power (a huge inductor?), you will need to store that power in DC. So let’s look at a theoretical wind turbine on a theoretical property:
The wind blows –> wind turbine spins –> motor in turbine creates AC power –> AC converted to DC –> DC stored in a battery –> DC converted back to AC when needed –> AC powers devices in a home –> (possibly) AC converted back to DC for use in consumer devices
That’s a lot of steps! Not only are there a multitude of steps to convert wind into air conditioning (heh, the electrical way…the natural way is opening the window), there are lots of places that you will be losing energy to inefficiencies. These occur in the power generation (motors have friction), the storage in the batteries (heat and losses due to chemical impurities in the wet cells), the AC to DC conversion and the DC to AC conversion (both processes lose energy to heat in the electronics). All told, it’s not hard to see why this is not the preferred method of powering ones’ home.
So now the real question: Can we take out some of these steps?
Other articles on this site will deal with improving efficiencies of each of these steps, but the simplest method for improving overall efficiency would be to remove one or more of those steps. The way I see it, one of these ways would be to convert a power scheme in a house. Let’s look at all the ways a DC power system in a house could be beneficial or detrimental to ones’ living situation:
Concerns about DC wall power
- Many devices have different voltages
- This would be a definite issue. Have you ever had to power a guitar pedal board? Random question perhaps, but if you saw what the power strip looks like, you’d catch my drift. Every one of those little electronic devices is too small for a transformer, so they all have AC-DC converters which can power the device with a different required voltage. Now take this idea and expand it to all the doo-dads in your house. I would be willing to guess that there are at LEAST 5 different required DC voltages for all of the normal devices in a home.
- Converting devices
- Conversions would be required from DC->DC instead of AC->DC. A possible solution would be to set up the wall sockets to have selectable DC output (perhaps the home runs on 100V DC and each socket can convert this down to 24V, 12V, 5V, 3V).
- Selling power back to the power supply company
- One of the most popular notions in renewable energy today is the idea of selling your excess power back to the power company, hopefully at a decent rate. Then when your device is not outputting power, you simply switch to grid power and start buying it from the power company. This is great because it does not require battery systems. And while this exercise excludes that option (for people living in the middle of nowhere or with unaccommodating power companies), it would be nice to sell any excess power back to make a small profit.
- Economies of Scale
- This is possibly one of the biggest problems that an all DC power system would face: No one does it yet! All parts would have to be custom made and you couldn’t just call an electrician to come out and fix your stuff.
- This also means that you would have a tough time buying consumer goods. Nearly every device has an AC plug, because that’s what everybody has! Not to mention all of the internal components for AC conversion and occasional power filtering (some devices need very clean DC power). Let’s just say you couldn’t go buy a TV and plug it in…
- Government regulation would also limit any kind of large scale implementation of DC power sockets. It is almost guaranteed that it would require government certifications on many levels to allow manufacturing large enough quantities to bring the cost down for Mr. John Q Everyman.
- Conversion to AC for certain devices
- Motors are the first kind that come to mind. This is basically how Nikola Tesla got started onto AC, proving that it is much more efficient when using AC than DC AND that these motors do not rely on voltage level (DC motors’ speed can be controlled by the voltage applied). This would mean you would either have to convert your DC back to AC to run the vacuum cleaner or you would have to make sure that your DC could supply constant DC and the whopping currents that those kinds of devices use.
- Step up/down transforming
- You know those big garbage can looking things that are attached to power line poles? Those are changing the ridiculously high voltages in the power lines (done for transmission efficiency) down to something that we can use in our houses. Further, these are VERY high efficiency devices. For power in general, you really can’t beat AC-AC conversion; the system proposed here would have to use transistors (note: not transformers) which will have some amount of heat loss associated with them. So even though we wouldn’t be using the AC power from the power company, we would be losing a critical tool in the electrician/electrical engineers’ arsenal, the transformer.
- Leakage currents and phantom power consumption
- No transistor is perfect, they all let just a little bit of current through. The more components in a system or the higher voltage you run at, the more leakage you will tend to have (Ever wonder why electronic devices run out of batteries eventually, even if you don’t use them for a long time?). This would apply to any DC system too and when you don’t have the lights on or anything running, there’s still a chance that the power devices are leaking. This will cut into overall efficiency.
Benefits of using DC instead of AC:
- Higher efficiencies off of battery power
- This point was discussed above, but is THE main point of the article and for going to all this trouble. The less you need to convert between AC and DC, the less energy will go to waste. And if you do need an AC power source, the inverter could be much smaller, in order to handle smaller loads or in order to sell power back to the power company (once the battery is fully charged)
- LED Lighting
- Currently any LED fixture installed in homes requires an AC-DC converter. Using a DC wiring system throughout a home would allow easy installation of LED fixtures and elements (the LEDs themselves)
- No 60 Hz hum
- I’m sure most of you know what this sounds like from a faulty light switch, an older device with poor power supplies or even by sticking a fork in the wall. The native frequency of power coming out of the wall is 60Hz in the US, but varies by region. Either way, this is something that I’ve had to deal with at my job and that all electronics designs have to deal with. With an all DC system there would be other issues such as power filtering and voltage stability… no hum though!
- Shrinking power supplies
- As devices continue to get smaller, the power supplies are reaching a lower limit. 1.8V is currently the lower end of DC supplies for microchips. This allows for less power consumption, as is governed by the formula P = V² * f * C (where P = power, V = voltage, F = frequency and C = capacitance). Have you ever noticed how they stopped increasing the frequency of microchips past a certain point (~3.5 GHz)? Yeah, it was because they started getting so hot you could fry eggs on the processors. Plus mobile processors became much more prevalent. As more and more devices go towards these lower voltages, there will be less need for conversion (or alternately, more need for AC-DC converters if wall power remains as AC).
So the final question comes back to that posed by the giants of the 19th century: AC or DC power? Well, really the answer will be both, as history has shown. Perhaps over time we’ll see a shift back towards DC power as devices continue to shrink and manufacturers don’t want to include bulky transformers or as people hopefully begin producing their own power at home; but one thing that is for certain is this battle will continue raging for a long time and hopefully we’ll help renewable energy find it’s place.
I welcome any and all comments on this idea and if you know of something being developed similarly, please let me know!
“If I have been able to see further than others, it is because I have stood on the shoulders of giants.” ~Sir Isaac Newton
As the "green living" evolution changes our ways of thinking, I just had a few questions/proposals/comments and am looking for some input.
If one were to reduce the living space, for one, wouldn't this make a difference in power drain?
LED lighting is great, I had thought of automobile-type bulbs, in small efficient areas throughout the home, but LED is ALOT more efficient. Thank you!
If one were to use the 12v automotive type plugs throughout the home, for items such as laptops, small dc fans strategically placed for cooling, and other portable type devices used in a more permanent setting, how bad would the power drain be? Also, how bad would dc inverters, like the type that are used in automobiles for powering laptops, drain the system?
Finally, larger appliances such as clothes washers and refrigerators, are there DC options available for these that would be efficient?
Thinking of building an approximately 600-800 sq. ft. vacation home that would be strictly DC powered and these are some questions I have…
Really enjoyed your post…
Alan Sawinski says
Add batteries in your trunk, with a connector, them make an extension cord to run your dc home appliances.
Dear JCT f/ Louisiana, I agree with the idea of reducing converting device AC-DC or DC-AC. Many appliances have DC Port besides the AC one. I hope this steps will be followed by others. Lights & fans could be a start. Washing machine, water pump, water heater, vacuum cleaner I believe will be next, either the cloths become lighter or the water heater can centralized and distributed as services just like water and gas. May be we can hear a lot from device (AC) manufacturer or start a DC blocks to test the idea.
Does anyone else have any experience with this?
You mention the need to convert to AC for appliances, such as vacuum cleaners. Vacuum cleaners are one appliance that have always used AC/DC motors, so they could run directly on 120VDC, except the on/off switch would have to change. In fact, all switches in the house would have to be rated for DC, which is not trivial.
For low voltage devices, I fail to see why conversion from a high voltage DC source is more efficient than from an AC source.
JCT suggests wiring a house with 12V outlets. There is a reason that homes are wired with 120/240V. At 12V, the wires would have to be 10 times the diameter – using 100 times as much copper! Realize that a 1500W hair dryer or toaster would draw 125A ! Even 0000 gauge wire (almost 1/2″ diam) would be too lossy. Or are you suggesting a dual wiring system, with both 12V & 120V circuits?
YES, USB and 110 Volt at every socket. If Im not mistaken USB is 12 Volts Low Amp. so you wouldn’t need a 0000 cable just a USB switch in the basement next to the breaker panel, with fuses in it like ATC style. As far as light are now I think you could use the current wires and switches for you houses lighting using LED’s. In fact Dimmers would work better.
Now Leds tend to be 1.2 volts DC so you step down the voltage with resistors or add enough Leds to use 12 Volts DC. Adjusting the dimmer would lower the voltage. Less heat less energy used. Low Voltage low amperage and if you did a USB socket for your lights you could have wired home automation, in fact USB can be used for Phones, and other things as well like a crude wired home network or intercom system. You I pod could be in the bedroom and you listen to the music on your home theater system.
Just a friendly FYI USB is 5V.
Chris McBrien says
We will never get away from 120V a.c. or 240V a.c. mains electricity depending whether you live in the US or the UK respectvely. ower levels of appliances are just too high….
a) 3kWatt immersion heaters
b) 2kWatt vertical kettles
c) 2kWatt hair driers
The list goes on.
I would however suggest 12Volts or 24Volts for ordinary house lighting. How many cars are there on the roads that use 12Volts, so no shortage of bulbs or storage batteries. How many trucks or aircraft are there that have a 24Volt system. No shotage of lighting equipment.
Storing any form of enery is potentially dangerous, hence Potential Energy.
Hot water storage for domestic housing from Solar Panels is not exactly dangerous. 39 cubic kilometres of water behind the Three Gorges Dam is dangerous, potentially.
Alan Sawinski says
Remember, when the voltage goes down, the current goes Upppppp! Larger wire/cables.
best regards, Alan
Brian Hanrahan says
No one should use an electric immersion in my mind they are old school. Its the first no brain step in reducing your energy needs. DC is not good for electric shower’s but electric shower are a thing of the past for the greener home. If you are to go green the first step is by far a solar thermal system. This step makes it silly to have electric shower. This should be backed up by oil gas or wood with no immersion or electric shower needed.
Can some one tell the guy how designed the washing mes to bring back the hot feed so we can use our solar hot water. Can not buy hot and cold feed washing mes its mad.
This is the low hanging fruit as they say. Once you take this step, then and only then are you in the realm of dc power discussion. If you are considering an immersion you are a few steps behind the pack.
Yes DC has a place for LED seems to be very clear. One DC supply at you main distribution board if you grid ti, would be a good plan i would think.
?? Dose aneone know where you can get 24V pwm 240v ac to 24v dc supper efficient supply 60A around
Ted Martin says
I am going through the misery of finding someone to help me design a 95% dc powered motorhome. None of the solar companies are interested in discussing these possibilities with me… they want to sell gen sets and inverters. The cost of an inverted system is outrageous. I want to use dc in everything – true, it drives up the initial cost, but when you are finished with a quality dc appliance, you still have something to sell. The only people that I can get advise from are the 12vdc alternator people, and their knowledge is usually not too broad. The others are those that prefer to live like hermits. As this nice website does not seem to prohibit emails, I would like to know somewhere I could go to find some advise/consultation on how to set up such a system – even if it costs to get that advise: firstname.lastname@example.org
Alan Sawinski says
My name is Alan
I'm a State licensed Master Electrician, Electrical Contractor and City Electrical Inspector/Plan reviewer…Not bragging just letting you know my overall experience spanning over 40 plus years.
I as wondering how your project is coming, and are you getting any help/advise.
I'm not a green tree hugger, but sure enjoy fooling around with my PV System.
I'm currently converting my PV System into a home powered DC system. To accomplish this I do need the following…
Voltage converters DC to DC up and down (12/48 & 48/12)
Digital meters (LED &LCD) both current & voltage.
Manual transfer switches, etc.
If I can be of assistance, please reply to me at: email@example.com or firstname.lastname@example.org
ps. The National Association of Electrical Inspectors mag. latest edition had an article on converting your house to DC system.
If I do not hear from you, Good Luck with your endeavor !
Best regards… Alan
Alan Sawinski says
Sorry Ted it's email@example.com
Nick Ingvoldstad says
Hey, this is a great post, I like your blog. I'm writing from the CPES at Virginia Tech, I came upon this post while doing some research for this program called the Sustainable Building Initiative. I shared the website with this comment, it's exactly what you've written about, we're designing and developing a showcase home running with DC. The grid will still be the main power source, with solar and wind sources helping to charge home battery storage and an EV battery, if plugged in. The concept is to have two DC buses, a 380V for large appliances (fridge, washer, dryer, etc) and a 48V bus for appliances. Lighting will most likely be a mix of fluorescent and LED, but I'm trying to see if we could use entirely nanocrystal LED. Anyways, just figured I'd comment since you wanted to know of anything similar being developed. If you want to get back to me, send me an email at firstname.lastname@example.org
Sharad Jain says
what is the current status and experience of your project? Is it working ? I am interested in the feed back as I am also working on a grid free residential house project in India.Your response will be much valuable Thanks
Ben Lightner says
I work with a company that builds DC power supply modules as well as other DC products. We are right in the wheelhouse of this article and the projects being mentioned. The company is called Nextek Power Systems and might be worth a poke.
Siddharth Samarth says
How did you go with the project? What system volt you finally went forward with? Are you aware of any regulations wrt 120V DC in India?
Emmanuel Olowosulu says
Nice one. I have been thinking along the same lines myself. Is it ok to reference your post in my work?
Chudamani Ratnam says
I find solar/direct current powered aircons use less than half the power of grid(alternating) current aircons for the same cooling capacity. Why ?
Flemming Frandsen says
I've always supported a standard for low-power, low-voltage supply and connectors.
USB is an obvious choice for everything under 9W, so that's already done, today.
There are a number of gadgets that can't be kept below 9W or are very inefficient at 5V, like laptops, monitors or speakers that still come with huge, ugly power bricks, for those things it would be very beneficial to have a standard that would get rid of all the different bricks and warts under the typical desk.
1) The connectors: One input and One output.
2) Voltage: Unregulated 24V, so anywhere from 20 to 28V is ok.
3) Power: Max 120 Watt per. output, individually limited.
To back the technical specification up the lawmakers should make it illegal to sell devices that don't use either USB or TheNewDCStandard if it uses less than 120Watt.
A great addition to such regulation would be to make it illegal for those devices to come with power supplies as well, because that way we can stop accumulating wallwarts and power bricks and in stead buy one large, efficient, desk-mounted DC supply.
Great… I’d love to see you try to run your clothes dryer off something like that.
diy home solar says
Great in-depth article. While there is a possibility to sell electricity back to the power company, not many of them are so accommodating. And also there are some regulations against doing it. AC and DC are completely different, each has its place. How could you possibly power integrated digital devices with AC without inverting it into DC.
I really hope DC gadget makers standardize on a plug such as mini or micro USB and we have them in the wall. When all lighting is LED then the only need for AC is for appliances. One issue I have on a minor point is that transistors can’t drain batteries when disconnected by the power switch. I think it is a chemical issue.
The transformer argument is lame and doesn't amount to anything in a world where such devices would not be required.
Tad Sehorn says
glad to be one of many visitors on this awe inspiring site : D. Consider a visit to my webpage anytime. :D..
Transmission will always be AC unless there is a *HUGE* infrastructure change. Generators naturally produce AC power, it is converted to DC using brushes. Very few places in the world use HVDC transmission as the infrastructure required is very different. Thus, the power coming to a house will always be AC. Inverters/rectifiers account for approximately 95% of AC/DC conversion inefficiencies. Smaller inverters are less efficient compared to larger inverters. A single 50kW inverter at the house level will be vastly more efficient than the hundreds of small inverters in every electronic piece of equipment in a household.
Any idea on 125 v dc as a system voltage? led lights, ceiling fans designed for 125 vdc. and other electronic appliances like a mobile charger, led tv, laptops, printers, etc etc designed to work on 240 v ac, work normally with 125 v dc, the brick interface between the wall socket and the appliance handing this conversion, and very efficiently too!!! a laptop eating 80 watt on 240 v ac consumes just 20 watt when fed with 125 v dc.
try this and you have a win win situation.
those appliances with a motor like a blender, washing machines etc are alone fed thro an inverter, a very small one for each appliance, and switched on on when needed, thus minimizing conversion losses.
You would not need inverters for appliances. If the appliances are AC and the supply is DC, you would need rectifiers. Their inefficiency is primarily from the voltage drop across diodes, thus heat and wattage. If the appliances and supply are both designed as a new DC system of say 48VDC (my recommendation, with those few larger appliances receiving dedicated wiring anyway), you would need nothing between them.
Great article. I think its time to move part of our houses to dc and have designed the dc stand dcstand.com
Gary Reeves says
Looking to design a new house in the Philippines to be self sufficient on power by going 75-90% DC on a solar and alternative power system. I look forward to designing and seeing how this works out. The design of the house will be with insulated concrete to reduce heating which is not much in a tropical island but cooling by natural air flow and insulation by the concrete, and DC powered ceiling fans. All lighting will be DC and controlled by automation along with the power source and consumption.
Ben Lightner says
I’m wondering how your design is coming along and am curious as to what avenues you are planning on taking. I work with Nextek Power Systems out of Detroit and we are very involved in projects such as yours. I’m not going to throw you a pitch but rather am interested in what kind of designs and companies you are working through to accomplish your house. I’m glad to see people are utilizing DC in homes!
If you are interested in poking around, here is a link to our site (it is shakily organized, but I think you will be interested as we build DC power systems and lighting solutions!)
In Germany we already have combined 220V AC and 5 DC (via USB) as a dual power outlet.
Look here: http://www.elektroversand-schmidt.de/images/bj_20EUCBUSB-24G.jpg
There’s no AC-DC converter (= transformer + rectifier + 5V voltage regulator) built in every single outlet (that wouldn’t make sense as in fact it would be the same as an external wall wart, just flush-mounted). Instead a single bigger converter acting as a main DC distributor for the entire home will be installed at a central location within the house (cellar, attic, …).
This is neither state-subsidized nor an obligatory law, but simply a voluntary and very comfortable way of powering those 1000’s of little gadgets lying around in our houses.
Unfortunately it’s about control. if DC were to become the resource of Choice. Power Companies would lose control of Profits and Money. and They would be so willing to do that.
Wrong. Power distribution via DC is not feasible.
Alo Pexoma says
Wrong. Power distribution via DC is being looked into from a national standpoint, as it is much better suited to long distance power transmission. The AC power grid is one of the reasons we have no national power grid(only regional grids) in the US as of now. A DC power transmission grid would be capable of long range transmission without significant losses, allowing the US power grid to be optimized from a national standpoint.
So true, it is both corporate and government control of person and taxes. Once you can look after yourself, you no longer need to fund their corruption. They will try and fight it!!!
Peter Nichols says
Thank to the Chinese, there are now an increasing range of 12VDC appliances including 12VDC Edison LED bulbs available at a lower cost than the AC equivalent. Most laptop manufacturers sell the 12V Cig lighter adapter. You can buy 12VDC -> 5VDC for a dollar, opening up the whole world of USB powered items. Sure,there is still not much to choose from in hair dryers, fridges and washing machines, but there is almost no reason why we can’t all enjoy DC lighting, DC phone communications and direct DC power for laptops straight from solar.
Many thanks Peter, Your info was very informative and living in Oz we really need to consider different solutions, regards Stuart
joe cole says
Are there any magazines or pub on d/c system I want to convert my house a trailer and become grid free
Hello, I’m not sure if someone pointed this out already, but your link to war of currents (wikipedia) is not working! 😀 Try adding http:// when linking.
Link is pointing to http://chrisgammell.com/can-dc-power-an-entire-home/en.wikipedia.org/wiki/War_of_Currents
Browser: Firefox 24.0, Windows 7
Also, thank you very very much for your explanation on op-amps! 😀 I’m struggling with my topics but you did a great explanation.
Óscar Andrés Berrío says
Hello everybody, I’m Óscar Berrío from Colombia
I’m currently doing my undergraduate work (in electrical engineering) in DC housing design, and I need information about DC Voltage Regulation and standards about this kind of systems.
Would be great if someone can give me a hand in that, recommending me books, papers or giving me information.
Thank you very much
My email is:
Paul Héroux says
I have written a 6-page article on why we should convert all of the electrical grid and systems to DC.
It can be found at http://www.invitroplus.mcgill.ca/AC to DC transition.pdf
What about having small clusters of solar houses running totally on DC and attached to a small local grid with a central station that has batteries or capacitors for storing energy?
Paul Héroux says
You would need a network at a reasonably high voltage (say, 350 V) to avoid having a grid with large wires.
rupesh pradhan says
hey thanks for ur blog it is like a great support for my current project at home..well am trying to convert allmy home wiring to both ac 230v and dc 12 volts…230 for home electronics like fridge, hair dryer,etc and 12 volt dc for 12 volt dc…..am about to start it with my new home plz suggest me….
Herman Shim says
Hello Chris, well thought out. May I suggest the answer lies in the challenges you have identified. The institution I am affiliated with has committed to investing in the research necessary to test this very question AC or DC, Edison/ Tesla(My Giant shoulder). Let me know if you would be interested in joining us. Have a read of Mr. Moshe Kinn’s paper and Capacitive Power Takeoff Technology.
Very Best Regards,
One would think that if auto can run from electricity, perhaps major appliances like washing machines, dryers, and certainly many light fixures could too. Better sustainable appliances than blackouts, or brownouts? Perhaps better than storm electrical lines down?
Further, refining that principle could bring lighting and appliances to even the most remote places on earth without having to duplicate the excessive energy methods created in the U.S. when wasteful energy was the norm.
Paul Heroux says
AC power is a remnant of the past, when transformers were the only method of increasing and decreasing voltages without energy loss. We now have power semi-conductors that do this in high voltage networks. The only reason why we still have ac domestic consumption is habit.
Wrong. Power distribution using DC is not feasible.
But the premise here is distribution is no longer necessary with the availability of inexpensive solar and other technologies.
Why not just have two separate channels? regular 120v AC line directly from the pole, and then a separate DC 12v channel alongside that.
Mike Mccormack says
Grounding, notice they keep the 48VDC telephone wires way down below from the AC voltage. Second problem is DC looses transmission ability over distance due to wire resistance. Best way to do it is everyone would have a small scale DC power source for small appliances and AC for high current appliances, even better use natural gas as a heat source and backup generator fuel.
Why this world is not running with DC.I think DC is more efficient.
There are many solutions from the marine industry; refrigeration, breaker panels, lighting, appliances… These things tend not to be cheap, I suppose because of economies of scale, but I suppose it would still be worth it to avoid the power losses in conversion and to keep the generation and storage capacity of a PV system down. I like the idea of a total DC LED lighting system and distributed low voltage DC along with AC for high power appliances. You can also avoid many high power appliances with a little thought. We have a manual espresso press for making coffee, you heat the water on a gas/propane/wood stove to avoid the AC water heating. One example.
Talk to a live-aboard sailor about how they get along and you will find a practical power solutions.
lokesh kumar says
sir, if dc is more efficient why cant we use direct current from the solar pannel directly to dc loads like tv..
lokesh kumar says
sir i am b.tech final year student,i had an idea to work the tv on direct current produced by a solar pannel by eliminating the inverter.Is it possible? if not why?
So now its 8 years on….
Whats the tech development done?
Dc looking a better idea I believe
Hi Chris, I have been living off solar and direct DC for 5 going on 6 years now off grid. I still do have one ac device and power tools but as they break I will replace them with DC. You can buy off the shelf, a 24v dc washing machine, mine is still 240vac with inverter. That is my only ac device. Vacuum 19v dc is a rechargeable one, 12v led lights, 12v water pump, I have converted my 42 inch TV and 32 to 12v actually 5v to 36v but i run on 12v. Cost $15 each TV to convert. 12v pedistal fan, 12v heated blanket. For fun I have now successfully run a 125 litre 120v DC electric hot water system for over a year. Hoping to drop it down to 60 or 48 volts in the next month or two. Currently heat it to 84 degrees Celsius each day, arduino controlled, and is usually there by 11am. But made it through winter fine and just coming into our second winter. I’m in Brisbane Australia. In the suburbs. Not in the bush. Our biggest problem is the lack of 12v appliances. I believe 48v for kitchen and laundry and heavy usage appliences. I’m building a 48v induction cooktop at the moment. Currently using gas cooktop and oven which is far cheaper, but we all have to have hobbies. I spend my money on achieving 100% elv DC. Battery are lifepo4 winston batteries and I highly recommend that you use these over lead. 2 more days and I can guarantee you will get 5 years at minimum. I have been told 15 to 20 years but I have my doubts. I’m using a 90ah lifepo4 and it runs my 360 litre fridge fine, 24/7. I have a 188 litre 12v DC chest freezer too. So it is possible just a little hard as it is not main street yet. Electrically it has cost around $5000 AUD. Solar panels, batteries and wiring and breakers. And no bill ever again!! But it does still cost for new batteries etc, so it is not free. Still costs around $7 a week. But way cheaper than being on grid!!!! And DC is a much cheaper way to go. No microwave yet, an inverter microwave is lower peak power, but once the freescale one comes out that should be easy to convert or at least much lower power usage. Who knows they may release a DC one. But it is 100% possible, just hard at the moment. It will take corporate change to make it happen, making direct DC appliences in mass quantities. They will have to take the lead.
Why would you want to reduce voltages? Also this entire page is so full of nonsense, anything that’s resistive, has a universal motor or switching power suppy will work on either AC or DC or any number or hz in between it simply doesn’t matter that include LEDs, TVs, Computers, Vacuum Cleaners and a whole lot more for the few things that you can’t run on DC then you get use an inverter for that, i really don’t understand why so much misinformation online, and the higher the voltage the better efficiency you get thinner wire less running costs why would anyone try to reduce voltages everyone should be running at least 240V if it was up to me everyone would be running delta 415 with 240v potentials just as safe as 240v and a lot more efficient.
Kevin Kangas says
Staying with DC over short distances for low power applications saves you the power loss in converting from your DC power supply to AC. This is the same reason your car is all DC. When you store in DC you don’t want to lose 20-30% just to go to AC.
Just came across this site after 8 yesrs… I guess…. The main advantage of AC is the use of a simple” transformer to step the voltige up and down easily and cheaply. Yes the induction/slip ring motor did “get rid” of the “sparking brushes” in the rotors.
This ability to step up and down the voltage was ultimately the “clincher” for AC over DC. actually DC Transmission is much better when you have to transmit power above about 500 miles, without any loads in thd middle… to step it down. The Trans-Sibetisn 100km+ lines in Siberia utilized DC only.
However….. when “decentralized” generation and captive domestic and even commercial loads are concerned….. DC woul again havd been preferred… but most vendors do not support DC equipment at this level of the distribution system.
I am looking at a large 2500KVA PV solar greenhouse…. which has 8000+ PV Panels on the roof and about 15,000 light fixtures below.
I would like to use the SAME Bus Distribution system for…. BOTH to feed in and extract
electricity…and keep the voltage as high as possible (600VDC…???) to maximize the power transfer…..
However…. I cannot seem to find anything for this voltage…except of course switchgear, fuses,buses, etc…
I am thinking of using a number of LED’s in series at this voltage…. but not sure if vendors will support me…. rven for such a large requirement…. any ideas out there…. because most power distribution equipment is tested to 600V but not sure about these LED’s…
Most illuminating! But you haven’t plugged fuel cells into your equation. Could be a game-changer. You may argue that after
~175 years they still offer as much unachieved promise as when Grove invented them, notwithstanding that Moon-exploration and many space applications can only choose between plutonium or fuel cells with banks of stored gases. [Just how do they power the ISS? Do they have dual ac & dc supplies?]
There are patents in the literature and masses more unpublished IPR for domestic (dispersed) FC generators. Some clever engineers even envisage the FC car will supply, rather than consume, electric power in the home – ideal when the house is empty all day and buzzing with amps prior to householders leaving for work and returning home. CHP based hot FCs have also been designed to solve the heating issue (British Gas and a Uni. offshoot have also demonstrated a complete plant.
All this is a long way from the Edison-Westinghouse fiasco (which was not, incidentally, a US competition – it was a Czech-Scottish argument initially, but we know how our country cousins enjoy rewriting history!) All parties should’ve recognised the importance of Grove’s discovery since he preceded them all and also worked at the RI with, inter alia Faraday himself.
Addendum: The Post Office Tower (before the IRA blew it up) was originally fitted with huge copper busbars running centrally, vertically to enable equipment to run off a centralised d.c. supply. [I learnt this from an engineer who was personally involved in its installation.] Within a very short period it was replaced by regular a.c. wiring; apparently the iR drops, even in such a closely wired installation, were unacceptably high. It was kept fairly quiet at that time (’60’s) as the Post Office was still publicly owned and large sums of tax revenues were required for the retrofit.