A DC-based culture is growing.

Get a professional CEng jounalist to write this sort of thing instead of an 'ologist on a deadline. Rubbish with opinion delivered as facts is bad in a trade mag. Going from random peformance parameters about low power DC devices and LED s to conclusions abot the national grid with nothing in between is appalling scientific discipline

H+S note - Any significant DC voltage can be lethal versus AC, you can't let go of relatively low voltage DC. 200Volts can easilly kill. Ask anyone who has built higher voltage DC equipment (me for a start). Or lost relatives in the pre war years when DC mains were still available (me again).

DC is no good as a transmission backbone nor for most domestic appliances requiring higher voltage to get the power required down sensible sized wires.

Do we really want to put in AC/DC converters just for our lights?

We need 1200 Lumen lights anyway, not 100. And again there is the dish washer, cooker, Clothes washer, tumble drier, room heater, and in future car charger, etc. AND we need the high power for industrial applications where the ease of distribution and relocation makes it the preferred power source.

Lighting is low power, while making up a good percentage of night time power consumption its bog all of the daytime peak grid loads.

Get educated in the subject first, then research and get the whole picture in context next, THEN do the writing bit. Articles predicting the future based on manufacturers press releases written by a PR girl with an 'ology degree are a bad idea. IMO

Brian Catt
01932 772731

Posted by Brian Catt on Jul 9, 2007 1:13 PM

Brian Catt said:

Get a professional CEng jounalist to write this sort of thing instead of an 'ologist on a deadline.
Thanks for answering my post. You would better check your spelling. This blog is free entry, not for professionals. True enough, I am not a journalist; I am just an electrical engineer bachelor with a master in computer science, and I am not on a deadline. Forgive me if I did not write enough. It was for the sake of discussion and shortness that I left off a lengthy justification of each statement. This is my opinion based on observed facts.

H+S note - Any significant DC voltage can be lethal versus AC, you can't let go of relatively low voltage DC.
Clarification: I talk about low voltage DC (up to 28 volts approximately), never about high voltage. That is the point I want to make. High voltage was the tradeoff taken by AC advocates to reduce the cross section of conductors, which was quite right at the time; no question about that.

DC is no good as a transmission backbone nor for most domestic appliances requiring higher voltage to get the power required down sensible sized wires.
Precisely. There will be a transition period when many applications will still require AC, but DC applications will grow faster now due to the illumination issue. DC applications are those that do not depend on wiring, which is very expensive, bulky, and heavy. That is going to decrease gradually.

Do we really want to put in AC/DC converters just for our lights?
No. We will use portable lamps on small batteries (NiMH, Li-ion, whatever more efficient) with enough light flux to compete with incandescent and CFLs. No rectifying power supplies any more; they are bulky and inneficient. DC culture.

We need 1200 Lumen lights anyway, not 100.
In Canada they have practical experimentation on road lighting: check out the April issue of LEDs Magazine, which you can reach online at no charge. Their preliminary conclusion is that cool white LEDs favor night vision more than warm white HPS lamps with much higher flux. The only hurdles for LEDs are initial cost and standards; all else is favorable.
And again there is the dish washer, cooker, Clothes washer, tumble drier, room heater, and in future car charger, etc. AND we need the high power for industrial applications where the ease of distribution and relocation makes it the preferred power source.
I agree. That is why temporarily we will have to put up with the power grid. We live in a culture where engineers are trained to take certain things for granted. Once one starts thinking differently, solutions will be proposed. For example, I just learned that a set of 10 AA-size NiMH batteries can store more than 18 Ah of energy and that you can spend 80% of that charge without a significant voltage loss. And these batteries can be recharged 500 to 1000 times without having to wait until empty like the NiCd batteries (no memory effect). An acid-lead battery with 18 Ah rating weighs several kilograms, while the NiMH batteries just 270 grams! There are improved Li-ion batteries with higher energy density that are being used on the Prius hybrid car, which has a kilowatt level DC motor. So, higher power applications are within the scope of the DC technology existing today. If you need high-voltage, just use an oscillator and a power MOSFET followed by a high frequenty transformer. Fascinating new things became available since I left engineering school. Enjoy them.
Lighting is low power, while making up a good percentage of night time power consumption its bog all of the daytime peak grid loads.
Take a look at the June issue of LEDs Magazine. I was amazed at the things I didn't know anything about a week ago. It is a serious paradigm shift taking place. The major hurdle now is to overcome the deeply ingrained AC culture.

Get educated in the subject first, then research and get the whole picture in context next, THEN do the writing bit. Articles predicting the future based on manufacturers press releases written by a PR girl with an 'ology degree are a bad idea. IMO
As I said, my objective is to put the idea in discussion. Learning is my favorite hobby. Knowledgeable people like you enhance and validate my topic. Thank you for the criticism, and please, let us chop and slice the ideas, until we learn a lot of things as we go. Other readers will appreciate that.
What motivated this article was that lighting is an extreme human necessity which is noticeable when one is deprived of it; in the dark, one cannot even think straight. Did you ever read a story by Isaac Asimov, his first publication, Nightfall? It is very entertaining, and makes you wonder if...

Updated by mariomiy on Jul 9, 2007 8:53 PM

Wow, great debate. Thank you guys!
Keep it going.

@Brian, if you want to see some cool LED videos visit our blog www.tecartex.info I hope you enjoy it.

AC

Posted by Tecartex.com on Jul 10, 2007 12:00 AM

Take a look at this demonstration:
http://br.youtube.com/watch?v=nkDPOER1Qe8

I built a 3-superLED lamp prototype, which I imagined would be bright, but reality surpassed my expectations.
The people in the LED illumination industry is really advanced, and confirm the point of my blog: they tilt the balance toward a DC culture.
The set of LEDs shown in my video consume a total of about 7 watts and the light flux seen is about 400 lumens (about 60 lumens/watt), because my power supply could not reach the 12 volts maximum of my design.
Those LEDs are supposed to operate at 700 mA, but can reach 1000 mA peak, although with lower efficiency. Next I will build a prototype that repeats the demo out of 4 AA-size NiMH batteries, which will last about 8 hours delivering 700 mA. That is something I am curious to see, and I will not be surprised if my expectations are once again surpassed. I will report in this blog.

Posted by mariomiy on Jul 12, 2007 2:43 AM

AC/DC?

Me again. The subect I read and replied to was about the end of the grid and distribution going DC, not just LED lights. No it won't. BTW as a 30 year Member of the UK IEE and a Physicist I do understand this a tiny bit as well.

I'm not disinterested in LED lights and Li Ion batteries for consumer devices. But not in battery power for real fixed applications like domestic lighting, appliances and factory machinery where the real demand is.

BTW A flashlight is a device for storing flat batteries, according to even flier and sailor wisdom

I recently read in a feature on LED progress in IEE news which also said what I said already. Current LED lights have good specific outputs but cost per lumen per hour of life is aeons away from being economic, and anyway we are only just now seriously migrating to low energy bulbs after 10 years of their availability - on existing electrical infra structure. Maybe my grandchildren will LED lights in their cars , boats, planes, but I won't.

I'm sure for local applications in inaccessible places, mobile applications as in motor homes and even more so inflight illumination where low voltage DC power is available already, is the power source of choice and can be used directly and batteries are justified/normal then LEDs will find applications where their cost is less of an issue.

And of course for the lighting on the Enterprise, geek gadets , mobile phones, and other non essential toys DC from Lithium Ion batteries is great - but they will still need an AC charger.

As already discussed the grid will not go DC and will be around indefinitely on AC for bulk utility power delivery for basic electrical engineering reasons. That is my point.

BTW any sort of serious power transmited by wirelesss is a REALLY bad idea, it fries you and H+S won't like that. But if you have a cabin in Oregon powered this way and fry your vital organs no one will mind. You should be well done by the time they find you and make a good dinner. We can have your liver with a nice Margaux. The Arabs can have the eyeballs. Seriously I have a LAN at home and all my wireless connections are turned OFF there. I have children and anyway care about my own eyes. I do use WiFi on the road when mobile, NOT when its not needed in office or home. I spent 7 years working for the UK NRPB including on the hazards of microwaves ..... no thanks.

For delivering power to millions or at least 100's of thousands of people who have a variety of high power requirements, and even for delivering the aggregate low power lighting demands of a town you still need a LOT of power - and an AC grid is essential to effective power distribution at that level.

As you know it HAS to be high voltage to reduce the current to something manageable in terms of conductor size, especially in developing and third world countries still using overhead cables. It has to be AC for transformability and safety. Its AC for a reason - it was a much better electrical engineering solution.

You can transform AC down at highish efficiency to non lethal voltages but not DC. DC Inverters are HORRIBLY inneficient BTW. Batteries are expensive and not necessary if you deliver AC to the point of use, the whole point of AC distribution network is you don't need multiple local storage or generation systems, that's the point of the grid, to manage real time power creation and delivery as cost effectively as possible.

Really you are talking about low power specialist LED lighting applications and gadgets, and I am talkng about mass utility power delivery via the National Grid, what most people use and something DC does not do in any safe or cost effective way at the levels of demand modern towns and cities demand.

Maybe this anti grid thing is because you are in a country with a rubbish grid? Not sure what kind of grid you have but ours never browns out or fails, and we have pumped storeage buffer systems and exchange power with the French who have Nuclear power and different peak times. No problem to solve.

Just FYI the simple electrical losses of AC (dielectric) versus DC (resistive) in transmission at its generated voltage mean DC is best on this one critera. However it can't be transformed effectively and still needs to be high voltage to keep the current and conductor size down - so there are very few uses of HVDC. One under the English channel. The dielectric losses associated with AC underwater increase due to the capacitance effect of the water between the conductors and this makes DC superior. There is a good list of other DC links such as New Zealand North and South Island where DC can be used for special requirements on Wikipedia. Some systems send DC and AC down the same transmission lines to optimise power delivery.
But for the bulk of normal applications its "AC for ever!"

And if you want a real experience and understanding of what serious power generation is about go to modern power station where they are using 660MW generating sets. Not only are the turbines HUGE but the infra sound they generate in the turbine hall is totally unreal. And its powering millions of low energy light bulbs, amongst other stuff.

Brian

Posted by Brian Catt on Jul 13, 2007 8:32 PM

[...] BTW as a 30 year Member of the UK IEE and a Physicist I do understand this a tiny bit as well.
So I can argue with scientific ideas properly.

I'm not disinterested in LED lights and Li Ion batteries for consumer devices. But not in battery power for real fixed applications like domestic lighting, appliances and factory machinery where the real demand is.
I thought so a few weeks ago. There has been a dramatic improvement in batteries that make them serious components for the electrical industry. In the recent past only lead-acid batteries were able to dispense tens of amperes to feed a starting motor. Now the NiMH and Li-ion can do the same from a smaller size and weight. Li-ion batteries are too expensive yet, but the NiMH are sold at reasonable prices. A set of 4 NiMH AA-size batteries of 2.5 Ah each can maintain 4.8 volts during 80% of their rated discharge time, which at 1 ampère steadily would be 8 hours. Their weight is about 100 g (3 oz). They can be recharged 500 to 1000 times and can last longer than the Li-ion batteries--more than 2 years.
People grew accustomed to lighting the entire house brightly and omnidirectionally because they could. Now with higher power bills, many people are switching off the lights every time they leave a room. Those who don't have a solid electrical infrastructure would be satisfied if they could have a white light similar to daylight on their table to study or work at night, and leave the walls and the ceiling in relative obscurity. That is what LEDs do offer nowadays.
There is a kind of DC motors that has been used for special low power applications (printers, positioning equipment for industrial operations, laboratories): the step motors. These, unlike the explosion engines and AC or DC motors which attain their maximum torque at high rotation rates, have the peculiarity of maximum torque at zero velocity (known as hold torque). If we build one with enough power (> 200W) and mount it directly to the wheel of a vehicle, it will be able to start moving as soon as it receives pulses of current in its coils. They can give small kicks of 1.8 degrees angle and soon attain reasonable speed. If the outer diameter of the traction wheel is 40 cm (15 3/4in) the vehicle's speed at 1000 rpm would be 75 km/h (47 mph) which is reasonable in the urban occupations. Some research is required with the use of a microprocessor to send the necessary pulses to start, stop, accelerate and decelerate hybrid step motors, and we could use one motor for each wheel independently controlled so that curves, ABS, battery charging when braking or coasting, are handled. Step motors have no brushes to spark, no need of gears, they are a whole new kind of game, helped by their inherent characteristics. The same idea is applicable to industrial machinery, without pulleys or gears--direct coupling--fed by batteries charged under the sun.

BTW A flashlight is a device for storing flat batteries, according to even flier and sailor wisdom
I did not understand this witty observation.

I recently read in a feature on LED progress in IEE news which also said what I said already. Current LED lights have good specific outputs but cost per lumen per hour of life is aeons away from being economic, and anyway we are only just now seriously migrating to low energy bulbs after 10 years of their availability - on existing electrical infra structure. Maybe my grandchildren will LED lights in their cars , boats, planes, but I won't.
I displayed a lamp built with two cool-white superLEDs with the nominal flux of 150 lumens each at 3.5 volts and 700 mA. My family and friends agreed that the device, placed in the middle of the 2.7 x 2.0 x 2.7m (8.86 x 6.56 x 8.86 ft) room at the height of 1.8m (6 ft) illuminates comfortably a work | study table of 70cm (27.6in) height. There is a 15-watt CFL in the same room that lights all walls and ceiling with similar brightness but the table top not so well as my LED lamp. A LED lamp concentrates its light on a smaller area than CFLs, but does not leave the remainder in total obscurity like flashlights do. The efficiency of the 2 LEDs is 300/(7 x 0.7) = 61 lm/W, comparable to the CFL. But I use a pulse width modulator which, at about 50% duty cycle, causes the same visual perception as at 100%. That increases the efficiency to 120 lm/W, much better than the CFL. I went to bed leaving the PWM at minimum lighting, which produced a bluish-white, soft spread like a bright moonlight, drawing a very small current from the power supply. I will make better measurements with an oscilloscope later, which I don't have now. With the dimmer, the same device used to study or work can be used in a child's bedroom to avoid total darkness.
The LEDs will cost around US$4 each in quantity, and NiMH batteries about US$2 each, so the final price to the consumer will be around $30, which is not bad if it lasts 20 years with careful usage. The batteries should last around 5 years. For efficiency and price, I think LED lamps have already beaten CFLs and the infrastructure they require (AC power grid).
The batteries can be recharged in one day with a solar panel of about 500 cm² (0.54 ft²) which would cost about US$50.

I'm sure for local applications in inaccessible places, mobile applications as in motor homes and even more so inflight illumination where low voltage DC power is available already, is the power source of choice and can be used directly and batteries are justified/normal then LEDs will find applications where their cost is less of an issue.
Cost is no longer an issue. See above.

And of course for the lighting on the Enterprise, geek gadets , mobile phones, and other non essential toys DC from Lithium Ion batteries is great - but they will still need an AC charger.
No, they can be recharged by a solar panel. AC converters are inneficient.

As already discussed the grid will not go DC and will be around indefinitely on AC for bulk utility power delivery for basic electrical engineering reasons. That is my point.
This statement sounds more like a politician's than a scientist's. Prejudicial and reeking of vested interest. My contention is derived from basic electrical engineering reasons, too. If there was a possibility of building affordable local DC generators in the 19th century, Edison would have won in his contention with Westinghouse, and we would have a DC culture ever since.

BTW any sort of serious power transmited by wirelesss is a REALLY bad idea, it fries you and H+S won't like that. [...] I spent 7 years working for the UK NRPB including on the hazards of microwaves ..... no thanks.
I did not talk about wireless power transmission. Wimax transmits very low power gigahertz packets which do not harm any living being.

For delivering power to millions or at least 100's of thousands of people who have a variety of high power requirements, and even for delivering the aggregate low power lighting demands of a town you still need a LOT of power - and an AC grid is essential to effective power distribution at that level.
It will require one or two generations for the current advanced countries to change their expensive energy-consuming habits. When costs are higher, alternative methods become the norm. Transmission of power through an AC grid can be replaced by local generation of DC power, without a grid. For the countries that have poor AC infrastructure or none, it is natural. Your statement is like the Windows users saying that Microsoft is essential for computing just because all they know about computing is from there and they invested a lot already in Windows to migrate into GNU/Linux.

As you know it HAS to be high voltage to reduce the current to something manageable in terms of conductor size, especially in developing and third world countries still using overhead cables. It has to be AC for transformability and safety. Its AC for a reason - it was a much better electrical engineering solution.
No, it does not have to be high voltage, if energy is not to be transmitted over long distances. DC energy is captured from the sun and stored in batteries. AC energy installed capacity is not always used, and if there is a transmission line failure, a blackout ensues. DC users have more freedom and less risk in their everyday life.

You can transform AC down at highish efficiency to non lethal voltages but not DC. DC Inverters are HORRIBLY inneficient BTW. Batteries are expensive and not necessary if you deliver AC to the point of use, the whole point of AC distribution network is you don't need multiple local storage or generation systems, that's the point of the grid, to manage real time power creation and delivery as cost effectively as possible.
Batteries store energy at low voltages. If higher voltages are required for any reason, they can be generated efficiently at high frequencies by low-loss transformers (ferrite core) and MOSFET transistors, which are quasi-perfect switches. Batteries are no longer so expensive and bulky as before and are a better tradeoff to an AC generator with excess installed capacity that add unnecessarily to the power bills.

Really you are talking about low power specialist LED lighting applications and gadgets, and I am talkng about mass utility power delivery via the National Grid, what most people use and something DC does not do in any safe or cost effective way at the levels of demand modern towns and cities demand.
If you thought as a scientist, you would never say such a thing. The situation today is a consequence of past circumstances that no longer hold true.

Maybe this anti grid thing is because you are in a country with a rubbish grid? Not sure what kind of grid you have but ours never browns out or fails, and we have pumped storeage buffer systems and exchange power with the French who have Nuclear power and different peak times. No problem to solve.
No. Brazilian engineers are pretty good. Greedy politicians do all they can to become rich in a few years, so the power bills go up without a corresponding improvement in services. If you have good engineers who understand the tradeoffs, then the UK is a good candidate to gradually adjust to a DC culture. The regions without AC culture will be forced to show the way, so the others will eventually follow. The reason is sheer cost.

Just FYI the simple electrical losses of AC (dielectric) versus DC (resistive) in transmission at its generated voltage mean DC is best on this one critera. [...]
But for the bulk of normal applications its "AC for ever!"
You have a notion that DC has positive properties, so not everything is lost. Your last flat statement is inconsistent with a wise mind.

And if you want a real experience and understanding of what serious power generation is about go to modern power station where they are using 660MW generating sets. Not only are the turbines HUGE but the infra sound they generate in the turbine hall is totally unreal. And its powering millions of low energy light bulbs, amongst other stuff.
I worked at a para-government power plant builder, Eletronorte, for a few years; huge hydroelectrical plants near the Amazon region. I am familiar with large generators. You get more out of 66,000 100-watt solar panels, and more reliable service. No need to wire the entire house.

Posted by mariomiy on Jul 23, 2007 5:28 AM

From the July edition of LEDs Magazine:

The Lumileds announcement shows that developments in the power LED segment are keeping pace with standard LEDs.
The white LEDs developed by Lumileds' Advanced Labs are built around 1x1 mm2 chips. The devices delivered 136 lm when driven with a current of 350 mA, corresponding to an efficacy of 115 lm/W. Lumileds emphasizes the correlated color temperature (CCT) of 4685K, which is significantly lower than values typically reported.

Equally impressively, at 2000 mA the white LEDs delivered 502 lm, corresponding to an efficacy of 61 lm/W. Lumileds says that it achieved these record results for white LEDs by combining several new and innovative technologies, including breakthroughs in epitaxy, device physics, phosphors, and packaging technologies.

These new LEDs are clearly superior to any CFL in terms of light quality and efficacy. With production in large numbers, the prices, already affordable, will come down, too.

Posted by mariomiy on Jul 23, 2007 12:38 PM

Well, looks like Sir Brian Catt considers my poor fact analyses below his dignity to respond. And there were no comments from anyone else. Perhaps nobody is reading this blog. Anyway...

Here are a few more signs that DC culture is up and running.

Electric Plane - Oshkosh - Sonnex Aircraft
http://news.com.com/2300-11397_3-6198783.html?tag=ne.gall.latest This one will run on Li-ion batteries. From the description, it uses a stepper motor.

Electric scooter reaches 50 mph in 6.8 seconds
http://news.com.com/Electric+scooter+to+charge+into+U.S./2100-11389_3-6184216.html?tag=item
This one runs on NiMH batteries. Must be a stepper motor because it uses direct transmission, indicating a high initial torque.

Eletric tricycle runs on sealed lead acid battery - brushless motor
http://www.made-in-china.com/showroom/xinguangbike/product-detailrMqEJDhusAWo/China-Electric-Tricycle-Ambulant-Shoppe-XG-304-.html
Probably is a stepper, because they say "brushless motor". It would improve with NiMH batteries, though.

Electric car outruns a Porsche. Wrightspeed X1
http://news.com.com/1606-2-6196906.html?tag=st.rb
Probably a regular DC motor, due to the high speed and the high torque at higher rpm.

BTW, my efficient one-white-superLED lamp model is being demonstrated successfully right now. My 3-year-old granddaughter loves it. It has a very simple but efficient dimmer, an invention of mine.

Updated by mariomiy on Aug 4, 2007 9:44 AM

Just wanted to poke in my tuppence worth if I may. I don't have any degrees, ologies or other little bits of paper to wave at people - but I do spend a bit of my time helping those who DO have them solve problems - funny world eh?

The part about "better check your spelling" - well although everyone is entitled to an opinion, I would rather read a document that is factually correct and balanced - with the odd typo - rather than a perfectly checked document which nonethless, doesn't quite know what it is talking about. "You would better check your spelling" - not sure if that wins any prizes for grammar you know.....

Now, first off, while I agree with Brian C on the point of not replacing the grid, it IS interesting to note that things have moved on a bit since the original AC - v - DC debate with elephants being killed to try and terrify people about AC. One of the more interesting developments has been the move to HVDC transmission - voltages as high as 1.2 MV I belive are shunted about now - and the "receiving end" effectively uses an "inverter on steroids" to handle the ultimate conversion to AC. Some still using giant "bottle" type

There are even some clever little "back-2-back" installations where countries have no sych (or even a 50Hz - V 60Hz issue). The two power systems are linked with an AC>DC>AC system. I would have thought the conversion efficiency would be dismal - but evidently it isn't - or at least not such that it prevents the system being a spinningly good idea.

With the obvious cost of the onverter, usually transmission is only viable on LONG hauls (and apparently under water feeds a great deal too). Losses on transmission however are a fraction of the AC losses for an equivalent system - plus reduced cabling of course.

Googling with HVDC as a search term will bring up more info if you are interested.

Mariomiy - I am not sure about the latest efficiencies with inverters, but HIGH 90's have been around for a very long time - when using square wave, then 98% is not uncommon. That isn't really "Horrible".

As for the LED's, I am stunningly impressed with some of the new 5w luxeon type devices - and I DO see a time when LED lighting is going to be the standard - it already is for rear lights on most new cars, cycle lighting, high-end torches and so on. It is also much easier to make dimmable main LED lamps - as the circuitry is extremely basic.

I am not sure what excited the author about 10 AA batteries storing 18AH. So you now have just under 22 watt hours of power. You cannot REALLY be comparing this with a 12v 18AH battery which stores 216 watt hours can you. Oh and while we're on about it, DO remember that charging a NiMH cell is a rather inefficient process - which is why they get so hot even when charged over a few hours. They also self-discharge too. Don't get me wrong, these batteries are good bits of kit - but they are not an order of magnitude times better than lead acid in terms of watt per gram. Better but only to a point - and dismal from a watt per £1 point of view of course.

The part about "If you need high-voltage, just use an oscillator and a power MOSFET followed by a high frequenty transformer. Fascinating new things became available since I left engineering school. Enjoy them." was a bit naughty.

I suspect most of the people reading this WILL understand that you can make a nice little switch mode power supply to tiddle about with everything from voltage to pulse width games and so on. No need to be patronising.

Also, when you combine the fact that you are making your assumptions on the weight of NiMh batteries being twn times lighter than they actually are (or same weight but 10% of the voltage), I suspect your logic falls down just a tiny bit - after all the battery pack in the corner has just grown 10 fold to be able to do what you had originally planned.

Anyway, I have just realised it is 05:10 and time for me to grab some sleep.

Night folks, play nicely.

Updated by guymark on Oct 3, 2007 9:26 AM