Pragmatic 2D: The Battery Problem Follow-up 4

3 February, 2014


Follow up (Part D) to The Battery Problem where John addresses some more follow up about Flywheels as a form of energy storage, the challenge of disposing of or recycling dead solar panels in 40 years and realistic expectations of DC efficiency.

Transcript available
This is pragmatic follow-up D for episode to the boundary problem and then Alexander and Michael hosted Judge Judy well we had some more feedback regarding our elements of the Barry problem that we talked about one of the alternative energy storage mechanisms out there SO millions of hours flywheels so this particular suggestion came from Matt T via email and is our essentially he just wanted me to slip guide flywheels and sort of discussing the pros and cons so essentially the belladonna flywheel is a flywheels essentially a spinning disk so think of it like a doughnut shaped usually that these the modern ones are a dark shape the oldest riskiest solid desktop that is benign access like a spinning top and they spend extremely high speeds though the idea is that when you have an abundance of energy you stall out energy as rotational energy by words you spin up the disc with your excess energy when there is abundance and limit is a lack of energy in a system you can then engage that rotational energy and politics back out again and because the law of conservation of momentum you can essentially go wrist route you can import energy back out of the year out of flywheel when I first I first heard about this many years ago on a TV show in Australia we was called towards 2000 and eventually beyond 2000 what was that was a show on the ABC that looked at emerging technology from around the world and there was a bus in Europe that they were developing the use flywheel technology to store break energy from the bus every time you would break the bus all that the braking energy was that was coming from the flywheel so flywheel was not move spinning very quickly as you braked that energy was used to spout the flywheel and that resistance from from inertia that slowed the bus down rather than using breaks which are just you carbon on AER steel steel disc and is essentially just dissipating heat so are better because when the bus needs to accelerate again there would re-coupled to the back wheels and these flywheel would then give it a kick to start the bus going again so sound like a great idea but it never really took off and is hotter reasons for that so essentially and I guess the I mention that because first time I heard of truth be told that's really not what I want to talk about too much because the feedback is as it relates to industrial scale energy storage or personal energy storage like in your garage and initiate in the backyard for rather than using batteries disaster hold the point of this feedback so the applications for cars is really beyond the scope of this discussion still are there is a great link in the show notes are where in from an article in the Economist from a few years ago on enough and it actually talks in pretty no pretty easy to understand language about a lot of the technical implications of flywheels in vehicles so if you're interested in that then please check out that link it starts quite a good read actually so the problem was with Ellie flywheels about made heavier the idea is that energy stored is proportional to their mass so the heavier it is the more inertia it has therefore you spin this thing up little store more energy however the problem was that high speeds the flywheel would then just rip itself apart in the heavier it was more likely was derivatives of our specially using something like steel however the thing is that if you double the speed that it spends it actually quadruples the amount of energy stored so the focus changed from being on mass of the flywheel to speed instead but in order to get higher rotational rates and a move away from steel some more modern flywheels are made of carbon fibre composite which is a lot stronger than steel one of the expenses with the flywheels is there they have to have a protective case or shall there has to be other withstand the impact of the shattering of the spinning disc inside so if there is a defect there is a crack in the flywheel flies apart then this device has to contain an entirely inside in such a way that you don't get a shard of carbon fibre flying out and then hitting someone who will was walking past or punching a hole in the wall across the room is not cheap to do that and is deftly not lights these things are not portable but in these sorts of applications that's okay I suppose so ultimately friction is your enemy and is like anything stored mechanically in the longer it spends more energy you lose the friction enacted be our best lessons for solace talk about that gas or air jotting air being a gas whatever woman does that causes parasitic drag and is essentially theirs is actually a good article on Wikipedia about that you learn what a passage drag but is basically where you have AER solid and then you've got a fluid and our active flu and acts as a fluid and as it spinning essentially you will get a resistance pushing in the opposite direction and that's where the beer at that the point of interface between the gas/liquid and solid that spinning so in order to avoid that problem flywheels have to be kept in a sealed near vacuum environment, microwave thermos model works so that's the first thing second thing is the bearings mechanical bearings are just too lost the greatest too much friction and how much grease you put on they will just bleed arm all energy away through friction so the best kind of bearings to use our magnetic bearings however the problem is that magnetic bearings actually permit magnetic bearings have issues with alignment and stability at high speeds what I found though is to get high speeds the most effective way of doing it is to use superconducting magnets and there is a great article again is a link in the show notes to it I invite you to watch a reader if you're interested about some of the reasons why they what they want to use superconducting magnets and now essentially in in high-speed large flywheels are so unfortunately if anyone knows anything about superconductors once were involved with them were stuck with join because high-temperature superconductors are still a long way from room temperature I think the best is our -98 Celsius and that is still very very cold long way from room temperature may consider high-temperature so down to cryogenics of some kind you going down to liquid nitrogen usually want to use because it's the cheapest but with any kind of liquid at that at that temperature what is liquid nitrogen liquid oxygen Maywood music when oxygen or you and else the problem is liquid helium may there's an effect called the Ya lead and frost effect and it is and it's annoying because when a liquid that touches a solid and the solos of significantly high-temperature that is above the boiling point of that liquid essentially that gas turns that liquid turns into a gas at that contact point was it does that gas literally insulates the liquid further liquid further liquid surrounding it from directly touching the surface and that insulating effect essentially prevents further cooling of that object where is your calling as a pain in the neck there are ways around it but it adds complexity and adds cost Tiger thermos yeah it's the thing is also with with with liquid nitrogen it may will be cheap to make video be handled very carefully and even though you can store it in a thermos and in special ghost origin has a basically just last thermos flasks are it still will go off eventually it will warm up to a point where it is a gas and that's the end of so you got all this extra handling that needs to happen in all this extra complexity and cost in order to keep superconductors call or give it spinning a high speeds without friction losses so for these reasons the only area that flywheels have had any involvement at all is in vehicles I said I was not talk about it discreetly flywheels are good for an application because they store energy for short periods of time only between acceleration and braking so the recently they had them in honey was Formula One and is are you using for our food for short periods of boost but the fact is that they just don't scale but I would really work on a private level because of all the cooling that is required and if you go with the cheaper methods of either the permanent magnets you simply won't be store enough energy and to make it worthwhile however as hydrogen semiconductors actually do approve approach room temperature and it is only a matter of time I believe they'll come up with one that does so with better material science maybe one day flywheels could replace batteries in some ways however at this point I have a long way to go so that was flywheels had some feedback from Chris Osan and via Clinton Phillips recital was a former editor of the strain MacWorld and Czar he raised the interesting issue of recycling solar panels concern is as I stated everyone go solar solar panels last with 25 3040 years if everyone has a mass adoption and there is at the moment mass adoption going on what happens in 40 years time and is a massive oversight massive supply of essentially dead solar panels what you do now I did say that during the episode it was the now recyclable but I really didn't go into any depth in the slide deck that I prepared from my previous jobs are published along with episode two are the slide explores solar system design on slide number 38 which is nearly at the very end essentially are published back on the arm this onset distortion a month or so ago I'd advise the I did address the issue of recycling the assault else but didn't go into a huge amount that is basically three components that are recyclable first what is the glass and is pretty obvious is very easily separated from the rest of it melted down and you recycled no problem I recyclable aluminium frames and support ribs again same deal they are easily separated recycled just like an arm aluminium can the third one and more interestingly of that one is silicon wafers themselves the little bit more difficult mainly because they're bonded to our special backing and support nice stuff so there are ways that they can separate them and that they can reclaim most the silicon that was used in them to be reused and I found a really good essay written by gentleman by the name of the neck neck we dock or we are dock called recycling methods for used photovoltaic panels links and show notes if you're interested please check it out it's quite good and eats and includes the cost of recycling you solar panels is actually pretty good but go rather perhaps obviously I think there simply is not enough infrastructure to support sort of scale that is going to be needed in coming years by looking this to the way the batteries used to be held are used to be dealt with as when I was kid barristers went to the Don Wright been who no one was really too concerned about heavy metals and toxic chemicals getting into the water table ministry burn nowadays it is that's criminal you can't do that because as recycling plans in place for you drop a battery off a special place at the rubbish dump the rubbish tip and they will then take the draining acids and process that so it becomes inert and do not take whatever letters left and they'll melt that down to uses anything from lead sinkers to lead linings to new plates for new lead acid batteries so is that eventually it's only a matter of time before they scale up with exactly the same thing I've already done for car batteries and TV sets and all sorts of other things about recycle so that was our recycling assault else last one is more talk about if you still hanging in there gentleman by the name of Brian Nehring via a feedback form and he asked the question would there really be an improvement in efficiency with purely DC appliances I made in France was offhand not really I made a comment that it would be better if we just use DC so his point is that you have to do switched mode conversion to go from DC to DC voltages so your change from 48 V 220 V or down to 24 V of eyebolts you have to do some kind of switching of the power on and off on foreign office we get losses from just as much as you do going from DC to AC whether it's hundred and 20 V AC 230 V AC whatever and then back down in the appliance says point was you have switching losses number which way you choose to go so I thought I'd like to elaborate on that and is is actually quite a bit to say about I found a report from the IEEE which is the Institute of Electrical and electronic engineers desire a global organisation and it suggests that there could be as much as 25% efficiency improvement moving from AC/DC a household environment however I really doubt that's actually the right number thing as well as optimistic best possible case numbers I think 15% is poly more realistic based on my observation because you have to realise that a lot of houses 20 years ago were done with DC if they have with our solar because inverters are simply so expensive and multipoint power tracking on solar panel modules simply didn't exist now we've got microcontrollers and everything built these things the cost of the RGB teas for the switching of the power is so cheap you what we can do this conversion wasting my point is that it that doesn't make sense to do it if you're striving for the maximum amount efficiency so I say about 15% and a 50% equates to less 50% less batteries 50% less solar panels anatomy thousands of dollars of upfront costs higher in aids it's JSP was a 50% arm I isolate like a 50% saving something massive for actually it is massive now so present huge it is and but you are asking about my IR 25/like 1/4 set yet I don't believe that number and a stuck result from a suitably present its decent size were striving for/breakdown look at the individual pieces there's a few angles there that I the IEEE report did not cover which I cover first one of those is AC has a problem and AC's problem is that it's voltages quoted in root mean square of the RMS value is the square root of two of its peak value size sine wave goes up-and-down up-and-down up-and-down are in a nice sinus oil waveform still very pretty but the point is that the root mean square voltages essentially got there with the effective amount of power that is actually transferred so you actually do your mass based on the RMS value voltage not the peak value when it comes to installation actually the peak value is the value that matters because if installation is going to break down it's going to break down at that point where it hits the peak voltage and remember it's it's a positive and negative peak as well so you've got a voltage differential out with AC that is swinging if it's our 120 V AC Basson RMS value but the peak voltage of those acting hundred 70 V and is plus or minus hundred 70 V so you now have to design all of your power cables to handle hundred 70 V minimum possible to headroom so always oversized cable are installation to make a figure that needs to be the funny thing is if it was all DC you would have to worry about 120 V DC is currently involved DC so your installation would not need to be as thick and therefore over a lot of cable that will be cheaper does not necessarily efficiency being in that case but it's definitely a cost saving so AC also has the downside of coupling we talked about this in the upside and eat couples through magnetic coupling with parallel cables it's much more evidence over a long transmission lines of your transmitting power over 10 km in a 30 miles whatever then obviously the impact of this can be far more noticeable around the house we've got wise going up down left right all over the place it's going very difficult to quantify but there will be loss honestly my best estimation I would say on an average household looking about 1 to 2% of lost through coupling they must not huge amount but it's it's part of the common contributions that 15% so going DC essentially eliminates that so that's about the cost saving rather but the biggest efficiency gain is the avoidance of AC altogether because once you go AC you've got something called total harmonic distortion and the thing with THD is that when you switch when you switch the power or not you switch on and off as a series of pulses and the width of the pulses changes so start extremely narrow get slightly wider slightly wider against the big fat wine one member get narrower and narrower again then we filter that you end up with a waveform that looks like a sine wave switching from DC to AC which is what most occurrences observers does like the one my garage the problem with that is it's not perfect it works and positive modulation is a wonderful thing however the problem is that limit how she felt stress will always have what they call harmonic currents and voltages now these harmonics represents you look at my spectrum analyser you'll have a fundamental frequency of your voltage in North America at 60 Hz and Australia's 50 Hz Europe writing is also 50 Hz mostly so you have you harmonic frequency but you have a whole bunch of parsley have your fontanelle from Seattle but harmonics are most harmonics will be 11 double triple on even harmonics in style and so forth up-and-down perspective and the amount of energy in each of those harmonics is loss so that's a problem and it's not a problem if you got DC mean yes when you do DC DC switching yes you are going to get noise it's a lot easier to filter out on a DC DC converter you'll never get rid of it then you elaborate on AC and you've got a lot of harmonics because you're trying to create a fundamental frequency using an nonideal source was a DC you you may will chop into different pieces and whether if you got a boost converter but was converter of whatever rosters are either article on of links on Wikipedia please check it out I go to the details nominee degree of DC DC converters but the point is that it will it will always be a smoother output than you will get from an AC DC to AC converter so in terms of actual efficiency however the reality is and the numbers vary because every design is different but based on the information that I was gathering I knew wasn't a heck of a lot but the efficiency of DC DC over AC/DC is about 88% so that I percent goes in without one to 2% from before and is essentially there are fewer losses but their harder and more specific and I won't go into those but the key ones are those it depends on the converters design and depends on the output requirements of the city's converter is well surveyed percent could be a lot higher could be 1012% on-site so I hate saying it all depends but it does all depend because it's kinda like saying that the efficiency of all the CDs are always use converters the same but that we know they're not because if you get an Apple are five what iPod charge of your wall plug back that is an AC/DC converter drops down five bolts guarantee you that its efficiency will be different from a run-of-the-mill black wall wart wall plug from no name brand from somewhere in Taiwan that is not to say that there are ones in Taiwan that are better understandably different sides how to give a definitive percentage on but I thought about what would be the biggest thing in a household that would benefit from going to DC and there is a perfect example and that is LED light bulbs CID lightbulbs LEDs as diets their LEDs light emitting diode and a lot of dieters just a PN junction and when you've got a PN junction are as a diode it only allows current in one direction just for so AC is already a bad choice because what it means is that you only get light 50 times a second one continuous flicker because you're only undergone a positive part of the sine wave we've got forward voltage over the PN junction is a summary get light while the ways around that is to have diets in both directions so you get a burst of light and forward in a burst like the reverse direction from two different LEDs wired differently but that's a bit wasteful because liquor using twice as many LEDs you need to so the solution that most of these LED light bulbs currently use is they have an AC/DC converter in Adelaide they take the DAC hundred and 20 V 240 V whatever it is they rectify and they turn that into a DC signal and regulated down to the required voltage in DC because LEDs are some essentially are you why DC constant current going through them so your costs are lined out now as other issues of causal LEDs in the high currently passed through them the more light you get that's great but unfortunately the more clarity put through a diode you have to be able to cool it otherwise the ER .7 V drop across the diode yet me PN junction that dissipation will essentially melts your tired battle a copy he sinks on these things are to get the heat out of the PN junction will destroy itself so even with all of that LED light bulbs are still more efficient much more efficient than a CFL combat fluorescence or a Yum tungsten filament sure deftly around the halogen so what would happen if you had an LED light bulb that had no AC was just DC voltage straight out of the wall well obviously they would be more efficient straight out the blocks to be no conversion required no AC/DC lost that that that could go BAE 15% saving right there is no AC/DC conversion failing is when LED lights first came out they all were DC so this whole AC thing is been a direction of gone simply because DC is not available houses generally but if you're building a solid house 20 years ago and you are having lightbulbs you do not DC there were other low-voltage lightbulbs because LEDs were quite that point yet but you can still get DC LED light bulbs are very efficient so let's say the last piece of this is the lower voltage so why would see is in future you if you had the senior house staff to voltages lighting circuits essentially sit it's just a bunch of sockets on the roof arm you plug something into it so you not to have high current demand because all your your highest current money LED light by scenes at 13 W really and that's very bright you're not gonna need that much more than the obvious problem is if I keep putting a lower lower voltage because people's VI of the problems going to be that my current requirements will go up so if I have are lower voltage likes to say I like circus 12 V and that's fine because low-voltage is better for the LED lights is less than they need to be a regulated way and it's awkward so what you will do then is your run the cabling around the house just like you would for the AC lightbulbs but you will have about 10 A roughly most most electrical cables are sized 10 A of crossover copper cross-sectional area, canals and amps about points let's say you got eight what LED light bulbs I'm saying a want because I'm stuck in a number out of my head because as the last lies LED light, bought but I've got a couple nines and a couple of sevens associate is an average that will give you hundred 20 W per circuit and that mill be about eight what LED bulbs that's about 15 lights per circuit that's pretty good that's pretty comparable to what you'd expect now to 40 lightbulb bulbs with exactly the same copper in the roof so is no cost difference there at all now because you've got larger appliances that require more current you would not have a 12 bolts you have the missile high-voltage probably 48 V or 24 bolts either either or you have more current requirements so you may spend a little bit more on copper upfront potentially may be lost and Isa 96 bolts all you hundred 20 bolts I don't know but if it's DC then obviously the higher the voltage because people's VI high-voltage the less the current year trying to reduce the amount current because you don't want to have are really thick copper cables because you garden current copper is expensive you don't want to spend that money on your cables and the that's all have Cybele so thank you very much for the feedback everybody�
Duration 26 minutes and 22 seconds Direct Download


Ben Alexander

Ben Alexander

Ben created and runs and Fiat Lux

John Chidgey

John Chidgey

John is an Electrical, Instrumentation and Control Systems Engineer, software developer, podcaster, vocal actor and runs TechDistortion the Engineered Network and technical whitepapers at Control System Space. John is a Chartered Professional Engineer in both Electrical Engineering and Information, Telecommunications and Electronics Engineering (ITEE) and a semi-regular conference speaker.

John has produced and appeared on many podcasts including Pragmatic and Causality and is available for hire for Vocal Acting or advertising. He has experience and interest in HMI Design, Alarm Management, Cyber-security and Root Cause Analysis.

You can find him on the Fediverse sometimes called Pleroma or Mastodon.