10 ms·
What does a kilowatt hour look like?
- soperj 10y agoWhat.
- qoobaa 10y agoThanks, I fixed the title. I'm not an English native, so I make a lot of errors like this :-).
- soperj 10y agoNo problem.
- luhn 10y ago*Watt
- TeMPOraL 10y agoOne kilowat, i.e. one thousand lines of Ruby or JavaScript code. https://www.destroyallsoftware.com/talks/wat https://www.destroyallsoftware.com/talks/wat
- outworlder 10y ago> So, what a kilowatt hour of high-grade electric energy can do for you? According to my car, it lets me drive 4.2 miles at highway speeds.
- qoobaa 10y agoInteresting, is it Tesla? Which model is it?
- freerobby 10y agoAs a reference point, a Tesla 85D uses 290 watt-hours to go one EPA rated mile. So 1 kWh takes you 3.448 miles.
- chrisseaton 10y ago> one EPA rated mile Are EPA miles not the same as normal miles?
- detaro 10y agoWhat's a "normal mile" regarding energy consumption? There is a series of standardized driving profiles that is averaged to get a comparable, somewhat realistic value.
- spydum 10y agojust guessing, it's a standardized way to declare the driven distence, given all the variables.. such as: up hill, down hill, low/high rolling resistance surface?
- walrus01 10y agoI think the poster means the EPA test cycle for miles, they have a pre-defined "cycle" of acceleration, braking, coasting etc for Highway ratings and City driving.
- ctdonath 10y agoI had a Leaf; the typical cruising power consumption was 4 miles per kWh. Battery was 26kWh.
- revelation 10y agoA kWh gets me easily >30km on my bike (250W for 1h if you assume average 25% efficiency)
- adrianN 10y agoBut you don't ride at highway speeds ;)
- whamlastxmas 10y agoBike also doesn't weigh 2500 pounds
- titzer 10y agoDrivetrains on bikes can be > 98% efficient, so I assume you mean the human power output efficiency. But 250W applied directly to the crank via an electric motor should get you a good 40km/h for 4 hours! :)
- 205guy 10y agoIn a Nissan Leaf, you can get around 5 miles per KWh average. You can plug in the 1.1 kWh charger and realize you will get 5 miles per hour. If you use a bigger 6.6 kWh charger, it's 30 miles per hour. Better yet, you can fiddle with the dash controls and get a power meter: acceleration takes 30-60 kW, but regeneration can make up to 30kw. Like the OP says, this kind of thinking really changes your perspective.
- jasoncchild 10y agoBatteries have different discharge curves, influenced by many factors such as chemistry, age, etc. Often "packs" of cells are balanced in an attempt to minimize variance. Something tells me your 10kW "wall" may not perform as you expect it to (providing you are actually loading it for real use).
- qoobaa 10y agoI know it's not as simple as "connecting 10k batteries together". It's an interesting topic anyways, there are a few guys already doing it with promising results (check HBPowerwall on youtube for instance). BTW: I haven't even connected these cells together yet - even that is not as simple as it may look like.
- deleted 10y ago[deleted]
- jononor 10y ago1kWh as gasoline is about 1/10 liter. Though one will not get anywhere near that much high-quality electric energy with consumer/small-scale methods.
- xyzzy123 10y ago1kWh as aluminium is about 66g (assuming 15kWh per kilo manufacturing input) or about 4 drink cans.
- bigiain 10y ago25 million kWh as mass is about 1g (E=mc^2) so 1kWh is 40 nanograms or about 1/150th of a grain of sugar. (handwaving away a method for 100% efficient conversion of mass to energy... But solving that would be a _really_ good thing...)
- mrfusion 10y agoWow so I could gather up a bunch of cans and heat my house.
- deleted 10y ago[deleted]
- jrockway 10y agoThe key to batteries is being able to use the stored energy. Bonus points if you can add energy and get it back later.
- madengr 10y ago"So, what a kilowatt hour of high-grade electric energy can do for you? Many useful things, i.e.: deliver 4-5 kWh of low-grade heat (or cold) into your home (depending on COP of a heat pump)" Huh? I assume he means 0.4 - 0.5 kWh?
- monochromatic 10y agoHeat pumps are more efficient than just using a resistive heater.
- semi-extrinsic 10y agoNope. Heat pumps have a COP > 1. It's quite literally a pump moving heat from a cold place to a warm place. If it takes 1 kWh to pump 3 kWh of heat from outside your house to inside (in winter), you've heated your house by 4 kWh. Note that the electric energy used to drive the pump is transformed into low grade heat, which in this case is useful.
- SilasX 10y agoGood point! It kinda threw me off too, since heat energy isn't usually measured in kWh. But yeah, heat is a kind of higher-entropy form of energy than electricity, so you can, in fact, turn one unit of the latter to more than one unit of the former. The "exchange rate" depends on the temperature; the maximum ("Carnot") heat pump efficiency is T_high/(T_high - T_low), where T_high is the temperature of the room being heated and T_low is the surrounding environment the heat is being pumped from (all on the absolute scale). When T_high = T_low, the max COP is infinity, which has the physical meaning that "You don't need to spend any energy to keep a room the same temperature as its environment; that happens automatically." https://en.wikipedia.org/wiki/Coefficient_of_performance#Derivation https://en.wikipedia.org/wiki/Coefficient_of_performance#Der...
- jrockway 10y agoIt's an air conditioner in reverse. You run your AC at 2kWh (or so) and you've heated the outside environment by more than 2kWh; otherwise your house wouldn't be cold, energy and heat don't magically appear or disappear.
- grondilu 10y agoNot related, but I hate this unit. Can't we just talk about Joules?
- qoobaa 10y agoIt's not pretty,but it's practical. Especially when it comes to electricity - watts and hours are quite easy to work with.
- grondilu 10y agoPerhaps, but it makes conversion to and from an other domain than electricity a pain.
- chriswarbo 10y agoIt doesn't make much difference whether you use Watts or Joules, since 1 Watt = 1 Joule per second, so both are just as convenient for electricity: 1 Watt = 1 Volt Amp, so 1 Joule = 1 Volt Amp Second = 1 Volt Coulomb (although amps seems to be more "normal" than coulombs). It's a bit redundant to multiply power by time, when that's just an energy, but going between Watts and Joules is trivial (by design), so it's not too bad. However, I can't think of a reason why hours would be easier to work with than seconds (as kiloseconds, if you want the same order of magnitude), especially regarding electricity?
- sesqu 10y agoIt's because power needs are reported as watts, and impactful devices are typically utilized for several hours. It's much easier to do your monthly utilization napkin math in multiples of kilowatt-hours than of 3.6 megajoules. I'm personally not a fan of the kWh, because it keeps being mistaken for kW, but I recognize that lack of need for a conversion factor help a lot of people make sense of energy.
- Retric 10y agoJoules are tiny it takes 3.6 million Joules = 1kWh
- mpreda 10y ago1 Wh is about 0.9 kilocalories. So 1kWh is about 100g of butter. The energy expenditure of a human in one day is about 2kWh. 1kWh is about the energy needed to heat 10L of water from 0 deg celsius to 100 deg celsius.
- javajosh 10y agoIt actually takes some extra energy to move from ice to water, and also some extra energy from water to steam, so your numbers only work out if you are strictly inside the 0-100C range. It's interesting to realize thought that we programmers are code producing machines that run on roughly 2kWh per day. If we produce 100 lines of code in a day, that's 20Wh per LOC. Not bad, actually.
- jfoldager 10y agoWater can be 0-100 C, both temperatures included. No need for melting/turning to steam. You could start with 10 L of 0 C ice, but he said water.
- basicplus2 10y agoI like the analogy of a bag of peanuts is equivalent to a teaspoon of petrol (properly aspirated) or a stick of dynamite
- robbrown451 10y agoLess acronyms please. (COP, PV, and even EV)
- qoobaa 10y agoYou're right. I normally use <abbr> for that, but I forgot this time. I'll fix it.
- Jugurtha 10y agoCOP: Coefficient of Performance. PV: Photovoltaic. EV: Electric Vehicle. TMDA: Too Many Damn Acronyms (It's a joke I heard at a company that had acronyms for everything).
- 0xCMP 10y agoWe name different projects after Greek Gods + acronyms. The names can be pretty fun.
- Jugurtha 10y ago"Where's Dionysus' Project Manager?" "In a bar, somewhere.."
- vacri 10y agoWell, a TLA is a TLA, but an FLA is not an FLA (it is also a TLA)...
- dredmorbius 10y agoETLA is a FLA. DETLA is also a FLA.
- Jugurtha 10y agoIt depends. Facing each other, when one says "to the right", does he mean to his right or to the interlocutor's right? Furthermore, Are RFCs TLA? It appears that IANA, an FLA itself, standardized the use of TLAs in an RFC. https://tools.ietf.org/html/rfc5513 https://tools.ietf.org/html/rfc5513
- spdustin 10y agoGiven how popular (and damn near impossible to discern) unsafe and unprotected lithium-ion batteries are, the idea of making a homegrown power wall terrifies me in ways I can't even begin to contemplate. An 18650 battery, if combusted, can produce hydrofluoric acid with just water vapor in the air (or the water in your lungs) if they use lithium hexafluorophosphate as the electrolyte. Hydrofluoric acid can and will cause permanent damage to lung tissue if inhaled, and nasty, nasty chemical burns to exposed skin. 18650 batteries are supposed to have several failsafes to prevent thermal runaway, but counterfeit batteries can lack those failsafes. Not to mention, in some laptop battery packs, the protection was pack-wide, and not in individual cells. Not knowing the chemistry of the cells or the state of the protection circuitry of the battery would make me very nervous. Maybe someone else can provide more detail on how to test them safely.
- gravypod 10y agoI came here to say just that. This is a horrible idea and definitely not something you should do. Just use sealed AGM batteries, don't burn your house down or deal with spilling chemicals everywhere. Even just drawing in parallel from batteries like this is a fire hazard. Charging is an out of your mind goal.
- agumonkey 10y agoWow, as someone uneducated about anything related to electricity and power, seeing the picture in the article really made me want to emulate the setup. Not anymore.
- gravypod 10y agoYou joke buy many many people don't know how volatile battery chemistry is and how different charging of Lithium cells works. I'd not have known how much of a bad idea this was had I not been a long time fan of EEVBlog. It's an entirely different world when touching Lithium cells. Even drawing in parallel from cells from the same batch can be a bad idea.
- userbinator 10y ago
- mncharity 10y agoWhat does a Newton-meter of torque feel like? Reopening a plastic soda bottle. From a web interactive I wrote: http://www.clarifyscience.info/part/ZoomB?v=A&p=CK6Ji&m=torque http://www.clarifyscience.info/part/ZoomB?v=A&p=CK6Ji&m=torq... (2014)
- Koshkin 10y ago> Newton-meter I do not know why (and I do not have a strong opinion on this), but somehow this (relatively recent) tradition of naming units after people feels weird to me. I know we are already used to these units, but imagine the unit of mass was called Einstein instead of kilogram.
- nitrogen 10y agoHow recent is the trend? Most of the units I know are named for people: Joule, Watt, Volt, Ampere, Newton, Angstrom, Ohm, ...
- Symbiote 10y agoBy convention, SI units named after people have capital letters for their symbol. http://physics.nist.gov/cuu/Units/units.html http://physics.nist.gov/cuu/Units/units.html
- Koshkin 10y agoI am sure Newton didn't name the unit of force after himself, so I would roughly place the invention of such possibility around early/mid nineteenth century, that is, about 200 years ago, which is when the research in such areas as electricity and magnetism, thermodynamics etc. was in full swing.
- daurnimator 10y agoThe Newton unit has been around since 1948. But that was hardly the first term to be named after someone: Watt has been used since 1882, Farad since 1881, Fahrenheit since 1776...
- agumonkey 10y agoI've been very curious for a very long time about people doing indoor bike workouts while storing the pedaling energy in batteries. Any of you do such things ?
- 205guy 10y agoOne the one hand, this would be good for people who overeat (more calories than they usually expend). On the other hand, in absolute terms, it is just turning agriculture into a source of power very inefficiently (a methane digester would be much better).
- agumonkey 10y agoEfficiency is not the goal, it's more symbiosis. Humans benefit from "wasting" energy through exercise. Instead of lifting weight and riding bikes, why not try to leverage it.
- ars 10y agoYou would get very little out of it. Enough to run a dim LED for a couple hours at most. If you did it in addition to (as opposed to instead of) your exercise then the energy in the food you ate is massively greater than what you can get from the bicycle. If you eat more as a result then you wasted your money.
- mikeash 10y agoIt wouldn't be quite that bad. You're probably putting out something like 100-200W. Even factoring in generating and storage losses, you're looking at running a reasonably bright LED bulb for several hours on the proceeds of a 30-minute session. Still not worth the effort of building the equipment, of course.
- agumonkey 10y ago200w seems for pro cyclists. 100w for above average sports fan. Today lots of computing devices fall under 10w power usage. Hence my daydream. For light or electric appliances that's another story.
- ge96 10y agoI like his battery haha, colorful. Also nuts to test all those cells. Make sure they're all roughly the same performance. wonder how hard it would be to find a bad cell.
- TD-Linux 10y agoProbably the most obvious indication would be temperature. Assuming they are in parallel, it'd be quite wise to measure their discharge curves to only select similar cells - that would also highlight any bad ones.
- ge96 10y agoHmm. It did appear that the cells were all oriented in the same direction. What a great idea I think although I wonder if it's a pain, cutting through that hard, protective plastic that these cells are in for laptop batteries. Unless you buy just the cells themselves.
- spodek 10y ago> David McCay - Sustainable Energy without the Hot Air A fantastic book. A Caltech trained physicist at Cambridge does the calculations to see if the UK could get all its energy needs sustainably. Simple, easy to understand, and enlightening. It deserves the praise they talk about. And it's free to download.
- titojankowski 10y agoSustainable Energy Without the Hot Air Free from the author's website: http://www.withouthotair.com/download.html http://www.withouthotair.com/download.html
- deleted 10y ago[deleted]
- basicplus2 10y ago"deliver 4-5 kWh of low-grade heat (or cold) into your home (depending on COP of a heat pump)" If you don't use a reverse cycle system you can more like 8 kwh of heat or cold
- walrus01 10y agoIf you like this, watch the videos from this guy: https://www.youtube.com/user/jehugarcia https://www.youtube.com/user/jehugarcia he methodically tests old 18650 laptop cells, sorts them, builds battery packs and so on. He's converted a classic VW bus to electric power using his home-made battery packs and packs salvaged from wrecked teslas.
- sporkologist 10y ago> wrecked teslas Wait what? where is this supply at
- walrus01 10y agoCalifornia, mostly, but not exactly a common thing yet. Will increase as more cars are totaled in rollovers or other crashes that mess up all of the body work.
- maxehnert 10y agoCopart is a good site for buying wrecked cars in various conditions. Otherwise try calling your local junk yards. http://www.copart.com/us/search?q=tesla http://www.copart.com/us/search?q=tesla
- deleted 10y ago[deleted]
- jqkeller 10y agoI was just commenting today how approachable this book makes understanding the requirements to transition to renewable energy. I would warn though that the little bit of economics and the discussions about battery storage and solar PV at the end are very dated. The exponential drop in pv prices wasn't anticipated by the author. I think if modern prices were used the 5 models at the end would look very different.
- cowardlydragon 10y agoIf we don't have to move the battery around, why not use cheaper but less compact techs for storage?
- perilunar 10y ago1 kWh = 3600 kJ = 95g of lard (or body fat!) = 85g (115 mL) of petrol/gasoline = 1.5 Big Macs = 40% of an average male's daily energy intake = ...
- ninja-wannabe-7 10y ago1/33.7 of an exceptionally privileged imperial gallon of petrol, according to US regulators.
- lightedman 10y agoA single 12V 100Ah VRLA Deep-Cycle battery might be a better idea that's more familiar to a much larger chunk of the population, and you have the added bonus of having enough capacity to make up for the typical conversion/transmission losses in most scenarios, thus delivering a true kilowatt-hour!
- vamur 10y agoLithium-ion batteries require an expensive materials and overly complex manufacturing (Gigafactory). They are also dangerous as evidenced by the Samsung Note 7 debacle. Hopefully, there will be advances in making lead-acid and hydrogen fuel cells cheaper and safer. That would allow viable energy storage for solar PVs.
- whamlastxmas 10y agoDangerous depending on the chemistry. There are plenty of very low volatility lithium ion cells out there.
- wazoox 10y agoThen you compare with the amount of energy in a liter of petrol (~10kW/h). And you realise how we're living literally awash in crazy amounts of energy, equivalent to having all hundreds of slaves working for us 24h a day.
- qoobaa 10y agoIt's even more terrifying considering the fact that it took millions of years of to accumulate such amounts of energy in fossil fuels (it's literally sun energy laying underground). Sooner or later, we'll run out of it… BTW, it's not 10 kW/h, but 10 kWh in a litre of petrol.
- lutusp 10y agoIt would have been nice if the article's author had provided a short technical explanation of kilowatt-hour. A kilowatt-hour is a unit of energy, and energy is the time integral of power. It follows that energy in kilowatt-hours is the time integral of power expressed in kilowatts, i.e. one watt for a thousand hours, a thousand watts for one hour, and so forth. I think that's pretty accessible and could only add to the article's value by answering the question, "What does 'kilowatt-hour' mean?"
- dredmorbius 10y agoThe book recommended here, David MacKay's Without the Hot Air really is remarkable, and I highly recommend it to anyone with an interest in energy, renewables, or nuclear (which MacKay somewhat grudgingly endorses), and the energy-intensity of modern industrial life. http://www.withouthotair.com http://www.withouthotair.com MacKay himself, a CalTech-trained physicist, worked at Cambridge. He died about five months ago, noted only modestly at HN: https://news.ycombinator.com/item?id=11500614 https://news.ycombinator.com/item?id=11500614 http://itila.blogspot.com/2016/04/index-for-first-23-cancer-chapters.html http://itila.blogspot.com/2016/04/index-for-first-23-cancer-... Of the book, I find a few things particularly illuminating. For starters, it is rather UK-centric, though the concepts are of course generally applicable. Beyond that: 1. It goes through the major uses of energy in modern life. Getting a feel for the comparative magnitudes is quite useful. 2. It compares the various options for renewable energy. It turns out that there's a lot less energy in renewables than would be convenient. Wind and Solar are much of the easy stuff. 3. It mapps out both energy consumption and use by area. Realising how many watts per square meter are used and are available is useful. 4. He really presses the point that solving the energy conundrum requires large changes. Unplugging charging devices won't cut it. Hitting major consumption, especially transport, heating, lighting, and refrigeration, help a lot. If you're interested in pursuing the issues further, I strongly recommend Vaclav Smil, whose books I've been going through. For a historical view, Smil's Energy in History, and the more recent two-volume book, Sources of Power, by Manfred Weissenbacher, explore how human history has been shaped by access to energy, from gatherer-hunter days, agriculture, coal, oil, and whatever comes next. Fascinating and terrifying at the same time.
- throwaway7767 10y agoRiding an electric bike has made me very aware of how much work can be performed with a given amount of power. Watt-hours aren't abstract anymore. 1kWh can get me and my stuff 120km easily if I pedal, probably closer to 80km if I used battery power only. Also instantaneous power, 200W is enough to move my bicycle, me and my stuff at a low cycling speed (15-20km/h) on the flat. It really puts things in perspective when I look at a 1KW space heater. That's a lot of power!