What does a kilowatt hour look like?

Given 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&#x27;t even begin to contemplate.<p>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.

1 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.

&gt; David McCay - Sustainable Energy without the Hot Air<p>A fantastic book. A Caltech trained physicist at Cambridge does the calculations to see if the UK could get all its energy needs sustainably.<p>Simple, easy to understand, and enlightening. It deserves the praise they talk about.<p>And it&#x27;s free to download.

1kWh as gasoline is about 1&#x2F;10 liter. Though one will not get anywhere near that much high-quality electric energy with consumer&#x2F;small-scale methods.

&quot;So, what a kilowatt hour of high-grade electric energy can do for you? Many useful things, i.e.:<p>deliver 4-5 kWh of low-grade heat (or cold) into your home (depending on COP of a heat pump)&quot;<p>Huh? I assume he means 0.4 - 0.5 kWh?

The book recommended here, David MacKay&#x27;s <i>Without the Hot Air</i> 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.<p><a href="http:&#x2F;&#x2F;www.withouthotair.com" rel="nofollow">http:&#x2F;&#x2F;www.withouthotair.com</a><p>MacKay himself, a CalTech-trained physicist, worked at Cambridge. He died about five months ago, noted only modestly at HN: <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=11500614" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=11500614</a><p><a href="http:&#x2F;&#x2F;itila.blogspot.com&#x2F;2016&#x2F;04&#x2F;index-for-first-23-cancer-chapters.html" rel="nofollow">http:&#x2F;&#x2F;itila.blogspot.com&#x2F;2016&#x2F;04&#x2F;index-for-first-23-cancer-...</a><p>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:<p>1. It goes through the major uses of energy in modern life. Getting a feel for the comparative magnitudes is quite useful.<p>2. It compares the various options for renewable energy. It turns out that there&#x27;s a lot less energy in renewables than would be convenient. Wind and Solar are much of the easy stuff.<p>3. It mapps out both energy consumption and use <i>by area</i>. Realising how many watts per square meter are used and are available is useful.<p>4. He really presses the point that solving the energy conundrum requires <i>large</i> changes. Unplugging charging devices won&#x27;t cut it. Hitting major consumption, especially transport, heating, lighting, and refrigeration, help a lot.<p>If you&#x27;re interested in pursuing the issues further, I strongly recommend Vaclav Smil, whose books I&#x27;ve been going through. For a historical view, Smil&#x27;s <i>Energy in History</i>, and the more recent two-volume book, <i>Sources of Power</i>, 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.<p>Fascinating and terrifying at the same time.

&gt; So, what a kilowatt hour of high-grade electric energy can do for you?<p>According to my car, it lets me drive 4.2 miles at highway speeds.

What does a Newton-meter of torque feel like?<p>Reopening a plastic soda bottle.<p>From a web interactive I wrote: <a href="http:&#x2F;&#x2F;www.clarifyscience.info&#x2F;part&#x2F;ZoomB?v=A&amp;p=CK6Ji&amp;m=torque" rel="nofollow">http:&#x2F;&#x2F;www.clarifyscience.info&#x2F;part&#x2F;ZoomB?v=A&amp;p=CK6Ji&amp;m=torq...</a> (2014)

Not related, but I hate this unit. Can&#x27;t we just talk about Joules?

Then you compare with the amount of energy in a liter of petrol (~10kW&#x2F;h). And you realise how we&#x27;re living literally awash in crazy amounts of energy, equivalent to having all hundreds of slaves working for us 24h a day.

It would have been nice if the article&#x27;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.<p>I think that&#x27;s pretty accessible and could only add to the article&#x27;s value by answering the question, &quot;What does &#x27;kilowatt-hour&#x27; mean?&quot;

Less acronyms please. (COP, PV, and even EV)

Riding an electric bike has made me very aware of how much work can be performed with a given amount of power. Watt-hours aren&#x27;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&#x2F;h) on the flat.<p>It really puts things in perspective when I look at a 1KW space heater. That&#x27;s a lot of power!

I like his battery haha, colorful. Also nuts to test all those cells. Make sure they&#x27;re all roughly the same performance. wonder how hard it would be to find a bad cell.

&quot;deliver 4-5 kWh of low-grade heat (or cold) into your home (depending on COP of a heat pump)&quot;<p>If you don&#x27;t use a reverse cycle system you can more like 8 kwh of heat or cold

I 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&#x27;t anticipated by the author. I think if modern prices were used the 5 models at the end would look very different.

If you like this, watch the videos from this guy:<p><a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;user&#x2F;jehugarcia" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;user&#x2F;jehugarcia</a><p>he methodically tests old 18650 laptop cells, sorts them, builds battery packs and so on. He&#x27;s converted a classic VW bus to electric power using his home-made battery packs and packs salvaged from wrecked teslas.

Lithium-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.

A single 12V 100Ah VRLA Deep-Cycle battery might be a better idea that&#x27;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&#x2F;transmission losses in most scenarios, thus delivering a true kilowatt-hour!

Batteries have different discharge curves, influenced by many factors such as chemistry, age, etc. Often &quot;packs&quot; of cells are balanced in an attempt to minimize variance. Something tells me your 10kW &quot;wall&quot; may not perform as you expect it to (providing you are actually loading it for real use).

If we don&#x27;t have to move the battery around, why not use cheaper but less compact techs for storage?

I&#x27;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 ?

1 kWh = 3600 kJ = 95g of lard (or body fat!) = 85g (115 mL) of petrol&#x2F;gasoline = 1.5 Big Macs = 40% of an average male&#x27;s daily energy intake = ...

1&#x2F;33.7 of an exceptionally privileged imperial gallon of petrol, according to US regulators.

What.