Not related, but I hate this unit. Can't we just talk about Joules?
Joules are tiny it takes 3.6 million Joules = 1kWh
What does a kilowatt hour look like?
21–30 of 147 posts
Re: What does a kilowatt hour look like?
#22Re: What does a kilowatt hour look like?
#23Less acronyms please. (COP, PV, and even EV)
You're right. I normally use for that, but I forgot this time. I'll fix it.
Re: What does a kilowatt hour look like?
#24Re: What does a kilowatt hour look like?
#25Less acronyms please. (COP, PV, and even EV)
COP: 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).
Re: What does a kilowatt hour look like?
#261kWh 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.
1kWh as aluminium is about 66g (assuming 15kWh per kilo manufacturing input) or about 4 drink cans.
25 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...)
Re: What does a kilowatt hour look like?
#27Re: What does a kilowatt hour look like?
#28"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?
Nope. 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.
Good 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#Der...
Re: What does a kilowatt hour look like?
#29Given 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.