Generating electricity from ice? - Page 1
Forum section: electronics / general

author: Artlav
author_rank: Frequent Contributor
timestamp: November 09, 2014, 07:06:33 pm
content: Ice.Lots of ice around, such is the nature of Russia.So, how about making electricity out of it?Just having some fun with a thermoelectric generator i made.A TEG is said to produce electricity from heat, but since it is running on a temperature difference, it's equally valid to say that it produces electricity from cold.However, i don't think i ever heard it described that way.And for a good reason - the energy is, in the end, coming from the furnace that heats up the house.Are there circumstances where it would make sense to say that the power is coming from the cold?Even in places where heat and cold co-exist, it's more precise to say that the heat is carrying the energy (be it from fire, solar, geothermal, nuclear, body heat, etc), and not the cold.

author: SeanB
author_rank: Super Contributor
timestamp: November 09, 2014, 08:45:40 pm
content: However the energy to the hot side comes from your central heating........... Will not work if you do not pay that bill and the heat is turned off.

author: Macbeth
author_rank: Super Contributor
timestamp: November 09, 2014, 09:42:04 pm
content: I believe running air conditioners in reverse is more efficient at generating heat in the home than the usual resistive electric heating methods. Kind of like air-con is so energy inefficient at reducing room temps compared to the power in, it's actually pretty good using the heat exchanger the other way around?I'm not sure, I live in the UK and use a gas boiler for our radiators in the winter. Far cheaper than electricity.I have a portable AC that I only really use in the rare summer heatwaves we have. It is a godsend when temps, and worse, humidity, are high.

author: PlainName
author_rank: Super Contributor
timestamp: November 09, 2014, 10:16:11 pm
content: QuoteYes, it is. I used to have a fan heater in my office and replaced it with aircon specifically for the heating part (in summer it's cheaper to open the windows, although I have used cooling once or twice). Cost about £300 and paid for itself in 2-3 years (hard to be precise because they bump the energy prices every year, but even so my bills are still coming in low).It is not for everyone - takes a while to get up to speed from cold, so you wouldn't want it if you're just heating up the place to watch a TV prog, say. But it is much moresmoothheat, so you don't feel extra cold when the extra hot fan blowing up your trousers turns off.

author: rob77
author_rank: Super Contributor
timestamp: November 09, 2014, 10:18:12 pm
content: Quote from: Macbeth on November 09, 2014, 09:42:04 pmAC is a heat pump, nothing less nothing morethe problem running the AC in reverse is the efficiency.... you can't extract enough heat from the freezing cold air with acceptable efficiency.... that's the reason why the heat pumps designed for heating houses are pumping the heat from a exchanger buried in the ground or submersed in a well.

author: Artlav
author_rank: Frequent Contributor
timestamp: November 09, 2014, 10:25:38 pm
content: Quote from: SeanB on November 09, 2014, 08:45:40 pmYep, like i said below the video.I mostly wondered if it would make sense to say the energy is coming from the cold.I.e. if you made liquid nitrogen, you stored a fraction of the energy spent making in it.So, when it vaporises it can spin a turbine and give some of that energy back (at 1% system efficiency or so).However, sources of energy don't naturally occur in the "cold" variety, AFAIK.Thus, the question.Quote from: Macbeth on November 09, 2014, 09:42:04 pmYes, in general.However, when it's -30*C outside, it tends to get difficult.Even if it is designed to run that cold, it still will be only marginally more efficient than a resistive heater, at many, many times the complexity.We are talking about refrigerating the cold outside air to even colder temperatures to bring heat inside, and that is a difficult task.So, at some point the complexity outprices the gains.

author: IanB
author_rank: Super Contributor
timestamp: November 09, 2014, 11:17:18 pm
content: Quote from: Artlav on November 09, 2014, 07:06:33 pmIf you put your generator outside with a black painted aluminium panel facing the sun on one side and the cold ice on the other, you could generate some solar powered electricity.

author: Rufus
author_rank: Super Contributor
timestamp: November 09, 2014, 11:50:41 pm
content: Quote from: IanB on November 09, 2014, 11:17:18 pmDoes that mean it is powered by dark?

author: suicidaleggroll
author_rank: Super Contributor
timestamp: November 09, 2014, 11:53:52 pm
content: Quote from: Artlav on November 09, 2014, 10:25:38 pmNo, it doesn't, because it's not.Quote from: Artlav on November 09, 2014, 10:25:38 pmNo, you make liquid nitrogen by pulling energy OUT of in, not by putting energy INTO it.Quote from: Artlav on November 09, 2014, 10:25:38 pmThe liquid nitrogen is not vaporizing itself and spinning the turbine. The energy required to vaporize the liquid nitrogen and spin the turbine is coming from the heat in the surrounding air. You're not extracting energy from the liquid nitrogen, the cold temperature of the liquid nitrogen simply gives you a conduit through which you can extract energy from the surrounding (read: warmer) air.Quote from: Artlav on November 09, 2014, 10:25:38 pmThat's because there's no such thing. Cold, by definition, is the absence of energy, not the presence of "cold energy".Think of it like a waterfall. High temperatures are like the water in the river at the top of the falls, low temperatures are like the water in the river at the bottom of the falls. The temperature (height of the water) is its potential energy. The higher it is, the more potential energy it has, but you can only extract that energy by allowing it to fall to a lower height.Same with a TEC, it allows you to extract some of the thermal energy on the hot side as it transitions from hot to cold. A perfect TEC wouldn't heat the cold side at all, it would just act like a sink on the hot side and all of that thermal energy would turn into electricity. Since a TEC is not perfect, some of that heat makes it through and warms up the cold side as well.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: November 10, 2014, 12:00:13 am
content: Quote from: Rufus on November 09, 2014, 11:50:41 pmIt's powered by solar radiation, black just happens to have a higher emissivity than shiny silver, which makes it more efficient.

author: calexanian
author_rank: Super Contributor
timestamp: November 10, 2014, 12:29:56 am
content: Dave just recently did a video on the Seebeck effect. Also Thermopile generators. The voyager probes have one each that are amazing.

author: Rufus
author_rank: Super Contributor
timestamp: November 10, 2014, 02:35:09 am
content: Quote from: suicidaleggroll on November 10, 2014, 12:00:13 amI think you are taking the thread too seriously.

author: LukeW
author_rank: Frequent Contributor
timestamp: November 11, 2014, 04:42:48 am
content: You've got the ambient environment on the "hot side" of the system, and something that is cold below room temperature (eg ice, or liquid nitrogen or whatever) on the cold side of the system.The energy comes from the hot side... so you could say that the energy comes from the temperature of the room.However, you've spent energy to create a system that is colder than room temperature, putting energy in to make the ice or whatever.So you can't (of course) get a free lunch in the thermodynamic sense.You can do the same thing using a small low-temperature-gradient Stirling engine, with the heat source at room temperature and ice on the heat sink, or a thermoelectric pile like you've used.