3 ms·
You can't really have an international grid on the scale you describe, due to transmission losses. If you take a conductor, even though for short distances the
by jfim 14y ago
You can't really have an international grid on the scale you describe, due to transmission losses. If you take a conductor, even though for short distances the material it has negligible resistance, it comes out to be a limiting factor for long lengths (thousands of kilometres).
If you look at Joule's first law, which says that the heat produced by a piece of wire is proportional to the square of the current times the electrical resistance of the wire (ie. I^2*R), you'll notice it doesn't say anything about voltage. This is why power transmission lines for long distances usually have high voltages (~100kV) or even higher ones(the transmission lines where I live are 735kV). Unfortunately, there is a limit as to how much voltage that can be put, due to other problems caused by the high voltage itself (coronal discharge, arcing, etc.).
This is why electricity (per kilowatt, retail) costs me one third of what it costs my friend in Los Angeles; it's not technically feasible to send our low cost electricity all the way to there while still turning a profit. Note that this completely changes if there is high temperature[1] superconductivity, but at this point, it's not exactly doable[2].
[1] High temperature, in this case, essentially means without liquid nitrogen and other relatively exotic cooling methods. Your living room would be considered high temperature, for example.
[2] The current superconductor with the highest transition temperature is HgBa2Ca2Cu3O8, at 133K (-140C).
- maxerickson 14y agoYou are a little pessimistic: http://en.wikipedia.org/wiki/Pacific_DC_Intertie http://en.wikipedia.org/wiki/Pacific_DC_Intertie http://www.abb.com/cawp/seitp202/25b65cc026636ebfc1257574004f0232.aspx http://www.abb.com/cawp/seitp202/25b65cc026636ebfc1257574004... (The first link describes the system that reduces energy costs in LA by carrying it in from the Columbia river system, the second one is from the company behind the technology and discusses their plan to send 6 Gigawatts over 2,000 km in China) The economics are certainly less favorable as distance increases.
- jfim 14y agoNot really. Current residential electric rate here is 0.0541$/kWh, compared to 0.232$/kWh in LA. I am sure they would enjoy having this cheap electricity, but they're too far from here. Furthermore, to take his example of solar electricity from the Sahara to the UK, the line of sight distance between both is over 3000km[1], includes underwater segments and is more than 25% longer than the longest HVDC link(the Rio Madeira, at 2375km). Can electricity be sent over long distances? Sure, but not intercontinentally, or even intracontinentally if you're looking at, say, New York to Los Angeles. [1] http://www.wolframalpha.com/input/?i=distance+between+the+sahara+desert+and+london%2C+uk http://www.wolframalpha.com/input/?i=distance+between+the+sa...
- maxerickson 14y agoI take the existence of the interlink as evidence that it lowers prices (this seems like a reasonable definition of profit here). Maybe it only works due to the regulatory situation in California. It would take some more information to decide how much of the price difference is due to the interlink. I don't particularly think intercontinental systems are in the near future, but I don't think "a little pessimistic" was outlandish. What if ABB can push their tech 50% further?
- danpalmer 14y agoThe cable I mentioned in the UK that is carrying up to 2.2GW is an HVDC cable. That will supposedly work.
- maxerickson 14y agoSure, HVDC obviously works over considerable distances. The problem jfim is talking about is that each additional length of cable increases the price of the delivered electricity (because a longer cable is less efficient). So given a particular method of generating power, a particular consumption market and a set of cable characteristics, there is a distance limit on viable projects.
- jfim 14y agoThere are also other costs, other than only transmission losses. If you're crossing multiple countries (which would be the case in such a long cable), there needs to be a clear path for the cable to take(ie. pay people to use their land to put a power line on), multiple legal jurisdictions, a higher rate of failure because of the increased cable length, more maintenance, etc. From speaking with an EE friend of mine, he mentioned that for long distances, DC is more appropriate and most of my (limited) knowledge revolves around AC. So it might technically be feasible, even though it would be politically hard to do so.
- danpalmer 14y agoI am not an expert in this. The speakers however are, and are the ones researching the new cables. The answer is that they need to be High-voltage DC. The high voltage to increase efficiency, and the DC in order to make them compatible around the world.