I heard this suggestion a long time ago, not sure where. It's pretty extreme and there are lots of factors against it, but this is one forum which should at least consider it.
The idea is to run a BIG DC ring main around the earth, traversing many equatorial parts where the solar energy (and in some places wind) is moderately reliable. That way you can have relatively constant energisation through renewable sources. Spurs running north and south would feed the energy to consumers.
You put up the first 5 trillion USD's and we'll go from there....
energisation
This just points out the main problem with how people think about renewables. The power will be generated out in the boonies and used in the city. I2R losses will gobble up most of the power heating bird feet along the way. DC is the worst possible scenario for how you would transmit this power. If we are going to make this ring it should be 250kv AC or higher (let the generator buy the inverter) to keep the current down, then the question becomes 50 or 60hz???
Cattle Fart Repository a better idea. // tbh
On 20 May 2004 16:05:18 GMT, snipped-for-privacy@aol.com (Greg) Gave us:
There are 1MV DC runs that are less leaky than AC runs, and have less losses as well.
The problem with DC is local downconversion. And safety interruption capability. That's about it.
At the local level, AC is going to be around for a long time.
| This just points out the main problem with how people think about renewables. | The power will be generated out in the boonies and used in the city. I2R losses | will gobble up most of the power heating bird feet along the way. DC is the | worst possible scenario for how you would transmit this power. If we are going | to make this ring it should be 250kv AC or higher (let the generator buy the | inverter) to keep the current down, then the question becomes 50 or 60hz???
I vote for 54.77225575 Hz, plus or minus a few.
On Thu, 20 May 2004 12:26:13 -0700 DarkMatter wrote: | On 20 May 2004 16:05:18 GMT, snipped-for-privacy@aol.com (Greg) Gave us: | |>This just points out the main problem with how people think about renewables. |>The power will be generated out in the boonies and used in the city. I2R losses |>will gobble up most of the power heating bird feet along the way. DC is the |>worst possible scenario for how you would transmit this power. If we are going |>to make this ring it should be 250kv AC or higher (let the generator buy the |>inverter) to keep the current down, then the question becomes 50 or 60hz??? | | | There are 1MV DC runs that are less leaky than AC runs, and have | less losses as well. | | The problem with DC is local downconversion. And safety | interruption capability. That's about it.
There are no zero crossings to easily interrupt and extinguish arcs.
| At the local level, AC is going to be around for a long time.
And Japan will stay split between 50 and 60 for a long time, too. If any place would be motivated to make a change, they would. But it's just not practical. So it's clear any merits in one particular system design over another just do not count in the decision. It's all money. That's why it was important to choose the right design at the start. Unfortunately, the people who did were not well equipped.
------------------ How come we have major DC links in countries all around the world? Look up Manitoba Hydro's DC link from the Boonies to civilisation as well as the Northwest Power pool (US) DC link from Oregon to points south as examples. These transmit over long distances at voltages of the order of
+/-800kV and where applied are more economical and efficient than an AC line (In some cases DC is usabel where AC is not). The systems feeding and drawing from these links are conventional AC. They have drawbacks as they do require large and expensive converter stations and are best point to point due to lack of effective DC circuit breakers and the possibliity of a DC "grid" By the way 250KV is not considered extra high voltage by any means.However, as to the original proposal-It probably assumes HVDC but ignores the whole process of conversion, gathering and transmission of energy in a feasible way. A round the earth link does run into more than a few problems- including the whole business of the concept of a ring main for such a link (also those long underwater cables don't come cheap). Pablo's $5 trillion would be a small downpayment. Oh yes, an AC round the world link is no more feasible. EHV AC cables are even more expensive than DC cables.
On Fri, 21 May 2004 05:17:47 GMT, "Don Kelly" Gave us:
But IS quite sufficient to keep line losses low.
Could work, but the voltage would have to be something out of this world.
Capacity?
To be comercially viable, the line would have to carry a lot of power. Conventional 400/500 kV lines have capacities in the Gigawatt region. This line would need a capacity of tens of GW. Let's assume 10 GW. Furthermore, the current would probably be in the kA region. Let's assume 1 kA. This means we need a voltage of 10 MV.
Being environmentalists, we need two conductors to cancel the magnetic field. A single conductor could work from an engineering point of view, but Greenpeace will get upset, claiming the fish will get disoriented.
How big would the cable be?
If we make this a Edison system, the voltage to ground would be 5 MV. If we allow 10 kV/mm of insulation we need a cable with half a metre of insulation. We will have a hard time finding us a ship to lay this monster cable...
What about voltage drop?
Let's assume the distance around the world is 40 000 km as the crows fly. In practice the cable would have to be much longer, 50 000 km or more. The longest distance you would ever transfer electricity would be half of that, i.e. 25 000 km. The most likely conductor material is aluminium, which has a resistivity of 30 ohm/(km mm2). Assuming 1000 mm2 conductors, we have a total resistance from one side of planet Earth to the other of 30 x 25 = 750 ohms. Remember that there are two paths as it is a ring circuit, but there are also two conductors. We therefore need to divide the resistance by two and then multiply by two. :)
The voltage drop is 750 ohms x 1 kA = 750 kV. This is quite reasonable as we have a nominal voltage of 10 MV.
(In practice, you would use a lower voltage and larger conductors.)
The cost?
If we get the cable cheap, we might just get away with a few million USD per km. If we assume 5 million, we get 50' km x 5'' USD = 250''' USD. 250 American billions could buy it :)
Would it be profitable?
Let's assume that the line operates at full capacity 24/7, we incur no cost from operation or losses and we charge 1 cent for each kWH that is transferred. Thus, we make 100' USD per hour and as there are 8760 hours in a year, we would make 876 million USD per year. Even with 0% interest rate, it would take us three centuries to reach break even...
/Clas-Henrik
P.S. HVAC wouldn't work since the distance is too great, especially under water. The longest underwater AC link is 100 km I think. (British mainland to the Island of Man.)
Ohhh! Ohhh! Can we get the engineering for that? Let's see, 10% of 5 trillion would be a very nice addition to the company bottom line - even if it was spread out over 25 years or 50 years.
Aside from the ruinous high cost of consulting engineers to design the thing, practical problems with this would include:
Right now this part of the world is looking at a much less ambitious connection to take advantage of the fact that when it's supper hour in Ontario, the kids are just getting out of school in Alberta - thereby spreading out the peak loads, and also allowing Manitoba to sell hydro power in both directions. Not 5 trillion, but I'm sure 5 billion dollars would get used pretty quickly.
Bill
Whatever happened to those solar power satellite guys? You know, the ones who were going to beam a couple of terawatts of gigahertz RF to sites in deserts. I thought at least one of the concepts being discussed decades ago was
remote power site > big RF transmitter > space reflector > big RF reciver > local power distribution
There's probably as many reasons why this wouldn't work as the global ring main, but since I know less about RF than HVDC I have the idea that the problems are more manageable?
Bill
generator buy
including the
Come on: the "taps" would be just like the terminals. They would be you "basic" (and expensive) DC-AC bi-directional conversion stations.
Over land it would be just like the situation today with AC networks: Power is "wheeled" from end to end rather than sent along a un-tapped transmission line. For the necesssary underwater links, the present technology just isn't up to the problem.
Amen. The intra-continental links are not yet fully developed (or "debuged".)
How fat do you think that environmental impact statement will be? You will still have the problem of getting the power into the cities.
FPL has been trying to get the permits to run a power line through a swamp here for well over a decade with no end in sight.
This can be done-in theory- it is expensive and each such tap requires both a rectifier and inverter as well as AC reactive sources. That is each would be a "back to back station" If you wanted feeder spurs to be DC then the equivalent of 3 AC circuit breakers would require the equivalent of 3 converter stations. as well as the availability of a strong AC system at each tap point. At some point "feasibility" degenerates into a no go situation. This point is reached long before consideration of a "round the world link".>In the case of a cross-continent tie -the tap points would be reduced to back to back converters such as those in Japan, Alberta/Saskatchewan and Eel River New Brunswick (all of which are DC for stability or frequency conversion needs ). At these "taps" the local systems do need some muscle.
transmission
Again, in present AC systems, circuit breakers at reasonable cost and effectiveness are very important. How far apart must the 'taps" be to make it either economically or technically worth while to use such a tapped DC system? (yes- there is in fact such a system if I remember correctly- the NW power pool DC link which ties strong areas of generation to major loads and is in parallel with AC ties
It all boils down to the merits and demerits of any proposed situation: Load here---Generation here---what's the best way to get them married? In some cases, don't bother- intercontinental transfer may have no net benefits and a lot of costs even if technology was up to the task.
Don Kelly snipped-for-privacy@peeshaw.ca remove the urine to answer
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