Perfect electrical conduction

[SagaLore]

What are power lines made of - aluminum or copper?

I just read that there is over 7% energy loss from transfering electricity along long distance power lines.

We have a natural gas furnace and stove. The pilot lights are always going out. Last year we were gone for a weekend and came back, it was very cold, the pilot had gone out early and everything was covered in soot. In ATOT I just read about a house exploding, then some members replied that they've also seen houses in their town blow up as well...

Why do we bother with all these different kinds of fuels for heating and cooking?

Large power plants have a higher efficiency for creating electricity. Instead of piping natural gas or bottling propane or refilling tanks with heating oil, why don't we use all of these at power plants then force all buildings to use elctricity.

The way I see it, we need to find more efficient electric-to-heat elements for this. We also need to find an alloy to reduce the energy loss in power lines. Also, I think its time we stop running lines along poles, and put these lines in conduits in the ground. They would stay cooler, wouldn't get knocked over by vehicles and strong winds, wouldn't be such an eyesore.

Discuss.

 

[BrownTown]

i guess its probably because natural gas heats better then electric heating. Also, you have the existing infrastructure, if everyone switched to electric heating you'd have to improve the power grid to take the extra load (and also build the extra power plants)

 

[smack Down]

electric-to-heat is almost 100% efficient. Although larger electric generation plants are more effcient then smaller ones but the extra effcienty comes from turning heat into electricty and not generating the heat.

 

[CycloWizard]

Aluminum wires are used because copper wires are way too heavy for above-ground wiring. That, and copper is a lot more expensive.

As BT said, natural gas is used for heating because it's very efficient. I'm not sure what the relative expenses of each type of energy (gas vs. electric are) and they'll vary from region to region, but at some point it was financially advantageous to heat with gas. In most places, it's probably still cheaper. If someone throws me some numbers as to how much electricity costs per kWh and how much gas is per BTU (or similar), then I could do some calculations and tell you which is more financially efficient.

 

[Mark R]

Power lines are made of aluminium.

Copper is a better conductor, and was used when electricity was first being commercialised - however, aluminium is considerably lighter, hence requires much cheaper/smaller towers. In fact, most high voltage power cables are aluminium with a steel core - the steel is a terrible electrical conductor but it is very strong, so allows longer spans between towers. The massive cost savings from using lighter cables far outweigh the efficiency advantages of using copper.

The next big thing is carbon fibre or glass fibre reinforced aluminium cables - lighter reinforcments mean more weight available for aluminium (so less resistance, less heat and more efficiency), and carbon expands less than steel when heated - so while steel reinforced cables have a max temp of about 200 F, before they sag unacceptably, carbon-fibre reinforced cables could potentially be used at 300-400 F. Yes, the high tension cables really do get that hot - that's why birds don't sit on the hot wires. If they tried, they'd burn their feet.

While transmitting electricity is overall reasonably efficient - 7% loss seems a reasonble figure - generating it is not. When nat gas is burned in a power plant, as much as 75% of the heat energy is discarded, and only 25% is converted into electricity (55% for a state of the art CCGT nat gas plant). Coal is a bit better at around 35% for an older plant and 40% for a state of the art plant.

From this, it should be clear why electricity is so much more expensive than nat gas or coal - you've thrown most of the energy of the original fuel away at the power plant. This is also why it's far more environmentally friendly to burn gas at home for heat, than to burn gas at a power plant and heat with the electricity.

Yes, pilot lights are wasteful - they've not been used in domestic equipment for several years. Indeed, if your furnace is so old that it uses a pilot light, instead of an electronic ignition system - it's bound to be a highly inefficient model and likely to be due for replacement soon anyway. However, even an old inefficient boiler which converts 75% of the heat in the gas into heat in your home is better than electricity. A modern nat gas boiler which retains 98% of the heat is even better.

All electic heating elements are pretty much 100% efficient - there's essentially nothing to be improved. The main reason for encouraging electrical heating is because it's easier to manage pollution generated at a power plant, than in individual homes. The other reason, is because electrical heat pump heating could be used. Heat pumps move heat from one area to another (e.g. the ground under your lawn, into your house) - they can potentially transfer 3 times as much energy as they consume. In this case, burning gas to generate electricity to power heat pumps is better than burning gas directly.

Burying cables isn't done much because it's incredibly expensive - digging deep trenches/tunnels, you need heavy armoured, insulated cable (instead of bare cable which you can run between towers), and you have a serious problem with heat. On towers, the cables are cooled by wind and natural air circulation - buried cables need careful design. In some cases, you need to use hollow cables and pump coolant through them to stop them from overheating.

 

[SagaLore]

Originally posted by: CycloWizard
Aluminum wires are used because copper wires are way too heavy for above-ground wiring. That, and copper is a lot more expensive.

As BT said, natural gas is used for heating because it's very efficient. I'm not sure what the relative expenses of each type of energy (gas vs. electric are) and they'll vary from region to region, but at some point it was financially advantageous to heat with gas. In most places, it's probably still cheaper. If someone throws me some numbers as to how much electricity costs per kWh and how much gas is per BTU (or similar), then I could do some calculations and tell you which is more financially efficient.

What I'm getting at - is pushing natural gas along a pipe system and burning it onsite more efficient than burning it at a centralized site, then sending that electricity to the home and converting it to heat?

Instead of running natural gas pipes in the ground, they could have ran electrical lines. Instead of pressure regulators and dedicated hookups, they could have just used the main electrical system. Look at all of the overhead. I'm not just looking at consumer prices but total economic cost.

I looked up electrical conductivity of metals, and came across this page:

http://www.overclock.net/faqs/49435-metals-thermal-electrical-conductivity.html

Looks to me that Lead is superior at transfering electricity. So why not run lead cables inside conduits in the ground.

 

[CycloWizard]

Originally posted by: SagaLore
What I'm getting at - is pushing natural gas along a pipe system and burning it onsite more efficient than burning it at a centralized site, then sending that electricity to the home and converting it to heat?

Ah, I gotcha. Yes, it's very much more efficient to pipe it into your house. Whenever you produce electricity using a heat cycle, your maximum theoretical efficiency is 50%. That means the electric power you get out is less than or equal to 50% of the heat produced by burning your natural gas. By piping it straight into your house, you recover 100% of the heat when you combust the gas. This cuts your heating bill in half at least, probably really decreasing it by a factor of 3.

Looks to me that Lead is superior at transfering electricity. So why not run lead cables inside conduits in the ground.

No one wants to build anything out of lead anymore. People see lead and get all scared because it's POISONOUS! Oh noooes! It's barely harmful unless you eat a fairly large quantity, but people are scared of everything these days. Another reason is because lead is difficult to extrude, so forming very long wires would be extremely difficult and expensive.

 

[SagaLore]

Originally posted by: Mark R
When nat gas is burned in a power plant, as much as 75% of the heat energy is discarded, and only 25% is converted into electricity (55% for a state of the art CCGT nat gas plant). Coal is a bit better at around 35% for an older plant and 40% for a state of the art plant.

It seems rediculous that we can't deisgn a power plant that gets better efficiency than that. The initial phase would be to burn the ng and run turbines, then the second phase would be to use the after-heat to run boilers which then create steam to run more turbines. The third phase would be to reclaim as much heat as possible from the waste water using heat pumps.

Or is that basically what the "state of the art" plants already do?

 

[Mark R]

So why not run lead cables inside conduits in the ground.

Because lead is 12 times worse than copper at conducting electricity.

CCGT - stands for combined cycle gas turbine. Which as it's name suggests, means that a conventional gas turbine (powered by burning gas) is combined with a steam turbine. The exhaust from the gas turbine is used to heat water into steam to power the steam turbine.

The problem is that the 2nd law of thermodynamics places a limit on how efficiently heat can be converted into another form of energy. This limit is called the Carnot efficiency - and it depends on the temperature of the heat source (e.g. steam in the boiler), and the temperature of the heatsink (cooling towers).

In the case of gas turbines the exhaust is very hot (the 'heatsink' is the air), so it's worth capturing the heat as you can convert it with decent efficiency.

In the case of coal your heatsink is warm water in the cooling towers - you won't be able to power another turbine with that heat and get good efficiency. The difference between modern and older coal plants is in the heat of the boilers. The very latest coal plants, convert the coal into gas, and then run a CCGT on the gas - but this tech is very expensive (probably as expensive as a nuclear plant).

 

[CycloWizard]

Originally posted by: SagaLore
It seems rediculous that we can't deisgn a power plant that gets better efficiency than that. The initial phase would be to burn the ng and run turbines, then the second phase would be to use the after-heat to run boilers which then create steam to run more turbines. The third phase would be to reclaim as much heat as possible from the waste water using heat pumps.

Or is that basically what the "state of the art" plants already do?

Even the Carnot efficiency (maximum thermodynamic efficiency that can ever be achieved with a heat engine) is 50%. Achieving 80% of that (40% overall efficiency) with modern coal plants is actually pretty darn good.

 

[SagaLore]

Originally posted by: CycloWizard
Another reason is because lead is difficult to extrude, so forming very long wires would be extremely difficult and expensive.

When I was in the boy scouts, we would recover as many of the lead bullets from a firing range as we could, and melted them down fairly easy. Then while the metal was still warm, it was very easy to mold and bend into shapes.

It doesn't have to be very long cables. It can be moderate-length pipes with some type of puzzle like hinge, and can be laid down quickly. They can do a quick weld to fuse the "joints" together. The conduit these lay in doesn't have to be pipe - it can be box-like with a bolted top for easy access.

 

[SagaLore]

Originally posted by: Mark R

So why not run lead cables inside conduits in the ground.

Because lead is 12 times worse than copper at conducting electricity.

Based on the table I found, that's not true. But I could be misreading the table. The author is measuring it in electron negativity in the Pauling scale, whatever that means...

 

[Mark R]

Originally posted by: SagaLore

Originally posted by: Mark R

So why not run lead cables inside conduits in the ground.

Because lead is 12 times worse than copper at conducting electricity.

The author is measuring it in electron negativity in the Pauling scale, whatever that means...

No idea either, but it's nothing to do with electrical conductivity. What you want is electrical resistivity.

Resistivity

(Note that the table is resistivity - lower means better conductivity).

 

[CycloWizard]

Originally posted by: SagaLore
When I was in the boy scouts, we would recover as many of the lead bullets from a firing range as we could, and melted them down fairly easy. Then while the metal was still warm, it was very easy to mold and bend into shapes.

It doesn't have to be very long cables. It can be moderate-length pipes with some type of puzzle like hinge, and can be laid down quickly. They can do a quick weld to fuse the "joints" together. The conduit these lay in doesn't have to be pipe - it can be box-like with a bolted top for easy access.

That's possible. However, the added installation expense would probably wipe out any financial benefit you'd get from using them. I'm just guessing because otherwise someone would probably already be doing it. Power lines are expensive, so I'm sure power companies take every measure they can do decrease their cost.

 

[SagaLore]

Originally posted by: Mark R
No idea either, but it's nothing to do with electrical conductivity. What you want is electrical resistivity.

Resistivity

(Note that the table is resistivity - lower means better conductivity).

Okay thanks. But, the table you just showed me indicates that Lead is less resistive than aluminum and copper.

edit:
Ah nevermind, the power is in negative. The table is least resistive to most resistive.

 

[Bassyhead]

I think many power lines are actually steel-reinforced aluminum.

Simply put, natural gas is just cheaper per joule (per unit of energy) than electricity is. I suppose it's due to cheaper distribution (lack of transformers and less maintenance) plus natural gas doesn't have to be generated, it's just pumped out of the ground. Natural gas burns very cleanly. I believe most NG furnaces are in the middle 90% range in terms of efficiency. In large facilities like universities or office buildings, even air conditioning systems utilize natural gas by running the boilers in the summer and using the hot water to run cold absorption generators, which is much more efficient than using electricity to run compressors in refrigerant-based chillers.

 

[BrownTown]

umm, no natural gas is actually waaay more expensive then electricity, but if you already have natural gas heating you are pretty much stuck with it unless you wanna buy a new heating unit. Obviously it makes alot more sense to burn natural gas in your home for heat then in a plant and then send the electricity, but it makes even mroe sense to use cheaper power sources like nuclear plants to produce electricity, then send that to your home. The preices for natural gas have skyrocketed recently, so it may have being economicly effecient a few years ago, but it deffinitely isn't anymore. But what i was alluding to was that you have higher QUALITY heat then with electricity. Most electric systems don't warm the air as fast as natural gas, although the new heat pumps claim they do, but i've never used one so i can't validate that claim.

 

[eilute]

Well I imagine it is very efficient to convert natural gas and oil into heat.

It is also good to have energy diversity. This just makes everything more reliable.

 

[DrPizza]

A decent modern furnace is going to burn natural gas with at least 90% efficiency... only 10% of the heat is lost.
You've already lost close to that in powerline transmission alone.

Also, someone mentioned something about pilot lights above. Most modern furnaces in homes don't have a pilot light. However, (unless I'm mistaken) most (gas) hot water tanks actually do have a pilot light.

BrownTown mentioned that natural gas is more expensive than electricity... this is true in some locations. There are at least a few places where the cost of electricity is very cheap due to hydro-power. But, for the most part, I think natural gas is cheaper.

(if you're looking for the least expensive method to heat a house, I believe coal furnaces win, hands down.)

 

[Bassyhead]

Originally posted by: BrownTown
umm, no natural gas is actually waaay more expensive then electricity, but if you already have natural gas heating you are pretty much stuck with it unless you wanna buy a new heating unit. Obviously it makes alot more sense to burn natural gas in your home for heat then in a plant and then send the electricity, but it makes even mroe sense to use cheaper power sources like nuclear plants to produce electricity, then send that to your home. The preices for natural gas have skyrocketed recently, so it may have being economicly effecient a few years ago, but it deffinitely isn't anymore. But what i was alluding to was that you have higher QUALITY heat then with electricity. Most electric systems don't warm the air as fast as natural gas, although the new heat pumps claim they do, but i've never used one so i can't validate that claim.

Natural gas is more expensive than electricity, how? I don't know about now but in 2000 electricity cost a national average of 8.03 cents/kWh and natural gas cost 68.8 cents/therm. Translated to BTU, which is a standard unit of energy, a single BTU of electricity cost $23.53 and a BTU of natural gas cost $6.88.

Edit: The dollar amounts are for millions of BTUs, but the comparison still stands

 

[BrownTown]

natural gas prices are much much higher then they were in 2000,ill go find the number for 2006 if i can

 

[Jeff7]

Yeah, electric heat is really expensive. We used to have nothing but electric heat at home, and sometimes in the really cold months, our electric bill would approach $500 for a month. It's just a ranch house too, nothing huge or extravagant, located in eastern Pennsylvania. We got a wood pellet furnace sometime in the past two or three years or so. That thing is able to heat the house for about $125 a month when it's really cold out. Quite a good deal. And the wood pellets are made from waste sawdust that would otherwise be put in a landfill.

 

[BrownTown]

well, gas prices are 2-3 times what they were in 2000, but yeah, i looked it up, and on average electric should still be more expensive. Id image that way in the middle of the country where they have to pipe gas 1000 miles its probably more expensive to use gas, but in most places probably not.

 

[silicon demon]

this is my area of expertise.

1. ) power lines are aluminum: because aluminum is cheaper, and much lighter. those long power lines are heavy.

Why do we bother with all these different kinds of fuels for heating and cooking?

2.) because many are more efficient and waste less energy than electricity. (For example: electricity is generated by spinning large magnets. why burn coal or natural gas...to generate steam...to spin magnets...to generate electricity...to send down a long wire and lose 7%...to convert back into heat through a heating element, to heat your water?) You could just burn the natural gas at your house and heat the water.

3.) to place large electrical lines in the ground would be cost-prohibitive. Besides, power lines are open to the air (hence, open-air conductors) and dissiapte heat better so utility companies can use smaller wires (i.e. less expersive all the way around). Wires in the ground get hotter because the conduits trap heat.

4.) the only alloy that will reduce energy loss (it's actually called 'voltage drop') would be a room-temperature super conductor. When they invent those, they will change the world more than the internet did.

 

[f95toli]

You do not need a room temperature superconductor.
There are a few commercial projects where nitrogen cooled high-temperature superconductor cables are used. These cables have been tested for several years in small-scale installations and apparantly the power companies are now satisfied with the reliability etc so they are starting to use them

However, at the moment the main reason for using superconducting cables is not to avoid losses in the cable. The reason is simply that in cities like e.g Tokyo they need to distribute more energy to certain areas but there is not enough space in the conduits for more copper cables. Superconducting cables can carry much more current than copper cables and can be installed in existing conduits as long as there is room for cooling equipment at the end of the cable.


More info can be found at http://www.amsuper.com