Because DC is produced electricity, and it takes burning around 10x the joules or more of hydrocarbons to match that power
Comment on TIL the cost of transporting energy around
andrewrgross@slrpnk.net 3 months ago
Why is DC power so much more expensive than pipelines?
Nomecks@lemmy.ca 3 months ago
sparkyshocks@lemmy.zip 3 months ago
Pipelines are absurdly efficient because moving liquid or gas through a pipe is absurdly efficient per kilogram per kilometer, and the energy density of fossil fuels is absurdly high.
A Tesla supercharger v4 can deliver 500 kW of power. BYD has launched chargers that can deliver 1000 kW (aka 1 MW) to a single car. Naturally, each kW of power is capable of delivering 1 kWh per hour.
What is the equivalent flow rate in gasoline? 1 gallon of gasoline contains the equivalent of 33.4 kWh (1 L contains 9 kWh). So 1000 kW would be the equivalent of 30 gallons per hour (110 L/hr), or 0.5 gallons (1.85 L) per minute. That’s 5% of the rate of a typical gasoline pump in the United States.
Plus exposed high voltage wires need to be maintained in weather and around vegetation, so they have high operating costs. Then there’s higher capital costs of making sure that there are transformers and safety equipment that step the voltage up and down and sync with the rest of the grid.
In the end, it really is that power lines aren’t capable of carrying nearly as much energy as the chemical fuels that flow through a pipe, so on a per joule/kwh basis, there’s less economy of scale from power lines.
wewbull@feddit.uk 3 months ago
One problem with that comparison is that, sure gasoline has a really high calorific value. Shame you put it in a machine with 20% efficiency.
Tobberone@feddit.nu 3 months ago
I would think that the graph would be rather different had it been “last kilometer”? I’d expect to see electricity at the bottom there.
sparkyshocks@lemmy.zip 3 months ago
Yes, the numbers change for shorter distances. There’s some loss in loading up a fuel tank and driving it to the station. But again, the high energy storage capacity of chemical energy still makes a huge difference.
If a loaded semi gets 8 miles per gallon of diesel, then moving a tanker full of 10,000 gallons of gasoline 200 mile (320 km) s will burn 25 gallons of diesel in order to transport 10,000 gallons of gasoline. Even with less efficient trucks (let’s say 6 mpg for 33.3 gallons of diesel burned), it’s still pretty efficient in terms of “losses,” of about one third of one percent of the original volume of fuel consumed. Of course, diesel is more energy dense than gasoline, especially gasoline mixed with ethanol, so the efficiency might drop to 99.5% instead of 99.7%, but we’re still talking about a pretty fundamentally efficient operation.
The real efficiency gains of electricity over fossil fuel (or any chemical fuel) comes from the more efficient motors. An electric car that goes 3 miles (5 km) per kwh is the equivalent of going 100 miles per gallon (42 km/L) of gasoline. A heat pump that has 300% efficiency only needs to transmit 1/3 as much electrical energy as would have been necessary for bringing fuel to a combustion-based heater.
So if you start breaking it down by actual use case, you might be able to make some gains back to mitigate the higher cost of transporting electricity across large distances. But it still remains that all the other methods are very efficient, too.
DrunkenPirate@feddit.org 3 months ago
All those fuel stations you have to build and operate… And the energy losses to move your car to those fuel stations.
Indeed, this paper seems to calculate around the goal of making powerlines look costly by cutting it to a dedicated process step. If you look at it end-to-end process from production to consumption transportation, it very likely looks different
andrewrgross@slrpnk.net 3 months ago
Wow, that’s a lot of food for thought.
MeThisGuy@feddit.nl 3 months ago
- joules for thought
sparkyshocks@lemmy.zip 3 months ago
Food energy tends to be measured in kcals though
brucethemoose@lemmy.world 3 months ago
Power transmission is hard.
The wire, the complex components, keeping it all in phase and steady and not exploding, the maintenance…
I cannot emphasize this enough. People tend to trivialize this when talking about remote production, but moving electricity long-distance is basically the hardest part. And pipes really are dead-simple in comparison.
It’s also why local production is so appealing.
andrewrgross@slrpnk.net 3 months ago
I was aware conceptually that it’s really complicated, but where are the costs going? Is this due to labor costs? Material costs? something else? What makes it so expensive to build and to operate, especially compared to pipelines.
brucethemoose@lemmy.world 3 months ago
I am not a power engineer, but I do know the capital costs for the wire and components all along the way is massive. They’re complicated, and they require a lot of expensive (and probably carbon intensive) materials.
Basic physics dictates it. Its more complicated than small scale DC/AC current with negligible transmission time you’re likely thinking of.
Maintenance is a pain, too. HV wires (especially the crazy DC ones) are extremely, extremely dangerous and basically can’t be near anything.
I’m not sure about installation labor costs vs a pipeline though.
sparkyshocks@lemmy.zip 3 months ago
capital costs for the wire and components all along the way is massive
That’s true of pipelines, too. It’s just that the sheer quantity of energy contained in those chemical bonds of chemical fuel is massive, so amortizing the up-front capital costs across how much energy can actually move through that pipe or cable in its lifetime tends to favor a pipe full of chemical energy, on a per kWh (or per joule) basis.
chocrates@piefed.world 3 months ago
They are also pretty lossy too right? Some percentage of the energy you are moving is lost to heat
mrgoosmoos@lemmy.ca 3 months ago
DC power is pretty much ready to use.
pipelines are raw material with an energy capacity of which a much lower percentage can be used due to conversion inefficiencies