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Comment by stavros | Hacker News Reader

You're assuming that, in the future, we'll still have huge, centralized plants. With solar, it's very possible that we'll have small stations in each town or area, and only need to balance between them infrequently, greatly reducing the amount of energy we need to carry across large distances.

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I think municipality-sized microgrids are a big part of the future, but they still don't remove the requirement for a grid, simply because of weather. Most renewables are very dependent on local weather conditions: you don't get solar when it's cloudy, and you don't get wind when it's calm. The grid needs to equalize power generation and consumption, and it's probably more economical to have a few transmission lines running between cities and to remote power generation facilities than it is add the utility-scale batteries needed to power through a week of cloudy weather.

I could however see a future where cities refuse to subsidize rural homeowners and communities, disconnect from the country-level grids that exist today, let them de-energize and fall into disrepair, and then maintain only a few transmission links over major transportation corridors to connect with other major cities.

Sure, but when you only need to transmit the difference, and even that only to charge batteries, the transmission lines can be much smaller.

That's not true, and stems from mistakenly thinking of electricity as a fluid instead of working through the math of the laws of electrodynamics themselves.

With AC, there is no net current anyway - nothing physical is being transmitted any substantive difference. The actual electrons travel on the order of 0.2 microns per 60Hz cycle, and then move back the other way. [1]

In reality, in the absence of fundamental electric components like resistors/capacitors/transformers, all points of a circuit have the same voltage and same current. The transmission lines are just connecting different cities into the same circuit, there's nothing flowing between them. This allows your solar array in the Mojave Desert to power your data center on the Columbia River, but there aren't fewer electrons traveling between them just because you also have a hydro power plant on the Dalles. The load from all devices on the grid is shared across all generation sources.

[1] https://en.wikipedia.org/wiki/Drift_velocity

> and only need to balance between them infrequently

I think it's exactly the opposite. There will frequently be a need to balance them.

With wind and solar in the mix, generation will fluctuate with the weather. In a given area, it could be cloudy one day and sunny the next. Or windy one day but not the next. And consumption won't be correlated with that, so that creates an extra source of mismatches between demand and consumption within each area.

Transmission is one way to solve that. You could also solve it with storage (within every area), but that's probably less efficient and/or more expensive.

It's easier for me to bring you some food when you're running out than to bring you food every single meal.

Sure, but you need the same road to get there regardless of how many hours a week it gets used.

It's a trade off. More transmission lines means less overbuilding and less storage. Really it's an optimization problem that will be solved on a case by case basis given geography and so on.

For infrastructure it’s the opposite. You have to buy a food truck big enough to feed everyone on the worst day of the year. And at that point you may as well use it every day because you already paid for it.

Inertia will keep the status quo for a very very very long time. Combine that with heterogeneity (i.e. not everyone will be using local solar plants) and that the distribution concerns noted still apply to local plants outside your house and it doesn’t seem like it’ll go away without some kind of central planning forcing the issue.

You're oversimplifying. US residential power is currently supplied by a pair of 120 V wires, but most of the stuff in your house only uses one leg of that pair. That's alright because it's AC, and the ground wire doesn't actually need to carry any significant current. Power just returns time-lagged through the same wire when the voltage changes.

If you switch to DC, that doesn't work any more. Every amp in requires an amp out. The wiring in your house just got a lot more complicated, not to mention the wiring in the local grid.

Also, running your neighborhood on 85 V (the DC equivalent to 120 V) isn't exactly efficient. Even large ground-mounted transformers only provide power to 10-15 houses at most, and pole-mounted transformers may only service one house. The main power to your neighborhood is 7.2 kV because it's more efficient to to send power at high voltage and low current.

It's not impossible for a residential solar setup to output thousands of volts, but it's not easy and it's pretty constraining for designs. There's also a world of difference between that voltage at the street and that voltage in the house. Things go wrong in the house.

> You're oversimplifying. US residential power is currently supplied by a pair of 120 V wires, but most of the stuff in your house only uses one leg of that pair. That's alright because it's AC, and the ground wire doesn't actually need to carry any significant current. Power just returns time-lagged through the same wire when the voltage changes.

This isn't how it works.

Maybe my model of how AC works is wrong, but my understanding is that neutral wires exist and are necessary in addition to safety earth, even though neutral and ground are eventually tied.

> You're assuming that, in the future, we'll still have huge, centralized plants.

You're assuming that we won't.

> With solar, it's very possible that ...

How nice the world would be we could all lean on "well because it is possible it must eventually happen."

- Things will be the same, except for X.

- Maybe other things will be different too.

- Oh, so everything will be different?!

> You're assuming that we won't.

That's really not how I read that comment.

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