[abakker]

Without directly answering the question of total capacity, solar does have a few problems that are unlikely to ever make it an "existential threat" to commercial power generation, especially when done at home.

1. It is highly dependent on the amount of sunlight an area gets. This might seem obvious, but is also problematic in that it is difficult to build the correct capacity for climates that vary significantly over seasons. Solar is well and good in Los Angeles, since the weather is very consistent, and the amount of sunlight doesn't vary hugely over the year. In Seattle though, if you were to install enough capacity to be useful in the winter, you would drastically over-produce in the summer. Over production of solar is currently a problem, and can have significant detrimental impact on the overall power grid. Typically, when it drastically over-produces, it can cause blackouts. This is amplified by the fact that solar produces its maximum amount of output at a time when people don't consume the most electricity. This may eventually be mitigated by better batteries, and alternative power storage systems like Vanadium Flow systems.

2. Solar has a maximum capacity, and will likely always need to be mixed with other "on-demand" power generation systems. At present, these are Coal or NatGas generation stations that can be ramped up to meet spikes in demand. Effectively, these plants allow us to store energy chemically in the gas/coal and burn it on demand. very few renewable energy sources have the ability to be ramped up to greater production over short period of time. Again, this problem could be mitigated by substantial battery installations, where a small amount of excess generation from solar could charge batteries that could be drawn on to deal with spikes in demand.

3. Power transmission is always going to be a problem. Solar is less and less viable the further toward the poles you go. Though we could generate power in the southwest, there are practical limits to how far power can be transmitted over existing lines without too much loss.

In all, though it would be possible for Solar to operate a given house or building with on-site generation. It is very unlikely to threaten the power companies, which give us a low-cost, reliable, and simple solution that is capable of meeting our needs.

[djrogers]

<quote> Typically, when it drastically over-produces, it can cause blackouts. This is amplified by the fact that solar produces its maximum amount of output at a time when people don't consume the most electricity.</quote>

This is a pretty regionalistic viewpoint - in many parts of the world the peak solar production and peak electrical usage are highly correlated due to air conditioning use.

[abakker]

That is very true - I should have been more specific. Solar doesn't generate in the evening hours, when everyone is still consuming their AC, their Lights, their TV and many home appliances.

Pumping workloads (AC, Refrigeration) are fairly static loads on the grid though and don't account for very much (~7%) of the overall energy consumption (http://www.eia.gov/consumption/residential/).

The trouble with solar only really happens when their are spikes, either in over production, or over consumption.

[malyk]

This is where on-site battery storage "fixes" the issue.

Most people are away from home during the day while their battery charges and then come home for a few hours at night when the battery powers the house.

Now, there are certainly cases, perhaps even many of them, where it wouldn't really work out. But for me it's the ideal setup. My wife and I live in a 1300ft2 house and use 250ish kwh a month in electricity including recharging an electric car a couple times a week. A 1.6 kwh system would cover almost all of our energy needs. Couple that to battery storage so we could use the energy we generate during the day when we are at home at night? Perfect!

[huxley]

Is there any region of the world that uses more energy during non-daylight hours? Everywhere I've lived, peak demand is daytime.

[kiiski]

Where I'm at, today the sunrise was at 09:10, and sunset at 14:30. Peak energy usage is in the evening.

[abakker]

You'll see many power companies that offer incentives like this - https://www.pacificpower.net/ya/po/otou/ooh.html

it is still daytime, but typically not peak solar hours.

[gohrt]

Is it not possible to "turn off" a solar panels? Worst case, you have to throw a tarp over some of your panels for summertime.

[abakker]

It is certainly possible. The challenge when doing this is that the solar installation that you put in to be able to generate during the winter months ends up being MUCH bigger, and more costly. Most of the ROI models on solar assume that when you do this, you'll be able to "sell" your excess capacity back to the grid.

Many/Most systems I have seen in southern California contribute energy to the grid directly, and power is still purchased through the grid like normal. When your panel is generating, the power you generate and consume balance out and your power is "free", but you don't consume power straight from your panel (a flawed representation of how electric flows, I know).

The challenge with these implementations are that the grid itself handles the power generated by panels, and can't turn them off. The reason they do the installations this way is so homeowners stay connected to the grid to even out their energy spikes, but also to save the homeowner the cost of battery storage systems. In this case, the grid acts as "storage" by accounting, rather than by real storage of energy.

[maratd]

This is easily solved if the utilities get properly involved.

My utility has been pushing a thermostat that they provide at no cost and will even give you a bit of cash for installing. The reason is that this thermostat is hooked up to the utility through the internet and can be shut off by them during a spike or an emergency.

I just got new smart electric meters installed too.

If those meters were a little bit smarter, connected over the net, and had the ability to restrict flow ... they could easily install devices on a per house basis that would protect the grid. That would put the ball back in the homeowners court and the homeowner can implement a solution to shut off the panels when the utility isn't interested in purchasing power back.

[marvin]

Just install an outdoor radiator (electric heater), perhaps with fans if outdoor temperature is very high, and burn off the excess electricity. Switch the radiator on or off by computer. Dirt simple and cheap.

[findjashua]

Re #2: is it be possible/feasible for panel owners to sell the extra electricity back to the grid?

[abakker]

This is precisely how most home solar installations work. They provide power directly to the grid and offset the power that they still draw from the meter. Most solar installations feed power to the grid at the meter, so the power company still knows how much power you consume, they just also see how much you provide and then only charge you the difference.

it is this setup in particular that is problematic for spikes in generation, since the power company can't just disconnect your solar array if it is adding too much power at a low demand time.