Dr. Strangelove’s numbers are certainly in the ballpark. I ran the numbers using other published figures for capacity factor in Arizona, plus the average power consumed per household (about 14,000 kWh), and I get about 8kW nameplate value for a solar system to do that. That is, if everything is theoretically optimal. If you aren’t tracking the sun, don’t have a south-facing roof or your cells can’t be mounted at the optimum angle, you might need a little more. Add in a bit extra to cover the losses the panels undergo over the years. A 10 kW system would be fine, but 8 kW would be okay.
I did the math also to see what it would take to power a Tesla model 3 driving the national average of 13,500 miles, and for Arizona get about 2 kW hours nameplate capacity for a solar system dedicated just to that, assuming you are net metering and can pull power from the grid when you need it. So if you also want to charge an electric car, add anothet 2 kW.
As for whether you can fit one on your roof… if you have a south-facing side, measure the area of that roof. An 8 kW solar system uses between 45 and 54 sq meters of roof area, or about 500-600 sq ft of roof space. Don’t count the whole roof - just the south facing part, because that’s what you’d use.
Here’s some pictures of solar systems of different sizes so you can get a sense of what you need. The first house has 8 kW installed.
I run my central AC in 100-degree summers in Las Vegas on solar just fine. On a clear day I can generate 70kWh or more. Here’s today’s output:
That can handle both of my AC units (upstairs and downstairs) running full blast on a 100-degree day and charge my car at the same time.
It certainly helps that I have a basically ideal roof for solar, with the main plane of the roof facing directly south.
It’s only April and hasn’t gotten super hot yet, but from my recent usage you can see how my net usage is substantially less than my solar output, even with the AC and car charging going.
I should also point out that one of Tesla’s products is a solar roof (solar panels that look like shingles) combined with “Powerwall” a large capacity battery, same tech as their cars. IIRC that’s 14.5KWh storage, enough to ensure the systems still work when the sun goes down. For larger homes, install 2 or more.
When you say A/C runs 20 hour a day - is that always powered? Or does it run for a while, create cool coils, stop for a while and blow cool air from the existing coolant, then power up again?
The other point is - how regionally diverse is power? A lot of Canadian power generation, for example, is hydroelectric. Ontario has a decent amount of nuclear power. I have no idea, but I’m guessing California’s power is more natural gas than coal - gas is a lot cleaner. Plus, generators running flat out, like regular cars cruising at highway speeds, are cleaner than an automobile in stop-and-go traffic. Recently constructed (natural gas) generators are probably far cleaner than antique power plants still burning coal. Plus, California likely imports a decent amount of hydroelectric power from Oregon or Washington, and California has a high concentration of electric cars. I suspect a lot of the much older coal powerplants are in the east and midwest. If nothing else, piping in natural gas is a lot more efficient than handling piles of coal, so I can see many utilities taking the opportunities they can to convert.
Another benefit of electric cars is that they usually charge overnight. Typical power consumption peaks during the day, and so cars charging at night in fact help the system by creating demand during slow times - so power companies can use their peak capacity plants (usually newer gas generators) longer and get better return on their investment; and the total grid capacity does not need to be expanded that much. (I for example, schedule charging at 1AM. By then, I’m not using the dryer, hot water, stove, or dishwasher, most of the lights are out and likely the A/C is running a lot less too.)
Currently it’s showing 0.276 mTCO2/MWh, which is the same as kg/kWh of CO2. My car goes about 4 miles/kWh, so I get 14.5 mi/kg CO2.
A gallon of gas burns to produce 8.9 kg of CO2. So a 40 mpg car is only getting 4.5 mi/kg. The EV is about 3x as efficient here. And as mentioned, I can pay extra for pure renewable plans.
Nuclear power would be great if it didn’t produce nuclear waste and didn’t inevitably result in things like 3 Mile Island, Chernobyl, and Fukushima.
There is no “good” source of power at this point. Currently for power generation in the U.S., nukes account for about 20 percent, coal 19 percent, natural gas 40 percent, and all types of renewables (solar, wind, geothermal, biomass, and hydroelectric) combined are 20 percent. Renewables unfortunately do not provide enough energy and also do not provide enough consistent energy. Solar only makes power when the sun is shining. Wind only makes power when there’s enough wind blowing. Hydroelectric ends up destroying the ecosystem and starves everything downriver of water.
It used to be that if you needed a bunch of electricity, your only two realistic choices were coal or nukes. Both are on the decline. Nukes are fading out due to costs, nuclear waste issues, and fear of disasters. Coal is fading due to environmental reasons. Natural gas has swelled to take up the slack, but natural gas still causes climate issues.
Better batteries would solve a lot of problems, but better batteries have been the Holy Grail for the last several decades.
I know someone who has rooftop solar (in Maryland, FWIW). The point isn’t to provide power 24/7/365 but to provide power during peak hours during the day since that is when electricity usage is the greatest. Their system is still tied to the grid and the grid provides power at night or at times during the day when the solar power system isn’t meeting the home’s demand. Extra power that is generated is sold back to the power company, but not at the same rate that they charge to sell power to you though.
Like @friedo the system does not have batteries and is not intended to.
There are tax incentives that help to make the system more affordable. Without those I’m not sure how the economic side of it would work out, but as it is, with all of the incentives the system will end up paying for itself and then some. There is a lot of money up front, but the overall cost savings make it cheaper than using the utility company’s power in the long run.
And while it doesn’t completely eliminate grid power, it does reduce the load on the grid rather significantly. Maryland is currently roughly 45 percent nuke power, 25 percent coal, 20 percent natural gas, and 10 percent “everything else”.
I agree that there is no good solution but nuclear is by far the least bad. Not a single person died from 3 Mile Island. One confirmed death from fukushima. We could have a 3 Mile Island disaster every year and it would still be better than fracking, coal, air pollution, and global warming that we’re experiencing now.
Nuclear power didn’t “result in” Fukushima. The biggest tsunami in recorded history resulted in that. No form of infrastructure was spared, and most of the infrastructure failed a lot worse than the nuclear power plant did.
And better designed, so that they can be “walk away safe”, in that if everything goes out, the reactor still goes to a safe state that it can maintain indefinitely.
That’s one of the easiest parts, really.
The total amount of spent fuel nuclear waste generated over the entire lifetime of all US reactors would barely fill a football field. As far as volume goes, it’s not really an issue. It’s pretty much just politics that makes it difficult.
And there are many new generation plants that not only create far less waste, but can also consume the waste of previous generations.
A whole bunch of what we call “waste” is actually extremely valuable. We spend ridiculous amounts of money in medical and research reactors to make these isotopes that are just sitting there in the spent nuclear fuel.
What are the Iranians generating in their centrifuges?
Father in law No.1, a geologist, was in favor of sealing nuclear waste in concrete and dumping it into the Marianas trench, where he assured me that it would end up deep in the Earth.
Probably Uranium 235. Not sure the relevance of the question.
The isotopes I am talking about are things like Plutonium-238 to fuel RTG’s for spacecraft and probes, Molybdenum-99 which produces Technetium-99m, one of the most used radioisotopes, or Thorium 229 for medical purposes (eventually turns into Bismuth 213, which can be very useful for targeted cancer treatments.)
Stuff like that, stuff that is only produced in nuclear reactors, not in centrifuges.
There are places in the ocean that are subduction zones that would eventually draw the materials in.
Problem with that is the nature of “eventually”, which could be longer than the storage containers can survive those conditions, and also, it’s not going that deep, but rather into the mantle, where a significant amount of it is then recycled by volcanoes. Not sure how it would play out, and it would certainly be quite diluted, but you could end up with volcanoes spewing out radioactive waste.
And then there’s the problem that you are throwing away perfectly good fuel for future generations of reactor.
Still not all that much. The vast majority comes from decommissioning power plants, and the rest is more classified that way legally, rather than based on how radioactive it actually is.
Most of it actually could be recycled and reused in future nuclear installations with little difficulty. It is more the politics than the technology or engineering that is in the way.
Or you can just bury it. We’ve got plenty of space in coal mines that we have dug out already. It’s not nearly radioactive enough for anyone to try to make a dirty bomb out of, much less a nuclear device.
And, once again, future generations of reactor will have much less material needed for their construction, and so have much less contaminated material that needs to be dealt with.
