“We already live in a solar powered world!”

[mountainsoft]

if I’m doing the math right it says the US would need an area 196 miles by 196 miles to be powered with nothing but solar.

Apparently, there are 200 square miles of parking spaces just in LA County. That's just one county in one state.

"Some 200 square miles of Los Angeles County were dedicated to parking as of 2010."

https://www.citylab.com/transportation/2016/01/map-la-county-parking-200-square-miles/423579/

Nationwide parking spaces consume somewhere around 3000-12000 square miles.

"Absent hard numbers Mr. Ben-Joseph settles on a compromise of 500 million parking spaces in the country, occupying some 3,590 square miles, or an area larger than Delaware and Rhode Island combined. If the correct number is 2 billion, we’re talking about four times that"

https://www.nytimes.com/2012/01/08/arts/design/taking-parking-lots-seriously-as-public-spaces.html

The land is already being used, we just need to install solar panels above them. Of course, that doesn't count roof tops, or dedicated solar farms on vacant land.

 

[NW-Bound]

I decided to do some simple calculations of my own to check Musk's claim.

According to EIA, the per capita annual energy consumption in the US is 390 million BTU. That number is everything, from coal to nuclear, petroleum products, natural gas, biomass, hydro, wind, etc... In short, every source of energy that the US is currently consuming is in the above number.

Converting the above number from BTU to kWh, we use 90,600 kWh/year/person, or 250 kWh/day/person. Now, if you look at the TedTalk presented by MacKay, you will see the 250 kWh/day is what he shows on the chart at 5:24.

Now, the question becomes "How many solar panels do we need to generate 250 kWh/day?"

Of course, that is highly dependent on the weather, the season, the location, etc... But I will take my location here in the SW, which is the best location for solar panels in the US. And instead of using the daily requirement, I will use the annual requirement, assuming that we somehow can afford enough batteries or some form of energy storage to save energy from summer production to use in the winter.

According to nrel.gov, a 1 kW worth of PV panels at my location will produce 1800 kWh/year. For 90,600 kWh/year, we will need 50 kW worth of PV panels per person. Now, how large is this array of PV panels?

A high-efficiency panel of 61"x41" in production now can produce 350W. That's 17.4 sq.ft. for 350W, or 50 sq.ft. per kW. For 50 kW of panels, each person will need 2,500 sq.ft.

However, the number of 1800 kWh/year quoted by nrel.gov assumes that the panels are tilted up 30 deg at my location. The tilted panels then have to be spaced out to prevent partial shading. The ground area increases from 2,500 sq.ft. to 2900 sq.ft for each American.

The US population is 327 million. The total area for solar panels is then 948.3 billion sq.ft., or 34,015 sq.mi. That's a square of 184 mi x 184 mi. That's a bit larger than Musk's 100 mi x 100 mi square. It's not too far from what Midpack computes at 196 mi x 196 mi.

If we want to put the panels closer to the points of use to avoid the cost and losses of transmission lines, then we will need even more panels, because the above number is based on the best location in the US.

For example, in Portland, Oregon, a 1 kW of panels will have an annual production of 1180 kWh, instead of 1800 kWh. In Dayton, Ohio, it will be 1400 kWh/year.


PS. I made an error in computing the spacing of rows of panels to prevent shading. The sun angle in the winter is a lot lower than I thought, even here in the SW. However, I will not present the new number, because all we care here is just a rough order of magnitude.

 

[NW-Bound]

Carrying on a bit further, let's see what it costs for 50 kW worth of PV panels per person.

I can buy the above 350W panel at about $150 each. For 50 kW, we will need 143 panels at a cost of $21K. To this we need to add the cost of structural mounting, in addition to various other hardware and electronics.

The hardest and most expensive thing will be the battery. Right now, lithium batteries still run about $200/kWh. Storing a day's worth of 250 kWh for each person will cost $50K/person/day. And these batteries do not last forever.

Technically, it is quite feasible. Financially, it's something else.

 

[Koolau]

Carrying on a bit further, let's see what it costs for 50 kW worth of PV panels per person.

I can buy the above 350W panel at about $150 each. For 50 kW, we will need 143 panels at a cost of $21K. To this we need to add the cost of structural mounting, in addition to various other hardware and electronics.

The hardest and most expensive thing will be the battery. Right now, lithium batteries still run about $200/kWh. Storing a day's worth of 250 kWh for each person will cost $50K/person/day. And these batteries do not last forever.

Technically, it is quite feasible. Financially, it's something else.

On a topic 90 degrees to this discussion, dear son was telling me today that one of his 14 month old batteries (in his PV, off the grid system on Big Island) caught on fire the other day. Not a major disaster, but the fire dept. came out and unhooked it and told him to call his electrician. Apparently, the warranty applies. Just thinking, though, when EACH of us has our own system and is responsible for its maintenance and replacement, how reliable will it be. Now, we curse HECO because we get a dozen half second to 5 minute outages per year (one 18 hour "gap" back in '08). What would it be like if your system goes down every couple of years or so and you are not qualified to fix it. DS is very do-it-yourself, but he knew better than to mess with the battery on his own. I forgot to ask him how long he was without electricity. I'm sure it was days.

If we let utilities handle collection and distribution of solar, I think the roughly $70K (or more) per person described above will mushroom as the utility makes it "reliable."

Oh, and tell me again how we get some of those 390 million BTUs collected from the sun into a Boing 777. YMMV

 

[Chuckanut]

So storage batteries in our houses will sort of be like having gasoline stored in the garage, except that they can self ignite?

 

[Nemo2]

https://www.cato.org/blog/crescent-dunes-another-green-flop

Oops.

 

[NW-Bound]

On a topic 90 degrees to this discussion, dear son was telling me today that one of his 14 month old batteries (in his PV, off the grid system on Big Island) caught on fire the other day. Not a major disaster, but the fire dept. came out and unhooked it and told him to call his electrician...

Could you find out more details about this battery catching on fire? What is the brand?

If we let utilities handle collection and distribution of solar, I think the roughly $70K (or more) per person described above will mushroom as the utility makes it "reliable."

Well, I showed that the material cost for 50 kW worth of panels is $21K. The total cost will of course be higher, and that is still without batteries.

For example, a quick look shows me that a local installer is advertising a 10kW system for $25K before tax credits. And that's a rooftop system. If you need to build a structure for a large 50kW array which is 5x larger and will not fit on a typical roof, it is going to cost quite a bit more.

And remember that for a couple, you need 100 kW.

Oh, and tell me again how we get some of those 390 million BTUs collected from the sun into a Boing 777. YMMV

Eventually, when we run out of oil, we will have to use biofuel for planes. Air travel will be a lot more expensive when powered with vegetable oil.

https://www.cato.org/blog/crescent-dunes-another-green-flop

Oops.

I posted about this project in the other thread. It would work, but the problem is that it needs to sell its output at $0.135/kWh to be economically viable.

A lot of "stuff" works. It's just too expensive. Let them eat cake.

 

[aja8888]

https://www.cato.org/blog/crescent-dunes-another-green-flop

Oops.

Well, what did anyone expect from government sponsored pipe dreams?

 

[Alan]

So storage batteries in our houses will sort of be like having gasoline stored in the garage, except that they can self ignite?

The 2 Lithium Ion batteries we have installed in our garage as part of our solar system are the same type I believe as we have in our Prius and I haven’t seen many reports of Prius car batteries catching fire.

 

[Koolau]

Could you find out more details about this battery catching on fire? What is the brand?

Son just left on a trip, but i'll try to find out. By the way, the battery did not burst into flames, but it did get very hot and was smoking. It was totally fried and useless. His batteries are mounted outside on the wall of his house. Don't know if that could have potentially caused a house fire or not. I have heard of batteries actually causing fires, so I would assume most folks place them accordingly. YMMV

 

[NW-Bound]

Son just left on a trip, but i'll try to find out. By the way, the battery did not burst into flames, but it did get very hot and was smoking. It was totally fried and useless. His batteries are mounted outside on the wall of his house. Don't know if that could have potentially caused a house fire or not. I have heard of batteries actually causing fires, so I would assume most folks place them accordingly. YMMV

Besides Tesla, there are a few other makers of home storage battery systems. There are two lithium battery chemistries in use in home storage systems that I have seen. One group uses lithium NMC (nickel manganese cobalt), while the other uses lithium iron phosphate (LFP or LiFePO4).

Lithium NMC is the type used in Tesla cars and powerwalls. It has higher energy density than LFP, but the battery is prone to rupture and fire if abused. In a good design, that should not happen unless there is a failure of the electronics that monitor the battery and keep it in a safe operating envelope.

On the other hand, the LFP type has a lower energy density, but is much safer, and has a more benign failure mode if abused.

LFP battery is what I use in my DIY system. The storage battery installed in Alan's home is also of this type.

 

[Koolau]

Besides Tesla, there are a few other makers of home storage battery systems. There are two lithium battery chemistries in use in home storage systems that I have seen. One group uses lithium NMC (nickel manganese cobalt), while the other uses lithium iron phosphate (LFP or LiFePO4).

Lithium NMC is the type used in Tesla cars and powerwalls. It has higher energy density than LFP, but the battery is prone to rupture and fire if abused. In a good design, that should not happen unless there is a failure of the electronics that monitor the battery and keep it in a safe operating envelope.

On the other hand, the LFP type has a lower energy density, but is much safer, and has a more benign failure mode if abused.

LFP battery is what I use in my DIY system. The storage battery installed in Alan's home is also of this type.

Son's system uses LFP. If you want the brand, I can PM you.

 

[NW-Bound]

Thanks. When your son knows more about the failure mode, if he can share it that will be great. For example, if it is the battery itself that fails, or a failure of the electronics that leads to the battery failure.

If the battery itself fails, that's not good. If it's the electronics, then the manufacturer could have done better by designing in redundant monitoring circuits, so that the system becomes "fail-safe". This means that the system will shut itself down if it detects its own failure.

 

[JoeWras]

I think the example of the 100x100 square mile solar farm is to simply make a point about how much solar energy is available, not to advocate actually building such a thing to power the entire nation.

Anybody with 1/2 a brain can see that having one location to power the entire country is wrong on so many levels - military vulnerability, transmission problems, a local natural disaster at the site, etc. etc. etc. I imagine we could develop a list of negatives big enough to paper over a 100x100 sq mile surface.

Then why did they choose the SW desert? Why not put that overlay on the Northeast? There was some subtle messaging going on in that demonstration.

And as others have mentioned, transmission issues and losses are no joke.

As for rooftop... I got a real problem with my house. It is completely wrongly oriented for decent solar. And I'd have to cut some 60 year old trees. That would tick off a lot of people.

 

[Zathras]

I find that 250 kWh/person/day really fascinating and a bit scary.
My wife and I have a total electricity use of about 14,000 kWh/year.

This includes all heating, appliances, local transportation.
This works out to roughly 20kWh/person/day.
In Minnesota, this can be covered with roughly 40 panels (315W/panel).

This doesn’t include the energy used to transport the food and goods we use.
I am guessing much of the balance is energy used in transportation and industry.

If we used gasoline fueled vehicles, say 40mpg cars, we would use about 300 gallons of gasoline, which converts to 10,000kWh of electricity. Instead, we used about 3000kWh of electricity.

Technically, producing as much energy as we use in the US is easy.
The logistics of delivering it to the places that need it, when they need it, are definitely more challenging.
And as always, a combination of power supply methods makes it easier.

 

[JoeWras]

I find that 250 kWh/person/day really fascinating and a bit scary.
My wife and I have a total electricity use of about 14,000 kWh/year.

We're well under 10k.

This 250kWh number includes everything from industry, to your vehicle usage, to streetlights, etc. So maybe that makes some sense, as you pointed out. I keep hearing how power hungry industrial concerns are. Household usage is a blip compared to everything else.

 

[NW-Bound]

Yes, the 250 kWh/day/person comes from the total energy consumed in the USA, divided by the head count.

That includes all that is used to grow, produce, and transport food, goods, and provides services that we use. It is a lot more than what we use in our home, and burn in our personal cars.

Also, let's not forget fuel burned by airplanes and cruise ships. And all those fancy rockets.

 

[NW-Bound]

This includes all heating, appliances, local transportation.
This works out to roughly 20kWh/person/day.
In Minnesota, this can be covered with roughly 40 panels (315W/panel).

In Minneapolis, the above array of 12.6 kW produces 33 kWh/day in December.

That falls way short in providing heating in addition to charging an EV.

 

[NW-Bound]

Before I installed a DIY solar system to provide a portion of the energy that I used, my residential consumption was 16,800 kWh/year. No EV charging.

That works out to an average of 46 kWh/day. The highest daily consumption was 100 kWh/day in the hottest day of summer. The lowest was 24 kWh/day.

Lest you think I use too much energy, I agree but like to point out that my utility company says I use about 80% that of my neighbors.

Now, with the solar, it is reduced to about 60% of the previous consumption, or about 1/2 that of my neighbors.

 

[Koolau]

Thanks. When your son knows more about the failure mode, if he can share it that will be great. For example, if it is the battery itself that fails, or a failure of the electronics that leads to the battery failure.

If the battery itself fails, that's not good. If it's the electronics, then the manufacturer could have done better by designing in redundant monitoring circuits, so that the system becomes "fail-safe". This means that the system will shut itself down if it detects its own failure.

Son said it was just one of his batteries. Apparently not his system.

 

[Zathras]

In Minneapolis, the above array of 12.6 kW produces 33 kWh/day in December.

That falls way short in providing heating in addition to charging an EV.

My apologies, I took for granted that “on an annual basis” would be assumed.
I should have stated it explicitly.

 

[NW-Bound]

Son said it was just one of his batteries. Apparently not his system.

We will need to wait to see if the manufacturer has to replace some hardware in addition to the battery when the system is serviced.

It is of course very possible that the battery itself failed, but the electronics can also be out-of-whack and overcharged/overdischarged the battery causing the failure.

My apologies, I took for granted that “on an annual basis” would be assumed.
I should have stated it explicitly.

I knew you were talking about annual production. I wanted to point out that it takes a lot of storage to save the summer production for use in the winter.

I did not know you are living in Minnesota. The 14,000-kWh/year consumption is unbelievably low. I could not have imagined that. You must have an extremely energy-efficient home, if that also includes your EV charge. I cannot do that here in the SW, even without charging an EV.

 

[Zathras]

...
I knew you were talking about annual production. I wanted to point out that it takes a lot of storage to save the summer production for use in the winter.

Oh absolutely! If I were in a more temperate climate I’d probably shoot to be off grid. In Minnesota that isn’t feasible without a second or third source of power. I’ve seen some do it with solar, wind and a wood burning stove, but it is rare.

I did not know you are living in Minnesota. The 14,000-kWh/year consumption is unbelievably low. I could not have imagined that. You must have an extremely energy-efficient home, if that also includes your EV charge. I cannot do that here in the SW, even without charging an EV.

Our house was designed to be net zero so yes, it is very efficient. If designed that way, it is not very difficult to do. It does take planning and a team that communicates.
Sadly, most builders aren’t interested in doing so.
More and more are though

 

[Midpack]

Our house was designed to be net zero so yes, it is very efficient. If designed that way, it is not very difficult to do. It does take planning and a team that communicates.
Sadly, most builders aren’t interested in doing so.
More and more are though

Agreed. We looked into it at our former city/state and again now that we’ve moved south 750 miles - there aren’t any contractors interested here either. Of course if there was demand, there would be contractors. Unless you live in large city in CA, AZ, TX, WA, OR and a few other exceptions - building net zero would take a lot of initiative and a hold harmless agreement from a contractor. Maybe some day...

 

[EastWest Gal]

Could you find out more details about this battery catching on fire? What is the brand?



Well, I showed that the material cost for 50 kW worth of panels is $21K. The total cost will of course be higher, and that is still without batteries.

For example, a quick look shows me that a local installer is advertising a 10kW system for $25K before tax credits. And that's a rooftop system. If you need to build a structure for a large 50kW array which is 5x larger and will not fit on a typical roof, it is going to cost quite a bit more.

And remember that for a couple, you need 100 kW.



Eventually, when we run out of oil, we will have to use biofuel for planes. Air travel will be a lot more expensive when powered with vegetable oil.



I posted about this project in the other thread. It would work, but the problem is that it needs to sell its output at $0.135/kWh to be economically viable.

A lot of "stuff" works. It's just too expensive. Let them eat cake.

Not to mention that without fossil fuel it will be nearly impossible to produce enough biofuel for the jets. Agriculture is highly dependent on fossil fuel for machinery and the production of nitrogen fertilizer.