Is it practical to generate all US power by solar PV?

[jim hardy]

In another PF thread it was proposed to build a centralized PV farm of 1000 gigawatts , which is the order of magnitude of US installed generating capacity. It'd cover 1/10 the area of New Mexico, Arizona and Nevada.

Mostly desert and dry US states:

Arizona: 295254 km^2
Nevada: 286367 km^2
New Mexico: 315194 km^2

Sum: 896815 km^2

If we would tile only 10% of this land with PV panels we'd generate
897 GW (on average). And then there are dry, inhospitable areas in
Utah, Colorado and Texas if we would ever need more.

√ (10%of 896815 km^2) = 299.5 km per side, 186 miles per side, not far from the 150 stated earlier in the same thread.
Close enough for thought experiments.

You can't drive maintenance trucks over solar panels so the dimensions will expand to accommodate roadways.
Unless they're elevated to serve as rooftops with access from below.
Stormwater runoff from a 150 mile square rooftop will be a challenge, Phoenix area has been known to get 6 inches in a storm.
http://www.fcd.maricopa.gov/Weather/Rainfall/raininfo.aspx

It'd be interesting that's for sure.
Myself, i am far more afraid of huge storage batteries than of reactors. I wouldn't be go anywhere near them.

Maybe @anorlunda will assess the practicality of moving so much power over so much distance.

 

[anorlunda]

That's quite an ambitious thought. I'll give it some thought, but here are a couple of preliminary points.

• Northeast utilities have determined that they could take up to 20% of their power from the Midwest. That does not say that they could not take more, but that it has not been studied. This idea is an order of magnitude beyond the boundaries of what has been studied. On an engineering scale, compare it with a proposal to build a bridge from Galveston to Tampa over the Gulf of Mexico, or bridges across the English Channel and the Bering Straight.
• Having said that, a lot of power can be transmitted a long way using HVDC But it would be very expensive, maybe trillions. Also it needs hundreds of thousands of miles of lines. Expect one landowner lawsuit per mile, so maybe more trillions for lawyers.
• It makes a great rhetorical point to locate all that PV power in one state, but it makes no engineering sense. The sun also shines on the other 47 of the lower 48, and distributed facilities would be far more reliable. Why not distribute the locations?

 

[jim hardy]

It makes a great rhetorical point to locate all that PV power in one state, but it makes no engineering sense. The sun also shines on the other 47 of the lower 48, and distributed facilities would be far more reliable. Why not distribute the locations?

Distributed rooftop solar.. has utility industry is really worried .
http://www.eei.org/ourissues/finance/Documents/disruptivechallenges.pdf

 

[mheslep]

Total installed capacity of US today is 1 TW, not 2. Average consumption is, naturally, much less that 1 TW.

As I said, with *all* energy use converted to electricity for a future scenario, including transportation, space heat, industrial, etc, the total US power load is 2 TW. Just backing up the existing US electric load at .5 TW for 7 days still requires some billion tons of battery. Currently, there is not a single utility scale battery project with even one day of run time, not anywhere in the world. The idea of backing up a large country with batteries, powered by solar, is nonsense. Power to gas or power to liquids has some small pilot plant traction, but no more.

 

[mheslep]

...
If you want to go all solar, you have to consider total energy consumption, which is about 3 TW...

Right, current primary energy use. Converted to electric transportation, heat pumps, etc, 2 TW is about right.

 

[nikkkom]

1/10 works for the US I guess, in Europe you still need the best places to get 1/10 of the installed capacity as average power.

Capacity factor in Arizona is 25%. Today. Not theoretical, it's what realized now.

 

[jim hardy]

Mentors - Request title be changed to

"is it practical to generate all US power by solar PV? "

 

[jim mcnamara]

Expect one landowner lawsuit per mile, so maybe more trillions for lawyers.

Hooray for NIMBY's. @anorlunda you really nailed it.

The whole concept has problems with practicality. Especially the "political" aspect. One example --
1. All of the existing scada systems would need some sort of realtime control, centralized.
2. It would take trillions to upgrade the electric grid. My 2005 WECC map show Texas with 2 tie lines, good luck pushing 80000MW through them or getting TX to change it's 'yee-hah' policy on electric system management. Which will not fit #1 at all.

The point is really that every state can dictate how they want to manage/not manage utilities. And if cooperating is perceived as unwanted control (or whatever), the state has the right to balk. So having states that are proudly unique and somewhat defiant you cannot have a truly functional national e- grid. And yes there are FERC and NERC guidelines about lots of things. And TX and NM (where I am) are still able to do wacky things.

 

[CalcNerd]

I believe the best benefit of PV cells on rooftops is to help offset the huge AC usage of electricity during the hot summer months. This is when the solar cells contribute the most to the grid. If the solar cells are NOT installed, a larger baseline power reserve is needed/generated. If this power isn't generated locally (ie PV cells), more power is needed on already overburdened electrical lines and wasting even more energy as I^2R losses are also a positive loop problem ie more current demand = hotter wires = higher resistance and hotter medium and high voltage transformers at distribution centers.
.
The local PV cells don't help much, but the power company has ample reserves for 95% of the year, and if the PV cells can contribute that last CRITICAL 5% (numbers pulled from my posterior end) the power company will not have to build another dirty filthy coal powered energy plant. A win-win if the PV panels work at their most needed time of when the sun is driving up the temps in the middle of the summer.

 

[jim hardy]

Wow i never heard of WECC before. Search takes one to this interesting tutorial (256 pages but quite readable with copious illustrations)

https://www.wecc.biz/Administrative/WECC-System-Overview-2-slides-per-page.pdf

It does a good job of explaining a lot of power system basics.

"The grid" is a huge machine that we cannot see in action by looking at it .
We can see trains moving goods along train tracks but not megawatt-hours moving down power lines.
So it is not obvious what a distributed, moving, and fragile system is "the grid".to Jim McNamara's point #2:

2. It would take trillions to upgrade the electric grid. My 2005 WECC map show Texas with 2 tie lines, good luck pushing 80000MW through them

(With today's security environment good luck finding detailed transmission line maps...)
Generation is presently scattered and near point of use so most transmission lines aren't very long.
Take this map and redraw it for all generation emanating from the region of green rectangle.

It goes from a structure supported by a foundation underlying pretty much all of itself to one that's suspended by long spindly arms.
And for right now that's more than enough for me to contemplate. Old guys just don't handle fundamental change all that well.

old jim

credit for that map goes to
http://docplayer.net/docview/25/5923397/#file=/storage/25/5923397/5923397.pdf
with a big "Thank You ! ".

 

[skeptic2]

Perhaps batteries wouldn't be the best energy storage device. I visited a power plant south of Luddington Michigan which pumped water from Lake Michigan to a large reservoir at night when electric rates were low and let it flow back through a generator during the day when the rates were high. Some of the energy was stored in a large flywheel. One advantage of a flywheel is that there are lower losses converting between DC and AC. Energy from DC solar panels can be added to the flywheel with a DC motor and extracted using an alternator to feed the grid.

 

[mheslep]

The most recently completed HVDC transmission project in North America was the W. Alberta Transmission line: 500 kv, 1 GW, $1.7 B, 350 km, or about $7 million per GW mile.

http://www.marketwired.com/press-re...Alberta-transmission-line-project-1840556.htm

Using the cost of that project, replacing one of the US nuclear 1 GW reactor projects with solar a 1000 km away has transmission cost alone of $7 B, assuming some kind of yet-to-be-inventec storage is colocated with the solar. If storage is remote, then 4 or 5 GW of intermittent transmission is required for up to $35 B for transmission alone.

 

[mheslep]

...visited a power plant south of Luddington Michigan which pumped water from Lake Michigan to a large reservoir at night when electric rates were low and let it flow back through a generator during the day when the rates were high. ...

While the pumped storage hydro capacity in the US is useful for leveling a bit of peak demand, it's a trivial amount compared to the hundreds of TWH required to backup up the entire US for several days, the topic of the OP. The typical run time for a PHS plant is a few hours.

 

[johnbbahm]

I was thinking about something like this earlier, but perhaps storing the surplus electricity as natural gas,
which could be moved through the natural gas grid.
https://www.fraunhofer.de/en/press/research-news/2010/04/green-electricity-storage-gas.html
The Gas could be used to fire existing local power plants, heat homes, or reformed into liquid fuels.
If the carbon came from atmospheric CO2, all the gas would be carbon neutral.
If the electrical utilities are pushing back from home solar, it is likely because of the highly imbalanced
price structure from net metering. As popular as net metering is, it needs to go away before home solar can
progress very far.
(Forcing a retailer to buy a product at his own retail price will never be popular with the retailer.)

 

[OrangeDog]

First, you wouldn't want all of the solar energy in one spot because of cloud coverage and weather. What happens if we get a big storm? Is everyone screwed until it passes? By spreading out the panels over a larger area, you essentially minimize the "risk" or probability of a total outage. It isn't unlike diversifying your bonds (props if you got the reference).

Second, all your solar energy is one area is like having a big bulls-eye for our enemies. If some country wants to bomb us, just hit the solar arrays and we are screwed.

To tell you the truth, I think something similar to solar roads have the most promise. Good luck getting anything done with the energy lobbyists in charge. Too bad this is also one of those venture capital crackpot/BS start ups. I do think the concept in principle has potential.
https://en.wikipedia.org/wiki/Solar_Roadways

 

[CalcNerd]

If someone wants to harvest energy from roadways, and pie in the sky ideas are looked at, consider a piezoelectric roadway surface. The bigger the vehicle, the more juice you get. I suspect that this technology would cost a fortune to implement, but you would only install it on the busiest of roads and it might even be made durable enough to avoid potholes!

 

[anorlunda]

To make this thread interesting, let's dump the suggestion to place all that capacity only in Arizona.

The sun shines in all places in the lower 48 states, but because of weather, and because of latitude, PV panels are most effective per $m^2$ in some regions. However as Jim pointed out in #3, the cost of panels is only $0.86 out of a total installed cost of $5/kw. If we had to add 50% or even 100% more $m^2/watt$ to compensate for location, it wouldn't have a big effect on costs. Therefore, the benefits in locating all the generation in a sunny region are tiny compared to the massive costs of transmitting that power to the entire 48. Please let's scratch that part of the idea and focus on the potential of PV distributed over the entire country, close to the loads.

The interesting part of the question is scalability. Could the use of PV solar plus storage be scaled all the way up to the ultimate extreme of 100% of our electric capcity? The question must be asked on three levels.

1. Science: Are there any unbreakable laws of physics that we would have to break thus making the proposition impossible? (i.e. things like conservation of energy or the speed of light). I can't think of any, so my answer to that is no. If anyone disagrees, please raise those objections early.
2. Engineering: This is where I would like to focus this thread. Is it practical? What are the engineering, economic, or legal obstacles to PV scalability?
3. Social: Just because we can do something doesn't mean we should. I would like to leave social questions, including renewability or the cleanliness of PV, out of this discussion if possible. I also note that it would not make sense to abandon wind or any of our existing investment in electric generation even if 100% PV is possible. I mostly fear that the discussion in this thread may become too unfocused if we include social issues. PF already has a thread YOU!: Fix the US Energy Crisis for unfocused energy discussion.

42% of the USA population lives in multifamily housing with 5 or more units with very few $m^2$ of rooftop per tenant. Also as a guess, half of the single family homes have shade trees or orientation, or blocking hills or mountains that make PV unsuitable for them. Therefore, a discussion of PV solar scalability necessarily includes both consumer-owned rooftop PV and utility-owned central PV generation.

Given all the above, the existing bulk power transmission grid would remain largely unchanged in form and in public need by conversion to PV. We don't need to include that in the discussion at all. Local power distribution at the neighborhood level however, faces some major challenges.

 

[mheslep]

I was thinking about something like this earlier, but perhaps storing the surplus electricity as natural gas,
which could be moved through the natural gas grid.
https://www.fraunhofer.de/en/press/research-news/2010/04/green-electricity-storage-gas.html
The Gas could be used to fire existing local power plants, heat homes, or reformed into liquid fuels.
If the carbon came from atmospheric CO2, all the gas would be carbon neutral.
If the electrical utilities are pushing back from home solar, it is likely because of the highly imbalanced
price structure from net metering. As popular as net metering is, it needs to go away before home solar can
progress very far.
(Forcing a retailer to buy a product at his own retail price will never be popular with the retailer.)

A very good and more recent summary of the economics involved for P2G (and then G2P again) is found here. One problem with this approach, that is, an all solar power grid backed up by power-to-gas, is that in addition to the cost of the 2.5 TW of solar power required a full load capable gas power fleet is required. With a reliability margin, one needs about what is in place now (minus the hydro), or about 1 TW of gas fired electric power plant fleet, that runs only at night. The cost would be the solar, the gas fleet, and the P2G fleet: enormous.

 

[insightful]

However as Jim pointed out in #3, the cost of panels is only $0.86 out of a total installed cost of $5/kw.

Obviously, you meant per watt.

 

[anorlunda]

Obviously, you meant per watt.

Yes, sorry. $0.86/watt for the panel, and $5/watt "all in ncost" In addition, I should have said that most of the $5.00-$0.86=$4.14 difference is not much dependent on the $m^2$ of the panels.

Next compare the costs of locating a watt in Maine instead of Arizona. Because of the latitude and weather, we may need twice as many panels in Maine, thus $5.86/watt. Say $6/watt round numbers. Compare that with the cost of hundreds or thousands of dollars per watt in capital costs to transmit the power from AZ to ME (I didn't really calculate those numbers, just eyeballed them). The point is that the economics of locating the panels near the load far outweigh those of putting the panels in a sunny state far away.

 

[jim mcnamara]

@anorlunda - consider basing your starting point (as above) on this kind of data:
http://petedanko.net/state-per-capita-solar-pv-generation-2015/

There are some few places where solar is has a big existing footprint compared with most of the US.
So the total cost there per capita will be lower. Maine notwithstanding. FWIW fogbound San Francisco has a large footprint of residential PV generation. So attitude counts for a lot, IMO.

 

[anorlunda]

Energy Storage:

Of course, a necessary part of large scale PV is battery storage. Other types of storage exist, but batteries are fully dispatchable and thus very friendly to the power grid.

Both home and utility scale battery storage are showing rapid development recently. The measures are energy capacity in watt-hours, power delivery capacity in watts, and cost. They are improving in all three measures. However, I think it's fair to say that they are now adequate yet, so we are speculating on the future.

Tesla is expected to sell 168.5 MWh of energy storage systems to the nation's leading residential solar system installer, Solar City.

If PV solar is the dominant form of generation, then other types of backup would dissapear. Storage capacity for a single day would not be enough, the capacity would have to cover the worst case weather event.

Regional reserve capacity also serve to offset local storage. For example, if one region's panels are covered by snow (or by dust in case of a volcanic eruption), then power could be supplied from neighboring regions until the panels are cleaned. That requires transmission capacity, but that level of transmission capacity already exists in most cases.

Weather is also a big factor. I remember one winter I spent in Vermont with more than 100 consecutive cloudy days. Even places like Arizona have a monsoon season. But I also know that my solar panels make as much as 50% as much energy on a cloudy day, so the solar capacity calculations are difficult.

Accurately calculating the actual reserve and energy storage requirements is exceedingly difficult. For purposes of this discussion, I'll hazard a guess of 100% overcapacity for reserve purposes, plus storage of 7x24 hours of energy would be the minimum requirements for a national PV system. But those guesses could be very wrong.

 

[mheslep]

Energy Storage:

Of course, a necessary part of large scale PV is battery storage. Other types of storage exist, but batteries are fully dispatchable and thus very friendly to the power grid.

Both home and utility scale battery storage are showing rapid development recently. ...

To date there are no utility scale backups of size and depth to wholly back up a single large power plant taken offline, nowhere in the world. The battery installations used by utilities, such as they are, are typically for minutes long carry over for the like of accommodating spinning standby. Similarly the home battery packs such as the ones from Tesla are also insufficient to allow anyone to cut loose a common home from the grid.

 

[anorlunda]

@anorlunda - consider basing your starting point (as above) on this kind of data:
http://petedanko.net/state-per-capita-solar-pv-generation-2015/

There are some few places where solar is has a big existing footprint compared with most of the US.
So the total cost there per capita will be lower. Maine notwithstanding. FWIW fogbound San Francisco has a large footprint of residential PV generation. So attitude counts for a lot, IMO.

Nice data. Thanks.

The highest state was Nevada with 615 kwh/person*year. According to the Energy Information Administration, electric sales (all sectors) in 2015 were
3,724,000,000,000 kwh. The US population was 326 million. Thus consuption was 11423 kwh/person*year. That make the PV footprint in Nevada about 5%, if I did the numbers right. We are still very far indeed from 100%. I think the national average was 0.2% of US electric generation was PV solar, so the premise of this thread is a x500 expansion in solar PV capacity.

 

[anorlunda]

To date there are no utility scale backups of size and depth to wholly back up a single large power plant taken offline, nowhere in the world. The battery installations used by utilities, such as they are, are typically for minutes long carry over for the like of accommodating spinning standby. Similarly the home battery packs such as the ones from Tesla are also insufficient to allow anyone to cut loose a common home from the grid.

That's very true.

We are beginning to expose some of the magnitudes of the problem. IMO, laymen most need education of the magnitudes of energy problems. That is part of the benefits from conducting a thread such as this. If we talk about a national 100% PV system, then the magnitudes can not be hidden or obscured.

 

[mheslep]

Tim Murphy of UCSD does a good job educating on the limits of energy production. His technical descriptions are superb, though IMO he fills compelled to stray into fanaticism on the subject of human behavior. Solar here, large scale battery backup here.

 

[mheslep]

Nice data. Thanks.

The highest state was Nevada with 615 kwh/person*year. According to the Energy Information Administration, electric sales (all sectors) in 2015 were
3,724,000,000,000 kwh. The US population was 326 million. Thus consuption was 11423 kwh/person*year. That make the PV footprint in Nevada about 5%, if I did the numbers right. We are still very far indeed from 100%. I think the national average was 0.2% of US electric generation was PV solar, so the premise of this thread is a x500 expansion in solar PV capacity.

Electric consumption is tracked by EIA and others. US electric per capita consumption peaked around 2007, and in this decade appears to be dropping at about 100 kWh per year (currently around 13,000 kWh per year)

 

[Baluncore]

If someone wants to harvest energy from roadways, and pie in the sky ideas are looked at, consider a piezoelectric roadway surface. The bigger the vehicle, the more juice you get. I suspect that this technology would cost a fortune to implement, but you would only install it on the busiest of roads and it might even be made durable enough to avoid potholes!

I hope that was a joke.
It would be a big incentive to avoid busy roads.
Almost all the energy harvested would come from the fuel bowser.
Electric cars would have a reduced range.

 

[dlgoff]

We are beginning to expose some of the magnitudes of the problem. IMO, laymen most need education of the magnitudes of energy problems.

The Union Pacific Railroad has two sets of east-west tracks near my home. When there's 100+ loaded coal cars going east and 100+ empties going west every 20 minutes, that helps expose the magnitude.

 

[jim hardy]

The Union Pacific Railroad has two sets of east-west tracks near my home. When there's 100+ loaded coal cars going east and 100+ empties going west every 20 minutes, that helps expose the magnitude.

It's BNSF by my house . Coal trains headed for Southern Company plants in S Alabama making "Coal by Wire" electricity for Florida.

We are beginning to expose some of the magnitudes of the problem. IMO,

I wish everyone could at some time in their life stand next to a thousand megawatt turbine, feel the heat, breathe the steam, feel it shaking the ground and the rumbling sound going through your whole body... it changes you.
Any other form of generation is papier mache.

 

[dlgoff]

I wish everyone could at some time in their life stand next to a thousand megawatt turbine, ...

Try three 800MW ones on a single floor. Been there, done that. Jeffrey Energy Center.

 

[CalcNerd]

I hope that was a joke.
It would be a big incentive to avoid busy roads.
Almost all the energy harvested would come from the fuel bowser.
Electric cars would have a reduced range.

Yes, it was a joke, but not for the reasons you mention. NO energy is taken directly from the vehicle ie it would not reduce the range of an electric vehicle. I suggest you look up piezoelectric generators. They would rob zero energy from the traffic, they recover their energy from the weight of the vehicle passing over them. Extreme cost is the prohibitive reason for not using them, not that they are robbing mileage from the vehicles passing over them.

 

[johnbbahm]

A very good and more recent summary of the economics involved for P2G (and then G2P again) is found here. One problem with this approach, that is, an all solar power grid backed up by power-to-gas, is that in addition to the cost of the 2.5 TW of solar power required a full load capable gas power fleet is required. With a reliability margin, one needs about what is in place now (minus the hydro), or about 1 TW of gas fired electric power plant fleet, that runs only at night. The cost would be the solar, the gas fleet, and the P2G fleet: enormous.

Thanks, that is a good link!
From the perspective of the discussion, I was thinking of using the P2G gas not just as storage, but transport.

 

[Baluncore]

They would rob zero energy from the traffic, they recover their energy from the weight of the vehicle passing over them.

So where do you really think that energy would come from?

 

[anorlunda]

I'm working on a spreadsheet to calculate the total estimated capital and operating (O&M) costs for a 100% solar PV conversion for the USA. I'll publish it here when ready. I'm using external sources, plus helpful data and links that other PF members have posted in this thread. Before that, there are several technical aspects to discuss to set the frame.

 

[CalcNerd]

So where do you really think that energy would come from?

Did you read anything about piezoelectric generators? The energy they are getting from the vehicle is the energy that is imparted upon the pavement as the vehicle passes over the roadway. That gravitational energy (weight) is always wasted, this is just a method to recover that energy. It is, admittedly not from nothing, but it is always there, and not recovered. However, these piezoelectric generators would recover THAT energy. Are they practical? No. But you could have done your own research before you ask.
.
Here is a link for reference:
http://www.greenoptimistic.com/israel-piezoelectric-highway-20091006/#.VyIjs2f2Y5s

 

[Averagesupernova]

Did you read anything about piezoelectric generators? The energy they are getting from the vehicle is the energy that is imparted upon the pavement as the vehicle passes over the roadway. That gravitational energy (weight) is always wasted, this is just a method to recover that energy. It is, admittedly not from nothing, but it is always there, and not recovered. However, these piezoelectric generators would recover THAT energy. Are they practical? No. But you could have done your own research before you ask.
.
Here is a link for reference:
http://www.greenoptimistic.com/israel-piezoelectric-highway-20091006/#.VyIjs2f2Y5s

My bold, no such thing.

 

[CalcNerd]

My bold, no such thing.

True, my poor choice of wording. What would you call it? Energy is recovered by the vehicle passing over the piezoelectric generator, that is a reproductable "ie proven" fact.

 

[Baluncore]

But you could have done your own research before you ask.

I understand piezo transducers. I just wanted to know where you thought the energy might come from. Conservation of energy holds.

That gravitational energy (weight) is always wasted,

Gravitational energy is not weight. Weight is only a force, being the product of mass and the acceleration due to gravity.
If something moves when you apply a force, you have done work and transferred energy. If it does not move when the force is applied then you have done no work and transferred no energy. What you appear to be saying is that the road drops as your wheel rolls onto it, then rises as you drive up out of the hole. That means you are always driving up hill.
I am saying that energy must come from your fuel supply.

 

[anorlunda]

Rooftop Solar

Residential rooftop solar PV is tremendously appealing. I myself get all my power from PV panels (but on my boat, I don't have a house). I suspect that many PF members reading this thread think that rooftop solar is the subject of this thread. If everybody just did what early adopters have already done, we have the national energy system solved. It's not that simple.

As I noted in #17, 42% of US households live in multifamily dwellings. I guess that half of the 58% of single family homes don't have the unshaded southern exposure needed. Therefore only about 30% of residential electric use is candidate for rooftop solar. I'll further estimate that half of commercial power could be rooftop PV (that might be too high). The EIA says that US electric sales were 38% residential, 36% commercial, and 26% industrial. From all that, I calculate that a national PV solar grid would have at most 25% rooftop solar, and 75% utility-owned solar farms.

Residential rooftop solar is a form of distributed generation. Here's a pretty good article on that https://en.wikipedia.org/wiki/Distributed_generation
Distributed generation causes numerous problems for utility designers of power distribution grids. Some of the problems are mentioned in the Wiki article. Some, but not all, of the problems are mitigated by mandated "utility interface boxes". I'm not an expert on distributed generation, so perhaps other PF members on this thread can post about it..

A partial cure for the overhead costs of distributed generation on the power grid could be to form micro-grids. The wiki article includes a section on that. But a micro grid is much more than stringing wires between neighboring houses in the neighborhood. For one thing, the National Electric Code (NEC) imposes numerous restrictions on how it must be designed and implemented. The micro grid must also provide its own backup. A real life micro grid needs to be designed by professional engineers, and the cost is far too high for most neighborhoods. It is possible that providers of pre-engineered off-the-shelf micro grids could appear. Anyhow, in my estimate, I do not plan to include any micro grid influence on total costs.

But from a layman's view, just consider that 120 years of tradition have evolved power distribution systems based on the valid assumption that only loads, not generators, exist at the far ends of those lines. When that assumption becomes invalid, it challenges the whole approach to distribution at a pretty fundamental level. In my total estimate spreadsheet, I plan to just eyeball a number for the utility's costs to accommodate distributed generation and add that to the solar O&M costs.

I also expect that many solar enthusiasts assume that expansion of rooftop solar will continue to be financed by net metering. I understand the "good for the goose - good for the gander" logic behind net metering. But that is not a sustainable business model. It transfers costs to non-solar utility customers. Also, IMO it is just not fair. I'll explain why.

Living off the grid, a PV homeower has to pay for energy storage and backup. Perhaps batteries. Perhaps a backup gas-powered generator. Perhaps a contract with a third party backup provider. In all those cases, the homeowner has to pay the cost. But if the backup provider is the public utility, homeowners think that service should be provided free via net metering (free if your net is zero kwh). That makes no sense. If we paid the utility for backup service only, the shocking reality is that about 75% of the monthly bill is for power delivery and installed capacity costs, and only 25% for actual energy used. That is hidden from many consumers today because delivery costs are buried in the kwh energy charge, but if the utility provided backup only service (with zero energy use) zero, the real costs would have to be exposed.

In my estimate, I do not plan to include any net metering in total costs.

 

[CalcNerd]

Gravitational energy is not weight. Weight is only a force, being the product of mass and the acceleration due to gravity.
If something moves when you apply a force, you have done work and transferred energy. If it does not move when the force is applied then you have done no work and transferred no energy. What you appear to be saying is that the road drops as your wheel rolls onto it, then rises as you drive up out of the hole. That means you are always driving up hill.
I am saying that energy must come from your fuel supply.

While this is technically true, the actual compression of these piezoelectric generators is nearly miniscule. The energy that they are actually recovering is the energy that would normally be wasted by the vehicle anyway. They are NOT driving uphill in any measurable form. Normal asphalt probably compresses more than these transducers.

 

[Salvador]

@CalcNerd , Solar panels to account for the whole US energy production in itself is a big enough challenge , piezoelectric roads I think are simply out of the frame by any means.I don't know how much power would they produce per mile and how much they would cost for the same mile but my gut tells me the energy out vs production cost , logistics problems and basically rebuilding the whole infrastructure of roads, which the government is already sweating to simply keep up the repairs as the roads age, sounds unrealistic.

@Jim as I read what you say about standing next to a large turbine running and the coal trains going by , I cannot but think how much work goes to waste since the thermal cycle of steam is only what ? 50% efficiency , I guess the real number was less.
Imagine how many tons of coal simply go through the chimney every minute without ever getting to a useful end other than increasing the already high "greenhouse" gas in atmosphere.
Sometimes I feel a bit sad that physics robs us even more from an already not too ECO friendly energy production's output power.

 

[Baluncore]

Normal asphalt probably compresses more than these transducers.

But the existing road surface is elastic. The wheel rolls in a depression. The force on the front of the wheel is balanced against the force on the rear of the wheel. If you extract some energy, it is no longer elastic, the forces do not balance and so it costs more in fuel. If you extract energy from the roadway you must supply all that energy by using more fuel.

Consider covering the road surface with piezo transducers, but do not connect the terminals. It is elastic, has balanced forces and is efficient. If you then connect the terminals and extract some energy, all that extracted energy comes from your vehicle tank or battery.

 

[Baluncore]

I think it is a mistake to worship huge power generation plants and huge energy consuming businesses. If a plant needs power then it should buy and operate sufficient generator plant. I tire of subsidising cheap power to industry by being connected to the state grid.

I have installed PV and am now energy and revenue neutral. I am still connected to the state hydroelectric grid. During the day when I have excess PV power I am delaying the fall of water from reservoirs. That water can be used later when needed. So the hydroelectric grid is effectively my storage system and I do not need a battery bank.

I pay a network fee as well as a fee for the power I consume. The network fee is progressively rising while storage battery costs are falling, so the economic justification for abandoning the expensive network connection increases. As more customers step away, the network maintenance cost to the remaining customers will increase faster, until something breaks. If the network can no longer compete financially, then why should I keep supporting the network. We live in interesting times.

The argument that network evolution in the past justifies its continued use today is clearly false. Things change.
The historical power distribution system has become an anachronism.

 

[CalcNerd]

But the existing road surface is elastic. The wheel rolls in a depression. The force on the front of the wheel is balanced against the force on the rear of the wheel. If you extract some energy, it is no longer elastic, the forces do not balance and so it costs more in fuel. If you extract energy from the roadway you must supply all that energy by using more fuel.

Consider covering the road surface with piezo transducers, but do not connect the terminals. It is elastic, has balanced forces and is efficient. If you then connect the terminals and extract some energy, all that extracted energy comes from your vehicle tank or battery.

Actually, this IS NOT TRUE. The typical road also absorbs energy. Have you noticed that heavily traveled roads in the winter do not have ICE on them in the northern areas. That is because they are warmed by the energy of the cars passing over them. A typical road robs energy from the vehicle. These transducers are merely collecting this energy (and not the energy of raising the car via Potential Energy). I suggest you do some research on these transducers if you are going to pursue that arguement. Their compressions are measured in micrometers ie your car tires will not be robbed of any extra energy unless you decide to compare to a steel roadway with zero compression. Read the stats on these devices. They are crystal based ie the compression in not easily measurable, especially in comparison to the give of a pneumatic tire.

@CalcNerd , Solar panels to account for the whole US energy production in itself is a big enough challenge , piezoelectric roads I think are simply out of the frame by any means.I don't know how much power would they produce per mile and how much they would cost for the same mile but my gut tells me the energy out vs production cost , logistics problems and basically rebuilding the whole infrastructure of roads, which the government is already sweating to simply keep up the repairs as the roads age, sounds unrealistic.

I agree that the piezoelectric IS NOT a viable solution (in at least two posts). It is a pie in the sky solution, but not for the reasons Baluncore wants to argue. His concern is with the 1st law of thermodynamics, that you can't get something for nothing. I am NOT arguing that either, my argument is that a piezoelectric transducer IS NOT reducing his mileage on the vehicles passing over them. These transducers are merely collecting energy that is normally wasted by a vehicles or the tires interaction with a roadway surface (better terminology is awaiting a reply from Averagesupernova here).

 

[jim hardy]

50% efficiency , I guess the real number was less.
Imagine how many tons of coal simply go through the chimney every minute without ever getting to a useful end other than increasing the already high "greenhouse" gas in atmosphere.

40% is about right for a 1000 degF 2400psi steam plant before the days of stack scrubbers.
Gas turbines with a heat recovery steam cycle can make 50%.
You might enjoy reading about early efforts to help Carnot help us by using mercury for working fluid here
http://www.douglas-self.com/MUSEUM/POWER/mercury/mercury.htm
...today that'd make EPA madder than hatters...

Just to give this scale:
There are about 46,000 miles of interstate highway in the US https://www.fhwa.dot.gov/interstate/faq.cfm
to achieve Nikkom's 150² square miles of solar panels
we'd need a corridor for them one half mile wide enclosing the US interstate system.
Well, that'd be distributed and provide access but it's a lot of land to condemn and claim . Risk of sparking a landowner revolt.

I agree that the piezoelectric IS NOT a viable solution (in at least two posts).

If a heavily traveled piezo road can make 100 kw/km, 160kw/mile
160E3 X 46,000 = 7.36E9 watts
digging up the whole Interstate system to put piezo underneath might make 7.36 gigawatts , 7% of the 1000 gw target.
And i think that's optimistic - see http://large.stanford.edu/courses/2012/ph240/garland1/

However, a more reasonable approximation can be made by using the fact that approximately 5% of the energy consumed by the car is lost as rolling friction, although rolling friction accounts for both internal friction in the wheels and friction due to the asphalt. [5] By replacing thermal efficiency in the above equation with 5%, the amount of energy released into the ground for one 20 mpg car would decrease to 0.19 MJ. This one-kilometer strip could then power at most 13 homes (32 kW) for the 20 mpg car, or 52 homes (128 kW) for an 18-wheeler. For this calculation, there is still a major assumption that all the vibrational energy of the road is captured by piezoelectric devices.

It is not clear whether the numbers currently used to quantify generating capacity are misguided or simply misreported, but under the optimistic assumptions stated above, piezoelectric devices over a one-kilometer strip of road will generate power for only about 15 homes. Unless the road carries only 5 mpg vehicles (or many more than 600 vehicles per hour), it is unlikely that anywhere near 400 kW of power can be generated from one kilometer.

This thread is about practicality - i agree piezo roads don't make the cut.old jim

 

[Salvador]

I would agree with what you say @CalcNerd , the only time when the road becomes somewhat elastic is only under two conditions , first the outside temperature is high enough with preferably direct sunlight and it's made of tarmac which is much softer under higher temperatures than reinforced concrete as used in some places or any other teeth grinding surface.I also doubt a car with ordinary struts and shock absorbers can get anything back from the road once it's started to jiggle back and forth up and down while going down a bad or heavily used road.
maybe modern cars with electromagnetic shock absorbers can indeed get something back.

Another interesting topic @Baluncore raised is that we should stop "worshiping" big plants and big consumers and big grid business , Ok I am all for it , but since you know physics which I think you do , tell me how are you planning to make these main electricity generating plants small?
We know fission can't be smaller than some given size because mainly of critical mass , the heavy tech involved and the steam cycle itself.
the promising fusion also has a minimum size even if we one day achieve a net output at all.
Same goes for hydro , an let's not even talk about coal here were not only size but smell is a big factor.
So in these terms how do you see the grid a thing of the past as of yet?

Ok renewables , yes they can be made smaller and can be afforded by individuals installed either into their houses , property etc.
Yet still do most homes have the resources and the capability to do so ?
Also do most residential or work areas are located in places were the main renewables are common enough to yield any worthwhile output?
Being energy neutral would probably be the greatest thing since industrial revolution but I don't see it coming yet.
If someone or you Baluncore for that matter have any opposing answers to my raised questions please go ahead and shoot me down.
P.S. and even the solar idea here talked about in this thread , if implemented the way I see it is not something someone is going to build in his backyard and become neutral , maybe even a business himself , it will probably too be one of the many large energy companies properties with the output electricity being sold to the national grid.
I assume you live in Australia and get a lot of sunlight which might be the reason you are lucky enough to use solar panels.
Were I live I would need a really big battery (non existent) to charge up because I'm getting serious sunlight only less than half of the year.

That being said I do agree that diversification is definitely a must even if the output from the renewables can't fulfill all your needs, some is still better than none.
If Ii would have a private house instead of an apartment in a highrise building I would definitely use both solar and wind since I'm getting wind throughout the year.
Knowing physics , heck I could build a windmill myself for the fun of it , my friend did that years ago and doesn't complain a bit.

 

[jim hardy]

I have installed PV and am now energy and revenue neutral. I am still connected to the state hydroelectric grid. During the day when I have excess PV power I am delaying the fall of water from reservoirs. That water can be used later when needed. So the hydroelectric grid is effectively my storage system and I do not need a battery bank.

You have the right idea there !

You must live in a mild climate.
Sun belt needs air conditioning
and we are so accustomed to hot water and frost free 1kw refrigerators that a break-even pv system is not yet for the average homeowner.

I dream of going off grid but it'll have to wait until i invent a practical two ton solar chiller.

old jim

 

[Salvador]

Or just listen to more rap music were artists like Nelly used to rhyme quote directly from the song

"Its gettin hot in here (so hot)
So take off all your clothes

I am gettin so hot, I want to take my clothes off"

P.S. Sorry for the interruption. :)

 

[jim hardy]

We know fission can't be smaller than some given size because mainly of critical mass , the heavy tech involved and the steam cycle itself.

The shielding required to protect operators means there'll be a lot of concrete required. So you make it big enough that the concrete supports required to hold it up are also big enough to provide shielding.

Military has built small 1 to 2 megawatt reactor plants that fit on a flatbed trailer.
https://en.wikipedia.org/wiki/Army_Nuclear_Power_Program

Backyard Nukes are possible but not practical.