# The future of solar power

1. May 19, 2017

### mheslep

The 80 MWh Mira Loma battery facility is for grid transients. It does not qualify as utility 'storage' in the sense of pumped hydro storage plants. Twelve Mira Loma plants would be required to back up *one* large (GW) sized thermal plant or wind farm for *one* hour. There are no battery based utility scale storage facilities anywhere the world, nor any planned, that could back up one middling 500 MW power plant for a day.

2. May 19, 2017

### mheslep

All the eggs are crushed every night.

3. May 19, 2017

### mheslep

So far as I can tell, there are no common residential homes in the US (typical sq footage, not a woodland shack) that can run off the grid for 2 to 3 days anytime of the year using just batteries, no combustion generator behind the curtain.

Off the grid doesn't work with solar. And, once you need the grid, some 3/4 of its cost is just the maintenance of the infrastructure. Actually shipping power is an afterthought. So, those with residential solar and net metering plans who avoid those costs are simply pushing the grid costs on to their neighbors. That practice is beginning to end in the US.

4. May 19, 2017

### nikkkom

This does not happen in Europe since a lot of electrical lines here are underground and thus are well-protected against weather. I'm guessing it's used more in a denser-populated areas where cost of land is relatively more important, and also in places expanding grid capacity at some point forced it underground because above-ground expansion was not possible.

I take it this is economically unattractive for sparsely populated areas of US, since lines are longer while customers are fewer?

5. May 19, 2017

### nitsuj

Some semantic work there on "utility storage". A journey of a thousand miles begins with a single step, "According to market research firm IHS, the energy storage market is set to “explode” to an annual installation size of 6 gigawatts (GW) in 2017 and over 40 GW by 2022 — from an initial base of only 0.34 GW installed in 2012 and 2013."

Comparing the energy production of a traditional power plant to the storage capacity of current tech batts. Why must a battery be able to support a days worth of energy from said power plant? Such storage could be done locally, even down to a per person...this flexibility is appealing.

There are a number of MW storage facilities being built and running all over the world. China, Japan & California seem to be throwing money at this...presumably to further improve/demonstrate the technology.

I suspect the reason the industry is not planning to build a storage facility capable of backing up one middling 500 MW power plant for a day is because it makes MUCH more sense to scale up...such a bizarre argument. "There are no manned space ships capable of travelling to Titan nor are any planned...ergo not possible."

Once government funded projects demonstrate the economics the industry grows....and grows and grows.

Last edited: May 19, 2017
6. May 19, 2017

### gleem

Rooftop installations on big box stores ,warehouses and public buildings will most likely only provide power for those structures. facotries that may have access to adjacent land will probably only produce a fractions of their needs. As a example a factory near me just built a solar facility 1.57 MW, producing about 2.3MWhrs per year on 6 acres (4992 panels) produces only about 12 % of their needs. One MW of power will meet the need of only about 70- 100 residences.

One could consider municipal solar farms. A community with 5000 houses would need about 60 MW of panels for just the residential requirements add to that commercial and municipal needs. The area needed would be similar to say an additional land fill. It could be funded by bonds and

I don't think solar is a good option for blackout in a place like Michigan especially when many will be in the winter when output is minimal. You can go for weeks without significant sun. Better with a standby generator 16kW about $3500 https://www.electricgeneratorsdirect.com/power/generac-11kw-16-kw-home-standby-generators.html Did a quick calc for a 1 GW, 4GW-hr storage facility using Tesla POWER PACK batteries. it would take 20,000 POWERPACKs occupying a building roughly taking up 4 acres and 5 stories high. From pictures of the Mira Loma facility it looks like the batteries take up about 0.25 acres with the transformers and other equipment taking up another and the power lines towers taking up ? all this fits on a 1.5 acre site. The Mira Loma plant provides 2500 houses back up for 24 hours producing 20 MW of power (50kW x 396 bat) with an energy storage of 83,000 kW-hrs. which for 2500 houses is about 33kWhr which is reasonable. A 1 GW facility which is 50 times greater would provide those same houses with 50 days of power. or 125,000 homes 24 hours. and take up at most 75 acres probably significantly less. However such a facility might cost as much as$900M .

7. May 19, 2017

### NTL2009

It's not clear to me what your point is?

What difference does it make who is "using" the output of the solar panels, or what % of their usage those panels represent? An installation of X MW will offset that much grid power, regardless of who is using it.

BTW, I think you meant 2.3GWhrs (not 2.3MWhrs) per year. 1.57 MW * ~ 5 hours/day * about 300 sunny days/year is about 2.3 GWhrs/year.

8. May 19, 2017

### gleem

I got the impression that there was a thought of using the large roof areas of large area commercial buildings to produce excess power which could be diverted to residential use.

9. May 19, 2017

### NTL2009

The thought is to use the large roof areas of large area commercial buildings to produce (solar) power (period). It just goes into the grid, there's essentially no difference to the grid and the power plants between 1,000 panels on a big flat roof in the neighborhood, or 2 panels on 500 houses in the neighborhood.

The important difference is that it will be cheaper, faster and safer to do one install on a big building, and very likely to get more power from the same number of panels, because they will all be at the optimum angle on a big flat roof, with no shade trees. Economy of scale will come into play at all levels (fewer transfer switches, optimally sized inverters, etc). Maintenance on one site is far easier (and likely to be noticed and repaired quicker) on one big install versus 500 small ones. And over 10-20-30 years, guess how many trees will grow and shade some of those panels installed earlier?

10. May 19, 2017

### gleem

I got that and you are correct. Many large local facilities obviate a number of problems.

11. May 19, 2017

### Staff: Mentor

In towns, the lines are typically underground, but the big distribution lines between towns are in the open air as everywhere in the world. We just don't have so many bad ice storms and probably more redundancy in the network.

12. May 19, 2017

### NTL2009

But what point were you trying to make about the commercial building using all (or most?) of the energy the panels would produce?

13. May 19, 2017

### gleem

.That the panel arrays takes up all the available space for their own needs and they cannot produce any excess power to sell to the utility.

14. May 19, 2017

### NTL2009

And again, what difference does that make?

A) If a set of panels on a commercial building produce exactly 1 MW at noon, and the building is consuming exactly 1 MW at that time, the power plants on the grid produce 1 MW less to feed that grid than if there were no panels.

B) If those same panels are scattered across hundreds of houses, and we assume (maybe incorrectly), that the houses are not consuming all that is produced, the net effect is the same. The power plants on the grid produce 1 MW less to feed that grid.

I see essentially no difference between the power being consumed at the point of solar generation, or consumed by others nearby on that grid. I say "essentially", because consuming it close to where it is generated will reduce transmission losses somewhat, another plus for commercial installations.

You seem to think there is some advantage to it being scattered across many homes. But I do not get your point.

Other than the losses I mentioned, there is no connection between the roof used to generate the power, and how much consumption is under that roof, they are just separate things. The grid doesn't 'care' if the solar panels were put over land where no electricity was being used, or put on the roof of a manufacturing plant that uses more power than the panels produce. The end result is the same.

15. May 19, 2017

### gleem

If the panel where scattered and only half of the power generated where used the panel owners put that on the grid and get paid the going rate for electricity generators. So when you are not home your panels are making money.

16. May 19, 2017

### NTL2009

AFAIK, no utility pays a homeowner more (per kWh) for excess power than they charge that homeowner for consumption. It's a wash.

17. May 19, 2017

### gleem

Suppose I normally use 40 kwhr per day my meter reads 10000 kwhr. at the beginning of the day. I use 25kWhrs. during the daytime when my panels produce 60 kwhrs. during this period. producing 35kwhrs of excess energy. At the end of the day my meter reads 9965kWhrs. I produced enough electricity myself so no charge for electricity that day plus I sent to the utility for their use 35KkWhrs for which they credit my account via the meter. At least that's the way I understand it and the reason people spend big bucks to put in these panels. and then there's the tax breaks on top of it.

18. May 19, 2017

### Staff: Mentor

The German government did that for a while (and continues to do so for old installations), now the rates are lower.
Various governments do that for wind energy, this plus the equivalent for solar power can make electricity market prices negative - it makes sense to "sell" electricity and pay for it if the government pays you more than that. An odd situation.
Everything is heavily subsidized. Directly, and indirectly - because you still need the grid with your solar panels (even more than before: you now use it in both directions!), but now you pay less for it. Which means others have to pay more for it.

19. May 19, 2017

### gleem

I do not know in fact that they pay the total cost per kwhr. because it includes the charge for generation and the charge for transmission which for me are about equal. If the meter reads less than the previous day then they know your sold them power and they might credit your account for the generation charge only and not the total charge. So everything is copacetic.

20. May 19, 2017

### Staff: Mentor

That's not what I meant. Let's ignore taxes for now:

Producing 1 kWh typically costs something like 4 cent in big power plants. The distribution, logistics and so on cost about the same, so you pay 8 cents per kWh in total. That is the system with big power plants only.
Now you install a small solar panel on your roof. On some days you don't need to buy electricity. You don't pay the 4 cent/kWh for the production naturally, but you also don't pay the 4 cent/kWh used to maintain the grid. But the grid still has to be maintained, because you want to be able to use it at any time. To get the same money to operate the grid, the electricity price has to rise. The effect from your local solar panel is tiny, of course, but summed over all residential solar power it can matter. While you save 8 cent/kWh, summed over all customers we only save 4 cent/kWh.

It gets worse. Electricity demand is quite predictable and follows daily and weekly cycles. Production from solar panels is not that predictable, and has a different pattern every day. The grid operators have to match production to demand, which means regulating down some power plants. Power plants that are idle still cost money but suddenly no money flows in when the sun shines.. What does the power plant operator do to recover these losses? Increase the price per kWh. Your electricity company guarantees that you get power even if the sun doesn't shine - the power plants will have to stay as long as we don't have a better storage solution.

A production/demand pattern that changes frequently can also mean the transmission lines need more capacity, increasing distribution costs. And handing down these costs to the customers, of course.

For you as customer solar power can be worth the investment - you save 8 cent per kWh, and even more if we add taxes. You might even get subsidies if you produce more power than you need, to increase the use of solar power for you even more. That is the calculation you see solar power proponents make. The overall economic use is much smaller: It is the difference between running or not running an existing power plant, something like 1-2 cent per kWh. And I don't see how solar panels are supposed to get that cheap - installation costs alone are at this price level.
If it helps to reduce emissions from coal and gas power plants, I think it is worth the investment, but we wouldn't need solar power to do that.
A reliable method to store electricity would improve things a lot.

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