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RegGuheert
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How to increase the *fraction* of roofs covered?

Fri Feb 21, 2014 4:58 am

In the discussion about the Ivanpah plant, Guy and I have been discussing the fraction of "impervious" surfaces you would need to cover with PV in order provide the amount of electricity used by the U.S. It's a big fraction, even assuming infinite, efficient storage: ~16%.

I am becoming more-and-more convinced that PV on existing structures is one of the least damaging forms of electricity generation available today. But that discussion got me thinking about the barriers out there that are keeping us from putting more PV on our roofs. One thing that strikes me is that while our roof already has 10 kW of PV installed, it could hold about 3X that amount (without installing on the North-facing portion). The current amount of PV almost provides the amount of electricity we use annually, but if we could triple the size of the array, we could provide for two more houses across the street which are in the woods.

But how could that be made practical? In theory, we could simply add the panels but our net-metering laws only permit residential installations up to 10 kW. But even if that limit did not exist, they also do not pay for production beyond our own consumption. But why should the power company be allowed to collect ALL the income for electricity which we produce? It makes sense for them charging for its distribution, but at the current price of PV, it would makes sense to install PV if we could be paid retail-minus-distribution.

Does anyone here produce more electricity than they consume? (Note that while I am not talking about zeroing your bill by producing a fraction of your consumption under a TOU plan, a discussion of producing beyond that amount to match or exceed usage fits here, too.) If so, how much do you get paid for the overage?

Is there any legislation out there that encourages the coverage of ALL flat or South-, East- and West-facing unshaded roofs on houses, barns, factories, warehouses, etc., even if it will result in production beyond consumption? If so, what and where are they? (Note that the East- and West-facing roofs only carry about a 15% production penalty if located on a roof that is not too steep. In fact, in some weather regimes in which there is more cloudiness in the morning or afternoon, the East- or West- facing surfaces can produce MORE electricity then the South-facing one.)
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

Phoenix
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Re: How to increase the *fraction* of roofs covered?

Fri Feb 21, 2014 5:20 am

PG&E in California will pay 4 cents if you generate more electricity than you use. They don't want competition in generating electricity. Hence their policies do not encourage conservation of usage or enlargening rooftop solar systems.

downeykp
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Re: How to increase the *fraction* of roofs covered?

Fri Feb 21, 2014 5:45 am

My 10.3 kw system on the Big Island is producing after 7 months 529 more kw than I am using. Thus saving me +\- $250 a month. Remember, this is just for lights a refrigerator and hot water. So I am putting 537kw back into the system and really getting nothing for it.
The power companies in Hawaii are really starting to complain that they are having a hard time using all of the excess generation. They are even starting to hold up letting systems be installed and charging high fees to homeowners for studies to be done and upgrades to the system that the customer might have to pay.
If the power company were paying me for the excess at the rate I pay for the energy I would have had to buy I would be getting $233 a month back. But I know that would not happen. Wholesale would be half of that.
So in short, the kWh I send back to them (for free is sent to someone else and they are charged $.44 a kWh. What a deal.
Like you, I have a north facing roof on a 2 to 12 pitch and another south facing roof that could easily handle another 20 kw.
2011 Black Leaf SL+QC Vin. 1931
Res. 6-14-10 Order 1-25-11
EVSE: Mod'd Ver. 2 Nissan L1
Delivered 5-31-11

7 years 33000mi. 8 bars

39 Suniva panels 10.3kw with Enphase micro inverters my electricity cost $21.87 a month.

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LTLFTcomposite
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Re: How to increase the *fraction* of roofs covered?

Fri Feb 21, 2014 6:57 am

I have two questions:

#1: Let's say PV panels became so cheap everyone was putting them in, and each person could generate a net amount equal to their consumption, but we still wanted everything to be grid connected because the storage problem was largely unresolved. Setting aside the issue that some storage is still needed somewhere, what percentage of my existing electric cost goes to generation and what part goes to building and maintaining the transmission system?

#2 Go to any Costco and see they have palettes of flat panel TVs literally stacked to the rafters. If there were half the enthusiasm for installing PV as we had for getting the next bigger screen size, shouldn't solar panels be a lot cheaper than flat panel TVs?
LTL
White 2012 SV delivered 10 Dec 2011 returned 25 Nov 2014 replaced with stopgap ICE Sentra
[35 months] [35K miles] [9 Bars]
2013 Volt replaced after 36 months/30k miles with ICE Rogue
2016 SV-adjacent May 2016 lost 4th bar March 2018

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DNAinaGoodWay
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Re: How to increase the *fraction* of roofs covered?

Fri Feb 21, 2014 7:01 am

With 6.72 kW ground mount, we were able to produce 99.3% of our avg usage, until we got the LEAF, so now we're thinking about adding 7-8 more panels, or just waiting for the teenagers to graduate.

Here, excess production won't be paid for, but can be allocated to any user on the same utility. Whole solar farms exist that offset usage somewhere else. If you had that, maybe you could find a way to work out the payment details with your neighbors or whoever.

As for HI, the utilities could save cost by shutting down generators during the day.
'12 SL last reading @ 2 yr, 22k, 260 GIDs, 62.35 Ahr

'15 SV w/QC, Mfd 5/14, Leased 8/14, 292 GIDs, 64.38 Ahr when new
@ 36 months, 34k, 270 GID, 57.49 Ahr

'17 Bolt LT



6.72 kW Array

Smidge204
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Re: How to increase the *fraction* of roofs covered?

Fri Feb 21, 2014 8:09 am

RegGuheert wrote:In the discussion about the Ivanpah plant, Guy and I have been discussing the fraction of "impervious" surfaces you would need to cover with PV in order provide the amount of electricity used by the U.S. It's a big fraction, even assuming infinite, efficient storage: ~16%.


The Wiki states that the figure given (110,000 km^2) is "Urban." So reasonably this figure includes only areas within major city limits. In other words, you'd have to cover 16% of the cities in PV.

There are roughly 130.6 million residences in the US. ~67% of these are single family homes, with another 18% being between 2-20 units (condos or small apartment buildings).

The average size for single family houses is about 2,400 square feet. At 67% of 130.6 million, that's 210 billion square feet, or about 20 billion square meters.

20,000,000,000 sq.m. * 1 KW/sq.m. * 0.15 PV efficiency * 4 hours/day * 365 days/year = 4,380,000,000 MWh/year.

That's more than the 3,886,400,000 MWh/year quoted in the other thread. For single family homes only.

Granted, not every roof is suitable and the entire area of a given roof may be suitable. However, if you include structures other than single family homes - especially large commercial and industrial buildings, and parking lots - then that would be handily to make up the difference. You'd even have enough to displace a significant chunk of fossil fuel use through electrification of homes and vehicles, as well as synthetic fuels.
=Smidge=

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Randy
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Re: How to increase the *fraction* of roofs covered?

Fri Feb 21, 2014 9:17 am

LTLFTcomposite wrote:I have two questions:

#1: Let's say PV panels became so cheap everyone was putting them in, and each person could generate a net amount equal to their consumption, but we still wanted everything to be grid connected because the storage problem was largely unresolved. Setting aside the issue that some storage is still needed somewhere, what percentage of my existing electric cost goes to generation and what part goes to building and maintaining the transmission system?



Since I work for the utility in San Diego, here is an observation I find many folks don't think about...

If your scenario was true and in the daytime each and every customer generated their electricity and did not rely on the grid at all during the daylight hours, that would (of course) result in a near zero flow on the grid during those hours. Existing large scale generating plants, however, would still need to be running at minimum output because as the sun starts to go down and solar output drops off, a "new" system peak is created from a utility generation perspective as people get home from work and fire up everything at home....In fact, my personal opinion is that this evening peak will just be a little bit less in the future than the current peak load we see in the afternoon.

And like you said about storage not be economical in large quantities for quite some time, you still need large scale generation in the evenings (in fact there will a large ramp up needed as the system shifts from daytime solar predominance to evening traditional generation), you'll still need relatively the same transmission system, distribution system, etc. in the evenings. I don't see a major cost savings in grid infrastructure by a "super buildout" of solar across the system. It can help during the daytime, of course, but in the evening and night time hours almost the same grid capability will be needed to serve customer load.

That is the reason why (at least here in California), the utility peak load will be shifting over time to be later in the day...I think it's an exciting time to be a utility engineer, as there are many challenges and issues that will need creative solutions in the years ahead...Anyways, just wanted to point that out....

smkettner
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Re: How to increase the *fraction* of roofs covered?

Fri Feb 21, 2014 9:44 am

LTLFTcomposite wrote:#2 Go to any Costco and see they have palettes of flat panel TVs literally stacked to the rafters. If there were half the enthusiasm for installing PV as we had for getting the next bigger screen size, shouldn't solar panels be a lot cheaper than flat panel TVs?


65" 220w tv at Costco -> $1,230
65" 235w solar panel (solarblvd) -> $174
1 bar lost at 21,451 miles, 16 months.
2 bar lost at 35,339 miles, 25 months.
LEAF traded at 45,400 miles for a RAV4-EV
I-Pace on order for end of 2018 delivery

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LTLFTcomposite
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Re: How to increase the *fraction* of roofs covered?

Fri Feb 21, 2014 9:48 am

What creates the big loads in the evenings? Here in FL I think it would mostly be air conditioning, particularly as LEDs take over in lighting and TVs.

Maybe instead of trying to store electricity we should be storing "cold", with residential A/C systems that freeze a tank of water into ice during the day then use that to cool the house at night.
LTL
White 2012 SV delivered 10 Dec 2011 returned 25 Nov 2014 replaced with stopgap ICE Sentra
[35 months] [35K miles] [9 Bars]
2013 Volt replaced after 36 months/30k miles with ICE Rogue
2016 SV-adjacent May 2016 lost 4th bar March 2018

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RegGuheert
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Re: How to increase the *fraction* of roofs covered?

Fri Feb 21, 2014 11:42 am

LTLFTcomposite wrote:#1: Let's say PV panels became so cheap everyone was putting them in, and each person could generate a net amount equal to their consumption, but we still wanted everything to be grid connected because the storage problem was largely unresolved. Setting aside the issue that some storage is still needed somewhere, what percentage of my existing electric cost goes to generation and what part goes to building and maintaining the transmission system?
My bill shows these prices (it is simple):

Distribution/Delivery: $5.45/month + $0.02243/kWh
Electricity Supply Service: Energy Charge = $0.03918/kWh + Wholesale Power Cost Adjustment = $0.03236/kWh

That means there is:

Flat $5.45/month connection fee
24% for distribution (transmission)
42% for energy (fuel?)
34% for electricity generation (power plants?)

So it looks like the distribution portion includes the connection fee plus ~25% of the total per-kWh fee.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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