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Should Solar PV owner be able to profit off selling excess power?
- Thread starter nwdiver
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- Energy Environment Policy
mknox
Well-Known Member
It used to be even higher (over 50 cents) and these are 20 year contracts too. This is not without controversy. The difference between market rates and the FIT rate get thrown into a bucket and socialized across all customers as a kind of "tax" on the bill. The idea was to make the payback for customers come out to something like 7 years, and as the capital costs for solar PV goes down, so does the FIT rate (which is adjusted roughly annually) to keep the payback time-frame the same. There are similar incentives for larger scale renewable projects including wind, micro-hydro etc. The cost of electricity has really shot up here due to policies like this made by our government and imposed through the regulator, but then Ontario has been able to retire all coal fired plants.
inottawa
Member
And therein lies the rub. It is very possible to go to a more renewable future (still need those peaker plants though!), but at what cost?
Interestingly we have approx. 7 year payback here too for solar PV, but that's due to really good solar insolance, and ridiculously high regular electric rates. The way California has squared the circle without massive public backlash is that they have an extremely progressive rate structure for electric use. If you live in an apartment and use just a little bit of electricity, you might pay $0.12/kWh, but folks with a suburban home will pay $.40/kWh in the summer.
I'm out of my expertise here, but I think it's the case that if you use Grid-tie inverters, then you lose all power if your grid connection goes down. If you lose power much, keeping the systems independent could have value as backup.
mknox
Well-Known Member
My brother lives up in Riverside and I was looking at his bill a couple of weeks ago. Surprised to see his rates were actually lower than mine in Ontario, Canada. Riverside is a municipally owned utility and not part of SoCal Edison, so that may be a part of it. No TOU either... just a two tier rate.
Designing a 'high power' system which will be capable of charging a Tesla @12kw minimum for the 6 hour solar day might be 'too powerful' for a normal connection to the grid. PoCo might require a commercial interface or just say 'the rural neighborhood can't handle it'. My pole pig is of the larger variety usually found in ranch hookups so that is a plus. But all the hassle of creating the grid tie *for the solar setup* is not outweighed by the puny payback possibilities. Why even bother?
Radians, etc. Thanks for these pointers- will persue!
> I'm out of my expertise here, but I think it's the case that if you use Grid-tie inverters, then you lose all power if your grid connection goes down. If you lose power much, keeping the systems independent could have value as backup [Robert.Boston]
I did not know this. Another good reason to keep this rural system off grid.
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I believe, as a safety feature, grid tie systems do not operate so as to not put energy into the grid when the grid is down. I understand that this is to protect the linemen in the event of an outage. I have often wondered if the 60hz signal that the grid tie inverter syncs to could be spoofed so the inverter would supply local power during a blackout. From reading the Radians information, that may be what it does. I would imagine it also has an automatic disconnect switch so there is no possibility of backfeeding the grid. I have seen these type of swiches at Home Depot to be used for generator backups. The other unknown issue is load management. With a grid tie inverter, excess power goes into the grid and with net metering can be used when there is cloud cover. I would be interested in the cost of load sharing devices in wycolo's proposed system.
I have installed two PV solar systems and in the process of converting one of them from net metering to virtual net metering. I understand the bureaucratic dark hole of dealing with the public utility. In my case with SCE, I have a financial incentive ($150/month) to dive into this hole. Wycolo's circumstances may be different.
I have installed two PV solar systems and in the process of converting one of them from net metering to virtual net metering. I understand the bureaucratic dark hole of dealing with the public utility. In my case with SCE, I have a financial incentive ($150/month) to dive into this hole. Wycolo's circumstances may be different.
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I have a sheet metal 'logic' plate, made for my particular breaker box, that locks the main breaker OFF as long as the genset output is being fed into one of the breakers on the main panel. This is foolproof. I have my doubts about any such automatic arrangement being PoCo approved. Need more info in any case.
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Oh yes, some municipal owned utilities actually have sane pricing structures. Palo Alto had $0.05/kWh not too long ago. Here in San Diego, we are stuck with SDG&E which does things like mothball a huge nuclear reactor a few years into its design life and then manages to convince the regulator to make ratepayers pay for it AND give the utility a rate of return for the "investment". Criminal in my mind, but it just complicated enough that no one knows they are getting the shaft.
We're getting off-topic here... we might need a new DIY section for threads like this...
Anyway... grid-tie inverters do need a 'grid' to operate. Unlike off-grid inverters they need a voltage source to produce power AND none that I'm aware of can self-regulate. If there's 8kW available from the PV array that's what they're producing. That's where the AC coupling I mentioned comes in. Two off-grid inverters that I'm aware of (Radian & Magnum Energy) are able to 'AC Couple' meaning that they can simulate the grid and sync with a grid-tie inverter. This makes off-grid systems MUCH cheaper. I spent ~$2k on a 4kW inverter + $600 on some deep cycle batteries and BAM I've got up to ~12kW of power available (with my existing 8kW array) if the grid fails.
An independent off-grid system would have cost nearly twice as much, would have been much less efficient and I would only have ~4kW of AC power available. During the summer months if there is a grid failure, during daylight hours, I can run my HVAC solely off the 8kW SMA with the remaining power sent to the batteries via my 4kW off-grid inverter. SMA inverters are ~96% efficient (PV=>240vac) vs ~80% efficiency of off-grid systems (PV=>48vdc=>240vac).
The Achilles heel of commercially available pure off-grid systems is that the highest voltage input inverters you can get is 48v. That's ~100 amps @ ~5kW. You also need a charge controller which adds to the cost. Grid-tie inverters aren't much more expensive than a charge controller and AC coupling allows you to use a grid-tie inverter instead of a charge controller.
http://magnumenergy.com/wp-content/uploads/2013/06/AN-0002-AC-Coupling-Rev-5-10.pdf
http://www.outbackpower.com/applications/ac-coupling
Anyway... grid-tie inverters do need a 'grid' to operate. Unlike off-grid inverters they need a voltage source to produce power AND none that I'm aware of can self-regulate. If there's 8kW available from the PV array that's what they're producing. That's where the AC coupling I mentioned comes in. Two off-grid inverters that I'm aware of (Radian & Magnum Energy) are able to 'AC Couple' meaning that they can simulate the grid and sync with a grid-tie inverter. This makes off-grid systems MUCH cheaper. I spent ~$2k on a 4kW inverter + $600 on some deep cycle batteries and BAM I've got up to ~12kW of power available (with my existing 8kW array) if the grid fails.
An independent off-grid system would have cost nearly twice as much, would have been much less efficient and I would only have ~4kW of AC power available. During the summer months if there is a grid failure, during daylight hours, I can run my HVAC solely off the 8kW SMA with the remaining power sent to the batteries via my 4kW off-grid inverter. SMA inverters are ~96% efficient (PV=>240vac) vs ~80% efficiency of off-grid systems (PV=>48vdc=>240vac).
The Achilles heel of commercially available pure off-grid systems is that the highest voltage input inverters you can get is 48v. That's ~100 amps @ ~5kW. You also need a charge controller which adds to the cost. Grid-tie inverters aren't much more expensive than a charge controller and AC coupling allows you to use a grid-tie inverter instead of a charge controller.
http://magnumenergy.com/wp-content/uploads/2013/06/AN-0002-AC-Coupling-Rev-5-10.pdf
http://www.outbackpower.com/applications/ac-coupling
Johann Koeber
Happy Owner
No. (In German 'Nein.' Is a complete sentence. No offence intended.)
To me the grid is the giant battery (unlimited capacity) that I am missing. When stationary storage becomes feasible, it might be replaced 80-90%.
100 % would be too expensive. And unreliable. What if my inverter breaks? The grid is my backup.
dhrivnak
Active Member
Not entirely true as the SMA Sunny Boy TL series has a secure power feature. It is not perfect but if the grid is down I can throw a switch on the inverter and have two 1500W circuits available for back-up power. You can see detail on the driving on sunshine poll. And if you have not voted yet please do so. Driving on Sunshine - Page 7
SUNNY BOY 3000TL-US / 3800TL-US / 4000TL-US / 5000TL-US / 6000TL-US / 7000TL-US / 7700TL-US
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Yes, that's true... I was specifically referring to the ability to access the entire output of your array... 'Whole house' vs 1.5kW...
While I agree that your calculations make sense, maintaining the grid is itself a huge expense. Currently that cost is shared among nearly all electric power users, so the cost seems quite manageable, per person. If most customers are 80-90% self-reliant, though, that huge centralized expense has to be borne by the remaining 10-20% of usage, and so the unit cost of the central grid will rise 4x or more, which makes going off-grid completely look even more economic. This "death spiral" is what has some utility executives and commissioners very worried.
How did Germany deal with the scenerio that Robert Boston articulates? I have heard there were benefits there from having distributed production.
I agree that maintaining the grid is a huge expense. The problem I see is that there is no incentive for the public utilites to manage their costs because their return is based on assets deployed.
I agree that maintaining the grid is a huge expense. The problem I see is that there is no incentive for the public utilites to manage their costs because their return is based on assets deployed.
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This many times over!
Being all electric at this time with geothermal heat and electric vehicles and living in a northern location with a significant heating season, I can cover my annual usage with solar in a "normal" year, but would need upward of 5 to 6 Mwh of battery to make it through a bad winter. So far this very cloudy December I have logged only 13.9 hours of sunshine and have drawn 1,923 Kwhs of banked solar power from my virtual battery with 750 Kwhs of that being for vehicles alone. I don't expect batteries to make off-grid affordable anytime soon for anyone living in the northern half of the country and not using fossil fuel/wood for heat.
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