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NERC sounds alarm on solar tripping in ‘sobering’ summer reliability report

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Re: NERC sounds alarm on solar tripping in ‘sobering’ summer reliability report

#51

Post by kkfx »

ars wrote: post #22

Why is solar thermal so rare?

Because nowadays p.v. is cheap enough to heat enough water with far less maintenance costs and potential issues, at least that's my choice: I was undecided for a bit of time if going p.v. only or p.v. + thermal and in the end:

- with p.v. I'm formally less efficient BUT in winter/cold but still sunny days my p.v. peak at a certain time for a certain time and my water heater start full power when there is enough energy, a solar thermal system take time to reach a sufficient temperature to make water (glicole) flow;

- almost no external maintenance, just panels and wires, no leaks or freeze risks, no pipes etc;

- no extra energy to make heat transfer fluid flow, witch means no pump, actually my heater is just an isolated "bowl" with a heat pump + classic electrical resistance and a big spiral pipe inside, so I have even no pressurized tank issues (water expansion) nor legionella problems etc;

- for my needs 300l of waters heat also in the winter enough 100% on p.v. except if more than two days without Sun, overall cost is very limited, potentially I can use the optional thermal solar integration with a classic wood burning stove to heat water in emergency conditions.

Why bother for thermal solar? With a big pool I understand but except for such case in witch solar anyway can't suffice for more or less large part of the year...

Re: NERC sounds alarm on solar tripping in ‘sobering’ summer reliability report

#52

Post by bitexploder »

toomuchtodo wrote: post #48
bitexploder wrote: post #37

Earlier quoted context omitted.

We ended up with 16kW and solar edge stack. 16kw was about all we could fit on the roof. Was a nightmare getting Xcel to approve it. Took them 2 months. We have 20 kWh of battery to buffer and back us up in the case of extended outages. It is a nice system. Anything over 10k in Colorado requires a lengthier approval process. We also moved the house entirely to heatpumps. They practically sip energy for cooling.

Excellent choices!

It is kind of fun :)

Re: NERC sounds alarm on solar tripping in ‘sobering’ summer reliability report

#53

Post by kkfx »

xxpor wrote: post #38
zeckalpha wrote: post #30

Earlier quoted context omitted.

Specifically, a heat pump water heater.

That usually is true if your electricity is generated by natural gas too and you're comparing it against a gas HWH Rough math is NG -> Electricty is 50% efficient thermally. A heat pump can have a COP of 4.2. 100 * .5 * 4.2 = 210% efficient, thermally A hot water heater powered directly by gas is ~100% efficient thermally.

Personally I do not care about efficiency: I can't sell energy I produce so the point is just heating the water and the load profile of a classic resistance and the load needs of my houses match normally to heat without the heat-pump (witch have a far limited life respect of a classic resistence)...

I use the heat pump mode only when there is little solar for few days where there is not enough overall energy production, otherwise being able to produce 120-130% of the overall consumption (of course ONLY when the Sun shine, so NOT independent as some sell just playing with absolute numbers) why care about efficiency? I can't use the extra energy anyway...

Re: NERC sounds alarm on solar tripping in ‘sobering’ summer reliability report

#54

Post by tremon »

gabereiser wrote: post #47
benglish11 wrote: post #45

Earlier quoted context omitted.

Where are you where you can’t sell excess electricity back to the grid? You definitely can here in SE Pennsylvania. Amongst the few people I know with solar panels on their roof it’s the most common scenario. Several of them have no battery either so they cannot store excess electricity.

Net-metering has only just been introduced in many southern states after much lobbying from power companies against it. Here in Florida (where I am now) it’s illegal to disconnect your house from the grid if you have solar. There’s a minimum “service fee” of $60 from FPL even if you only used $10 of energy. In many other states run by a certain political party, they have been making it so your net-metered connections…

There’s a minimum “service fee” of $60 from FPL even if you only used $10 of energy.

I don't see how this is a problem: the maintenance of the electricity grid must be paid somehow, and this is more or less a flat, predictable cost. If you're coming from a situation where the maintenance was previously factored into the price of energy consumption (not a bad way), you're going to have to redesign your billing.

Are you arguing against a maintenance fee in general or just how much it costs?

Re: NERC sounds alarm on solar tripping in ‘sobering’ summer reliability report

#55

Post by amluto »

Veliladon wrote: post #29
amluto wrote: post #14

Earlier quoted context omitted.

Last year, I had the opportunity to talk to some PG&E-associated contractors [0] who were replacing the distribution transformer serving me. I asked them whether they trusted the anti-islanding protection in everyone’s inverters and whether they would like me to turn off my main breaker. They laughed and said that they couldn’t care less. They were going to intentionally short the secondary circuit if they were doing…

> I’m genuinely unsure what purpose anti-islanding actually serves. Because a typical solar inverter can't handle transient loads. It just spits out whatever power is coming in from the panels. It can't shed if too much is coming in and it can't magically create power to fix a shortfall. The power has gotta go or come from somewhere. If you have a battery you can soak the transient load and disconnect from the grid a…

Shedding excess power is very, very easy for solar, especially as compared to any other power source. The MPPT can move away from the maximum power point. (Compare to, say, wind or hydro where moving a turbine away from its optimal speed and torque can be quite destructive without extreme care. I visited a small hydro installation with a monstrous space heater to dump power in the interval between when a load disappears and when valves can adjust to reduce the flow of water.)

I am curious how SolarEdge’s inverters reduce output, though. It’s not fundamentally hard, but the inverter does not have appear to have a particularly high speed data connection to the MPPTs, and I haven’t found the underlying mechanics documented anywhere. I’m guessing that the inverter pulls the incoming voltage down such that the MPPTs hit their preprogrammed output current limits and curtail production.

(SolarEdge’s system can’t just dump excess power into a battery — their common configurations have the battery behind a DC-DC converter with considerably lower capacity than that of the inverter’s output. The DC-DC can’t fully absorb the solar string’s output if the sun is shining and an island’s load goes away. The battery itself likely could, at least for a little while, but there isn’t any way for the power to get there.)

Re: NERC sounds alarm on solar tripping in ‘sobering’ summer reliability report

#56

Post by malchow »

kkfx wrote: post #50
toomuchtodo wrote: post #9

Earlier quoted context omitted.

I spec’d my 21kw system with IQ8+s for this reason. It’s future proofing distributed generation by being software defined (Enphase’s Ensemble system). Highly recommend them to anyone considering residential solar, and go for as big of a system as you can (and your utility will allow, if they limit based on usage history; tell them you’re buying an EV if necessary).

Consider the peak power of the panel vs the maximum power of the microinverter... My very small p.v. if converted to microinverters from string inverters would be FAR LESS productive due to the maximum power limit of the microinverters, surely they allow "free" panels, mixed with any orientations, many different numbers, even different kind of panels, but they cut much the output to a point they are IMVHO interested…

No, these days microinverters aren't the bottleneck. The IQ7 can handle up to a 460 W module, with 366 VA output. The IQ8 can handle up to a 540 W module, with 384 VA output. 97.6 efficiency.

Re: NERC sounds alarm on solar tripping in ‘sobering’ summer reliability report

#57

Post by malchow »

sbierwagen wrote: post #32
toomuchtodo wrote: post #9

Earlier quoted context omitted.

I spec’d my 21kw system with IQ8+s for this reason. It’s future proofing distributed generation by being software defined (Enphase’s Ensemble system). Highly recommend them to anyone considering residential solar, and go for as big of a system as you can (and your utility will allow, if they limit based on usage history; tell them you’re buying an EV if necessary).

Do you have any battery storage? How well do islanded microinverters handle startup surge on electric motors, or is it the case that you need a 20kw+ array to handle a refrigerator cycling on?

Every IQ micro and battery you add adds more ability to deal with current surge requirements. On my 8.5Kw system with 30KwHr of Enphase LFP batteries, I can handle turning on AC when I have full sun and partially charged batteries without going to the grid.

AC is a difficult load. Get the inrush current here: https://www4.enphase.com/en-us/support/faq/how-support-hvac-... and you will be able to figure it out.

Your refrigerator will be fine. Its locked-rotor amperage requirements are small compared to AC.

Re: NERC sounds alarm on solar tripping in ‘sobering’ summer reliability report

#58

Post by kkfx »

malchow wrote: post #56
kkfx wrote: post #50

Earlier quoted context omitted.

Consider the peak power of the panel vs the maximum power of the microinverter... My very small p.v. if converted to microinverters from string inverters would be FAR LESS productive due to the maximum power limit of the microinverters, surely they allow "free" panels, mixed with any orientations, many different numbers, even different kind of panels, but they cut much the output to a point they are IMVHO interested…

No, these days microinverters aren't the bottleneck. The IQ7 can handle up to a 460 W module, with 366 VA output. The IQ8 can handle up to a 540 W module, with 384 VA output. 97.6 efficiency.

Mh, from Enphase catalogue in my country (France) I do not see such data, the IQ8 are not on sale here and IQ7 variants arrive at maximum at 315 VA for the IQ7X-96-2-INT witch is the top performer on sale here. Anyway, it's still less than classic string inverters even if they give "resilience" and "installation freedom"...

Re: NERC sounds alarm on solar tripping in ‘sobering’ summer reliability report

#59

Post by ars »

zeckalpha wrote: post #30
ip26 wrote: post #24

Earlier quoted context omitted.

Because photovoltaic got so good & cheap, with no moving parts. In most locales it’s now more cost effective to heat your water with photovoltaic panels & an electric water heater.

Specifically, a heat pump water heater.

So I looked into them because of your comment, and they have a very big drawback of taking a very long time to heat the water. That wouldn't work for me, our water usage tends to be very "peaky" - my system can heat the water almost as fast as you can use it in a shower.

Maybe with a very complicated system with an extra large storage tank, and perhaps integrated with the home heat (so a single heat pump). I feel like the tech isn't quite ready yet, and I don't like being a pioneer.

It seems like a no brainier if you heat with electricity, but not quite ready yet for those who heat with natural gas. Right now it seems better suited for southern climates.

Re: NERC sounds alarm on solar tripping in ‘sobering’ summer reliability report

#60

Post by gjvc »

dotancohen wrote: post #42
gjvc wrote: post #41

Earlier quoted context omitted.

> I'm having trouble with the power industry terminology. :-) In the UK, the term "prosumer" is the official term for an electrical system which produces to and consumes power from the supply. (example https://electrical.theiet.org/wiring-matters/years/2019/74-m... ) (In the past it was widely taken to mean "a customer who wants to buy very high-quality technical products or equipment", https://dictionary.cambridge.o…

First context: prosumer: Portmanteau of "producer" and "consumer". Second context: prosumer: Portmanteau of "professional" and "consumer".

i fail to see what your comment adds
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