Home Solar System to Achieve Energy Usage Offset

SpaceNut · 2024-07-14 20:00:30

The monocrystaline solar are said to be the best performer with shade so one needs to see if the issue is at the panel joiner box or down the connection of the power wall.

Calculating How Many Solar Panels You Need

To determine how many solar panels you need, you'll need your annual kWh usage, which you can find by adding up your monthly kWh for January through December from your electricity bill. Alternatively, you can use the NREL PVWatts calculator, which offers a close estimate by looking at several advanced factors.
You'll also need the production ratio of your region or the amount of electricity produced by solar panels under common weather conditions near your address. Thankfully, there isn't much of a fluctuation throughout the United States and you can use the following maximum production ratios from clean energy provider EnergySage:
Northeast: 1.3
Pacific Northwest: 1.15
Southwest: 1.8
Mid-Atlantic: 1.35
Southeast: 1.5
Mountain West: 1.6
West Coast: 1.8
Midwest: 1.3
Finally, you'll need the solar panel's wattage. Divide the annual total wattage needed by the production ratio and then divide that by the wattage of your panels. For this example, let's go with the average of 400 watts per panel. Using an address in Las Vegas as an example, you'll divide 7,157 kWh by 1.8 by 400 W to get approximately 10 panels.

All of which we must then calculate the power wall sizing for how long it might be needed for.

tahanson43206 · 2024-07-15 05:48:01

For SpaceNut ....

As a follow up to your interesting observation....

kbd512 has reported actual experience with the equipment ...

You used the term "reported to be" ....

kbd512 has "reported" that the solar panels installed in his facility work fine with full sunlight but do not perform in overcast conditions.

I expect we can deduce that there is no problem with hardware downstream from the panels.

If the hardware works when the Sun is shining, it will be just as capable when the Sun's light is absorbed by clouds.

Please confirm that kbd512 has monocrystaline solar panels?

(th)

Last edited by tahanson43206 (2024-07-15 05:48:45)

RobertDyck · 2024-07-15 11:07:16

I don't believe monocrystaline solar cells are any more efficient in diffuse light than other photovoltaic cells. The issue is solar concentrators. A solar concentrator is a mirror or lens to focus light on a small photovoltaic cell. This allows a larger collection area with a smaller solar cell. Two problems: this greatly heats the solar cell, which greatly nreduces its operational life. And second it doesn't neoel at all with diffuse light. A lense or convex mirror only works with direct light, not diffuse light. So in overcast conditions power from a solar concentrator system drops to near zero. To deal with these issues, just use flat photovoltaic cells. But a triple junction cell should work equally well in direct or diffuse light. Any flat photovoltaic will produce power from whatever light is available.

kbd512 · 2024-07-15 15:38:12

I don't know what's supposed to happen, but I do know what actually happened, because we didn't have any power in the middle of the day, during an overcast yet still very bright day. It wasn't as if the "sky turned dark" or something like that. Looking up at the clouds in the sky was painfully blinding. We still had no power at all, either during the day or at night from the Tesla PowerWall batteries. If something else was supposed to happen, then it didn't.

We do have monocrystalline panels. I know the difference between the two. I have solar powered garden lights with both monocrystalline and polycrystalline cells. The panels on our roof are what I said they are. Our two Tesla PowerWalls are exactly what's printed on them, and they look like all the other Tesla PowerWalls I've seen.

Our initial installation took place in 2021. The roof was recently replaced, after which all panels were reinstalled and some newer or repaired equipment provided by the solar installers. If it's not "working", then I'm not sure how or why we had power on clear / cloudless days. On the days that were clear, we had power during the day and at night (enough to run our refrigerator, a couple of fans, and to recharge our cell phones). On the days that were overcast, we had neither. Period. End of.

The system is of the "grid tie" variety, but since there was no functional grid at all during any of those days, I seriously doubt that any of the generated power was fed back into the grid. Each panel has its own micro inverter, and as I understand it there's both an over and under voltage cutoff. Maybe the under-voltage cutoff is what prevented the panels from powering the refrigerator back up, but that is only a guess on my part.

For the days that we did have power, running what little we did would drain the batteries by around 7AM to 7:30AM, and then at around 9AM the power from the panels would come back and the refrigerator would power back up. We unplugged everything we could unplug, except for what we were running. After the power died early in the morning, the fans were also unplugged and not plugged back in until it was time to go to sleep around midnight. The refrigerator was the only appliance we kept plugged in at all times.

Anyway, we now have grid power back, it's clear outside, and we can see on the app that the panels are providing power and charging the batteries.

My only hope for the installation, beyond lowering our power bills to something affordable (which it did), was that it would keep the refrigerator going and allow us to recharge our cell phones. Plugging in a couple of box fans for it to run at night was more than the system could handle. We threw out all the food and medications for my wife in our refrigerator, because it spoiled due to no power.

All in all, it didn't do very much, considering the enormous amount of money spent on it.

Terraformer · 2024-07-15 16:05:23

Oh! I think I know. Grid tied systems are designed to shut down if the grid shuts down, to avoid sending power into it when work is being done.

kbd512 · 2024-07-15 19:53:57

The day the grid was restored, it was cloudy outside during the morning, so we had no power. By the afternoon, it was sunny outside. Wonder of wonders, the refrigerator had power again (after almost 3 days of not having power). The damn solar system was "ON" the entire time that they were working on the power lines. How do I "know this"? The stupid refrigerator had power. It didn't do any good by then, but once again, the fridge had power.

The following are my personal observations of our home solar system's function between July 8th, 2024 to July 13th, 2024:

Monday morning (after Hurricane Beryl passed), Tuesday, Wednesday - fridge has power (not overcast)
Thursday, Friday, Saturday morning - fridge off (overcast)
Saturday afternoon - fridge has power (not overcast)
Saturday evening - grid power finally restored (not overcast); fridge on before / during / after the lights come back on (maybe it shouldn't have been, and maybe that was dangerous for our linemen, but the fridge was definitely "O-N" at that time

Our home solar system is installed on top of a 3 story single family home located in the northwest of Houston, Texas. It includes 67 panels and 2 Tesla Power Walls. None of the panels are shaded. It's a corner house on top of a small hill, but still higher than the surrounding homes. The house in question has approximately 6,500ft^2 of interior space, IIRC. The equipment was installed by a company named "Sunrun Solar", 9331 Hwy 6 STE 190, Houston, TX 77095. They're "The #1 home solar & battery company in America" (over 900,000 installations), according to their website. I am neither claiming nor insinuating that anything is wrong with either the company or their equipment or the services they've provided to us. As far as I'm concerned, their system works. The panels in question have shrugged off hail storms, hurricane force winds, torrential rain, small tree branches, as well as snow and ice. They provided power today, as a matter of fact, and the sky was also very clear today.

As with all other things in life, terms and conditions apply:
Direct Sunlight = solar panels powering fridge and charging Tesla Power Walls
No Direct Sunlight = fridge has no power, Tesla Power Walls not charging

Maybe, just maybe, most grid-tie monocrystalline solar panels with on-panel power inverters require direct sunlight. If this part of the reality of living with photovoltaic and battery power upsets other people here, perhaps they should take up their beliefs about the equipment with the respective equipment manufacturers. I'm merely the end user of the system, when it works, which from direct observation while grid power normally provided by CenterPoint Energy was quite obviously non-functional, is only when direct sunlight is present. That's the simple and obvious explanation for what I directly observed.

tahanson43206 · 2024-07-16 04:41:39

For kbd512 re #131

Thank you for your detailed reporting on the operation of the solar power service you've installed.

This is a learning opportunity for members of the forum. We (collectively) start from a position of complete (or nearly complete) ignorance.

In the near term, we have an opportunity to learn how a well designed, well installed and well maintained system operates in the Real Universe, if you have the patience to stay with the undertaking.

You have answered SpaceNut's question about the Powerwalls. You have reported that the Powerwalls have functioned as designed.

However, Terraformer's question about connection to the grid is interesting, and your report offers an opportunity for us to learn more about that aspect of the designed system installed on your property.

My guess is that the flow of electricity to and from the grid is controlled remotely, using the Internet, but possibly using radio control.

My home has a radio reporting device installed in the power meter, and data from that device is polled (somehow) each month. This system is for reporting only, and it does not control the flow of power. If you have time and the subject is of interest to you, please find out how the power flow is controlled. My guess is that the default configuration is to prevent flow of power into the grid, so that when grid power is absent, the flow of electricity to the grid is cut off. The answer to that would be good to know.

(th)

tahanson43206 · 2024-07-16 05:11:46

Gemini is Google's enhancement to their search engine. It is permitted to access the Internet, which is not the case with ChatGPT.

I asked Gemini to see if it could find out how net metering works when power is lost on the grid.

Hello Again! I have a question that may be a good match for your abilities. A member of a group who are corresponding over the Internet has a solar power installation with 70+ panels and 2 Power walls. He has reported his observations of the performance of the system during the recent power outage in Houston, Texas. A question was posed by a correspondent about the control of flow of electricity to and from the grid. My guess is that the flow of power is controlled remotely by a computer at the power company, and that the default behavior would be to NOT deliver power to the grid when the grid Is down. Please investigate to see if information is available on how the flow of electricity to and from the grid is controlled.
You're absolutely right! The flow of electricity to and from the grid is a complex process, but I can help you understand the general principles and how it might apply to a residential solar system with Powerwalls during a power outage.
Here's a breakdown of the key points:
Grid Management: The flow of electricity on the power grid is carefully monitored and controlled by a central entity called the Independent System Operator (ISO) or a similar organization. They use sophisticated computer systems to balance supply and demand in real-time.
Anti-Islanding Protection: For safety reasons, most residential solar systems with battery backup have a feature called "anti-islanding protection." This feature automatically disconnects the solar system from the grid when it detects a power outage. This prevents the solar system from inadvertently energizing downed power lines, which could pose a safety hazard to utility workers and others.
Powerwall Behavior During Outage: Tesla Powerwalls are designed to provide backup power to a home during a grid outage. When the grid goes down, the anti-islanding protection disconnects the solar system, and the Powerwall automatically starts supplying power to the house.
Islanding Capabilities (Some Systems): It's important to note that some advanced solar inverter systems with battery backup can be configured to operate in "islanding mode" during a power outage. However, this typically requires additional equipment and permitting from the utility company, and it's not a common feature for residential systems due to safety concerns.
In summary:
For your friend's setup with 70+ panels and 2 Powerwalls, it's highly likely that the system would have disconnected from the grid during the Houston outage due to anti-islanding protection. The Powerwalls would then have taken over supplying electricity to the house.
Here are some resources where you can find more information:
Anti-Islanding Protection: https://ieeexplore.ieee.org/document/8591807
Tesla Powerwall Features: https://www.tesla.com/powerwall
I hope this explanation clarifies how electricity flow is controlled on the grid and how it applies to residential solar systems with battery backup during outages. Feel free to ask if you have any further questions!
thank you ** very ** much! I am hopeful your easy-to-understand reply will be helpful.
You're welcome! I'm glad I could provide a clear explanation. If you have any other questions related to solar power systems, grid management, or anything else, feel free to ask. I'm always happy to help in any way I can.

(th)

Last edited by tahanson43206 (2024-07-16 05:13:53)

Calliban · 2024-07-16 17:29:19

TH, you rely too heavily on dimwit AIs, that have the IQ of a house fly. Most of what I have seen Chat GPT produce has been garbage. So far at least, the AI revolution appears overhyped.

kbd512 · 2024-07-16 22:09:19

The notion of powering an entire home after a storm, or recharging an EV without grid power, using most or all of the actual setups shown on various slick website advertisements, is unrealistic. The grid is still doing nearly all of the heavy lifting, or the actual performance results don't add up. Since the grid is doing the work, the "real solution" is to either make the grid itself more reliable, or accept that a number of people, mostly women / children /the elderly, are going to die without reliable power.

Assuming the space you have to install solar panels is limited to the roof of your home, they cannot provide sufficient power, unless you live in a desert. If you live some other place which still has significant heat and humidity caused by variable cloud cover / precipitation / proximity to the ocean, such as Houston, then your home solar system will be overwhelmed by the demand placed upon it in fairly short order. The reality of this situation is that the pair of Tesla PowerWalls were suitable for powering a small number of fans, lights, and portable electronic devices. They can't power a refrigerator and pair of box fans at the same time, never mind a central AC unit.

This has fomented a lot of speculation that something is wrong with the system I'm using, but those assertions are incongruent with direct observation of how the system performed when direct sunlight is available. The system I have is by no means "perfect", yet I would assert it out-classes most home solar setups, which have 30 panels or less and no battery backup at all. The pivotal question nobody has asked here is, "What was it actually designed to do?"

My home solar setup was engineered, by a credentialed electrical engineer with 10+ years of experience designing home solar systems, to reduce our power bills to a more affordable fixed monthly value, limited to the cost of the installation loan. It has achieved that objective. For all the other touted benefits, "some terms and conditions apply". The primary economic benefit was achieved. All the other potential benefits produced mixed results.

When we purchased our home system, we evaluated the products being offered by 4 or 5 different companies. Of all the companies making offers, I selected the offer from the company which had an actual electrical engineer show up to our home for a sit-down explanation, with mapping and Excel system sizing software in hand, and a durability demonstration for their photovoltaics to boot. We actually talked about photovoltaic technologies on offer, potential problems, and he showed me his calculations and software program, which he'd written himself.

Is it apparent why I selected that proposal versus the other proposals made by salesmen with glossy brochures?

The other proposals were a little short on the details of how it would work, even though I'm sure their solutions would also provide power. In all cases, the primary motivation- to sell home solar systems, was the same. However, the "stand-out" company's representative thought details mattered enough to send an electrical engineer, rather than a salesman. Well, in the Navy, "attention to detail", is beat into your head 24/7/365. In al technical matters, details matter.

One of the lines that came out of this guy's mouth was something to the effect of, "While we could theoretically install more panels on your roof, and you would get some additional power, real world performance is nearly all that actually matters. I'm not suggesting more panels than this because I don't think it's going to help." This is exactly why you want to talk to an actual engineer, rather than someone with an ideological belief about what they're doing, but they're short on details.

tahanson43206 · 2024-07-17 05:52:30

For kbd512 re Post #135

Thank you for adding additional perspective to your earlier reports on the performance of a high end solar panel installation.

This has been a learning opportunity for NewMars members who are willing to accept Real Universe input.

It seems to me you have answered SpaceNut's question about the Powerwall electricity storage system.

Terraformer offered a question that you have accepted as valid, and in your first response you reported that you did not know the answer to the question. In the spirit of helping our members (and forum readers) to increase knowledge of high end solar systems with net metering, please see if you can find out how the net metering component of your system is configured.

We have speculated that the interface to the grid is managed by the utility, and we have speculated that the interface may be controlled over the Internet. An alternative that is feasible is radio control, but I think that is less likely. There is a third possibility, which is radio over grid wires. That is feasible under some circumstances, but my understanding is that the method fails at transformers that are needed to increase or decrease voltage in the network.

Of particular interest would be the default behavior of the interface at your home. My guess is that the interface would be programmed to deliver all available power to your Powerwall storage when the grid is gone. How the Interface "knows" the grid is gone would be interesting.

Finally, while this is unlikely, it is possible that your interface captures and saves data for some period of time. I would imagine most of that storage is done by the utility at a central station. If your interface ** does ** capture data, it might be possible to discover what it ** saw ** during the outage. Your observation is of the end result, and that is good, but it is anecdotal. If your interface captured data as the outage was underway, including solar flux if that is available, then it should be possible to compare the performance of the system with full Sun and overcast conditions, as well as night time when input is zero.

(th)

SpaceNut · 2024-07-21 14:14:31

A few reasons come to mind for why shadow is causing is as to how the single panels are wired internally as a wired orred (basically shorted together) which means the node currents are source and sinking to the same circuit wire causing the power to become low. If the segments are diode isolated that solves and causes the input to the MPPT that KBD512 has a loading issue such that the trigger voltage is being loaded down by its inputs.

MPPT mppt-vs-pwm_480x480.jpg?v=1685633247

https://www.renewablewise.com/mppt-charge-controller/
ngcb1

https://www.cleanenergyreviews.info/blo … ontrollers

kbd512 · 2024-07-21 19:42:01

Enphase IQ8 Over/Under Voltage Shutdown

Enphase IQ8 Over/Under Voltage Shutdown
I'm noticing my new IQ8+ inverters are shutting down for 5-15 minutes due to over/under voltage according to the system event log. I'm logging the voltage & frequency and don't see a corresponding blip but it's possible the line is out of spec for too short to make it into the logs but long enough to force the IQ8 inverts to halt. It's also possible there's something wrong with the IQ8 inverters or perhaps the default grid profile.
This isn't happening every day. Some days it's not at all, other days it's once an hour and really limits overall production.
Have other people seen this problem? Suggestion on fixes?

Response from Reddit User "solar_brent":

What is the AC voltage as reported by the inverters? And are all inverters going off-line at once, or just a few at a time?
I've seen this before as a result of high voltage from the utility (usually in rural locations where they like to boost the voltage to overcome long line losses between customers)
I've heard of it happening where installers (especially "regular electricians") undersize the wiring, because they are used to targeting 3% "voltage drop" but with the micro-inverters we like to target 1.5% or so in the site-installed wiring.
I have also seen it doe to glitch in grid profile (i.e. enphase firmware problem).

Forum readers are encouraged to read through the entire Reddit post and series of responses.

I'm "guessing" that our micro-inverters are shutting down to protect the batteries. I recall a vague passing reference to this being explained to me by the installers, but that was over 2 years ago and I can't recall everything I was told. I know for a fact that our on-panel micro-inverters have under-voltage and over-voltage protection, which I presume exists to protect our pair of Tesla PowerWalls, but there could be other reasons I'm unaware of, which are related to protecting the grid or all the electronic devices in our house, which seems reasonable to me. It's also possible that the micro-inverters have failed, because some of them initially failed inside of 2 years, long before Hurricane Beryl did its damage.

There may also be some combination of firmware and configuration settings that prevented the panels from producing power during daylight hours. I'm still trying to figure out if there's anything I can do about this.

SpaceNut · 2024-07-22 17:38:24

https://enphase.com/sites/default/files … -DS-US.pdf

https://enphase.com/en-gb/download/iq8m … data-sheet

https://gcframing.com/articles/green-en … l-summary/

https://www.viridisenergy.com/learning- … ifferences

Sounds like if it's going into output over voltage then the load of the powerwall is not heavy enough. Line isolation to line transformers would help to regulate the voltage so that it would not happen.

I am wondering if the overvoltage happens when the powerwall is checking to see if the line is present coming in.

kbd512 · 2024-07-22 18:28:58

SpaceNut,

From my perspective, especially for the amount of money spent, the default operating mode shouldn't be "no power" when power should be available, unless my assumptions about indirect sunlight still providing power were wrong. Rather than arguing reality, I've accepted it. I'm not going to spend any more money on it. The solar system provides power in direct sunlight, or at night if the batteries were charged by direct sunlight during the day. It doesn't do anything else. It's highly likely that was an intentional design feature. Other people who also have on-panel micro-inverters report the exact same behavior from their home solar installations.

This is easy enough to understand, at least for me. The system doesn't work the way most people here think it should, it works the way it needs to work to protect the batteries, all the other home electrical and electronic devices, and the rest of the grid. That limits the conditions under which it functions at all, to direct sunlight. In direct sunlight, it works very well. Under other operating conditions, not so much. It's also highly probable that the micro-inverters are the real culprit here, given that 13 of 67 of them failed in less than 2 years.

SpaceNut · 2024-07-24 19:46:31

Without the panel information I can only say that the input voltage is below 25Volts and that is why the convertor does not output anything. As for saving the batteries of the Powerwall that means not enough power is going out of the system to the grid as to why its ac voltage is so high.

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#126 2024-07-14 20:00:30

Re: Home Solar System to Achieve Energy Usage Offset

#127 2024-07-15 05:48:01

Re: Home Solar System to Achieve Energy Usage Offset

#128 2024-07-15 11:07:16

Re: Home Solar System to Achieve Energy Usage Offset

#129 2024-07-15 15:38:12

Re: Home Solar System to Achieve Energy Usage Offset

#130 2024-07-15 16:05:23

Re: Home Solar System to Achieve Energy Usage Offset

#131 2024-07-15 19:53:57

Re: Home Solar System to Achieve Energy Usage Offset

#132 2024-07-16 04:41:39

Re: Home Solar System to Achieve Energy Usage Offset

#133 2024-07-16 05:11:46

Re: Home Solar System to Achieve Energy Usage Offset

#134 2024-07-16 17:29:19

Re: Home Solar System to Achieve Energy Usage Offset

#135 2024-07-16 22:09:19

Re: Home Solar System to Achieve Energy Usage Offset

#136 2024-07-17 05:52:30

Re: Home Solar System to Achieve Energy Usage Offset

#137 2024-07-21 14:14:31

Re: Home Solar System to Achieve Energy Usage Offset

#138 2024-07-21 19:42:01

Re: Home Solar System to Achieve Energy Usage Offset

#139 2024-07-22 17:38:24

Re: Home Solar System to Achieve Energy Usage Offset

#140 2024-07-22 18:28:58

Re: Home Solar System to Achieve Energy Usage Offset

#141 2024-07-24 19:46:31

Re: Home Solar System to Achieve Energy Usage Offset

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