Into the Night
Verified User
He is correct.Wow. I sure hope you don't give anyone electrical advice.
He is describing 140W of sunlight, not 140W of panel capacity.The cells efficiency is how much of the solar energy it receives is turned into electricity.
The panel rating is how much it can produce in perfect conditions. A panel rated for maximum 140 watts can produce 140 watts but only when it is receiving the roughly maximum 1000 watts of sunlight.
But let's look at your 23.24 watts claim. That means that a 140 watt panel can only produce 24wh which would mean that in 10 hours of sunlight it would only produce 120whs of electricity.
Correct. You actually need more.The average home in the US uses 28.9kwh per day. that would mean the average home would need 240 140watt solar panels to produce enough energy for their daily use. We know that isn't true.
The Sun isn't at peak angle for the solar panel for 10 hours. Attempted proof by contrivance.The average number of panels a home needs is roughly 20 larger panels . Let's do the math. 140whs per panel times 10 hours of sunlight times 20 panels gives us 28kwhs. So your claim that a 140w panel only produces 23.24 watts is utter nonsense. Of course the actual calculation is much more complex in calculating the amount of production needed to meet that 28kwhs.
Irrelevant. Straw man fallacy.But then when I pull out my copy of the NEC, I find that 690.8 gives the way to calculate the maximum current and source currents support the fact that the panels can produce 140 watts if rated at 140 watts since the current is calculated using the maximum current is calculated using the short circuit current. Nothing in the code says the output must be adjusted by the efficiency. The code says the cable size needs to be based on the calculated maximum current. There would be no reason for the NEC to require the cable size should be based on 22% of the amperage that could ever be produced.
No so simple. Synchronization MUST be maintained with the grid. Significant producers must coordinate with the grid dispatcher BEFORE connecting to the grid.Further the NEC code goes on to say the the disconnect must be able to be switched on and off with a breaker or manually operated switch. This simple disconnect is precisely what I said exists and could easily be turned on or off as a connection to the grid.
This safety is required by the NEC and your electrical company and must completely isolate the solar panel from the power line. An improperly wired transfer switch puts utility workers at risk. They will tend to place shorting jumpers while working on the line anyway, and if you are connected there goes your system! THAT damage is permanent.But I can also talk from personal experience. Most panels on residential homes are 320 watts or more such as this one of which I have 24 on my house. https://silfabsolar.com/sla-m-320/. The rated max is 320. The normal rating is 240. On September 29, the panel production varied from .963kwh to 1.24kwh per panel. The lower panels are blocked by trees in the late afternoon so their production is less. The sun was basically up for 12 hours that day. At a roughly 20% efficiency the max any panel could have produced using your method is .768kwh and that is assuming they were getting direct sunlight the entire 12 hours. In reality, the majority of the production is from 9-5 with the panels averaging over 200wh at noon. I have a single switch that can take my system off grid. There is also a built in safety that automatically takes my system off grid if the grid goes down.
What do you think would shut down portions of the array? It would be the inverter which is likely to be a smart device. That means it can sense changes and respond quickly to those changes. Changes in voltage and current can be detected and compensated for. It means the entire system panel shut down because one portion has stopped producing. You can find a ton of videos online of people testing solar panels with parts of the panel blocked to see how it affects production. None of the videos show production for the panel to stop when a portion is completely blocked.
Solar panels must be protected from the weather and the elements, and have a limited lifespan. Sand, snow, ice, rain, debris, bugs and other pests all serve to ruin solar panel installations and the panels themselves.
Panels on rooftops are also dangerous. You can't walk on them, making it difficult to clean off leaves, moss, deal with pests, etc.
You get NO power when the Sun is down. That means NO power for cooking, heating, or even using your computer. You only get something like peak power even possible when the Sun is at an optimal angle to the panel.