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wk057,
Wonderful project! I have been following it for quite some time. Congratulations for getting all the solar on line.
I was wondering if you had considered splitting it into two independent systems? You already have two load panels, each with their own transfer switch. The benefit would be in case of a failure, only half the circuits would be out (or running from the grid). You could even wire one of the charge controllers to be switchable between the two systems to ensure that neither battery bank gets too low of a state of charge.
I was wondering if you had considered splitting it into two independent systems? You already have two load panels, each with their own transfer switch. The benefit would be in case of a failure, only half the circuits would be out (or running from the grid). You could even wire one of the charge controllers to be switchable between the two systems to ensure that neither battery bank gets too low of a state of charge.
Well, there you have it, it is unique, in this great country of ours, that you would find different solutions because of local politics. I have heard the term, "Energy Democracy" used to describe the choice to choose where we want to get our energy. That is why I have solar panels and drive electric cars.
.... isn't each charge controller and each inverter already independent? Why would the failure of 1 charge controller or 1 inverter effect the rest of the system?
Awesome to see your panels up. Do you have a way to burnoff excess solar power when your batteries are full and not enough loads to keep charge controllers in constant MPPT mode? You are not planning back-feeding the grid, correct? There may be days when you cannot "absorb" all available solar energy and your daily solar power graph will not show all possible power you could have made which would skew your capacity factor lower than it could have been. I ran into that problem with my 3 panel experimental off-grid setup. To solve this I utilized Aux output on charge controller set up in diversion relay mode. The signal would drive power MOSFET switching on load resistors on DC bus at preset battery voltage. Here is video of it. I think this method can be improved using micro controller for some lithium battery management techniques to prolong battery life.
assuming they can actually pay me real money (not just credit, since that would be useless to me).
...But I don't really see the need to find a way to really do anything with the excess power if I can't do something useful with it. Dumping it into a resistor as heat is basically the same as just not utilizing the power from the array since the panels will get warmer since the power isn't being absorbed... and I don't really see any harm in that since it's what would happen if they just weren't hooked up anyway.
If the credit is sufficient and annual you could use it to reduce the cycling stress on the batteries and displace winter consumption... do you expect to need the grid in the winter?
I had considered it, however the peak loads on each panel would be more than half of the inverter capacity. Max is about ~48kW on the one panel and ~48kW max on the other. In total it would be more than my inverters could handle if every large load were maxed out, but with them as one system I don't really need to worry about it much at all. The chances of me charging both cars while running the over, dryer, both hot water heaters in resistive heat mode, resistive aux heat for all three HVAC units plus their heat pumps, along with the pool pump and other general loads........ is pretty slim.
I could see both cars charging while cooking and doing laundry though, while the HVAC was running which would be over 55kW.
Overall it made more sense to have the whole system be available for handling loads on either panel. My setup can do 64kW continuous, and 72 kW for 30 minutes as a surge rating. Without Model S charging included my max possible load is under the 64kW continuous rating. Since I'm redesigning the HPWC control circuitry to be smarter and work with my system better I will have a few lines of code in there that basically slow charging if charging plus other loads happen to push things above the 64kW mark for very long. In general, though, I bet I could just go about business as usual and it would probably never be a problem.
Now if only these clouds would go away today
Very cool. I like your unistrut based panel racking. That was actually my initial idea as well, but too much work for so many panels.
Currently I have nothing really setup for handling excess power aside from the charge controllers just not taking it in. When that happens I'm going to set it up so that my graph changes color, indicating that it's not the maximum power available. If it turns out this happens often enough (likely will in the summer) then I'm going to investigate a dump into the grid, assuming they can actually pay me real money (not just credit, since that would be useless to me).
My current plan is to utilize existing household items as the initial diversion load in an automated way. Basically, drop or raise the temperature in the house a degree or two utilizing all HVAC systems (~9kW). Heat the hot water another degree or two (5kW if using the resistive elements). Top off the Model S's if they're below 90%, and maybe even bump them to 91 or 92%. Doing laundry or running the dishwasher when this happens would make sense too, although can't really automate that. I plan on getting an electric pool heater (probably 10kW) and will use that (even in the winter, maybe) also if the water isn't already too warm. Basically plenty of normal things I can think to dump power into.
If I still have excess beyond all that... well, not much I can about it I guess, currently. A DC based resistive heater up to 44kW would be pretty crazy. Could heat the neighborhood. But I don't really see the need to find a way to really do anything with the excess power if I can't do something useful with it. Dumping it into a resistor as heat is basically the same as just not utilizing the power from the array since the panels will get warmer since the power isn't being absorbed... and I don't really see any harm in that since it's what would happen if they just weren't hooked up anyway.
I'm wondering why you photo shopped your back yard by your pool and solar array with trees?
How does the model S react to changes of the pilot signal that communicates max current allowed? I assume it will adjust down. Will it automatically adjust up?
Does temperature impact the longevity of the panels? (Solar newbie here). Sounds like you need more batteries
Jason,
I'm wondering why you photo shopped your back yard by your pool and solar array with trees?
Is this some weird form of spam?
If you really think he Photoshopped it take a look at some video and see the same trees.
Solar Install - 28.7kW Ground System (Residential) - Part 1 - YouTube