The graph is from the electric company website showing my usage for a single day last week. It was sunny all last week, so pretty much every day's usage looks like that graph. The little peaks around 1pm are when I made lunch since I can't run the electric range from the power station. I could have run things for about 3-4 more hours from the power station, but I like to end the day with it charged to at least 90% in case I need to use it for a power outage.
This is just my trial PV setup with 800W of PV on the south-facing side of the house and another 800W on the west-facing side so I get a pretty continuous 600W throughout the day. I'm currently using an Anker Power Station which is limited to 60V and 600 watts of input, so I'm not getting the most out of my PV panels.
Today I ordered two, big 16 KWh batteries and a 10KW inverter to finally start my "big boy" PV installation (for comparison, that's 32x the capacity of this power station and 5x the total wattage in addition to supporting 220v split-phase). That will let me take better advantage of the panels since I can put all 8 in series for less losses (partial shading notwithstanding).
I've been planning on building this out all winter and am finally seeing it through. Totally unrelated (/s), but my electric rate just got hiked another $0.01/KWh so I wanted to get this in place before A/C season kicks in.
I think its common to think about these min-max scenarios about squeezing every bit of efficiency out of a solar system deployment. I encourage others to go down this through process, but don't get too discouraged at the end when you start looking about why this gets really complicated really quickly.
In your example of trying to bypass the PC power supply and feed DC power directly to the PC, I can think of a number of challenges to that working (or being reliable).
Even if you're avoiding the switch from DC to AC and then back to DC inside the computer, that does nothing to step down the voltage produced by the panels. In a PC you need the following voltages 3.3V, 5V, 5Vsb, -12V, and +12V. On a PV solar system, you'd get anywhere from 18v on a single small panel, to 60v on a large panel, to 400v on a whole residential array.
Just because the panels are producing DC doesn't mean its necessarily clean. DC just means the current flow never switches direction. Lets say you set up a whole bunch of buck converters to produce all the right voltages to feed an ATX power supply. What happens when you get a cloud shadow moving across the array and the power produced drops for a few seconds? PCs are expecting very clean, very predictable power. That voltage sag would likely be enough to interrupt the operation of the PC.
Would it be possible to engineer a high quality power supply with enough capacitance and batteries to provide clean power from solar? Sure, but that's a pretty complicated engineering exercise. You've already go two very well designed power systems: the inverter(s) from your array and your PC power supply. The only cost is 3% DC to AC conversion loss.
Unless you constantly want to be messing with your solar deployment, you quickly realize that reliability is usually the state to optimize for. Get your system working at a decent expected state that will stay working without intervention for a long long time. Optimize elsewhere.
Thanks for taking the time to reply :)
The idea is that you would use the 48v off of the battery array, the charge controller side takes care of dealing with the fluctuating power from the panels and the linked DC power supply handles the conversion from the 48v output of the battery to the various voltages required by the PC.
Same with the supply voltage drops, the battery is providing the stability and so major voltage swings are unlikely.
You're right that it is a tiny increases in efficiency. A 3% conversion loss on the inverters and a 5-10% loss on the AC to DC conversion isn't anything major, it'd only add about 5-10 minutes of battery life across a day (not counting the cooling costs of the heat conversion due to the increased inefficiencies).
This is mostly a quest for niche gadgets and a way to explore/lean the technology. I would almost certainly start with a bog standard solar battery setup.