Staged charge / discharge cycles

[Sparky]

By way of analogy: most people who use computers understand that there are different storage levels (RAM vs Hard Disk vs Thumb drives, for instance) and they have different speeds for different price points.

What would it cost and what would the benefits be, if we took a similar approach to electricity storage? Could we connect systems with diverse power storage capabilities within a home or vandwelling?

For example: An Air Conditioner's compressor motor needs x watts to turn, but x+y watts to start from zero; would it be beneficial to wire in a capacitor bank to handle that spike? (High upfront cost; but may offer longevity...) A longer term, lower requirement device (say a low-watt fridge) might be run fine with a less capable power storage device, so we use the most capable storage where it's needed most, and put the cheap storage where cheap storage is acceptable.

I'm not talking about multiple solar systems per se; let the Air Conditioner's capacitors charge via 'mains', and after they provide for the surge, the AC pulls from the same 'mains'.

 

[Hedges]

By way of analogy: most people who use computers understand that there are different storage levels (RAM vs Hard Disk vs Thumb drives, for instance) and they have different speeds for different price points.

What would it cost and what would the benefits be, if we took a similar approach to electricity storage? Could we connect systems with diverse power storage capabilities within a home or vandwelling?

For example: An Air Conditioner's compressor motor needs x watts to turn, but x+y watts to start from zero; would it be beneficial to wire in a capacitor bank to handle that spike? (High upfront cost; but may offer longevity...) A longer term, lower requirement device (say a low-watt fridge) might be run fine with a less capable power storage device, so we use the most capable storage where it's needed most, and put the cheap storage where cheap storage is acceptable.

I'm not talking about multiple solar systems per se; let the Air Conditioner's capacitors charge via 'mains', and after they provide for the surge, the AC pulls from the same 'mains'.

AC reverses polarity every 1/120 second. A motor draws a surge for about 1/16th of a second. So a capacitor on the AC line doesn't get to store power over several cycles and then supply a surge for motor starting. It can be used to cancel "reactive" power, current drawn out of phase with voltage, reducing IR drop and current demand from the inverter. A starting capacitor and running capacitor could help.

Putting capacitor on battery side of inverter could help, reducing current draw from batteries and through cables.

Appliance motors which are inverter driven can ramp up gradually, eliminating surge. The VFD on my 2 HP pool pump takes a number of seconds to ramp up to 60 Hz, 3600 RPM. They can also run at an optimized lower speed and power. But, mostly they run off DC from a capacitor, rectified from AC (just pulling current from peak of sine wave.) Ideally, they would synthesize a "real" or resistive load by pulling current proportional to voltage and boosting it to the capacitor.

Tricks may help you make a home run off a cheap lightweight inverter. If you don't mind spending the money, you can get one which has no trouble starting anything you can reasonably throw at it. Good inverters are $5000, cheap inverters are $500. Some people report 20 to 30 years operation and still going strong.

Batteries are likely to be your largest capital cost and ongoing expense. Designing the system to utilize power as it is generated from PV, minimizing battery cycling and drain during darkness is the place to focus.