Solar Power for Air Condition System

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CameraMan said:
So, the bulk of my electric bill every month in the summer time comes from running the air conditioner. In fact my bill doubles... Almost triples because of the AC. I've been thinking about putting the AC system on solar power. What information do I need to get about my AC system in order to purchase the correct solar power setup. I'm seeing 400 Watt systems but the description says it will only work smaller devices and such. Where do I find this information?
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80 posts and no one has gone into the other direction to save money: better insulation.

A few years ago we added a foot of insulation in the attic of my mom/aunt's second home, as well replaced the 13 60 year old windows. One 6k BTU window unit in the living room kept the house (900' sq) at or below 75* even in July/August. It helped more in the winter as the house has baseboard heat. Cost was ~$5k (a company did the windows, we did the insulation), and there is zero upkeep.

If you have central air older than ~15 years, you'd also see savings there by replacing it, and making sure the ductwork is properly installed.

A complete 400W solar kit with 4 batteries looks to be between 1500 and 2000 dollars, but the one Im looking at provides an average of 1600 watt-hours, which is only enough to run a 6k BTU (6.5A @ 120V) window unit for about 2 hours a day. That package's inverter can handle 1500W/3k surge, it's the panels and batteries that limit the run time. For central air that draws 15-25A @ 240V, you'd need an inverter more along the lines 5kw/10kw (or more) surge.

eta: the info you'd need from your AC is its RLA, multiplied by the voltage, to get your running KW. Surge or start-up current could be 5x that number for a few moments; no idea if an inverter that is properly sized for the running current could withstand a surge 2.5x its rating (which is already twice its operating wattage). Istm you'd have to get an inverter that is sized by its peak wattage to run an HVAC unit.
 
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Once again... you really don't need the batteries. A grid-tied system is best at offsetting air-conditioning loads (as compared to other loads) since generally hot weather coincides with sunshine. Hardly any upkeep to a grid-tied system either.
 
electrofelon said:
Yeah they are pretty cool. Definitely more of a utility scale thing. Is anyone aware of any functioning installations?
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How long can they spin without any external intervention? If (for example) you power up one of these things and it spins at 10,000 rpm, how fast will it be spinning after 4 months?

The magnetic field that makes for 'frictionless' actions requires energy. So, instead of loss from friction, there will be loss from maintaining a magnetic field. There is no free lunch.
 
K8MHZ said:
How long can they spin without any external intervention? If (for example) you power up one of these things and it spins at 10,000 rpm, how fast will it be spinning after 4 months?

The magnetic field that makes for 'frictionless' actions requires energy. So, instead of loss from friction, there will be loss from maintaining a magnetic field. There is no free lunch.
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Very true. TANSTAAFL. The Moon is a Harsh Mistress by Robert Heinlein.
 
electrofelon said:
Yeah they are pretty cool. Definitely more of a utility scale thing. Is anyone aware of any functioning installations?
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This moving off topic. SolarPV converts energy. Flywheels store energy that you have to provide in the first place.

But I'll try to give an answer.
A few years ago we got an order for a 1500V, 600A low ripple DC supply. This was testing flywheel energy storage systems. I don't know what the individual ratings were but a number of them were powered up at the same time from our DC supply. The flywheels were run up in concrete pits. Just as well. I saw several disintegrate. The funding for this research project was withdrawn and none went into service.
 
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