DIY solar - to - grid tie

[shovel]

OK dumb question time (but I couldn't find useful info online..)

I would love to buy a kW of solar panel, to connect to a little 5000btu window a/c unit, to keep my bedroom cool. I live in Phoenix and my bedroom is upstairs so it stays hot all the time, and I figure if I can keep it cool for "free" during the day that will take a heck of a load off the central A/C, day and night (in the evening, it won't have to cool off all the items with mass such as furniture, clothes, etc)

However it's just simply not in the cards right now to front cost for something that will take 5+ years to pay off. I know that's not TOO long but I just can't afford it today.

What I can afford today is a ~200w panel and I already own a computer UPS. - I don't use the UPS anymore because I only have a laptop nowadays.

The UPS contains a pair of rather large sealed 12v batteries, together they are as large as the battery in my S10.

I don't know a ton about electronics, but I was thinking, can I feed a regulated 12v from the solar panels to the batteries in the UPS as a "grid tie" to partially offset the load of whatever is connected to it? Or are the batteries disconnected during normal operation?

Thanks!

[cfg83]

shovel -

I don't have info in front of me but I think this is a great idea. This way you can have a blackout-proof "safe room" in the summer.

Were you thinking of using a DC off-the-grid Air Conditioner to bypass the requirement of an inverter?

I'm having trouble finding a reasonably priced one. This is NOT an option ($4K!!!) but it does meet your BTU spec :

Sunspot 5000

CarloSW2

[shovel]

Originally Posted by cfg83

Were you thinking of using a DC off-the-grid Air Conditioner to bypass the requirement of an inverter?

I was mostly thinking, since i already have a UPS and I can easily acquire a 200W panel... my A/C draws ~500w in operation, so 500 minus 200 is 300 roughly. In other words, my net electrical requirement from mains power would (potentially) be 300w if UPS's work that way.

It would not be "blackout proof" as the a/c unit still draws considerably more current continuously during operation than the panel is able to produce.. but if it reduces my operating costs - that's fine by me.

Presumably I'd need some type of diode to keep energy flowing in the "right" direction... well, this is the part I would need to research & am willing to do, but I just can't seem to find data on whether or not a UPS can even be hacked to work this way in the first place.

Otherwise, I may still use the UPS as a simple inverter/storage to run something less power hungry, completely isolated from the grid. A/C is simply the most attractive because it's a constant, necessary, and expensive load. (necessary to keep significant other happy, she doesn't give a damn about saving money/energy)

[Daox]

You can't split the current draw like that. It is either going to be 500W from the battery, or 500W from the grid. I'd consider using the power supply maybe for lighting at night or something with a lower power requirement.

[captainslug]

Originally Posted by shovel

5000btu window a/c unit

After having lived in Arizona for 6 years I'm under the impression that phase-change air conditioning never worked properly unless you had it set below 65F. I don't remember if you can you get small swamp coolers or other evaporative coolers, but those might work much better and draw far less power.

[shovel]

Online ("True") UPS

This looks like it answers my question.... looks like there are UPS' which constantly flow through the 12v circuit, but their own efficiency losses may exceed any benefit I would receive - not to mention I do not have enough understanding of electronics to know if one can "balance" the load between the mains-supplied converter and the solar (so each can provide "x" number of watts to the battery at the same time as each other) - it would be easy to install a gated relay that disconnects the converter from the charge circuit any time battery power exceeds 11v and reconnects it to charge the battery under 11v ... but then I would by cycling the battery endlessly which is probably not good for it. Big capacitors? I can obtain 1F 20V caps through my employer for about 12 bucks.... that would eliminate the cycle problem as well as the charging resistance... but may introduce a whole other bag of problems.

THIS is what I want.... Solar in a Box pity it's not made yet

[cfg83]

shovel -

(these URLs do NOT address your initial question, but they give other people info that may read this thread)

Here is a website I have been tracking for years that is still too expen$ive, *and* it doesn't appear to be on sale yet (bad sign) :

SolCool - Solar Air Conditioners

The gizmo is not an evaporative cooler in the pure sense of the word. It is a a system that I *think* is based on automobile Air Conditioner tech, which is DC based.

Here is a company that is selling the "pure" evaporative cooler (swamp cooler) that runs off a few solar panels :

SolaCool

I have been wanting to "try" the evaporative cooler because of the comparatively lower cost, but I can't get seem to find any customer feedback on how smelly or efficient it is.

They also sell the "safe room" package for mondo money :

Solar Safe Room

CarloSW2

[NachtRitter]

Originally Posted by cfg83

....

Here is a website I have been tracking for years that is still too expen$ive, *and* it doesn't appear to be on sale yet (bad sign) :

SolCool - Solar Air Conditioners

The gizmo is not an evaporative cooler in the pure sense of the word. It is a a system that I *think* is based on automobile Air Conditioner tech, which is DC based.
....

CarloSW2

Not sure how much I would trust a company that also sells products which make claims like this one: SolCool Store: EMBEDDED ION TIRE VALVE STEM CAPS with NANO TECHNOLOGY [fms_1] - $69.95

[captainslug]

Originally Posted by cfg83

I have been wanting to "try" the evaporative cooler because of the comparatively lower cost, but I can't get seem to find any customer feedback on how smelly or efficient it is.

They work extremely well provided the outside humidity is below 20%. Normal maintenance cycles are very simplistic.

[shovel]

Originally Posted by NachtRitter

Not sure how much I would trust a company that makes claims like this: SolCool Store: EMBEDDED ION TIRE VALVE STEM CAPS with NANO TECHNOLOGY [fms_1] - $69.95

..... BWAHAHAHAHAHAHAHAHAHAHHAHAHAHAHAHAH

I BET PEOPLE ACTUALLY BUY THOSE THINGS TOO!!!