recommendations for for micro solar electric project

[Dagmar]

Hi,

New to the forum. Have lived off grid for several years and sort of know what to expect from solar electric, but need some help designing a tiny system for an off-grid application in a remote subtropical rainforest environment.

System would be used to provide minimal power (charging of cell phone, some LED lights and a few rechargeable hand tools) to a tiny cabin that receives significant but sporadic sunlight. I have seen similar setups in the area often using a single panel and a couple of deep cycle batteries. Would prefer to have AC available. Just need some recommendations for a simple (and reasonably priced) charge controller and inverter to complement the single flexible 124W panel I am considering in the first incarnation of this system. Back-up charging through a Honda EU Series 900W generator. Bonus points if the recommended equipment is versatile enough to add additional panels and batteries at a later date. I'll take what I can get though!

Thanks!

[Mike90250]

There are only 2 ways to expand a system:

* build minimally, and discard and upgrade as you expand

* overbuild at the beginning, and slowly grow into it.

For AC, consider the small, pure sine inverters, Exeltech or Suresine 300 that have pretty high efficiencies. That will get the most out of the batteries, and pure sine does not burn up small electronics like mod-sine can.

[Dagmar]

Thanks Mike.

I suppose that the minimal build is the way to go for me. Frugality being key and the possibility of theft in such a location makes me want to keep it small and cheap.

Any suggestions as to a usable charge controller for such an application? Single 124W panel and a couple of batteries. And the ability to plug in a little 900W generator to charge and take up slack for high demand applications.

There are only 2 ways to expand a system:

* build minimally, and discard and upgrade as you expand

* overbuild at the beginning, and slowly grow into it.

For AC, consider the small, pure sine inverters, Exeltech or Suresine 300 that have pretty high efficiencies. That will get the most out of the batteries, and pure sine does not burn up small electronics like mod-sine can.

[Mike90250]

Do you need 120VAC, or do you have "car chargers" for your gear ? Saves the cost of a $250 inverter, if you have car chargers.

$80 Battery (big box store Marine battery) 80ah (you could go up to almost 120Ah of battery, but more, you will not be able to recharge)

$10 Fuse kit with fuse

$10 misc wire, crimp terminals

$80 3 stage battery charger (AC powered) [ 900W genset, powering a charger with .6PF (power factor) means a 35A charger is all you can power. If your battery was 50% drained, it would take about 2 hours of generator time, to get it close to full. Charging becomes less efficient as the battery fills up closer to full.] The longer your battery sits below 75% of full, the more sulfation damage it incurs.

$100 Quality, name brand 3 stage PV charge controller

You already have a panel ? Make sure it's about 18V Max Power voltage, and about 22V open circuit voltage. Those are the right specs for a 12V battery system, if the voltage is higher - you will actually harvest LESS watts, because of mismatch, which could be solved with a MPPT charge controller. ($250 +)

[Dagmar]

Thanks again for all the info!

I do need 120VAC.

No panel yet. Was thinking of going flexible for shipping convenience, light weight and low-profile. At first I considered the Uni-Solar PowerBond PVL-136 (or actually it's 124W cousin that seems to have gone out of production). But now I see that would be better suited for a 24V system. There is a 68W version. For purposes of total usable power and frugality, which would be the better option? A 24V system with the larger panel, or a 12V with maybe 2 of the 68W?

Much appreciation for your patience. I'm no electrician and only have any experience with a much larger, older 24V system that was set up years ago.

[Mike90250]

Uni-Solar PowerBond PVL-136 (or actually it's 124W cousin that seems to have gone out of production). But now I see that would be better suited for a 24V system. There is a 68W version. For purposes of total usable power and frugality, which would be the better option? A 24V system with the larger panel, or a 12V with maybe 2 of the 68W?

The unisolar flexible panels slowly degrade over time, about 20% the first year, and 5% a year after that. There is some thought they produce better in less then perfect light, than regular panels.

Generally, as single large panel will cost less than 2 smaller panels, watt for watt.

A 24 volt system looses any compatibility with 12v gadgets

24v panel on 12v system needs a MPPT controller to harvest the most power.


I don't have an answer for you, but can provide the pro's and con's

[russ]

Unisolar has earned itself a rather bad name on the solar forums - haven't used it myself so I have no personal knowledge.

[Dagmar]

Thanks for the tip about Unisolar. I'm getting that impression the more people I talk to about them.