system advice needed

blazeddragon

i want to make a system to at 1st run 1 to 2 5v dc fans. these will be used to cool my bearded dragons cage and eventually want to expand the system to cover his cages 121 max w/hr consumption.

fan specs:
5v dc
.1 - .3 a. i used .3 in my calculations
1.3 watts

fan(s) will be on for 12 hours per day.

cage power usage:
2x 23w florescent
1 75w halogen on a dimmer

i thought about using a 6v system to start with then move to a 12v one.

need help with panel choice, wiring, and controller options(if needed).

BB.

Re: system advice needed

Welcome to the forum B-dragon!

It is very difficult to slowly "expand" an off grid solar power system... Battery capacity needs to increase. Small charge controller needs to be replaced with a larger one. Larger solar panels may not be compatible with smaller solar panels (need a second, more expensive MPPT charge controller, etc.).

And, things that run 24x7 frequently use many times more power than those items that take a lot of power but only run a handful of minutes per day (i.e., a laptop computer can use several times as much energy vs a microwave oven that runs a few 10's of minutes a day.

For AC power, it would be really helpful for you to measure your daily usage (in Watt*Hours or kWH) with a Kill-a-Watt type meter.

If you want to run these 12 hours per day:

2x 23w florescent
1 75w halogen on a dimmer

• 2*23w + 75w = 121 Watts
• 121 watts * 12 hours per day = 1,452 Watt*Hours = 1.45 kWH per day

That is around the same amount of power as a full sized energy star refrigerator would use. That is not a "small" amount of power. If you doubled that (lights, washer, well pump, computer, etc.)--That would be enough to power an entire (very efficient) smallish off grid home.

The fans are on the other side of the power usage curve:

• 0.3 amps * 5 volts * 12 hours = 18 Watt*Hours per day

Or about 1/100th the amount of power as for the lights... Not a very easy system to "scale" from a tiny amount of 5 volt power to a fair amount of 120 VAC power.

-Bill

blazeddragon

Re: system advice needed

Would it be easier to just power the fans and leave it at that or start with 12v dc fans and go from there or suck it up n just pay the electric company for the 5v fans?

NorthGuy

Re: system advice needed

blazeddragon wrote: »

Would it be easier to just power the fans and leave it at that or start with 12v dc fans and go from there or suck it up n just pay the electric company for the 5v fans?

Paying for fans will probably cost you around $0.60/year. Unless you're interested in learning how to build solar systems, it would be a very good choice.

BB.

Re: system advice needed

It depends on your needs... 120 VAC fans--bypass the whole need for any voltage conversion... You can use batteries+inverter for backup.

Or 12 volt computer fan on a small battery bank--Other than the battery charger, no need for more electronics/hardware.

5 volt fans. Usually very small and little air flow (volume). If using Lead Acid batteries, most solar charge controller are a minimum of 12 volts, so you would need another small down converter (like a USB power supply adapter).

All would work... Just depends on your needs (reliability, fans run in power outage, cost, available equipment, future needs, etc.).

I think you will find 12 volt battery system a bit more practical and useful for other needs. 5-6 volt system is pretty specific to your loads and you will not find much in the way of "off the shelf" solar hardware (don't know of a solar charge controller that will charge 6 volts of lead acid batteries).

If you will be having a "larger" backup power system--Many times, just going 120 VAC is going to be the easiest to support (cell phone chargers, easier to send power more than a few 10's of feet, etc.).

In terms of learning--There are many switching power supplies available now that are much more efficient, especially with greater voltage drops (i.e., 12 volt to 5 volts) vs using the older 3-Terminal "analog" series/shunt type regulators (i.e., for best efficiency, you would want a 6 volt battery to 5 volt fan series regulator).

-Bill

blazeddragon

Re: system advice needed

using 12v fans would not be a problem, i need to cool a area of ~2'x2'x2x by ~10 to 15 degrees. i think 120vfans would be serious overkill, maybe i'm wrong here. will look more into 120v fans after work tonight.

NorthGuy

Re: system advice needed

blazeddragon wrote: »

using 12v fans would not be a problem, i need to cool a area of ~2'x2'x2x by ~10 to 15 degrees. i think 120vfans would be serious overkill, maybe i'm wrong here. will look more into 120v fans after work tonight.

Do you want to make it cooler than ambient by 10 to 15 degrees, or do you want to remove heat produced by a lamp (or other heat source)?

blazeddragon

Re: system advice needed

there is a 23w fluorescent bulb on that side of the cage. the other side of the cage has a 75w halogen creating heat along with a 23w uvb bulb. the "cool" side of the tank runs ~10 to 15 degrees hotter than it should. will post a pic of cage when i get home if needed. also going to a grid system is not out of the question, just as of right now it is.