Help Request for unique system requirements

Lance_Carbuncle · April 2016

Hello everyone. I hope I am posting this in the right forum. I need a little help understanding how inverters work or which might be suitable for our situation. I have an indoor facility for raising lizards of all things, and use a lot of electricity for basking lights. Each cage uses a 50-75 watt halogen spotlight to provide basking heat for diurnal reptiles. We are building a small off grid building and I would like to build a stand alone solar powered system to provide this lighting. Since we follow the natural solar cycle, we really only need to have lights on when the sun is out.

Right now we are using 110 volt halogen lamps. I would be excited if I could learn that an inverter would simply convert the DC voltage to AC voltage, and then simply dim the lights when there isn't enough power to run them at full voltage.... this would provide a natural cycle indoors as clouds and weather influence the sunlight supply.

I am guessing that rather than reduce ac voltage, the inverter will probably shut off when the power drops below a preset minimum. Can someone let me know if this is indeed the case, or I can source an inverter that could do what i need it to do?

My other thought was to switch to 12 volt halogen lighting and just connect directly to a 12 volt parallel array.... but this severely limits my panel and bulb selection.

Thanks in advance, Lance

solar_dave · April 2016

It would be interesting to see if your bulbs might work on DC directly.

Some of the problems with direct use of solar energy is cloudy days with very low output and Cloud edge effect with higher than normal output. I have not seen a controller that works without the battery bank to buffer those highs and low effectively. I think even with 12V lighting you will need a battery setup to at least act as a buffer. The charge and discharge depth could be fairly shallow since night the usage is not required, you just need to watch the cloudy day issues of battery deep discharge.

AC is much easier to work with, I assume you use timers to control the living now?

mike95490 · April 2016

What happens on cloudy days, when the {V generates no power, and the lizards cool off ?

Vic · April 2016

mike95490 said:

What happens on cloudy days, when the {V generates no power, and the lizards cool off ?

My guess is that the lizards will pretend that it is a cloudy, sunless day, and stay inside and play pool, or something(?).

But, whatta I know? Vic

Lance_Carbuncle · April 2016

mike95490 said:

What happens on cloudy days, when the {V generates no power, and the lizards cool off ?

Yes, exactly..... they have cold cloudy days in nature and they stay under their rocks... and come out when the sun comes out... so it would be perfectly normal for them. I will have propane space heat to keep the minimum room temperature where it needs to be. Because they are cold blooded, then need an high heat source to be able to thermo-regulate.

Dave: I had thought about using a small battery bank as a buffer but was hoping it wouldn't be necessary. I guess I could use a low voltage disconnect to keep it from deep discharging when there is extended periods of cloudiness. I live in San Diego, so it wouldn't be often.

Lance

Lance_Carbuncle · April 2016

solar_dave said:

It would be interesting to see if your bulbs might work on DC directly.

AC is much easier to work with, I assume you use timers to control the living now?

I hadn't even considered that DC voltage might drive a halogen bulb designed for AC.... might have to get out my power supply and give it a try.

Right now I use a solar sensor that runs a relay, which switches the lights on at dawn and off at dusk.

BTW, I forgot to mention that there will be 24 50 watt bulbs, so approx 1,200 watts required to run the bulbs at full power.

Lance_Carbuncle · April 2016

So back to the idea of running a halogen bulb with DC..... I did some googling and it seems they might just work on DC as well as AC.

My thought would be to try running 3 x Kyocera Ku265 in series, (3x38.3v) so approx 115v DC ..... might be an interesting experiment.

Does anyone want to help me try to guess how many 50 watt bulbs I could keep running fairly bright with a system this size and little or no battery backup? I would be happy if I could run two bulbs per panel but don't know if that's enough reserve capacity.

Lance

littleharbor2 · April 2016

Check your specs again on that panel again voc=38.3 but vmp-31.0 giving you 93 volts max under load, probably less on typical warm San Diego days. Panels in the 300 + wattage range are typically 72 cell panels which have the voltage you are looking for in three panels. Or possibly try using four 250 watt size panels giving you more like 120 volts under load.

Help Request for unique system requirements

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