Equipment recommendations for desert heat

System · May 2010

I've been following the forum for a while, gathering information to put together a small system here in the Phoenix, AZ area. From what I've learned, heat will be a problem. Please comment on the following thoughts:

1. It appears that mono crystalline PV panels are a better choice than others when handling heat.

2. It also appears that the benefits of an MPPT charge controller may be less when working in a hot climate rather than a cool one.

3. Batteries are going to need to be inside where it's cooler.

4. Desert heat may also require larger gauges of low voltage wire.

5. For a 24 volt system (batteries, inverter) I'm looking at Sharp 230 w panels,
Open Circuit Voltage (Voc) 37.0 V
Maximum Power Voltage (Vpm) 30.0 V
Short Circuit Current (Isc) 8.40 A
Maximum Power Current (Ipm) 7.67 A
Does that sound like a good choice?

I've also read that the Xantrex Trace inverters, although modified sine wave, generate their wave using a lot more steps than other MSW inverters, and are much closer to true sine wave. I'm looking to run laptop computers, satellite tv system, and LCD TV. Will the Xantrex be okay for that?

Thanks for your help. I've answered a lot of my questions by reading, but these I'd like more informed opinions on while planning a course of action.

Thanks!

mike95490 · May 2010

Re: Equipment recommendations for desert heat

1) no opinion

2. It also appears that the benefits of an MPPT charge controller may be less when working in a hot climate rather than a cool one.

Only the winter thermal/power gain, in desert, you can still run a 70V array (lower amps = smaller wires)

3. Batteries are going to need to be inside where it's cooler.

Balance against the venting requirements

4. Desert heat may also require larger gauges of low voltage wire.

I don't understand this thought at all

5. For a 24 volt system (batteries, inverter) I'm looking at Sharp 230 w panels,
Open Circuit Voltage (Voc) 37.0 V
Maximum Power Voltage (Vpm) 30.0 V
Short Circuit Current (Isc) 8.40 A
Maximum Power Current (Ipm) 7.67 A
Does that sound like a good choice?

For panels in parallel, NOT good. In summer heat, your panels may fall below the voltages needed to equalize.

So, this is a completely off grid cabin or full time house?

niel · May 2010

Re: Equipment recommendations for desert heat

1> to me not a factor.

2> no matter as you just put 2 pvs in series to double the voltage.

3> if venting is a problem you can go with agm batteries and there will also be less heat generated from them as they are more efficient than fla batteries.

4> the temps may require you to have a higher temp rating on the wire, but we like to go with large wires anyway to overcome voltage drops.

5> a pv is a pv if the power, pricing, and warranty are to your liking. they will work.

as to modsine i think you'll be able to use it. a sine wave inverter would be necessary if you have items sensitive to the waveform such as fans, motors, and compressors. some plug in wall adapters may also be sensitive depending on the adapter and the item it may power.

BB. · May 2010

Re: Equipment recommendations for desert heat

The Xantrex/Trace line of inverters--That merger was long ago and there are few of those units (if any) still in production.

Basically, a True Sine Wave inverter is defined as having less than 5% harmonic distortion. MSW will, typically, have much higher than 5% distortion. That is the "number" you should look at.

You can read a couple of inverter FAQ's to get a better idea of why it matters (and why TSW are usually the better choice, even if they are much more expensive).

All About Inverters
Choosing an inverter for water pumping

-Bill

blackswan555 · May 2010

Re: Equipment recommendations for desert heat

For the panels the numbers you want to be comparing are the below, how much you lose per deg, as you can see , about 1/2 a % per deg on those,

Temperature Coeffi cient (Pmax) -0.485% / °C
Temperature Coeffi cient (Voc) -0.36% / °C
Temperature Coeffi cient (lsc) 0.053% / °C

CC, I do not know about the other`s but the earlier outback MX series was rated @ 25 c and the later current FM series @ 40 c so would still be a reasonable investment in my opinion
.

Inverter, Again I would go outback, It`s good kit and the after sales / warrantee/ serviceability /tech help is second to none
Tim

Solar Guppy · May 2010

Re: Equipment recommendations for desert heat

Thermally speaking, Outback would be my LAST choice, I have owned both Outback and Xantrex inverters, there is no comparison, the Outback if run anywhere near rated power one could almost use for a cook top, just check out the derating that the CEC has for the FX series of inverters.

As for the MX/FM series of Outback charge controllers, even with the little noisy fans they run very hot, both the Xantrex XW and Morningstar TS-Mppt run cooler and that's without having fans in the controller, both of the later are UL rated for 45C ambient conditions for continuous maximum power

Overall. Outback is now closing in on 8 years on the age of there designs, and there are may other manufactures that are UL/CSA/FCC listed that would be a much better choice

Dave Angelini · May 2010

Re: Equipment recommendations for desert heat

Solar Guppy wrote: »

Thermally speaking, Outback would be my LAST choice, I have owned both Outback and Xantrex inverters, there is no comparison, the Outback if run anywhere near rated power one could almost use for a cook top, just check out the derating that the CEC has for the FX series of inverters.

As for the MX/FM series of Outback charge controllers, even with the little noisy fans they run very hot, both the Xantrex XW and Morningstar TS-Mppt run cooler and that's without having fans in the controller, both of the later are UL rated for 45C ambient conditions for continuous maximum power

Overall. Outback is now closing in on 8 years on the age of there designs, and there are may other manufactures that are UL/CSA/FCC listed that would be a much better choice

DITTO !
I have a buddy south of Tucson near Tombstone running 2 3KW XW cc's into
the XW system in an uninsulated power shed with Surrettes and he is very happy!
This not the best thing to do letting batteries get that warm, but that is the one battery I would do this to.

System2 · May 2010

Re: Equipment recommendations for desert heat

mike90045 wrote: »

1) no opinion

Only the winter thermal/power gain, in desert, you can still run a 70V array (lower amps = smaller wires)

Balance against the venting requirements

For panels in parallel, NOT good. In summer heat, your panels may fall below the voltages needed to equalize.

So, this is a completely off grid cabin or full time house?

So you recommend I series connect two panels for about 70v output?
Then the charge controller can drop output for the 24v battery bank?

This is a full time house. I plan on setting up a sub panel in the house and moving a couple of circuits to it, such as computer plug/router/ Radio-modem, and a lighting circuit. It would be totally separate from the Grid portion.

System2 · May 2010

Re: Equipment recommendations for desert heat

niel wrote: »

3> if venting is a problem you can go with agm batteries and there will also be less heat generated from them as they are more efficient than fla batteries.

I was more concerned about how the ambient heat would affect the storage batteries, not heat output from the batteries. I was planning on putting them in an insulated, enclosed patio room that I could actually pipe some A/C to without too much trouble.

System2 · May 2010

Re: Equipment recommendations for desert heat

Solar Guppy wrote: »

Thermally speaking, Outback would be my LAST choice, I have owned both Outback and Xantrex inverters, there is no comparison, the Outback if run anywhere near rated power one could almost use for a cook top, just check out the derating that the CEC has for the FX series of inverters.

Have you had or heard of anyone's experience with the SAMLEX inverters, such as the SA-2000K-124? They make inexpensive true sine wave inverters.

Thanks for all your help and info.

Vic · May 2010

Re: Equipment recommendations for desert heat

AZ,

Regarding the, "SAMLEX inverters, such as the SA-2000K-124" This has just been touched on in another post on this Forum.

It appears that the THIS series inverter is not well suited for FLA batteries, or for COLD batteries, as the inverter shuts down when the battery voltage reaches or exceeds 30 VDC Battery Voltage ( or at 15.00 VDC for the 12 V version). This is too low to allow an Equalize charge for Vented batteries, and can be exceeded during an asorb cycle for cold batteries, as well.

You should consider this situation when selecting inverters, IMHO.

Good Luck, Vic

Equipment recommendations for desert heat

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