Solar Power Design Suggestions

[BraveSirRobbin]

Solar Design Suggestions Needed

I have to specify, order, and implement a solar powered system for a field data acquisition project for work. The system will run 24/7 in a remote Nevada area.

Here are some of the system requirements:

• 12 volt DC operated equipment
• 1 amp constant draw all day and night
• Temperature extremes from freezing to 115 deg F (in enclosed field box) during the year.

Here is what I believe to be the needed specifications to meet the above requirements:

1 amp at 24 hours = 24 amp*hr continuous load

Battery will be 75 to 100 amp*hr rated (deep cycle).

Solar panel will be rated at 120 Watts. This will be capable of supplying (120Watt/12Volt) 10 amps of current during the daytime.

Assume worse case of only five hours of daylight this solar panel will yield 5*10 = 50 amp*hours per day (approximately double the 24 amp*hr draw per day by the equipment).

A 10 amp rated pulse width modulation charge controller will be connected between the solar panel and the battery. This will provide diode isolation during the night time (when no current is supplied from the solar panel, thus not providing a discharge path for the battery) as well as voltage regulation as the solar panel can provide a voltage as high as 22 volts during peak sunshine (of course the peak voltage is very dependent on the load as well).

I have two questions.
1) Is a factor of two sufficient between the solar charge capability and the load as this will account for (multiple) cloudy days?

2) Are the parts specified below sufficient for the overall design (any red flags based on user experience or some unknown that I did not take into account)?

I appreciate any input as I’m not familiar with solar systems and thought possibly some of our members might have experience in this field.


Solar Panel:
Mitsubishi 120 Watt Solar Panel PV-MF120EC4

http://www.altersystems.com/catalog/mitsub...ec4-p-1667.html

Here is where I could really use some recommendations. I elected to go to a single panel rather than parallel two 60 Watt units, mainly for ease of installation and cost. Does anyone have a better suggestion (brand/size/type/etc…)?


Charge Controller:

MorningStarr Sunsaver 10 Amp Controller SS-10L-12

http://www.altersystems.com/catalog/sunsav...-lvd-p-347.html

This controller is rated for use up to 60 degrees C (140 F) which is the main reason I like it. It also has the diode (reverse current) protection scheme necessary for the night time.


Battery:

I was initially thinking about a 75 amp-hr deep cycle (blue top) Optima battery, but am wide open to suggestions based on a member’s experience.

Are the Odyssey batteries worth their high price? I’m not looking for cold cranking amp capabilities obviously as I will only be drawing one amp continuous, but would like to have three days or so of reserve power. Plus these batteries do have to operate in extreme heat during the summer months.

Thanks again for any comments and suggestions.

Regards,

BSR

 

[BraveSirRobbin]

Moved topic to Wiring Closet forum bump.

 

[BraveSirRobbin]

Well, here is what I decided on:


Solar Panel: Mitsubishi 120 Watt, PV-MF120EC4

This has a 25 year warranty and a very sturdy frame (for high winds). It is also one of the last panels to come with a junction box in lieu of a connector arrangement.


Charge Controller: MorningStarr SunSaver 15 Amp MPPT, SS-MPPT-15

An MPPT arrangement is superior to a pulse width modulated charge controller, especially for short winter time daylight hours.


Battery:

SunXtender 104 Amp-Hr PVX-1040T
This is made to be discharged/charged via solar power systems (even though you try not to obtain more than a 50% discharge at any time).

 

[electron]

This thread didn't show up in my 'view new posts' query until just now, probably because of the move.

Isn't this a pretty big setup for just 1A@12V?

 

[BraveSirRobbin]

Well, it is overkill, but the main things making it that way are the battery derating at high temperatures (for the battery only run times) and the conversative estimate of only five hours of daylight during winter months for charging.

I'm also slightly skeptical of spending that much money on a battery. I'm getting one complete system in to evaluate so I'll give some updates in the near future.

The conversative estimates though are pretty typical in industry (some go even more conversative).

 

[electron]

What about those Optima Deep Cycle batteries? They are pretty popular and reliable, used to drive carPC's and other aux. equipment.

 

[BraveSirRobbin]

I asked about the Optima deep cycle. Seems they are classified as a "hybrid" and not capable of the continuous charge/discharge that solar batteries are subject to.

Of course any decent battery should work, but the ones specified above should last many more years.

 

[electron]

Cool. Thanks for posting all these details, I really want to start with a small setup as well, but I doubt one of those Harbor Freight kits would be a good start.

 

[DrunkenLizard]

I've been thinking about something like this myself, I want to setup a remote wifi relay site with a couple parabolic antennas. Not sure if solar is going to be sufficient in the winter months up here, Heavy cloud cover for extended periods of time, snow, etc... I'm thinking wind power might help supplement that.

 

[Waynedb]

Good batteries for playing with a small setup are Golf cart batteries(6v around 220 amp ), I used them in my motorhome that I had setup with 4 solar panels on it.
The true deep cycle batteries have big heavy lead plates that can handle the heavy charge and discharge cycles better than the starting/deep cycle hybrid style batteries. If you regularly discharge the battery down to a 50% s.o.c. it will not last nearly as long as a 20%.

For a larger setup you can use something like this http://www.dcbattery.com/rollssurrette_6cs17ps.html , my brother uses these for his house.

 

[BraveSirRobbin]

Yes, I also read about the Deka batteries (used in golf carts) that some use in their solar systems. The specialist at windsun.com said he felt the Concorde Sun-Xtender battery was a better product (plus I only needed just one single 12 volt battery for my applicaiton).

 

[politics123]

Wind-backup?

 

[garylm]

This battery caught my eye the other day. The guys that built the Killacycle drag racing bike have designed a jig for welding together multiple A123 nanophosphate Li Ion cells in series/parallel.

 

[BraveSirRobbin]

This reply was moved from another topic:

Charge current to the battery would be an interesting parameter to measure, especially if more than one solar panel is used.

I would also measure the voltage from each battery if possible.

Graphing the results can also tell you a lot about the panels performance, especially when compared to the solar data.

You will see subtle changes and could diagnose problems before they become major. For instance I graph battery voltages (12 volt single battery system) on various solar charged panels (for work). As you can see in the graph below the "ASP" voltages for Site 6 are less then Sites 3 and 8 (identical current draws). The battery is old and had a pretty good load on it before it was able to charge, and would never be able to regain its "full" charged voltage. I have read this can occur on certain batteries if they are drawn down to under 50% of their capacity. Over the course of four days you could see the small decrease in the waveform's peak voltage.

Also, you can see in the ASP voltages that those panels are slightly undersized for the load. Thus their graphs don't have the sharp increase in voltage as their "SYSTEM" counterpart's graphs. This helped me size newer correct solar panels (which I started a thread on here), plus other peripherals including charge controllers and battery types.

Anyway this is probably more than you wanted to know, but I'm just now learning about solar charged systems myself (so this is on the top of my mind right now).

I would be curious and interested in other people's experience with solar charged systems (I'm certainly no expert and woud like to hear various opinions). Lets reply to THIS thread though for posts concerning this subject so we don't cloud Eric's forums with off-topic posts!

 

[BraveSirRobbin]

EL34's Reply From Another Topic:
I am gonna be using a solar charge controller which handles all the charging and and monitors the loads.
I ordered a small 10 amp model, should be here next week.

They will cut off the load at a certain voltage so the batteries do not get damaged.
They also control the charging and will go into trickle charge mode to keep from over charging.
Some charge controllers can read the battery temps with a sensor and set the charging accordingly so you don't over cook them.

Here's some info on charge controllers, pretty cool devices.
http://www.morningstarcorp.com/products/Su...S_DataSheet.pdf


I am more interested in collecting battery voltages and voltages coming off the solar panel in relation to sun strength.
I have one of the HB solar sensors.

I'll have all the data collected from my one wire sensors on real time graphs, just for my own entertainment and to see the relation between the sun strength and voltage output at different times of the year.