Seattle got slammed - want recommendation on solar systems

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tom baker

tom baker

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Master Electrician
Seattle area made national news last Friday, big windstorm knocked out power to a million homes

I have some remote sites for monitoring water tanks, I want put in a photovoltaic (solar) system maintain radio communcations for 5 days w/o power.
Equipment is 24 volt, 0.5 amp. Radio is only 2 watts.
What systems should I be looking at? I want a package- panels, charge convertor and batteries.
 
tom baker said:
Seattle area made national news last Friday, big windstorm knocked out power to a million homes

I have some remote sites for monitoring water tanks, I want put in a photovoltaic (solar) system maintain radio communcations for 5 days w/o power.
Equipment is 24 volt, 0.5 amp. Radio is only 2 watts.
What systems should I be looking at? I want a package- panels, charge convertor and batteries.
Click to expand...

Why not simply buy some large marine batteries and but 2 in series as well as a charger.With a small load that might be enough.Photo cells put out very little and would take many to meet any load.
 
Jim W in Tampa said:
Why not simply buy some large marine batteries and but 2 in series as well as a charger.With a small load that might be enough.
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Let's see...

Five days is (5 x 24) 120 hours. Providing 1/2 amp for five days requires (0.5 x 120) 60 amp-hours.

Yep. A pair of 75-ah deep-cycle marine batteries would be an economical standby supply ($50-60 ea @ Costco).

You could add a low-capacity solar panel if you want to, but the math bears out not needing one.
 
Tom
Not only is the battery idea a good one, but something else to think about.

If the wind storm knocked out power, might it not knock out the solar panels?
How about those batteries or a small generator.

Also does not the Seattle area receive a relatively low amount of sunlight, compared to other parts of the country?
 
Correct me if I'm wrong, but solar panels only need daylight present to be producing power.

From ealier research Seattle area has fair daylight -

--------------------------------------------------------------------------------

Bremerton WA - Dec 21, 7:56 AM 4:22 PM 8 hrs and 26 mins of daylight
Bremerton WA - April 21, 6:11 AM 8:09 PM 13hrs and 58 mins of daylight

Is 1/3 of the day enough to keep the system fully charged vs the cost of enough panel(s) vs having a trickle charger doing it's job?

Curiosity is killing the cat.
 
Yes correct a pair of batteries would work, but I don't think you can get 75 AH out of a 75 AH battery. This location has good southern exposure with no trees.
 
tom baker said:
Yes correct a pair of batteries would work, but I don't think you can get 75 AH out of a 75 AH battery. This location has good southern exposure with no trees.
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You're mostly correct -- you cannot get 75AH out of a 75AH battery except under the conditions the 75AH capacity is specified for. One of which is "when new" (batteries lose capacity with time), and another of which is operating temperature (when warm enough, but not too hot). The demand is low enough that the discharge rate shouldn't adversely affect real-world capacity (the higher the load, the lower the actual capacity will be).
 
Found a page with photos of something like what you're describing at
http://www1.eere.energy.gov/solar/yellow_pages.html

The same site may have other items of interest at
http://www.eere.energy.gov/states/state_specific_information.cfm/state=WA

Information on many currently installed systems (Resource, Commercial bars) at
http://www.solarelectricpower.org/

I hesitate to recommend anything. Remember solar hot water? Frankly, what I'd do is contact a local highway call box operator or the park service to find a known quantity.
 
I know that many gate operators have solar systems on them. They are both 12V and 24V, and are available as an accessory option to backup most hardwired gate operators. That seems like a reasonable "out of the box" solution to me.
 
Just did a job where there was solar panels, when I was there last week it was over cast, wind ,and rain, the unit was charging 275watts in the worst of it. when it was just overcast no rain 440 watts. Needless to say it was more then I expected to see.
 
tom baker said:
Yes correct a pair of batteries would work, but I don't think you can get 75 AH out of a 75 AH battery.
Click to expand...
Typically, the reserve capacity is stated at a 20-hour rate, and is where the battery reaches 10.5 volts. The trickle current load should actually extend the AH time.

Plus, the 4-day time implied worst-case, and the 75 AH is 125% of my calculated 60 AH requirement. If that's not enough, parallel-series four of them.

It's still gotta be cheaper than a solar array and associated wiring.

acrwc10 said:
Just did a job where there was solar panels, when I was there last week it was over cast, wind ,and rain, the unit was charging 275watts in the worst of it. when it was just overcast no rain 440 watts. Needless to say it was more then I expected to see.
Click to expand...
Now let's price the array.:wink:
 
Another option would be a hydrogen fuel cell....May be less than the solar system. Could always have deep cycle batteries on standby in town, and take out to the site, if not snowed in...
Our public emergency dispatch lost their generator at main radio site, and their Nextel radios were not working.
 
acrwc10 said:
Just did a job where there was solar panels, when I was there last week it was over cast, wind ,and rain, the unit was charging 275watts in the worst of it. when it was just overcast no rain 440 watts. Needless to say it was more then I expected to see.
Click to expand...

While that can happen its price tag puts you into thousands and you still need batteries.Put what ever number it takes in parallel and series.Even if that comes to 10 its gotta be cheaper.Now if this is a government job then sure why not.If it was practical every homeowner would be doing this to cut there electric bill down some.Show me something cost effective per kw and i will buy it.If this thing had to run forever and no power within 5 miles then it would be worth it.
 
LarryFine said:
Typically, the reserve capacity is stated at a 20-hour rate, and is where the battery reaches 10.5 volts.
Click to expand...
That would be 8-hour rate @ 77 degrees to 1.75 VDC per cell. You have to check the specific manufacture discharge curves at the specific discharge rate and tempurture curve of interest to get a calculation, but it is only a calculation. Any VLRA battery looses about 5 to 10% of its capacity per year under ideal conditions, vs a flooded type which can still have up to 80% capacity after 50 years.

Tom at .5-amps draw on a 60-amp hour battery you are looking at around 5-to-6 days of reserve time. More than enough time to get a portable genset to the site and run periodocally to top off the batter charge. One thing you have to look at is the devices voltage operating range to determine if it can even operate on batteries. The range on a 12 VDC system is 10.5 to 14.5, 24 VDC 21 to 29, and 48 VDC 42 to 58. If the equipment cannot handle the range, it is not compatible.

Also keep in mind as the battery voltage starts to decay (as soon as the rectifier turns off), the load current increases because the load device requires a constant power, and as the voltage decreases, the load current goes up.
 
The cost of most solar systems is way to high to make sence for a home owner. The technology in the solar panel is about to take a huge leap that should make them more cost effective but until that happens I'll wait. The last system I saw was 50k with a 20k rebate from the poco.After rebates it is still a minimum 15 year payback on the investment. As far as Toms question in a remote area my consern would be theft of the solar panel. It has been a problem for road side call boxes , although if the site is secure this may not be a problem. Jim is right you will need batterys no matter which system you choose, a small charger would be MUCH more cost effective, but if the customer is green in the brain they may think it is worth the money.
 
I would use a marine battery and trickle charge it from a small solar panel. A voltage regulator or a power supply would take care of any problems with the supply voltage.

I would do an internet search for companies that make roadside signs. I often see roadside signs that are solar powered. I bet they have a package that could easily be modified or applied to your radio.

Steve
 
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