Small Solar Power system

[riptides]

I'd like a complete "small" solar power system to provide ample juice for two lights (manual control), a motion detector light and a heater in a water trough.

The system will be mounted on a roof and all components except the wiring and panels will be housed out of the weather.

My issue seems to be that of watts. I think the heater is the issue, because it draws so much. At this point, I don't need it full time and would probably opt for a day on battery backup.

Recommendations or advise, welcome. Thanks!

 

[newbury]

C'mon - you know better -
Give us some specs
Where? Northern Virginia? Alaska" Hawaii?
To what temp? just above freezing?
What size is the trough and will it be insulated?
Can we assume LED lights or do you want the lights to provide heat?
Will the batteries be mounted on the roof?

 

[John_Mc]

The lights are easy, especially if you use LEDs to minimize the draw. Is the motion detector light for you, or for whatever is using the trough? If it's for you, figuring out how to keep what is using the trough from triggering it will minimize battery drain. What size heater are you thinking of running? That could easily turn your "small" solar system into a larger one.

I assume the heater in the trough is just for freeze protection. Anything you can do to insulate your trough to slow heat loss will help cut down on the size of the system you need (a bucket or tank lends itself better to insulating than a shallow open trough).

If you have a day on battery backup, is 3 days without sun going to cause problems for whatever is using the water trough, or do you have other means of dealing with that?

It's hard to size the system with all of the variable (including how much sun you get in your area - I'm aware of calculators which will give you average annual solar estimates for your area - PVWatts is one. However, "average annual" won't help you, since wintertime output is much less than average. I but don't know if those resources will show seasonal solar expectations - it's been several years since I've used it.)

 

[riptides]

Northern Virginia. Climate, Jan-Mar (20 degrees to 50, average).

Inside LEDs (manual switch only) no more than 40 watts.

Outside LED (flood light, motion detector) no more than 90 watts.

Water trough (deep tank) looks to be no more than 1500 watts.

Panels on top, all components including batteries on inside. Probably right under panels. No more than 3 feet distance.

I have other means of getting water to area, if needed. So a day or so on battery backup is fine.

 

[Diggin It]

The trough heater is the issue. How big? How much surface area? How much Sun do you normally get? How much loss is there due to shade from trees, buildings, terrain, etc.?

There are solar pool heaters that lay out on the ground and circulate the water through them via a small pump. If you get enough Sun and temperatures don't too bitter cold, that may be an option.

 

[Diggin It]

Inside LEDs (manual switch only) no more than 40 watts.

Outside LED (flood light, motion detector) no more than 90 watts.

Those don't need to be anywhere near that. Outside LED floods can be 10 watts unless you want to light a huge area.

 

[riptides]

The water trough sits in the sun for 3/4 of the day. 4 foot surface area to it. Depth is at least feet. Heater is at the bottom, will look into solar pool heater with pump. Good idea.

 

[Jchonline]

As you can see there is a great deal of detail needed to make solar work. You need to figure out how much power you will draw (max power) in a 24h period. Then you back this into a battery and solar system to support it based on your location. Take the heater out of the equation and it will be much easier.

 

[riptides]

Those don't need to be anywhere near that. Outside LED floods can be 10 watts unless you want to light a huge area.

Ok. TIA. Fairly large area (need to see what we are walking into), can experiment with lighting watts, not a problem.

 

[Deerherd]

Instead of a heater, get a large aquarium/small pond bubbler that will draw no more than 15-25 watts.

 

[riptides]

Instead of a heater, get a large aquarium/small pond bubbler that will draw no more than 15-25 watts.

Wow. Yeah I have all sorts of koi/aquarium/water pumps around. No where near the wattage of the heater. Will have to see how horses react to - bubbly water. LOL.

For the outside lights, heck for 50 bucks I can get self contained solar units. I might try that route in the meantime while I figure this out.

 

[Diggin It]

For the outside lights, heck for 50 bucks I can get self contained solar units. I might try that route in the meantime while I figure this out.

Or less:

 

[John_Mc]

I wonder if you might be better off going with solar hot water, rather than electrically heating your water. I have a couple of 4'x8' panels that act as a preheater for my domestic hot water tank. The antifreeze is circulated through them by a solar powered pump run by a small solar panel (roughly 12' x 16" panel, no batteries, the pump runs whenever the sun shines). The panel also powers the control system that decides whether the pump runs or not (it won't run if the solar collector temp is below my holding tank temp, or if my holding tank is at it's max safe temperature).

My system is overkill for what you need (even one of my panels is probably overkill), but something similar in your setup probably makes more sense than trying to heat the water electrically. There would be no battery backup, but you'd be able to keep your water thawed even on moderately sunny days where there is not enough electric power to run your 1500 watt heater.

Your system would consist of some sort of solar thermal collector, a small pump and PV panel, control system (so pump doesn't run when collector is colder than your tank, or when tank is already at your max desired temp), plumbing, and a heat exchanger that you drop into your tank (since you should probably run antifreeze in your heat exchanger, you may want a double walled heat exchanger to provide extra isolation of the antifreeze from your water).

Couple that with the self contained solar lights you linked, and you might be in pretty good shape.

 

[MossRoad]

The trough heater is the issue. How big? How much surface area? How much Sun do you normally get? How much loss is there due to shade from trees, buildings, terrain, etc.?

There are solar pool heaters that lay out on the ground and circulate the water through them via a small pump. If you get enough Sun and temperatures don't too bitter cold, that may be an option.

A solar pool heater, left with water in it on a freezing night, can burst pretty quick. So can any pool pump or filter.

 

[Travelover]

I'd agree that the way to get solar heat is to directly capture the heat from the sun. In a place where it freezes, you need a system that has separate antifreeze to capture the heat, then a copper coil in the trough to transfer the heat, with a tiny pump to circulate the working fluid. Just a couple gallon can painted black would suffice as a solar collector. Insulate the trough, too, of course.

 

[RoyKing]

How about solenoid valve and a freeze alarm , turn on the water and let it run. Much less complicated

 

[John_Mc]

From my friend, who is a renewable energy guru (used to run a Solar PV installation company using systems he custom-designed, formerly designed wood combustion systems and control systems for them):

Going with a solar water heater and enough thermal mass would definitely be the most cost effective solution. There was a batch of solar hot water panels being sold used from a large food processing facility in the past. They may be a good source for panels if your other friend doesn't want to make a panel.

If it were me ... I would insulate the stock tank and have a second, fully closed & insulated tank with a gravity feed to move water to the drinking tank as needed. The second tank would be the thermal mass to get through the one day storage you mentioned.

Alternatively, would a temperature triggered electric circulator and sufficient thermal mass be the low cost solution for a climate like VA?

BTW, making your own solar hot water panel is not at all difficult. A local friend made his own, which provides the majority of his domestic hot water here in Vermont. If you search solar hot water on YouTube, you'll find lots of DIY examples. You don't need a lot of capacity, since you are just looking for freeze protection, rather than hot water for a shower or similar use.

 

[Travelover]

These might be of use. Build a Solar Stock Tank - DIY - MOTHER EARTH NEWS

Solar heated and insulated stock tank

Suntanks: Freeze-proof Solar Heated Horse Waterers,Cow Water Tanks

Build a Solar Stock Tank - DIY | On The Farm | Pinterest | Livestock, Horses and Farm life

Solar Heated Stock Tanks - Shipping Nationwide!

https://www.amazon.com/Gallon-Suntank-Heated-Livestock-Manual/dp/B07261G4V2

https://www.builditsolar.com/Projects/WaterHeating/SteveTank/SteveTank.htm

 

[Industrial Toys]

Funny how the whole Solar Power consideration comes to a grinding hault when someone mentions "heat". Most solar installations for heat, are through circulating panels. I'm guessing the efficiancies are higher, than making electricity and heating water that way.

 

[riptides]

This experience is interesting. For lights it is a no brained to spend less than 100 dollars for decent flood light type bulbs. For indoor lighting about the same for a few bulbs. For a water heater. .... it is more complicated as now we need wattage and a good battery system. I will insulate the tank and run an extension cord as needed until I figure out a better low cost less hassle solution.