Uninteruptable Power Supply

[JNSMAR043]

Hi, I am designing an uninterpretable power supply for a piece of surveying equipment to monitor wind speeds in remote locations of the grid. So the bat monitor/Lidar uses a 28V DC at 210 W (maximum). The system is to be deployed anywhere in southern africa and already has 10x 105Ah 12V batteries but will require more. I have made a start and will update the thread I am just curious to see what ideas are out there.

[Mike90250]

Wow. That's going to be a pain. The size of the solar array required will surely affect the wind readings !! And attract unwanted attention.

Why is it such a power hog ? There are small, highly accurate weather stations that can go weeks on a couple small batteries, and log the data locally. But 5Kwh a day is way out of line. Does it have capacity to log data and just fire up a radio for 10 minutes to dump the recordings ?

To recharge the batteries, you will need a good amount of sunlight, and about 4KW of PV array. Less sun = larger PV array. What happens if the batteries go dead, will it still log data, or is all lost? Cloudy weather will impact battery charging, will a generator be an option ?

[Robert1234]

Remote locations "of the grid" (as written) or "off the grid"? OP's clarification would help tremendously. Either way, I agree that is a chunk of power. Wonder what the actual average amp/watt draw is?

[JNSMAR043]

Hey so here are some more details. I need to design a system that will supply power to a lidar surveying unit in remote locations that will definitely be off the grid.The uniut basically gets parked in a field and records data for a year at a time. The unit draws varying amounts of power based on the temperature, but does have the capacity to accept either ac or dc inputs but requires continous power (24hours a day)
Lidar Power requirements
Voltage(W) Power(W) Temperature °C Operating condition
Minimum 28V DC 100 0 to 25 Normal
28V DC 120 25 to 40 Hot
28V DC 210 -25 to 0 Cold
Maximum 28V DC 250 N/A Absolute Extreme.
AC input: 100-240V AC, 50/60 Hz, 300VA
The system is to be deployed in a region of South Africa where the temperature is only ever below 0 degrees for approximately 18 hours and above 25 for the same amount of time. The 3 options I have investigated are only solar, solar and wind, solar and generator. Any suggestions or warnings yet. Lowest solar insolation levels are 2.5 Kwh/m^2/day.

[Mike90250]

you are in a pickle. a 24v battery gets recharged with 29-31v, which is over your 28v limit.

you may have to go with a 24v (or maybe a 48v inverter if it makes the battery work out right) system If you are sure you have reliable wind, you could install dual wind turbines with dump loads, and visit weekly to make sure they are still spinning. And a Solar PV array, for when the wind isn't.
Site security - who is going to guard all this expensive gear ?

so, some answers before I calc all this out?

from Russ:

For wind also see http://www.solacity.com/SmallWindTruth.htm

If you don't have a tall tower - forget it
If you don't like to tinker - forget it

[SunEagle]

you are in a pickle. a 24v battery gets recharged with 29-31v, which is over your 28v limit.

you may have to go with a 24v (or maybe a 48v inverter if it makes the battery work out right) system If you are sure you have reliable wind, you could install dual wind turbines with dump loads, and visit weekly to make sure they are still spinning. And a Solar PV array, for when the wind isn't.
Site security - who is going to guard all this expensive gear ?

so, some answers before I calc all this out?

from Russ:

I think the minimum and maximum values the OP listed concerns the wattage with respect to the temperature.

Min = 100 watts @ 0 to 25C
Hot = 120 watts @ 25 to 40 C
Cold = 210 watts @ -25 to 0 C
Max = 250 watts @ N/A C

Those wattage's are calculated at 28VDC but he did not list the DC voltage range the equipment can work at.

[JNSMAR043]

The Lidar unit has its own built in batteries that charge of the input so the only DC value specified by the manufacturer is 28V DC which they suggest supplying through a DC DC converter.

Could two 12V batteries in series work.

The proposed site locations are very remote and the trailer housing the charge controller and other equipment will be properly secured. If the unit accepts DC and the batteries output DC then would the inverter be for the wind turbine output?

[Mike90250]

The Lidar unit has its own built in batteries that charge of the input so the only DC value specified by the manufacturer is 28V DC which they suggest supplying through a DC DC converter.

OK, so a wide range, 300w DC-DC brick converter can be had for about $300 Input 15-40VDC. That handles the charge voltage of the 30V the 24V batteries need.

Could two 12V batteries in series work.

yes but you get more capacity with 4, 6v200ah in series.

The proposed site locations are very remote and the trailer housing the charge controller and other equipment will be properly secured. If the unit accepts DC and the batteries output DC then would the inverter be for the wind turbine output?

So what is the budget ? What is the time frame? for a couple months, a $1000 generator with some stacked fuel cans or a propane adapter would be the ticket. Months in one spot, installing solar might work. We really haven't gotten enough feedback from you to come up with a good plan. If there is a trailer, there is a road, and a road is not "remote" enough to provide security. Here in California, road construction sign trailers were getting stolen off the highways, till the department started removing the wheels off the trailers so they could not be towed. Out in the boonies, there is nobody to hear a saws-all gutting a lock.