Pv system for existing lights.

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bth0mas20

Senior Member
Location
Maryland
Im new to solar work and would like to bid a job.
Requires installing a pv system to power 4 existing lights on a metal building. These lights are 150 watts each.

Im looking for any help or suggestions. Im not really sure how this will be set up to work. The rest of the building will just be powered from the existing power.
 
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BillK-AZ

Senior Member
Location
Mesa Arizona
Efficiency comes first

Efficiency comes first

You need to first make sure that the solar powered devices (lights in this case) have the lowest possible power requirement to provide the required benefit, light output in this case.

Recent advances in LED lighting may apply. Sounds like you need to replace 150-watt fixtures that use high pressure sodium lamps. With ballast, these fixtures require over 200 watts.

My city has recently replaced such fixtures with LED fixtures that draw less power and provide more light. Very impressive.

LED lamps are more efficient because of three factors. LEDs now provide more lumens per watt at the lamp, the light is directed in one direction so less is lost within the fixture, and the ballasts are more efficient.

Determine the light level needed, find the LED fixture with the lowest power that will meet the lighting need, design the PV system to meet the power requirements.

It makes no sense to provide a larger PV system to power existing light fixtures.
 
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dbuckley

Senior Member
Location
Canterbury, New Zealand
BillK-AZ said:
It makes no sense to provide a larger PV system to power existing light fixtures.
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Absolutely.

And you would need a fair size system to make four 150W lamps work all night, especially in terms of batteries.

Is there some reason why just these lights need to be solar powered? And do they actually have to be solar powered?? By which I mean do the PVs have to charge batteries to run the lights, or can you use PVs to backfeed the grid during the day, and use the grid overnight. Thus using the grid as a battery. Ok, so the lights aren't using the actual electrons the PVs generated, but, you can offset power used against power generated.
 
tallgirl

tallgirl

Senior Member
Location
Glendale, WI
Occupation
Controls Systems firmware engineer
Calculate the maximum average daily load. That's the average ... of whenever the lights run the most. Which is prolly December or January, but could be another month for some weird reason.

Divide that by 0.77, which is the NREL standard derating factor to go from AC KWh to DC KWh.

Go to the NREL insolation tables for you location. Find the MINIMUM daily average insolation. Don't use the "average" and certainly don't use the maximum.

Divide DC KWh by the minimum daily average insolation. That's your array size.

Sizing the battery is an entirely different matter, but I've scribbled enough for now.
 
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