Jobsite trailer

To give you a little description of my work, I build custom homes in old established neighbourhoods. The project would consist of demolishing a single family detached home and erecting a two story home. From demolishing, to the roof and until exterior cladding, the jobsite will without power. I have used the neighbours power which has bee satisfactory except for the occasional tripping of the fuse I've looked into the local power company providing temporary power, but that costs roughly $2000 per house. So, I looked into solar power and found that it is doable to provide power to the site using a 3kW modified sine inverter running off of the trucks batteries. Since, I leave my enclosed trailer onsite, I thought about placing solar panels onto the roof, and the remaining system, (control charger, battery bank and inverter) inside the trailer. However, I don't know how many or size of the panels and batteries. The majority of the power will be circular saws, miter saw, table saw and charging batteries. The air compressor will be gas powered. Technically, the most power used is during the framing. Now I would like to add a small fridge and microwave to the list, but those items are not required. Especially, if they require me to raise the cost of the system.

Thanks for taking the time to read this and respond.


  • BB.BB. Super Moderators, Administrators Posts: 28,309 admin
    Welcome to the forum Nomad.

    When designing solar power--We really need to start with how much power you need. In general, solar power is not cheap and a relatively large solar array to provide more than a "minimal" amount of electrical energy.

    For example, say you can fit 4 of these
    Pmax: 315 Watts
    Voc: 45.6 Volts
    Vmp: 36.5 Volts
    Isc: 9.35 Amps
    Imp: 8.71 Amps

    Weight: 49.6 Pounds
    Dimensions: 78.15" x 38.98" x 1.81"

    In a reasonably sunny climate, you can get a minimum of 4 hours of sun for ~9 months a year. Such a system would generate around:
    • 4x 315 Watt panels * 0.52 typical system eff * 4.0 hours of sun per day = 2,621 WH per day = 2.6 kWH per day
    And a reasonably large enough battery bank to run this load would be:
    • 2,621 WH per day * 1/0.85 inverter eff * 2 days of storage * 1/0.50 maximum discharge * 1/24 volt battery bank = 514 AH @ 24 volt battery bank
    Or roughly 12x 6 volt @ 200 AH "golf cart" batteries... And the maximum size recommended AC inverter would be around 2.5 kWatts.

    My guess is that you would use a genset during "intensive" construction--And could use such a solar system for charging tools/cell phones/running LED work lights. You could run a single Skil saw.

    Only you can decide if this is worth the effort for you... My guess is that, if you can borrow power from the neighbors, you are better off doing that (or even charging the owner $2,000 for temporary utility power (the home will need service eventually anyway--So some of the fees may only be delayed, not avoided by the owner).

    There is, at least, one alternative for the "blowing breaker" problem with borrowed power. There are some AC inverters that have a "Generator Support" mode. Basically, you can program the inverter to never pull more than (for example) 12 amps @ 120 VAC from the AC mains (or AC generator) and if more power is pulled--The AC inverter uses the DC Battery Bank to supply additional 120 VAC energy (there are 240 VAC versions too) when needed. The AC inverter also has an integrated battery charger--So you would not even need a solar array--To keep the battery bank charged.

    With a generator support system--You could get away with a smaller battery bank (or even Lithium batteries--lighter/smaller) too.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • oil pan 4oil pan 4 Solar Expert Posts: 759 ✭✭✭✭

    Use all energy sources.

    Get some solar, have a generator, heck even add a battery charger that can be ran off a neighbors 15amp 120 volt line.

    Its good to have more than one plan for power.

    Are you sure you need a gasoline powered air compressor?

    My 5hp gasoline fuelled air compressor is grossly overkill for almost everything. I only need my gasoline fuelled air compressor for running plasma cutter and/or sand blaster at a remote site.

    My smallest 1hp air compressor with a 5 gallon tank can easily keep up with my roofing nailer as fast as I can set the gun and shoot nails into pre laid out shingles. I also turn the pressure down to close to the minimum required to drive the nail flush, this saves air and saves wear and tear on the gun.

    Sounds like you need a bigger version of what I built:

    I built it for building projects, backup power, camping, powering work lights just a little of everything.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • Dave AngeliniDave Angelini Solar Expert Posts: 4,196 ✭✭✭✭✭
    Awesome articles in Home Power on this 2 issues back. You can subscribe for 12$
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
    E-mail [email protected]

  • bill von novakbill von novak Solar Expert Posts: 822 ✭✭✭✭
     I have used the neighbours power which has bee satisfactory except for the occasional tripping of the fuse.
    My recommendation - start with an inverter that will do generator support and a small battery bank.  This will allow you to plug into a neighbor's house, set the input current limit to 10 amps (or some other reasonable current) and never blow the breaker.  When the load exceeds 10 amps the inverter will draw from the battery; when the load is under 10 amps the inverter will use the excess to charge the battery.

    Next step is to add a generator.  Again a small generator will be sufficient because of the above generator-support function.

    Next step would be to add solar + charge controller if the above isn't enough.  That's expensive and less useful, so I would only do it if it gives you some other benefit (like "green cred" to use as a selling point with customers or something.)
  • BB.BB. Super Moderators, Administrators Posts: 28,309 admin
    This is a post from July--And the poster has not been back.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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