Office Trailer / Portable Unit - Brand Newbie looking for recommendations

[evelopez]

Hello! Brand newbie who purchased a 20 x 8 one room pre-fab portable structure which will be housed in my backyard until able to return working at an office, at which time I intend to sell the unit. To avoid the cost of having electricity brought to the unit and to try to increase salability, is it feasible for it to be solar powered?

The pre-fab unit has some lighting (spec sheet attached) and in addition to the lighting, power would be needed for a computer workstation, internet, internet based phone and perhaps a desk lamp. I have called a couple of solar companies near me (Los Angeles area) but they have all said that they do not work on these types of structures,. suggesting to look at a solar panel kit. Any suggestions? I have read a bit about the kits but the truth of the matter is that I don't know enough to know what to ask or to look for. If I am unable to locate a professional to help with these decisions and installation, any suggestions for a DIY kit for a brand newbie? Basically, I'd need one that is dummy proof.

Any help to steer me in the right direction would be greatly appreciated!

Thank you.

Eve Lopez Trailer front view (croppoed).pngTrailer Specs.pdf Inside view.png

[bob-n]

Eve,

Welcome to the forum. You have a nice project in mind. I hope it works out well.

You can put solar panels on the roof of the trailer. But that's not all you'd need. To be completely off grid, you also need batteries and electronics. Of the three, batteries are the most expensive part, and also the part with the shortest life. Because of this, many people start down this path and then abandon the batteries and just run a power cord.

As you plan this project, there's a few things you need to calculate and consider. The first is how much energy you need in a particular day. Energy is measured in watt-hours. For example, if your computer uses 100 watts continuously and will be on for 8 hours a day, that alone needs 800 watt-hours. Lights are easy. Each bulb is labeled with watts. Modern LED bulbs are roughly 10 watts each. My internet modem uses around 15 watts and my router uses another 20 watts. Add it all up. Let's assume it comes out 1500 watt-hours per day.

If you always have lots of sun, you could put 1500 watts of solar panels on the roof of the trailer and get by with a small battery. But life is never so simple. The sun is low in the winter so you won't get much in the winter months. There are rainy days, even in southern California. So you need enough battery storage capacity to get you through this with lots of energy to spare.

You need to calculate how long you will be without strong sun. Is it one full day? A week? Or a full season? As you can imagine, that means a huge difference in the size of batteries you need. Battery costs vary wildly, but as a rough estimate, figure $0.30 per watt-hour of usage. In other words, if you need to run one full day of 1500 watt-hours on batteries, that's roughly $450 worth of batteries. If five days without sun, you need 5X that much battery. Please don't quote me on this, it's just a round number for estimating. I'm not sure how long batteries will last for you, but as a rough estimate, they seem to be good for 5 years if not deeply discharged and well maintained.

Next, you need to assess the amount of solar panels. Solar panels are roughly 400 watts each and roughly 1m x 2m. You have room for 5-6 panels on top of the trailer, so have peak power available of 2000-2400 watts. In the summer, you might get that for perhaps 5 hours. In the winter, for perhaps 1 hour. So in the winter, if it's clear and dry, you can get 2000 watt-hours per day, and in the summer, much more. That's probably going to be OK unless you have to work through many consecutive days of gloomy weather. Solar panels cost roughly $300 each, so you're going to get roughly $1500 worth of panels. Again, this is a ballpark number, not a quote.

Finally, you also need a battery charger and inverter. I haven't priced these recently.

Now compare all of that with the cost of running a long extension cord.

Hopefully, others will also give some good advice, such as good books to read, how to calculate the exact amount of sun you'll get in a specific situation, etc.

I hope that this is helpful. It probably raises more questions, so please keep asking here.

[J.P.M.]

Your brand newbie part is showing. Skip the paid professionals.

For the time, toil and treasure involved in a project to get PV power to a place that could more easily be had with a couple of extension cords and be done with it for what may be a temporary structure, IMO only, you'll be money and hassle ahead by simply running power from the house.

I doubt a stand alone PV system could be accomplished for what it sounds (reads) like what you want to do for much less than maybe $3K-$5K, and you'd have a more than a part time job maintaining the system if it's proposed to be off grid.

Get educated about residential/small scale PV and you'll see what you have in mind entails. In the meantime, go to Big Box and get a couple of extension cords and see how that works out. If it does, that's when you hire a couple of professionals to run a couple of permanent lines from the house to the structure.

Better, cheaper, faster.

Welcome to the forum of few(er) illusions.

[bcroe]

Use an extension cord, have it professionally installed under ground if needed. Bruce Roe

[SunEagle]

The cost of powering that building using solar will be much more then just getting an electrician to run a grid connection to it.

Solar/battery system costs about $1500/kWh it can safely deliver. If you do the math even a small load of 5kWh will cost you over $5000.

[Sunking]

Running AC power is a lot less expensive to install and operate with no power limitations. Adding solar would only devalue the property. Only a sucker would buy it.