Building a Solar Generator ( First Time )

ehazell94 · February 2014

I would like to build a Solar Generator I see a lot of people have been doing so, and companies are now advertising Solar Generators for outrageous prices online at places such as Amazon, and Google.

So what I would like to do is build a portable (In a sense) solar generator,
I am trying to have the following functions from the generator;
Have a maximum power output of 1000 Watts
Be able to supply that power of 1000 watts for at least 1 hour (In the circumstance of cooking something)

My Main concerns for the generator would be powering my TV (300 Watts) my WiiU (40Watts) perhaps the ability to charge 1 -> 2 cell phones. I'd like the ability to be able to run at least 500 Watts of constant power for at least.

As for portability it seems now a days people are building solar generators that are simply mobile based upon there being wheels attached to the battery case that allows them to sort of cart their generator around, This would also prove useful as the handle could be used as an attachment point for the Solar panel(s).

So please if you could provide any or all information, what would it take to get a generator like this built? One that could supply 500 watts for up to 2 - 4 or 8 hours of constant use and or also supply 1000 watts for at least 1 hour of constant use.

I appreciate you taking the time to read and respond to this thread thank you for any and all information!

Cariboocoot · February 2014

Re: Building a Solar Generator ( First Time )

Just because it bugs me I'm going to say the term "solar generator" is inaccurate and should not be used.

What you're looking at is a small, battery-based back-up system with solar panels to recharge it. This is not difficult to do, especially as you have already described the power need as 1 kW hour AC. Being able to supply 500 Watts continuous for 2 hours isn't impossible either. But if you think it's going to be small or cheap, guess again.

The basic math:

1000 Watt hours AC is about 1176 Watt hours DC. Call it 1200. Divide by 12 Volts nominal system Voltage and you get 100 Amp hours. But the battery shouldn't go below 50% SOC, so your minimum battery bank is 200 Amp hours @ 12 Volts.

Enter the good ol' GC2's: cheapest stored Watt hours you can get, and at 220 Amp hours just right for the job. Recharging them from 50% DOD on the other hand ends up being pretty big in the panel department. For one thing the 10% rule-of-thumb usually won't work here, so you need "maximum panel" capacity (i.e. 20% peak charge current).

That means supply 44 Amps @ 12 Volts, or 770 Watts of panel on a PWM charge controller. This is no longer small, as that much panel will take up approximately 50 square feet of space. Ouch.

So where do you want to compromise? Less stored capacity by limiting the discharge to 25%? That cuts down on the supplied power available. Larger battery at lower charge rate? Array ends up just as big.

Now I know what you're going to say: "Other people have done it, and there are commercial units available." Two things; other people have done it and made the necessary adaptations so that they work, and the commercial units are too often too small in battery and/or panel to be of any practical use (as well as expensive).

For occasional back-up power generators are much cheaper. If you want to experiment with solar and see what it can do, then go with the two GC2's and 'standard' amount of panel (around 385 Watts, or three 130 Watt panels in parallel on a 30 Amp PWM controller) and recognize that the stored power may not be so easily replaced.

hemmjo · February 2014

Re: Building a Solar Generator ( First Time )

A local company used to advertize those units around here as the save all solution. They would allow you to save on utility bills, run your whole home during power outages, stay warm, cook, run urgent medical equipment etc. No need for fuel, no danger of carbon dioxide, everyone should run out and buy one. They would even work on cloudy days.

As with most products that are advertized and sound too good to be true, the claims are outrageous. That company is no longer in business either.

If you really want an emergency power supply to recharge a computer or cellphone or something, a small portable solar system might be in order. But if you need to cook, for less than 50 dollars, you can get a small propane camp stove and a 4 pack or propane cans. You can store them forever and use them at a moments notice.

If you really need TV to feel connected to the world make sure you get one that can receive over the air broadcast as if there is a major storm, your cable will probably be out also.

Just my thoughts,

John

BB. · February 2014

Re: Building a Solar Generator ( First Time )

If you can "live" with 2x 6 volt ~220 AH "golf cart" batteries. That would be a great place to start.

Here are some "smaller" off grid power options:

BB. wrote: »

Add this link to our Solar Beginner Post:

Emergency Power

Basically a very long thread that starts from the beginning with a few vague requirements through design and assembly for a "portable" solar RE off-grid power box.

And here is another example by Mike90045 called the Solar Monolith:

Update pictures/information here.

-Bill

-Bill

Building a Solar Generator ( First Time )

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