Thursday, January 10, 2013

DIY Solar Energy (Part 1)

Note: (Part 2) is now available.

      Living off-grid gives you new perspectives on everything. For one, you become super aware of all nature's elements and how they affect you. This may be in terms of their warmth or chill, light or darkness, comfort or torment. For Heidi and me, the element we notice most often is the sun. There is almost nothing more satisfying than seeing the sun break through heavy winter clouds which warms our southern facing windows and watching our battery monitor as it climbs to full.
       Solar power was something I knew nothing about when we first decided to build our bus. We realized that we would need some sort of power source when the bus was parked, but we didn't want to restrict ourselves by the necessity of grid power whenever we weren't driving, nor did we want to rely on a noisy, polluting gas generator. I had stumbled upon a few websites and forums about people who had retrofitted there RVs to run on solar. As I dug deeper, I found that there is loads of information out there as long as you know what you're looking for. I decided to give solar power design and installation a try and the results have been awesome!
          My aim now is to create an organized resource for others who are interested in creating a similar system or just curious about solar power. In the following two posts I will review the basic design, parts and process of creating your own small-scale solar electric system. By small scale, I am talking about applications such as a small cabin, RV, boat or a very small and efficient home. I will also provide helpful links that I wished were all organized in one place when I started my project.

 IMPORTANT DISCLAIMER: Working with electricity and batteries can be dangerous! The purpose of this post for basic information only. I am not an electrician and I do not recommend that anyone attempt any of the following without a professional's opinion. Always refer to your local laws and building codes. Please see Terms of Use.

Ok, now that we got that out of the way. Lets get started! There are four basic components to any solar charging system.

1. Solar panels (aka photovoltaic panels) which collect an electrical charge from the sun.
2. Batteries to store the charge from the solar panels.
3. A Charge Controller that safely and effectively regulates the charge from the panel(s) to the batteries.
4. The Wiring which connects all of these components together.

We will get to all of these, but you need to begin with this important question:

How much power do I need?

This is the first question that needs to be answered in planing any solar setup. On the most basic level, the more energy you use the bigger the system you need to design. Other important factors include weather (i.e. how much sun do you get on average?), shading (do trees, houses, or mountains shade your location at certain times of day?) latitude (how many daylight hours do you receive at various points throughout the year?) and direction (how much southern exposure do you have).

The most cost effective way to "go solar" is to minimize your energy consumption first. Before you even consider solar power, first consider the ways you can become more efficient. Can you use LED lights? Are some DC appliances an option? You can create AC power (like most home appliance use) with solar power but is often much less efficient then using the DC current which solar panels generate. Most importantly, ask yourself do I really need that TV, toaster and/or iron? For us, going off grid has meant scaling way back on our energy needs, and shouldn't that be the idea anyway? Consider everything and then size your system for your requirements.

Our 12v LEDs provide plenty of warm light using only 10% of the energy of an incandescent bulb
 and 45% of a compact florescent. The do not contain mercury and are rated to last over 20 years!
By having each light on its own individual switch, we only use as many lights we need. is a great place to find specialty LED lights and accessories.    

First calculate how much power you use. Utilize an online power calculator to figure out just how much energy you will need to generate. I would recommend using one that also calculates the size of the solar panel or panel array (group of panels) that will be required for your system. So far I have not found the perfect calculator. Some are easy to use but very inaccurate. Others are incomplete or have have some major glitches. The most accurate one I could find is the The Solar Sizing Calculator from To use the tools on this site you are required to become a free member by entering your email (you can easily unsubscribe from there mailing list later). Next, you will need to gather the wattage (or DC amp) ratings from the labels on all of your appliances or refer to this chart. You can also look up many of your appliance online by searching (your appliance name and model) + specs. If these numbers already are making your head spin, click here for a simple explanation of amps, volts and watts.

Now, enter the appliance info into the calculator along with an estimate of how many hours you will use the appliance each day. You can enter watts, DC amps, and whole or partial hours (i.e. .25 hrs = 15mins). Remember that if you are using 2 of the same appliances at once (such as lights) you will need to either double the amount of energy for that appliance's category. The calculator will tell you how many amps hours you use per day. Next it will ask you for your "Solar insulation" value which is basically the average sun exposure at your location. To find this, you can use a map on the side bar or follow their link to the NASA website for more exact information. Remember to choose the solar insulation value from the month with the smallest value in which you will be using your system. There are short tutorial videos to help you through these processes on the solar-panelbatterycharger site.

Here is what the calculator looked like for our bus needs on a high energy use day:

You will notice that our total amp hours are pretty low by most standards, but our panel size suggestion is quite large for a these requirements. That is because we in a northern latitude (almost at the Canadian border) which means less direct sunlight. Also, our area is very cloudy most of the winter. So in the middle of December we need every bit of panel to keep our batteries charged. This is why you should use data from your area's least sunny month. If we lived somewhere like southern California, for example, we could get all the energy we need from a quarter of the panel size even in December.

Another thing worth noting is that the power ratings given on appliance labels are their maximum output ratings. In reality most appliances use significantly less power then this. If you really want to know the actual power use you can buy an inexpensive watt meter like the Kill-A-Watt. I personally find it is better to be conservative and use the maximum rating since you want to size your system slightly larger then your needs anyway.

The Go Power Calculator is a different calculator that is much simpler and fairly accurate, but it would not calculate the appliances that I added in myself. Also the solar insulation maps were not accurate for my area. Maybe it will work better for you. If anyone knows a better online calculator please post a link in the comments section.

That should be enough to get you started. Once you know what size system you are looking for then you can start looking for parts. Next week. I will discuss different options for panels, batteries, charge controllers and wire sizing. I will also share some of my own experiences and mistakes so that you may avoid them. If you liked this post, you can subscribe to this blog so you don't miss the next one. Good luck!

EDIT: DIY Solar Energy (Part 2)  has now been posted!

Clipart of a decorative sun, Click here to get more Free Clipart at

As I mentioned before, I am not am not a solar power expert or professional, but I will try to answer any basic questions left in comments to the best of my ability.

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bro said...

What kind of batteries and charge controller did you use?

Colin D said...

Hey bro, we use two Trojan t-105 batteries and Blue Sky Energy's Solar Boost 3024i for a charge controller. I will talk about these components in detail on next week's post (part 2).

Lisa Lynn said...

This is an awesome post! Gotta share :) Thanks for linking to The HomeAcre Hop!!!

Annie @ MontanaSolarCreations said...

What an awesome post! The solar panels on our house are not off grid but we do have a solar panel on our old slide in truck camper. I'm always amazed at how much energy it stores up. We use it quite often for cool weather and winter camping since we have a heater hooked up that it powers. Do you get a decent amount of sun throughout the winter? Where we are outside Missoula it is still quite gray because of inversion but amazingly our solar panels still generate some power on those days!

Wild Blue said...

Thanks Annie! Yeah, we do alright in the winter even though there are stretches (like right now) where the sun barely shows its face in three weeks or more. Last winter we were struggling with 250w of panels so we added another 200w. Even on overcast days we can usually get back the power we used the night before. The key is finding a place to park that gets decent southern exposure and to angle the panels toward the sun, which can increase efficiency up to 40%! I will talk more about this in my next post.

Jami at 2 Cool 4 Skoolie said...

Thanks for sharing everything you've learned! Your research will help us so much when we finally convert over our skoolie. Even if we aren't living off grid, it will still be helpful to not have to be hooked in.

Troy Ault said...

Hey Col -

Took a course at Berkeley in renewable energy and the insolation tables/maps they recommended using were from the Department of Energy's "National Renewable Energy Lab", or NREL. One would think NASA and NREL would share data or coordinate efforts... Here are the links:
(can select state-specific tables at the above)

Wild Blue said...

Hi Troy! Thanks for the links. There is loads of information in these documents. I found data a little more difficult to interpret than the NASA site, but lots of good info none the less.

eliwhitney said...

I found the GIS data he posted quite helpful.

The second set listed, PV power by month, shows it month by month, so you can create baseline winter and summer loadouts.

Unknown said...

WOW Good

Unknown said...

Yes! We are looking to do this for our rig in the near future as we will be without electricity until we get a building permit for our house. Thank you so much for the information!!

Mr. R. said...

Thanks for posting your progress through all of this! It's a great inspiration.
Just so you know the solar sizing calculator link is dead.