Simple Solar Project Part I

Renewable energy is key to being self sufficient on the homestead. Having an alternative source of energy, such as solar, makes you a little bit more self reliant. Despite the importance of this, many people are intimidated by this topic and never realize that quite often a simple solar project is easily within their reach.

In this video post, I demonstrate how I solved a particular problem with my green house.  The green house sits a 10,000 feet elevation and has been in place for about 3 years.  I assumed that my biggest problem would be keeping it warm enough. However, due to the intense mid-day sun at that elevation, my biggest problem is keeping it cool enough. I tried putting in roof vents, side vents, leaving the door open, and using small 12 volt fans to circulate air. But nothing was working the way I wanted it to. What I needed was a large electric fan to force hot air out through the roof vents. But in order to run a fan, I needed electricity. The utility lines are 1/2 mile away and my primary solar array is 300 yards away. See me demonstrate how I solved this problem with a simple solar project.

In this video, I demonstrate this simple solar project step by step. After watching the video, read the “Additional Project Details” to learn a little more.

Enjoy!

Additional Project Details

It occurred to me after making this video that it would be important to explain a few other things regarding this project. These details will give a lot of further information and help you to have a successful installation.  The good part is that this information is applicable to any solar project.

–Tilt angle of the solar panels:

First of all, solar panels are typically angled toward the equator for maximum sun exposure. This means is you live in the Northern Hemisphere, you face the solar panels toward the South. I you live in the Southern Hemisphere, you point the solar panels North. Additionally,   solar panels are either mounted at a set angle to the sun or they are mounted with an adjustable angle. Solar panels will produce more electricity if they have near 90 degree contact with the sun.

Because the Earth is not flat, the best angle varies according to your latitude.  Here is a simple calculation for determining your optimum tilt angle:

Add 15 degree to your latitude in the winter

Subtract 15 degrees to your latitude in the summer

For example, if your latitude if 35 degrees:

Winter angle: 35 + 15 + 50

Summer angle: 35 – 15 = 20

This calculation helps to compensate for the fact that the sun travels through the sky at different angles depending on the time of year.

-Connecting the solar panels:

For this particular project, I wired the solar panels in parallel. All of the positives were wired to one central connector and all the negatives were wired to another central connector. The end result was that I ended up with only one positive and one negative electrical output going to the charge controller. This is important because the overall voltage for the circuit stays the same. I still end up with a 12 volt output. This makes a difference because I have 12 volt batteries.

-Installing the DC loads box:-

This is important for several reasons. Any electrical system should have safety  or emergency cut off points. This allows you to isolate portions of the electrical system. If there is an emergency or you simply need to perform maintenance or replace equipment, you need to be able to isolate portions of the system to reduce the risk of electrical shock. Additionally, it protects your equipment from electrical surge such as a lightning strike.

Just because this is a small project, do not skip this important step.

-Choosing the charge controller:

When solar panels are connected in series, as they are in this project, the voltage stays the same but the amperage is additive. So if you have two solar panels putting out 5 amps each, that is 10 amps total.

To be more specific, watts/volts = amps. In this project, I have 200 watts/12 volts = 16.6 amps max. Always add 25 % for safety margin and then round up.  16.6 amps x 25% = 4.16

16.6 amps + 4.16 = 20.76

In this example, a 25 or 30 amp charge controller would be sufficient.  I went with a 30 amp.

-Wiring the battery bank:

The batteries are also wired in parallel. All the positive terminals are wired together and all the negative terminals are wired together. This means the voltage remains consistent. You have 12 volts coming out of the solar array and thus you want a 12 volt battery bank.

As you can see in the image that all of the battery negative terminals (black) are wired together and all of the battery positive terminals (red) are wired together.

-Wiring of the charge controller and inverter to the battery bank:

The positive and negative leads of the charge controller should not be wired to the positive and negative terminals of the same battery.  The same is true for the inverter. If you do this, it produces unequal charging and cycling of the batteries and will reduce the life span of the battery bank.

It is better to place the positive and negative leads of the  charge controller and inverter  at opposite ends of the battery bank. This produces a more even rate of charging and drawing of the battery bank. In other words, a more balanced use of the battery bank.

In this image you can see the inverter cables, which have multiple strands, are wired at opposite ends of the battery bank. Also, the wires from the charge controller, the ones coming into the image from the upper left, are also wired at opposite ends of the battery bank. Again, this produces a more balanced charging and drawing of the battery bank, balances use, and extends the life of the batteries.

-Sizing the inverter:

As a general rule, the size of the inverter should be similar in size to the solar array. In this particular project my solar array is 200 watts. So, a 200 watt inverter would be appropriate.  However, as a rule of thumb, I install equipment with power ratings that far exceed my general use. I do this so that I can expand my solar array at a later date if desire without having to change out any equipment.

The inverter that I used in this project was savaged from another piece of equipment. It has a 1500 watt rating. But, I shopped around online for inverters that would be suitable for a project of this size. That is how I came up with the dollar figure listed below for the cost of the inverter.

Summary of Expenses for this Simple Solar Project

Solar panels:               $228.97

Mounting Brackets:   $19.99

Lumber:                       $15.00

Hinges:                         $6.00

Solar panel cables:     $20.50

Connectors:                  $17.33

Charge Controller:      $49.99

Batteries:                       $79.99

Inverter:                         $49.99

Fan:                                 $58.30

Total Cost:                 $546.06

Does this simple solar project makes sense?

Let’s take a moment and analyze the cost of this project.

With average sun exposure, I will be generating about 1 kilowatt of electricity per day. So approximately, 365 kilowatt/hours per year. Doing the math, that means my average cost is $1.496 per kilowatt hour of electricity production.  At this time of this writing, the average consumer cost of electricity in Colorado was 11.05 cents per kilowatt hour.

So, despite my accomplishment of this simple solar project, does it actually make sense?

What were my other options?

Option One

-Run wiring from my primary solar array to the green house

Due to the distance of the primary solar array to the green house, the cost of wiring alone would have been about $900. This is because it would have to have been very large diameter wire in order to reduce the resistance to the flow of electricity.  Additionally, the wiring would have to be buried in conduit and I would have to dig a 12 inch deep trench for 300 yards.

Option Two

-Bring in electrical lines

The last time I checked, the utility company wanted to charge me almost $30,000 USD to run electricity to my cabin. The of course I would be paying them for electricity every month.  My primary solar array cost me about $9,500 USD and has been in place for 3 years.  My closest neighbor pays about $400/month for electricity. Which means, my solar array paid for itself 12 months ago.

Why this project makes sense

Obviously what I did was the least expense option. Additionally, I now have a small stand-alone solar electric system that will function independently for years with little or no maintenance.  I did this with minimal equipment. Once again, I am producing my own electricity.

Remember, as long as someone is in control of your resources, they are in control of your life.  Why not push yourself to learn some of the skills of self reliance and be in more control of your life.

Other post of interest

23 Reasons to Choose Solar Power

What Makes a Good Solar Site

Introduction to Renewable Energy Systems

How I Built the Log Cabin

Go off grid and live well,

Patrick