The Four Essentials Of Off Grid Solar

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An off-grid solar electric power system is an ideal prep for the modern survivalist in that it can partially or totally relinquish you from dependence upon other systems, which themselves are vulnerable to disruption or breakdown.

Off-grid systems also enable the ability to live away from the main stream, which opens the door to properties which may be more affordable than others that require connectivity to public systems. Even if living in suburbia, installing an off-grid system to be next to the existing grid system will provide you with a completely separate electrical circuit (separate outlets, etc… however you design it), reduce your dependency on the grid system, as well as provide a back-up means of electrical power during an outage or disaster situation.

One notation however, be aware that while your neighbors are all without electricity, it may be obvious that you still have yours and invite knocks on your door if the situation endures too long.

In fact, this will be true in all aspects for those that have prepared. If the down-time of a disaster becomes longer than the period of time that others are able to endure (those that have not prepared), you will surely begin to get people at your door looking for help and handouts. At this point, some serious judgment on your part will need to take place. Personally, I believe preppers should plan to keep some extra for charity in this situation, while at the same time not advertising your true storage. In most cases, giving to others will create beneficial good, which will come back to you in one way or another.

Back to off-grid solar power…

This summary is intended to provide a very high level overview. There is much more to it than just these basic elements, things such as circuit breakers, interconnecting cabling, safety considerations, and technical know-how.

Having said that, the following comprises the major parts of a typical off-grid system and can be split up into four areas, each with their own function and purpose as listed here in the correct order of their functions.

• Photovoltaic Solar Panels
• Charge Controller
• Battery Bank
• DC to AC Inverter

PV Solar Panels

The PV (PhotoVoltaic) solar panel is where it all begins. A typical solar panel is made up of an array of many small individual solar cells, made of crystalline silicone, each connected together to provide a usable amount of total power. Sunlight (photons) strike the crystalline silicone wafers, which convert that energy into electricity.

A typical individual solar panel that is used in an array of panels may contain enough individual cells to produce about 200 watts (there are lots of different sizes). The more solar panels, the more power you get. This is where the majority expense of the system resides. These days, a 200 watt solar panel is priced between $600 – $800.

Without getting into the detailed methods of calculating the number of panels required (which are different from calculating for a grid-tie system – one that is tied into the local utility grid), suffice it to say that most people are familiar with the term, ‘watts’ (light bulbs anyone?). A ‘watt’ is a unit of power.

Basically how this works is that you determine the wattage of an individual item that you would like to power, and multiply that number by the number of hours per day that it is running (the result is a unit of energy which is required to power that item – power times time). You do this for each item and add them all up to get a final number.  You probably want enough power to run a refrigerator, maybe a separate freezer, a number of lights, along with enough left-over energy to occasionally run a washing machine, kitchen appliance, radio or TV, and a computer.

For example,

• Refrigerator (100 watts  x  12 hours  =  1,200 watts per day, also known as 1.2 kWh, or 1.2 kilowatt hours, which is the same as consuming 1,200 watts in one hour) In reality a refrigerator cycles on and off all day, so in this basic example I’m using 12 hours instead of 24.
• Chest Freezer (60 watts  x  12 hours  =  720 watts per day)
• Energy Efficient Light Bulbs (20 watts  x  6 bulbs  x  4 hours  =  480 watts per day

This very simple example adds up to use 2,400 watts of energy in a given day, or 2.4 kWh. Lets add another 600 watts overhead for other items that may be operated throughout the day. This brings us to 3,000 watts of energy consumed throughout the day, or 3 kWh.

Now you need to discover the worst case scenario regarding the number of hours of ‘good’ sunlight that you will get per day in your geographical location. Lets say the worst case is during the heart of winter, with 4 hours of usable good sunlight to provide electrical charging capacity. This means that during those 4 hours, you will need to come up with 3,000 watts of energy. So, 3,000 divided by 4 hours equals 750 watts of solar panel power to absorb and convert 4 hours of solar energy into 3 kWh. This means we would need four 200 watt panels. Well, not exactly… this is a best-case scenario where your panels are tracking the sun and angled exactly right all the time, etc.. Lets say you don’t have a tracker and your panels are simply installed on the roof at some optimum fixed angle. In this example you may actually need 6 panels to be safe. You see how this works? A lot of this is about having a safety margin so you don’t run short.

Charge Controller

The charge controller is the electronic device that goes in between the solar panel array and the battery bank. It provides a proper amount of electrical charge to the batteries and is intelligent in that it automatically adjusts itself depending upon the current load on the system and the current charge of the batteries versus the amount of available power from the solar panels at any given moment (at least the better ones do this). A good charge controller will also perform maintenance functions to your batteries to help keep them in optimum condition and to prolong their life. The charge controller is not terribly expensive and is an essential component in the overall system.

Battery Bank

The battery bank is unique to the off-grid system. Since you do not use up all of your daily energy requirements during daylight hours, an off-grid system will store the energy that is collected over time during daylight into a bank of batteries to be used as energy later. The batteries used in solar power systems are manufactured specifically for the situation where lots of its energy is drawn off over a relatively long period of time, whereas a typical car battery draws off energy over a very short period of time when starting the engine. Solar designed batteries are a type of ‘deep cell’ battery with a rugged and heavy duty internal design.

An additional consideration is the number of backup days that you want to have energy in reserve, during times when the sun is covered by clouds during bad weather. It is important to have a few days reserve energy, which simply means having more batteries to store that energy. ‘Simply’ may not be the best word here, because these batteries are extremely heavy, require special considerations when connecting them into an array, and also require special considerations for their placement (environmental temperature, proper exhaust – depending on battery type, and safety).

Dc to AC Inverter

The Inverter is located at the last stage of the solar power system. It’s job is to convert the DC energy from your battery bank and solar panels, into AC energy that is used in the typical home. Without giving an electronics lesson, ‘DC’ refers to direct current, and ‘AC’ refers to alternating current. AC power is what is generated in utility power plants, and is what most all home appliances, etc.. are designed to handle and consume as energy. Therefore, you will need this inverter unless you have special appliances and lighting to handle DC power.

Today’s modern inverters can be very efficient, so hardly any power is lost during the conversion process assuming you’ve purchased a quality unit. There are cheap inverters out there which I caution against for several reasons, including the ability to handle short-term high current loads from motors and compressors starting up (refrigerators and freezers for example). The good units provide pure sine wave AC power and will not damage your appliances.

So to sum it up, an off-grid solar power system is a reassuring bit of insurance when you are already connected to the grid, and also provides options for living in remote areas without grid hook up. It is not inexpensive, and can also be very expensive if the system is large. I would never recommend money spent on this capability until and unless all debt is paid off and many other preps are in place first.



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