A Basic Solar Power System Description and Diagram

October 12, 2011, by Ken Jorgustin

Solar power systems vary widely in their power producing capacities, and the cost of implementation is directly proportional to that capacity.

Solar energy is not cheap. In fact, one could argue that from a cost savings point of view it is not very practical at all because it typically will take many, many years to reach the break-even point when considering the cost of your local utility electricity… I’m talking roughly 5 to 15 years in many instances depending on your usage.

However, despite the cost of solar power systems, for many folks it is a worthwhile investment for reasons other than saving money on your utility bill. If your property is far from the nearest road, it may actually cost less to have solar power than to pay to run electricity to your property. If you have an RV, or boat, solar power is a great way to have electricity present.

For many, simply having a very basic solar power system is reassurance that they will have some amount of limited power at the ready, just in case…

Without going into great detail, I thought that I would illustrate a very simple and basic system that could be assembled to provide enough power to operate some lights, a TV, a computer, enough to recharge power tools or other items… a 800 watt system (with caveats).

(1) Solar Panel (180 watt with MC4 connectors)
(1) Battery Charge Controller (15 amp, 225 watt – 12V)
(1) Battery (12 V, Sealed AGM, 55 AH)
(1) Power Inverter (12 VDC to 120 AC, 800 watt)
(2) Battery Cable Kit (4-AWG)
(1) Solar Array Cable (50 feet, MC4 ends – cut it in half)

With the components listed in the basic system above, while the sun is shining you could continuously run (consume) up to about 140 watts of power, or up to 800 watts for about half an hour if the battery is fully charged. Even when it’s cloudy, you will probably still have access to about 100 watts continuous.

When it is dark, and since we’ve included a battery in the system, you will have access to about 500 watts for one hour (or 100 watts for 5 hours, or 50 watts for 10 hours, etc.). The amount of available energy after dark assumes a maximum allowed 80% battery discharge (never go below 20% battery capacity!), and assumes we’re using the particular battery listed above (55 Amp hour, 12 volt), and assumes 5 hours per day of charging sunlight.

Note that if you get two identical batteries and wire them in parallel, you will double your night time capacity, provided that they get fully charged during the day time.

The price tag of the very-basic system above is nearly a thousand dollars, and as you can see, it’s not cheap to achieve the energy capacity listed in this example. If we assume that your local utility company charges say, 20 cents per kilowatt hour (per thousand watts of consumption in an hour), you would not break-even with the price until you’ve consumed 4,755 kilowatt hours (that’s 4 million and 755 thousand watts of power). That’s the same as running 100 watts of ‘something’ for 47,550 hours straight (or a bit more than 5 years).

I’m not trying to discourage you by any means! I’m just pointing out the facts. Again, there are lots of reasons to have solar energy systems other than for offsetting the cost of local electricity! Like… preparedness!

Here’s a sketch of how the very basic system that I’ve listed above, would be connected together.

solar-power-system-diagram

A statement of caution… don’t attempt building your own solar energy system unless you have a basic understanding of what you’re doing. Maybe you know a friend who knows basic electricity… For example, if you don’t know what ‘ohms law’ is, then you probably shouldn’t be putting one of these together yourself. Designing the proper package involves a full understanding of power equations (P=IE), conversions, and other basic electronic understanding.

 

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