Monday, July 24, 2017

DIY Solar System

There are some good power systems like the enCube (left), with a 100 ah battery, which are nicely packaged.  You can also build your own system with fewer bells and whistles but with more power for your money.  A Do It Yourself (DIY) system allows you to tailor it to your needs and it serves as good training too.

The first step is to determine your needs.  What do you want to power, and for how long?  The answer could range from powering a single outlet for a few hours to powering your entire house for ever.

Lower temperature settings on heating and cooling appliances will reduce energy consumption.

There are simple tools like the Kill-a-watt ($20) that will help you determine exactly what load you will need, or can run.  This is a wise investment to avoid building a system that doesn't meet your needs.

In this case, the small fan above is using 9.6 watts on its low setting and used 21 watts on its high setting.

So after we determine our power requirements, let's suppose that we need 2,000 watts per day under two scenarios.
  1. The first scenario is to have only enough power to last for 1 day
  2. The second scenario is to be sustainable at this level indefinitely
The first scenario (1 day) can be achieved with sufficient battery capacity, charged by your household electricity.  This is shown below.  Note that this includes using only 50% of the battery capacity which will extend the life. An alternative would be to have 6 of the enCube's ($1,000 each) above strategically located around your home to achieve the same results but at a much higher cost.

This is 126% of our daily needs.

The second scenario (indefinitely) will require the addition of power generating solar panels capable of generating the daily needs of electricity.

Here is the math: 4 - 100 watt solar panels ($600) with 8 hours of sun delivers  the following wattage/day:

Power generated (theoretical) = 4 X 100 X 8 = 3,200 watts.

At a realistic 70% efficiency (3,200 X 0.7 = 2,240 watts/day) the actual watts/day generated is 112% of our daily needs which would allow an additional safety factor.

Our 4 solar panels will generate 100% of our 2000 watt daily power needs plus 12% extra per day.  The battery will handle our daily needs (using only 50% of the battery capacity to extend its life) and hold an extra 26%.  This Solar Power Kit sells for $1,500.

It will take the extra solar generation capacity two days to charge our battery's extra storage capacity.  This extra will deliver 3 hours of extra power per day, or 6 hours (1/4 day) of extra power every other day. Any extra power generated beyond two days will be lost as there is no more battery storage capacity.
So suppose we add additional battery capacity.  This gives us 168% of our daily storage needs or an extra 16 hours.  However, it will take our extra solar generating capacity about 5-6 days to charge this extra battery storage.

Supposed we add two additional batteries. This gives us 210% of our daily storage needs or an extra 26 hours.  However, it will take our extra solar generating capacity about 9-10 days to charge this extra battery storage.

Our next step would be to add additional solar power generation, providing that our electrical infrastructure can handle it.  This may include our wiring, charge controller and 12 VDC to 120 VAC inverter.  With this (below), it would only take 3 average days or 24 hours to charge the extra battery power.

Below is a rough example of what a simple standby system would look like.  Buying a Solar Power Kit will make your first solar project much easier. 

In most cases, home solar systems require a licensed installer, but small stand-alone systems are something most handy men can do, but do NOT try to integrate them into your home wiring unless you are an electrician. 

E-mail us with questions; good luck.

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