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SOLAR SCHOOL

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Solar energy is a great source of power for everyone. However, every application does not always fit solar energy. We have developed this section to help the novice learn a little about solar energy, and figure out of they have an application suitable for the Solar Stik™.

The first thing we will cover is a little about your electrical system. There are 2 commonly used types of electricity, AC (alternating current) and DC (direct current). Both of these types of electricity are measured in voltage. Most small DC systems use 12 volts (12VDC), and most AC systems use 120 volts (120VAC). A simple rule to follow when determining which type of system you are using is whether the power is produced from a battery bank, from a generator, or from a power line. Anytime the primary power source is a battery, then that is a DC system. DC systems are commonly found in motorhomes, sailboats, powerboats, cars, and campers. The Solar Stik™ produces 12 volts of DC power (12VDC), so if your power comes from a battery bank, then you are a good candidate.

Next, let's dive a little deeper into the specifics of your system. We need to figure out your loads. A load is anything that consumes power in your electrical system. "VOLTAGE" is the force that "pushes" the electricity through the wire... the higher the voltage, then the higher the force of the "push". The amount of electricity that flows through a wire is "current", and is measured in "AMPS". The current flows through the wire to the load, and the electricity is then consumed. We measure the amount of power consumed in "WATTS". For instance, let's say you own a camper and the two loads in your electrical system are a 12 volt DC refrigerator, and a 12 volt DC light. Each one will consume different amounts of power, and as we discussed, consumed power is measured in watts ( you will see that a "watt" is represented by the letter "P" [for "power"] in electrical formulas). There is a commonly used formula to determine the characteristics of an electrical system, and it is as follows: VOLTAGE, multiplied by AMPS, equals POWER (V x A = P).

This formula can be used to determine all three values:

V x A = P

V = P / A

A = P / V

Let's say that your 12 volt DC light consumes 25 watts of power, and you need to know the current it uses. We need to use the following formula: AMPS equals WATTS divided by VOLTAGE

(A = P / V). Inserting the values that we know, we then have A = 25 /12, and solving the equation we have A = 2.1 amps of DC (direct current) consumed by a 25 watt light bulb in a 12 volt system.

Pretty easy, right? Good!

Now let's look at the refrigerator. You would be able to find the electrical ratings in the literature for the refrigerator, or on the data plate affixed to the unit. Depending on the manufacturer, you may be reading the power consumption rating in watts or amps. If you need to, reapply the formula you learned with the light to get the rating of the amps that the refrigerator draws. Let's say that your math resulted in the answer of 5 amps.

Now let's figure out the total of amperage draw for the camper's DC system. Simply add the values of the amp ratings of all of the loads. The total amp draw for the light and the refrigerator is 7.1 amps!

Now that we have the total load for the system, we need to learn how it relates to your 12 volt battery bank. Batteries store energy, and since they do not consume or produce energy, we can't measure their capacity in watts. The voltage rating we know is 12 volts. That leaves "amps" as the unit of measurement for battery capacity. If you were to look at a deep cycle battery, you will probably find a label that rates the battery capacity in AMP-HOURS. This relates to how many amps can flow from the battery to the load, in the amount of time it takes to render the battery "discharged". For example, if the battery label reads 125 amp-hour reserve capacity, then it means that it can provide 25 amps continuous for 5 hours (25 amps x 5 hours) and at the end of 5 hours, the battery would be fully discharged.

Why is this important to know? Because the Solar Stick recharges the 12 volt batteries at a specific rate, and you will need to know the loads in your particular system to calculate how much current you need to replace the power consumed by the loads. Correct battery bank size can also be determined by the load requirements. Are you starting to get the picture?

Let's back up for a minute. We figured out that the camper refrigerator and light total current draw was 7.1 amps when they were both running, but you may not leave the light on all the time, or the refrigerator may only actually run 20 minutes during the hour. To get an accurate picture of your system, you will need to get the sum total of 'hours per day' of refrigeration and light operation time. Let's say that you added it all up and figured out that the total amp draw from the batteries was 7.1 amps for 8 hours in a 24 hour period. This means that you are consuming about 57 amp-hours per day, right? (7.1 amps x 8 hours = 56.8 amp-hours) Now how are you going to replace those 57 amp-hours that you consumed from the battery? Let's take a look at the Solar Stik™ power production. It produces about 6 amps, therefore, it would need to produce 6 amps for 10 hours to replace the current used by your DC loads. This amount of current would keep the batteries fully charged and allow indefinite use of your refrigerator and light!

The Solar Stik™ has two 50 watt solar panels, and added together, we can say that we have 100 total watts of solar power. (Notice that the panels are rated in watts, they create power, not consume it. They are still considered a "load" though, and as such, they are rated in watts) Locate the solar panel data plate to obtain voltage and amperage ratings. The panel rated operating voltage is about 18 volts. Using our standard formula V x A = P, we get A = P / V (amps = 100 / 18). We find that the Solar Stik™ panels produce 5.8 amps, or about 3 amps per solar panel. On average, one can expect to be able to get 10 hours per day of direct sunlight, providing the user with about 60 amp-hours of recharging ability.

Now, you probably noticed that the Solar Stik™ operates at 18 volts, and you may be thinking "but my batteries are rated for 12 volts". This is why we recommend (and provide in every package) the use of a MPPT (Maximum Power Point Tracking) charge control. This charge control converts 18 volts DC to about 14 volts DC by using a small computer. Allowing the solar panels to operate at their maximum rated voltage instead of the battery voltage results in an amperage boost to your batteries. Let's perform the math to see the difference:

A = P / V

A = 100 / 14

A = 7.2

Using the MPPT charge control, we just increased the current from 5.8 amps to 7.2 amps... an increase of about 25%. Other types of charge controllers force the solar panels to operate at the battery's voltage. In other words, the 3 amps from the solar panels multiplied by (the battery voltage) 12 volts, yields only 36 watts of power being produced.

V x A = P

12 x 3 = P

36 = P

There is a substantial power loss associated with this type of configuration. It is always better to use a MPPT charge controller with a solar system.

In summary, it is important to find out the total current draws for a particular DC electrical system, so that one can build an effective electrical system with effective power replacement options. (solar, wind, water power generators).

Using the formula V x A = P

1. Find the amp-hour ratings of each individual load

2. Determine how long the load runs in a 24 hour cycle

3. Add up the total amp-draws of all the electrical loads for a 24 hour period (total amps x hours)

4. Determine how much energy must be produced to replace the current drawn from the batteries.

"What about using an inverter in my system to run a 120 volt appliance? How much power will it draw?"

Let's say that you have a microwave oven that is rated at 700 watts. If we know the microwave uses 120VAC, then we can figure out the amperage it requires to operate by using the same formulas we used in the DC circuit:

A = P / V

A = 700 / 120 = 5.8 amps

The microwave uses 5.8 amps of AC (alternating current) from a 120V source, which then must be converted to DC (direct current) to find out the draw from the battery (12V) source. An appliance working off a 120V system will consume ten times more power than its 12V equivalent. Therefore, the ten-fold difference must be taken into account when converting AC to DC. An inverter in the DC system allows you to run AC appliances by converting 12V to 120V. Since the inverter consumes power in the act of converting power, we must also take that into consideration. For simplicity, the power of ten is increased to eleven when calculating 12V DC to 120V AC power use.

A= P/V

A=700 / 120

A= 5.8 amps in an AC system

Using the AC appliance in a DC system: 11 X 5.8A= 64A

...the 120VAC microwave will draw 64 amps of DC current from your batteries while operating.

When possible, use a DC appliance in any application where your power source is a battery. You will use a fraction of the current compared to an AC appliance.

For example, a DC refrigerator will consume a fraction of the power that an AC refrigerator will consume, but the result is the same... cold food storage. Dedicating some extra effort in finding DC appliances in place of traditional AC appliances when building your DC system will prove extremely beneficial. The internet allows for easy product sourcing and comparison regarding DC appliances.

Some readily available DC appliances include:

• laptop computers
• TVs
• stereo systems
• fans
• coffee makers
• blenders
• refrigeration
• water pumps
• lights
• communications equipment
• handheld electronics
• rechargeable tools

Many of these items are used every day by people who have no idea that they are using a DC powered product. When purchasing an electrical appliance, remember to ask if a 12 volt DC adapter plug is available for the product.

Now you need to know a little about solar panels to complete your training. Solar panels work at their rated capacity in direct sunlight. So as the sun drops lower to the horizon in the late afternoon, most flat-mounted solar panels gradually lose their ability to generate power. This means that a fixed mounted panel system works at rated capacity for about 3 to 4 hours per day, and summarily, they are inefficient means of power production. The Solar Stik™ has the ability to follow the sun from dawn to dusk, maximizing the solar panel's power production. Now you can see why the Solar Stik™ revolutionizes the solar industry. Even if one's power consumption is greater than what the Solar Stik™ can reproduce in one day, the fuel cost savings will be substantial if the traditional engine-driven DC recharging systems operate less due to the employment of the Solar Stik™. Beyond the addition of a Solar Stik™ there are yet more ways to increase power production. A boat, for instance, could add a wind generator, or an RV could have additional flat mounted solar panels on it's roof. The methods and equipment for power production are numerous.

There are two commonly used types of solar panels, multi-crystalline and mono-crystalline. Both are excellent and efficient means of DC power production, each having a small advantage over the other. The multi-crystalline operates better in a shaded condition than the mono-crystalline, but is less efficient in direct sunlight than the mono-crystalline.

Easy, right? There are many variations to the scenarios that we have presented... many requiring more math and understanding of electrical systems, but hopefully we have given you a basic understanding of solar energy and it's advantages over traditional "fuel-driven" DC recharging methods.

For a detailed introduction on how solar panels generate electricity from sunlight, please visit the following: science.howstuffworks.com

For a detailed synopsis of the Solar Stik™ on how the Solar Stik™ works, click here.

To see a list of AC and DC appliances and their power consumption, click here