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The Solar System

How many photovoltaic panels and batteries do I need?

The first step is to determine how much power the appliances and lights you intend to run draw. There are a couple of ways to determine this. The wattage of a UL listed/approved appliance can usually be found near the AC power cord. This may be in amps or watts. If it is in amps, a simple formula will let you convert it to watts: Volts x Amps = Watts. In other words, if your appliance draws 4 amps, the formula would be 120 x 4= 480 watts.

Another method is to use a device that monitors how much power your appliance uses. If you don’t have the patience for math calculations and want quick answers, it may be another way to go. We can help you with this part.

The average refrigerator use varies from as low as 800 watts/h per day for a new Energy Star refrigerator to as high as 3000 watts/h per day for an older unit. At start-up, your refrigerator may have a higher draw, so you want to err on the high side when you figure how many watts of power you need. Also, determine the wattage of any lights or other items you intend to run.

Once you have determined the wattage, you need to run all your appliances. Determine how many hours each day they will run. For instance, your refrigerator can run approximately 1/3 of the time during a 24 hour cycle, or 8 hours a day. The light that draws 75 watts may run 3 hours a day. Once you have determined how many watts you use a day from each appliance, add them up to give you the daily watt-hour results.

For example:

Refrigerator 1600 watts
Lights 400 watts
Misc 400 watts
Total 2400 watts daily watt-hours

Now, to allow for bad weather when the sun doesn’t shine, multiply the daily watt-hour result by three. This provides a buffer, in case you aren’t able to recharge the batteries on a daily basis.

Because you should not discharge the batteries below 50%, multiply this number by 2. This will give you the total battery capacity your system needs to store to run for three days. We also add a 20% buffer knowing that the battery will age and lose capacity after a couple years. In this example, 5760 watts.

How much maintenance do solar systems require?

Solar systems generally require very little maintenance. Just spray them down with a hose at ground level every month to remove any debris or dust that may have gathered on the panels. Now the batteries may require some maintenance (periodic electrolyte refilling, testing…) depending on their type, you can choose maintenance free batteries as well to avoid the maintenance.

How long will a solar system last?

Photovoltaic panels are rated to last over 25 years.

How does solar help the environment?

Solar will help reduce your carbon footprint and is also a clean alternative to natural gas and coal. By switching to solar you contribute to less pollution in the air which means that the air we breathe will be cleaner.

Charge Controllers

Why do I need a Solar Charge Controller?

A charge controller regulates the charge on the batteries, giving full power when necessary and reducing the charge as the batteries require less. This is important for maintaining the health of the batteries.

What is a PWM charge controller?

PWM stands for Pulse Width Modulation and is basically a 3-stage charging cycle type controller. This is the old way to recharge batteries with a solar system. What is a MPPT charge controller? MPPT stands for Maximum Power Point Tracking. This is a newer type controller that not only provides multi-stage charging, but it also delivers more power to the batteries by matching the battery voltage to the solar panel voltage. This makes them more efficient especially in varying levels of sunshine. They can boost your production by 30-40% compared with PWM. They're also different quality and it is important to choose the right controller.

Power Batteries

Do I need a Power Inverter?

This is the only component of a solar energy system that is not absolutely required. However, if you don't use one, you will not have Alternative current (120VAC, 120/240VAC…) and will have to use battery power alone. This might be acceptable in a small RV or cabin, but most people want to use normal AC appliances. Most systems are now using Pure sine wave Inverter Charger, nowadays you need a pure sine wave inverter in order to have all your electronics devices working properly and not having problems with your appliances electronics boards.

What's the difference between 12, 24, and 48 volt inverters?

This refers to the input voltage from the battery bank. The main consideration is that at higher voltages the current is less so that you can use smaller wires between your solar panel array and your battery bank. Of course, when you decide on a system voltage, the Solar Panels, Inverter, and Battery Bank all need to use the same voltage. The bigger the system we install, the higher the voltage. You always have to take in consideration futures needs.

What is a Grid Tie inverter?

If you are connected to normal Utility company power and just want to add some Free Sun Power electricity to reduce your electric bill and you do not need a independent system, it is possible that a Grid Tie inverter will suit your needs. With a Grid Tie inverter, whatever electricity that your solar panels produce will reduce the amount supplied by the power company, in effect lowering your bill. For this setup a large battery bank to store the power for later use is not needed. Unless you have frequent power company outages, you will not need any batteries at all.

What's the difference between a true sine wave inverter and a modified sine wave inverter? The AC sine wave of a true sine wave inverter is just as good as the utility company's AC power. A modified sine wave inverter is not as close, but is still quite satisfactory in some cases. Certain motor control circuits don't like the modified wave. Modified sine wave inverters are also much less expensive.

Storage Batteries

What is meant by Flooded batteries?

Flooded batteries have those little caps on top and you must add water (distilled) to them from time to time as the charging process boils off some of the water as hydrogen gas. They should be installed in vented boxes and not used indoors or near spark or flame. Those batteries are lead acid batteries, regular deep cycle batteries or OPzS tubular deep cycle batteries.

What is a sealed battery?

Not to be confused with maintenance free, a sealed battery has no service caps and water is never added. They also do not out gas during the charging process and are safe to use indoors. This usually means that the temperature of the battery will be more constant which translates into more efficient operation. You can choose between AGM or GEL batteries.

Should I use Flooded or Sealed batteries?

While you can safely use sealed types indoors, they are more expensive than flooded types. So, cost factors and where you plan to locate the batteries are the main deciding factors.

AC Generators

Why should I have a Generator if I have Solar Panels?

When supplying your own power, it's a good idea to have back-up power for 2 reasons. Number one is that in the winter (depending on your location) you will often have too many days of low sunshine to supply all your electric needs from the solar panels alone. Reason number 2 is that you will probably have some equipment that uses large amounts of power but is only needed some of the time. (say filling a water tank with a large pump)

How long does the generator need to run?

During bad weather, you will need to supply the bulk of your battery charging with the generator. For a medium sized system, with no sunshine at all, an hour per day will usually provide enough of a charge for the batteries. A large system may require up to 10 hours depending on the system.

What size Generator should I use?

Please contact a specialist in order to calculate the loads onsite plus the charger, it is important to have the right size of generator in order to be the most effective. This way you will burn less fuel. A generator with an auto start is the best way to manage your complete system and get more cycles from your batteries, let the AGS do the work for you.