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Q: What are photovoltaics?
  The term photovoltaic (PV) means to convert light directly into electricity though a photochemical reaction involving silicon, a semiconductor material ideal for this task due to its light sensitive properties. Photovoltaics are made of silicon, plus boron and phosphorous. In the presence of sunlight, an electric current is produced from the release of electrons contained in these three materials' atoms. PV modules involve no moving parts and produce no pollution.
Q: What is the difference between on-grid and off-grid PV systems?

Grid-connected PV systems operate in parallel with your local utility service, providing a supplemental source of clean, renewable energy. Direct current (DC) power from the solar modules is feed to an inverter that converts this energy to utility-grade alternating current (AC). This energy is then feed into a building's load center, helping offet incomng utility power. These systems can be designed with storage batteries and a special "bi-modal" inverter to act as a back-up power source if utility power fails.

Off-grid PV systems are designed as the primary power source for remote locations without utility service. These systems always have deep-cycle storage batteries and often are coupled with a fossil-fuel generator to provide reliable service regardless of weather conditions. These are called hybrid power systems.

Q: How do grid-tie systems work ?

There are two types of grid-tie systems, those with storage batteries and those without. Systems without batteries use PV modules connected directly to an inverter to create 120-volt utility-grade electricity. Power is produced during sunlight hours and is fed directly into a building's electrical load center. This solar power supplements the utility power and reduces the amount of utility power used. If there is extra solar generation above what is needed in a house, it is sent back to the utility grid, spinning the customer's meter backwards.

These systems are simple, reliable, and produce the most kilowatt-hours (kWh) per dollar invested. But there's one thing they won't do - keep the lights on during a power outage.

The second type of grid-tie PV system, those with batteries, overcome this limitation by use of a battery bank to store energy and a special "bi-modal" inverter. During a brownout or blackout, the inverter will disconnect from the utility and draw energy from the sun or battery bank to power house loads. The number of appliances that can be run, and the length of time they can run, depends on the size of the inverter and the battery bank.

Q: Which system is right for me?

• There are several key factors that must be considered when making this decision.
• Your current electrical consumption. What % of your electric bill would you like the system to provide? 
• Whether you want battery backup or not. If your primary concern is power outages, then you will need batteries.  
• Your interest in being able to sell or "net meter" excess electricity back to your utility. 
• How much non-shaded roof or ground area is available?
• Where does it make the most sense to locate the system?
• The amount you would like to invest in solar energy?

Q: How many Kwh do I need?
  The first step in configuring your solar system is to define your load. There are two aspects you need to know: power and energy. To determine the power requirements look up the "Power Rating" on the appliances you wish to run simultaneously. Next, determine how many hours per day these loads will run.

You can also check your existing electric bill for "Kwh per month" consumption. This will tell you how many Kwh of energy you'll need each month.
Q: Will the system work on gray, cloudy or overcast days?
  Yes, because photovoltaic energy (PV or solar power) uses the full spectrum of light, the ultraviolet rays are still charging the system, even when the sunlight isn't visible.
Q: Does the system work when the regular power (the utility grid) is down?
  Yes, if you choose a system that has a battery pack, it will provide power to those circuits you select as critical loads. You might choose the refrigerator, computers, some lighting circuits, heater fan, TV or whatever you feel should have back-up power.
Q: What happens when we generate more power than we're using?
  Excess electricity is fed back into the utility grid for others to use. Your electric meter spins backwards to credit you for all energy sent into the electric grid. You are billed for the difference between the electricity you generate and the energy you use.
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