How Does a Solar System work?

There are two types of solar power systems available to homeowners: solar thermal, and photovoltaic. Solar Thermal systems collect heat from the sun, and directly use that to heat water or your home. Here at ECC Solar, we specialize in photovoltaic systems.

A photovoltaic (PV) system takes energy from the sun and converts it into electricity. The first step is when light from the sun hits the solar panel. The light creates a voltage difference between the panel’s terminals. When the ends of these terminals are connected, they create a Direct Current that flows through the wire. This is the same as the direct current that a battery creates. The appliances in your home run on Alternating Current, so the panels need an inverter to convert DC to AC. The inverter will produce AC power that will power whatever you have turned on. From here what happens depends on how much electricity you’re using, and if you have batteries. For systems without batteries, any extra power you’re not using will be fed into the electrical grid to help supply other homes. Your electric meter will run backwards when this happens. If you are using more energy than you produce, then the electrical grid will supply the difference.

If you have a system with battery backup, or if you are grid independent, then the battery will fill the same role as the grid. When producing excess electricity, direct current from the panels will be directed to charge the battery. When you are producing less than you use, or at night, the battery will supply direct current to the inverter to power your home. For grid independent systems, the battery can run out because of high usage, cloudy days reducing electricity collected, snow covering the panels, or other reasons. This is why grid independent systems typically have a backup generator that is automatically turned on by low energy.

An active solar thermal system works by using the sun to heat a fluid that is pumped through solar collectors. This fluid can be water, but in colder climates, an antifreeze like propylene glycol is often used to prevent the lines from freezing in cold weather. As the fluid heats up, it runs through insulated pipes down to either the water heater, or to pipes embedded in your floor. If you heat your house with solar, the fluid circulates through your floor, warming the house as it moves along. If you are heating water, then the fluid is pumped into a hot water tank through a heat exchanger. A heat exchanger works by creating a large surface area between two fluids, without letting those fluids mix. A simple example is where the water sits in a large tank, and the fluid from the panels is pumped through lots of small pipes that go through the water tank. An electric backup is typically used to meet peak demands or long cloudy periods.