Solar Science: How the Sun Can Power Your Home

When you harness the power of the sun and use it to power your home, what exactly is happening?

With rising power prices and growing concern over the environmental effects of powering our homes with fossil fuels, there are many reasons to consider renewable energy sources. Solar panels are perhaps the most affordable option, and their popularity continues to grow around the world.

You may have heard about many of the benefits of using solar power, such as lowering your electricity bills and reducing your carbon footprint, but you may not understand the science behind it.

The smallest part of the solar rooftop array is the PV cell; when people ask how do solar panels work, this is the place to start. Each PV cell has two layers of silicon held by metal plates; the plates connect to a thin wire. In the top layer, the silicon has been doped, or treated, with phosphorous, giving it a negative charge.

A negative charge means an oversupply of electrons. The bottom layer has been doped with boron, so it has a positive charge, or a lack of electrons. The difference in charge creates a kind of force field between the layers, through which energy cannot travel.

However, when a conductive material connects the two sides, the electrons have a path along which they can flow, which creates an electric circuit. It is as if there are two houses next door to each other. One house has 30 puppies; this is the oversupply, or the phosphorous-rich top layer.

The other house has only five pups; this is the undersupply, or boron-doped bottom layer. The dogs represent electrons. A river (the force field) runs between the houses, but there is a bridge (metal plates and wires) a mile away. At night, the puppies are asleep, so there is no movement between the houses.

At sunrise, everything changes. Photons, or light particles, bombard the cells and knock electrons loose on both sides. In other words, they wake up the pups in both houses and chaos ensues.

Naturally, the dogs want to move from the crowded house (negative layer) to the less-crowded house (positive layer), but the river won’t let them. Eventually, the puppies run the mile along the river to the bridge and can get to the other side.

As you may expect, the puppies use a great deal of energy in their run along the river, over the bridge, and to the positive house. But how is that energy captured? The bridge (metal plate) is the key. Imagine that the bridge’s floor starts out covered with a shiny clean tarp but is quickly covered with muddy pawprints; each pawprint is one unit of energy.

Once the puppies have crossed the bridge, the tarp is picked up and taken to a huge shed for storage with other tarps that also have numerous pawprints. Obviously, the wires are the tarp collection system and the storage shed is the battery that holds the power until it is needed.

This process is repeated throughout the day; as long as photons are striking the PV cells, power is being generated and carried away for use or storage.

Now that you understand how the smallest piece of the puzzle works, it is easy to see the bigger picture. Most solar panels hold 60 PV cells, so the panel will generate 60 times as much power as the one cell. For example, most new PV cells generate up to 5.33 watts which means the panels can generate around 320 watts.

A solar array, like you might see on a rooftop or along a hillside, contains a collection of panels that all connect and send power to one site where it can be used immediately, stored onsite or sent to a power grid.

Typical consumer household arrays include between 20 and 40 panels but your power needs and space limitations will dictate your particular configuration. Your solar provider will help you calculate the optimal number of panels for you.