A User's Guide to Solar Power

While many people are interested in using sustainable energy sources, the terminology can make the process of “going solar” seem more difficult than it really is.

Before contacting solar installers in your area, learn more about how solar power works, and what to look for when installing panels at your home or business.

Important terms you may come across in research

  • Direct Current (DC) – Energy captured by solar panels that can be stored.
  • Alternating Current (AC) – Electricity that flows directly from the energy source into your wall socket. DC energy is converted to AC energy through an inverter, allowing you to use it at home.
  • Inverter – A device that converts DC energy to AC energy. The AC is fed into your home from the inverter, much like it would from an electrical provider.
  • Photovoltaics – Materials that convert sunlight into electrical energy.
  • Photovoltaic Cells – Electricity producing devices consisting of silicon-based semiconductor materials
  • Photovoltaic Modules – Many photovoltaic cells assembled together, creating panels or modules
  • Photovoltaic Arrays – Many photovoltaic modules assembled together
  • Renewable Energy Certificate – A kind of currency used to show that energy you generate comes from renewable sources.
  • Solar Radiation – The general term for electromagnetic radiation emitted from the sun. This radiation can be captured and harnessed into heat and electricity with photovoltaic cells.
  • Charge Controller – A device that limits the amount of energy that is added to a battery, preventing overcharging that decreases the life of a battery.

How does a solar cell work?

You’re already set on solar, but naturally have some questions. How does all of this stuff work anyway?

Solar panels are actually made up of smaller devices known as photovoltaic cells, or solar cells. Solar cells consist of two layers of silicon sandwiched between two metal strips that conduct the flow of electricity into the house.

Silicon by itself is not a good conductor of electricity, so each layer is “doped” with two separate chemicals. The top layer of silicon receives phosphorous, while the bottom layer is doped with boron.

With the addition of the chemicals, the top layer gains more electrons, while the bottom layer receives less. Once sunlight hits the solar cell, the electrons in both layers become excited, and are “knocked loose,” flowing freely in each layer. In this state of excitement, some of the electrons hit the metal strips on the outside of the cell, generating electricity.

This electricity transfers from the metal strips to wires that eventually wind their way into a home. With dozens of cells working in conjunction as panels, homeowners generate the electricity they need to turn on lights, watch television, and use computers.

In the next section, we’ll explore how the electricity moves from panels, through several other devices, and into the home as useable energy.

How does a solar panel create energy for my home?

Creating lasting, renewable energy for your home isn’t as simple as slapping a solar panel on your roof and waiting for the meter to run backward. Instead, solar installers create solar electric systems that include several pieces of equipment that allow energy to safely flow to the proper areas.

There are several different types of solar electric systems, but many typically include the following devices:

  • Solar panels
  • An inverter
  • Wiring
  • A support structure
Grid-Connected Systems

These solar electric systems are the most common, allowing you to supplement energy from the utility company with energy from your solar panels. With this system, you’ll power your house with solar energy during the daytime as you generate it, while using power from the utility company at night or during cloudy periods.

Energy travels from your panels through wiring as Direct Current (DC) energy. This energy is best stored in batteries, and must be turned into Alternating Current (AC) energy before you can use it in your home.

This conversion occurs in the Inverter, which will allow you to use the energy you’ve produced in outlets throughout your home. The inverter is a critical component of any solar system, taking the formally unusable DC energy and converting it into AC energy.

This AC energy is then wired through your electricity meter, where it is treated as if it came from any typical energy source. The major difference is that if you generate more energy than you’re using, you can actually watch your meter run backwards, as you contribute to the energy grid. By contributing to the energy grid, it’s actually possible to gain money back from the utility company each month through net metering programs.

Solar Electric System with Battery Backup

Instead of relying on utility companies during cloudy days or dark nights, people with solar batteries can store unused solar energy over a period of time. With a battery attached to their solar system, people can last longer without using grid-based power sources.

Systems that have batteries typically involve the same devices as normal grid-connected systems, with the addition of a battery and charge controller. Charge controllers ensure your battery does not become overcharged, which can degrade the battery over time and lead to inefficiencies.

With the addition of a battery, you have the ability to live completely off the grid in some cases. Living completely off the grid requires many batteries, and not many homeowners choose this option. However, many do choose to retain their grid connection even with batteries, giving them a backup in case power is low.

What do I need to consider when buying solar panels?

Most solar panel installers do not manufacture their own panels, but offer several choices to consumers based on their specific needs. When you contact an installer, they’ll ask you about your energy needs and schedule an at-home consultation, allowing them to gauge your eligibility.

Those buying solar panels should pay attention to some of the following factors:

  • The Type of Solar Cell
  • Solar Efficiency rating
  • Roof Orientation and Shading
Types of Solar Cells

Not all solar panels are created equal. Actually, there are several different kinds you’ll be able to choose from when negotiating with installers. Depending on what your installer offers, you’ll have access to solar panels made from three main types of solar cells:

  • Monocrystalline Silicon Cells
  • Polycrystalline Silicon Cells
  • Thin Film Cells

Monocrystalline silicon cells are the most efficient kinds of solar cells, but also the most expensive. Monocrystalline cells are created from one single silicon crystal, and are usually cut into small wafers, then assembled into panels.

Polycrystalline silicon cells are the most common cells used in solar panels. Poly cells are less efficient than mono cells, but are also less expensive. Where the monocrystalline cell is cut from one large silicon crystal, polycrystalline cells are made up of many tiny crystals. You can identify polycrystalline panels from the geometric shapes within the cells.

Thin film panels are formed by coating a silicon mixture onto a flexible material, sacrificing efficiency for cost. While these panels are the cheapest to purchase, they require nearly twice as much space as poly and monocrystalline panels to produce the same amount of energy.

Solar Efficiency Rating

Years of technological research have created more effective solar cells, allowing us to convert more of the sun’s energy into electricity. A panel’s Solar Efficiency Rating refers to what percentage of solar energy absorbed is able to be converted into electricity (the previously mentioned process where electrons bounce between the silicon layers until some hit the metal strips).

Most residential solar panels typically offer between a 13% to 15% efficiency rating, but some companies have achieved higher. Most recently, SunPower Corp, a manufacturer of high efficiency solar cells, achieved an efficiency rating of 24.2%.

A panel’s efficiency can be impacted by a number of outside factors, including dust, dirt, and anything that could block light from hitting the solar cells. While solar panels generally require little maintenance, those are some of the first things you should check for if you notice a drop in efficiency.

Roof Orientation and Shade

In Colorado (and the rest of North America) the sun follows a southern path. This means that solar panels work best on south-facing roofs, with some systems losing efficiency even when facing southeast or southwest.

Aspects like roof tilt may require you to buy different mounting systems that allow you to position your panels in more efficient directions. The most common mounting systems for solar panels include ground mounts and roof mounts.

When even one solar cell on your panel is exposed to shade, it can lead to an up to 50% reduction in efficiency in that cell and surrounding cells in the panel. This means that wherever you install your solar panels, you must be aware of any trees, chimneys, or parts of the roof that could block sunlight during the day.