• Introduction
• Getting Started
• Components
• Rebates
• System Planning
• Solar Resources
• Wind Resources
• Energy vs. Cost
• Buyer's Guide
• Single-Sided PV
• Double-Sided PV
• Wind Turbines
• Grid-Tie Inverters
• Installation Guide
• Advanced Tech.
• Glossary
• Links

Getting Started - Components

Photovoltaic modules

Photovoltaic modules, or solar panels for short, are a direct means to convert sunlight to electricity. They should not be confused with solar hot water heaters, which convert sunlight to thermal energy. These flat panels, or modules as they are termed, are generally mounted on south-facing roofs in order to absorb the optimal amount of light. They may also be mounted on a "tracker", a device not unlike a sunflower in its manner of following the sun throughout the day. A typical module measures anywhere from 1x3 feet to 3x5 feet. Modules always generate direct current, though some new models are sold with inverters pre-mounted to output alternating current. Most locations in the United States will have four to six hours of near-full sunlight each day. Solar installations will generally use one to sixty modules (which have ~36-144 cells each). It is a good idea to plan for gradual system expansion for solar installations because the up-front investment can become substantial, though not out-of-line for typical home construction upgrades.

Wind turbines

Wind turbines, also known as wind generators, are a secondary option to photovoltaic panels. They are typically more costly to install but can produce more power per ground area provided they are high enough. Typically two or three blades turn a motor, operated in reverse, to put power back onto the line in a similar fashion to photovoltaics. Wind availability varies greatly across the United States; the best areas are those east of the Rocky Mountains. Some wind generators are sold with inverters inside, while others require external units. Typical home installations use only one wind turbine (with or without solar panels).

Grid-tie or standalone inverters

These change the direct current from the modules or the alternating current from the turbine into a precise 60Hz alternating current, which for grid-tie inverters is synchronized to the utility. This may be 120V or 240V, but is typically the latter. 98% of homeowners choose grid-tie inverters because the utility is almost always available to soak up the power generated by the modules or turbine, yet it can still provide power to the home when the renewable source is not currently producing. (This setup is called net-metering.) Therefore this is the most cost-efficient option, but the renewable source will not be of any benefit during a power outage. Only a couple photovoltaic modules and wind turbines include an inverter inside, so generally a separate one must be purchased. Often installations will require multiple inverters. A list of available grid-tie inverters is on the Buyer's Guide page.

Accessories

Generally, mounting rails are required for solar modules if they are to be placed on a roof. These ensure the module frames are grounded, which is usually required by the National Electrical Code (see the Links page). Wiring is another necessity. Many modules use the MC/MC3 or MC4 connectors. These are single-conductor cables used to connect the module(s) to the inverter(s). They are designed so that there are only two connector polarities for both the sending and receiving end of the positive and negative leads. The sending positive is the same style as the receiving negative, and vice versa. In this way, the same extension cable can be used for both polarities, but is switched end-to-end to avoid accidentally reversing the polarity of the module. Junctions are also sold that enable the installer to put modules in parallel or series, depending on the requirements of the inverter. Lightning arrestors are advisable for both the DC and AC circuits. These clamp the lightning voltage at a level less dangerous to the system components. Finally, DC and AC disconnects may be required if the inverter does not already contain them. The Enphase line of inverters does not require DC disconnects by design, though they do require an AC disconnect since one is not built-in. The inverter data sheet should be consulted to see whether or not DC and AC disconnects are included. A list of NABCEP-certified installers (recommended by us and required for some rebates) can be found on the Links page.