Types of Solar Power Systems

Switch to Solar offers several different types of commercial and residential solar electric systems, each suitable for different applications:

  • Grid-Tied Solar Energy Systems: provide a constant stream of electricity to your home or business through a combination of solar power and electricity purchased from your utility. These configurations are ideal when you’re looking for affordability and do not need emergency power.
  • Standalone Solar Power Systems: use solar energy to provide full power in areas that are not connected to the utility grid. These systems are ideal for supplying power when a utility connection or generator aren’t practical.
  • Grid-Tied/Battery Backup Solar Energy Systems: which provide a constant stream of electricity to your home or business by combining solar power, electricity purchased from your utility, and battery backups to ensure a constant supply of electricity regardless of any issues with the utility or insolation (the amount of sunlight your solar panels are receiving).

Grid-Tied Solar Energy Systems

A grid-tied solar energy system generates electricity only when the sun is out. If your solar panels generate more energy than you are currently using, the excess automatically flows back to the grid, and you are credited for the kilowatts you generate on your utility bill. If at any point your solar panels produce less electricity than you are using, you will draw energy from the grid and notice the difference.

If the utility grid goes down, your solar energy system will shut off to prevent utility workers from being exposed to back feeding from solar energy generation while they are working to repair the lines.

Configuration

A simple grid-tied solar energy system, without battery backup, consists of the solar panels (also called solar modules or photovoltaic/PV modules), the mounting system (typically a rail-based system for roofs) and the inverter(s). Balance of system (BOS) equipment includes the mounting and wiring systems that integrate the solar panels into your home or office’s structural and electrical systems.

The wiring systems contain disconnects for the DC and AC sides of the inverter, ground-fault protection, and overcurrent protection for the solar panels.

Many solar energy systems include a combiner box for fusing each solar panel source circuit, though some inverters include this fusing and combining function.

The DC-AC inverter converts the DC power from your solar panel array into standard AC power used by home appliances. Metering provides an indication of your solar energy system’s performance and may also indicate home energy usage. A utility switch may also be included, but that depends on your utility.

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Standalone Solar Power Systems

For those who are not connected to a utility grid, Switch to Solar offers stand-alone solar electric power systems. In this configuration, a bank of batteries stores excess electricity and provides power at night and on cloudy days.

Both the battery bank and solar panel arrays must be carefully designed in order to supply power when insolation (the amount of sunlight the solar panels receive) is low, especially for an extended period of time.

Direct-Couple System

The simplest standalone solar power system is a direct-coupled system, where the DC output of a solar panel or solar array is directly connected to a DC load that operates only during the daylight hours.

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Because there are no batteries in direct-coupled solar energy systems, the load only operates during sunlight hours. Therefore, this configuration is commonly used for ventilation fans and water pumps, which do not need constant power.

In some cases, an electric DC-DC converter called a maximum power point tracker (MPPT) is inserted between the solar panel array and the load to better utilize the solar array’s power output.

Matching the impedance of the electrical load to the photovoltaic array’s maximum power output is important for designing high-performing direct-coupled solar energy system.

Standalone Solar Power System with Battery Bank

Standalone solar energy systems that serve both DC and AC loads have battery banks that continue to supply electricity generated by your solar panels at night and cloudy days. A generator may also be added to create a hybrid system. The figures below show a diagram of a typical standalone solar energy system powering DC and AC loads, as well as how a typical photovoltaic hybrid system might be configured.

 

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Grid-Tied/Battery Backup Solar Energy System

A grid-tied/battery back-up solar power system is a hybrid of the grid-tied and stand-alone types. As the name suggests, this system is connected to the utility grid and has a battery bank, which allows it to provide power from solar when the grid is up and emergency power from both solar and batteries when the grid is down.

In the event of an outage, a central smart inverter disconnects from the main service panel, allowing critical loads to continue to be energized through solar and the battery backup without endangering utility personnel.

Configuration

In addition to the components listed for a grid-tied solar energy system without backup, this system may include some or all of the following:

  • Batteries and battery enclosures
  • Battery charge controller
  • Separate subpanel(s) for critical load circuits

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Battery

Deep-cycle batteries can be discharged and then recharged thousands of times. These batteries are rated in amp hours (ah) – usually at 20 hours or 100 hours. Simply stated, amp hours refers to the amount of current (in amps) that can be supplied by the battery over a period of hours. For example, a 350ah battery could supply 17.5 continuous amps over 20 hours or 35 continuous amps for 10 hours.

Charge Controller

A charge controller monitors the battery’s state-of-charge to insure that, when the battery needs charge-current, it gets it. It also insures the battery isn’t over-charged.

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