The Grid-Connected PV System


grid connected pv system

We all know that solar energy systems are beneficial, but there are a few things to think about when considering a grid-connected PV (photovoltaic) system.

Benefits of a Grid-Connected PV System

Off-the-grid renewable energy systems are able to completely power a home. However, connecting to the power grid can offer a wider variety of benefits.

One of the benefits is the ability to draw electricity from the utility company when solar power is not enough. Some power providers allow a net metering agreement by using a single meter to track the amount of excess electricity that is fed back to the utility company. The meter spins forward when you are using the grid and backward when your system is producing electricity.

You end up only paying the difference between what you produced and what you used. In addition, if you produce more than you use, the power company is required to pay you for what is being fed into the grid and used elsewhere. This can improve your return on investment.

What Do You Need for Your Grid-Connected PV System?

Sometimes additional equipment is needed to connect a PV system to the grid. This is called “balance of system”. The balance of system equipment includes the power conditioning equipment. This equipment matches the voltage and frequency powered by your system to that of the electricity flowing through the grid. Safety equipment prevents damage to the system or harm to people during lightning, power surges, malfunctioning equipment, etc. Meters and instrumentation allow you to monitor your PV system’s equipment.

Power providers have similar issues they face when connecting a system to the grid. Therefore, most providers have a common set of connection requirements. Grid connection requirements can vary, so before buying any specific equipment, it’s best to call your power provider and ask about the standards of compliance. Your PV contractor might be able to help you with this aspect of the installation as well. The connection requirements revolve around the issues of safety, power quality, contracts, metering, and rates.

Occasionally a power provider might not have a person assigned to deal with grid connection requests. In this case, you want to contact either your state utility consumer advocate group, state utilities commission, state energy office, or state consumer representation office.

Safety and Power Quality Issues

Along with the power conditioning equipment, power providers usually require disconnect switches. These switches allow the grid-connected PV system to be disconnected in case of a power outage or surge. This also prevents the grid from receiving electricity while repairmen are working on fixing the infrastructure.

Several organizations have attempted to address the issues of safety and quality by developing national guidelines for the manufacture, installation, and operation of a grid-connected PV system. These organizations include The Institute of Electrical and Electronics Engineers (IEEE), Underwriters Laboratories (UL), and the National Fire Protection Association. The IEEE is responsible for a standard which sets the technical requirements and tests needed for grid-connected operation. The UL has developed UL 1741, which certifies converters, inverters, output controllers and charge controllers for both off-grid and grid-connected PV systems. Finally, the National Electric Code, from the National Fire Protection Association, is the regionally adopted standard for wiring and electrical equipment.

Contractual Issues

When connecting a PV system to the grid, an interconnection agreement is usually signed between the homeowner and the power provider.

Most power providers require homeowners to carry liability insurance. Insurance protects the provider in case of an accident which results from operating the PV system.  Make sure that your policy covers the system, and be aware that some power providers require homeowners to release them from any responsibility in case of injury, loss or potential damage caused by your system. 

Some agreements may also require permitting fees, standby charges (to reimburse the costs of maintaining your solar system as an alternate power supply), engineering and inspection fees, and metering charges (in case a second meter is installed).

In addition to the requirements mentioned above, a power supplier might also ask for a considerable amount of paperwork to be completed.

Is Getting Connected to the Grid Worth It?

With a powerful enough system in the right climate, you might meet all of your energy needs off-grid. However, those setups can be rare. If you do own one, you can hook it up to the grid and sell excess electricity to the utility company. All in all, connecting your system to the grid is almost always the right move.The exceptions would be small systems that power only a part of your property (such as a stand-alone home solar kit that powers your toolshed).



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