The PV System Design Review and Approval process applies to any type of photovoltaic system interconnected with the utility grid and provides a method for evaluating the complete system design and documentation package. Items evaluated include safety and code compliance of the overall design, individual components and their interactions with one another, and the completeness of the instructions, diagrams and schematics for the installation, operation and maintenance of the system. This review and approval procedure does not cover site-specific requirements or issues, nor do these approvals replace or exempt any requirements of electric utilities or local jurisdictional authorities such as permitting, inspections or utility interconnection agreements. When installing a grid-connected system, eventually you'll need to make contact with the local utility to arrange interconnection. Check Utility Interconnection for a list of utility contacts.

Importance to Florida Photovoltaic Buildings Program

FSEC's PV System Design Review and Approval process is a key element of the Florida Photovoltaic Buildings Program, with the primary objective of helping ensure the safety and quality of installed systems. All grid-connected photovoltaic systems installed under the Florida Photovoltaic Buildings Program must be approved by FSEC in order for program partners to receive rebate funds from the State of Florida. The system design review and approval process is closely tied to acceptance testing, in which the approved system documentation is used to verify that installed systems are consistent with the design documents provided by the rebate applicant.

System Classifications

The design review process focuses on two categories of photovoltaic systems: grid-connected and stand-alone. Two types of grid-connected photovoltaic systems are considered in this FSEC standard. These include grid-connected PV systems without battery storage, and grid-connected PV systems with battery storage. For the purposes of this document and the scope of the design review and approval process, the following is the intended definition of a grid-connected photovoltaic system:

" “An electrical power generating system that uses a photovoltaic (PV) array as the primary source of electricity generation, and is intended to operate synchronously and in parallel with the electric utility network. Such systems may also include battery storage, other generating sources, and may operate on site loads independent of the utility network during outages.” "

There are three types of stand-alone systems covered by this document. These include PV-powered water pumping systems, PV-powered lighting systems, and remote residential PV systems. A generic description of these PV systems follow.

 

Grid-Connected

PV Systems without Battery Storage

Grid-connected or utility-interactive PV systems are designed to operate in parallel with and interconnected to the electric utility grid. The primary component in grid-connected PV systems is the inverter, or power-conditioning unit (PCU). The PCU converts the DC power produced by the PV array into AC power consistent with the voltage and power quality requirements of the utility grid, and automatically stops supplying power to the grid when the utility grid is not energized. A bi-directional interface is made between the PV system AC output circuits and the electric utility network, typically at the on-site distribution panel or service entrance. This allows the AC power produced by the PV system to either supply on-site electrical loads, or to back feed the grid when the PV system output is greater than the on-site load demand. At night and during other periods when the electrical loads are greater than the PV system output, the balance of power required by the loads is received from the electric utility. When the utility grid is down, these systems automatically shut down and disconnect from the grid. This safety feature is required in all grid-connected PV systems, and ensures that the PV system will not continue to operate and feed back onto the utility grid when the grid is down for service or repair.

PV Systems with Battery Storage

Typically, these systems include a ground-mounted array. This type of system is extremely popular for homeowners and small businesses where backup power is required for critical loads such as refrigeration, water pumps, lighting and other necessities. Under normal circumstances, the system operates in a grid-connected mode, supplementing the on-site loads or sending excess power back onto the grid while keeping the battery fully charged. In the event the grid becomes de-energized, control circuitry in the inverter opens the connection with the utility through a bus transfer mechanism, and operates the inverter from the battery to supply power to the dedicated critical load circuits only. In this configuration, critical loads are typically supplied from a dedicated load sub panel.

Each of these systems can provide power to DC loads. With the incorporation of an inverter in the system, each can also supply AC loads. Unlike the grid-connected systems, these systems must generate all the power available to the loads. Thus, array sizing (and battery sizing where included) and load requirements are critical aspects of success in meeting the customer’s needs.

 

Stand Along Systems

PV-Powered Water Pumping Systems

Water pumping is a major application for PV systems. Typically, these systems include a ground-mounted array (with or without an optional mechanical tracking device), a pump controller, an inverter for AC pump motors, and the pump/motor assembly operating off either DC or AC. Water is pumped only during daylight hours and is usually stored in a water tank to cover periods of bad weather. Batteries banks also may be incorporated in these systems as well.

PV-Powered Lighting Systems

Photovoltaic-powered lighting systems are an option for providing area lighting and sign lighting in lieu of extending utility service. These systems are sold as packages including the array, batteries, battery enclosure, charge controller, lighting controller, light fixture, ballast and lamp. The systems are typically small – total module output is typically under 250 WSTC. The arrays are usually pole mounted or mounted to the sign structure and should be equipped with vandal resistant hardware. High-pressure sodium, low-pressure sodium, and fluorescent fixtures are popular choices for these lights. Protection of the batteries from significant temperature variations is an important installation issue with these systems. Enclosure provisions for the batteries should moderate any temperature excursions to extend the lifetime and capacity of the batteries.

Remote Residential PV Systems

Photovoltaic systems can power remote residences and other small facilities where utility power is not available or desired. These systems typically utilize a roof or ground mounted array, a battery charge controller, battery storage, and an inverter to supply 115 VAC, 60 Hz electrical service. These systems may also be supplied with an auxiliary source of power such as small wind generators and/or engine generators to meet electrical needs during periods of bad weather. These systems may also be configured as portable power generators, either skid or trailer mounted, and are complete packages with integrated components.