Solar Power & How It Works
Solar Power Systems & Your Home
Photovoltaic System Overview
Photovoltaic (PV) systems are used to convert sunlight into electricity. They are a safe, reliable, low-maintenance source of solar electricity that produces no on-site pollution or emissions. PV systems incur few operating costs and are easy to install on most Canadian homes. PV systems fall into two main categories—off-grid and grid-connected. The “grid” refers to the local electric utility’s infrastructure that supplies electricity to homes and businesses. Off-grid systems are installed in remote locations where there is no utility grid available.
PV systems have been used effectively in Canada to provide power in remote locations for transport route signalling, navigational aids, remote homes, telecommunication, and remote sensing and monitoring. Internationally, utility grid-connected PV systems represent the majority of installations, growing at a rate of over 30% annually. In Canada, as of 2009, 90% of the capacity is in off-grid applications; however, the number of grid-connected systems continues to grow because many of the barriers to interconnection have been addressed through the adoption of harmonized standards and codes. In addition, provincial policies supporting grid interconnection of PV power have encouraged a number of building integrated PV applications throughout Canada.
With rising electricity costs, concerns with respect to the reliability of continuous service delivery and increased environmental awareness of homeowners, the demand for residential PV systems is increasing. This article aims to inform homeowners of what they need to consider before purchasing a system. The information presented will focus on grid-connected PV systems. To learn more about off-grid applications, consult CMHC’s Research Highlight fact sheet Energy Use Patterns in Off-Grid Houses.
PV system components
The most critical component of any PV system is the PV module, which is composed of a number of interconnected solar cells. PV modules are connected together into panels and arrays to meet various energy needs. The solar array is connected to an inverter that converts the Direct Current (DC) generated by the PV array into Alternating Current (AC) compatible with the electricity supplied from the grid. AC output from the inverter is connected to the home’s electrical panel or utility meter, depending on the configuration. Various AC and DC disconnects are installed to ensure safety when working on the systems.
Metering
There are two different types of metering arrangements that can be used, depending on the local utility. The first is net metering. In this configuration, the utility charges you for your net consumption of electricity. When you are producing more electricity than you are consuming, your meter will essentially run backwards providing you with a credit. If you have a large system and produce a net surplus of electricity over the course of a year, utilities generally do not currently pay you for the surplus. Instead, accounts are generally reset to zero after a given period, often on a given day every year.
The second metering arrangement is where the electricity generated by the PV system is measured by a separate utility meter. This metering configuration is used when the utility pays homeowners a different rate for electricity that is generated than what is taken from the grid. For example, in 2009, the Ontario provincial government started offering 20-year fixed price contracts paying homeowners $0.802 for every kilowatt-hour produced from rooftop systems of less than 10 kW1. These types of contracts, known as feed-in tariffs, are used to accelerate the adoption of renewable energy technologies and are discussed in more detail later.
Backup power
The system shuts down during power outages. In such a case, inverters are designed to sense the outage and automatically disconnect all power going to the utility meter as a safety requirement to protect utility service employees that may be working on the power lines. So even though you have a PV system, it would not be available during power outages. In order to have backup power, you need to add a battery bank. The whole domestic electrical load is too large to be entirely powered, but some inverters have the capability to continue powering an emergency sub-panel that can be used to provide power to critical loads (e.g. refrigerator, security systems, etc.) in the case of a power outage.
In addition to a battery bank, this configuration requires a charge controller that is able to effectively manage the batteries charging from the PV system, to ensure their optimal performance and extend their life expectancy. This system is more costly and loses some of the efficiency advantages of a battery-less system.
Contact your REALTOR at Coldwell Banker Vantage Realty for more tips and advice on how to integrate a solar power system in your home.
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