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  rev. 2009-10-22        

Existing Conditions

Photo Voltaic (PV) panels convert solar energy directly into electricity.  The electricity can then be coupled to the building’s electrical distribution, where it can be used within the building or sold back to the utility.

This building has a relatively large roof area with a clear exposure to the Eastern, Southern and Western skies.

Retrofit Conditions

Under the standard offer contract, the PV connection is upstream from the building, and consumption patterns are not affected, such as peak load shaving.  Net metering is only $0.11/kWh, but there are less costs associated with administration, more benefits from peak load shaving, and more potential for battery storage.

Further Benefits

The Ontario Power Authority will buy back electricity generated by PV cells for $0.802/kWh under their “Feed In Tariff” contract.  At this rate, the Return on Investment for a typical system are 12-15 years.  inverters and panels have warranties for 10-25 years respectively.  Domestic Content issues restrict the equipment, labour and design. The payback for this opportunity is greater than 20 years.

There are other benefits to the community, province and country, however.  These benefits include reduced smog, reduced summer peak grid load, economic development and environmental leadership.  We recommend installing 10 kW of panels to participate in the microFIT Program for ~$125,000

Application Details

A typical PV system is connected to a grid tied inverter, and the range of voltage produced must remain within the inverter's acceptable range (approximately 250 volts dc).

If the grid fails, the inverter measures the change in impedance, and disconnects itself until it senses the normal conditions again.  This is called Anti-Islanding.

Complex inverters, such as the Xantrex XW or OutBack offer an automated ability to integrate other systems, such as batteries, generators, and scheduled peak load shaving for unique applications.

The optimal slope of a panel is equal to the site's latitude.  A steeper tilt favors the winter, while a shallower slope favors the summer.

Issues and Concerns

The building must be structurally able to handle the new weight load, as well as the added wind load.

The costs are usually $5/watt for the panels, and at least $10/watt installed - Usually $15-$20/watt.

There are regional issues surrounding distribution and administrative fees.

The Domestic Content Laws add a level or Red Tape.





Analysis of a photovoltaic system can be done using RETScreen modeling software.

On the start page, change the project type to 'Power' and the Technology to 'Photovoltaic'.  The 'Energy Model' tab directs you to the key inputs needed.


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