|Written By: Barbara Lang
MIPEC Solar Inc.
|Originally Published in the September 1988
issue of The Outfitter Magazine.
What is photovoltaic?
Photovoltaic is the direct conversion of light into electricity by means of solar cells.
Photovoltaic systems provide electricity in areas where there are no power lines or when power line service is interrupted. They put an end to the dependence on gasoline and diesel generators and oil or gas lighting.
Photovoltaic power generation is completely silent and heat free. There are no by-products and thus there is no impact on the environment. Once installed, there are no operating costs. The only fuel is the sun.
Not to be confused with passive solar heating systems, photovoltaic power supply systems are lightweight and can be carried wherever needed.
A few typical applications are:
Mobile homes and campers
Sailboats and yachts
Cellular telephone installations
Back-up power supply alarm and medical care systems
A variety of uses for remote operations in the forestry, agricultural and transportation industries.
How does it work?
The basic system consists of three components:
Consisting of one or more weather-proof panels exposed to sunlight, the solar module is actually a series of interconnected solar cells cut from a block of extremely pure silicon. These cells, which are the basis for the photovoltaic effect, create electricity which is then stored in the battery.
The heavy-duty battery stores the electricity generated by the solar module so that the power is available even when the sun is no longer shining.
The charge regulator is a compact, fully automatic switching device which controls the flow of power from the solar module to the battery (preventing overcharging) and from the battery to the connected appliances (preventing over discharge).
Which appliances can be connected?
The solar panels operate on a nominal 12 volt DC current. While it is possible to convert the DC current to 110 volt AC, the highest efficiency is maintained by connecting the system to 12 volt appliances. Modern lighting fixtures, refrigerators, water pumps, ventilators, radio-cassette players and television sets which operate on 12 volt DC are readily available at about the same cost as 110 volt DC appliances. Alarm systems and cellular phones are ideally served by solar power since they are basically 12 volt DC devices.
What does it cost?
Photovoltaic systems are not expensive, especially when compared to the alternatives. Due to the modular design of the system, you can start with a single panel set and expand it as your needs increase. Your basic system will end up costing you less than the purchase, fuel and maintenance costs of a gasoline generator.
How to determine the required energy supply (number of panels)
One SM 55 panel generates an average of 130 to 200 WH per day during the summer months in various parts of Canada, even in the northern regions. For example, a one-panel installation in the vicinity of Montreal will produce on average 200 WH/day during the summer months.
Your energy requirement can easily be determined by multiplying the load demand of each appliance by the expected number of service hours in a 24-hour period, e.g. one 8 W lamp switched on for 2 hours requires 16 WH. 12 V appliances are normally designed for low energy consumption (e.g. lights 10 to 13 WH, alarm system 0.6 WH, radio 15 WH, refrigerator 10 WH, portable colour television 40 WH, water pump 100 WH).
The total watt-hours for all the appliances you expect to use during a 24-hour period is then compared to the average daily power generation figure for your location. This will tell you how many panels you need. If your system is used on weekends only, consumption may be allowed to exceed the daily power generation figure considerably, provided the battery is allowed to recharge during the week.
MIPEC SOLAR offers a number of low consumption lighting fixtures and appliances which enable you to maximize the efficiency of your system.