Photovoltaic Energy

Passive Solar Energy
August 19, 2017
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August 19, 2017
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Photovoltaic Energy

Advantages of Solar Energy
Solar energy is a renewable resource that is environmentally friendly. Unlike fossil fuels, solar energy is available just about everywhere on earth. And this source of energy is free, immune to rising energy prices. Solar energy can be used in many ways – to provide heat, lighting, mechanical power and electricity.

Photovoltaic Energy
Sunlight is converted to electricity using photovoltaic or solar cells. Photovoltaic (PV) cells are semiconductor devices, usually made of silicon, which contain no liquids, corrosive chemicals or moving parts. They produce electricity as long as light shines on them, they require little maintenance, do not pollute and they operate silently, making photovoltaic energy the cleanest and safest method of power generation.

Photovoltaic cells and modules
Photovoltaic cells come in many sizes, but most are 10 cm by 10 cm and generate about half a volt of electricity. PV cells are bundled together in modules or panels to produce higher voltages and increased power. A 12-volt module, for example, depending on its power output, could have 30 to 40 PV cells. A module producing 50 watts of power measures approximately 40 cm by 100 cm. PV panels are not highly efficient, converting only 12 to 15 per cent of the sun�s light into electricity, but laboratory prototypes are reaching 30 per cent efficiency.

PV modules generate direct current (DC), the kind of electricity produced by batteries. Although incandescent lights can operate on DC, most electric devices require 120-volt alternating current (AC) as supplied by utilities. A device known as an inverter converts DC to AC current. Inverters vary in size and in the quality of electricity they supply. Less expensive inverters are suitable for simple loads, such as lights and water pumps, but models with good quality waveform output are needed to power electronic devices such as TVs, stereos, microwave ovens and computers.

Sizing a PV System
PV modules produce electricity only when sunlight shines on them. When sizing a stand-alone PV system, the energy output of the PV panels and the storage capacity of the batteries should be high enough to operate devices at night and on cloudy days when little sunlight is available. To determine the amount of energy you need, multiply an electrical device�s power in watts by the number of hours a day the device will be used. For example, a 17-watt fluorescent light lit for 18 hours a day uses 306 watt-hours (or 0.306 kilowatt-hours) of electricity. To get total power use, do this calculation for each electric device and add the results. The PV system should supply at least as many kilowatt-hours (under a variety of lighting conditions) as your total electric needs. When sizing your PV system you should also consider the ability of your system to expand to meet any unexpected demands, such as the purchase of a new appliance, computer etc. PV systems can power any electric device but they are not suitable for water heating or other heat related appliances. A solar heater can heat water more quickly and efficiently than an electric water heater powered by PV panels. Solar heaters convert up to 60 per cent of the sun�s energy into heat whereas PV cells are far less efficient and convert only 12 to 15 per cent of the sun�s energy into electricity.

Cost of PV System
When examining costs of PV systems, a consumer must consider the following factors: that PV modules are technically well proven, have an expected service time of 30 years and as a modular system they have the potential to grow from a milliwatt system to a megawatt system, which allows the flexibility needed to meet increasing energy demands. PV is a cost-effective and viable option in many remote areas where utilities may charge $18,000-$60,000 a kilometre (depending on terrain) to run a power line to an unserviced area. Basic costs, beginning with a portable PV unit with a 50-watt solar panel, low-power inverter and battery, are about $700 and can operate three high-efficiency lights, a small TV and a water pump. A more powerful PV system that produces 600 watts and operates several lights, a TV, stereo, microwave oven and water pump – but not at the same time – costs about $8,000. New production techniques and applications combined with lowering prices for photovoltaics should increase the acceptance of this environmentally friendly technology.

Photovoltaics in Northern Climates
In the northern areas of Canada, where there is both grid and remote/off-grid electricity demands, there is a limited supply of viable energy sources. Traditionally, electricity in the north has been provided by diesel generation, which is costly, owing to high fuel transportation costs and, if a spill occurs, devastating to the local environment. It is in these areas that PV, a clean and reliable electricity source, has a great deal of potential. PV systems in northern locations must be technologically adaptable to withstand extreme weather conditions and to provide electricity when there are large seasonal fluctuations in solar radiation.

Photovoltaics in Developing Countries
In the developing world, where there is abundant sunlight and a large rural population without the proper infrastructure to develop an electrical grid, PV is seen as very attractive option because of its modular features, its ability to generate electricity at the actual point of use, its low maintenance requirements and its non-polluting technologies. PV is also important to rural health clinics in developing countries. These clinics require electricity for lighting, vaccine refrigeration and water pumping and purification. PV has proven to be a reliable system for these isolated clinics.


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