photovoltaic solar cells and solar energy systems for home usages mohammad anisuzzaman
TRANSCRIPT
Photovoltaic Solar Cells and Solar Energy Systems for Home
Usages
Mohammad Anisuzzaman
What are Photovoltaic Solar Cells?
• Photovoltaic cells, commonly known as solar cells, are semiconductor devices that convert sunlight directly into electricity.
• Efficiency range from a few percent to above 40%.
• Most cell materials are non-toxic and produce to greenhouse gas.
• Usage range from portable electronics to spaceships.
Types of Solar Cells• Silicon Solar Cells:
– Single Crystal Si Cells: Commonly used. Usual efficiency of 20%. Long lifetime (>20 yrs). Approaching the theoretical limit of 29%. Cost of production $2.48/watt.
– Poly Crystal Si Cells: Less expensive. Efficiency is usually less than 15%.
– Amorphous thin film Si Cell: thin non-crystalline Si layers are printed on a substrate. Lightweight and less expensive. Efficiency around 10%.
• Cadmium Telluride Thin Film Cells– Inexpensive to produce; US$1/watt reported. Best efficiency
reported is 16.5%. Popular for solar panel arrays.• Copper Indium Gallium Selenide Thin Film Cell:
– Efficiency around 20%. Manufacturing costs are higher that amorphous Si thin film cells, but dropping fast.
• Gallium Arsenide Multijunction Cells:– Maximum reported efficiency of 42.4%. Much more
expensive to produce. Limited to scientific and high cost commercial usage. Thin Film Cells
Polycrystalline Si Cell
Solar Panels
• A single solar cell has very limited output capacity, e.g. a single crystal Si cell output is about 0.5V
• Cells are joined in series and parallel to increase their output capacity, e.g. 36 sc-Si cells are connected to produce a ~24v module.
• Further increase in output capacity, require joining panels into solar arrays.
+
Cells
Panel
Array
Solar Panel System
In addition to the solar panel array, several other components are needed for a complete solar power system:
• Charge controller: prevent overcharging of the batteries
• Batteries: power storage• Inverter: DC to AC
conversion for AC appliances • DC and AC safety switches• Optional AC generator
Cost: $6,000 - $10,000
System Wiring Diagram
Electricity Consumption
– Average household electricity usage in the United States is more that 600 kWH/month.
– Average household electricity usage in developing countries like Bangladesh and India is less than half of that in the US.
– Electricity usage can be reduced to 200 kWH or less per month by adopting energy conservation techniques and moderation.
– Such conservation policies can make a reasonably sized solar panel system enough for the energy need of an average household.
Example Home System
• A typical home may need about 200 AH/day of supply capacity from the photovoltaic (PV) system. (ignoring heavy equipments like microwave oven, air conditioners etc.)
• A typical 80 watt solar panel gives 5.5 A of current under direct sunlight.A system with 10 panels with 6 hours of sunlight per day gives
5.5 A x 8 x 6 Hr = 330 AH• This ensure that the batteries will be charging even when the
system is under full load.• With fifteen 105 AH Lead Acid batteries –
Total battery capacity: 105 AH x 15 = 1575 AH • This ensures that the system has adequate backup for multiple
days and still maintain a shallow discharge level required for long battery life.
Conclusion
• Solar cells are a very clean way to produce electricity, with no greenhouse gas emission over their lifetime.
• The initial cost of setup may be high, but their long lifespan results in payback typically in about 20 years.
• Over its estimated life a photovoltaic module will produce much more electricity then used in its production.
• A 100 W module will prevent the emission of over two tons of CO2 during its lifetime.
• With proper disposal of depleted batteries and old cells, impact on the environment from solar panels systems is minimal.