Solar Energy By Henry Mooers and Harrison White

Introduction l l Solar energy is clean and plentiful, it is also a renewable resource meaning it will never run out on earth. Solar energy can be harnessed and captured in many ways.

Vocabulary l l Passive solar heating: the process of trapping sunlight inside of a structure and using it to heat the structure Active solar heating: a process in which heated tubes of water are fanned so that the hot air can escape; this hot air is used for heating a building Photovoltaic cells- Solar cells that directly generate solar energy into electricity Thermal energy- energy from heat

Passive solar heating l l l Passive solar heating is the process off trapping sunlight inside of a structure. The trapped light is absorbed by various materials inside the building and is released as heat. The interior of a car becomes very hot due to passive solar heating. The light passes through the windshield, and is then absorbed by the seats and other materials in the car. The light energy is changed to heat energy and is given off by the seats. Because heat energy has a different wavelength than light, It cannot pass back through the windshield Houses use big windows facing the sunlight to utilize passive solar heating

Diagram of Passive solar heating

Active solar heating l l l Active solar heating is a process in which solar collectors harness the suns energy and use it to heat collecting tubes filled with liquid. This hot air is pumped to a central collection tank The hot water is transferred throughout the house in pipes Fans blow on these pipes pushing warm air out through a vent This warm air is pumped throughout the structure

Active solar heating system

Photovoltaic cells l l l Photovoltaic cells generate electricity directly from the sunlight by an electronic process that occurs by itself in some materials. These materials are called semiconductors These materials include a thin layer of silicon mixed with a small amount of metals. When sunlight hits the cell, a small flow of electrons is created To power a home, 5000 cells would be needed

Solar thermal energy system l l l in this system, huge mirrors reflect sunlight onto curved mirrors that reflect light into a central point on a collector The steam byproduct from this is used to power turbines that produce electricity A system like this is not in use anywhere yet

Nuclear Fusion l l l Stars like the sun produce energy by the nuclear fusion of hydrogen into helium at its core Since hydrogen atoms are so densely packed in the suns core, they stick together and fuse into helium atoms The energy byproduct from this fusion is radiated out from the core and into the solar system

Cons of solar energy Pros of solar energy l l l Free Unlimited supply No carbon dioxide is released from a solar heating system Solar cells last for 30 years Material for solar cellssilicon-is cheap and abundant l l Weather and time dependant Expensive installation The metals gallium and cadmium (used in cell production) are hard to find The processes used to make the cells produces chemicals that could pollute the water

Climate issues l l l Obviously, for solar power to work, there needs to be a sufficient supply of sun. Although it is possible for solar energy to be stored, if there is consistently no sun for long periods of time (I. e. monsoon season in Asia, or the northwestern United states), then solar energy will be inefficient Solar energy is weather dependant, making it unreliable In certain areas

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Quiz l l l What are Photovoltaic cells? Solar cells that directly generate solar energy into electricity Name one pro and one con of solar energy It is renewable, it is expensive Name the two elements mainly involved in nuclear fusion Hydrogen and helium