The power and importance of the sun.
Energy from the sun is powerful and useful. People harness the sun’s energy in many ways, from growing plants for food to installing solar panels for electricity generation. Students will see what happens when a plant is deprived of light. While investigating the power of the sun, students will discuss methods of protecting themselves from the sun's harmful ultraviolet radiation. They will explore solar thermal energy by examining a radiometer, playing with a solar UFO and creating solar ovens. They will use photovoltaic cells to power small motors.
Students will be able to:
- identify the sun as the main source of the earth's energy
- identify methods of protecting themselves from harmful solar radiation
- demonstrate ways to convert solar energy into thermal energy and mechanical energy
Every second, the sun gives off more energy than humans have used in all of history. Only about one billionth of the sun’s energy ever reaches the earth (174 petawatts (PW) at the upper atmosphere). Approximately 30% of this energy is directly reflected back into space. The rest is absorbed by clouds, oceans and land masses. Solar energy is electromagnetic radiation (including infrared, visible and ultraviolet light) released by thermonuclear reactions in the core of the sun.
With a few exceptions (e.g. nuclear energy, geothermal energy), solar energy is the source of all energy used by humans. Indirect forms include hydroelectricity, ocean thermal energy, tidal energy and wind energy. The sun also powers the process of photosynthesis, the original source of the energy contained in biomass, peat, coal and petroleum (oil and gas). Usually, however, the term solar energy refers to the portion of the sun's radiant energy harnessed directly, such as through solar panels.
Solar technologies include active and passive solar techniques. Active techniques include things such as using photovoltaic panels and solar thermal collectors to convert sunlight into useful outputs. Passive techniques include things such as orienting a building to the sun and designing spaces that naturally circulate air.
Solar power is the conversion of sunlight into electricity. Sunlight can be converted directly into electricity using photovoltaics. It can also be converted indirectly with concentrating solar power (CSP) systems. CSPs normally focus the sun's energy to boil water and create steam which is then used to provide power to a generator. Photovoltaics were initially used to power small and medium-sized applications, from the calculator powered by a single solar cell to off-grid homes powered by a photovoltaic array.
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