Solar energyMorten Vesterager Madsen
The global energy future is arguably the most important subject undertaken by the scientific community. Without energy, our society will not function. Without energy we cannot find or administer medicine to cure disease, we cannot purify water, drive our cars, operate computers, or even study at night. The current energy need is roughly $15 TW$ and with an increasing world population this number is destined to increase. Professor of Physics and Astronomy at Rice University and Nobel laureate Richard E. Smalley coined the term the "Terawatt Challenge" based on this future energy deficit. Smalley defines the “Terawatt Challenge” as the challenge to provide the technology for accomplishing our energy goals - an alternative that can act as a basis for energy prosperity in the 21st century, that is as enabling as oil and gas have been for the past century.http://cohesion.rice.edu/naturalsciences/smalley/emplibrary/120204%20mrs%20boston.pdf It seems inescapable that the world of the future must embrace alternative energies.
Today most of the energy consumed in the world is provided by fossil fuels.http://en.wikipedia.org/wiki/Fossil_fuel Even though the sources of fossil fuels can cover the energy consumption for many years to come, there are many good reasons to look for alternatives. Along with resource scarcity and inadequate supply CO2 pollution are strong arguments against fossil fuels.
Renewable resources including, wind, solar cells, solar thermal, geothermal, marine, and tides still represents a minor fraction of the overall primary energy supply at the present moment. With a total nameplate capacity of 93,957 MW as of the end of 2011 within Europe alone, wind is the leading alternative energy resource.http://www.ewea.org/fileadmin/ewea_documents/documents/publications/statistics/Stats_20 11.pdf Several countries have high levels of penetration, such as 25.9% of electricity production in Denmark (2011), 15.6% in Spain (2011), 12% in Ireland (2011) and 10.6% in Germany (2011).http://www.ewea.org/fileadmin/ewea_documents/documents/publications/statistics/Stats_20 11.pdf
In the future, it is imperative that a larger and larger share of the energy is supplied by alternative or renewable energy forms. Solar energy is an excellent choice for an environmentally friendly reliable energy source. Each day the Earth receives approx. $1.2 \cdot 10^5 TW$ from the sun. Compared to the current energy consumption on Earth (> 20 TW) the sun sufficiently delivers energy to meet our consumption many many times. To harness the energy from the sun, we must either use solar panels which use the solar energy to heat water or we must use solar cells which produce electricity directly from sunlight. In this chapter you can read more about solar cells and the three generations of solar cells.http://en.wikipedia.org/wiki/Solar_energy http://en.wikipedia.org/wiki/Photovoltaic_effect