Download “Renewable energy sources”

“Renewable energy sources”
Conventional energy sources based on oil, coal, and natural gas have proven to be highly effective
drivers of economic progress, but at the same time damaging to the environment and to human
health. Furthermore, they tend to be cyclical in nature, due to the effects of oligopoly in
production and distribution.
Renewable energy is generally defined as energy that is collected from resources which are
naturally replenished on a human timescale, such as sunlight, wind, tides, waves, and geothermal
heat. Renewable energy flows involve natural phenomena such as sunlight, wind, tides, plant
growth, and geothermal heat, as the International Energy Agency explains:
“Renewable energy is derived from natural processes that are replenished constantly. In its
various forms, it derives directly from the sun, or from heat generated deep within the earth.
Included in the definition is electricity and heat generated from solar, wind, ocean, hydropower,
biomass, geothermal resources, and biofuels and hydrogen derived from renewable resources”.
Based on REN21's 2014 report, renewables contributed 19% to humans' global energy
consumption and 22% to their generation of electricity in 2012 and 2013, respectively.
At the national level, at least 30 nations around the world already have renewable energy
contributing more than 20 percent of energy supply. National renewable energy markets are
projected to continue to grow strongly in the coming decade and beyond.[8] Some places and at
least two countries, Iceland and Norway generate all their electricity using renewable energy
already, and many other countries have the set a goal to reach 100% renewable energy in the
future. For example, in Denmark the government decided to switch the total energy supply
(electricity, mobility and heating/cooling) to 100% renewable energy by 2050.
Wind Power
Wind is a form of solar energy: winds are caused by the uneven heating of the atmosphere by the
sun, the irregularities of the earth's surface, and rotation of the earth. Wind flow patterns are
modified by the earth's terrain, bodies of water, and vegetative cover. This wind flow, or motion
energy, when "harvested" by modern wind turbines, can be used to generate electricity.
The terms "wind energy" or "wind power" describe the process by which the wind is used to
generate mechanical power or electricity. Wind turbines convert the kinetic energy in the wind
into mechanical power. This mechanical power can be used for specific tasks (such as grinding
grain or pumping water) or a generator can convert this mechanical power into electricity to
power homes, businesses, schools, and the like.
Wind turbines turn in the moving air and power an electric generator that supplies an electric
current. Simply stated, a wind turbine is the opposite of a fan: instead of using electricity to make
wind, like a fan, wind turbines use wind to make electricity. The wind turns the blades, which spin
a shaft, which connects to a generator and makes electricity.
Solar Power
Solar power is the conversion of sunlight into electricity, either directly using photovoltaics (PV), or
indirectly using concentrated solar power (CSP). Photovoltaics convert light into an electric current
using the photovoltaic effect. Concentrated solar power systems use lenses or mirrors and
tracking systems to focus a large area of sunlight into a small beam.
A solar cell, or photovoltaic cell, is an electrical device that converts the energy of light directly
into electricity by the photovoltaic effect, which is a physical and chemical phenomenon: it is a
form of photoelectric cell, defined as a device whose electrical characteristics, such as current,
voltage, or resistance, vary when exposed to light. Solar cells are the building blocks of
photovoltaic modules, otherwise known as solar panels. The array of a photovoltaic power system,
or PV system, produces direct current (DC) power which fluctuates with the sunlight's intensity.
For practical use this usually requires conversion to certain desired voltages or alternating current
(AC), through the use of inverters.
Concentrated solar power (CSP), also called "concentrated
solar thermal", uses lenses or mirrors and tracking systems
to focus a large area of sunlight into a small beam.
Contrary to photovoltaics, which converts light directly into
electricity, CSP uses the heat of the sun's radiation to
generate electricity from conventional steam-driven
turbines.
A wide range of concentrating technologies exists: among
the best known are the parabolic trough, the compact
linear Fresnel reflector, the Stirling dish and the solar power tower.
Hydropower
Hydropower is using water to power machinery or make electricity. Water constantly moves
through a vast global cycle, evaporation from lakes and oceans, forming clouds, precipitation as
rain or snow, then flowing back down
to the ocean. The energy of this water
cycle, which is driven by the sun, can
be tapped to produce electricity or for
mechanical tasks. Hydropower uses a
fuel, water, that is not reduced or used
up in the process. Because the water
cycle is an endless, constantly
recharging system, hydropower is
considered a renewable energy.
When flowing water is captured and
turned into electricity, it is called
hydroelectric power or hydropower. There are several types of hydroelectric facilities; they are all
powered by the kinetic energy of flowing water as it moves downstream.
Turbines and generators convert the energy into electricity, which is then fed into the electrical
grid to be used in homes, businesses, and by industry.
References:
https://en.wikipedia.org/wiki/Renewable_energy
http://windeis.anl.gov/guide/basics/
https://en.wikipedia.org/wiki/Solar_power#Photovoltaics
http://energy.gov/eere/water/how-hydropower-works