Sunlight, Electricity and Heat
The sun is basically just a ginormous nuclear reactor sitting out in space. The sun's nuclear reaction forces turn the atoms in its mass into photons, light energy particles that radiate out. These photons travel across space and strike the Earth as light and heat.
The sun's energy comes to us in a wide spectrum of wavelengths, from ultraviolet to infrared. The amount of sunlight that hits the Earth's surface is about 35,000 times more than the total amount of energy used by all humans. This solar radiation, and its interaction with various materials, is what enables us to generate power.
Turning Sunlight Into Power
There are four basic ways that sunlight interacts with matter:
Boiling water, for example, is just liquid whose electrons have been so excited by the transfer of energy from the burner that they move like crazy. Hot stuff burns you because the excess energy gets transferred into your skin, which is not equipped to absorb it.
In order to use the heat energy in sunlight, you have to change it into a usable form, and you have to physically move it from where it is collected. There are three ways with which heat can be moved:
Air / .02 Plastic / .6 Fabric / 2 Bricks / 25 Wood / 27 Steel / 59 Water / 62 Copper / 78
The two best materials for storing and moving heat are water and copper. Water is cheap, but it doesn't absorb heat from light because it's highly transparent. It can, however, retain and store heat transferred to it from a different collector material. The material most commonly used in solar heat collectors is copper painted black.
Photovoltaic Cells Turn Sunlight Into Electricity
Photovoltaic (PV) cells are two layers (positive and negative) of purified silicon making a semiconductor sandwich. The most common example of a semiconductor is the transistor, which is found in all modern electronic components.
When you hook a closed electric circuit to your PV cell, by, say, connecting a lightbulb, you create the conditions for electricity to flow.
When the photons from the sun strike the electron-rich N (negative) silicon layer surface, they cause some of those electrons to break free from their atoms, leaving holes behind. If the electrons are close enough to the P (positive) layer, they can jump across the barrier and try to fill holes in the atoms in that layer.
The resulting electrical imbalance encourages the electrons to flow through the circuit (lighting up your bulb along the way) and back to the N layer. This electrical current is a direct result of the action of the solar radiation (photons) interacting with the physical properties of your PV cell.
A PV array is just a whole bunch of cells hooked up together. There's all kinds of stuff in a solar array system to keep you safe from getting zapped, convert your current from DC to AC (which most homes and appliances use), and store what you don't use right away for later.
In its simplest, most fundamental form, every solar energy system is basically just about efficiently harnessing the action of photon-excited electrons as they jump from one material to the next.
Isn't science fun? :)
The sun is basically just a ginormous nuclear reactor sitting out in space. The sun's nuclear reaction forces turn the atoms in its mass into photons, light energy particles that radiate out. These photons travel across space and strike the Earth as light and heat.
The sun's energy comes to us in a wide spectrum of wavelengths, from ultraviolet to infrared. The amount of sunlight that hits the Earth's surface is about 35,000 times more than the total amount of energy used by all humans. This solar radiation, and its interaction with various materials, is what enables us to generate power.
Turning Sunlight Into Power
There are four basic ways that sunlight interacts with matter:
- Absorption - the energy in a photon is absorbed by the material and changed into a different form
- Transmission - the energy goes through a material without changing form or losing power
- Scattering - the energy splits up into different wavelengths with different properties, and changes direction. Rainbows are the most well-know example of scattering
- Reflection - the energy changes direction without changing properties. Mirrors are reflectors.
Boiling water, for example, is just liquid whose electrons have been so excited by the transfer of energy from the burner that they move like crazy. Hot stuff burns you because the excess energy gets transferred into your skin, which is not equipped to absorb it.
In order to use the heat energy in sunlight, you have to change it into a usable form, and you have to physically move it from where it is collected. There are three ways with which heat can be moved:
- Conduction - the heat energy itself moves from one molecule to another, while the molecules stay in place. Heat moves from a hotter surface to a cooler surface.
- Convection - the heat energy moves from a fixed material to a liquid material in contact with the fixed material's surface. Convection also happens as the heat energy is moved along with the molecules travelling within the fluid itself. The heat energy makes the hotter liquid molecules rise, while gravity pulls the colder molecules down.
- Radiation - All fire emits infrared radiation, and the sun is the biggest fireball of all.
- Convert solar radiation into heat as efficiently as possible - a black surface is the most efficient heat collector of all, so the surface of your heat transfer devices will be dark.
- Transfer the collected heat energy into a medium that is easily used - the simplest heat transfer medium is liquid. Running water through a black metal pipe will take the heat absorbed by the surface and transfer it directly to the water. Putting on a tea kettle transfers energy from the burner through the pan and into the water.
- Prevent heat loss through good insulation - you can generate heat all day, but what good will it do you if the cold air just transfers the heat right back out of your medium? Air inside a closed house retains heat, but open the windows and you'll need a sweater.
- Store enough heat - the medium needs to have an intrinsically high heat capacity. That means that the physical structure of the materials you use have to be able to retain the energy that is transferred into them. Different materials have different physical properties and energy retention capabilities.
Air / .02 Plastic / .6 Fabric / 2 Bricks / 25 Wood / 27 Steel / 59 Water / 62 Copper / 78
The two best materials for storing and moving heat are water and copper. Water is cheap, but it doesn't absorb heat from light because it's highly transparent. It can, however, retain and store heat transferred to it from a different collector material. The material most commonly used in solar heat collectors is copper painted black.
Photovoltaic Cells Turn Sunlight Into Electricity
Photovoltaic (PV) cells are two layers (positive and negative) of purified silicon making a semiconductor sandwich. The most common example of a semiconductor is the transistor, which is found in all modern electronic components.
When you hook a closed electric circuit to your PV cell, by, say, connecting a lightbulb, you create the conditions for electricity to flow.
When the photons from the sun strike the electron-rich N (negative) silicon layer surface, they cause some of those electrons to break free from their atoms, leaving holes behind. If the electrons are close enough to the P (positive) layer, they can jump across the barrier and try to fill holes in the atoms in that layer.
The resulting electrical imbalance encourages the electrons to flow through the circuit (lighting up your bulb along the way) and back to the N layer. This electrical current is a direct result of the action of the solar radiation (photons) interacting with the physical properties of your PV cell.
A PV array is just a whole bunch of cells hooked up together. There's all kinds of stuff in a solar array system to keep you safe from getting zapped, convert your current from DC to AC (which most homes and appliances use), and store what you don't use right away for later.
In its simplest, most fundamental form, every solar energy system is basically just about efficiently harnessing the action of photon-excited electrons as they jump from one material to the next.
Isn't science fun? :)
You can find all kinds of great information on home solar energy systems at HomePowerCheap.com
Erick Mcguire writes regularly on renewable energy. He hopes you find this article useful and encourages you to use all the resources at http://www.HomePowerCheap.com
Erick Mcguire writes regularly on renewable energy. He hopes you find this article useful and encourages you to use all the resources at http://www.HomePowerCheap.com
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