What Do I Need To Know?
You've probably seen calculators with solar cells -- devices that never need batteries and in some cases, don't even have an off button. As long as there's enough light, they seem to work forever. You may also have seen larger solar panels, perhaps on emergency road signs, call boxes, buoys and even in parking lots to power the lights.
Although these larger panels aren't as common as solar-powered calculators, they're out there and not that hard to spot if you know where to look. In fact, photovoltaics -- which were once used almost exclusively in space, powering satellites' electrical systems as far back as 1958 -- are being used more and more in less exotic ways. The technology continues to pop up in new devices all the time, from sunglasses to electric vehicle charging stations.
The hope for a "solar revolution" has been floating around for decades -- the idea that one day we'll all use free electricity from the sun. This is a seductive promise, because on a bright, sunny day, the sun's rays give off approximately 1,000 watts of energy per square meter of the planet's surface. If we could collect all of that energy, we could easily power our homes and offices for free.
In this article, we will examine solar cells to learn how they convert the sun's energy directly into electricity. In the process, you will learn why we're getting closer to using the sun's energy on a daily basis, and why we still have more research to do before the process becomes cost-effective.
The sun—that power plant in the sky—bathes Earth in ample energy to fulfill all the world's power needs many times over. It doesn't give off carbon dioxide emissions. It won't run out. And it's free.
So how on Earth can people turn this bounty of sunbeams into useful electricity?
The sun's light (and all light) contains energy. Usually, when light hits an object the energy turns into heat, like the warmth you feel while sitting in the sun. But when light hits certain materials the energy turns into an electrical current instead, which we can then harness for power.
Old-school solar technology uses large crystals made out of silicon, which produces an electrical current when struck by light. Silicon can do this because the electrons in the crystal get up and move when exposed to light instead of just jiggling in place to make heat. The silicon turns a good portion of light energy into electricity, but it is expensive because big crystals are hard to grow.
Newer materials use smaller, cheaper crystals, such as copper-indium-gallium-selenide, that can be shaped into flexible films. This "thin-film" solar technology, however, is not as good as silicon at turning light into electricity.
Right now, solar energy only accounts for a tiny portion of the U.S.'s total electricity generation, because it is more expensive than alternatives like cheap but highly polluting coal. Solar power is about five times as expensive as what people pay for the current that comes out of the outlets.
In order to have a hope of replacing fossil fuels, scientists need to develop materials that can be easily mass-produced and convert enough sunlight to electricity to be worth the investment.
We asked Paul Alivisatos, deputy laboratory director at Lawrence Berkeley National Laboratory in California and a leader of their Helios solar energy research project, to explain how people capture energy from sunlight and how we can do it better.
[An edited transcript of the interview follows.]
What is a solar cell?
A solar cell is a device people can make that takes the energy of sunlight and converts it into electricity.
How does a solar cell turn sunlight into electricity?
In a crystal, the bonds [between silicon atoms] are made of electrons that are shared between all of the atoms of the crystal. The light gets absorbed, and one of the electrons that's in one of the bonds gets excited up to a higher energy level and can move around more freely than when it was bound. That electron can then move around the crystal freely, and we can get a current.
Imagine that you have a ledge, like a shelf on the wall, and you take a ball and you throw it up on that ledge. That's like promoting an electron to a higher energy level, and it can't fall down. A photon [packet of light energy] comes in, and it bumps up the electron onto the ledge [representing the higher energy level] and it stays there until we can come and collect the energy [by using the electricity].
What's the biggest difference between how a plant captures light energy and how we do it with solar cells?
We wish we could do what plants do because plants absorb the light, and [they use] that electron to change a chemical bond inside the plant to actually make fuel.
Could you do artificial photosynthesis and emulate a plant?
We would love to be able to make a solar cell that instead of making electricity makes fuel. That would be a very big advance. It's a very active topic right now among researchers, but it's hard to predict when we will be able to use it.
Although these larger panels aren't as common as solar-powered calculators, they're out there and not that hard to spot if you know where to look. In fact, photovoltaics -- which were once used almost exclusively in space, powering satellites' electrical systems as far back as 1958 -- are being used more and more in less exotic ways. The technology continues to pop up in new devices all the time, from sunglasses to electric vehicle charging stations.
The hope for a "solar revolution" has been floating around for decades -- the idea that one day we'll all use free electricity from the sun. This is a seductive promise, because on a bright, sunny day, the sun's rays give off approximately 1,000 watts of energy per square meter of the planet's surface. If we could collect all of that energy, we could easily power our homes and offices for free.
In this article, we will examine solar cells to learn how they convert the sun's energy directly into electricity. In the process, you will learn why we're getting closer to using the sun's energy on a daily basis, and why we still have more research to do before the process becomes cost-effective.
The sun—that power plant in the sky—bathes Earth in ample energy to fulfill all the world's power needs many times over. It doesn't give off carbon dioxide emissions. It won't run out. And it's free.
So how on Earth can people turn this bounty of sunbeams into useful electricity?
The sun's light (and all light) contains energy. Usually, when light hits an object the energy turns into heat, like the warmth you feel while sitting in the sun. But when light hits certain materials the energy turns into an electrical current instead, which we can then harness for power.
Old-school solar technology uses large crystals made out of silicon, which produces an electrical current when struck by light. Silicon can do this because the electrons in the crystal get up and move when exposed to light instead of just jiggling in place to make heat. The silicon turns a good portion of light energy into electricity, but it is expensive because big crystals are hard to grow.
Newer materials use smaller, cheaper crystals, such as copper-indium-gallium-selenide, that can be shaped into flexible films. This "thin-film" solar technology, however, is not as good as silicon at turning light into electricity.
Right now, solar energy only accounts for a tiny portion of the U.S.'s total electricity generation, because it is more expensive than alternatives like cheap but highly polluting coal. Solar power is about five times as expensive as what people pay for the current that comes out of the outlets.
In order to have a hope of replacing fossil fuels, scientists need to develop materials that can be easily mass-produced and convert enough sunlight to electricity to be worth the investment.
We asked Paul Alivisatos, deputy laboratory director at Lawrence Berkeley National Laboratory in California and a leader of their Helios solar energy research project, to explain how people capture energy from sunlight and how we can do it better.
[An edited transcript of the interview follows.]
What is a solar cell?
A solar cell is a device people can make that takes the energy of sunlight and converts it into electricity.
How does a solar cell turn sunlight into electricity?
In a crystal, the bonds [between silicon atoms] are made of electrons that are shared between all of the atoms of the crystal. The light gets absorbed, and one of the electrons that's in one of the bonds gets excited up to a higher energy level and can move around more freely than when it was bound. That electron can then move around the crystal freely, and we can get a current.
Imagine that you have a ledge, like a shelf on the wall, and you take a ball and you throw it up on that ledge. That's like promoting an electron to a higher energy level, and it can't fall down. A photon [packet of light energy] comes in, and it bumps up the electron onto the ledge [representing the higher energy level] and it stays there until we can come and collect the energy [by using the electricity].
What's the biggest difference between how a plant captures light energy and how we do it with solar cells?
We wish we could do what plants do because plants absorb the light, and [they use] that electron to change a chemical bond inside the plant to actually make fuel.
Could you do artificial photosynthesis and emulate a plant?
We would love to be able to make a solar cell that instead of making electricity makes fuel. That would be a very big advance. It's a very active topic right now among researchers, but it's hard to predict when we will be able to use it.
Solar PV Basics - How Solar Panels Work & Types of Solar Panels
How does solar power work? Here’s a quick guide to the steps that it takes to turn sunlight into electricity using solar panels:
High electricity bill? We can help.At One Block Off the Grid, our job is to help homeowners across the country save money on their electric bills by having the best solar installers compete for their business.
- Every day, light hits your roof’s solar panels with photons (particles of sunlight).
- The panel converts those photons into electrons of direct current (“DC”) electricity. Naturally, the sunnier it is, the more energy is produced by the panels.
- Those produced electrons flow out of the panel and into an inverterand other electrical safety devices.
- The inverter converts that “DC” power into alternating current or “AC” power. AC power is the kind of electric juice that your television, computer, and toasters use when plugged into the wall outlet.
- A bi-directional meter keeps track of the all the power your solar system produces. Any solar energy that you don’t use immediately will go back into the grid through the meter. Then at night or on cloudy days, that extra solar juice is credited back to your bill. So, net meteringis similar to having a virtual battery-back up system (we explain more about grid-tied solar home solar systems later)
High electricity bill? We can help.At One Block Off the Grid, our job is to help homeowners across the country save money on their electric bills by having the best solar installers compete for their business.
Solar panels work through what is called a photovoltaic process – where radiation energy (photo) is absorbed and generates electricity (voltaic).
Solar Panel Diagram: A cell level view of how solar panels work.This is called a photovoltaic process.
Radiation energy is absorbed by semi conductor cells – normally silicon – and transformed from photo energy (light) into voltaic (electrical current).
When the sun’s radiation hits a silicon atom, a photon of light energy is absorbed, ‘knocking off’ an electron.
These released electrons create an electric current.
The electric current then goes to an inverter, which converts the current from DC (direct current) to AC (alternating current).
The system is then connected to the mains power or electricity grid.
Crystalline Silicon Solar PanelsTraditional systems, called crystalline silicon solar modules, involve wafers of refined silicon beneath sheets of glass. The panels are surrounded by a metal frame.
A solar panel installer connects crystalline silicon panels – made with silicon wafers, glass panelling, and a frame.
These are by far the most common solar panels. If you’ve come across a solar panel installation, chances are it uses crystalline silicon technology.
Crystalline silicon technology has been used for around 50 years, and was first developed for powering satellites in space.
Current off the shelf crystalline silicon systems are generally capable of converting up to about 18 % of solar radiation exposure into useable electricity. This is termed as aphotovoltaic efficiency of 18%.
The main complaint of crystalline silicon is that the systems are expensive and bulky, installation requires a lot of wiring and labour, and that glass can be prone to damage.
Thin film solar panelsThe new breed of solar technology is thin-film solar panels. Thin film is less bulky than crystalline silicon, and increasingly cheaper to produce.
New tech: Thin film solar panel cladding at the Solar Decathlon in Washington.
Thin-film solar energy systems currently have a lower photovoltaic efficiency than crystalline silicon – converting around 8% of radiation exposure – however the conductibility is expected to sharply rise as current research improves the method.
Thin-film solar panels work in the same photovoltaic manner as crystalline silicon modules, without the bulky wafers and glass panelling.
Amorphous silicon is a material usedin some thin-film flexible solar panels, which can be moulded to essentially any surface such as roofs or walls.
Rethinking How Solar Panels Work – New Methods and ApplicationsSolar research and development has boomed around the world over the last few years. These include new photovoltaic conversion methods and application technology, large scale solar farms, and increasingly efficient technology.
Below are a few of these developments.
Stirling Energy Systems’ California plant has developed a new solar electricity production method.
They use the sun’s radiation to heat hydrogen gas, which spins a generator, producing electricity. This method has a reported expected efficiency of 30%.
Another development is the number of large scale solar farms, which has recently spiked.
There are now 56 large scale (20 megawatt or more capacity) solar farms, with at least 27 more in the planning or development stages.
One of the largest, the Montalto di Castro Solar Park in Italy, produces 40,000 megawatt hours per year, enough electricity to power around 13,000 Italian households.
American company Solar Roadways has recently been awarded a grant by the US Federal Highway Administration to develop a solar car park.
The idea is to cover the car park’s surface in solar panels, creating a vast surface area for clean electricity production.
Solar Roadways co-founder Scott Brusaw envisages the project spreading to roads once the technology and methodology has been developed with the carpark project.
Beyond the possibility of turning whole roads into electric grids, other features in the pipeline include built in de-icing mechanisms and LED lighting for driver visibility, as well as recharging stations for electric cars – all using free solar energy.
Another US company, Dow Chemicals, have developed thin-film solar roof tiles.
The solar roof tiles are physically like any other roof tile, and are nailed to the roof just like traditional tiles.
How the tile solar panels work is along the same concept as conventional solar – the tiles plug into each other to create an array, then an electrician connects the panels to an inverter, and into the mains power of the building.
Solar Panel Diagram: A cell level view of how solar panels work.This is called a photovoltaic process.
Radiation energy is absorbed by semi conductor cells – normally silicon – and transformed from photo energy (light) into voltaic (electrical current).
When the sun’s radiation hits a silicon atom, a photon of light energy is absorbed, ‘knocking off’ an electron.
These released electrons create an electric current.
The electric current then goes to an inverter, which converts the current from DC (direct current) to AC (alternating current).
The system is then connected to the mains power or electricity grid.
Crystalline Silicon Solar PanelsTraditional systems, called crystalline silicon solar modules, involve wafers of refined silicon beneath sheets of glass. The panels are surrounded by a metal frame.
A solar panel installer connects crystalline silicon panels – made with silicon wafers, glass panelling, and a frame.
These are by far the most common solar panels. If you’ve come across a solar panel installation, chances are it uses crystalline silicon technology.
Crystalline silicon technology has been used for around 50 years, and was first developed for powering satellites in space.
Current off the shelf crystalline silicon systems are generally capable of converting up to about 18 % of solar radiation exposure into useable electricity. This is termed as aphotovoltaic efficiency of 18%.
The main complaint of crystalline silicon is that the systems are expensive and bulky, installation requires a lot of wiring and labour, and that glass can be prone to damage.
Thin film solar panelsThe new breed of solar technology is thin-film solar panels. Thin film is less bulky than crystalline silicon, and increasingly cheaper to produce.
New tech: Thin film solar panel cladding at the Solar Decathlon in Washington.
Thin-film solar energy systems currently have a lower photovoltaic efficiency than crystalline silicon – converting around 8% of radiation exposure – however the conductibility is expected to sharply rise as current research improves the method.
Thin-film solar panels work in the same photovoltaic manner as crystalline silicon modules, without the bulky wafers and glass panelling.
Amorphous silicon is a material usedin some thin-film flexible solar panels, which can be moulded to essentially any surface such as roofs or walls.
Rethinking How Solar Panels Work – New Methods and ApplicationsSolar research and development has boomed around the world over the last few years. These include new photovoltaic conversion methods and application technology, large scale solar farms, and increasingly efficient technology.
Below are a few of these developments.
Stirling Energy Systems’ California plant has developed a new solar electricity production method.
They use the sun’s radiation to heat hydrogen gas, which spins a generator, producing electricity. This method has a reported expected efficiency of 30%.
Another development is the number of large scale solar farms, which has recently spiked.
There are now 56 large scale (20 megawatt or more capacity) solar farms, with at least 27 more in the planning or development stages.
One of the largest, the Montalto di Castro Solar Park in Italy, produces 40,000 megawatt hours per year, enough electricity to power around 13,000 Italian households.
American company Solar Roadways has recently been awarded a grant by the US Federal Highway Administration to develop a solar car park.
The idea is to cover the car park’s surface in solar panels, creating a vast surface area for clean electricity production.
Solar Roadways co-founder Scott Brusaw envisages the project spreading to roads once the technology and methodology has been developed with the carpark project.
Beyond the possibility of turning whole roads into electric grids, other features in the pipeline include built in de-icing mechanisms and LED lighting for driver visibility, as well as recharging stations for electric cars – all using free solar energy.
Another US company, Dow Chemicals, have developed thin-film solar roof tiles.
The solar roof tiles are physically like any other roof tile, and are nailed to the roof just like traditional tiles.
How the tile solar panels work is along the same concept as conventional solar – the tiles plug into each other to create an array, then an electrician connects the panels to an inverter, and into the mains power of the building.