Curious Kids: how do solar panels work?



Installing solar panels on a roof.
Shutterstock/lalanta71

Andrew Blakers, Australian National University


How do solar panels work? – Nathan, age 5, Melbourne, Australia.



The Sun produces a lot of energy called solar energy. Australia gets 20,000 times more energy from the Sun each day than we do from oil, gas and coal. This solar energy will continue for as long as the Sun lives, which is another 5 billion years.

Solar panels are made of solar cells, which is the part that turns the solar energy in sunlight into electricity.

Solar cells make electricity directly from sunlight. It is the most trusted energy technology ever made, which is why it is used on satellites in space and in remote places on Earth where it is hard to fix problems.




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Curious Kids: how does electricity work?


How do solar cells work?

Solar cells are made using silicon atoms. An atom is basically a building block – just like a Lego brick but so tiny you’d need a special machine to see them.

Because the silicon atoms are so small you need trillions and trillions of them for a solar cell.

To make the solar cell you need a wafer layer of silicon, about the same size as a dinner plate but much much thinner – only about three times the thickness of a strand of your hair.

This silicon layer is changed in a special way using hot temperatures of up to 1,000℃. Then, a sheet of metal is put onto the back of the layer and a metal mesh with holes in it, like a net, is put on the front. It is this mesh side of the layer that will face the Sun.

When 60 solar cells are made they are fixed together behind a layer of glass to make a solar panel.

On this roof you can see one solar hot water collector (top left) and 42 solar electricity panels, each of which is made of 60 solar cells combined behind a protective glass.
Shutterstock

If your house has a solar power system, it will probably have 10 to 50 solar panels attached to your roof. Millions of solar panels are used to make a large solar farm out in the countryside.

Each silicon atom contains extremely tiny and lightweight things called electrons. These electrons each carry a small electric charge.

Each tiny silicon atom has a nucleus at the centre made up of 14 teeny-tiny protons and 14 teeny-tiny neutrons. And 14 teeny-tiny electrons go around the nucleus. It doesn’t really look exactly like this diagram but you get the idea.
Shutterstock

When sunlight falls on a solar panel it can hit one of the electrons in a silicon atom and knock it free.

These electrons can move around but because of the special way the cell is made they can only go one way, up towards the side that faces the Sun. They can’t go the other way.

So whenever the Sun is shining on the solar cell it causes many electrons to flow upwards but not downwards, and this creates the electric current needed to power things in our homes such as lights, the television and other electrical items.

If the sunlight is bright, then lots of electrons get hit and so lots of electric current can flow. If it is cloudy, then fewer electrons get hit and the current will be cut by three quarters or more.

At night, the solar panel produces no electric power and we need to rely on batteries or other sources of electricity to keep the lights on.

How are solar cells being used?

Solar cells are the cheapest way to make electricity – cheaper than new coal or nuclear power stations. This is why solar cells are being installed around the world about five times faster than coal power stations and 20 times faster than nuclear power stations.

In Australia, nearly all new power stations are either solar power stations or wind farms. Solar and wind electricity can be used to run electric cars in place of polluting petrol cars. Solar and wind electricity can also heat and cool your house and can be used in industry in place of coal and natural gas.

Windmills and solar panels can produce electricity.
Shutterstock

Solar and wind are helping lessen the amount of greenhouse gases which damage our Earth. They are cheap, and they continue to get even cheaper and the more we use it the quicker we can stop using energy that can hurt the Earth (like coal, oil and gas).

What’s more, silicon is the second most common atom in the world (after oxygen). In fact, sand and rocks are made of mostly silicon and oxygen. So, we could never run out of silicon to make more solar cells.




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Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.auThe Conversation

Andrew Blakers, Professor of Engineering, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

11,000 scientists warn: climate change isn’t just about temperature



Land clearing, cattle populations and carbon emissions stand alongside temperature as important measures of climate change.
DAN PELED/AAP

Thomas Newsome, University of Sydney and William Ripple, Oregon State University

Exactly 40 years ago, a small group of scientists met at the world’s first climate conference in Geneva. They raised the alarm about unnerving climate trends.

Today, more than 11,000 scientists have co-signed a letter in the journal BioScience, calling for urgently necessary action on climate.

This is the largest number of scientists to explicitly support a publication calling for climate action. They come from many different fields, reflecting the harm our changing climate is doing to every part of the natural world.




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Why no change?

If you’re thinking not much has changed in the past 40 years, you might be right. Globally, greenhouse gas emissions are still rising, with increasingly damaging effects.

Much of the focus to date has been on tracking global surface temperatures. This makes sense, as goals like “prevent 2℃ of warming” create a relatively simple and easy-to-communicate message.

However, there’s more to climate change than global temperature.

In our paper, we track a broader set of indicators to convey the effects of human activities on greenhouse gas emissions, and the consequent impacts on climate, our environment, and society.

The indicators include human population growth, tree cover loss, fertility rates, fossil fuel subsidies, glacier thickness, and frequency of extreme weather events. All are linked to climate change.

Troubling signs over the past 40 years

Profoundly troubling signs linked to human activities include sustained increases in human and ruminant populations, global tree cover loss, fossil fuel consumption, number of plane passengers, and carbon dioxide emissions.

The concurrent trends on the actual impacts of climate change are equally troubling. Sea ice is rapidly disappearing, and ocean heat, ocean acidity, sea level, and extreme weather events are all trending upwards.

These trends need to be closely monitored to assess how we are responding to the climate emergency. Any one of them could hit a point of no return, creating a catastrophic feedback loop that could make more regions of Earth uninhabitable.




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The need for better reporting

We urge national governments to report on how their own results are trending. Our indicators will allow policymakers and the public to better understand the magnitude of this crisis, track progress, and realign priorities to alleviate climate change.

Some of the indicators could even be presented monthly to the public during news broadcasts, as they are arguably more important than the trends in the stock exchange.

It’s not too late to act

In our paper we suggest six critical and interrelated steps that governments, and the rest of humanity, can take to lessen the worst effects of climate change:

  1. prioritise energy efficiency, and replace fossil fuels with low-carbon renewable energy sources,

  2. reduce emissions of short-lived pollutants like methane and soot,

  3. protect and restore the Earth’s ecosystems by curbing land clearing,

  4. reduce our meat consumption,

  5. move away from unsustainable ideas of ever-increasing economic and resource consumption, and

  6. stabilise and ideally, gradually reduce human populations while improving human well-being.

We recognise that many of these recommendations are not new. But mitigating and adapting to climate change will entail major transformations across all six areas.

How can you help?

Individuals can make a difference by reducing meat consumption, voting for political parties and members of government bodies who have clear climate change policies, rejecting fossil fuels where possible, using renewable and clean sources of energy, reducing car and air travel, and joining citizen movements.

Lots of small changes will help inspire larger scale shifts in policy and economic frameworks.

We are encouraged by a recent global surge of concern. Some governments are declaring climate emergencies. Grassroots citizen movements are demanding change.




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As scientists, we urge widespread use of our indicators to track how changes across the six areas above will start to change our ecosystem trajectories.The Conversation

Thomas Newsome, Lecturer, University of Sydney and William Ripple, Distinguished Professor and Director, Trophic Cascades Program, Oregon State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.