# Lesson 1: A giant greenhouse

Global warming

Our planet is warming up. The poles are melting and in a while they will, so to speak, only exist in the history books your grandchildren will be reading. The polar bear in the picture has already seen the ice melt under his feet. Probably, you have seen a lot more of these pictures of melting ice shelves on the news or the Internet. That’s no coincidence: global warming is a hot topic all over the world. In particular, this can be attributed to Al Gore (if you don’t know him your parents will). In 2000 he started giving speeches on his worries about the health of the Earth. The documentary ‘An inconvenient truth’, based on these speeches, received an Academy Award for Best Documentary in 2007. Although some scientist question the reliability of the facts that Al Gore uses, his movie certainly made the world realize that our planet is in danger.

The greenhouse effect

So what’s this global warming all about? It all has to do with the greenhouse effect. The Earth’s atmosphere contains carbon dioxide (CO2). This gas acts as a blanket around the planet, capturing some of the suns energy. However, human influences like factories, cars and the cutting down of complete rainforests bring an extra amount of CO2 in our atmosphere every day. So, the blanket around our planet gets thicker and thicker and the Earth gets hotter every day.

Fossil fuels

Besides the big issue of dealing with the greenhouse effect there is another problem: our reserves of fossil fuels is shrinking fast. In about 60 years all of the oil and gas will be vanished and 70 years after that there will not be any coal left either. This, in itself, does not have to be a disaster: since CO2 is emitted when burning these fuels it would be better not to use them at all. However, there has not been found a sustainable way of producing energy that can substitute these fossil fuels. This is exactly the problem that many scientist are working on nowadays.

A method for generating energy should be:

- sustainable
- CO2-neutral

Light is the answer

In search of an energy generating technique it can be useful to learn from Mother Nature. For example, the growth of plants is a very intriguing process. Let’s consider an arbitrary flower. Using the energy of the sunlight, it converts CO2 and water into food and oxygen. This is called photosynthesis. So, in short, plants collect the energy to grow from sunlight. Now, if a simple plant can do that, why can’t we? The idea seems tempting. The light of the sun is always available and it will never run out. In this course you will be learning about a technique that converts sunlight into fuel. This technique is called the artificial solar tree.

Artificial solar tree

The artificial solar tree works like a real one. Just like the photosynthesis of a real tree, an artificial one uses sunlight for the generation of energy. The aim is to store the energy so we can use it wherever and whenever we need it. This can be done by making a liquid fuel that can be transport and used when needed. In the remainder of this course you will learn what challenges are involved when designing an artificial solar tree. These challenges are not solely scientific ones. You will also have to consider costs, environmental consequences and so on. When you have obtained enough knowledge about the artificial solar tree you are ready to make your own working fuel cell!