A magnifying glass to burn a leaf – an analogy to a useful renewable energy

Many people have, at some point, used a magnifying glass to burn something (whether it be an ant or a leaf) but did you know that this exact concept is being used as a renewable energy?

The Gemasolar solar thermal power plant, Spain (image credit “Beyond Coal & Gas Image Library” via Flickr)

The sun produces a lot of energy. I mean, it’s 149.6 million km away, but will still burn you pretty badly if you’re exposed to it for too long! Most energy utilised by modern civilization, when traced back, will originate from the sun – the obvious ones like energy from solar cells, from fossil fuels to all sorts of renewable energies like wind and hydro-electrical power. With these, the energy from the sun is converted into electrical, chemical or kinetic energy so it can be readily used by us.

Another renewable energy source captures the energy from the sun in a very simple way to produce either heat or electrical energy. Called Concentrated Solar Power (or CSP for short) it uses a array of mirrors to concentrate the suns rays to a small area, where water (or another liquid) is heated up. This heated liquid produces steam, which drives a steam turbine producing energy. That’s it. No complicated solar cell theory or unusual materials, or waiting for millions of years for dead plants and animals to turn themselves into oil and coal for us. Simply use the heat from the sun to heat water to produce electricity. Simples.

This method is currently being used right now in areas of Spain and California. Some of the largest CSPs are able to produce energy up to 360 Megawatts. By contrast, an average coal-driven power plant would generate around 500 Megawatts. So while it’s still a little behind it’s fossil-fuelled powered cousin, it’s not by much – and it’s doing pretty well considering they’ve only been around 15-20 years. Either way, it’s still a useful tool to have in your renewable toolbox.

Actual operating plants are a little more complicated than described above. While the principle is the same, concentrating a lot of mirrors into a small area can be difficult. Particularly when they move – as the sun is constantly moving across the sky, the mirrors need to change position to continue focusing the sunlight to the same spot. There can be many types of set-ups, such as parabolic troughs, solar power towers and even these nifty things called Fresnal reflectors, which all have their own strengths and weaknesses.

The Gemasolar solar thermal power plant, Spain (image credit “Beyond Coal & Gas Image Library” via Flickr)

The liquids that the thermal solar energy heats up can be varied too – of particular interest are molten salts. Whilst they need energy to make them melt initially, they absorb energy very efficiently and take a long time to cool down. So they can be stored and continue producing heat (and steam, and energy) even when there is no sunlight – such as at night. This gives CSPs a particular advantage over other solar energy technologies.

Shortly put, CSPs could be a pretty big piece in the renewable energy puzzle, and ending the world’s reliance on fossil fuels. As summarised quite well by Bill Nye; we can power the world with renewable energy, if we decided to just do it!