SolarGas Part 1: What it’s all aboutPosted: Thursday, 29th September, 2011
It’s a clear spring day in this photo of Solar Field 1 at our Newcastle site. There’s obviously plenty of sunshine to power solar panels or solar turbines. But in this case there’s more going on than meets the eye. Even after the sun has set we’ll still have a supply of solar energy, thanks to what’s in the small shed circled below.
In the shed is a group of gas cylinders. They’re holding the product of a process that CSIRO has developed to near commercial demonstration that captures and stores solar energy for later use. Because the added solar energy is stored in the chemical bonds of a gas, we call the product SolarGas™.
SolarGas isn’t just a way of storing solar energy. It’s also a way to add solar energy to fuels like natural gas, and it can even be used in production of many liquid fuels and fine chemicals which currently rely on finite fossil fuel feedstocks. It’s been one of the main areas of research and development for our solar thermal team over the last decade, and that’s because we think it’s a really versatile product that’s well suited for Australian resources and needs.
I get asked questions about SolarGas all the time from people ranging from school students to scientists. For people who don’t work in process industries (that’s most of you, I’m guessing) I’ve realised that to really get across why SolarGas has so much potential, it’s necessary to take a bit of time to start at the beginning and explain the concepts involved. Unlike a system that produces electricity – which we can all relate to, because we use it to power our kitchen blenders and so on – SolarGas applications are more varied and perhaps might seem a bit further from home (related more closely to, say, the industrial manufacture of hydrogen rather than lighting our houses at night). Nonetheless, it has the potential to have huge benefits that are worth understanding. That’s why I’ve chosen to spread this article over two sections, and why I’m going to write it for the sort of reader who prefers to call a fire ‘hot’ rather than ‘exothermic’. No apologies.
How it’s made
To make SolarGas, we use mirrors to focus solar energy onto a series of metal pipes, which creates temperatures of around 800°C inside them. Through these pipes we flow a stream of natural gas mixed with something else. This ‘something else’ can be steam or carbon dioxide – both pretty common ingredients, suited to different situations.
These metal pipes form our SolarGas Reactor, and they have been carefully designed so that inside them the conditions are right for a chemical reaction to occur. This reaction converts the natural gas and steam (or carbon dioxide) to a new mix of gases, and in the process ‘sucks up’ a whole lot of solar energy into the new gas molecules in what is called an endothermic reaction. If you could touch the pipes where the reaction is going on (and we wouldn’t recommend it) you’d feel that they’re actually cooled as energy transfers from solar heat to chemical bonds – thus changing it into a form that, unlike the energy in sunlight, can be stored in bottles or pumped from place to place.
It’s interesting to note that steam and carbon dioxide are the products of normal combustion. So here, where we’re using them as the reactants, we’re in essence turning the usual reaction around using energy from the sun. That’s neat.
So, the result is that we’ve produced a new gas that has more energy than the gas we started with – and this extra energy came from the sun. The video below gives an overview of the process. In this example, the more common steam version of the reaction is shown.
You might have noticed that the video shows what SolarGas is. It’s made up of hydrogen and carbon monoxide – specifically, three units of hydrogen gas for every molecule of carbon monoxide gas. This mixture makes the gas very useful in a number of ways.
But that’s a topic that deserves a post of its own. Next: Part II – how it can be used.