More Efficient Steam Generation

A simple and inexpensive but effective method of generating steam from solar energy could have a profound impact.

Hydrophilic absorbing layer on top combines with a hydrophilic insulating layer on the bottom

The steam turbine cycle can trace its origins to the industrial revolution. Coal was used to boil water which in turn drove pistons to create useful movement that could be harnessed by industry, causing a fundamental change in how society is structured. People who lived in industrial towns can remember the chimneys dotting the skyline, and on a Sunday night the smoke would start billowing out in preparation for Monday morning when the workers would come in. Giant machines would crank out power that was distributed mechanically through rotating shafts that ran the length of the building, and machines would be connected to the shafts via belt drives. Huge losses in energy were involved, much of it converted to deafening noise. This gave way to electrical distribution of energy that was much more efficient, controllable, and certainly quieter.

Pistons gave way to more efficient turbines, and we often think of steam as an antiquated technology that last saw its use in ocean-going ships. However the steam turbine cycle is still widely used in the generation of electricity. There is no other more practical way of converting heat to useful electrical power, and most of the world’s electricity comes through steam be it in coal-fired power stations, gas-fired power stations, or nuclear power.

However the cycle involves several stages in which there is plenty of scope for energy loss. Other methods of generating steam have been tried using solar power where light is concentrated into a transparent container to heat water, but again there are losses since not all of the light will penetrate the container no matter how clear it is.

A study published in the journal Nature Communications claims that a technique has been found that generates steam from solar energy with up to 85 percent efficiency. Researchers have developed a simple but effective porous material consisting of graphite on top and carbon foam on the bottom, forming a sponge which sits on top of water in a container. Solar energy strikes the graphite heating it up. This creates a pressure differential that draws the water up from below, creeping into the heated upper layer of the sponge where it evaporates.

The advantage of the materials used is that they are inexpensive and easy to come by. While the scientists say that the process cannot yet be used to generate electricity, it can definitely find other applications where the evaporation of water is useful. Developing countries that could use distilled water but have a lack of an electrical supply are one that springs to mind. Access to fresh water is an overlooked but significant contributor to conflict in multiple locations in history including Africa and the Middle East. Technology like this holds the potential to neutralize such conflicts and have as profound an effect in the twenty-first century as the steam turbine cycle did in the nineteenth century.