ROMA – TABEMPE Lesenyeho, a Masters of Sustainable Energy graduate from the National University of Lesotho (NUL), is eating cooked chicken hearts.
He has just cooked them with a solar cooker he and his teammates made.
It is low-cost, portable, uses free energy from the heavens and can be used wherever you are.
The giant cooker Lesenyeho displays at the NUL picks up sunlight and directs it to a pot and the cooking starts.
Lesenyeho and team are responding to a problem—a serious problem.
Basotho women in general spend a disproportionate amount of time in the business of cooking.
They have traditionally used cow dung and wood for cooking and they have to go around fetching them.
That adds too much to their already busy schedule.
Plus those fuels are running out.
What could be other alternatives?
“We believe this cooker could be among the tools that can help, especially in sunny days of the year,” Lesenyeho introduced his gadget.
Today, we are going to go through the solar cooker and consider it alongside our understanding of solar energy to really appreciate how the cooker works.
Most of the energy we use on earth comes directly or indirectly from the sun.
We would all be dead, in fact, we would not have lived at all, without the sun.
Before you finish reading this sentence, you will have used some energy from the sun.
It was trapped during a process of photosynthesis by the plant (food) you ate or it was transferred from the plant to the animal (food) you ate.
In much of this, the sun’s energy was absorbed and changed into other forms of energy.
“We use a similar process with the solar cooker,” Lesenyeho said.
So let’s start the journey.
The journey starts from the heavens, right inside the sun, where light is produced.
That’s an odd place to begin but it sure begins there.
Light is made of particles called photons which—can you believe it—have no mass!
When it leaves the centre of the sun, a photon might take 10 000 years or many, many more years before it reaches the sun’s surface.
But out of the sun’s surface, the photon will take just 8.3 minutes to reach the earth, travelling through a distance of 150 000 kilometres.
Only light travels at the speed of light.
It is faster than anything we know.
Once it reaches us the mortals on the surface of the earth, Lesenyeho and his team are already waiting.
They’ve got plans for it!
Thaane ’Mokose and Molibeli Rakauoane are other members of his team.
They are supervised by Dr Naleli Matjelo and Professor Leboli Zak Thamae.
All this is happening under the NUL Energy Research Centre and the NUL Innovation Hub.
In order to make a wise use of light from the sun, you have to understand it.
As Physics students, the fearsome threesome know a thing or two about light.
“So we generated Physics equations that would help us make use of the light,” he said.
So when the light from the sun touches their solar cooker surface, it is reflected.
That is because Lesenyeho and the team have selected a specifically shiny material with which to cover the inside of their cooker. But the light is not reflected to just about anywhere.
This is where the Physics equations come in.
“Based on those equations, we have designed the cooker such that when light hits its surface, it is directed to the pot placed at the centre of the cooker.”
The idea is to have the pot bombarded with as many of the light particles as possible.
Now something interesting happens when the light reaches the pot.
The pot is black so that it can absorb as much of the light as possible.
Have you realised you get cooked more when wearing a black t-shirt in a hot summer day?
If you didn’t know, now you know.
According to Lesenyeho, “the light is then absorbed by the pot and turned into heat.”
Sounds simple but it is not.
In fact, how exactly that happens and what it means, can come in so many explanations and here is one of them.
Remember light is made of the particles called photons.
When the photons enter the black body, the pot, the particles that make the pot itself (the atoms) get excited!
Well, that in science does not mean they get happy (although they might as well be, who doesn’t enjoy getting visitors with bundles of energy?).
It simply means the photons give them some energy they did not have.
Some of these atoms are so excited that they do not just shake, they move.
Yes they jump with “excitement”!
As they move, they lose some energy and we feel some of that energy as “heat.”
That heat is transferred from the black pot to the food inside.
The food particles also get so “excited,” they get cooked. Lesenyeho is now ready to eat.
Own Correspondent