For the first time since 2019, Eskom has implemented stage six scheduled power cuts – leaving South Africa in the dark, at great cost to the country’s fragile economy and to the inconvenience of its citizens. Whether this is the beginning of the end of a grossly outdated business model and problem-ridden company, is not for me to say. However, what I do know is that the executives of Eskom recently announced that we would experience even more disruptive load shedding in the future.
This means that South Africans will have to make provision for their own power generation, just like they often have to make provision for their own security, own healthcare, own water, own education, own transport, and filling their own potholes and maintaining their own municipal infrastructure.
Luckily the citizens of South Africa do have alternative energy sources, since we are blessed with an abundance of sunshine and even wind.
As electricity costs keep increasing, solar is becoming an even more viable and cost-effective option for businesses and private homes in South Africa. While there is quite an initial outlay cost, it can be recouped after five to eight years on average due to the ever increasing Eskom electricity tariffs.
Several large (up to 100MW) photovoltaic (PV) and concentrated solar power (CSP) farms have been developed, while thousands of households have installed small scale solar PV (rooftop and ground-mounted) units.
One solar company reported that it is was installing 9MW of residential solar power per month in 2020 – enough clean power for 3 000 homes. According to a recent market study by Technavio, the solar energy market share in South Africa is expected to grow at an accelerated compound annual growth rate (CAGR) of 29.74 percent.
Unfortunately, one of the problems with solar is the percentage of solar energy reaching a PV cell that is converted into usable electricity (the conversion efficiency of PV cells). The conversion rate for most commercially available multi-crystalline silicon solar cells is about 14 to 19 percent.
In 2015, researchers at Saurashtra University in Rajkot, India, used a mixture of tomato extract, carbon and titanium dioxide to develop a carbon nano-dot based lycopersicum solar cell, which is 75 percent cheaper when compared to the solar panels of the time.
Professor Nikesh Shah established that when a film of the mixture was pasted on a glass window with connecting wires, it has the potential to generate solar power – and could light up a bulb.
In 2017, D R Shinde and his research team from India found that lycopene (the natural pigments that make tomatoes red) can be used as a photo-sensitiser in solar cells. This was followed by further research confirming that tomato pigment could be used in bio-solar cells, or as sensitisers.
Now, Donglei Zhou and his fellow researchers from Jilin University in Changchun, China, have found that lycopene can improve the efficiency and stability of perovskite (a titanium and calcium crystal) solar panels.
About 95 percent of commercial solar cells are silicon-based (a semiconductor). The basic principle of a PV cell is to force the electrons and electron vacancies to move towards the opposite side of the material. This is done by using two semiconductor material layers, doped respectively with P (with an excess of holes) and N (with an excess of electrons), and called a P-N junction.
More recently, a new generation of solar cells have been developed from very thin films of perovskite (PSCs), which promise better efficiencies than silicon solar cells and are particularly inexpensive to manufacture.
Unfortunately, perovskite cells decompose much faster than silicon-based cells in the presence of light, thus leading to a performance drop after a few minutes of sunshine.
Perovskite is sensitive to humidity and temperature. Further, it is not a single-crystal material, which makes it prone to chemical defects. Some of the electrons created by light radiation are also trapped in the atomic grid and often block the electrodes. These factors all contribute to the general structural instability of perovskite solar cells.
Due to the toxicity of the materials used in the production of perovskite cells, they are not environmentally friendly and viable. However, their low manufacturing cost and efficiency have been of commercial interest, spurring numerous scientists to try and find a way to increase their stability to prevent their performance from degrading.
It is in this context that the Jilin University researchers conducted their research with the powerful antioxidant lycopene, which is found in some red fruits and particularly in tomatoes. Lycopene is known to protect the skin of the fruit from cell damage caused by solar ultraviolet (UV) rays. This is done through the binding of lycopene to free radicals produced by the ultraviolet light. The researchers thus tested whether lycopene could slow down the degradation of perovskite cells when they are exposed to UV radiation and oxygen.
The results were encouraging – lycopene reduced the number of electron entrapment sites and reduced stability – by stabilising multi-crystal grain boundaries, by improving crystallinity, and even by reducing the density of electron traps to improve the flow of electricity.
The modified solar cells are not only more stable, but also more efficient, with an increased energy conversion efficiency ranging from 20.57 percent to 23.62 percent. The solar device also exhibited improved hydrophobic and antioxidant properties, high oxygen stability, improved UV resistance and long-term stability.
According to the Jilin University research team, “[t]his work represents a strategy to address the efficiency and stability issues of PSC devices inspired by natural plants, paving the way for the development of environmentally friendly PSCs with high efficiency and stability… ”
However, much more work needs to be done before this cell type can be commercialised and its long-term effectiveness established.
Without doubt, under current circumstances, solar energy is the most readily accessible resource in South Africa, lending itself to a number of potential uses. And it seems that a dash of tomato pigment may make it easier and cheaper in the future. Current innovations in PV cells build hope for better, renewable and cheaper sources of energy.
In particular, PV power is a financially viable and environmentally friendly solution for South Africa to reduce reliance on fossil fuels and boost the country's economy. The less reliant we all are on the national grid for our electricity, the less we have to worry about the constant increases in energy prices and disruptive load shedding.
It turns out that tomatoes, besides being loved for their taste, can also be used to produce electricity and improve the efficiency of certain solar cells. It is perhaps time to consider solar energy for your house or business. Unfortunately, the problem with providing your own electricity is that the poorest households will suffer even more since the installation of solar power systems is currently still expensive. And so is paraffin and gas alternatives.
Professor Louis C H Fourie is an Extraordinary Professor at the University of the Western Cape.
BUSINESS REPORT ONLINE