Due to its environmental friendliness, zero pollution, and other advantages, solar energy is slowly gaining on other conventional forms of energy. Photo: Pixabay

CAPE TOWN – Despite the view of some sceptics, current trends worldwide point towards a greater adoption of solar energy. Due to its environmental friendliness, zero pollution, and other advantages, solar energy is slowly gaining on other conventional forms of energy.

The sun is one of the most abundant energy resources in the universe. According to the some resources, every five days, the sun delivers an amount of energy similar to the total supply of all known oil, coal and natural gas on earth. If we could only capture a fraction of the sun’s energy – about one 6000th of the 120 000 terawatts of radiation to be more precise – we would be able to meet the total energy need of the world. In different words: The sun covers the Earth with sufficient photons in one hour to meet the whole world’s energy needs for a year. And the wonderful news is that unlike fossil fuels, solar energy will not expire soon.

No wonder that we are experiencing an amazing wave of Fourth Industrial Revolution innovations with regard to solar energy. Last week we covered cost effective perovskites and the great strides made with regard to photovoltaic cell efficiency. However, what we have seen so far might just be the proverbial tip of the iceberg. 

When we think of solar photovoltaic energy it conjures the image of panels on a roof. But researchers are studying a number of unconventional solar applications that may contribute to our ever-increasing energy needs. 

One of these innovative applications is the creation of solar powered roads. Due to the current efficiency rates industrial scale solar panels take up considerable land to deliver enough electricity. If highways and roads are thus lined with solar panels, large amounts of electricity could be generated. Solar roadways are currently being tested in the Netherlands and on the sidewalks along the famous and historic Route 66 in the USA. The benefit of these panels is that it can provide power to the LED road lights and also thermal heating to melt the snow during the winter months. The sidewalk tests will be followed soon by tests on certain road segments of Route 66.

Closely related to this innovation is the building of photovoltaic solar noise barriers. In the USA, Europe and some other countries highway traffic noise is curbed through the building of thousands of kilometres of noise barriers. Recently the US Department of Energy has announced that they will in future use these barriers to generate electricity. Given the widespread use of noise barriers in the USA, they calculated that they could produce around 400 GigaWatt hours (GWh) per year, which equals the electricity usage of roughly 37 000 homes.

Floating solar farms (or floatovoltaics) is another way to address land use concerns since 70% of the earth’s surface is covered by water. The French company Ciel et Terre are experimenting with this technology in France, Japan and England by placing panels on reservoirs, dams and other water bodies. Similar projects are being undertaken in India and California. One major benefit is that the installation cost is much less than land-based photovoltaic panels. Research has also shown that the power production of floating solar panels is 10% higher due to the cooling effect of the water.

In addition to the cost and efficiency benefits, the solar panels also help to reduce the loss of water due to evaporation as it limits air circulation and blocks sunlight from the surface of the water. The floating farms further prevent algae production and thus lower water treatment costs.

Scientists from Japan are reviving space based solar - a technology that was first tested more than forty years ago. This technology entails space-based satellites that capture sunlight and convert it into microwave energy, which is then beamed back to a base station on earth. Since the satellites could be positioned to optimise the capturing of sunlight twenty-four hours a day and the amount of power collected increases as you move closer to the sun, they can capture significant more sunlight (about 90%) than panels on earth. India, China and Japan are currently investing large amounts of money in these technologies.

At the Idaho National Laboratory in the USA scientists have been researching very thin solar film that will enable them to capture solar energy even after sunset. This nanotechnology approach entails the attachment of billions of nanoantenna-square conductor gold squares or spirals onto a polyethylene (plastic) sheet. The nanoantennas have the ability to absorb infrared energy not only during the day, but also those that is released after sunset, thus making them much more energy efficient. This will ensure that the infrared energy of the sun, which mostly goes to waste with current solar panels, will be converted into useful energy. The result is that these nanoantennas absorb close to 80% of the available energy from the sun.

Recent research has also discovered that some bacteria such as cyanobacteria, can generate enough electricity to power certain wireless devices. The researchers believe that these bio-solar cells could be valuable in the future generation of electricity.

A major breakthrough is the “Spray On” solar cell technology. Mitsubishi was the first to invest in the research of this technology. But it was only with the development of perovskite that the final breakthrough came. Perovskite makes it possible to harvest light in the form of liquid solar cells. It is thus possible to place this technology on a variety of surfaces. When dried the perovskite solar cells act as semiconductors and generate electricity from the sunlight.

The Massachusetts Institute of Technology (MIT) in the USA has developed an interesting approach to the harvesting of solar energy. Single-junction silicon cells are limited to a maximum of 33.7% efficiency (the Shockley-Queisser limit) since the spectrum of solar radiation used to generate electricity is limited to visible light. To increase the efficiency of solar cells MIT scientists altered the harvesting procedure by using a light concentrator made of carbon nanotubes known as an “absorber-emitter.” The absorber-emitter turns sunlight into heat. One of the layers then radiates the energy back out as light so that the photovoltaic cells can absorb it.

In the field of energy storage similar innovations have been announced. A new type of system could revolutionise the storage of energy and also decrease the charging time of electric cars from hours to minutes. In an academic paper published a few months ago in the journal Nature Chemistry, professor Lee Cronin and colleagues from the University of Glasgow described how they developed a “hybrid-electric-hydrogen” flow battery system using a nanoscale battery molecule that can store electric power or hydrogen gas and release it on demand.

When a concentrated liquid containing nano-molecules is produced, it can store about ten times more energy.  This energy can be released either as electric power or as hydrogen gas. Electric cars could thus be charged in minutes, as the fuel is a pumpable liquid. The old battery liquid would be removed at the same time and then recharged for later use.

Professor Cronin is convinced that their electrochemical research will pave the way for new flexible energy storage systems and make the recharging time of electric cars more realistic. The high energy density of their material could also increase the range of electric cars and the resilience of energy storage systems to provide electricity at times of high demand.

The future of solar indeed looks promising. Due to recent innovations solar energy generation has moved beyond ground-mounted or rooftop panels. The photovoltaic panels are now lighter, more flexible and would in future even generate electricity at night.

However, many of the innovative next-generation solar cells with much higher efficiency rates have yet to find their way into commercial products. Although new material science breakthroughs will push the efficiency potential of solar cells to eventually provide more efficient and cheap solar energy, we will have to be patient. However, with rising energy costs, the price-performance ratio of solar technologies is increasingly undercutting traditional energy sources.

Professor Louis C H Fourie is a technology strategist. [email protected]

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