Top solar technology for 2018

How much do you know about innovations in solar power? Take a look at recent technological innovations that will transform the energy landscape globally. By Subhajit Roy, Group Editor

Picture Courtesy: www.lovetoknow.com

Solar power on cloudy days!

Researchers at the Canada’s University of British Columbia found a cheap, sustainable way to build a solar cell using bacteria that convert light to energy, even under overcast skies.

This innovation could be a step toward wider adoption of solar power in places like British Columbia and parts of northern Europe where overcast skies are common. With further development, these solar cells—called “biogenic” because they are made of living organisms— could become as efficient as the synthetic cells used in conventional solar panels. “Our solution to a uniquely B.C. problem is a significant step toward making solar energy more economical,” said Vikramaditya Yadav, a professor in UBC’s department of chemical and biological engineering who led the project.

Solar cells are the building blocks of solar panels. They do the work of converting light into electrical current. Previous efforts to build biogenic solar cells have focused on extracting the naturaldye that bacteria use for photosynthesis. It’s a costly and complex process that involves toxic solvents and can cause the dye to degrade.

The UBC researchers’ solution was to leave the dye in the bacteria. They genetically engineered E. coli to produce large amounts of lycopene—a dye that gives tomatoes their red-orange colour and is particularly effective at harvesting light for conversion to energy. The researchers coated the bacteria with a mineral that could act as a semiconductor, and applied the mixture to a glass surface.

With the coated glass acting as an anode at one end of their cell, they generated a current density of 0.686 milliamps per square centimetre—an improvement on the 0.362 achieved by others in the field.

“We recorded the highest current density for a biogenic solar cell,” said Yadav. “These hybrid materials that we are developing can be manufactured economically and sustainably, and, with sufficient optimization, could perform at comparable efficiencies as conventional solar cells.”

The cost savings are difficult to estimate, but Yadav believes the process reduces the cost of dye production to about one-tenth of what it would be otherwise.

‘Funnelling’ the sun’s energy more efficiently

A team of experts from the University of Exeter has developed a breakthrough technique that could unlock new methods of making solar energy more efficient.

The new technique relies on ‘funnelling’ the sun’s energy more efficiently directly into power cells, such as solar panels or batteries.

In the research, the team of physics experts developed how to ‘funnel’ electrical charge onto a chip. Using the atomically thin semiconductor hafnium disulphide (HfS2), which is oxidised with a highintensity UV laser, the team were able to engineer an electric field that funnels electrical charges to a specific area of the chip, where they can be more easily extracted.

“While current solar cells are able to convert into electricity around 20 per cent of the energy received from the Sun, the new technique has the potential to convert around 60 per cent of it by funnelling the energy more efficiently,” the researchers claim.

Designing high-efficient organic solar cells

Semi-transparent solar module
Photo credit: Thor Balkhed

Twenty-five researchers from seven research institutes have put their heads together to draw up rules for designing high-efficiency organic solar cells. The research is led by Feng Gao, associate professor at Linkoping University (LiU), Sweden.

Organic solar cells, made from carbon-based materials, present unique advantages compared with other solar cell technologies. For example, they can be manufactured through low-cost printing technologies, and they can be made semi-transparent with selectable colours, which can be used architecturally in building integration. Their flexibility and low weight make them perfect for powering the sensors for the internet of things applications.

A key challenge facing the development of organic solar cells is that they usually have large energy losses. The researchers have formulated some rational design rules to minimise energy losses in organic solar cells.

Using these design rules, organic solar cells promise to catch up with their competitors with respect to power conversion efficiency, which measures the fraction of the energy in the Sun’s radiation that is converted to electricity. “The theoretical limit for the fraction of the Sun’s energy that can be obtained in solar cells is around 33 per cent. Laboratory experiments with silicon-based solar cells have achieved 25 per cent at best,” an official statement said.

Researchers have until now believed that the limit for organic solar cells is lower. “But we now know that there is no difference – the theoretical limit is the same for solar cells manufactured from silicon, perovskites or polymers”, says Olle Inganas, professor of biomolecular and organic electronics, Linkoping university.

Fluorination to enhance organic solar cells performance

An international team of materials scientists from France, Russia and Kazakhstan found a way to boost the efficiency of organic solar cells several times by incorporating fluorine atoms in the polymer. This process, known as fluorination, was previously shown to enhance polymer photovoltaic properties, but the mechanism was poorly understood. The new study clarifies the effect of fluorination on cell efficiency.

By experimenting with various polymer modifications, the team increased cell efficiency from 3.7 to 10.2 per cent. While this still falls short of the commercial silicon photovoltaics, the massive gain in efficiency suggests that polymer-based cells are a technology to be reckoned with. Perhaps with further tweaks organic solar cells could outperform their polysilicon-based counterparts.

According to co-author of the study Professor Dimitri Ivanov, what made the study challenging was the “need to optimise solar cell efficiency by picking the right molecular energy levels of the donor and the acceptor, while also creating the appropriate supramolecular structure that would facilitate charge transport to the electrodes.”

Store solar heat with STF

Although the Sun is a virtually inexhaustible source of energy, it’s only available about half the time we need it — during daylight. For the Sun to become a major power provider for human needs, there has to be an efficient way to save it up for use during nighttime and stormy days. Most such efforts have focused on storing and recovering solar energy in the form of electricity, but the finding by MIT professor Jeffrey Grossman and his team could provide a highly efficient method for storing the Sun’s energy through a chemical reaction and releasing it later as heat.

The key to enabling long-term, stable storage of solar heat, according to the team’s findings, is to store it in the form of a chemical change rather than storing the heat itself. Whereas heat inevitably dissipates over time no matter how good the insulation around it, a chemical storage system, known as solar thermal fuels (STF), can retain the energy indefinitely in a stable molecular configuration, until its release is triggered by a small jolt of heat (or light or electricity).

Turn your building into batteries

Energy storage issue could soon become a thing of the past thanks to the discovery of new cement mixtures. Researchers at Lancaster University have developed a new smart cement mixture that is able to store electricity for long periods of time. When fully optimised, the potassium-geopolymetric (KGP) composites that is made from flyash and chemical solutions, could have the potential to store and discharge between 200 and 500 watts per square metre.