Wearable solar cells have long been developed for a range of applications. The ANU has completed a AUD$2.3 million (USD$2.4 million) project with the ADU to produce a new generation of wearable solar cells. The cell technology, called SILVER, was developed by the ANU and will be manufactured by Transform Solar, which has bases in South Australia and Idaho, in the U.S.
The ANUs Center for Sustainable Energy Systems developed the SILVER cell process, which produces ultra-thin, elongated monocrystalline cells. These cells are highly flexible and bifacial, which means they can produce electricity when light strikes either side. Elizabeth Thomsen, from the ANU reasearch team, told pv magazine that cells, "have an elongate form factor, which […] allows them to be used in novel module designs." Thomsen said that another unique property of the cells is that their bifacial nature means there is, "virtually no shading of the cell due to metal."
In an unconventional approach to cell manufacture, 1.5-millimeter monocrystalline wafers are prepared to create the SILVER cells, which themselves are paper-thin. The surface area of the final cells is then created from the depth rather than the surface of the wafer. Each cell has typical dimensions of 20 to 10 um thick, 0.5 to 2 mm wide and five to 12 cm long.
The Chief Investigator on the project, Andrew Blakers, claims that the thin and flexible cells have advantages over similar cells when applied to clothing. "These cells have the same thickness of a sheet of paper or a human hair, " said Blakers in a statement. "This means they are flexible, lightweight and allow high power to weight ratios to be achieved."
In terms of efficiency Thomsen reported laboratory efficiencies of 20 percent. "Because the cells are made from monocrystalline silicon they have high
and stable efficiencies."
Wearable solar cells will help soldiers in the field, claims the projects Development Manager, Igor Skryabin. With increasing amounts of electrical devices used by soldiers, batteries can be bulky and each kit requires power supply of a different nature. "While battery technology research has delivered considerable improvements, the goal of a small, lightweight power storage system, capable of sustaining all electronic equipment for the whole time a soldier is in the field, is not yet available."
Skyrabin continued: "The development of these wearable solar cells will now allow soldiers to generate power in the field and reduce the need for batteries for their electronic devices. They will also establish a power supply that keeps electronic devices operational throughout the duration of missions."
In military circumstances and difficult field conditions durability of the cells is thought to be a major factor. Thomsen told pv magazine that the SILVER cells durability is due to a both the cells themselves and the circuit designs used. "The mechanical strength of the cells is unaffected by 100 000 flexures," explained Thomsen.
She continued, "The small size of the cells (around 1.5 mm width) means that battery charging voltage can be generated in a very small area by connecting
the cells in series. Each cell is connected to the adjacent cell with at least two connections, building in robustness. These series strings can then be connected in parallel to build up the required current. If a cell in one series string is damaged it will limit the performance of that particular string, but will not restrict the output of the rest of the module."