Energy-harvesting ‘tree’ can power electronics

Finnish company develops an energy harvesting ‘tree’ capable of powering smart phones and other devices. Its production technique can also be used to make sheets of smart organic light-emitting diodes on a large scale.

OULU, FINLAND (MARCH 12, 2015) (REUTERS) – Finnish researchers have developed an energy-harvesting ‘tree’ that can be used to charge electronic devices.

Technology company VTT Technical Research Centre, based in the northern city of Oulu, designed the tree to be decorative, as well as useful. The organic solar panel ‘leaves’ are flexible and patterned, as well as forming a complete electronic system. The tree trunk is made from wood-based biomaterials developed and 3D printed by the company.

VTT says the innovative tree can be produced using traditional manufacturing methods, making it a low-cost option.

The solar panel leaves are only 0.2mm thick, and includes the electrodes and polymer layers where light is collected. Additionally, graphics can be printed to improve the look of the leaf. In a test, the scientists printed 200 leaf-shaped photovoltaic cells which made one square metre of active surface that generated 3.2 amperes of electricity, with 10.4 watts of power at Mediterranean latitudes.

VTT communications officer Paula Bergqvist demonstrated the VTT tree powering an LED light, adding that it could be used to charge phones and other devices.

Ritvonen demonstrated a motion sensor used with the printed tree.

“Our printed solar cell panels can be utilised for example this kind of sensor systems. There is a presence sensor and the printed organic solar panels. When we are going closer to the painting, blue colours igniting, when we are going more close then red colour is igniting,” he said.

VTT’s printed optoelectronic systems team leader, Tapio Ritvonen, explained why the system used to produce the tree is so valuable.

“We are utilising low-cost mass manufacturing printing methods to produce, for example, organic solar-cell-panels, organic LEDs, memories, batteries, sensors, bio sensors and micro fluidics for example. This kind of a flexible thin, lightweight components can be done in high volumes. And this machine can produce over two thousand square metres of printed components per day,” he said.

VTT have used the same production method to plastic sheets of printed organic light-emitting diodes (OLEDs) for the first time on a large scale.

“This is a printed OLED device which is printed here in VTT also. It’s very flexible and very power efficient device,” said VTT research scientist Kaisa-Leena Väisänen.

VTT says the traditional printing technology used in manufacture allowed them to produce innovative products while reducing costs.

“This is a cost efficient manufacturing process just regular printing technology used and this enables completely new types of revolutionary lighting products to be developed like light emitting wall-papers, space dividers and so on,” explained smart lighting and integration concepts team leader Vesa Pentikäinen.

VTT says the technology used in the OLEDs could be applied to healthcare with the help of a smartphone.

“The stripes can be cut out from the roll and they can be used for measuring some analytes from your blood samples at home or at doctor’s office with a smart phone based camera system with an additional operational optical unit,” said research team leader Leena Hakalahti.

While the company has found a way to mass produce organic solar panels and OLEDs in a cost-effective way using traditional manufacturing methods, the solar ‘leaves’ on its energy harvesting tree are not yet as efficient as conventional silicon-based solar panels. VTT says its efforts to find a way to manufacture a new generation of solar panels using a mineral called perovskite have been promising.