While China is usually quoted as the country that sports environmental pollution, the fact remains that it is now ahead of the US when it comes to renewable energy development and deployment while Chinese innovation in clean energy is becoming a regular source of inspiration.
One similar development is in the shape of ‘plastic grass’ and has been achieved by scientists at the Southwest Jiatong University in Chengdu. The research team is led by Zhong Lin Wang and has created a new kind of triboelectric nano-generator (TENG) – a form of technology that allows of conversion of mechanical and/or thermal energy into electricity. Nano-generators work on three principle methods; piezoelectric, triboelectric and pyroelectric. The former two deal with harvesting mechanical energy and the latter deals with harvesting of thermal energy. TENG features vertically free-standing strips that have been created from polyethylene terephthalate (PET) thin film – coated with indium tin oxide (ITO) on one side and nanowires on the other, thus allowing the electrons to jump between the two materials. The process is known as triboelectric effect.
The team’s research study was published in the journal, Advanced Materials. According to the publication, TENG-based wind energy harvesters, developed someplace else, made use of wind-induced membrane vibration for the electricity generation but are only beneficial when the wind blows in a particular direction. The project’s aim, therefore, was to tap into the energy potential of the erratic winds while also being able to take advantage of stable winds. The Southwest Jiatong University thus came up with a flexible TENG that is capable of harvesting energy from natural wind despite the erratic wind directions.
Team member, Weiqing Yang, said, “Compared with a wind turbine, our triboelectric nanogenerator (TENG) is effective at harvesting the energy from natural wind blowing in any direction. Yang further added that the polymer thin film material used in the gadget allows the gadget to be made available at a low cost while allowing for easy manufacturing and scaling up if needed.
Every flat array of TENG has a structure similar to that of a kelp forest thus allowing single strips to move independently and thereby creating a contact-separation process in response to the blowing wind. A high-speed camera was employed for capturing the working states and interaction between two TENGs that are adjacent. The strip was able to create vibration frequency of 154Hz thus allowing for a sufficient contact-separation for high electric output. When a 10 x 2 cm strip when subjected to an airflow velocity of 27m/s, the team learned that two adjacent strips covering a rooftop area of 2×0.7cm can provide an open circuit voltage of 98V, short-circuit current of 16.3µA and a power density of up to 2.76 Wm-2. This is enough power to light an advertisement hoarding.
Upon deploying an array, consisting of 60 strips, of TENGs on a rooftop, the team was able to generate a power density of up to 2.37 Wm-2. This is enough power to simultaneously light up 60LED bulbs that are connected in series.
The team has demonstrated that the TENG is able to provide substantial power when it comes to home electronics and is therefore, a reliable power source. The device has only been tested in the lab so far, so we’ll have to wait a while before it becomes consumer-ready.
