Storyline: Southern Chinese tech hub Shenzhen energized as leading portable energy storage maker [Voice_over] Southern China's Shenzhen city, home to four of the world’s top five portable energy storage companies, is securing its place a global leader in the sector. About the size of a small toaster, portable energy storage systems like these are great for outdoor activities or for businesses or homes to use as a backup energy source. This model maintains 70 percent of its capacity even after 4,000 charges. Engineers at the company that make it say typically, to increase capacity in a portable energy storage unit, it need more components, which makes it heavier. To overcome this hurdle, the company's research and development team got creative with battery placement to make a product that's 41 percent smaller yet 35 percent lighter than similar capacity products. [Sound_bite] Chen Wenyang, Senior Manager, Portable Product Center, Hello Tech: "We fixed the battery cells directly onto the product base, saving internal space and enabling a more compact design." [Voice_over] From main control chips, to capacitors and plastic parts, all the parts for an energy storage unit are sourced within the Pearl River Delta region, which allows for short procurement cycles and significant cost savings. [Sound_bite] Lei Jianhua, Executive Vice President, Shenzhen PowerOak NewEner Co., Ltd.: "Our entire supply chain is based in the Pearl River Delta. We can cut procurement cycles to as short as 10 days, reducing costs by up to 30%." [Voice_over] The are currently some 7,000 energy storage companies now based in Shenzhen. [Restrictions : No access Chinese mainland]