Adata showed off a solar powered model at Computex, though the solar cells only power the small LCD display - but as this only draws tiny amounts of power to show you how much capacity you've got left, there's no need for a battery. Besides the solar powered display, there isn't much to this product - it's available in sizes from 128MB to 1GB and should be available shortly. Adata was also showing a similar device using an electronic paper display. This model also shows a small pie chart graph and digital representation of how much space is left.