Flash memory

Flash memory cards are storage devices that store information on memory chips. Flashcards are often used in battery operated devices, where energy consumption is an important issue, such as MP3 players, digital photo and video cameras and in other portable devices such as cell phones and PDAs. Through card readers the flashcard data can be read in notebooks/PCs.
Their typical size is a large postage stamp. Storage capacity is typically 2 to 8 GB, while 64 GB has become recently available. Basic types are Compactflash, Smart Media, Multimedia, Secure Digital and Memory Stick. The memory device (NAND-Flash) mainly comes from Toshiba, Samsung or Hitachi. The only competing technology for this type of application is the miniaturized hard disk drive, where price per megabyte is still lower.


Power consumption during reading and writing ranges from 66-330 mW. Usually faster cards draw more power. However, they are still more energy efficient than hard disk drives (the current Hitachi 6 GB MicroDrive consumes about 750 mW at writing). Standby energy consumption is around 1 mW (Hitachi MicroDrive: 40 mW).
To compare flashcards on energy consumption you need both the power consumption and the data transfer speed. Reading energy consumption was between 0.15 and 0.4 Wh per Gb of data transferred. Writing energy consumption was between 0.3 and 1.5 Wh per Gb of data transferred. As a comparison: The MicroDrive used 1 Wh reading 1 Gb of data and 2 Wh writing 1 Gb.


In the coming years flash memory storage capacity will probably grow to match present hard disk drive capacity in notebooks. Actually, in notebooks where mobility is more important than storage space, they have already become the hard drive's substitute because of their low energy consumption. Alternatively they will become the preferred storage medium for various mobile products. Only the future will tell whether functionality of smartphones will be enough to convince mobile consumers not to buy a notebook anymore and/or leave the notebook at home to replace the desktop.

Courtesy of the French Energy Agency ADEME, Future Electronics project, expanded by VHK.