The bulk of Ellison's fortune comes from his 23.5 percent stake in Oracle, the world's largest database company. He also owns a 49 percent stake in NetSuite, as well as an interest in educational software maker LeapFrog Enterprises. He has an estimated $4 billion in cash and other assets, including numerous real estate properties.
Oracle Corp. Chief Executive Officer Larry Ellison plans to build one to power the Hawaiian island he bought last year. EBay Inc. has one to run a data center. The University of California at San Diego and the federal government have invested tens of millions of dollars in the technology.