The Fusion Energy Plant produces energy by fusing atoms together. This type of energy is even more efficient than the Fission Energy Plant on a waste per energy produced ratio. Requires a high level University to construct. The higher the building level the more energy is produced.
Unfortunately the fusion plant produces enormous amounts of heat as well which requires coolants such as molten lead or salt. Therefore you'll need a good supply of galena or halite to build one.
Required Galena or Halite (varies by species):