In Lost Planet 3, you won't need to collect thermal energy to stay alive, heal, or power your mech suit or energy weapons, unlike in previous instalments; thermal energy is now the currency used to buy weapons and upgrades. You acquire it by killing Akrid enemies or, in a new resource-gathering gameplay element, by planting thermal posts and returning later to harvest the heat.
At E3, the makers of the game discussed the new thermal energy farming system in a demo in which Jim, Lost Planet 3's civilian mech pilot hero, explored a network of caves and icky alien nests, replete with exploding eggs and the skittering, three-legged Akrid creature, Sepia, encountered in earlier games. By fighting his way to the heart of the tunnel complex, armed with a pistol and an old-timey hunting rifle (a family heirloom, says Capcom producer Andrew Szymanski), Jim reclaimed an abandoned thermal post, planted long ago and overgrown with alien gunk.
The post then became a collection point for thermal energy. Energy at posts like these accumulates in real time as Jim is elsewhere battling Akrid foes. You can return to the posts to harvest the energy they have gathered; the longer you leave a post to ripen, the more energy you will receive, but the harder it will be to recover--because Akrid, attracted by warmth, will begin to nest around them.
Players will spend more time on foot, in third-person shooting segments like that of the demo, than in the game's characteristic mech suits. Szymanski gauges the ratio of on-foot to in-mech action as 60:40, though that will vary, of course, according to player choices; on open terrain (as opposed to interior environments), players can choose to hop out of their bipedal robot rig whenever they like. The gameworld is large, though not fully open ("This isn't Skyrim," says Szymanski), but fast travel will be available to take you part of the way to, for instance, a thermal post ready for harvesting.