Seatrec harvests energy from temperature differences in the environment to power underwater research, industry, and defense. OCEAN: Seatrec’s initial focus is a thermal engine to power underwater platforms, vehicles, and sensors in support of ocean research and national defense. Unmanned underwater platforms and vehicles accelerate ocean exploration and facilitate routine monitoring and surveillance – but require a source of electrical power for propulsion, navigation, data collection, and communications. Typically, this power is supplied by toxic and potentially hazardous lithium batteries of which several tons per year are discarded at sea. Seatrec has developed and patented a compact, modular thermal engine that extracts energy from the ocean’s vertical temperature gradient and converts it to electricity. Seatrec’s first product, the SL1 Thermal Engine, will support the family of 4000+ expendable, vertically-profiling robotic probes currently deployed in the global ocean as part of an international observing network. The SL1 can dramatically extend the operating lifetime of a profiling float — or enhance its utility through increased profiling rates and support of energy-intensive sensors for biogeochemical and acoustical studies. Variants of this system are currently being developed for integration with underwater gliders, moored profilers, and other high-endurance undersea platforms. ICE: Persistent observing systems are required to probe the coupled dynamics of atmosphere, ocean, and ice and associated biogeochemical and ecosystem processes in the pristine polar maritime environment. As in the ocean, lithium-chemistry batteries limit endurance and are associated with high operational costs, safety hazards and negative environmental impacts. In many circumstances neither wind nor solar are viable options for high-latitude applications due to contamination by snow and ice and by the inevitable darkness of polar winter. Seatrec is developing a novel environmental energy harvesting system that extracts thermal energy from the high-latitude air-sea temperature differential and converts it to clean, useful electricity (patent pending). This effort will result in a clean energy source that could fundamentally alter the logistics and economics of polar observing system operations. The air-sea thermal engine will support oceanographic and meteorological monitoring stations and buoys, navigational beacons, communication nodes, ice-based sensor packages, and satellite-to-acoustic data relays. The system will be compact, low-maintenance and capable of long-term deployment on a fixed platform, buoy, or ice floe – or on a mobile platform such as a drifting buoy or autonomous surface vehicle. LAND: Temperature differences on land occur in many forms, both temporal and spatial. Where permanent solar arrays or wind turbines are not appropriate, the diurnal (day-night) temperature differential at a specific location can be utilized to generate power for applications ranging from backcountry recreation to remote communications facilities to covert surveillance and border security. Terrestrial applications exploiting vertical temperature differences between the air, earth, and groundwater are also being explored to support residential, industrial, and defense energy requirements in remote, off-grid locations.