# Ocean thermal gradient

The temperature gap between warm surface water and cold deep water.

Source page: https://www.materialinsights.org/energy/e_ocean_thermal/

Natural sources · Solar-derived flows · No. 6

- Natural sources
- Origin: Indirect solar
- Renewable: Yes
 Natural sources · Solar-derived flows · Foundation · Energy

In tropical seas, warm surface water sits a kilometre above water near 4 °C, and that gap can run a power plant.

Chart: Illustration: Ocean thermal gradient

##### Where it comes from

Chart: Map of where it comes from

The tropical Sun heats the top layer of the ocean while water a kilometre down stays near 4 °C; a heat engine runs on the roughly 20 °C gap.

##### Three things to know

1. IRENA counts at least 98 nations and territories with an ocean thermal resource.
2. Micronesia's estimated resource is 1,134 TWh a year, far more than its small population could use.
3. Steep island slopes matter because they put water 1,000 m deep within a short pipe of the shore.

##### The journey

1. 1 **Sun-warmed surface**Tropical seas held at 25-30 °C
2. 2 **Cold deep water**Near 4 °C about a kilometre down
3. 3 **Long pipes**Pump warm and cold water to shore
4. 4 **Heat engine**The temperature gap drives a turbine
5. 5 **Island power**Steady supply for diesel-dependent islands
 Covered in [Earth's energy flows: sun, wind, water, heat and lifeEnergy](https://www.materialinsights.org/learn/energy/earths-energy-flows/)

##### Go deeper pick a tab to open it in full

## Other sections

- [Overview](https://www.materialinsights.org/energy/e_ocean_thermal/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_ocean_thermal/correlation/index.md)
- [How energy resides](https://www.materialinsights.org/energy/e_ocean_thermal/resides/index.md)
- [Abundance](https://www.materialinsights.org/energy/e_ocean_thermal/abundance/index.md)
- [Fluctuation in time](https://www.materialinsights.org/energy/e_ocean_thermal/time/index.md)
- [Across the Earth](https://www.materialinsights.org/energy/e_ocean_thermal/geography/index.md)
- [Impact on nature](https://www.materialinsights.org/energy/e_ocean_thermal/nature/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_ocean_thermal/links/index.md)