# OTEC and salinity power: Resources and labour

Rivers of seawater, kilometre-long pipes and vast membrane areas

Source page: https://www.materialinsights.org/energy/e_otec/resources/

What this tab covers The natural resources (land, water, materials, fuel or feedstock) and the labour needed to capture this energy, per unit, with the reason each is needed.

OTEC needs very large seawater flows, pipes and heat exchangers; salinity plants need enormous membrane areas and both fresh and salt water.

#### Natural resources

| Resource | How much | Why it is needed |
|---|---|---|
| **Seawater** | About 100,000 m3 an hour for a 10 MW OTEC plant^[1](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2014/Ocean_Thermal_Energy_V4_web.pdf) | Each cubic metre carries little usable heat across a 20 °C gap. |
| **Cold-water pipe** | About 10 m diameter and 1,000 m long for 100 MW^[1](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2014/Ocean_Thermal_Energy_V4_web.pdf) | Cold water must come from about 1 km down with little warming. |
| **Heat exchangers** | USD 200-800 per m2^[1](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2014/Ocean_Thermal_Energy_V4_web.pdf) | Small temperature differences need very large surfaces; they must resist corrosion and biofouling. |
| **Membranes (salinity)** | At least 2 million m2 for a 2 MW plant, replaced about every 5 years^[2](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2014/Salinity_Energy_v4_WEB.pdf) | Power per square metre is low, so area must be huge. |
| **Fresh water (salinity)** | Not quantified^[2](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2014/Salinity_Energy_v4_WEB.pdf) | River water or treated sewage provides the low-salt side; it is returned, not consumed. |

#### Labour

| Phase | How much | Skills | Why it is needed |
|---|---|---|---|
| **Manufacturing** | Not quantified^[1](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2014/Ocean_Thermal_Energy_V4_web.pdf)^[2](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2014/Salinity_Energy_v4_WEB.pdf) | Heat-exchanger and membrane manufacturing | These components dominate cost. |
| **Construction** | Not quantified^[1](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2014/Ocean_Thermal_Energy_V4_web.pdf) | Offshore pipe installation, marine engineering | A 10 MW cold-water pipe of 4-7 m diameter has not yet been demonstrated. |
| **Operation** | Not quantified^[1](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2014/Ocean_Thermal_Energy_V4_web.pdf)^[2](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2014/Salinity_Energy_v4_WEB.pdf) | Plant operators, membrane cleaning | Biofouling must be controlled continuously. |
| **Decommissioning** | Not quantified^[1](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2014/Ocean_Thermal_Energy_V4_web.pdf) | Marine salvage | Pipes and moorings must be recovered. |

No studies of jobs per MW were found for either technology.

#### Sources

1. [Ocean Thermal Energy Conversion: Technology Brief](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2014/Ocean_Thermal_Energy_V4_web.pdf) IRENA, 2014
2. [Salinity Gradient Energy: Technology Brief](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2014/Salinity_Energy_v4_WEB.pdf) IRENA, 2014

## Other sections

- [Summary](https://www.materialinsights.org/energy/e_otec/index.md)
- [Overview](https://www.materialinsights.org/energy/e_otec/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_otec/correlation/index.md)
- [Efficiency](https://www.materialinsights.org/energy/e_otec/efficiency/index.md)
- [Techniques](https://www.materialinsights.org/energy/e_otec/techniques/index.md)
- [Impact on the biosphere](https://www.materialinsights.org/energy/e_otec/biosphere/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_otec/links/index.md)