Ultra-Low-Maintenance Portable Ocean Power Station

NASA’s Jet Propulsion Laboratory, Pasadena, California

The goals of this research are to develop a relatively inexpensive, compact, and modular power package for deep offshore oil drilling or other undersea applications that provides 2 to 5 MW electricity, minimal maintenance, and at least 30 years of life.

The ultra-low-maintenance portable ocean power station.

It is too expensive to provide power packages that sit on the deep ocean floor (typically 3-km deep), and it is too expensive to supply fuel and oxidizer to this deep equipment. It is also too expensive to run power cables from shore or from offshore platforms that are many tens of kilometers long. Traditional internal combustion generators, such as diesel generators or turbine generators, require considerable maintenance about once a month, which is far too expensive. The answer is to provide very-low-maintenance (once per year) fuel cell generators that are remotely floated near the deep wells, such that shorter power cables can be supported by anchor lines attached to the floatation device.

A barge is used to support an internal fuel cell (solid oxide or molten carbonate preferred, incorporating internal fuel processing) and a year’s supply of liquefied natural gas (LNG). Heat generated by the fuel cell system can be used in partial fulfillment of the energy required to vaporize the LNG in the integrated power system to increase the efficiency beyond the high efficiency provided by the fuel cell. Submerged buoys are attached to the anchor lines so that the power and anchor cables can be removed during a storm and yet float beneath the ocean surface, and the portable power barge can be towed to a harbor. Relatively simple annual maintenance, such as filter cleaning, is necessary for the fuel cells, so this type of maintenance can be performed in situ or in a harbor.

The barge can also be partially filled with seawater to allow the vessel to sink partly during storms, or the anchor lines can be made tighter to completely submerge the floating vessel during hurricanes. Air purification and fuel tanks are located on top of the barge to facilitate maintenance. For very long operation in rough seas, the heavier LNG tanks could be located below the barge, and the fuel cells could be above or below the barge.

A hybrid power system may be created in which fresh water produced by the fuel cells is used to generate power in a pressure-retarded osmosis (PRO) unit when integrated with seawater.

This work was done by Jack A. Jones and Gerald E. Voecks of Caltech for NASA’s Jet Propulsion Laboratory. NPO-49330