Overview

Due to the unprecedented growth in the offshore wind, wave and tidal power generation industries and the continued ubiquity of offshore oil and gas installations, the technological limits of remotely operated vehicles (ROVs), autonomous unmanned vehicles (AUVs) and fixed sub-sea support and production equipment are being pushed further than ever.

Sub-sea application such as ROVs, AUVs and many fixed installations invariably require an electrical power source. While the required power may be fed from surface level via an umbilical cable, it is well known that this methodology has several drawbacks such as high reliance on support vessels, limited reliability and restricted operating scope.

There is an increasing need to solve the challenges of current power solutions and improve the capabilities of underwater power sources. With research, experiment and testing, Altertek have developed an alternative approach to designing the subsea power source. This approach tackles many of the challenges currently faced and is working on an effective power source at 3,000 meters underwater.

Problem Definition

One key aspect of sub-sea system design that has significant scope for improvement is the power source. Existing power source solutions often require the use of an umbilical to feed electrical or hydraulic power from surface-level to the sub-sea application or sub-sea hydraulic accumulators.

While these current techniques can be effective, they have significant drawbacks. Poor reliability or high levels of reliance on costly support vessels are of primary concern. Alternatively, sealed, pressure tolerant housings that contain batteries can be used. This approach is appropriate for small, low power applications. But, as the quantity of energy stored increases so does the high cost, complexity and size of pressure housings that are suitable for deep-water use, as such, the ‘pressure contained’ methodology only permits small quantities of energy to be stored.

Among the key areas of continued advancement are overall system reliability, system autonomy and operating cost reduction. Therefore, a cost-effective way of achieving marked improvements over existing technologies in these areas would bring significant benefits to the Original Equipment Manufacturers (OEMs), integrators and operators in the offshore oil, gas and renewable energy sectors.

Solution

A solution was needed to overcome the inherent issues associated with existing technologies for a large scale, deep and shallow water applications. It required a modular lithium-ion (li-ion) battery system, which could be configured as a very large capacity, high reliability battery with exceptional power output.

The battery needed to be pressure tolerant to avoid the use of pressure containment housings but also combined with suitable pressure tolerant electronics to fully monitor and control the battery. Communication with the battery monitoring system needed to be developed in a way to provide fully autonomous battery management. Finally, the battery system would need to be fully qualified for sub-sea use to a depth of up to 3,000 meters and be subjected to a comprehensive test programme to verify its long-term performance, reliability and abuse tolerance.

Altertek have researched and developed a high power, high reliability, pressure tolerant lithium-ion battery system. The battery system is scalable in capacity from just a few watt-hours up to 600kWh and is capable of repeatably delivering up to 200kW of power. The custom designed sub-sea battery therefore affords improved agility, mission duration, reliability, operating range and reduced operating costs to a vast array of sub-sea applications.

Scope of the Research Paper

Key aspects of the extensive research carried out to develop the new battery and battery management system will be available in the research paper, to be released by Altertek, during summer 2018.

To be placed on the waiting list to receive this paper once it is released please email marketing@altertek.com

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