Strategies for zero boil-off liquid hydrogen transfer: an export terminal case-study

TL;DR

This paper investigates two strategies to achieve zero boil-off losses in liquid hydrogen transfer at export terminals, emphasizing pump efficiency and tank pressure adjustments to optimize economic viability.

Contribution

It introduces and compares two transfer strategies using variable speed and fixed-speed pumps, highlighting the importance of pump efficiency and tank pressure in minimizing boil-off losses.

Findings

VSD pump with split-range control reduces losses to 0.24 wt%.

Fixed-speed pump has higher losses, up to 1.06 wt%.

Increasing tank pressure to 1.35 bara enables zero loss with fixed-speed pump.

Abstract

To ensure economic viability, LH2 export terminals must minimize boil-off losses. We show two strategies to achieve zero boil-off losses for the transfer of 160 000 m3 LH2 (11 248 tons) using a centrifugal pump. In the first strategy, a pump with variable speed drive (VSD) and split-range control for the flow rate achieves losses from 0 wt% to 0.24 wt% in an uncertainty analysis. A pump efficiency approaching 70% is the most important factor to minimize losses. In contrast, a fixed-speed pump has unacceptably high losses ranging from 0.76 wt% to 1.06 wt% (119 tons per ship). The second strategy is to increase the maximum pressure in the seaborne tank (base case is 1.15 bara). Zero loss is achieved for the fixed speed pump if the maximum pressure is increased to 1.35 bara, while 1.22 bara is required for the pump with VSD assuming an efficiency of 60%.