Optimal design of power hubs for offshore petroleum platforms

Abstract

Even though advanced power generation systems offer higher efficiencies than simpler gas turbines, severe area and weight restrictions keep on impeding their widespread implementation in offshore petroleum industry. If those restrictions could be resolved, the performance of the utilities systems on offshore platforms may be drastically enhanced. In order to overcome these practical limitations, the installation of a power hub is proposed to centralize the energy supply required by a number of floating production, storage and offloading units (FPSOs). However, many challenges are still brought to companies contemplating this approach, such as incremental costs and prolonged offdesign operating conditions. This circumstance renders necessary to determine the optimal number, layout and operating load of the modular power units on the hub. Thus, in this work, a computational framework is developed to assist in the selection of the most suitable hub setups, so that the trade-off between higher overall efficiency and lower investment cost can be elucidated. This framework consists of a group of subroutines that evaluates, compares and ranks alternative offshore utility systems in terms of well-defined objective functions, whereas is subject to restricted weight and space allowances. As a result, the power hub configurations based on the largest bottoming cycles benefit from the economies of scale, as well as from an increased efficiency, if compared to other designs based on smaller bottoming cycles. Levelized costs of electricity reaches 40 USD/MWh when only gas turbines are installed, which can be reduced by 13% if combined cycles are preferred. The weight-to-power ratio of the hubs based on combined cycles remains 12–28% higher than that of the conventional setup, whereas the efficiency increase achieves up to 7 percentage points.