Extending the lifetime of fuel cell based hybrid systems

ACM Trans. Des. Autom. Electron. Syst.

et al. 2008

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This article presents our work on the development of a fuel cell (FC) and battery hybrid (FC-Bh) system for use in portable microelectronic systems. We describe the design and control of the hybrid system, as well as a dynamic power management (DPM)-based energy management policy that extends its operational lifetime. The FC is of the proton exchange membrane (PEM) type, operates at room temperature, and has an energy density which is 4-6 times that of a Li-ion battery. The FC cannot respond to sudden changes in the load, and so a system powered solely by the FC is not economical. An FC-Bh power source, on the other hand, can provide the high energy density of the FC and the high power density of a battery.In this work we first describe the prototype FC-Bh system that we have built. Such a prototype helps to characterize the performance of a hybrid power source, and also helps explore new energy management strategies for embedded systems powered by hybrid sources. Next we describe a Matlab/Simulink-based FC-Bh system simulator which serves as an alternate experimental platform and that enables quick evaluation of system-level control policies. Finally, we present an optimization framework that explicitly considers the characteristics of the FC-Bh system and is aimed at minimizing the fuel consumption. This optimization framework is applied on top of a prediction-based DPM policy and is used to derive a new fuel-efficient DPM scheme. The proposed scheme demonstrates up to 32% system lifetime extension compared to a competing scheme when run on a real trace-based MPEG encoding example.

Section: Fcs For Human-portable Applicationsmentioning

confidence: 99%

A fuel-cell-battery hybrid for portable embedded systems

Lee

Chang

ACM Trans. Des. Autom. Electron. Syst.

et al. 2008

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“…The FC system efficiency can be treated as a constant in the load following range 0.3 A-1.2 A (the efficiency variation is within ±3). This is the configuration that was used in [10,11].…”

Section: Fc System Efficiencymentioning

confidence: 99%

“…FCs have limited power capacity, i.e., their power range is limited. Thus a hybrid power source composed of an FC that has high energy density and a secondary power source (such as battery or super capacitor) with high power density is much more efficient [9,10].…”

Section: Introductionmentioning

confidence: 99%

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Dynamic power management with hybrid power sources

Proceedings of the 44th Annual Conference on Design Automation - DAC '07

Chakrabarti

Lee

et al. 2007

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DPM (Dynamic Power Management) is an effective technique for reducing the energy consumption of embedded systems that is based on migrating to a low power state when possible. While conventional DPM minimizes the energy consumption of the embedded system, it does not utilize the properties of the power source. Alternative power sources such as fuel cells (FCs) have substantially different power and efficiency characteristics that have to be taken into account while developing policies that maximize their operational lifetime. In this paper, we present a new DPM policy for embedded systems powered by FC based hybrid source. We develop an optimization framework that explicitly considers the FC system efficiency and is aimed at minimizing the fuel consumption. Next we apply this optimization framework on top of a prediction based DPM policy to develop a new fuel-efficient DPM scheme. The proposed algorithm was applied to a real trace based MPEG encoding example and demonstrated up to 32% more system lifetime extension compared to a competing scheme.

“…In our prior work, we have proposed FC-aware algorithms when the FC works at a fixed output level [15] as well as when the FC works at multiple output levels [16]. While in both cases, the voltage scaling level of the CPU is a function of the power model of the embedded system and the power state of the hybrid source, the work in [16] allows fuel flow control and results in additional fuel savings.…”

Section: Introductionmentioning

confidence: 99%

Energy management of DVS-DPM enabled embedded systems powered by fuel cell-battery hybrid source

Proceedings of the 2007 International Symposium on Low Power Electronics and Design

Chakrabarti

Chang

2007

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Dynamic voltage scaling (DVS) and dynamic power management (DPM) are the two main techniques for reducing the energy consumption of embedded systems. The effectiveness of both DVS and DPM needs to be considered in the development of an energy management policy for a system that consists of both DVS-enabled and DPM-enabled components. The characteristics of the power source also have to be explicitly taken into account. In this paper, we propose a policy to maximize the operational lifetime of a DVS-DPM enabled embedded system powered by a fuel cell-battery (FC-B) hybrid source. We show that the lifetime of the system is determined by the fuel consumption of the fuel cell (FC), and that the fuel consumption can be minimized by a combination of a load energy minimization policy and an optimal fuel flow control policy. The proposed method, when applied to a randomized task trace, demonstrated superior performance compared to competing policies based on DVS and/or DPM.