Analysis of stationary fuel cell dynamic ramping capabilities and ultra capacitor energy storage using high resolution demand data

Abstract

Current high temperature fuel cell (HTFC) systems used for stationary power applications (in the 200-300 kW size range) have very limited dynamic load following capability or are simply base load devices. Considering the economics of existing electric utility rate structures, there is little incentive to increase HTFC ramping capability beyond 1 kWs −1 (0.4% s −1 ). However, in order to ease concerns about grid instabilities from utility companies and increase market adoption, HTFC systems will have to increase their ramping abilities, and will likely have to incorporate electrical energy storage (EES). Because batteries have low power densities and limited lifetimes in highly cyclic applications, ultra capacitors may be the EES medium of choice. The current analyses show that, because ultra capacitors have a very low energy storage density, their integration with HTFC systems may not be feasible unless the fuel cell has a ramp rate approaching 10 kWs −1 (4% s −1 ) when using a worst-case design analysis. This requirement for fast dynamic load response characteristics can be reduced to 1 kWs −1 by utilizing high resolution demand data to properly size ultra capacitor systems and through demand management techniques that reduce load volatility.

Load-following active power filter for a solid oxide fuel cell supported load

“…Instead the load is approximated by looking at general trends and behaviors. As shown in [2], commercial office buildings tend to have two distinct load levels: off-use and on-use. The transition between the levels occurs in the early morning when the air conditioning system starts up to condition the building for the day.…”

“…One illustrative example of this occurs during sudden load changes. Load increases and decreases may occur during the start and stop of a large load with cycling behavior, such as an air conditioning compressor motor or arc furnace [2]. A voltage sag can accompany a sudden surge of inrush current, which may disrupt functionality or cause failure in delicate equipment on a neighboring circuit.…”

On control concepts to prevent fuel starvation in solid oxide fuel cells

“…When the anode dynamics are also considered, the reference governor model will need to simulate the response of the hydrogen mole fraction due to a change in the power demand. This problem is formulated as a constrained maximum where the goal is to find the maximum β∈ [0,1] such that the hydrogen mole fraction constraint is not violated:…”

“…A fast fuel cell system will allow use in a larger number of applications and can also limit the undesirable dynamics put onto the utility grid, which often is an important barrier to greater fuel cell adoption [1]. Various control concepts to prevent hydrogen starvation that result in different transient capabilities are investigated herein.…”

Fuzzy Optimal Energy Management for Fuel Cell and Supercapacitor Systems Using Neural Network Based Driving Pattern Recognition

“…INTRODUCTION NERGY crisis, environmental pollution and global warming cause fuel cells (FCs) powered vehicles to draw a lot of attention due to their high reliability and low pollutant emission [1]. However, due to slow dynamic response and limited load following capability, hydrogen starvation may occur at power fluctuations, which is impermissible for vehicles [2]. Energy storage devices, such as batteries or capacitors, are usually hybridized by a fuel cell bank as a power buffer during climbing, acceleration and braking [3][4].…”