Density volumetric power

Volumetric power density W/dm3 (watt per cubic decimetre)... 

Planar SOFC, in particular, monolithic designs (MHI) are capable of high (volumetric) power densities most favoured by direct and short current paths across the stack components. The PEN is principally square, rectangular and circular (Ceramic Fuel Cells Limited (CFCL), Mitsubishi Materials Corp., SulzerHexis) in shape with active surface areas of 100-200 cm2 (15.5-31 in2). A drawback of this design is that it often necessitates the use of high temperature sealants for application at the in-... 

For most mobile applications size and weight of the fuel cell is very important. Automotive fuel cell stacks have gravimetric and volumetric power density >1 kW/kg and >1 kW/1, respectively. For smaller stacks <10 kW, power density is significantly lower. 

Another important criterion for the comparison of different storage technologies is the (gravimetric or volumetric) power density, which specifies how fast the electrode can be discharged or charged at a given mass or volume. 

The main advantages ofthe tubular design are good thermal cycles resistance and no requirement for high-temperature seals. In contrast, the planar geometry provides a higher volumetric power density. 

Cell design is also an important factor to improve the performance of SOFC stack/module [15-18]. Use of small diameter SOFC may also give opportunity to reduce operating temperature by increasing the volumetric power density [19]. Thus, they are expected to accelerate the progress of SOFC systems which can be applied to portable devices and auxiliary power units for automobile. 

The gases are distributed within the two compartments from channels on the bipolar plates. Bipolar plates can be made of carbon-based material or metal. The decision on the bipolar plate material and design depends strongly from the available space. By increasing the requirement of power density the metal bipolar plate are more suitable. The cell pitch of 1.2-1.5 mm can be manufactured to achieve a volumetric power density of 2 kW/1 or more. 

Apart from all the advantages, MFCs have technical challenges to overcome, and the most critical one is the low power density. The areal and volumetric power densities have improved by more than 10" and 10 folds in the past decade, and the highest areal power density of 7.72 W/m and volumetric power density of 3,320 W/m have been reported. Yet the areal and volumetric power densities are still about four orders of magnitudes lower than those of conventional lithium-ion battery. Thus enhancing the power density of microscale MFCs is critical. 

Output Current, Output Power, Areal/Volumetric Current Density, and Areal/Volumetric Power Density... 

Here imax, areah imax, volumetric Pmax, areab Pmax, volumetric are the areal current density, volumetric current density, areal power density, and volumetric power density, respectively. 

Figure 5a shows the Reynolds number and mass transfer coefficient as a function of characteristic length. As the characteristic length reduces, the Reynolds number decreases and mass transfer coefficient increases. Consequently, the areal current and power densities increase. Figure 5b shows areal and volumetric power densities versus the characteristic length scaling down from macro- to sub-microscale, both areal and volumetric power densities increase and then reach saturation points at 26.4 W/m and 1.16 x 10 W/m , respectively, based on the assumption that the theoretical maximum current density is 66 A/m. ... 

It is helpful to compare the areal and volumetric power density of prior art versus theoretical calculation in Fig. 5b. The maximum areal and volumetric power density of prior art are 7.72 W/m and 3,685 W/m, respectively. The areal power density is close to the theoretical prediction of 10 W/m, while the volumetric power density is approximately one order of magnitude lower than the theoretical prediction of 2.5 x lO" W/m (both of 250 pm characteristic length). This discrepancy may be due to the effective chamber volume that ultramicroelectrode is associated with. The geometrical chamber volume may not be fully utilized by ultramicroelectrode. On the other hand, performance of prior art microscale MFCs have varied significantly, which may be due to different setups, operation procedures, inoculum, etc. 

Microscale Microbial Fuel Cells, Fig. 6 Schematic of microscale MFCs (a) the first microscale MFC by Chiao et al. [1], which produced an areal power density of 5.72 nW/m (b) microscale MFC presented by Siu and Chiao [17], by applying micropillars to increase surface-area-to-volume ratio (elevated areal and volumetric power density of 4 mW/m and 40 W/m were achieved, respectively) (c) microscale MFC presented by Choi et al. [2], by reducing the distance between anode and cathode and mitigating oxygen leakage by adding L-cysteine (areal and volumetric power densities of 47 mW/m and 2,333 W/m ... 

Since the first microscale MFC has been reported, a significant improvement in power density has been achieved for a short period of time, less than a decade. Both the areal and volumetric power densities have improved by more than 10" folds, and microscale MFCs may become an attractive candidate on renewable and carbon-neutral green-energy converter. 

An integrated heat exchanger-reactor for methanol steam reforming was developed by Hermann et al. [65] at GM/OPEL for a 50 kW methanol fuel processor. The system specifications included a volumetric power density of more than 5 kW dm, a gravimetric power density of more than 2.5 kWkg and a transient response to load changes from 10 to 90% in milliseconds. 

The reactor core of the QP300 consists of 121 fuel assemblies of the 15 x 15 type with an active fuel length of 2.90 m. The average volumetric power density of the core is 70.9 kw/1. 

Liquid-cooled stacks have higher volumetric power density and they are preferred when the output power is around 5 kW or higher. The resulting fuel... 

As a key module of the fuel cell system, the performance and reliability of the stack is crucial. As a world leader, Ballard Power Systems (Canada) has spent many years developing stacks. Table 6.7 lists the basic parameters of Ballard9 SSL stacks. At a rated power of 21.0 kW (current is 300 A), the specific and volumetric power densities of the stack are 1.24 kW kg and 1.52 kW H, respectively. 

The mean volumetric power density of a DT fusion reactor depends on the plasma power density B ) and the sum of the volumes... 

If a linear relation between the volumetric power density and neutron wall load is assumed, extrapolation of the data from the two fusion reactor designs yields the curves shown in Fig. 10, where the dependence of the blanket volume on the power density is ignored (optimistic extrapolation ). Compacting the construction beyond a certain limit is achieved at the expense of complexity and availability. The upper compacting limit is characterized by the so-called most compact tokamak reactor (A = 3 r = b = 1.75 m), whose power refers to the sum of the net volumes of the plasma vessel and the outer system (b), which comprise the blanket,... 

This type of H2-fed fuel ceU, due to its high achievable specific and volumetric power density (in the range of 1 kW/kg and 1 kW/1 and above), its cold start behavior, and its fast load following properties, has found the interest of automotive industiy and is under development by aU major automotive companies. 

Worldwide interest in DMFCs is increasing due to their high volumetric power density which makes them ideal candidates to replace Li-ion batteries in mobile devices. Since 1991, the number of publications on DMFC science... 

A typical laboratory fuel cell generates power in the range of 10-100 W. To increase the power of the FC system and to achieve high volumetric power density, fuel cells are assembled in stacks. A stack is a layered structure consisting of membrane-electrode assemblies (fuel cells) clamped between metal or graphite bipolar plates (BPs) with channels for feed gas supply (Figure 5.1). 

Average volumetric power density of the core, kW/litre 140 ... 

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