Net power density

The intensity of the process or the effectiveness in making small droplets is often governed by the net power density (c(t)) ... 

Feasibility is strongly related to the net power density of the nuclear island and the system complexity. As a rule in energy technology, increased... 

Power plant properties Suitability criteria Reactor configu- ration Net power density of the nuclear island System com- plexity Circu- lating power Fuel cycle... 

This derivation highlights several key features of solid-state laser refrigeration. First, Eq. (12) shows that the pump absorption coefficient diminishes exponentially as the temperature is lowered, which is a result of the thermal depletion of the initial state II). This reduces the net power density that can be extracted from the solid (Eq. 11) and ultimately sets a lower limit for the temperature that can be reached by laser cooling. Finding materials with a small ground-state crystal-field sphtting 5Eg) is advantageous in this respect. 

Along with electronic transport improvements must come attention to substrate transport in such porous structures. As discussed above, introduction of gas-phase diffusion or liquid-phase convection of reactants is a feasible approach to enabling high-current-density operation in electrodes of thicknesses exceeding 100 jxm. Such a solution is application specific, in the sense that neither gas-phase reactants nor convection can be introduced in a subclass of applications, such as devices implanted in human, animal, or plant tissue. In the context of physiologically implanted devices, the choice becomes either milliwatt to watt scale devices implanted in a blood vessel, where velocities of up to 10 cm/s can be present, or microwatt-scale devices implanted in tissue. Ex vivo applications are more flexible, partially because gas-phase oxygen from ambient air will almost always be utilized on the cathode side, but also because pumps can be used to provide convective flow of any substrate. However, power requirements for pump operation must be minimized to prevent substantial lowering of net power output. 

The behavior of fuel cells in terms of individual and overall voltage as function of current density represents the basic performance from which an overall efficiency evaluation has to start. The impact of the parasitic consumption of auxiliary components involved in the system management strategies on the net power produced by the fuel cell stack represents the second important step to be carefully evaluated. 

Fuel cell performance of the composite LSM-YSZ/YSZ/Ni-YSZ cell was investigated using forming gas (10 vol% H2 in N2) as the fuel (Figure 3-25). The results showed that a maximum power density of about 0.26 W cm2 as obtained at a temperature of 850°C. The temperature dependence of the area specific resistances of the asymmetrical cell is shown in Figure 3-26. The electrode overpotential was estimated to 0.3 Q cm2 at 800°C, which is the total of anode and cathode overpotential. It appeared that about half of the overpotential originated from the anode, because the cathode overpotential determined from the symmetrical cell test was found to be about 0.14 Q cm2 at 800°C. The performance of the cell was mainly limited by the electrolyte resistance. The decrease in the electrolyte thickness would decrease electrolyte resistance. It can be concluded that the net shape technology can be successfully applied for the fabrication of cathode and anode electrodes. 

It was pointed out in the section on gas coolants that the heat removal capacity of helium or CO2 could be made equivalent to that of sodium by choosing appropriate coolant pressure and flow rate conditions for the gas coolant. The studies on the GCFBR have shown that the heat transfer with oxide fuel elements is not limited by the coolant when the coolant pressure is 1000 psia. Under these conditions, it is found that a net plant efficiency of 40 % can be obtained in a large GCFBR having a fuel rating of 900 kW/kg of fissile fuel, a power density of 240 kW/liter, an overall conversion ratio 1.55, and a doubling time of 8 years (see Table I). 

If the net electric power density pei of the tokamak reactor is defined as the quotient of the plant net electric power Pei and the volume Ve which... 

Resume IT CAN BE DRAWN FROM RECENT REACTOR DESIGN STUDIES, THAT THE MEAN VOLUMETRIC NET ELECTRIC POWER DENSITY IN TOKAMAK REACTORS WOULD ONLY BE 2.5 to 4% OF THE VALUE COMMON TODAY IN LIGHT WATER REACTORS AND THAT A TOKAMAK REACTOR WOULD REQUIRE ABOUT 12 kg OF CONSTRUCTION MATERIAL PER kW j TO BE BUILT, OR A FACTOR OF 17 MORE THAN FOR THE LIGHT WATER REACTOR. 

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,... 

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