Efficiency of energy conversion

The power efficiency of a photoelectrode ean be eharaeterized by the open-circuit potential (OCP) and short-circuit current  

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Research is being done in the United States and worldwide to lower some ot the barriers to biofuels. Researchers hope to develop high-yield, fast-growing feedstocks for reliable biomass fuel supplies. Research is also being done to improve the efficiency of energy conversion technologies so that more of the biomass is utilized. 

This is the efficiency of energy conversion between mechanical and electrical forms. For PZTs, it ranges from 0.5 to 0.7, which are the most efficient of all known piezoelectric materials (see Table 9.1). For quartz, the coupling constant is about 0.1. 

The efficiency of energy conversion in the polymers, i.e. how much the change in shape of the chain is induced by a photon, is, however, rather low. They need many photons and a high content of pendant photochromic chromophores to induce a large conformation change. To make a sensitive photo-responsive polymer, i.e. one which responds more efficiently to fewer photons, it is necessary to introduce an amplification mechanism to the system. One possible way of achieving this is to utilize the phase transition of polymers [7,8]. 

The HEI describes the amount of energy required to haul 1 kg of the vehicle over a distance of 1 km. The HEI is a measure of efficiency - it is the inverse of a vehicle L divided by the weight of the vehicle (b) Increase the efficiency of energy conversion devices such as the engine, fuel cell, electric motor and gasoline... 

A surface of p-InP was modified by the electrodeposition of submonolayer amounts of various metals and the photocurrent vs. potential behavior studied. The photocurrents observed at 0 V vs. NHE for various surface treatments are shown in the Table E.2. Calculate the maximum efficiency of energy conversion in each case and comment on the observed trend. The light source was an Xe lamp and incident light intensity was 50 mW cm-2. (Contractor)... 

So, a hypothetical super fuel cell would have i0 10-3 A cm-2. The efficiency of energy conversion at practical power densities could be greater than 90%, and limiting currents 104 times the limiting current densities at planar electrodes giving power densities up to 1 W cm-2. Let us see to what degree real fuel cells approach these hypothetical ideals. 

In practice, in all fuel cells that involve the utilization of 02 from air (Section 13.4.5), the oxygen reduction reaction [Eqs. (13.4) and (13.24)] is always rate determining for terrestrial applications. One can seejust how important it is to attempt to develop electrocatalysts for the cathodes of fuel cells on which the enhanced current density is high and Tafel slope is low and the efficiency of energy conversion, therefore, maximal. The direct relation of the mechanism of oxygen reduction and the associated Tafel parameters to the economics of electricity production and transportation is thus clearly seen. 

The efficiency of energy conversion and utilisation in this process cannot be evaluated based on first lau of thermodynamics alone and true energy dissipations can be brought out by using available energy analysis. 

Khalifa, H. E., "Towards a Systematic Definition of the Thermodynamic Efficiency of Energy Conversion Systems,"... 

Equation (7.80) may be called the efficiency of energy conversion. When jjXj shows the input and JpCq the output power, then diffusion drives the heat flow. Since 7jX is zero when either J" orXq is zero, then it must pass through a maximum at an intermediate value. The values of 7jX are often small in regions of physical interest, and the maximum value depends on the degree of coupling only... 

Efficiency of Energy Conversion of a Reaction-Diffusion System... 

However, the hydrolysis of ATP can pump the ions only if some degrees of coupling exist between the reaction velocity and the mass flow. The efficiency of energy conversion for pumping a substrate with the help of a chemical reaction may be related to the degree of coupling by using Eq. (9.105)... 

Only a small part of the initial free energy of photons is available for photosynthesis, and the rest is dissipated. The efficiency of energy conversion in photosynthesis is low and varies in the range 2.4 7.5% (Andriesse and Hollestelle, 2001). The efficiency of energy conversion is defined by... 

The efficiency of energy conversion as a ratio of output energy to input energy is related to the degree of coupling as follows... 

Noteworthy is the efficiency of energy conversion of these spirobenzopyran rubbers 4>, i.e. the ratio of the contraction work to the energy of absorbed light. For irradiation periods of 60 s the mean value of 0e is 0.86% independent of the irradiation wavelength between 500 and 600 nm. Calculated on the initial rapid contraction phase it is equal to 2%. 

Efficiency of Energy Conversion under Polychromatic Radiation... 

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