Energy electricity production

Two of these cycles have an electrolysis step. Although one of the purposes of the thermochemical cycles is to avoid electrolysis and the associated iaefftciencies of electricity production, the electrolysis steps proposed use much less electrical energy than water electrolysis. The Mark 13 is regarded as the most advanced thermochemical cycle, with overall efficiency of about 40%, including the electrolysis step (164). 

The widespread availabiHty of electrical energy completely transformed modem society and enabled a host of breakthroughs in manufacturing, medical science, communications, constmction, education, and transportation. Centralized fossil fuel-powered, steam-turbine-based power plants remain the dominant means of electricity production. However, hydropower faciHties such as the 1900-MW Hoover Dam Power Project located on the Arizona—Nevada border, commissioned by the U.S. Bureau of Reclamation during the 1930s, have also made significant contributions. 

Fig. 7. Biofuels and biomass electricity production. Courtesy of the National Renewable Energy Laboratory.

In the United States about 3 percent of all electricity produced comes from renewable sources of this a little more than half comes from biomass. Most biomass energy generation comes from the lumber and paper industries from their conversion of mill residues to in-house energy. Municipal solid waste also is an important fuel for electricity production approximately 16 percent ot all municipal solid waste is disposed of by combustion. Converting industrial and municipal waste into bioenergy also decreases the necessity for landfdl space. 

The main advantage of geothermal energy is that it can be exploited easily and inexpensively in regions where it is abundantly available in hydrothermal resen/oirs, whether it is used for electricity production or for dircct-usc heat. Gcothcrmally produced electricity from dry-steam sources is vei y cheap, second only to... 

Fuel cells are electrochemical devices transforming the heat of combustion of a fuel (hydrogen, natural gas, methanol, ethanol, hydrocarbons, etc.) directly into electricity. The fuel is electrochemically oxidized at the anode, whereas the oxidant (oxygen from the air) is reduced at the cathode. This process does not follow Carnot s theorem, so that higher energy efficiencies are expected up to 40-50% in electrical energy and 80-85% in total energy (heat production in addition to electricity). 

Heat from all the hot exhaust gas streams is used for steam generation to drive the steam turbine. Thus, the final products from the GE fuel-flexible process are pure hydrogen from the first reactor, C02 from the second reactor, and heat for electricity production from the third reactor. A portion of the solids in the chemical loops needs to be purged to avoid ash accumulation and maintain solid reactivity (Rizeq et al., 2002). The overall energy conversion efficiency for the GE fuel-flexible process is estimated to be 60% (Rizeq et al., 2003). 

An energy cost would also be paid for the processes that remove the sulfur along with environmental problems from disposing of it. About 5% more coal would be needed to keep electricity production from these power plants at current levels if most of the sulfur is scrubbed out. 

Figure 5.4. Renewable Energy Sources (RES) in electricity production in 2004 (IEA, 2007 IEA, 2006b).

In the area of wind offshore energy, Garrad Hassan et al. (1995) place the electricity production potential at 10904 PJ/year including areas with a distance up to 30 km from the coast and a water depth of less than 40 m. The EWEA (2003) and Greenpeace (2001) apply further constraints leading to a significantly lower value for the offshore electricity potential (see Fig. 5.6). In this way they restrict the area available for offshore production to a water depth of 20 m and reduce the capacity density. 

In most of today s ethanol plants for the conversion of wheat, rye and corn, the required thermal energy is provided by natural gas, heavy fuel oil or coal. The protein-rich by-products of ethanol plants are referred to as dried distillers grains with solubles , abbreviated as DDGS, and are mostly used for animal fodder. Alternatively, they can be converted to biogas for heat and electricity production. The resulting residue can then be used as fertiliser (see Table 7.16). 

The potential for renewable electricity production from wind and solar energy is by far higher than the potential for biomass production. Therefore, in the case of... 

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