Electrical energy from thermal

Ileri, A., Reistad, G. M. and Schmisseur, W. E., "Urban Utilization of Waste Energy from Thermal-Electric Plants," Trans. ASME J. Eng. Power, 98, 309 (1976). 

The conventional generation of electrical energy from a fuel requires the use of a heat engine which converts thermal energy to mechanical energy. All heat engines operate by the Carnot cycle, and their maximum efficiency is about 40-50% (for the modern gas-fired power stations, the efficiency is about 55%). 

The PassPort system from Altea Therapeutics uses a thermal process to create an array of macropores across the stratum corneum. The device consists of a planar array system of small metallic filaments that rapidly converts electrical energy to thermal energy. The heat ablates the stratum corneum for a few milliseconds at a time and porates only the stratum corneum. After skin poration with this process, drug absorption occurs from a drug reservoir on the porated site. Hydromorphone and insulin delivery with this method is currently under human clinical testing. 

The overall energy efficiency of densification systems may be misleading. Only 10 to 25of input energy is lost in making a biomass fuel pellet, even if electrical energy is thermally generated from the same residue when used as feedstock. 

An initial cost analysis was completed in [56] to determine the effects of the electricity price on hydrogen costs. For each electrolyzer, the specific system energy requirement was used to determine how much electricity is needed to produce hydrogen. At current electrolyzer efficiencies, in order to produce hydrogen at lower values than US 3.00/kg, electricity costs must be lower than 4//kWh. In a developing country without oil, such as Uruguay, the electricity costs from thermal devices are nearly US 1/kWh, so the inferences have to be very different. 

Figure 1.2 The relationship between chemical energy and other forms of energy, with examples. Note that a reaction can have energy transferred to or from several types of energy, as in the conversion of chemical energy into electrical energy and thermal energy.

Figure 2.11 Comparison of the primary energy usage for ethanol/water separation using traditionai distillation/adsorption process (Fig. 2.9) and hybrid membrane-assisted vapor stripping (MAVS Fig. 2.10) process. Minimum energy (from minimum work calculation) shown as reference. Assumptions 37% and 85% efficient conversion of primary energy to electrical energy and thermal energy, respectively, 0.02 wt% ethanol in stripping column bottoms, and 99.5 wt% ethanol product (0.5 wt% water).

The Seebeck effect corresponds to the electricity production from a difference of temperature. This effect can be reversible and is the inverse of the Peltier effect, which is the phenomenon of conversion of electric energy into thermal energy (heat). These effects can be superimposed onto the dissipative processes of transport by conduction of electric charges (Joule effect) and to the transport of heat (Fourier equation) which are both irreversible processes. 

Other includes net imports of coal coke and electricity produced from wood, waste, wind, photovoltaic, and solar thermal sources connected to electric utihty distribution systems. It does not include consumption of wood energy other than that consumed by electric utiUty industry. 

Fig. 1. Thermal energy use vs temperature (2). Electricity generation is practical from thermal energy sources hotter than 150°C.

Obstacles attend this new solution of the freshwater problem, which magnify those familiar to the chemical engineer in purifying other cheap or worthless raw materials into valuable products by treatment with chemicals or thermal or electrical energy. These obstacles are quite different from the previous main problem of water supply, ie, the factor of happenstance in finding a river or lake nearby or of making a fortunate geological strike. 

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