Daily Archives March 2, 2016

Specifications of and Key Assumptions for Fuel Production Pathways

Table IV presents specifications of and key assump­tions of fuel production pathways for North Amer­ican applications. For each fuel pathway, the table presents the fuel pathway (including feedstocks), key parametric assumptions, and main pathway charac­teristics. Note that the petroleum gasoline pathway is the baseline pathway to which other fuel production pathways are compared.

8.1 Vehicle Fuel Economy Assumptions

Table V lists the fuel economy of baseline gasoline vehicles (GVs) and the fuel economy ratios of alternative vehicle/fuel systems relative to the base­line GV. The values are based on research at Argonne National Laboratory of various vehicle technologies and fuel economy simulations from studies com­pleted at Argonne and elsewhere. The baseline GV fuel economy [27...

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Gas Turbines

Derived from aero-applications, power generation with gas turbines is commonplace, with an extensive installed capacity and sizes ranging from 500 kWe to >50 MWe. Low maintenance costs and high-grade heat recovery have made gas turbines a favorite in industrial DE applications.

The unit has a turbine and compressor on the same shaft and compressed combustion products at high temperature drive the turbine. Compressor losses and materials restrictions inhibit the upper temperature of the cycle and thus constrain efficiency. Hot exhaust gases are used to preheat incoming air (regeneration). The remaining thermal energy of these exhaust gases can be reclaimed as waste to heat a boiler. A typical energy balance is as follows: electricity, 30%; high – grade heat, 50%; stack losses, 14...

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AND EMISSION RESULTS OF VEHICLE/FUEL SYSTEMS

Because different studies have different system boundaries and parametric assumptions, the studies
described in Section 7 resulted in different magni­tudes of changes in energy use and GHG emissions. The GREET model was used to develop the results presented in this section. In conducting the analyses with the GREET model, key assumptions were specified by taking into account the results from various completed studies. Because some of the vehicle/fuel systems are emerging technologies and are not in the marketplace yet, all technologies were analyzed for the time frame around 2010, so that both emerging technologies and technologies already in the marketplace can be compared within the same period.

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Engines

Reciprocating IC engines are an established and well – known technology. Engines for stationary power are

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FIGURE 3 U. S. photovoltaic shipments. From Energy Information Administration (2001), Renewable Energy Annual, Table 10, U. S. Department of Energy, Washington, DC.

TABLE I

Qualitative Strengths and Weaknesses ofDE Technologies

Reciprocating

engines

Low capital cost

Fuel flexibility

High air pollutant emissions

Noisy

High reliability Established technology

Quick startup

Frequent maintenance

Thermal output at low temperatures

Gas turbines

Proven reliability and availability

Established technology Larger sizes available

Low capital cost High-temperature steam

Reduced efficiencies a...

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COMPLETED STUDIES

Some of the results of past studies are summarized in the following sections. Although many of the studies estimated both (1) absolute energy use and emissions of vehicle/fuel combinations and (2) energy use and changes in emissions of alternative vehicle/fuel systems relative to benchmark technologies (usually gasoline-fueled light-duty vehicles), the summary here presents relative changes only, because they are more comparable than absolute amounts across studies.

Of the vehicle types that use alternative transpor­tation fuels, most completed studies evaluated only

passenger car applications. However, many alterna­tive transportation fuels and advanced vehicle tech­nologies can also be applied to heavy-duty trucks...

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OVERVIEW OF DE TECHNOLOGIES

DE technologies have a range of technical character­istics, making different technologies more suitable in specific applications, depending on whether the determining criterion is electrical output, provision of usable heat, fuel availability, reliability, or emission levels, to name just a few criteria. However, all DE technologies have the capacity to be remotely operated and controlled. This is achieved through monitoring a range of operating parameters via a
communication link and allows simplified mainte­nance, avoids unexpected shutdowns, and eases the grid control issues that arise from locating DE units within the electric distribution network...

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DE MARKET STATUS

It is extremely difficult, or even impossible, to provide values for the total installed capacity of DE technol­ogies and resources. This is due to the range of technologies, their varying levels of use in different countries, and ambiguity over what constitutes a DE application as unit sizes become larger and units are sited further from demand centers. In addition, some of the most promising technologies, including fuel cells, photovoltaics, and microturbines, either are just entering commercialization or are used only in niche applications. The relative rate of technological pro­gress and the regulatory structure of energy markets will determine to what degree and how quickly DE will penetrate the mainstream market...

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HISTORICAL DEVELOPMENT OF DE

The shift toward DE can in many ways be viewed as power generation coming full circle. In the 1880s, Thomas Edison’s Pearl Street electricity system

serving Wall Street and the surrounding city blocks was distributed power. This paradigm was continued over the next 20 years with schemes in the United States and across the world serving limited urban areas with small-scale direct current (DC) systems. Also popular were installations serving individual factories and supplying electricity and heat in combined heat and power (CHP) applications. One large drawback of using DC was the large losses from this low-voltage system when transmitting power over distance. An alternative system based on alternating current (AC) was promoted by a number of competitors, including George Westinghouse...

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