Randall P. Field

Biomass logistics analysis for large scale biofuel production: case study of loblolly pine and switchgrass.

The objective of this study was to assess the costs, energy consumption and greenhouse gas (GHG) emissions throughout the biomass supply chain for large scale biofuel production. Two types of energy crop were considered, switchgrass and loblolly pine, as representative of herbaceous and woody biomass. A biomass logistics model has been developed to estimate the feedstock supply system from biomass production through transportation. Biomass in the form of woodchip, bale and pellet was investigated with road, railway and waterway transportation options. Our analysis indicated that the farm or forest gate cost is lowest for loblolly pine whole tree woodchip at

Hybrid Solar-Geothermal Power Generation to Increase the Energy Production from a Binary Geothermal Plant

39.7/dry tonne and highest for switchgrass round bale at

Integration of a CaO-Based Thermal Storage System in an IGCC Plant With Carbon Capture

72.3/dry tonne. Switchgrass farm gate GHG emissions is approximately 146kgCO2e/dry tonne, about 4 times higher than loblolly pine. The optimum biomass transportation mode and delivered form are determined by the tradeoff between fixed and variable costs for feedstock shipment.

Techno-Economic Evaluation of Pressurized Oxy-Fuel Combustion Systems

This article examines how hybridization using solar thermal energy can increase the power output of a geothermal binary power plant that is operating on geothermal fluid conditions that fall short of design values in temperature and flow rate. The power cycle consists of a subcritical organic Rankine cycle using industrial grade isobutane as the working fluid. Each of the power plant units includes two expanders, a vaporizer, a preheater and air-cooled condensers. Aspen Plus was used to model the plant; the model was validated and adjusted by comparing its predictions to data collected during the first year of operation. The model was then run to determine the best strategy for distributing the available geothermal fluid between the two units to optimize the plant for the existing degraded geofluid conditions. Two solar-geothermal hybrid designs were evaluated to assess their ability to increase the power output and the annual energy production relative to the geothermal-only case.Copyright

Baseline Flowsheet Model for IGCC with Carbon Capture

Using pre-combustion CO2-capture, IGCC plants show significant potential for efficient power generation with carbon capture. The gasification and gas processing steps however have multiple temperature and flow constraints which severely limit the flexibility of IGCC plants to meet the dynamic demands of the current grid. To address this issue, a CaO-based energy storage system has recently been proposed to substantially increase the load range of a base IGCC plant without cycling the gasifier island.In this work, further storage configurations have been assessed, addressing the inefficiencies identified in previous work. In particular, the following cases have been investigated: directly fired calciners with varying make-up flow rate to minimize the purge stream energy loss, directly fired calciners with improved heat integration to reduce the calciner syngas demand and an indirectly fired calciner to minimize the ASU penalty. Additionally, an alternative storage integration strategy after the Selexol unit has been compared both with respect to its performance and its impact on the base IGCC plant design and operation. To this end, process simulation was undertaken in Aspen Plus™. As demonstrated, the CaO based energy storage system can be effectively used to modulate the IGCC net power output by ±20–25%, while maintaining the capture capacity of 90% of the CO2-emissions. Improvement of the particle reactivity and the internal heat recuperation were found to impact the round-trip efficiency the most.Copyright

Performance of an IGCC Plant with Carbon Capture and Coal-CO2-Slurry Feed: Impact of Coal Rank, Slurry Loading, and Syngas Cooling Technology

Oxy-fuel combustion coal-fired power plants can achieve significant reduction in carbon dioxide emissions, but at the cost of lowering their efficiency. Research and development are conducted to reduce the efficiency penalty and to improve their reliability. High-pressure oxy-fuel combustion has been shown to improve the overall performance by recuperating more of the fuel enthalpy into the power cycle. In our previous papers, we demonstrated how pressurized oxy-fuel combustion indeed achieves higher net efficiency than that of conventional atmospheric oxy-fuel power cycles. The system utilizes a cryogenic air separation unit, a carbon dioxide purification/compression unit, and flue gas recirculation system, adding to its cost. In this study, we perform a techno-economic feasibility study of pressurized oxy-fuel combustion power systems. A number of reports and papers have been used to develop reliable models which can predict the costs of power plant components, its operation, and carbon dioxide capture specific systems, etc. We evaluate different metrics including capital investments, cost of electricity, and CO2 avoidance costs. Based on our cost analysis, we show that the pressurized oxy-fuel power system is an effective solution in comparison to other carbon dioxide capture technologies. The higher heat recovery displaces some of the regeneration components of the feedwater system. Moreover, pressurized operating conditions lead to reduction in the size of several other critical components. Sensitivity analysis with respect to important parameters such as coal price and plant capacity is performed. The analysis suggests a guideline to operate pressurized oxy-fuel combustion power plants in a more cost-effective way.Copyright