Environmental assessment of a hybrid system composed of solid oxide fuel cell, gas turbine and multiple effect evaporation desalination system

To provide a corresponding preparation and foundation for the implementation and testing of China 6, as well as provide a strong reference for the formulation of China automotive test cycle (CATC) in the future, portable emission measurement system (PEMS) was applied to carry out CO and NOx emissions test on conventional roads for a light-duty gasoline vehicle (Toyota Levin) and a heavy-duty diesel vehicle (KING LONG bus) in Nanjing. The results showed that the CO emission rate of the Toyota car was mainly determined by the speed. As the vehicle speed increased, the CO emission rate increased rapidly while it was below 0.035 g/s. The CO emission rate of KING LONG bus accelerated with the increase of the vehicle speed at the lower speed and began to decrease when the speed reached 60 km/h. In terms of NOx emission rate, as the vehicle speed increased, the NOx emission rates of both vehicles increased. The CO and NOx emission factors of the two models showed similar patterns, both of which decreased significantly as the vehicle speed increased. Compared with the corresponding emission limits, the CO emission of both vehicles was higher, especially for light vehicle, and it was more than 3 times the limit. The NOx emission of both vehicles met the corresponding emission standards. The CO and NOx emission rates of light vehicles were positively correlated with specific power of vehicle (VSP). When VSP was less than 16, the two pollutants emission rate variation with VSP of heavy vehicle showed the same trend, while it was different when VSP was more than 16.

With high efficiency and very low emissions, fuel cells have been one of the choices of research in current energy development. The Solid Oxide Fuel Cell (SOFC) is a high temperature type fuel cell. It has the characteristic of very high operating temperature 1,027°C (1,300K). The SOFC has the main advantage of very high performance efficiency (over 50%), but also has very high exhaust temperature. Current studies point out that the combination of SOFC and Gas Turbine (GT) can produce efficiency more than 60%. The exhaust temperature of this hybrid power system can be as high as 227–327°C (500–600K). With this waste heat utilized, we can further improve the overall efficiency of the system. A simulation program of SOFC/GT system and the introduction of the concept of Combined Cooling, Heating, and Power System (CCHP) have been used in this study. The waste heat of SOFC/GT hybrid power generation system was used as the heat source to drive an Absorption Refrigeration System (ARS) for cooling. This waste heat enables the SOFC/GT to generate electricity in the system while providing additional cooling and heating capacity. Therefore, we have a combined CCHP system developed using three major modules which are SOFC, GT, and ARS modules. The SOFC module was verified by our test data. The GT and SOFC/GT modules were compared to a commercial code and literature data. Both the single- and double-effect ARS modules were verified with available literature results. Finally, the CCHP analysis simulation system, which combines SOFC, GT, and ARS, has been completed. With this CCHP configuration system, the fuel usability of the system by our definition could be above 100%, especially for the double effect ARS. This analysis system has demonstrated to be a useful tool for future CCHP designs with SOFC/GT systems.

The gaseous emissions of stage Ⅲ standard City bus with and without DOC+CDPF after-treatment fueled with biodiesel blends on real road in steady-state and transient conditions were studied using OBS-2200 gaseous portable emission measurement. The results showed that B20 led to a decrease of CO and THC emission rates compared with those of B0. In steady-state condition, CO and THC average mass emission rates of B20 decreased by 26.43% and 10.44% respectively and in transient condition the decrease rates were 22.78% and 4.95%. Meanwhile, B20 eventuated in higher CO2 and NOx emission rates. In steady-state condition, CO2 and NOx average mass emission rates of B20 increased by 8.41% and 8.26% respectively and in transient condition the increase rates were 7.15% and 9.13%. DOC+CDPF caused a more obvious reduction of CO and THC emission rates of B20 compared with B0. In steady-state condition, CO and THC average emission rates decreased by 60.58% and 79.92%, while in transient condition they decreased by 63.67% and 82.57%. The influence of DOC+CDPF on emission reduction of CO2 and NOx was not obvious.

In this paper, exergy, exergoeconomic, and exergoenvironmental analysis of a gas turbine cycle and its optimization has been carried out by MOPSO algorithm. Three objective functions, namely, total cost rate, exergy efficiency of cycle, and CO2 emission rate have been considered. The design variables considered are: compressor pressure ratio, combustion chamber inlet temperature, gas turbine inlet temperature, compressor, and gas turbine isentropic efficiency. The impact of change in gas turbine inlet temperature and compressor pressure ratio on CO2 emission rate as well as impact of changes in gas turbine inlet temperature on exergy efficiency of the cycle has been investigated in different compressor pressure ratios. The results showed that with increase in compressor pressure ratio and gas turbine inlet temperature, CO2 emission rate decreases, that is this reduction is carried out with a steeper slope at lower pressure compressor ratio and gas turbine inlet temperature. The results showed that exergy efficiency of the cycle increases with increase in gas turbine inlet temperature and compressor pressure ratio. The sensitivity analysis of fuel cost changes was performed on objective functions. The results showed that at higher exergy efficiencies total cost rate is greater, and sensitivity of fuel cost optimum solutions is greater than Pareto curve with lower total cost rate. Also, the results showed that sensitivity of changes in fuel cost rate per unit of energy on total cost rate is greater than the rate of CO2 emission.

Coal gasification, cleaning of the synthesis gas (syngas), and combustion of the clean syngas is currently the upcoming IGCC (Integrated Gasification Combined Cycle) method in the thermal power production and control of several air contaminants and possibly the greenhouse gases. A good number of patented feedgasifiers are commercially available. Once coal or other feed is gasified, the elemental sulfur is removed from syngas and, then it is possible to remove the carbon-dioxide (a greenhouse gas) as required by the upcoming local, state, and federal environmental regulations. Currently, the syngas with the carbon-dioxide is fired in the stationary combustion turbines (CTs) to produce power. IGCC process is, currently, the preferred choice over conventional thermal power production in regard to cleanup of fuel and significantly reduced contaminant emissions. The air permitting requirements include the review of: feed preparation and PM emissions; feed gasification and contaminant emissions; elemental sulfur recovery and SO2 emissions; options for carbon-dioxide recovery; syngas characteristics for combustion; CT design and combustion mechanisms; air contaminant emissions of CT; controlled CT emissions of nitrogen-oxides and carbon-monoxide gases using the SCR and oxidation catalysts, respectively; and, emission of volatile organic compounds (VOCs), and hazardous air pollutants (HAPs). However, the IGCC processes are being rigorously reviewed for the system integration and reliability, and significant reduction of air contaminant emissions (including the greenhouse gases). This paper included a review of IGCC air contaminant emission rates, and various applicable regulatory requirements, such as NSR (New Source Review), NSPS (New Source Performance Standards), and MACT (maximum achievable control technology). The IGCC facility’s NOX, CO, SO2, PM, VOCs, and HAPs emission rates would be significantly low. Thus, effective, construction and installation, and operation air permits would be necessary for IGCC facilities.

Road emission test is for heavy-duty diesel trucks, retrofitted compressed natural gas cars, and light gasoline cars. To study the relationship between engine speed, load, and emission, the relationship between engine speed, engine emissions per cylinder per working cycle and emission ratio is put forward. The results showed that the NOx, CO, and CO2 emission rates of diesel trucks, natural gas cars, and gasoline cars increase with the increase of engine speed and load. The engine emissions per cylinder per working cycle increases with the increase of engine load. The trend of CO emission rate of heavy diesel truck is not obvious with engine condition.

In spite of the high performance characteristics of the solid oxide fuel cell / gas turbine (SOFC/GT) hybrid system, it is very difficult to maintain the high level performance under real application conditions, which generally require part-load operations. The performance loss of SOFC/GT hybrid systems under part-load operating conditions is closely related to that of the gas turbine. The power generated by the gas turbine in a hybrid system is much smaller than that generated by the SOFC. However, its contribution to the system efficiency is very important especially at part-load operating conditions. Therefore, to enhance the part-load performance of hybrid systems, it is useful to reduce the relative amount of power generated by a gas turbine that delivers lower performance than a SOFC. In the present study, several part-load operation strategies related to the gas turbine are studied and their impacts on the performance of a SOFC/GT hybrid system are discussed.

Conventional recuperative micro gas turbines have a 30 per cent low heating value (LHV) maximum efficiency at full load. Therefore, if they are to be used in a potential distributed energy scenario, solutions must be developed that increase efficiency. An innovative gas turbine-based technology is the fuel cell — gas turbine hybrid system. This work is aimed at studying how the basic performance of a conventional Brayton cycle changes when heat addition is done at a fuel cell. Two layouts are considered: a direct system where the compressor feeds the fuel cell directly and an indirect system where only heat is transferred between subsystems. Direct and indirect systems have been studied at full and part load, concluding that the efficiency versus pressure ratio curves of hybrid systems change substantially with respect to a traditional gas turbine; part-load efficiency hardly decreases. Maximum efficiency of hybrid systems doubles the efficiency of state of the art micro gas turbine and remains high at part load. Furthermore, the benefit of a certain increase in temperature is higher for hybrid systems than for conventional engines. Finally, a simple economic analysis shows that the total installation and operation/maintenance costs of hybrid systems make them competitive against conventional gas turbines.

Carbon and nitrogen emissions rates and heat transfer of an indirect pyrolysis biomass cookstove

Determination of anthropogenic emissions in the Augsburg area by the source–tracer-ratio method

Light commercial vehicles (LCVs) account for about 10-15% of road traffic in Europe. There have only been few investigations on their on-road emission performance. Here, on-road remote sensing vehicle emission measurements from 18 locations across four European countries are combined for a comprehensive analysis of NOx and smoke emission rates from diesel LCV in the past two decades. This allows differentiating the performance by emission standards, model years, curb weights, engine loads, manufacturers, vehicle age, and temperature, as well as by measurement devices. We find a general consistency between devices and countries. On-road NOx emission rates have been much higher than type approval limit values for all manufacturers, but some perform systematically better than others. Emission rates have gone down only with the introduction of Euro 6a-b emission standards since the year 2015. Smoke emission rates are considered a proxy for particulate emissions. Their emissions have decrease substantially from the year 2010 onward for all countries and size classes measured. This is consistent with the substantial tightening of the particulate matter emission limit value that typically forced the introduction of a diesel particulate filter. The average NOx emission rate increases with engine load and decreasing ambient temperatures, particularly for Euro 4 and 5 emission classes. This explains to a large extent the differences in the absolute level between the measurement sites together with differences in fleet composition. These dependencies have already been observed earlier with diesel passenger cars; they are considered part of an abnormal emission control strategy. Some limited increase of the NOx emission rate is observed for Euro 3 vehicles older than 10 years. The strong increase for the youngest Euro 6 LCVs might rather reflect technology advances with successively younger models than genuine deterioration. However, the durability of emission controls for Euro 6 vehicles should be better monitored closely. Smoke emission rates continuously increase with vehicle age, suggesting a deterioration of the after-treatment system with use.

Five light-duty vehicles were used to investigate HC, CO, and NOx emissions and fuel economy sensitivity to changes in the length of soak period preceding the EPA Urban Dynamometer Driving Schedule (UDDS). Emission tests were conducted following soak periods 10 minutes to 36 hours in length. HC and NOx emission rates and fuel consumption during the UDDS increased almost linearly with log 10 of soak period length. CO emission rates during the UDDS are stable following soak periods of 10 minutes to 1 hour in length, but the level ranges from 10 to 70 percent of the 16-hour soak value depending on the type of exhaust after treatment. Following 2-hour and longer soak periods, CO increased approximately linearly with log 10 soak length. Soak period length does affect emission rates and fuel consumption during the stabilized portion of the UDDS, but the magnitude of the effect is small compared to that observed during the transient portion.

Development of vehicle emission rates based on vehicle-specific power and velocity

Transfer function development for control of cathode airflow transients in fuel cell gas turbine hybrid systems

A theoretical solid oxide fuel cell–gas turbine hybrid system has been designed using a Capstone 60 kW micro-gas turbine. Through simulation it is demonstrated that the hybrid system can be controlled to achieve transient capability greater than the Capstone 60 kW recuperated gas turbine alone. The Capstone 60 kW gas turbine transient capability is limited because in order to maintain combustor, turbine and heat exchangers temperatures within operating requirements, the Capstone combustor fuel-to-air ratio must be maintained. Potentially fast fuel flow rate changes, must be limited to the slower, inertia limited, turbo machinery air response. This limits a 60 kW recuperated gas turbine to transient response rates of approximately 1 kW s −1. However, in the SOFC/GT hybrid system, the combustor temperature can be controlled, by manipulating the fuel cell current, to regulate the amount of fuel sent to the combustor. By using such control pairing, the fuel flow rate does not have to be constrained by the air flow in SOFC/GT hybrid systems. This makes it possible to use the rotational inertia of the gas turbine, to buffer the fuel cell power response, during fuel cell fuel flow transients that otherwise limit fuel cell system transient capability. Such synergistic integration improves the transient response capability of the integrated SOFC gas turbine hybrid system. Through simulation it has been demonstrated that SOFC/GT hybrid system can be developed to have excellent transient capability.