Journal of Energy Engineering

Thermal generators’ emissions constitute an externality on which a regulator might wish to impose constraints. In addition, transmission capacity for sending energy may be naturally restricted by the grid facilities. Both pollution standards and transmission capacity impose constraints, coupling the strategies of the agents in their joint strategy space. To force competitive electricity generators to respect those constraints when individual monitoring is unavailable we envisage the regulator solving a generalized Nash equilibrium problem to establish an equilibrium in which the joint constraints are satisfied. If the regulator appropriately modifies the generators’ payoffs then they will play a decoupled game in which they can ignore the information on the joint constraints. For the payoff modification to induce the required behavior, a coupled constraints equilibrium needs to exist and be unique. We borrow from the electrical engineering (EE) literature a three-node network model that has these properties and use it in this paper to discuss and explain the behavior of the agents subjected to the coupled constraints. We find that the imposition of transmission and environmental restrictions may increase the output share of an inefficient generator and decrease consumer surplus.

One of the current targets of European Union (EU) energy policy is to reach at least a 10% share of biofuels in fuel consumed for transportation (petrol and diesel) in 2020. However, it has not been specified how this global target should be distributed among the Member States according to its different starting points and potentials. Therefore, the purpose of this study is to propose a dynamic nonlinear target distribution method for increasing the share of biofuels in fuel consumed for transportation. We applied the proposed distribution based on the following indicators: nonbiofuels in fuel consumed for transportation, nonbiofuels per capita, nonbiofuels per gross domestic product (GDP), and GDP per capita, in the reference year (2005). In addition, a multicriteria analysis was also conducted to weigh the variables in the study. The proposed methodology is innovative, easy-to-use, and attempts to contribute to the political discussion on the importance of territorial weighing of the biofuel consumption target by the real situation in each member state.

A one-dimensional, nonisothermal model for passive direct methanol fuel cells (DMFCs) is developed. The coupled heat and mass transport, along with electrochemical reactions, are considered in the model. Cell performance for different methanol feed concentrations is evaluated. The reason for improved fuel cell performance at increased methanol feed concentrations is investigated and explained. Variations in cell operating temperature, heat generation rate at the anode catalyst layer (ACL), and at the cathode catalyst layer (CCL) are critically analyzed in this connection. It is found that the ACL temperature, referred to as the cell operating temperature, has a crucial effect on passive DMFC performance. The increased cell operating temperature at higher methanol feed concentration is responsible for better cell performance. The results of this work will be useful for optimizing the thermal management and achieving better performance of passive DMFCs.

In order to meet the operating requirements during both winter and summer, a thermosyphon heat exchanger unit used to recover energy from the exhaust air needs to be adjusted for its inclination angle by a regulation mechanism. In this paper, the factors that affect the heat transfer efficiency of the thermosyphon heat exchanger was analyzed and the unit practical operating data in a shopping center was studied. The unit optimal operating mode was acquired due to the influence of the unit inclination angle on the temperature effectiveness under a wide temperature change of the outdoor air. In addition, the inclination angle regulation mechanism uses a programmable logic controller (PLC) to control the unit to work at the optimal operating mode. The unit charged with R410A working fluid worked well and was highly effective.

Energy consumption by the building sector constitutes a large portion of global energy use. Energy-efficient building technologies help to reduce heat gain in hot summer months, heat loss in cold winter months, and modify energy requirements in buildings. In the writers’ paper, the effect of a proposed hollow roof (independent of and combined with a designed brick-cavity wall with brick projections and static sunshade) on indoor air temperature has been analyzed experimentally by constructing four rooms of habitable dimensions ($3.0\times 4.0\times 3.0\text{-}\mathrm{m}$ high) and studying average hourly temperatures for 1 year. Each room has a different combination of type of roof, wall, and static sunshade; hence, the difference in indoor air temperature of the rooms will primarily be attributable to differences in heat transferred through these building elements. The proposed hollow roof combined with the designed brick-cavity wall with brick projections and static sunshade lessened indoor air temperature in summer and increased indoor air temperature in winter mornings and nights. The writers’ structures are thus useful for energy conservation per seasonal needs.

A parameter identification method based on genetic algorithm (GA) is presented to solve the multimodel parameters identification problem for the main steam temperature of ultra-supercritical (USC) units. Linear ranking selection, nonuniform linear crossover, and Gaussian mutation are employed in the algorithm design to enhance the convergence speed and the accuracy of the identification. Besides, the uniform design method is executed to initialize the population and the sigmoid function with adaptation is applied to adjust the probabilities of crossover and mutation. Simulations carried out with the field operation data from Haimen USC units, including two processes—parameters identification and model verification. The simulation results show that the improved genetic algorithm performs well in global parameters searching and the proposed identification methodology offers good results for the multimodel parameters identification.

One of the limitations of using the pump-as-turbine (PAT) technique is its relatively narrow high-efficiency operating range. When the system pressure head or flow rate decreases, trimming the impeller or replacing the impeller with one of a smaller size is an easy and convenient approach. Therefore, research on the impeller diameter in terms of its influence on PAT is useful. To perform research on how the impeller diameter influences PAT, experimental research was first performed on a single-stage centrifugal PAT with three impellers of different diameters. Experimental results show that PAT flow versus head curve is lessened; its flow versus efficiency and flow versus power curves increased after the best-efficiency point in accordance with increasing impeller diameter. The PAT flow rate, required pressure head, generated shaft power, and efficiency at the best-efficiency point increased in accordance with increasing impeller diameter. Numerical simulation and analysis of the PAT with the three impellers were performed using a verified computational fluid dynamics (CFD) technique. Hydraulic loss and flow field distribution analyses show that the total hydraulic loss within PAT and the hydraulic loss within the radial gap between the rotating impeller and stationery volute decreased in accordance with increasing impeller diameter. Theoretical analysis indicates the PAT theoretical head increased and its required pressure head decreased in accordance with increasing impeller diameter. Theoretical formulas used to predict PAT performances as the impeller diameter changed were verified. Possible reasons for the deviations between the performances predicted by theoretical formulas and test results are explored.

This study investigates the impact of dimethyl ether (DME) on the combustion and exhaust emission characteristics at low engine load operating and pilot injection conditions in a four-cylinder diesel engine that was modified for DME application. The combustion characteristics were analyzed based on the combustion pressure, the rate of heat release, the accumulated heat release, and the premixed combustion characteristics. The emission characteristics were analyzed through the analysis of the nitrogen oxides (${\mathrm{NO}}_x$), soot, hydrocarbon (HC), and carbon monoxide (CO). The heat release amount per unit crank angle in DME combustion is higher than that in diesel combustion in a pilot injected combustion mode. The accumulated heat release of DME during the main combustion is higher than that of diesel fuel. The pilot injection combustion of DME fuel started earlier than single-injection combustion does. The advanced pilot injection timing caused a decrease of premixed combustion duration and a retardation of premixed combustion phasing. As the pilot injection timing moved to top dead center, the total combustion duration and the heat release amount per unit crank angle decreased. In the emission results, advances of the pilot injection timing caused the decrease of indicated specific (IS) ${\mathrm{ISNO}}_x$ emission in both diesel and DME fuels. The advanced pilot injection timing caused a significant increase of HC and CO emission because of an increase of the overmixed region and incomplete combustion.

An experimental study was conducted to show the influence of the primary air velocity on lean coal combustion in a lateral-ignition tiny-oil burner. Using the lateral ignition scheme, a lean-coal ignition experiment was conducted at a coal feed rate of $3.5\mathrm{t}/\mathrm{h}$ and primary air velocities of 15, 20, 25, and $30\mathrm{m}/\mathrm{s}$. During firing up with three oil guns in the presence of coal, the gas temperature along the center line increased along the flow of primary air. The gas temperatures on the side of the oil guns ($r=+116.5\mathrm{mm}$) were higher than those on the opposite side ($r=-116.5\mathrm{mm}$). As the primary air velocity increased, the gas temperature along the center line at the same measurement point decreased while that on the side with the oil guns rose. However, the gas temperature on the opposite side changed only a little. ${\mathrm{O}}_2$ concentrations at the exit of the burner were 1–3%. The burner resistance resulting from the flow and combustion of pulverized coal was 1,300–1,800 Pa.

W-shaped furnaces equipped with swirl burners suffered from high carbon content in fly ash and high NOx emission. Using an IFA 300 constant-temperature anemometer system, cold air experiments on a scale model of a 300-MW of electrical output down-fired pulverized-coal utility boiler with swirl burners were performed to investigate the effect of the declination angle of vent air on flow characteristics of the furnace. When the angle of vent air was 28°, 35°, and 40°, the flow field in the furnace has good symmetry, which was beneficial to the stable combustion of the flame. As the angle of vent air increased, the mixing of downward airflow and vent air was delayed. At a vent-air angle of 45°, the flow field in the furnace was deflected. The deflected flow field would result in a flame short circuit, the local high temperature, an increase in the carbon content in fly ash, and a reduction of boiler efficiency. The angle of vent air had little effect on the mixing of downward airflow and staged air. Downward airflow began to turn upward in the region of the staged air nozzle and mixed weakly with the staged air. As the declination angle of vent air increased, the mixing of arch downward airflow and staged air was postponed, which extended the residence time of the pulverized coal under strong reducing atmosphere and was beneficial to reducing the generation of fuel NOx. Meanwhile, the dimensionless penetrating depth of downward airflow increased, which helped extend the residence time of the pulverized coal in the furnace, reduced the carbon content in fly ash, and increased the boiler efficiency. Considering the symmetry of the flow field and the dimensionless penetrating depth, the best angle for the vent air is 40°.

The stabilization of non-premixed flame is often done by coupling an annular swirling flow. Acoustic excitation, however, can improve combustion through fuel jet oscillation but can sometimes blow out the flame. The writers aimed to experimentally investigate the effects of annular swirl strength on acoustically excited non-premixed flame. Visual observations coupled with flame length measurements showed that the flame can be particularly shortened and transformed to blue at a low swirl strength. Flame and flow images obtained through the Mie scattering technique showed that the recirculation bubble enlarged proportionally in accordance with the swirl strength. Jet oscillations were diagnosed by using a laser Doppler anemometer at the central jet. Turbulence and mixing properties obtained from the central jet velocity were statistically compared to identify the best combination of swirl strength and acoustic excitation level. Combustion performance was finely validated through flame length and temperature measurements.

A three-phase solid-state solar cell (SSSC) has been developed successfully using TaON nanoparticles or BiOI microspheres as a sensitizer material over a ${\mathrm{TiO}}_2$ film and CuI as a hole collector. Stable current ($I_{sc}$)–voltage ($V_{oc}$) curves are found under ultraviolet UV visible light irradiation with an efficiency of 0.15% and 0.10% for TaON- and BiOI-based solar cells, respectively. The observed photocurrents in SSSCs are approximately 10 and 48 times higher than those in wet-type solar cells (WSCs) based on TaON and BiOI, respectively. A plausible mechanism of charge transfer and hole filling is discussed in terms of the band gap energy and band position of the semiconductor materials.