Total Power Generation Efficiency Research Articles

Performance improvement of an integrated system with high-temperature PEMFC, Kalina cycle and concentrating photovoltaic (CPV) for low temperature heat recovery

This study proposed a novel integrated system that including the high-temperature proton exchange membrane fuel cell (HT-PEMFC), Kalina cycle, concentrating photovoltaic (CPV), and the half-effect absorption refrigeration system. The waste heat discharged from HT-PEMFC was recovered to drive Kalina cycle for more power output, while the lower-grade waste heat of CPV was utilized by the half-effect absorption refrigeration cycle which provided the refrigerating capacity for Kalina cycle’ condenser cooling demand, and thus the power output of Kalina can be further improved. For examining the feasibility and evaluating the performance of the novel integrated system, a mathematical model for the proposed system was established. The results showed that the electrical efficiency of Kalina subsystem was increased by 1.217%, the exergy efficiency of PEMFC and CPV were increased by 23.99% and 9.39%, respectively, compared with the single supply system. Parameter analysis indicated that the efficiency of integrated system was improved with the increase of fuel cell operating temperature, photovoltaic operating temperature and the basic ammonia concentration, and was decreased with the increase of the Kalina separation pressure and PEMFC current density. It was also found that the total power generation efficiency of integrated system was 27.71%, which was increased by 5.03% compared with the single supply system.

Study on Buildings CCHP System Based on SOFC

The relationship among the working temperature, pressure and current density of a Solid oxide fuel cell (SOFC) and its output power and efficiency are analyzed in the framework of a theoretical model able to provide, among other things, the volt ampere characteristic curve. In particular, following the principle of temperature matching and cascade utilization, we consider a gas turbine (GT) and a LiBr absorption chiller to recycle the high-grade exhaust heat produced by the considered SOFC. This distributed total energy system is set up with the intent to meet typical needs of buildings for cooling, heating and power (CCHP). The total power generated by the considered SOFC and gas turbine is about 222 kW and the total power generation efficiency by low heat value of fuel (LHV) is 63.7%. In the CCHP system, the high temperature exhaust of GT is further used to drive LiBr absorption unit, which can produce about 34.8 kW cooling capacity or 84.5 kW of heat (the total energy utilization 78.03%).

Thermodynamic performance study of the MR SOFC-HAT-CCHP system

Based on Aspen Plus, a methanol reforming Solid Oxide Fuel Cell - Humid Air Turbine - Combined cooling, heating and power (SOFC-HAT-CCHP) system based on solar methanol reforming is built in this paper, which combines (Solid Oxide Fuel Cell) SOFC with (Humid Air Turbine) HAT power generation system. This paper analyzes the performance of SOFC-HAT-CCHP system, and reveals the affinity of complementary utilization of solar energy and chemical energy. This paper optimizes the integrated design of the system and constructs a steady state model of the system's thermal calculation. The calculation results show that the total power efficiency of the method, the system total exergy efficiency and the thermal efficiency are 57.2%, 63.0% and 87.1% respectively. The results show that the introduction of HAT power generation system has increased the power generation and reduced the coal consumption rate. Compared with simple methanol reforming (Solid Oxide Fuel Cell - Gas Turbine - Combined cooling, heating and power) SOFC-GT-CCHP, the introduction of HAT effectively improves the total power generation efficiency of the system and increases 4.1% points. The exergy efficiency of increased by 4.6% points. Compared to the reference system, the standard coal consumption rate of electricity generated by the new system decreased by 16.6 g/kWh and the power generation increased by 15.5 g/kWh.

Design of Water Deflection Mechanism for Ocean Current Energy Generation Device

Ocean current energy, as a large reserve and clean energy, has become an important direction for the development of renewable energy. Nowadays, many researches on ocean current energy have focused on the design of different kinds of generators and blades to make efficient use of currents, and there is a lack of research on how to use currents in a wider range. This paper has designed a water guiding mechanism through theoretical analysis and experimental verification, using a wider range of sea currents, increasing the kinetic energy of the impact blade and the blade energy efficiency, and improving the total power generation efficiency of the device. The water guiding mechanism is divided into a cylindrical current collecting and accelerating device, and a gradient tube based on a coupled electromagnetic field. In the current collecting and accelerating part, the cylindrical capacitor is designed, and the inductor coil is wound on it. The alternating current of the two is used to construct a composite electromagnetic field, so that the seawater undergoes deflection acceleration under the action of the electric field force, and the directional movement generates a current. The current is received in the magnetic field, making the water to accelerate the injection, so as to achieve the current acceleration effect. In the gradient tube part, the gradient tube parameters are calculated by the equal-area criterion and the law of energy loss according to the targeted increasing magnification of the flow rate. Large-scale currents flow through the current collecting and accelerating device to produce a convergent and accelerating effect, and then flow into the gradation tube. On the one hand, the velocity increases once more. On the other hand, the gradation tube can reduce the turbulence coefficient that increases due to deflection. A wider range of currents is used.

Enhanced electricity production from rice straw

Developing an approach of electricity production can lead stakeholders to make proper and appropriate decisions in the future. This research proposes an integrated system of electricity production from biomass waste which could bring to both economic and environmental benefit. As case study, straw yield of rice is investigated. In this study, an enhanced integrated system of power generation is proposed. The integrated system consists of a torrefaction, entrained flow gasification, gas cleaning module, and combined cycle for power generation. As an effort to optimize the heat circulation and minimize the exergy loss throughout the proposed system, enhanced process integration technology (EPI) is also implemented. By adopting the EPI, the unrecoverable energy or heat in a single process can be recovered and utilized in other processes through process integration. Furthermore, the influences of torrefaction temperature to the total generated power and power generation efficiency are also investigated. Results of calculation and modeling show a very high energy efficiency of integrated system. A positive energy harvesting with the total power generation efficiency of about 43% can be achieved.

Power generation from algae employing enhanced process integration technology

An integrated power-generation system with enhanced process integration (EPI), using macroalgae as a fuel source, is proposed. The integrated system includes a drying, conversion through gasification, and power generation in a combined cycle. An EPI that combines heat circulation and process integration was used to significantly reduce the exergy destruction in the integrated system. Brown seaweed Fucus sp. was selected as a representative macroalgae. The influence of fluidization velocities during drying and gasification on power generation efficiency was evaluated. The proposed integrated system showed an extremely high power generation efficiency of approximately 60%. No significant relationship was found between the fluidization velocities in drying and gasification to total power generation efficiency. The effect of the turbine inlet temperature (TIT) in the gas turbine was also evaluated. It showed that a higher TIT resulted in higher total power generation efficiency due to enhanced energy/heat recovery, especially from the steam turbine.

Enhanced Energy Utilization System of Algae: Integrated Drying, Gasification and Combined Cycle

A highly energy-efficient integrated energy utilization system consisting of drying, gasification and combined cycle for algae is proposed. The integration is performed based on the concept of exergy recovery and process integration technologies. The energy involved in each process is basically recovered thoroughly through exergy recovery. In addition, the unrecoverable energy in a single process will be utilized in other processes using the principle of process integration. The combination of these technologies can minimize the total exergy destruction throughout the integrated system. Hence, significant improvement in energy efficiency can be achieved leading to high total power generation efficiency. Alga Laminaria digitata was used as sample during process calculation. Two main analyses have been performed relating to drying performance and total power generation. As the results of the study, the proposed integrated-system showed a very high energy efficiency. A significantly positive energy harvesting from algae with the total power generation efficiency of about 40% can be achieved.

Advanced Energy Harvesting from Macroalgae—Innovative Integration of Drying, Gasification and Combined Cycle

State-of-the-art integrated macroalgae utilization processes, consisting of drying, gasification, and combined cycle, are proposed and their performance with respect to energy efficiency are evaluated. To achieve high exergy efficiency, the integration is performed through two main principles: exergy recovery and process integration. Initially, the energy involved in one process is recirculated intensively through exergy elevation and effective heat coupling. Furthermore, the unrecoverable energy from one process will be utilized in the other processes through process integration. As the result, the total exergy destruction from the whole integrated processes can be minimized significantly leading to significant improvement in energy efficiency. The first analysis relates to the performance of integrated drying process, especially the influence of target moisture content to energy consumption. Furthermore, the influences of gasification fluidization velocity to the total generated power and power generation efficiency are also calculated. As the results of study, the proposed integrated-processes proved a very high energy efficiency. A positive energy harvesting with the total power generation efficiency of about 40% could be achieved.

Integration of energy-efficient empty fruit bunch drying with gasification/combined cycle systems

A high-energy-efficient process for empty fruit bunch drying with integration to gasification and combined cycle processes is proposed. The enhancement is due to greater exergy recovery and more efficient process integration. Basically, the energy/heat involved in a single process is recovered as much as possible, leading to minimization of exergy destruction. In addition, the unrecoverable energy/heat is utilized for other processes through process integration. During drying, a fluidized bed dryer with superheated steam is used as the main evaporator. Exergy recovery is performed through exergy elevation via compression and effective heat coupling in a dryer and heat exchangers. The dried empty fruit bunches are gasified in a fluidized bed gasifier using air as the fluidizing gas. Furthermore, the produced syngas is utilized as fuel in the combined cycle module. From process analysis, the proposed integrated processes can achieve a relatively high energy efficiency. Compared to a standalone drying process employing exergy recovery, the proposed integrated drying can reduce consumed energy by about 1/3. In addition, the overall integrated processes can reach a total power generation efficiency of about 44%.

Power generation efficiency of an SOFC–PEFC combined system with time shift utilization of SOFC exhaust heat

A microgrid, with little environmental impact, is developed by introducing a combined SOFC (solid oxide fuel cell) and PEFC (proton exchange membrane fuel cell) system. Although the SOFC requires a higher operation temperature compared to the PEFC, the power generation efficiency of the SOFC is higher. However, if high temperature exhaust heat may be used effectively, a system with higher total power generation efficiency can be built. Therefore, this paper investigates the operation of a SOFC–PEFC combined system, with time shift operation of reformed gas, into a microgrid with 30 houses in Sapporo, Japan. The SOFC is designed to correspond to base load operation, and the exhaust heat of the SOFC is used for production of reformed gas. This reformed gas is used for the production of electricity for the PEFC, corresponding to fluctuation load of the next day. Accordingly, the reformed gas is used with a time shift operation. In this paper, the relation between operation method, power generation efficiency, and amount of heat storage of the SOFC–PEFC combined system to the difference in power load pattern was investigated. The average power generation efficiency of the system can be maintained at nearly 48% on a representative day in February (winter season) and August (summer season).

OS5-01 低温型と高温型を直列配置した平板型SOFC発電のサイクル解析(OS5 水素・燃料電池)

In this study, two-stage SOFC cycle by series connection of low- and high-temperature SOFCs (Lanthanum gallate and YSZ electrolyte, respectively) and a gas turbine has been studied. This cycle can extend the operating temperature range of SOFC and may increase a total power generation efficiency. This report has estimated system efficiency by cycle analysis of two-stage SOFC power generation with gas turbine. Fuel and air recirculation and external reforming have been adopted in this calculation. Physical properties and activation overpotential of low-temperature SOFC were based on recent published data and they are relatively superior to those of high-temperature SOFC. The analysis result shows the SOFC power generation efficiency of 50.3% and total power generation efficiency of 56.1% under a standard condition (low-temperature FC average temperature: 1023K, current density: 0.3A/cm^3, cell pressure: 1.0MPa, total fuel utilization ratio at PCs: 85%). The total power generating efficiency increases with increases of low-temperature SOFC average temperature and fuel and air utilization ratios, respectively. It also shows a positive cell pressure dependence, but peaks out around 1.0MPa.

Cycle Analysis of Two-stage Planar SOFC Power Generation by Series Connection of Low and High Temperature SOFCs

Solid Oxide Fuel Cell (SOFC) can be composed by solid components, and high power generation efficiency of a whole cycle is obtained by using high temperature exhaust heat for fuel reforming and bottoming power generation. Recently, the low temperature SOFC, which runs in the temperature range of around 600°C or above, has been developed with the high efficiency of power generation. On the other hand, multi-stage power generation system has been proposed by the United States DOE. In this study, a power generation system of two-stage SOFC by series connection of low and high temperature SOFCs has been studied. Overpotential data for low-temperature SOFC used in this study are based on recent published data, and those for high temperature SOFC arhaihe based on our previous study. The analytical results show the two-stage SOFC power generation efficiency of 50.3% and the total power generation efficiency of 56.1% under a standard operating condition.