• Energy Research
• 2016-2025close
• US close
• IR close
• AU close
• Energy close

Abstract Clamping mechanisms have significant effect on the performance of polymer electrolyte membrane (PEM) fuel cells. In this paper, PEM fuel cell with new clamping mechanism is designed to study the contact pressure distribution over the active area of PEM fuel cell's membrane electrode assembly (MEA). The clamping pressure is pneumatically exerted on the PEM fuel cell assembly. A comparison between the conventional and new clamping mechanism is carried out with simulation, and the numerical results are validated against experimental investigation performed in the fuel cell technology research laboratory. The experimental results are gathered using embedded pressure measurement films in the designed single cell. The results achieved via finite element method are in good agreement with experimental results. It is concluded that the contact pressure distribution of MEA for the new clamping mechanism is more uniform than the conventional one.

Abstract To improve the conversion efficiency of thermophotovoltaic devices, we designed a thermophotovoltaic system based on an InAs/InGaAsSb/GaSb three-junction tandem cell. The tandem cell can recover photons in the wavelength range of 200–3650 nm and therefore enhance the output power of the system. To further improve system performance, we designed a multilayer circular truncated cone metamaterial emitter matching the tandem cell. Existing TPV systems based on multi-junction tandem PV cells can achieve conversion efficiencies of 33.3%–41%, while the thermophotovoltaic system coupled with the multilayer circular truncated cone metamaterial can recover more photons of 1.44 mol/(m2·s) and achieve a higher conversion efficiency of 52.8% at 1773 K. The thermophotovoltaic system designed here demonstrates an extremely high energy conversion efficiency and has good application prospects.

Abstract Propane (C3H8) is being considered as an alternative refrigerant, besides being used as an alternative fuel, because of its low Global Warming Potential and zero Ozone Depletion Potential. Using blends of C3H8 with CO2 as refrigerants, diminishes the fire safety concerns in case of accidental leak of this flammable substance in refrigeration applications. This paper reports on the effects of CO2 on laminar burning speed and flame instability of C3H8/air blends at elevated temperatures and pressures. The flame structures were investigated in a Schlieren system. The laminar burning speeds of C3H8/CO2/air mixtures were measured in a spherical chamber and were fitted by a power-law mathematical correlation. The one-dimensional flame code from Cantera with kinetic model was also used to predict laminar burning speed. The high-speed photography showed that CO2 inhibits the flame instability because of its hydrodynamic and diffusional-thermal effects. Results showed that the laminar burning speed decreased with increasing CO2 mole fraction in the mixtures and that CO2 promotes the flame stability. The high temperature C3H8 oxidation was governed by the reaction of H + O 2 = O + OH . The effects of CO2 on laminar burning speed were mainly determined by the reaction of CO 2 + H = CO + OH and the high energy capacity (specific heat) of CO2.

Abstract This study sheds new light on the variability of wind power across the Australian NEM (National Electricity Market) and in doing so gives an insight on the potential network configuration for a high RE (Renewable Electricity) future. We present idealised cost-minimised simulations for the NEM utilising onshore wind, large-scale solar, pumped hydro and OCGT (open cycle gas turbines) technologies. A model using gridded meteorological data from the regional ACCESS-R (Australian Community Climate and Earth-System Simulator) simulates wind and solar technology output along with generation from OCGT to meet demand in the NEM for the period 2010–2011. A cost for connecting each location to the nearest major load centre is introduced and a base scenario created from an initial connection cost of $1 M/km. A sensitivity study reveals that a cost of $8 M/km results in the contraction of all renewable resources to four major wind installations. Compared to the base scenario the four major wind locations share much of the variability in renewable energy output, demonstrating that the NEM region has four distinct wind regimes. Separated by 1,400 km these four wind installations provide an optimisation-based decorrelation length for the NEM. This information is particularly useful for long-term planners of large-scale energy infrastructure.

Abstract This paper uses quantile regression to demonstrate how electricity price distributions are linked to fundamental supply and demand variables. It investigates the California electricity market (zone SP15) for selected trading hours using data from January 8, 2013 to September 24, 2016. The approach quantifies a non-linear relationship between the fundamentals and electricity prices, just as predicted by the merit order curve. Natural gas, greenhouse gas allowance prices and load all have a positive effect on electricity prices, with the effect increasing with the quantiles. In contrast, solar production and wind production both have a negative effect on electricity prices. The effect of solar production increases with quantiles, whereas the effect of wind production decreases with quantiles. This paper also includes a stress testing case study in which a producer faces the risk of high solar and wind production, and investigates the effect on the lower tail of the price distribution. Overall, the results demonstrate how the proposed approach can be a helpful risk management tool for participants in the electricity market.

This study investigates the thermoeconomic performance of a new integrated system including a regenerative two stage organic Rankine cycle which is coupled with a parabolic trough collector via a thermal storage tank. The cold energy of liquefied natural gas (LNG) is used to absorb the heat duty of condenser. The LNG subsystem not only allows the ORC cycle to produce more power by reducing its condensate pressure, but also provides the system with extra power via the LNG expander and chilled water. The system is capable of producing power with solar fraction of a hundred percent during the day. The thermoeconomic analysis is performed to optimize the system for design point conditions. The analysis also reveals the exergoeconomic criteria on system components. Results show that solar collector has the most value of Z˙+C˙D which is due to both high exergy destruction and high investment costs of solar collector. Also, storage tank and condenser are the second and third important components with respect to exergoeconomic criterion. Parametric analysis is performed on the system to show the effects of eleven key thermodynamic parameters on system performance. In order for optimization, the product cost rate and exergy efficiency are chosen as the objectives. Eleven decision variables including inlet temperature and pressure of the turbines, heat exchanger minimum temperature differences along with the mass flow rate of storage tank, condensate pressure and LNG pressure were chosen according to parametric analysis. With the aid of TOPSIS decision making technique, the optimal point was selected among the Pareto frontier of the genetic algorithm. Results show that system can reach the efficiency of 19.59% and product cost rate of 3.88 million dollars per year.

Abstract The use of compressed air in industry is an important and yet overlooked energy carrier. Although there are different energy-saving measures discussed in the specialized literature, there is little discussion on the energy performance of the production and use of compressed air. This study developed a new approach to assess the energy performance of compressed air systems based on a six-step local energy benchmarking methodology. The methodology includes an energy management procedure to monitor and control the electricity consumption and sustain the energy performance of compressed air systems in time. The procedure monitors the production and use of compressed at plant and at manufacturing section levels based on the real-time monitoring of relevant variables to calculate energy performance indicators, energy baselines, and CUSUM charts. Monitoring the consumption of compressed air at the section level in a case study reduced the demand between 11 and 47%. While electricity consumption to produce compressed air at the plant level reduced by an estimated 23%. This approach permits the rapid detection of inefficiencies in the production and demand sides of the compressed air system, highlighting inefficiencies that are frequently hidden in the total electricity consumption of manufacturing plants.

Abstract Using the Bakken shale play as a case study, the previous part of this two-part series demonstrated how small-scale mobile plants could be used to monetize associated or stranded gas effectively. Here, we address the issue of uncertainty in future supply, demand and price conditions. To this end, we modified our multi-period optimization framework to a stochastic programming framework to account for various scenarios with different parameter realizations in the future. The maximum ENPV (expected net present value) obtained was $2.01 billion, higher than the NPV obtained in the previous part. In addition, the value of the stochastic solution was 0.11% of the optimal ENPV, indicating that the flexible nature of mobile plants affords them a great advantage when dealing with uncertainty.