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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 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.

Abstract This paper investigates the thermochemical and physical conversion processes of coal gasification numerically with particular interest on calcination in a bubbling fluidized bed furnace. A comprehensive Eulerian-Eulerian three-dimensional model is developed for studying the gasification process. Three calcination cases are carried out under different operating conditions while one inert case is conducted to evaluate the effect of calcination. The presented numerical results aim at determining the mechanism of coal gasification in an air-steam environment with different flowrates. Evidence of particle segregation is found in the bed of coal and limestone due to density reduction and diameter shrinkage. Char conversion is investigated for different air-coal and steam-coal ratios, also the effect of bed temperature, fluid flowrate and fuel feeding rate on the carbon conversion is studied comprehensively. The highest char conversion rate is observed in the airflow rate of 17.0 kg/h where the bed temperature is found to be maximum. A noticeable impact of calcination is found in the gaseous emission while increasing CO2 concentration. Time averaged solid and gas temperature and species concentration profiles indicate the steady-state condition of numerical simulation.

Abstract This work presents a simultaneous mixed-integer nonlinear programming (MINLP) optimisation model and an efficient iterative solution strategy that can be successfully applied to various heat-integrated water networks (HIWNs), including large-scale problems with a large number of water streams. These problems are highly nonlinear, non-convex and combinatorial. To circumvent such difficulties, including network complexity as well as identifying the roles of water streams in the heat exchanger network (HEN) whether they are hot or cold, a modified convex hull formulation proposed by Ahmetovic and Kravanja [1] is applied. The overall model combines the water network (WN), wastewater treatment network (WTN), heat integration (HI), and heat exchanger network synthesis (HENS) models. This model is iteratively solved in three steps including targeting and design steps. The proposed model and solution strategy are tested on large-scale problems. To the best of our knowledge, the results obtained for all the problems in this paper are better than those reported in the current literature.

Abstract In order to assess the feasibility of utilizing renewable hydrogen as transport fuel for fuel cell vehicles, four possible low-carbon hydrogen supply routes for a hydrogen refueling station located in Shanghai are studied. Route Ⅰ and II are onsite hydrogen supply routes powered by a stand-alone or grid-connected photovoltaic (PV)-wind generation system separately. Route Ⅲ and IV are offsite hydrogen supply routes, in which hydrogen is produced by a stand-alone or grid-connected PV-wind generation system located in Qinghai Province respectively and delivered via liquid hydrogen truck to Shanghai. The microgrid system for hydrogen production is designed and optimized with the aid of HOMER Pro® software. The results show that in hydrogen production stage, Route Ⅳ shows the best economic performance, both in the total net present cost (NPC) cost and levelized cost of energy (LCOE) cost. As for the whole hydrogen supply chain, Route IV is also the most economic hydrogen supply way, the levelized cost of hydrogen (LCOH) of which is slightly lower than that of Route II. The sensitivity results show that the total LCOH cost of Route Ⅳ is feasible based on the current shorter electrolyzer's lifetime. Therefore, it indicates that nowadays, producing hydrogen from a grid connected PV-wind hybrid power system in renewable energy rich area (Qinghai Province) and delivering it via liquid hydrogen truck to a refueling station in east coast area (Shanghai) of China may be a feasible solution.

Abstract Industry and agriculture in Malaysia are the main contributors to economic growth and employment. These sectors also play an important role in Malaysia's total exports. The question then is whether technological innovation, sectoral output, and exports growth have had a real impact on these two sectors, which are very important for policy-making. This paper attempts to empirically identify such relations using econometric methods, including an autoregressive distributed lag (ARDL) bounds testing method and a dynamic ordinary least squares (DOLS) during 1978–2018. The results confirmed that overall long-run economic growth is the main contributor to the increase in energy consumption with a greater magnitude than in the short-run. In the long-run, an increase of 1% in economic growth leads to an increase of 4.6% and 1.1% in energy demand in agriculture and industrial sectors, respectively. Exports are the second largest contributor to energy demand in the overall economy and the agriculture sector. Finally, the technological innovation that enhances energy efficiency is only effective in reducing energy consumption in the industrial sector, which ultimately reduces emissions.

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