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Abstract There was a rapid development of coal to synthetic natural gas (SNG) projects in the last few years in China. The research from our previous work and some other researchers have found coal based SNG production process has the problems of environmental pollution and emission transfer, including CO 2 emission, effluent discharge, and high energy consumption. This paper proposes a novel co-feed process of coal and coke-oven gas to SNG process by using a dry methane reforming unit to reduce CO 2 emissions, more hydrogen elements are introduced to improve resource efficiency. It is shown that the energy efficiency of the co-feed process increases by 4%, CO 2 emission and effluent discharge is reduced by 60% and 72%, whereas the production cost decreases by 16.7%, in comparison to the conventional coal to SNG process. As coke-oven gas is a waste gas in most of the coking plant, this process also allows to optimize the allocation of resources.

Abstract Since the establishment of the market economy in 1993, the residential consumption of commodities, including energy, has been highly influenced by prices in China. However, the contribution of the factors related to prices in residential energy consumption is relatively unexplored. This paper extends the KAYA identity with price and expenditure factors and then applies the LMDI method to a decomposition of residential energy consumption in China from 1993 to 2011. Our results show the following: (1) Though the prices of a majority of residential energy sources in China declined, the effect of energy prices restrained residential energy consumption because the expenditure structure changed during the period. (2) During the research period, the urban energy expenditure proportion experienced two progresses of rising and falling, and the rural proportion, which was stable before 2002, sharply increased. (3) The energy consumption intensity effect, which is the negative of the average energy price effect, contributed to most of the decrease in energy consumption, whereas residential income played a key role in the growth of consumption. According to the conclusions, we suggest further marketization and deregulation of energy prices, the promotion of advanced energy types and guidance for better energy consumption patterns.

Abstract This article identifies the sources and determines the convergence and causes of energy efficiency in Africa. In terms of contribution, it provides the first cross-country evidence. This study applies the stochastic fixed effect, true fixed effect and the Kumbhakar-Heshmati (K-H) models using a panel data of 22 countries for the period 1988–2014. The result reveals that: (1) the problem of energy efficiency in Africa is more structural in nature. Removing transient inefficiency and minimizing persistent inefficiency will save 5.7% and 84% of total energy consumption, respectively. Thus, energy security and carbon emissions will benefit more from policies aimed at the long-term than the short-term; (2) overall energy efficiency is low and hyoid in nature. While it declined from 1988 to 2006, the trend has reversed after 2006; (3) economic growth, urbanization and population density promote efficiency but price, foreign direct inflows and service and industry output reduce it; (4) energy efficiency convergence is conditional in nature, driven by country-specific factors such as the level of technology; (5) energy intensity is not a good measure of energy efficiency and should not be used as a policy indicator for energy efficiency enhancement.

Abstract The paper presents an exergo-economic analysis of humidification-dehumidification (HDH) desalination system operating under a conventional open-water open-air (OWOA) and a modified closed-water open-air (CWOA) configuration. Besides, the possibility of coupling a reverse osmosis (RO) system with HDH unit is also analyzed. The hybrid HDH-RO system is studied under three different retrofits including a simple HDH-RO, HDH-RO with a Pelton turbine and HDH-RO with a pressure exchanger. The analysis reveals that the modified cycle has a higher exergetic efficiency and lower product cost than the basic cycle. The product cost for the basic cycle with an electrical heater is calculated to be $6.56/m3 and with the solar heater $5.98/m3. Moreover, it is observed that the hybrid HDH-RO system with a pressure exchanger has the highest gained output ratio and second-law efficiency followed by HDH-RO with a Pelton turbine and simple HDH-RO, respectively. The product cost for hybrid HDH-RO with a pressure exchanger is calculated to be $0.13/m3 and $0.12/m3 with an electrical and solar heater, respectively.

Abstract Integrated systems consisted of solar energy and air source heat pump have been a hot research topic in recent decades due to their high efficiency and low environmental pollution. Recently, much attention has been paid to the performance characteristics of these systems, however, scarce of attention has been paid to indicate which kind of integrated systems have the optimal performance under different working conditions. For the integrated system of solar heating independently, the solar collectors have high heat-collecting temperature and high heat loss to ambient, so it has advantages in high solar radiation. For the integrated system of solar energy used for the low temperature heat source of heat pumps, the solar collectors have low heat-collecting temperature and low heat loss, so it has advantages in low solar radiation. But for the condition of medium solar radiation, both the above existing two types of systems may not be the optimal ones. Therefore, in this study, a novel integrated system was put forward for this condition. The characteristics and optimal working condition range of this novel system were comparatively studied by the simulation method. By comparison with the above existing two types of systems, the results proved that for most conditions of medium solar radiation, the novel system has the optimal performance, and its COP can be about 55% higher than that of the two types of existing systems when the outdoor temperature is −25 °C. An I-T diagram was proposed in this study to quantificationally divide the optimal working condition ranges of the three types of systems. This study can effectively guide the selection of optimal systems under different working conditions.

Abstract The annual electricity consumption analysis and forecasting of China is one of the important bases of management decision making for power generation groups as well as power policy adjusting for government. The socioeconomic actuality could not offer adequate observations with perfect statistic characters. The partial least squares method is applied to get a linear equation. It could quantificational simulate the relationship between the electricity consumption and its factors. The variables importance analysis method is further adopted to distinguish the explanatory power of all relative factors. The foremost importance of production and consumption in rural area shows that the development of this area should account more for the increasing of electricity consumption. The less explanatory power of the gross domestic product of tertiary industry means the gigantic potential in electricity consumption for the future several years. At last, it calculates the contributions of observations. The results show that the unusual development of real estate and relative industry has affected the usual electricity consumption mode. With the clear away of price bubble in real estate, the increasing speed of electricity consumption will slow down in the recent years.

More than 1800 hundreds of millions of beverage cans are manufactured yearly over the world, which will pollute the globe environment without recycle. The recycle and regeneration estates of used beverage cans are highly profitable enterprises. Vacuum technologies are mature on a large scale today, and therefore, the re-melting process of used beverage cans (UBCs) does not have to use flux. Furthermore, the coating on UBCs becomes the key factor causing poor product quality. The present paper concerns removing the coating of UBCs and compares two different kinds of methods to remove the coating: a thermal method and a chemical reagent method. A new kind of reagent, thick sulfuric acid, was employed in the chemical reagent de-coating process. The de-coating ratio in the thermal method reached 93% at most, but the de-coating ratio reached 100% within 30 min in the chemical reagent method by using thick sulfuric acid. Recycling the used thick sulfuric acid was also supplied. A titanium yellow product can be simultaneously obtained. The experiments show that the chemical reagent method is more available than the thermal method, which will enhance the purity of the regeneration product enormously.

Abstract The cement industry is an industry that consumes a considerable quantity of resources and energy and has a very large influence on the efficient use of global resources and energy. In this study, exergetic life cycle assessment is performed for the cement production process, and the energy efficiency and exergy efficiency of each system before and after waste heat power generation is investigated. The study indicates that, before carrying out a waste heat power generation project, the objective energy efficiencies of the raw material preparation system, pulverized coal preparation system and rotary kiln system are 39.4%, 10.8% and 50.2%, respectively, and the objective exergy efficiencies are 4.5%, 1.4% and 33.7%, respectively; after carrying out a waste heat power generation project, the objective energy efficiencies are 45.8%, 15.5% and 55.1%, respectively, and the objective exergy efficiencies are 7.8%, 2.8% and 38.1%, respectively. The waste heat power generation project can recover 3.7% of the total input exergy of a rotary kiln system and improve the objective exergy efficiencies of the above three systems. The study can identify degree of resource and energy utilization and the energy-saving effect of a waste heat power generation project on each system, and provide technical support for managers in the implementation of energy-saving schemes.

Methanol is an important platform chemical. The conversion of natural gas is the most widely used technology to produce methanol. With the development of chemical industry, the situation of energy shortage has become very serious. The exploration and adoption of renewable energy is an alternative way to solve the crisis of energy shortage. Wind energy is one of the most prominent energy source among all renewable energy sources in the Chinese energy markets. In this paper, wind energy integrated with natural-gas-to-methanol (WGTM) process is proposed. Performance analysis including carbon efficiency, energy efficiency, production cost, carbon reduction benefit, and impact of carbon tax is conducted. Based on the comparison results of NGTM (natural-gas-to-methanol) and WGTM (wind energy integrated with natural-gas-to-methanol), it can be concluded that the proposed system may be ready for industrialization at the near future. The wind energy integration provides a promising way to reduce carbon dioxide emission. The WGTM can be a flexible way to slow down the GHG effect.