• Energy Research
• Applied Energy close
• Chinese Academy of Sciences close

Abstract Microalgae have reported to be one of the most promising feedstock for biofuel production. However, microalgal cultivation for biofuel production is a costly process due to the large amounts of water, inorganic nutrients (mainly N and phosphate (P)), and CO2 needed. In this study, we evaluated whether the nutrient-rich ash and flue gas generated in biomass power plants could serve as a nutrient source for Chlorella sp. C2 cultivation to produce biolipids in a cost-efficient manner. When ash was incorporated in the culture medium and photosynthesis was enhanced by CO2 from flue gas, Chlorella cultures produced a lipid productivity of 99.11 mg L−1 d−1 and a biomass productivity of 0.31 g L−1 d−1, which are 39% and 35% more than the control cultures grown in BG11 medium. Additionally, the cultures reduced the nitrogen oxide (NOx) present in the flue gas and sequestered CO2, with a maximum ash denutrition rate of 13.33 g L−1 d−1, a NOx reduction (DeNOx) efficiency of ∼ 100%, and a CO2 sequestration rate of 0.46 g L−1 d−1. The residual medium was almost nutrient-free and suitable for recycling for continuous microalgal cultivation or farmland watering, or safely disposed off. Based on these results, we propose a technical strategy for biomass power plants in which the industrial wastes released during power generation nourish the microorganisms used to produce biofuel. Implementation of this strategy would enable carbon negative bioenergy production and impart significant environmental benefits.

Abstract Based on an extensive dataset containing aggregated hourly energy consumption readings of residents during March 2011 and October 2012 in South Ontario, Canada, this paper estimates the energy consumption of circulating pumps of residential swimming pools (CPRSP) non-intrusively, and quantifies the impact of CPRSP on the power system. The main challenges are that, first, widely used non-intrusive appliance load monitoring (NIALM) methods are not applicable to this work, due to the low sampling rate and the lack of the energy consumption pattern of CPRSP; second, temperature-based building energy disaggregation methods are not suitable for this work, as they highly depend on the accurate base load estimation and predefined parameters. To overcome these issues, in this paper, first it is found that, during the pool season, for homes with and without swimming pools, the ratio between their base loads is approximately equal to the ratio between their temperature-dependent energy consumptions, then a novel weighted difference change-point (WDCP) model has been proposed. The advantages of the WDCP model are that, on one hand, it doesn’t depend on the base load estimation and predefined parameters; on the other hand, it has no requirement on the data sampling rate and the prior information of energy consumption patterns of CPRSP. Based on the WDCP model it is shown that, the average hourly energy consumption of CPRSP is 0.7425 kW, and the minimum and the maximum hourly energy consumptions are 0.5274 kW at 9:00 and 0.9612 kW at 17:00, respectively. At the peak hour 19:00, July 21, 2011, CPRSP contributes 20.36% energy consumption of homes with swimming pools, as well as 8.48% peak load of all neighborhoods. As a result, the peak load could be reduced by 8.48% if all CPRSP are stopped during the peak hour.

As one of the three high-energy consumption sectors (industry, building, and transportation) in China, the transport sector faced a devastating resource and environment challenge. The transport sector was reportedly responsible for about 15.9% of the country’s total final energy consumption in 2008. This paper investigates the energy consumption and efficiency of China’s transport sector from 2003 to 2009. The transport energy data of 30 China administrative regions were divided into “three-belts” (Eastern, Western, and Central areas), and the corresponding turnovers were reported and analyzed using an index decomposition analysis (Logarithmic Mean Divisia Index). The energy data and turnover of the transport sector indicated that the high growth rate of turnover results is attributed to the high growth rate of diesel, assuming that diesel is the major fuel for freight transport. The growth of diesel is the main contributor to the overall growth of energy consumption. The growth rate of gasoline has become minimal since 2006. Since 2005, all three-belt areas, with regard to the effectiveness of energy conservation policies, have continuously improved their energy efficiencies based on the results of decomposition analysis. The energy intensity effect shows that the energy conservation and efficiency policies were more effective in the Central and Western areas than that in the Eastern area. On the other hand, the regional shift effect indicates that the policies favor to the Eastern area since only its regional shift effect contributes energy savings since 2008. The energy-mix effect is insignificant, which indicates that it is not necessary to conduct CO2 emission decomposition analysis due to the redundant observations. At last, the activity effect dominates the energy consumption increase (98.05% of the accumulated total energy increase) from 2003 to 2009, which is consistent with the rapid development of transportation in China. That is, the policies in the transport sector mainly focused on the economic development but the energy efficiencies in the study period.

Abstract Biodiesel production was catalyzed by a novel magnetic carbonaceous acid (Zr-CMC-SO3H@3Fe-C400) with both Bronsted and Lewis sites synthesized by a four-step method: (i) metal (Fe) ion chelation, (ii) calcination, (iii) metal (Zr) ion chelation and embedding, and (iv) sulfonation. It catalyzed the esterification of oleic acid with 97% biodiesel yield, transesterification of high acid value (AV) soybean oil with 95% biodiesel yield, and pretreatment of Jatropha oil with AV reduced from 17.2 to 0.7 mg KOH/g. Biodiesel yields (>90%) at 90 °C for 4 h reaction time were obtained for ten cycles by easy magnetic separation which showed potential practical applications in the field of green production. The synthesized catalyst was characterized with elemental analysis, XRD, ICP-OES, FT-IR, BET, VSM, SEM-EDX, HRTEM, TG-DSC and Boehm titration.

A 117.8 l three-dimensional pressure vessel is used to study the methane hydrate dissociation with the steam assisted gravity drainage (sagd) method. it is called the pilot-scale hydrate simulator (phs). this study proposes the evaluation and the comparisons of the gas production performance by sagd method from the methane hydrate reservoir with different steam injection rates. it indicates that the experiment could be divided into three main stages: the original gas releasing stage, the original and the hydrate-originating gas releasing stage, and the hydrate-originating gas releasing stage (the sagd process). furthermore, the temperature change consists of the four periods: decreasing dramatically, keeping stable, rising gradually, and keeping steady. with the injected steam flowing downwards and sideways, the steam chamber is expanding. the gas production rate increases with the steam injection rate, while the energy efficiency ratio (eer) and gas-to-water ratios are improved by the decrease of the steam injection rate. (c) 2013 elsevier ltd. all rights reserved.

Abstract Chemical looping gasification (CLG) is viewed as a promising gasification technology because gas phase oxygen of gasifying medium can be replaced by lattice oxygen of oxygen carrier. In the present work, the reactivity of biomass char with Fe2O3 oxygen carrier under different atmospheres was detailed investigated through the thermodynamic and thermo-gravimetric analysis. The Fe2O3 was almost completely reduced into metallic iron when the reaction temperature exceeded 1000 °C, but the carbon conversion of char only attained to 40.80% due to the lack of oxygen source under inert atmosphere. However, the carbon conversion of char apparently increased and the oxygen conversion of oxygen carrier dramatically decreased under oxidizing atmosphere (CO2, or H2O). It is attributed to the fact that oxidizing agents can supply oxygen sources to promote char conversion as well as to alleviate the reduction of oxygen carrier. These thermodynamic predictions were confirmed by TGA tests, where the char was fully converted into gas under CO2 or H2O atmosphere because of enough oxygen sources but a low carbon conversion was obtained under inert atmosphere. TGA results further indicated that the reactivity of char with oxygen carrier under steam atmosphere is much higher than that under CO2 atmosphere and the Fe2O3 phase is mainly reduced into Fe3O4 phase in all the tests. Additionally, several other different carriers (Al2O3, NiO-modified iron ore and NiO) were employed to compare the reactivity of iron ore as well. The order of reactivity is speculated as follows: Pure oxygen ≈ NiO > H2O > Iron ore > CO2 > Al2O3. The reduced oxygen carrier can recover entire lattice oxygen [O] to its initial state under air atmosphere. Therefore, it suggests that the Fe2O3 material used as an oxygen carrier can be recycled in the process of char CLG.

Abstract Current global resources of fossil fuels are gradually depleting and the energy crisis induces increasing concerns on the research of new effective substitution of these fossil fuels by renewable energy, especially bio-fuels from biomass such as bio-oils. However, bio-oils, generally originated from the pyrolysis of biomass, contain a great deal of carboxylic acids such as acetic acid and these acids can easily decrease the stability and the quality of oil. Meanwhile, these acids are highly corrosive to reaction equipments. Bio-oil could be upgraded before its utilization in the feedstocks of fuels and chemicals. In this work, the removing of these carboxylic acids was investigated by esterification in supercritical ethanol. The effects of reaction temperature, the ratio of ethanol to bio-oil, and reaction time on the conversion of acids were studied as well as the addition of external acid such as H2SO4, H3PO4 or zeolite. The results showed that carboxylic acids in crude bio-oil easily esterified with ethanol in the supercritical system. More ethyl acetate was formed at higher volume ratio of ethanol to bio-oil and 100% of the selectivity was achieved at the volume ratio of 5:1 after 2 h reaction, whereas more side reactions were present in lower or higher ratio of ethanol to bio-oil. The addition of external acid decreased distinctly the formation of esters, indicating that these carboxylic acids could be effectively removed under the acidic system arising from the internal ionization of ethanol. These would be very useful in the upgrading of bio-oil into high quality fuels in the future biorefinery.