• 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.

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 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.

Abstract Gas hydrate found in nature is mainly existed in deposit, such as marine deposit and permafrost. The thermophysical properties of the deposit are largely influenced by the formation features of gas hydrate, thereby affecting the hydrate production. In this manuscript, the experiments of formation and decomposition behavior of gas hydrate in the deposit with different grain sizes (40–60 mesh, 80–120 mesh, 325–400 mesh) and different thermal conductivities (0.926 W/m.K, 28.8 W/m.K, 41.9 W/m.K) were conducted in the small cubic hydrate simulator, and the coupling effect of the heat and mass transport on the hydrate formation and dissociation were researched. It was concluded that the mass transport rate in the deposit dominated the hydrate formation. The formation of gas hydrate was initial at the contact surfacing of gas–water and grew gradually in the gas-rich region, and the hydrate formation amount in the water-rich region was little. In the deposit with the grain size of 80–120 mesh and 325–400 mesh, there was no obvious induction time for the hydrate formation that occurred during gas injection. Be different from the hydrate formation, the heat transfer rate of the deposit restricted chiefly methane hydrate dissociation. With the raise of grain size and thermal conductivity of deposit, methane hydrate decomposition rate enhanced. It’s also found that the formed hydrate acted as cementation in porous medium with the grain size of 80–120 mesh and 325–400 mesh. The heat transfer rate of the deposit would significantly decrease when most of the cementation between the porous medium was disappeared as a result of hydrate dissociation, and the hydrate saturation in sediments at this time was defined as the critical hydrate saturation (50–80% of the initial hydrate saturation). The critical hydrate saturation is meaningful for gas hydrate resource prospecting and the risk assessment of gas hydrate production in actual fields.