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Abstract Compared with other traditional energy sources, renewable energy, which results the less pollution and has numerous resources, is a significant factor in addressing the current issues of the serious environmental pollution and the resource depletion. Large-scale renewable energy integrated to the grid could bring change in both morphological structure and operation modes of energy transmission. Therefore, it is necessary to research the evolution mechanism of the future transmission network with a high proportion of the renewable energy. In this paper, an evolution framework of power system with high proportion of renewable energy is proposed. Firstly, a network equivalence and simplification based on power transfer distribution factors (PTDFs) is proposed, which can effectively simplify the decision-making process of evolution of large-scale power system. Then, an annual production simulation (8760 h) which takes into account renewable energy and load fluctuations is used to find out the bottleneck of the power grid. Based on the above methods, evolution strategy of power system with high proportion of renewable energy is studied for finding out optimal expansion strategy. A real power system of Zhejiang province is used as a test system. Test results demonstrate the feasibility of the proposed evolution framework.

Abstract To alleviate the shortage of natural gas resource and ease carbon emissions, a novel solar-driven combined cooling, heating and power (CCHP) system is designed and optimized using the genetic algorithm in the work. Different from the process of direct combustion in a conventional CCHP system, natural gas is firstly converted into syngas by a solar-driven natural gas reforming step, which is consumed in an efficient tri-generation system. Energy, economic and environmental evaluations on five office buildings in different climate zones in China are implemented to validate the advantages of the proposed system. Results show that the annual maximum primary energy saving, total cost saving, and CO2 emission reduction are 69.76%, 49.80%, and 71.55%, respectively. The system located in severe cold zones, where solar energy is abundant and building requires more heat load in whole year, achieves the highest benefits in comparison with separate systems. Furthermore, the sensitivities on the price fluctuations of electricity, natural gas and solar field to the system profits are investigated, which indicates that the influence of electricity price on the system performance is the most significant. Thus, a promising method for reducing the natural gas consumption and improving the utilization efficiency of solar energy is provided.

In this study, Myriophyllum elatinoides growth under different nitrogen (N) concentrations (2, 250, 300, 350 and 400 mg L-1) and changes in rhizosphere bacterial community structure were investigated. High N (>300 mg L-1) concentrations caused reduction in M. elatinoides biomass. Growth tended to stabilize at 49 days. N concentration in roots were higher than that in stems and leaves under high N conditions. TN and NH4+ removal efficiencies reached 84.0% and 87.2%, respectively, in M. elatinoides surface flow constructed wetlands (SFCWs). Rhizosphere bacterial diversity increased over time. Proteobacteria, Firmicutes, Cyanobacteria, and Bacteroidetes dominated at the phylum level. Genera Turicibacter, Allochromatium, and Methylocystis increased at low N (<300 mg L-1) concentrations, while Pseudomonas increased at high N concentrations over the experimental period. Redundancy analysis showed that pH was strongly correlated with changes in rhizosphere bacterial community structure. These findings helped to insight into N removal mechanism in M. elatinoides.

There is a widely believed myth that replacing the use of fossil fuels largely by renewable forms of energy is, with a possible exception of nuclear power, critically dependent on the development of appropriate new technologies. Accordingly, it is held that decarbonizing straight away is particularly difficult and expensive. There was a time when this idea had an element of reality, but this is no longer the case. Unfortunately, belief in this myth is shared by those in positions of influence. This paper serves to document that this presumed reality no longer holds, although the misconception may have been based on fact in the past. Whilst the survey of the available technology offered concentrates on electricity supply, it also documents that manufacture of synthetic fuels via hydrogen obtained by electrolysis of water and CO2 integrates smoothly with electricity grid stabilization as well as reducing the CO2 content of the atmosphere. The likely price and cost development in the energy market is also reviewed. In addition the role of CCS, in practice mainly capture from the air and industrial processes other than power generation is reviewed against the background of the cost effective generation of electricity by harvesting renewable forms of energy.

Abstract A recent field survey provided eight typical soffits used in the residential houses within the typhoon-prone coastal region of southeastern China. Their aerodynamic effects in alleviating rooftop extreme wind pressures were evaluated via wind tunnel testing on a series of 1/20 gable roof house models. Local pressures, area-averaged pressures and uplift forces acting on roofs were examined. Results showed that in contrast to the model without soffits, the presence of these gutters or eaves gives a rise to a significant reduction of negative peak wind pressures at edges and corners near them. However, they hardly impact wind loads on the other roof surface. Some minor simple architectural elements attached to eaves, such as cantilevered spoiler and semicircular gutter, were observed to facilitate the reduction of extreme wind pressure at edges and corners. Additionally, the reduction rate of spatially averaged wind pressures with area was found to be dependent on the size of tributary area, rather than the shape of tributary area.

In a former study, a German lignite extract exhibited toxicity to Danio rerio and Caenorhabditis elegans and was shown to have mutagenic and dioxin-like activity. Besides the comparatively low content of known toxic polycyclic aromatic hydrocarbons (PAH), highly intensive peaks of m/z 274 and m/z 324 were observed during the chromatographic analysis. These compounds are assumed to be alkylated chrysenes and picenes (3,3,7-trimethyl-1,2,3,4-tetrahydrochrysene, 1,2-(1'-isopropylpropano)-7-methylchrysene and an isomer of the latter, 1,2,9-trimethyl-1,2,3,4-tetrahydropicene and 2,2,9-trimethyl-1,2,3,4-tetrahydropicene). These compounds are intermediates in the diagenetic formation of chrysene and picene from triterpenoids. Due to their general high abundance in lignites and the toxicity observed for the lignite extract, the mechanism-specific toxicity and bioavailability of these compounds were investigated in the present study using the approach of effect-directed analysis. After the separation of the compounds from other PAH, their mutagenic activity (Ames Fluctuation test) and dioxin-like activity (EROD activity) were studied. Both, mutation induction factor (up to 2.9±2.7) and dioxin-like activity (Bio-TEQ of 224±75 pg/g; represents the amount (pg) 2,3,7,8-tetrachlorodibenzo-p-dioxin per g coal that would provoke the same toxic effect) were rather low. Bioavailability estimated by the bioaccumulation test with Lumbriculus variegatus was also very limited. Based on the obtained results, the environmental risk of the highly abundant alkylated chrysenes and picenes in lignites is concluded to be low.

Abstract Bioenergy crops are one of the renewable energy options available to decarbonise the energy sector in Scotland and help to achieve the overall planned target of 80% reduction in greenhouse gas (GHG) emissions by 2050. A process-based model for poplar and willow developed for simulating the effect of different environmental and management options on growth and biomass yield was used to estimate the GHG abatement potential (GHG-AP) under different crop management options in Scotland. The model results of annual wood yield did not show a strong relation with any of the environmental factors except that of initial soil organic carbon (SOC) content. Increasing plant density and decreasing harvest frequency increased GHG-AP. Application of N-fertilizers at a rate of 50–100 kg N ha−1 resulted in the buildup of carbon in soils with less than 180 Mg C ha−1. However, in soils with greater SOC contents, annual emissions resulting from N fertilizer application were greater than the carbon saving through marginal increases in wood yield and SOC changes. The best management scenario in terms of economic and environmental objectives depends on identifying an optimum plant density based on the site specific conditions with a fertilizer application of 20–100 kg ha−1 y−1 and a five year harvest interval. Even under the best economic scenarios, SRC willow and poplar have a GHG-AP ranging from 9.9 to 11.6 and 8.8–10.0 Mg CO2 eq. ha−1 y−1, respectively. Under the best environmental scenarios this range increases to 10.5- 13.2 and 9–11.1 Mg CO2 eq. ha−1 y−1 for willow and poplar, respectively.

Abstract Spark-ignition (SI) aviation piston engines are widely used on light helicopters and unmanned aerial vehicles (UAVs) because of the high-power density and ultra-high cost performance. Kerosene with high flash point is expected to improve safety of aforementioned aircrafts by replacing gasoline. However, in spark-ignition mode, kerosene is difficult to mix and is easy to knock. Short-chain alcohols have high volatility and octane number which can just make up for some defects of kerosene. In this paper, three kinds of alcohols including ethanol, n-propanol and n-butanol were blended with aviation kerosene (RP-3) by volume fraction of 30%, 50%, 70%, respectively. The combustion and emission characteristics of the blended fuels were deeply studied on a typical spark-ignition aviation piston engine. Meanwhile, engine performance fueled with commercial gasoline was also tested for comparison. Results indicated that alcohol/kerosene blends could reach higher brake thermal efficiency (BTE) (alcohol ratio ≥50%) compared to gasoline. Carbon monoxide (CO) and nitrogen oxides (NOx) emissions of blended fuels expressed dramatically descending. With the increase in alcohol ratio, the CO, hydrocarbons (HC) and soot emissions gradually decreased. The brake thermal efficiency showed an upward trend with the increase of alcohol ratios. The brake thermal efficiency of E70, P70 and B70 were increased by 2.15%, 3.52% and 6.51%, and the CO emissions of E70, P70 and B70 were reduced by 39.8%, 38.5% and 49.0%, respectively, compared to those of gasoline. Notably, n-butanol/kerosene blends exhibited the better combustion and emission characteristics, which had the higher efficiency and lower CO, HC and soot emissions.

Abstract In arid areas, dry cooling technology is a preferable alternate of wet cooling mainly owing to the scarcity of abundant water supply. However, the supercritical CO2 power cycle still offers considerable thermal performance even at higher ambient temperature using dry cooling. The novelty of this work is the exhaustive designing of dry cooler for supercritical CO2 cycles (recompression and partial cooling) in concentrating solar power application. Prior to the design of tower, a preliminary analysis is conducted in achieving the optimum main compressor inlet temperature (33 °C-recompression and 40 °C-partial cooling) at which the cycle delivers the maximal efficiency. The comparison is performed at same higher and lower pressure and for the partial cooling, the intermediate pressure is optimized. At relatively higher compressor inlet temperatures (above 50 °C), the partial cooling achieves higher efficiency while at lower temperatures (30–49 °C), the recompression shows superior performance. An iterative nodal method is used for the air-cooled finned tube heat exchanger units that takes account of the dramatic variation in thermodynamic properties of CO2 with the bulk temperature. Kroger’s detailed methodology of designing dry cooler is adapted with the implementation of nodal approach for CO2 property variation. A dry cooling tower with 52.45 m height is essential for the recompression cycle, whereas the partial cooling requires two towers of the height of 35.4 m and 38.7 m. A thermal assessment is carried out on the dry cooler under various cycle fluid inlet temperatures and ambient temperatures. During hot and humid ambient conditions, lower compressor inlet temperatures (up to 53.1 °C) are obtained with the recompression cycle compared to partial cooling (up to 64.5 °C). In extreme climate condition of 50 °C air temperature, the recompression cycle provides superior thermal efficiency (46.5% against 45.5%). For future commercialization of dry cooled sCO2 power plant, the recompression cycle is preferred due to its superior performance and lower capital cost for cooling tower design and solar field. The work demonstrates the impact of dry cooling tower design strategy in the context of cycle thermal assessment under various working condition.