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China’s research on and specific implementation of energy saving for buildings are mainly concentrated in urban areas, but according to 2016 statistics, the rural population accounts for 42.65% of the total population, so rural housing has considerable energy-saving potential. However, the degree of attention to the energy consumption of rural houses needs to be improved. Regarding the research on and implementation of passive energy-saving strategies for residences, compared with centralized urban high-rise residences, rural residences mainly have independent courtyards, with a flexible layout and easier transformation. In this study, a system that uses the common cold lanes in traditional villages and buildings’ exterior walls was constructed, and the indoor spaces of courtyard buildings in southern Shaanxi were completely passively cooled in summer. This system can be completely separated from the supply of artificial energy by relying on the accumulation and buoyancy effects of air in patios and cold lanes and the hot-pressure ventilation in buildings to cool the buildings and greatly improve indoor ventilation efficiency. As the building is ventilated and cooled, the air wall formed in the system can effectively prevent direct contact between the outdoor and indoor temperatures and reduce the impact of thermal wall radiation on the interior. In previous studies on the passive design of courtyard houses, scholars considered the effect of thermal wall radiation on indoor temperature in simulations. Therefore, in this study, we also separately calculated whether to consider the difference between the situation with and without wall heat radiation (WHR) when simulating thermal conversion. The final results show that when the cooling system was adopted, the annual cooling load of the whole building was 4786.494 kW·h without WHR. However, with WHR, the cooling load reduction was 2989.128 kW·h, a difference of 1797.336 kW·h.

This paper presents a multi-objective optimization model for a long-term generation mix in Indonesia. The objective of this work is to assess the economic, environment, and adequacy of local energy sources. The model includes two competing objective functions to seek the lowest cost of generation and the lowest CO2 emissions while considering technology diffusion. The scenarios include the use of fossil reserves with or without the constraints of the reserve to production ratio and exports. The results indicate that Indonesia should develop all renewable energy and requires imported coal and natural gas. If all fossil resources were upgraded to reserves, electricity demand in 2050 could be met by domestic energy sources. The maximum share of renewable energy that can be achieved in 2050 is 33% with and 80% without technology diffusion. The least cost optimization produces lower generation costs than the least CO2 emissions, as well as the combined scenario. Total CO2 emissions in 2050 are five to six times as large as current emissions. The least CO2 emissions scenario can reduce almost half of the CO2 emissions of the least cost scenario by 2050. The proposed multi-objective optimization model leads some optimal solutions for a more sustainable electricity system.

This study aims to identify potential hydropower sites and calculate the theoretical potential hydropower capacity based on watershed modelling of the Mindanao River Basin (MRB) in the Philippines for the sustainable development of a previously unstudied region. The Soil and Water Assessment Tool (SWAT) was applied to delineate the watershed of the MRB and simulate the river discharges with inputs from observed precipitation and global gridded precipitation datasets. Observed weather data, such as temperature, humidity, and solar radiation, from four meteorological stations in the Philippines were also used as inputs for SWAT modelling. Simulated discharges were calibrated at three river gauges on the Nituan, Libungan and Pulangi Rivers. However, due to limited river discharge records, model validations were conducted in proxy basins: the calibrated model parameters in river A were used in the watershed modelling of proxy river B. Of the delineated 107 sub-basins in the MRB watershed, only 33 were identified as having potential sites for hydropower development. These potential sub-basins hosted a total of 154 potential sites with an estimated monthly average power capacity of 5,551.35 MW for all 33 sub-basins. The estimated theoretical power capacity of 15,266.22 MW for all sites in the MRB is approximately equivalent to the Philippines’ total available power capacity in 2017 of 15,393 MW. These sites were classified into 16 mini-scale hydropower sites, 114 small-scale hydropower sites and 24 medium-scale hydropower sites based on the simulated river discharges and potential power capacities. Based on these results, hydropower development could be an alternative to strengthen the exploration of renewable energy resources and improve the energy situation in Mindanao; hydropower development could also have mitigation effects on frequent floods in flat, low-lying downstream areas.

Cavity growth occurring with crack extension and coal consumption during UCG processes directly influences the gasification efficiency and the estimated subsidence and gas leakage to the surface. This report presents an evaluation of the gas energy recovery, coal consumption, and gasification cavity estimation using a proposed stoichiometric method to analyze the coal gasification reaction process. We defined the evaluation parameters of rate of energy recovery and investigated the effects of different parameters using UCG trials conducted with coal blocks and coal seams, adopting different Linking-hole methods and operational parameters. Analyses of results obtained from laboratory experiments and small-scale field trials using V-shaped and L-shaped linking holes, and Coaxial-hole UCG models show that the gasification of Linking-hole models yielded average calorific values of product gas as high as 10.26, 11.11 MJ/m3 (lab.), and 14.39 MJ/m3 (field.). In contrast, the Coaxial-hole models under experimental conditions yielded average calorific values of product gas as: 7.38, 4.70 MJ/m3 (lab.) and 6.66 MJ/m3 (field.). The cavity volume obtained with Coaxial models was about half of the volume obtained from Linking-hole models. Results obtained for these UCG systems show that the feed gas and linking-hole types can influence coal consumption and product gas energy. Fissure ratios were also investigated. Results confirmed major factors underpinning gasification efficiency. Linking-hole types strongly influenced the development of the oxidization surface and fracture cracks for subsequent combustion in the gasification zone. Estimated gas energy recovery results support experimental observations within an acceptable error range of about 10%. Moreover, this stoichiometric approach is simple and useful for evaluating the underground cavity during UCG. Based on these results, we proposed a definition of the energy recovery rate, combined with the obtained volumes of gasification cavities that provide a definition of energy recovery and UCG effects. UCGにおいては，炭層内のき裂進展に伴う燃焼空洞の拡大と石炭の消費が重要であり，これがガス化効率や安全性 (地盤沈下，ガス漏洩等) に大きく影響する。本研究では，ガス化効率，回収エネルギーとガス化空洞の評価方法として，化学量論および化学平衡に基づく評価手法を検討した。生成ガス組成と求めたガス化反応式から，石炭の消費量，ガス生産量等を推定する方法である。また，エネルギー回収率を定義し，UCG室内モデル実験及び露天炭鉱の炭層で行った小規模現場実験の結果を評価し，リンキングの方式や注入ガス等のパラメータがガス化効率やガス化空洞の成長に与える影響を検討した。リンキングの方式として，L字，V字，同軸型のUCG実験を行い，ガス化効率の違いと，その原因を明らかにした。すなわち，リンキング型と同軸型モデルを比較すると，リンキング型UCGモデルの方が発熱量が高く，平均発熱量では，前者が10.26/11.11 MJ/m3 (室内) ，14.39 MJ/m3 (現場) であった。一方，同軸型モデル試験では，7.38/4.70 MJ/m3 (室内) と6.66 MJ/m3 (現場) と低い値であった。実験後の空洞体積の直接評価結果でも，リンキング型の方がガス化領域が拡大していることを確認した。リンキング方式の方が，炭層内にき裂を連続的に進展させやすいためと考えられる。また，エネルギー回収率の評価では，実験前後の供試体質量差から求めたエネルギー回収率と比較検討を行った。その結果，両者の誤差は約10％で，検討した手法によりエネルギー回収率や燃焼ガス化領域の石炭消費量を推定できることがわかった。以上の結果より，検討した化学量論法よる回収エネルギー評価手法は簡便で，実用的であることが明らかになった。 Special Edition for Coal Energy Technology; Development and Utilization of Coal Energy

This paper presents experimental results of the impact of CO(2) co-feed on a gasification/pyrolysis process for various feedstocks (biomass, coal, and municipal solid waste (MSW)). Various feedstocks were thermo-gravimetrically characterized under various atmospheric conditions and heating rates. A substantial amount of char burn out was identified in the presence of CO(2) via a series of thermo-gravimetric analysis tests, which enabled high conversion of final mass (approximately 99%) to be achieved. The impact of CO(2) co-feed on the volatilization regime during the pyrolysis/gasification process was not apparent at a heating rate of 10-40 degrees C min(-1). However, the impact of CO(2) on the volatilization regime at a fast heating rate (950 degrees C min(-1)) was substantial. For example, significant enhancement in the generation of CO, by a factor of approximately 2, was observed in the presence of CO(2). The generation of major chemical species, such as CH(4) and C(2)H(4), were enhanced, but this was not as apparent as in the case with CO. In addition, introducing CO(2) to the pyrolysis/gasification process enabled the amount of condensable liquid hydrocarbons, such as tar (approximately 30-40%) to be significantly reduced in the presence of CO(2), in that injecting CO(2) into the pyrolysis/gasification process expedites cracking the volatilized chemical species. Experimental work confirmed that biomass and MSW could be feasible and desirable feedstocks for the pyrolysis/gasification process as these feedstocks can be easily treated compared to coal. To extend this understanding to a more practical level, various feedstocks were tested in a tubular reactor and drop tube reactor under various experimental conditions.

COVID-19 pandemic has brought tremendous environmental burden due to huge amount of medical wastes (about 54,000 t/d as of November 22, 2020), including face mask, gloves, clothes, goggles, and sanitizer/disinfectant containers. A proper waste management is urgently required to mitigate the spread of the disease, minimize the environmental impacts, and take their potential advantages for further utilization. This work provides a prospective review on the possible thermochemical treatments for those COVID-19 related medical wastes (CMW), as well as their possible conversion to fuels. The characteristics of each waste are initially analyzed and described, especially their potential as energy source. It is clear that most of CMWs are dominated by plastic polymers. Thermochemical processes, including incineration, torrefaction, pyrolysis, and gasification, are reviewed in terms of applicability for CMW. In addition, the mechanical treatment of CMW into sanitized refuse-derived fuel (SRDF) is also discussed as the preliminary stage before thermochemical conversion. In terms of material flexibility, incineration is practically applicable for all types of CMW, although it has the highest potential to emit the largest amount of CO2 and other harmful gasses. Furthermore, gasification and pyrolysis are considered promising in terms of energy conversion efficiency and environmental impacts. On the other hand, carbonization faces several technical problems following thermal degradation due to insufficient operating temperature.

Since the great east Japan earthquake, photovoltaic (PV) and wind generator (WG) are introduced actively as a solution regarding shortage of electrical power with the stopping of nuclear power plants. Renewable energy source such as PV generator and WG contribute for prevention of global warming because these energy dose not use fossil fuels and it can reduce carbon dioxide emissions. However, it is difficult to predict renewable energy facility output because this output depends on weather conditions. It may reduce power quality. As a countermeasure of the fluctuation of power output, battery energy storage system (BESS) is introduced into power system. BESS is very effective facility because it can compensate the surplus and shortage power by charging and discharging. However, it is necessary to investigate the high cost for installation of large BESS. Thus, the fuel cell and the hydrogen generation apparatus are installed in the proposed scheduling method. The fuel cell can absorb surplus power, and surplus power is converted into hydrogen and it is accumulated by hydrogen storage device. Furthermore, it is possible to generate power easily by using the hydrogen which is stored in the fuel cell, when the shortage power occurs. As a consequence, the high-efficiency operation plan is determined to reduce the operation cost which had been accomplished, by introducing the fuel cell and the hydrogen generation apparatus.

In deregulated power systems, it is very important to make electricity demand more flexible in order to secure market-based system operation from power system operator's point of view. Also, as one of energy conservation technologies in Japanese residential houses, home-cogeneration systems such as gas engine-type and polymer electrolyte fuel cell-type (PEFC) is highly expected because exhausted heat of gas-engine or PEFC can be utilized for hot water demand. This paper assumes a new cooperation framework between cogeneration's owners and power system operator in order to attain more secure power system operation. In the cooperation framework, from cogeneration owner's point of view, the authors evaluate an influence of the integrated control of gas engine-type cogeneration systems on economic factor and energy conservation for cogeneration's owner.