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Abstract In this paper, we examine the electrical power-generation potential of a domestic-scale solar combined heating and power (S-CHP) system featuring an organic Rankine cycle (ORC) engine and a 15-m 2 non-concentrated solar-thermal collector array. The system is simulated with a range of organic working fluids and its performance is optimised for operation in the UK climate. The findings are applicable to similar geographical locations with significant cloud coverage, a low solar resource and limited installation areas. A key feature of the system’s design is the implementation of fixed fluid flow-rates during operation in order to avoid penalties in the performance of components suffered at part-load. Steady operation under varying solar irradiance conditions is provided by way of a working-fluid buffer vessel at the evaporator outlet, which is maintained at the evaporation temperature and pressure of the ORC. By incorporating a two-stage solar collector/evaporator configuration, a maximum net annual electrical work output of 1070 kW h yr −1 (continuous average power of 122 W) and a solar-to-electrical efficiency of 6.3% is reported with HFC-245ca as the working fluid at an optimal evaporation saturation temperature of 126 °C (corresponding to an evaporation pressure of 16.2 bar). This is equivalent to ∼32% of the electricity demand of a typical/average UK home, and represents an improvement of more than 50% over a recent effort by the same authors based on an earlier S-CHP system configuration and HFC-245fa as the working fluid [1] , thus highlighting the gains possible when using optimal system configurations and fluids and suggesting that significant further improvements may be possible. A performance and simple cost comparison with stand-alone, side-by-side PV and solar-thermal heating systems is presented.

The present study explores the potential of artificial neural network to predict the performance and exhaust emissions of an existing single cylinder four-stroke CRDI engine under varying EGR strategies. Based on the experimental data an ANN model is developed to predict BSFC, BTE, CO2, NOx and PM with load, fuel injection pressure, EGR and fuel injected per cycle as input parameters for the network. The study was carried out with 70% of total experimental data selected for training the neural network, 15% for the network’s cross-validation and remaining 15% data has been used for testing the performance of the trained network. The developed ANN model was capable of predicting the performance and emissions of the experimental engine with excellent agreement as observed from correlation coefficients within the range of 0.987–0.999, mean absolute percentage error in the range of 1.1–4.57% with noticeably low root mean square errors. In addition to common correlation coefficients, the present study incorporated special statistical error and performance metrics such as mean square relative error, forecasting uncertainty Theil U2, Nash–Sutcliffe Coefficient of Efficiency and Kling–Gupta Efficiency. Low values of MSRE and Theil U2 combined with commendable indices of NSE and KGE proved beyond doubt the robustness and applicability of the model so developed. Furthermore, the developed ANN model was capable of mapping the PM–NOx–BSFC trade-off potential of the CRDI operation under EGR for all cases of actual observations with significant accuracy.

Abstract The paper presents a cradle-to-grave life cycle assessment for two domestic solar hot water systems. The first consists of polypropylene unglazed solar panels coupled with a 300-l storage tank; the second one consists of a traditional system with glazed solar panels coupled with a thermal storage of the same volume. Life cycle assessment was conducted according to the Eco-Indicator 99 methodology, Egalitarian Approach, yielding 49.7 and 18.3 eco-indicator points for the glazed and unglazed panels systems, respectively. In addition, for each domestic solar hot water system, the energy, CO 2 and economic payback times were calculated. In order to take into account the influence of local climate on the solar panels yield evaluate, the systems performance was simulated for three different locations: Rome, Madrid and Munich. The payback times were evaluated with respect to both natural gas and electrical boilers. The Energy Payback Time of the unglazed panel system ranges between 2 and 5 months, that of the glazed panel between 5 and 12 months. The CO 2 Payback Time of the unglazed panel system ranges between 1 and 2 months, that of the glazed panel between 12 and 30 months. The economic payback time, if compared with natural gas boiler, is in the range 9–11 years/8–13 years for the system with unglazed/glazed panels, respectively; if compared with the electrical boiler, it is in the range of 3–4 years for the system with unglazed panels and 4 years for that with glazed panels. The different national costs of natural gas and/or electricity play an important role in the economic payback times. Indeed, in Munich, the smaller energy savings achieved with the renewable systems are offset by the higher costs of these commodities.

Abstract A novel calcium looping (CaL) process integrated with a spent bleaching clay (SBC) treatment is proposed whereby fuels and/or heat from regeneration of SBC provide extra energy for the calcination process, in addition, the regenerated SBC can be used to synthesize enhanced CaO-based sorbents. Different kinds of composite samples were prepared with the regenerated SBC and/or aluminate cement at various doping ratios via a pelletization process. All pellets were subjected to thermogravimetic analyzer tests employing severe reaction conditions to determine the optimal doping ratios and regeneration method for the SBC based sorbents. These results demonstrate that pellets containing combustible components showed higher CO2 uptakes, due to the improved pore structure, which was verified by N2 adsorption measurements. The as-prepared sorbent “L-10PC” (90 wt.% CaO/10 wt.% pyrolytic SBC) achieved a final CO2 uptake of 0.164 g(CO2) g(calcined sorbent)−1 after 20 cycles, which was 67.3% higher than that of natural limestone particle. A new larnite (Ca2SiO4) phase was detected by X-ray diffraction analysis, however the weak diffraction peak associated with it indicated a low content of larnite in the pellets, which produced a smaller effect on performance compared to cement. A synergistic effect was achieved for a sample designated as “L-5PC-10CA” (85 wt.% CaO/5 wt.% pyrolytic SBC /10 wt.% cement), which resulted in the highest final uptake of 0.208 g(CO2) g(calcined sorbent)−1 after 20 cycles. Considering the simplicity of pyrolysis regeneration process and the excellent capture capability of pellets doped by pyrolytic SBC, the proposed system integrating CaL with SBC pyrolysis treatment appears to offer particular promise for further development.

Abstract The integration of different technologies acts as a leverage in boosting “circular economy” and improving resource use efficiency. In this respect, the coupling of anaerobic digestion with pyrolysis was the focus of this work. Solid-digestate obtained from anaerobic digestion was addressed to supply pyrolysis thus increasing the net energy gains and obtaining “biochar” (called “pyrochar” in our case) to be used as soil amendment alternatively to solid-digestate. The current interest on biochar is linked to its long-term soil carbon sequestration, thus contributing to global warming mitigation. A parallel detailed screening of the physical and chemical properties of both solid-digestate and pyrochar was performed, inferring their effects on soil quality. Results showed that while P and K are enriched in pyrochar, total N showed no significant differences. Heavy metals revealed higher concentrations in pyrochar, but always largely below the biochar quality thresholds. Pyrochar exhibited a higher surface area (49–88 m 2 g −1 ), a greater water holding capacity (352–366%), and a more recalcitrant carbon structure. Both solid-digestate and pyrochar showed good soil amendments properties but with complementary effects. Although starting from the same biomass, being the original feedstock processed differently, their ability to improve the physical and chemical soil properties has proved to be different. While several other soil improvers of organic origin can substitute digestate, the important role played by biochar appears not-replaceable considering its precious “carbon negative” action.

This paper assesses the energy and water consumption practices of existing housing in Saudi Arabia, with the ultimate aim of establishing guidelines for delivering sustainable residential buildings in the near future. In order to achieve this aim the current status of a typical Saudi residence (i.e. an apartment complex) is investigated in terms of energy and water consumption using simulation software packages. The paper then examines the prospects for applying various measures to the typical Saudi residence to manage energy and water use more sustainably. This research identifies several design-related faults common to Saudi Arabian house design. These faults contribute to an inefficient use of energy and domestic water resources. Finally, the paper puts forward a set of recommendations and guidelines, design-related and otherwise, to enhance the sustainability of future Saudi residential buildings.

Abstract Conversion of biomass into biofuel and biochar with a subsequent soil storage is assumed as a prospective strategy of reducing atmospheric CO2 concentrations. However, substantial uncertainties exist in this field regarding the country-level potential of biochar carbon sequestration, indirect effects of biochar implementation on overall environment, and dominating factors. This study conducted a life cycle assessment of country-wide incorporation of biochar in agriculture, and associated potential benefits. Results showed that over 920 kg CO2e (CO2-equivalent) could be sequestrated via converting 1 t of crop residues into biochar. As an example, based on crop residues availability statistics for China in 2014, the estimated annual carbon sequestration potential could be as high as 0.50 Pg CO2e (1 Pg = 1 × 109 t). The most significant potential for biochar carbon sequestration was identified in the central south, east and northeast of China, which contributed 65% of the national biochar carbon sequestration potential. The biochar system could also contribute to mitigation of the following environmental problems: marine aquatic biodiversity destruction, surface soil and water acidification, etc. Sensitivity analysis demonstrated that biochar yield, carbon content in biochar, electricity conversion efficiencies of bio-oil and pyrolysis gas were the critical parameters determining the biochar system’s overall carbon sequestration potential and environmental effects. This study provides guidance on evaluating biochar’s potential carbon sequestration capacity and comprehensive environmental impacts, as well as research and development needs.