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Abstract In many European countries the production of combined heat and power based on renewable energies is well established though the efficient and economical operation of such plants remains a challenging task. This also applies to the existing district heating network at Baden-Dattwil (Switzerland) where a conventional gas boiler is substituted by a wood-fired boiler comprising an Organic Rankine Cycle. An overall control strategy that allows fully exploring governmental incentives is therefore of paramount importance. In addition, the highly fluctuating heat demands combined with the thermal inertia of the different plant components impose demanding requirements to the control system to guarantee a stable as well as highly efficient operation. The overall control concept is successfully tested and verified by means of dynamic simulations of the overall plant with a simplified model for the district heating network. The models are implemented using the object oriented modeling language Modelica. The overall model is based on open source Modelica libraries such as ThermoCycle, Modelica Standard Library and StateGraph2 as well as on own Modelica models. The overall model is prepared to be coupled to the real plant control system which will allow virtual commissioning in the next step. This allows pre-tuning of control parameters as well as a weakness analysis which again helps to speed up the commissioning process. In General, the dynamic simulations proved to be a useful tool that deepened the insight and understanding of the plant operation at an early project phase and therefore greatly supported the making of design decisions. After commissioning, the calibrated simulation models will be used for monitoring purposes.

An empirical model of global solar irradiance (EMGSI) under all sky conditions was developed by using solar radiation and meteorological parameters at Sodankylä. The calculated hourly global solar irradiance is in agreement with that observed at the ground during 2008–2011 and at the top of the atmosphere (TOA). This model is used to calculate the global solar irradiance at the ground and its attenuation in the atmosphere due to absorbing and scattering substances in 2000–2018. The sensitivity test indicates that the responses of global solar irradiance to changes in water vapor and scattering factors are nonlinear and negative, and global solar irradiance is more sensitive to changes in scattering (expressed by the scattering factor S/G, S and G are diffuse and global solar radiation, respectively) than to changes in water vapor. Using this empirical model, we calculated the albedos at the TOA and the surface, which are in agreement with the satellite-retrieved values. A good relationship between S/G and aerosol optical depth (AOD) was determined and used to estimate AOD in 2000–2018. An empirical model for estimation of tropospheric NO2 vertical column density (VCD) was also developed and used to calculate tropospheric NO2 VCD in 2000–2018. During 2000–2018, the estimated global solar irradiance decreased by 0.92%, and diffuse irradiance increased by 1.28% per year, which is ascribed to the increases of S/G (1.73%) and water vapor (0.43%). Annual surface air temperature increases by 0.07 °C per year. Annual mean loss of global solar irradiance caused by absorbing and scattering substances and total loss are 1.94, 1.17 and 3.11 MJ m−2, respectively. Annual mean losses of absorbing and scattering global solar irradiance show negative and positive trends, respectively, and the annual total loss increases by 0.24% per year. Annual mean losses due to absorption were much larger than those due to scattering. The calculated albedos at the TOA are smaller than at the surface. The calculated and satellite-retrieved annual albedos decrease at the TOA and increase at the surface. During 2000–2018, annual means of the AOD and the tropospheric NO2 VCD increased by 8.23% and 0.03% per year, respectively.

Abstract Ammonia (NH3) emissions from gasoline-fueled vehicles have become an important source of pollution affecting urban air chemistry. NH3 influences the acidity of atmospheric depositions and it is involved in secondary aerosol formation. NH3 has to be considered as a secondary pollutant of the three-way-catalyst (TWC), since it is formed de novo during the DeNOx process. The extent of traffic-related hydrogen (H2) emissions and its impact on atmospheric redox chemistry is not well understood but is of increasing importance when we develop towards a hydrogen-based society. Herein we report on tail-pipe H2, NH3, and NO emissions of gasoline-fueled Euro-3 passenger cars at transient driving from 0 to 150 km h−1. The effects of velocity, acceleration, deceleration, and cold start were deduced from time-resolved EI- and CI-MS data. On a molar basis, H2 emissions were always higher than those of NH3 and NO by about an order of magnitude. H2 and NH3 emissions are correlated to some degree, as soon as catalyst light-off occurred. NH3 emissions exceeded those of NO for most vehicle conditions. Mean NH3/NO mixing ratios around two were observed with the exception of the cold start, where NO was present in large excess. Catalyst light-off is indicated by a fast transition from a NO- to a NH3-rich exhaust gas. All emissions clearly depend on speed and acceleration. Mean velocity-dependent emission factors varied by about one order of magnitude from 17 to 720, 8 to 170, and 7 to 80 mg km−1 for H2, NH3, and NO, respectively, with emission minima for all three pollutants when driving 70–90 km h−1. We conclude that the investigated Euro-3 vehicles are mainly operated under slightly reducing conditions, where NH3 and H2 emissions dominate over those of NO. Under these conditions, all vehicles fulfill the valid emission limit for NOx.

Abstract Life, on earth, is active only because of water devouring. Nature has provided a number of water resources such as surface water for instance rivers, lakes, springs, ground water and so on. By artificial means, man has created water storage systems such as excavated dams, check dams, reservoirs, tanks etc., to meet the basic water requirements throughout the year. But ever-growing population and poor water management skills of individuals have driven the globe towards serious water crisis. Solar distillation fills the gap between water scarcity and water productivity and remains one of the simplest methods of producing pure drinking water. Though many models in solar stills are being used across the globe, tilted wick type still excels with outstanding performance in the production of pure water. In this review, an attempt has been made in particular to study the factors that are involved in increasing the performance of tilted wick type solar distillation stills. This review covered the initiatives taken from the year 1985 being the first initiative in tilted wick type model to final tilted wick model on 2020 based on published articles.

The article presents new empirical material from a case study on longstanding, pioneering efforts on implementation and use of solar mini-grid systems in the Sunderban Islands in India. These local, socio-technical experiments have been investigated by a trans-disciplinary team of researchers and practitioners in order to gain a deep understanding of the diversity of social and technical factors influencing the ways in which the systems work at different levels. This socio-technical research highlights the dynamics between technology and society and how they are mutually influencing and shaping each other. These dynamics create gradual changes in the socio-technical system of technical devises, people, practices, knowledge and other elements, requiring adjustments also by the implementing actors. A range of technical and non-technical factors at various levels are found to be relevant for the implementation, operation, sustenance and further development of the solar power supply systems. The research points to important factors that should be taken into account and considered when planning similar activities. In addition to the analysis of the research findings, the article includes a brief review of literature on the implementation and use of solar photovoltaic technology in developing countries, with an emphasis on solar mini-grid systems.

Batch studies were conducted to investigate the kinetics and isotherms of Cu(II) biosorption on the biomass of green alga Spirogyra species. It is observed that the biosorption capacity of the biomass strongly depends on pH and algal dose. The maximum biosorption capacity of 133.3 mg Cu(II)/g of dry weight of biomass was observed at an optimum pH of 5 in 120 min with an algal dose of 20 g/L. Desorption studies were conducted with 133.3 mg/g of Cu(II) loaded biomass using different desorption agents including HCl, EDTA, H2SO4, NaCl, and H2O. The maximum desorption of 95.3% was obtained with HCl in 15 min. The results indicate that with the advantages of high metal biosorption capacity and satisfactory recovery of Cu(II), Spirogyra can be used as an efficient and economic biosorbent material for the removal and recovery of toxic heavy metals from polluted water.

Abstract Bio fuels are still a major source for cooking by many households in developing countries such as India causing significant disease burden due to indoor air pollution. While household income influences the choice of fuel the policies that affect accessibility and price of fuels also have an important role in determining the fuel choice. This study analyzes the pollution–income relationship for the period 1983–2000, separately across rural and urban households in India based on unit record data on fuel consumption obtained through National Sample Surveys. While a non-monotonic relationship is observed in rural India in both the decades, in urban India a similar relationship is observed only for the initial period indicating faster transition towards ‘cleaner’ fuels mainly enabled by policies that have been pro-urban. The study also finds that the impact of household size and composition on bio fuels is more negative than for clean fuels and is increasingly negative over time possibly due to greater awareness about the ill effects of such fuels.

Driven by the search for the highest theoretical efficiency, in the latest years several studies investigated the integration of high temperature fuel cells in natural gas fired power plants, where fuel cells are integrated with simple or modified Brayton cycles and/or with additional bottoming cycles, and CO2 can be separated via chemical or physical separation, oxy-combustion and cryogenic methods. Focusing on Solid Oxide Fuel Cells (SOFC) and following a comprehensive review and analysis of possible plant configurations, this work investigates their theoretical potential efficiency and proposes two ultra-high efficiency plant configurations based on advanced intermediate-temperature SOFCs integrated with a steam turbine or gas turbine cycle. The SOFC works at atmospheric or pressurized conditions and the resulting power plant exceeds 78% LHV efficiency without CO2 capture (as discussed in part A of the work) and 70% LHV efficiency with substantial CO2 capture (part B). The power plants are simulated at the 100 MW scale with a complete set of realistic assumptions about fuel cell (FC) performance, plant components and auxiliaries, presenting detailed energy and material balances together with a second law analysis.

Abstract Uncertainty introduces significant complexity to the design process of distributed energy systems (DES) and introduces the risk of suboptimal decisions when the design is performed deterministically. Therefore, it is important that computational DES design models are able to account for the most relevant uncertainty sources when identifying optimal DES configurations. In this paper, a model for optimal DES design under uncertainty is presented and is formulated as a Two-stage Stochastic Mixed-Integer Linear Program. As uncertain parameters, energy carrier prices and emission factors, building heating and electricity demands, and incoming solar radiation patterns are considered and probabilistic scenarios are used to describe their uncertainty. The model seeks to make cost-optimal DES design decisions (technology selection and sizing) before these uncertain parameters are known, while it also identifies the optimal operation of the selected DES configuration for multiple uncertain scenarios. Moreover, two strategies for emission reduction are employed that set CO2 limits either to the system’s average emissions under uncertainty (‘neutral’ strategy) or individually to the system’s emissions for every possible uncertainty outcome to ensure a more robust emission performance (‘aggressive’ strategy). To illustrate the model’s application, the design of a DES for a Swiss urban neighbourhood of 10 buildings is investigated. Multiple optimal DES configurations are obtained by using the ‘neutral’ and ‘aggressive’ emission reduction strategies and the trade-offs between the systems’ economic and emission performance are analysed. Moreover, the optimal DES are contrasted in terms of technology selection and energy consumption shares among fossil fuels, grid electricity and renewable energy. Finally, all model outputs are compared to results obtained from a deterministic design model. The comparison showed that the deterministic model leads to underestimations of the system costs and inaccurate estimates of the system’s CO2 emissions. Moreover, the deterministic designs, in many cases, underestimate the renewable energy capacity that is required to meet the imposed CO2 limits. These significant differences between the stochastic and the deterministic model results can serve to confirm the shortfalls of deterministic design.