• Energy Research

Abstract This paper describes the thermochemical transformation of residual whole olive stones from the industrial production of pitted and stuffed table olives by using a rotary reactor. This experimental investigation describes the chemical, physical and fuel properties of the resulting solids and liquids obtained in the temperature range between 200 °C and 900 °C. Optimum torrefaction conditions, intended to maximize mass and energy yields, were obtained at 278 °C and resulted in a solid product with 68 wt% volatile matter, 29 wt% fixed carbon, 58 wt% elemental carbon, 0.55 O/C ratio, 23.4 MJ/kg of HHV, 11.25 GJ/m 3 apparent energy density for an energy yield of 89%. The carbonized solids obtained at temperatures between 500 °C and 900 °C exhibited LHV and apparent energy density up to 57–66% higher than the original biomass. The carbonization process generates a condensable liquid that represents 50–53 wt% of the original biomass and contains between 57 and 61 wt% water and 39–43 wt% organic products. The carbon content (up to 25 wt%) and heating value (HHV and LHV up to 5.2 MJ/kg and 2.8 MJ/kg, respectively) of this liquid is limited. A model has been tested and a series of equations have been produced which allow us to predict the chemical and energy properties of the solid fraction derived from the torrefaction and carbonization process. This model has found linear correlations between the solid yield and elemental/proximate composition of the solids, and exponential correlations between solid and energy yields.

Abstract This paper describes the thermochemical transformation of residual whole olive stones from the industrial production of pitted and stuffed table olives by using a rotary reactor. This experimental investigation describes the chemical, physical and fuel properties of the resulting solids and liquids obtained in the temperature range between 200 °C and 900 °C. Optimum torrefaction conditions, intended to maximize mass and energy yields, were obtained at 278 °C and resulted in a solid product with 68 wt% volatile matter, 29 wt% fixed carbon, 58 wt% elemental carbon, 0.55 O/C ratio, 23.4 MJ/kg of HHV, 11.25 GJ/m 3 apparent energy density for an energy yield of 89%. The carbonized solids obtained at temperatures between 500 °C and 900 °C exhibited LHV and apparent energy density up to 57–66% higher than the original biomass. The carbonization process generates a condensable liquid that represents 50–53 wt% of the original biomass and contains between 57 and 61 wt% water and 39–43 wt% organic products. The carbon content (up to 25 wt%) and heating value (HHV and LHV up to 5.2 MJ/kg and 2.8 MJ/kg, respectively) of this liquid is limited. A model has been tested and a series of equations have been produced which allow us to predict the chemical and energy properties of the solid fraction derived from the torrefaction and carbonization process. This model has found linear correlations between the solid yield and elemental/proximate composition of the solids, and exponential correlations between solid and energy yields.

SummaryMeasuring the sustainability of goods and services in a systematic and objective manner has become an issue of paramount importance. Life cycle sustainability assessment (LCSA) is a holistic methodology whose aim is to integrate into a compatible format the analysis of the three pillars of sustainability, namely, economy, environment, and society. Social life cycle assessment (S‐LCA) is a novel methodology still under development, used to cover the social aspects of sustainability within LCSA. The aim of this article is to provide additional discussion on the practical application of S‐LCA by suggesting a new classification and characterization model that builds upon previous methodological developments. The structure of the social analysis has been adapted to maintain coherence with that of standard LCA. The application of this methodology is demonstrated using a case study—the analysis of power generation in a concentrated solar power plant in Spain. The inventory phase was completed by using the indicators proposed by the United Nations Environment Program/Society for Environmental Toxicology and Chemistry (UNEP/SETAC) Guidelines on S‐LCA. The impact assessment phase was approached by developing a social performance indicator that builds on performance reference points, an activity variable, and a numeric scale with positive and negative values. The social performance indicator obtained (+0.42 over a range of –2 to +2) shows that the deployment of the solar power plant increases the social welfare of Spain, especially in the impact categories of socioeconomic sustainability and fairness of relationships, whose results were 1.38 and 0.29, respectively.

SummaryMeasuring the sustainability of goods and services in a systematic and objective manner has become an issue of paramount importance. Life cycle sustainability assessment (LCSA) is a holistic methodology whose aim is to integrate into a compatible format the analysis of the three pillars of sustainability, namely, economy, environment, and society. Social life cycle assessment (S‐LCA) is a novel methodology still under development, used to cover the social aspects of sustainability within LCSA. The aim of this article is to provide additional discussion on the practical application of S‐LCA by suggesting a new classification and characterization model that builds upon previous methodological developments. The structure of the social analysis has been adapted to maintain coherence with that of standard LCA. The application of this methodology is demonstrated using a case study—the analysis of power generation in a concentrated solar power plant in Spain. The inventory phase was completed by using the indicators proposed by the United Nations Environment Program/Society for Environmental Toxicology and Chemistry (UNEP/SETAC) Guidelines on S‐LCA. The impact assessment phase was approached by developing a social performance indicator that builds on performance reference points, an activity variable, and a numeric scale with positive and negative values. The social performance indicator obtained (+0.42 over a range of –2 to +2) shows that the deployment of the solar power plant increases the social welfare of Spain, especially in the impact categories of socioeconomic sustainability and fairness of relationships, whose results were 1.38 and 0.29, respectively.

Abstract The aim of this work is to investigate the use of Full Environmental Life Cycle Costing (FeLCC) methodology to evaluate the economic performance of a 50 MW parabolic trough Concentrated Solar Power (CSP) plant operating in hybrid mode with different natural gas inputs (between 0% and 30%). The analysis is based on a plant located in Southern Spain and includes current financial incentives for the promotion of renewable energies. The analysis also incorporates an estimation of external costs associated with atmospheric emissions on six categories: Human Health, Loss of Biodiversity, Local and Global Damage to Crops, Damage to Materials and Climate Change. In a scenario where the project is funded through equity, the life cycle internal costs of the plant operating with solar energy only represent 82.8 €/MW h, while revenues from electricity sales amount to 85.7 €/MW h, resulting in a net present value of 2.95 €/MW h. Internal costs are attributable primarily to the purchase of materials and equipment incurred mainly during the Extraction and Manufacturing life cycle phase. In this scenario, external costs (calculated using CASES damage costs methodology) represent less than 2.6% of all the internal costs considered. Hybridizing CSP with natural gas allows higher overall power outputs due to extended operating hours. However, this strategy involves higher internal costs, resulting in a significant reduction in the revenues (per unit of power generated) and in the net present value of the project. Thus, the existing regulatory system in Spain makes CSP hybridization with natural gas economically unattractive. In addition, the use of natural gas in CSP installations results in a rapid increase in environmental damage as evidenced by higher external costs. For instance, external unit costs of CSP with 30% natural gas were up to 8.6 times higher than in solar-only operation, due primarily to increased greenhouse gas emissions. When the analysis is extended to consider financing through bank loan under common market conditions, the same project shows economic viability for percentages of natural gas hybridization up to 14%. However, solar-only operation remains as the best option.

Abstract The aim of this work is to investigate the use of Full Environmental Life Cycle Costing (FeLCC) methodology to evaluate the economic performance of a 50 MW parabolic trough Concentrated Solar Power (CSP) plant operating in hybrid mode with different natural gas inputs (between 0% and 30%). The analysis is based on a plant located in Southern Spain and includes current financial incentives for the promotion of renewable energies. The analysis also incorporates an estimation of external costs associated with atmospheric emissions on six categories: Human Health, Loss of Biodiversity, Local and Global Damage to Crops, Damage to Materials and Climate Change. In a scenario where the project is funded through equity, the life cycle internal costs of the plant operating with solar energy only represent 82.8 €/MW h, while revenues from electricity sales amount to 85.7 €/MW h, resulting in a net present value of 2.95 €/MW h. Internal costs are attributable primarily to the purchase of materials and equipment incurred mainly during the Extraction and Manufacturing life cycle phase. In this scenario, external costs (calculated using CASES damage costs methodology) represent less than 2.6% of all the internal costs considered. Hybridizing CSP with natural gas allows higher overall power outputs due to extended operating hours. However, this strategy involves higher internal costs, resulting in a significant reduction in the revenues (per unit of power generated) and in the net present value of the project. Thus, the existing regulatory system in Spain makes CSP hybridization with natural gas economically unattractive. In addition, the use of natural gas in CSP installations results in a rapid increase in environmental damage as evidenced by higher external costs. For instance, external unit costs of CSP with 30% natural gas were up to 8.6 times higher than in solar-only operation, due primarily to increased greenhouse gas emissions. When the analysis is extended to consider financing through bank loan under common market conditions, the same project shows economic viability for percentages of natural gas hybridization up to 14%. However, solar-only operation remains as the best option.

Concentrating Solar Power (CSP) technology is developing in order to achieve higher energy efficiency, reduced economic costs, and improved firmness and dispatchability in the generation of power on demand. To this purpose, a research project titled HYSOL has developed a new power plant, consisting of a combined cycle configuration with a 100 MWe steam turbine and an 80 MWe gas-fed turbine with biomethane. Technological developments must be supported by the identification, quantification, and evaluation of the environmental impacts produced. The aim of this paper is to evaluate the environmental performance of a CSP plant based on HYSOL technology using a Life Cycle Assessment (LCA) methodology while considering different locations. The scenarios investigated include different geographic locations (Spain, Chile, Kingdom of Saudi Arabia, Mexico, and South Africa), an alternative modelling procedure for biomethane, and the use of natural gas as an alternative fuel. Results indicate that the geographic location has a significant influence on the environmental profile of the HYSOL CSP plant. The results obtained for the HYSOL configuration located in different countries presented significant differences (between 35% and 43%, depending on the category), especially in climate change and water stress categories. The differences are mainly attributable to the local availability of solar and water resources and composition of the national electricity mix. In addition, HYSOL technology performs significantly better when hybridizing with biomethane instead of natural gas. This evidence is particularly relevant in the climate change category, where biomethane hybridization emits 27.9–45.9 kg CO2 eq per MWh (depending on the biomethane modelling scenario) and natural gas scenario emits 264 kg CO2 eq/MWh.

Concentrating Solar Power (CSP) technology is developing in order to achieve higher energy efficiency, reduced economic costs, and improved firmness and dispatchability in the generation of power on demand. To this purpose, a research project titled HYSOL has developed a new power plant, consisting of a combined cycle configuration with a 100 MWe steam turbine and an 80 MWe gas-fed turbine with biomethane. Technological developments must be supported by the identification, quantification, and evaluation of the environmental impacts produced. The aim of this paper is to evaluate the environmental performance of a CSP plant based on HYSOL technology using a Life Cycle Assessment (LCA) methodology while considering different locations. The scenarios investigated include different geographic locations (Spain, Chile, Kingdom of Saudi Arabia, Mexico, and South Africa), an alternative modelling procedure for biomethane, and the use of natural gas as an alternative fuel. Results indicate that the geographic location has a significant influence on the environmental profile of the HYSOL CSP plant. The results obtained for the HYSOL configuration located in different countries presented significant differences (between 35% and 43%, depending on the category), especially in climate change and water stress categories. The differences are mainly attributable to the local availability of solar and water resources and composition of the national electricity mix. In addition, HYSOL technology performs significantly better when hybridizing with biomethane instead of natural gas. This evidence is particularly relevant in the climate change category, where biomethane hybridization emits 27.9–45.9 kg CO2 eq per MWh (depending on the biomethane modelling scenario) and natural gas scenario emits 264 kg CO2 eq/MWh.