Energy analysis of a CO2 recycling system

In this report, a CO₂ recycling system is proposed and designed for the purpose of CO₂ mitigation through utilization of natural energy (photovoltaic power generation). The materials for construction and unit requirements of this system are quantified and also an energy analysis is performed as one of life‐cycle analysis (LCA) of this system. Concrete required for the foundation of the facilities is the largest material requirement and accounts for 62 per cent of the total amount of materials for building this system. The energy consumption needed to build the photovoltaic (PV) power generation facilities represents the largest fraction of energy consumption and accounts for 82 per cent of the energy consumption needed for building of plants. The energy balance ratio of the system is approximately 1.85. It clearly reveals that this system would be an effective way to utilize natural energy. Copyright © 2000 John Wiley & Sons, Ltd.     

Performance investigation of a hybrid PV‐diesel power system for remote areas

Algeria is in a region with an enormous potential of solar energy for power generation. However, photovoltaic (PV) power plants have not yet been developed sufficiently in the country, and its applications such as PV pumping, solar distillation, and solar heating. The main problem is the high maintenance, operating costs, fossil‐fuel transportation, and CO₂ emission of Bordj Badji Mokhtar's (BBM's) diesel power plant that exhibits a noteworthy issue in south Algeria. This paper presents the results of a theoretical and experimental study for PV/diesel hybrid energy system (HES) considering the load demand profile and the solar radiation in isolated area of south Algeria. Suggested hybridization based on a renewable energy with a view to an improved environment is promising. Study results show the performance of PV/diesel system based on solar radiation. The experiment load curve in this typical area may conduct the diesel generator to operate at 60% to 70% of its nominal power with less fuel consumption, and it has been verified during this study that the implementation of a PV/diesel hybrid system is efficient for higher load and higher solar radiation. Results and discussions are encouraging considering less emission of greenhouse gases and less storage of fuel, which drives the government to draw a political arrangement for the improvement of cleaner forms of electricity generation.     

A preliminary study on potential for very large-scale photovoltaic power generation (VLS-PV) system in the Gobi desert from economic and environmental viewpoints

A 100 MW very large-scale photovoltaic power generation (VLS-PV) system is designed assuming that it will be installed in the Gobi desert, which is one of the major deserts in the world. Array arrangement, array support, foundation, wiring, and so on are designed in detail. Then energy payback time (EPT), life-cycle CO₂ emission rate and generation cost of the system are estimated based on the methodology of life-cycle analysis. As a result of the estimation, 1.7 year of EPT and 12 g C/kWh of CO₂ emission rate are obtained. These show that VLS-PV in the Gobi desert would be very promising for the global energy and environmental issues. The generation cost is calculated at 8.6 cent/kWh assuming that PV module price is one US $/W and system lifetime is 30 years.     

Examining the feasibility of nuclear-renewable hybrid energy system in Korea: A case-based analysis of high penetrations of solar energy

In 2017, as part of an effort to reduce CO₂ emissions, Korea declared its plan to increase the contribution of renewables from 9% to 33% of its total installed capacity by 2030. To this end, it is crucial to harmonize the existing low CO₂ baseload generators (ie, nuclear power plants) with more variable and uncertain generation sources such as photovoltaic (PV) plants. In this study, we propose a nuclear and renewable hybrid energy system (NHES) configuration that combines the nuclear power fleet, PV plants, and industrial demand response (DR) resources, to address technical and economic issues arising from high penetrations of PV capacity. Employing a day-ahead scheduling method, the effectiveness of harnessing industrial DR as energy storage for Korea's nuclear fleet was evaluated with an emphasis on grid flexibility, operation costs, and CO₂ emissions. The findings of this study show how the NHES could broaden Korea's affordable low-carbon paths and technical options, which are promising for short-term applications.     

An evaluation on the life cycle of photovoltaic energy system considering production energy of off-grade silicon

In this study, single-crystalline silicon (c-Si) photovoltaic (PV) cells and residential PV systems using off-grade silicon supplied from semiconductor industries were evaluated from a life cycle point of view. Energy payback time (EPT) of the residential PV system with the c-Si PV cells made of the off-grade silicon was estimated at 15.5 years and indirect CO₂ emission per unit electrical output was calculated at 91 g-C/kWh even in the worst case. These figures were more than those of the polycrystalline-Si and the amorphous-Si PV cells to be used in the near future, but the EPT was shorter than its lifetime and the indirect CO₂ emissions were less than the recent average CO₂ emissions per kWh from the utilities in Japan. The recycling of the c-Si PV cells should be discussed for the reason of the effective use of energy and silicon material.     

Characteristic evaluation of a CO2‐capturing repowering system based on oxy‐fuel combustion and exergetic flow analyses for improving efficiency

A CO₂‐capturing H₂O turbine power generation system based on oxy‐fuel combustion method is proposed to decrease CO₂ emission from an existing thermal power generation system (TPGS) by utilizing steam produced in the TPGS. A high efficient combined cycle power generation system (CCPS) with reheat cycle is adopted as an example of existing TPGSs into which the proposed system is retrofitted. First, power generation characteristics of the proposed CO₂‐capturing system, which requires no modification of the CCPS itself, are estimated. It is shown through simulation study that the proposed system can reduce 26.8% of CO₂ emission with an efficiency decrease by 1.20% and an increase power output by 23.2%, compared with the original CCPS. Second, in order to improve power generation characteristics and CO₂ reduction effect of the proposed system, modifications of the proposed system are investigated based on exergetic flow analyses, and revised systems are proposed based on the obtained results. Finally, it is shown that a revised proposed system, which has the same turbine inlet temperature as the CCPS, can increase power output by 33.6%, and reduce 32.5% of CO₂ emission with exergetic efficiency decrease by 1.58%, compared with the original CCPS. Copyright © 2010 John Wiley & Sons, Ltd.     

Power sector development in India with CO2 emission targets: Effects of regional grid integration and the role of clean technologies

The power sector in India at present comprises of five separate regional electricity grids having practically no integrated operation in between them. This study analyses the utility planning, environmental and economical effects of integrated power sector development at the national level in which the regional electric grids are developed and operated as one integrated system. It also examines the effects of selected CO₂ emission reduction targets in the power sector and the role of renewable power generation technologies in India. The study shows that the integrated development and operation of the power system at the national level would reduce the total cost including fuel cost by 4912 million $, total capacity addition by 2784 MW, while the emission of CO₂, SO₂ and NO_x would be reduced by 231.6 (1.9%), 0.8 (0.9%), 0.4 (1.2%) million tons, respectively, during the planning horizon. Furthermore, the study shows that the expected unserved energy, one of the indices of generation system reliability, would decrease to 26 GWh under integrated national power system from 5158 GWh. As different levels of CO₂ emission reduction targets were imposed, there is a switching of generation from conventional coal plants to gas fired plants, clean coal technologies and nuclear based plants. As a result the capacity expansion cost has increased. It was found that wind power plant is most attractive and economical in the Indian perspective among the renewable options considered (Solar, wind and biomass). Copyright © 2003 John Wiley & Sons, Ltd.     

Study on a zero CO2 emission SOFC hybrid power system integrated with OTM using CO2 as sweep gas

A new zero CO₂ emission solid oxide fuel cell (SOFC) hybrid power system integrated with the oxygen ion transport membrane using CO₂ as sweep gas is proposed in this paper. The pure oxygen is picked up from the cathode outlet gas by the oxygen ion transport membrane with CO₂ as sweep gas; the oxy‐fuel combustion mode in the afterburner of SOFC is employed. Because the combustion product gas only consists of CO₂ and steam, CO₂ is easily captured with lower energy consumption by the condensation of steam. With the aspen plus soft, this paper builds the simulation model of the overall SOFC hybrids system with CO₂ capture. The exergy loss distributions of the overall system are analyzed, and the effects of the key operation parameters on the overall system performance are also investigated. The research results show that the new system still has a high efficiency after CO₂ recovery. The efficiency of the new system is around 65.03%, only 1.25 percentage points lower than that of the traditional SOFC hybrid power system(66.28%)without CO₂ capture. The research achievements from this paper will provide the valuable reference for further study on zero CO₂ emission SOFC hybrid power system with higher efficiency. Copyright © 2013 John Wiley & Sons, Ltd.     

Emissions reduction data for grid-connected photovoltaic power systems

This study measured the pollutant emission reduction potential of 29 photovoltaic (PV) systems installed on residential and commercial building rooftops across the US from 1993 through 1997. The US Environmental Protection Agency (EPA) and 21 electric power companies sponsored the project. This article presents results of analyses of each PV system’s ability to offset electric utility power plant emissions of sulfur dioxide (SO₂), nitrogen oxides (NO_x), and carbon dioxide (CO₂). Each PV system’s performance was monitored and compared with hour-by-hour operating characteristics of the participating electric utilities in order to determine pollution offsets. The monthly mean and standard deviation offset are given for each pollutant, along with the coefficient of variation.     

Study on zero CO2 emission atmospheric pressure SOFC hybrid power system integrated with OTM

In order to further reduce the energy consumption of CO₂ capture from the traditional SOFC hybrid power system, based on the principle of energy cascade utilization and system integration, a zero CO₂ emission atmospheric pressure solid oxide fuel cell (SOFC) hybrid power system integrated with oxygen ion transport membrane (OTM) is proposed. The oxygen is produced by the OTM for the oxy‐fuel combustion afterburner of SOFC. With the Aspen‐plus software, the models of the overall SOFC hybrid power systems with or without CO₂ capture are developed. The thermal performance of new system is investigated and compared with other systems. The effects of the fuel utilization factor of SOFC and the pressure ratio between two sides of OTM membrane on the overall system performance are analyzed and optimized. The research results show that the efficiency of the zero CO₂ emission atmospheric pressure SOFC hybrid power system integrated with OTM is around 58.36%, only 2.48% lower than that of the system without CO₂ capture (60.84%) but 0.96% higher than that of the zero CO₂ emission atmospheric pressure SOFC hybrid system integrated with the cryogenic air separation unit. Copyright © 2014 John Wiley & Sons, Ltd.     

Considerations for the calculation of greenhouse gas reduction by photovoltaic solar energy

A CO₂ comprehensive balance within the life-cycle of a photovoltaic energy system requires careful examination of the CO₂ sinks and sources at the locations and under the conditions of production of each component, during transport, installation and operation, as well as at the site of recycling. Calculations of the possible effect on CO₂ reduction by PV energy systems may be incorrect if system borders are not set wide enough and remain on a national level, as can be found in the literature. For the examples of Brazil and Germany, the effective CO₂ reductions have been derived, also considering possible interchange scenarios for production and operation of the PV systems considering the carbon dioxide intensity of the local electricity grids. In the case of Brazil also off-grid applications and the substitution of diesel generating sets by photovoltaics are examined: CO₂ reduction may reach 26,805 kg/kW_p in that case. Doing these calculations, the compositions of the local grids and their CO₂ intensity at the time of PV grid injection have to be taken into account. Also possible changes of the generation fuel mix in the future have to be considered: During the operation time of a PV system, different kinds of power plants could be installed that might change the CO₂ intensity of the grid. In the future also advanced technologies such as thin films have to be considered.     

A comparative analysis of energy and CO2 taxes on the primary energy mix for electricity generation

In many countries, economies are moving towards internalization of external costs of greenhouse‐gas (GHG) emissions. This can best be achieved by either imposing additional taxes or by using an emission‐permit‐trading scheme. The electricity sector is under scrutiny in the allocation of emission‐reduction objectives, not only because it is a large homogeneous target, but also because of the obvious emission‐reduction potential by decreasing power generation based on carbon‐intensive fuels. In this paper, we discuss the impact of a primary‐energy tax and a CO₂ tax on the dispatching strategy in power generation. In a case study for the Belgian power‐generating context, several tax levels are investigated and the impact on the optimal dispatch is simulated. The impact of the taxes on the power demand or on the investment strategies is not considered. As a conclusion, we find that a CO₂ tax is more effective than a primary‐energy tax. Both taxes accomplish an increased generation efficiency in the form of a promotion of combined‐cycle gas‐fired units over coal‐fired units. The CO₂ tax adds an incentive for fuel switching which can be achieved by altering the merit order of power plants or by switching to a fuel with a lower carbon content within a plant. For the CO₂ tax, 13 €/tonCO₂ is withheld as the optimal value which results in an emission reduction of 13% of the electricity‐related GHG emissions in the Belgian power context of 2000. A tax higher than 13 €/tonCO₂ does not contribute to the further reduction of GHGs. Copyright © 2005 John Wiley & Sons, Ltd.     

Optimal operation of a photovoltaic generation-powered hydrogen production system at a hydrogen refueling station

As the popularity of fuel cell vehicles continues to rise in the global market, production and supply of low-carbon hydrogen are important to mitigate CO₂ emissions. We propose a design for a hydrogen refueling station with a proton exchange membrane electrolyzer (PEM-EL)-based electrolysis system (EL-System) and photovoltaic generation (PV) to supply low-carbon hydrogen. Hydrogen is produced by the EL-System using electricity from PV and the power grid. The system was formulated as a mixed integer linear programming (MILP) model to allow analysis of optimal operational strategies. Case studies with different objective functions, CO₂ emission targets, and capacity utilization of the EL-System were evaluated. Efficiency characteristics of the EL-System were obtained through measurements. The optimized operational strategies were evaluated with reference to three evaluation indices: CO₂ emissions, capacity utilization, and operational cost of the system. The results were as follows: 1) Regardless of the objective function, the EL-System generally operated in highest efficiency state, and optimal operation depended on the efficiency characteristics of the EL-System; 2) mitigation of CO₂ emissions and increase in capacity utilization of the EL-System required trade-offs; and 3) increased capacity utilization of the EL-System showed two opposing effects on hydrogen retail price.     

Examining the driving forces for improving China’s CO2 emission intensity using the decomposing method

This paper examines the driving forces for reducing China’s CO₂ emission intensity between 1998 and 2008, utilizing the logarithmic mean divisia index (LMDI) technique. By first grouping the CO₂ emissions into two categories, those arising from activities related to the electric power industry and those from other sources, emission intensity is further broken down into the effects of the CO₂ emission coefficient, energy intensity of power generation, power generation and consumption ratio, electricity intensity of the gross domestic product (GDP), provincial structural change, and the energy intensity of the GDP for other activities. The decomposition results show that improvements in the energy intensity of power generation, electricity intensity of GDP, and energy intensity of GDP for other activities were mainly responsible for the success in reducing China’s CO₂ emission intensity and that activities related to the electric power industry played a key role. It is also revealed that performance varied significantly at the individual province level. The provinces with higher emission levels contributed the most to China’s improvements in CO₂ emission intensity.     

Trade-off between environmental and economic implications of PV systems integrated into the UAE residential sector

PV technology offers clean resource and environmental advantages over fossil-fuel-based electricity generation; however, it remains more expensive than conventional technology in most grid-connected applications. The trade-off between environmental and economic parameters represents a challenge for governments. The objectives of this study are: firstly, to review studies in relation to the use of PV systems in the Gulf region and secondly, to assess the trade-off between environmental and economic parameters that influence the value of building integrated photovoltaic (BiPV) technology applied into the UAE building sector. This work examines residential buildings and concludes that the economic viability of BiPV systems is subject to capital cost, system efficiency and electricity tariff. To be a cost-effective option in the UAE, subsidies for PV investments and reasonable electricity tariff must be implemented. It is suggested that BiPV systems offer cost reductions in both energy and economic terms over centralised PV plants, especially if the costs of saved operating energy and avoided building materials are taken into account. Each square meter of BiPV is capable of making a significant reduction in CO₂ emissions generated by conventional power plants. This will limit the impact of global warming on the UAE and others.     

Demonstration of the environmental and demand-side management benefits of grid-connected photovoltaic power systems

This study investigated the pollutant emission reduction and demand-side management potential of 16 photovoltaic (PV) systems installed across the US during 1993 and 1994. The US Environmental Protection Agency (EPA) and 11 electric power companies sponsored the project. This article presents results of analyses of each PV system's ability to offset power plant emissions of sulfur dioxide (SO₂), nitrogen oxides (NO_x), carbon dioxide (CO₂) and particulates and to provide power during peak demand hours for the individual host buildings and peak load hours for the utility. The analyses indicate a very broad range in the systems' abilities to offset pollutant emissions, due to variation in the solar resource available and the emission rates of the participating utilities' load following generation plants. Each system's ability to reduce building peak demand was dependent on the correlation of that load to the available solar resource. Most systems operated in excess of 50% of their capacity during building peak load hours in the summer months, but well below that level during winter peak hours. Similarly, many systems operated above 50% of their capacity during utility peak load hours in the summer months, but at a very low level during winter peak hours.     

A multiperiod multiobjective framework for the synthesis of trigeneration systems in tertiary sector buildings

This paper develops a multiperiod multiobjective optimization procedure to determine the optimal configuration and operational strategy of a trigeneration system assisted with solar-based technologies and thermal energy storage. The optimization model, formulated as mixed integer linear programming problem, incorporates dynamic operating conditions through time-dependent local climatic data, energy resources, energy demands, electricity prices, and electricity CO₂ emission factors. The methodology is applied to a case study of a residential building in Spain. First, the single-objective solutions are obtained, highlighting their fundamental differences regarding the installation of cogeneration (included in the optimal total annual cost solution) and solar-based technologies (included in the optimal total annual CO₂ emissions solution). Then, the Pareto curve is generated, and a decision-making approach is proposed to select the preferred trade-off solutions based on the marginal cost of CO₂ emissions saved. Additionally, sensitivity analyses are performed to investigate the influence of key parameters concerning energy resources prices, investment costs, and rooftop area. The analyses of the trade-off solutions verify the enormous potential for CO₂ emissions reduction, which can reach 32.3% with only 1.1% higher costs by displacing cogeneration in favor of the heat pump and the electric grid. Besides, with a modest cost increase of 7.3%, photovoltaic panels are incorporated, promoting an even greater CO₂ emissions reduction of 45.2%.     

Characteristics and economic evaluation of a power plant applying oxy-fuel combustion to increase power output and decrease CO2 emission

This paper evaluates power generation characteristics, economics, and CO₂ reduction effects of a proposed CO₂-capturing repowering system that utilizes low pressure steam (LPS) to increase generated power and to capture generated CO₂ based on the oxy-fuel combustion method. A case study was adopted wherein LPS from a combined cycle power generation system (CCPS) is used. It is estimated that the proposed system can generate 2.03 times greater power compared to a conventional steam turbine power generation system (the reference system) using the same LPS, with an exergy efficiency of 54.2%, taking into account O₂ production power and captured CO₂ liquefaction power. The proposed system is estimated to be economically feasible (the depreciation year is estimated to be 4.78 years; BCR 2.50; and IRR 23.0%), and will economically outperform the reference system if CO₂ emission credit higher than 30 $/(t − CO₂) is applied for the captured CO₂. The effects of retrofitting the proposed system into the CCPS are estimated as follows: the net generated power can be increased by 27.9% and the CO₂ emission amount can be reduced by 21.8% with a 2.41% degradation of the net power generation efficiency, from 56.2% to 53.8%.     

A comprehensive techno‐economic analysis method for power generation systems with CO2 capture

A new comprehensive techno‐economic analysis method for power generation systems with CO₂ capture is proposed in this paper. The correlative relationship between the efficiency penalty, investment increment, and CO₂ avoidance cost is established. Through theoretical derivation, typical system analysis, and variation trends investigation, the mutual influence between technical and economic factors and their impacts on the CO₂ avoidance cost are studied. At the same time, the important role that system integration plays in CO₂ avoidance is investigated based on the analysis of a novel partial gasification CO₂ recovery system. The results reveal that for the power generation systems with CO₂ capture, the efficiency penalty not only affects the costs on fuel, but the incremental investment cost for CO₂ capture (U.S.$ kW⁻¹) as well. Consequently, it will have a decisive impact on the CO₂ avoidance cost. Therefore, the added attention should be paid to improve the technical performance in order to reduce the efficiency penalty in energy system with CO₂ capture and storage. Additionally, the system integration may not only decrease the efficiency penalty, but also simplify the system structure and keep the investment increment at a low level, and thereby it reduces the CO₂ avoidance cost significantly. For example, for the novel partial gasification CO₂ recovery system, owing to system integration, its efficiency can reach 42.2%, with 70% of CO₂ capture, and its investment cost is only 87$ kW⁻¹ higher than that of the reference IGCC system, thereby the CO₂ avoidance cost is only 6.23$ t⁻¹ CO₂. The obtained results provide a comprehensive technical–economical analysis method for energy systems with CO₂ capture useful for reducing the avoidance costs. Copyright © 2009 John Wiley & Sons, Ltd.     

Embodied energy analysis of photovoltaic (PV) system based on macro- and micro-level

In this paper the energy payback time and CO₂ emissions of photovoltaic (PV) system have been analyzed. The embodied energy for production of PV module based on single crystal silicon, as well as for the manufacturing of other system components have been computed at macro- and micro-level assuming irradiation of 800–1200 W/m² in different climatic zones in India for inclined surface. The energy payback time with and without balance-of-system for open field and rooftop has been evaluated. It is found that the embodied energy at micro-level is significantly higher than embodied energy at macro-level. The effect of insolation, overall efficiency, lifetime of PV system on energy pay back time and CO₂ emissions have been studied with and without balance of system. A 1.2 kW_p PV system of SIEMENS for mudhouse at IIT, Delhi based on macro- and micro-level has been evaluated. The CO₂ mitigation potential, the importance and role of PV system for sustainable development are also highlighted.