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[en] Highlights: • Three novel schemes about integrating solar energy into the boiler are proposed. • Solar-coal hybrid system under fuel saving mode and power boosting mode are studied. • Sankey diagram is used to analyze the exergy destruction of key components. - Abstract: A Solar Tower Aided Coal-fired Power (STACP) system utilizes a solar tower coupled to a conventional coal-fired power system to reduce pollutants, greenhouse gas emissions and the investment of solar energy facilities. This paper examines three different schemes for integrating solar energy into a conventional boiler. For each scheme, an energy and exergy analysis of a 600 MWe supercritical coal-fired power system is combined with 53 MWth of solar energy in both a fuel saving mode and a power boosting mode. The results show that, for all these integration schemes, the boiler’s efficiency and system’s efficiency are reduced. However, the standard coal consumption rate is lower in comparison to conventional power plants and the standard coal consumption rate in the fuel saving mode is lower than that in the power boosting mode for all three schemes. Comprehensively considering both the standard coal consumption rate and efficiency, the scheme that uses solar energy to heat superheat steam and subcooled feed-water is the best integration option. Compared with a coal-fired only system, the saved standard coal consumption rate of the above mentioned scheme in fuel saving mode and power boosting mode can reach up to 11.15 g/kWh and 11.11 g/kWh, respectively. Exergy analysis shows, for STACP system, exergy losses of boiler and solar field contribute over 88% of whole system’s exergy loss.
[en] Highlights: • Novel optimization method for off-grid renewable installations is presented. • Results are compared with an installed PV-battery system. • At least 9.7% reduction in the lifetime cost of the system is achieved. • Sensitivity analysis is performed to consider Li-ion battery price uncertainties. - Abstract: This paper proposes a new methodology to find the most economic system configuration and energy management strategy for Li-ion battery based off-grid renewable energy systems. A system level macroscopic model and a microscopic battery lifetime prediction model are incorporated into the optimization framework to simulate hourly performance of the system. Due to the computational efficiency of the model, optimization is carried out using enumerative method (evaluating all the possible combinations of components and control strategies) to ensure finding the global optimum solution of the problem. To investigate the effectiveness of the proposed methodology, the optimization results are compared with a baseline scenario which is an installed PV-battery system to provide electricity for an isolated house situated near Zaragoza, Spain. Results indicate that the optimized scenario leads to 9.7% reduction in the levelized cost of energy and 48.6% improvement in the battery service period in comparison with the baseline scenario. Moreover, by considering a 0.5% unmet load, the economic feasibility of the system and the battery longevity are enhanced to 14.6% and 78.4%, respectively. Finally, to evaluate the effect of battery unit price and future trends on the optimization results, sensitivity analysis is performed.
[en] Highlights: • A data-driven system approach was developed for visualization analysis. • A transport biofuel technological paradigm (TBTP) is proposed. • Further electric energy trends were discovered through a DAS trend analysis. • Indirect e-bio fuel cell and direct bioelectricity assist in electric energy conversion. • The paradigm shift exits the biofuel paradigm to a bio-electric energy paradigm. - Abstract: The continuing dependence on fossil fuels and the rising energy use in the transport sector have resulted in increased research into viable transport biofuels to mitigate climate change and improve energy security. As transport biofuels now only have a small share of the transport sector energy supply and the complexity in providing the fuels because of issues related to available land and food security, this paper develops conversion path solutions for transport biofuel development based on a technological paradigm study. A data-driven approaches system (DAS) that combines visualization analyses with technological paradigm theory is proposed to reveal the key areas and trends in transport biofuels. Timeline, timezones, and cluster visualizations identified the transport biofuel technological paradigm (TBTP) from current transport biofuel developments; a pre-shift phase (including TBTP competition and TBTP diffusion) and a shift phase (TBTP shift), which respectively relate to conventional biofuels, advanced biofuels, and biofuel cells. However, from further DAS trend analyses and the practical findings, electric energy trends were revealed, indicating that there was a paradigm shift from the biofuel paradigm to a bio-electric energy paradigm. From the developed bio-electric energy framework, both indirect and direct methods were found to have led to an this electric energy conversion to an e-bio fuel cell vehicle for fuel cell electric vehicles (FCEV) and bioelectricity for electric vehicles (EV), both of which can contribute to a low-carbon, sustainable transportation future.
[en] Highlights: • A novel cogeneration heating system with full waste heat recovery is proposed. • Optimization direction of integration is revealed for waste heat recovery system. • Thermodynamic perfection, energy consumption and economy are analyzed intensively. • Total exergy efficiency of the novel system increases by 6.1–14.1% • Both the heating energy consumption and the unit heating cost are evidently reduced. - Abstract: In order to utilize the condensed waste heat of multi turbine units of cogeneration plant efficiently and simultaneously, a novel cogeneration heating system is proposed. Comparative analyses are made among the conventional cogeneration heating system, the absorption heat pump cogeneration heating system, the high backpressure cogeneration heating system and the novel cogeneration heating system from the aspects of thermodynamics, energy consumption and economy. The research objects are 2 × 300 MW water-cooling turbine units. The aim of the work is to point out the optimization direction of system integration for the novel cogeneration heating system by the thermodynamic analysis, and to reveal the actual heating energy consumption and the unit heating cost of the systems based on the method of equivalent electricity of heating. The study results show that the novel cogeneration heating system reasonably matches the extraction steam, the exhaust steam and the heating network water with each other at different energy levels. Therefore, it has evident advantages in the aspects of the thermodynamic perfection, the actual heating energy consumption and the economy. Compared with other systems, the novel cogeneration heating system increases the total exergy efficiency by 6.1–14.1%, reduces the equivalent electricity of heating by 11.1–29.4% and reduces the unit heating cost by 8.7–23.9%.
[en] Highlights: • The built environment is facing an energy challenge due to an aging population. • Benefits of poly-generation for houses inhabited by elderly people were analysed. • Results show 26% reduction in CO2 emissions and 80% savings in the energy bill. • Potential 8% reduction in CO2 emissions of the national residential sector by 2037. - Abstract: The increasing number of elderly people (over 65 years of age), long-term home care policies and the generally higher energy demand of houses inhabited by elderly people will pose an energy challenge for the built environment. The paper analyses the benefits of poly-generation technologies, focusing on the case of hard to heat homes in Northern Ireland. The energy consumption of a test house that is representative of 28% of Northern Ireland housing stock and of a house with elderly inhabitants has been monitored without any intervention. An optimization procedure has been developed to identify the optimal mix of poly-generation technologies. The technologies considered are micro-combined heat and power, heat pump and photovoltaic systems with possible integration of thermal energy storage systems. Six scenarios based on different energy tariffs and technology incentives have been presented. In the best case scenario, the combination of photovoltaic, heat pump and thermal energy storage provides 26% reduction in carbon dioxide emissions and 80% savings in the energy bill compared to standard energy generation. The investment required would be in the order of £11,000. In Northern Ireland, 307,000 households (79.1% more than in 2012) will have elderly inhabitants by 2037. The adoption of poly-generation technologies in the older housing stock could lead to 8% reduction of carbon dioxide emissions of the entire residential sector, with 150 GWh increase in the electricity generation from renewable energy without affecting the electricity distribution network.
[en] Highlights: • The SOFC-PEMFC hybrid system coupled with TSA technology is proposed and modeled. • The novel hybrid system presents a higher efficiency than the single FC systems. • WGS reaction heat can be recycled for driving TSA reaction to improve efficiency. • Using TSA instead of PSA improves efficiency without increasing exergy destruction. - Abstract: A novel hybrid system fueled with natural gas (NG), consisting of solid oxide fuel cell (SOFC), proton exchange membrane fuel cell (PEMFC) and gas processing (GP) subsystem for H2 production and purification, is proposed and modeled in this paper. The combination of water gas shift (WGS) and thermal swing adsorption (TSA) methods is adopted to convert the syngas from the SOFC into H2 with high purity for subsequent use as a fuel in PEMFC for additional power generation. The parametric and exergy analyses show that the proposed hybrid system can achieve high energy conversion efficiency of approximately 64% and exergy efficiency of 61%, which are higher than some other fuel cell systems, such as reformer-PEMFC, standalone SOFC, SOFC-engine/gas turbine and SOFC-chemical looping hydrogen production. The waste heat recovery for driving the TSA reaction and the H2 recirculation for the PEMFC are found to improve the net electricity efficiency by 3.24% and 6.33%, respectively. In addition, using TSA method instead of the traditional pressure swing adsorption (PSA) could improve the efficiency of the SOFC-PEMFC hybrid system without increasing the exergy destruction. These results reveal that the novel hybrid system is a promising energy conversion system with high efficiency.
[en] Highlights: • The mathematical model of combined heat and power plant operation is developed. • Energy flows in various modes of CHP operation are compared. • Effect of the increased CO2 emission price on CHP probability is studied. • Economic analysis of CHP operation in different modes is performed. - Abstract: This paper presents mathematical modeling and economic analysis of a medium size combined heat and power (CHP) operation, installed in Poland. The plant is equipped with steam boilers, extraction condensing turbine, and the grade type water boilers. The paper determines the most efficient mode of CHP operations. The economic efficiency analysis is performed for transient seasons, characterized by low demands for heating, which obliged production units to operate out of its nominal conditions at a lower efficiency. The developed method is also suitable for analyzing complex power plants, with a few energy equipments. The developed mathematical model for simulating CHP performance gives the possibility to select the boiler type, and assess the probability and efficiency of each configuration. The dedicated tool calculates the selected operation mode, heating power demand, and enables models comparison. The algorithm includes real equipment operational parameters, technical limitations, actual energy prices and costs regarding energy law acts. The performed analysis is up-to-date, due to a few aspects: permanently increased fossil fuels costs, low electric energy prices, growing costs of CO2 emission allowances, and high electricity production cost on turbine’s condensing section at steam parameters of T = 435 °C and p = 34 bar. A detailed cost analysis is performed on each product separately: thermal energy, electric energy from cogeneration and electric energy from condensation, during every hour, frequently. The calculation is carried every an hour for a period of 24 h, the energy balance is ensured during the calculation. The most important result of this study is a comparison of CHP to water boiler operation profitability, also including the net profit comparison. Furthermore, the cost of the CO2 emission is studied, for the production profitability in two scenarios, as the price increases from 7 EUR/tone to 15 EUR/tone and 30 EUR/tone.
[en] Highlights: • A novel EfW process is proposed based on intermediate pyrolysis and CHP technology. • A 500 t/h plant has an electrical output of 4.4 MW and a thermal output of 5.3 MW. • The capital cost is £6.23 m/MWelec and the levelised electricity cost is £0.063/kWh. • The plant availability and production rate are the most influential factors to LCOE. • The government’s waste management and energy policies are critical to project viability. - Abstract: The increasing environmental concerns and the significant growth of the waste to energy market calls for innovative and flexible technology that can effectively process and convert municipal solid waste into fuels and power at high efficiencies. To ensure the technical and economic feasibility of new technology, a sound understanding of the characteristics of the integrated energy system is essential. In this work, a comprehensive techno-economic analysis of a waste to power and heat plant based on integrated intermediate pyrolysis and CHP (Pyro-CHP) system was performed. The overall plant CHP efficiency was found to be nearly 60% defined as heat and power output compared to feedstock fuel input. By using an established economic evaluation model, the capital investment of a 5 tonne per hour plant was calculated to be £27.64 million and the Levelised Cost of Electricity was £0.063/kWh. This agrees the range of cost given by the UK government. To maximise project viability, technology developers should endeavour to seek ways to reduce the energy production cost. Particular attention should be given to the factors with the greatest influence on the profitability, such as feedstock cost (or gate fee for waste), maintaining plant availability, improving energy productivity and reducing capital cost.
[en] Highlights: • Wind energy integrated with natural-gas-to-methanol process is proposed. • Performances of NGTM and WGTM are compared. • WGTM can cut down the greenhouse gas emission and raw material consumption. - Abstract: Methanol is an important platform chemical. The conversion of natural gas is the most widely used technology to produce methanol. With the development of chemical industry, the situation of energy shortage has become very serious. The exploration and adoption of renewable energy is an alternative way to solve the crisis of energy shortage. Wind energy is one of the most prominent energy source among all renewable energy sources in the Chinese energy markets. In this paper, wind energy integrated with natural-gas-to-methanol (WGTM) process is proposed. Performance analysis including carbon efficiency, energy efficiency, production cost, carbon reduction benefit, and impact of carbon tax is conducted. Based on the comparison results of NGTM (natural-gas-to-methanol) and WGTM (wind energy integrated with natural-gas-to-methanol), it can be concluded that the proposed system may be ready for industrialization at the near future. The wind energy integration provides a promising way to reduce carbon dioxide emission. The WGTM can be a flexible way to slow down the GHG effect.
[en] Highlights: • The LCOE is estimated for solar PV with batteries and bio-crude combustion. • The LCOE of solar PV and batteries was calculated to be 170 AUD/MWh. • The LCOE of solar PV and bio-crude combustion was calculated to be 116 AUD/MWh. • Combining solar PV with bio-crude combustion yields low cost renewable electricity. - Abstract: The strong growth of intermittent electricity generation from solar PV and wind is leading to a greater need for energy storage at grid scale. In this work a techno-economic model has been constructed to calculate the levelised cost of electricity for two systems that can meet an arbitrary energy demand curve: (1) solar PV and battery storage and (2) solar PV with combustion of bio-crude and bio-gas from biomass. The analysis is performed for conditions prevalent in Queensland, Australia where over a gigawatt of new solar PV capacity is being constructed in 2018. The battery storage assumes lithium-ion batteries and costs derived from the recently constructed Hornsdale Power Reserve in South Australia. A variable energy demand curve is assumed in the work. The model shows that the parameters with the most impact on the LCOE for the solar PV and battery system are the solar yield, and total installed costs of the battery and solar PV unit. Assuming, battery costs of 750 AUD/kWh, solar PV costs of 1.6 AUD/W and a project capacity of 240 MWh/d, the LCOE of the solar PV and battery system was calculated to be 170 AUD/MWh. Using total installed costs forecast for the near future, the LCOE is expected to be in the range 150–185 AUD/W for the variable energy demand curve, and over 200 AUD/MWh if a constant supply of power is required. The parameters with the most impact on the LCOE for the solar PV and bio-crude system are the solar yield and total installed cost of the biomass pyrolysis and bio-crude combustion unit. For a 240 MWh/d project scale with variable energy demand, the LCOE for the solar PV and bio-crude system is estimated to be 116 AUD/MWh. Variations in feedstock cost and project scale showed that the LCOE is in the range of 104–125 AUD/MWh. The main conclusion from this work, is that integration of solar PV and the production and combustion of bio-crude and bio-gas using fast pyrolysis of biomass, leads to competitively priced dispatchable renewable energy that is forecast to be cheaper than using solar PV and batteries for the foreseeable future. It has also been found that the combination of solar PV and bio-crude combustion leads to lower LCOEs than using bioenergy alone, due to the rapidly decreasing costs of large scale solar PV. While the solar PV and bio-crude system analysed in this work will likely be a niche solution, in areas with substantial biomass resources, it offers a credible starting point for the development of larger scale bioenergy value chains, with the longer term goal of converting lignocellulosic biomass materials into renewable transportation fuels and chemicals.