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In this paper, the problem of optimal sizing of biomass-fired ORC combined heat and power (CHP) unit for existing coal-fired district heating (DH) plant is discussed. The study examines the influence of boundary conditions on the optimal design characteristics of the ORC CHP system within heating plant backfitting project. The optimisation task is solved for given site-specific technical, economic, ecological and legal constraints. The proposed methodology for synthesis of new technological structure takes into account long-term operational experience and results of measurements of a given reference plant. Although the methodology is general, the solution presented in the paper is relevant for Polish DH sector. The analysis considers country specific system of financial incentives for renewable energy projects as well as participation in electricity balancing market and European Trading System (ETS). Thermal energy storage is considered as a solution providing flexibility of CHP system operation. Influence of different electricity, biomass, coal and EUA (European Emission Allowance) prices on optimal size and structure of the cogeneration system is examined. The analysis revealed that economic optima are relatively flat and the range of ORC unit size, for which the value of objective function is close to the optimum is quite wide. Although Net Present Value (NPV) and Internal Rate of Return (IRR) suggest slightly different size of the system, the recommended solutions are the ones with relatively long annual time of operation. The optimum size of ORC for a DH system of approximately 30 MW peak heating output is within the range of electric power of 1–2 MW. It was also found that although market prices and support instruments are nowadays different than at the time of commissioning of the reference plant, the size of the ORC unit is still close to the optimal value. Implementation of thermal energy storage (TES) in the form of hot water storage tank moves the optimal rated electric power of the ORC generator slightly towards higher values. On the other hand, only a small improvement of financial performance is gained by implementation of TES. Considerable improvement of economic performance has been reached after anticipated increase paths for electricity and EUA prices were introduced. In this case however, the recommended optimal size of the ORC CHP remained almost the same as in the case of constant prices. • Optimal sizing of biomass-fired ORC CHP unit for district heating plant is presented. • Alternative methodology based on measurement data from existing reference plant is proposed. • Participation in electricity balancing market and European Trading System (ETS) is considered. • Location of optimum is mostly determined by system technical performance. • Optimally sized ORC CHP unit should cover base heating load of district heating grid. [ABSTRACT FROM AUTHOR]

In order to identify impacts of photovoltaic (PV) power plant on surface radiation, this paper conducted a comparative study on the surface radiation and surface albedo characteristics between the PV site and reference site in the Gobi area in Xinjiang, China in the summer of 2020. The results show that, the upward long-wave radiation at the PV site was significantly lower than that at the reference site in the night, while the two were basically the same during the daytime. The average surface albedo at the PV site (0.14) was 39.1% lower than that at the reference site (0.23). Net radiation was higher at the PV site than that at the reference site throughout the whole day. The average net radiation of the underlying surface at the PV site was 30.7% more than that at the reference site, 75% of which was contributed by lower upward shortwave radiation and 25% was due to nocturnal lower upward longwave radiation at the PV site. • Average surface albedo at photovoltaic power site decreases 39.1%. • Upward long-wave radiation at photovoltaic power site decreases significantly. • Average net radiation at photovoltaic power site increases 30.7%. [ABSTRACT FROM AUTHOR]

Large-scale distributed renewable energy sources as well as emerging controllable loads such as electric vehicles connected to the distribution grids have posed challenges to the efficient management of these distributed energy resources. Promoting energy-sharing of distributed energy resources through economic incentives is a cost-effective and equitable solution to the challenge. This paper proposes a two-stage transactive energy control mechanism by the virtual power plant (VPP) for energy-sharing of multiple prosumers. Firstly, a VPP internal price mechanism based on the supply-demand ratio of prosumers in the energy-sharing alliance is proposed. Then, a two-stage economic optimization model is developed. Trading prices between VPP and prosumers are established in the first stage, and prosumers make operating plans based on those prices in the second stage. Then, considering that prosumers and VPP are independent stakeholders, a decentralized optimization algorithm based on the analytical target cascading method is developed. The upper-level VPP coordinates the energy-sharing alliance and sets the transaction price following the overall supply and demand ratio. Lower-level prosumers independently make decisions and feedback on the trading power of the VPP. Then, iterative calculations provide a distributed and independent solution. Finally, the case study verifies that the proposed energy-sharing model can reduce the operating cost of prosumers by 14.29 %. Moreover, prosumer privacy protection is achieved by the analytical target cascading-based distributed model at a cost of less than 1.5 % accuracy. [ABSTRACT FROM AUTHOR]

The paper undertakes a novel study that aims to analyze the performance characteristics of ten monocrystalline or polycrystalline silicon modules employing different emerging technologies in waters environment. In this work, monitoring data were collected over a duration of one year using a multi-technology empirical platform within a floating photovoltaic power plant. The energy performance of different module technologies was evaluated using multiple performance metrics such as array yield, performance ratio, capacity factor, efficiency and energy density. By considering environmental variables such as irradiance, ambient temperature, and water temperature, the thermal behavior of photovoltaic modules under water surface deployment conditions is revealed. Furthermore, the multiple variable coupling analysis was conducted to determine the correlation between the performance metrics of various technology type modules and meteorological variables in waters environment. The results indicate that the energy performance and reliability of monocrystalline silicon modules using double-glass double-sided P-type PERC technology is superior to other technologies in waters environment, and the performance ratio and capacity factor reach 88.95 % and 15.04 %, respectively. The heterojunction with intrinsic thin-layer (HIT) technology module exhibits better thermal stability and holds an advantage in the deployment of limited water surface areas due to its higher energy density. Moreover, the performance ratio of floating photovoltaic systems shows a weak correlation with irradiance, and is more significantly affected by the negative correlation of ambient temperature than water temperature. [ABSTRACT FROM AUTHOR]

Large-scale distributed renewable energy sources as well as emerging controllable loads such as electric vehicles connected to the distribution grids have posed challenges to the efficient management of these distributed energy resources. Promoting energy-sharing of distributed energy resources through economic incentives is a cost-effective and equitable solution to the challenge. This paper proposes a two-stage transactive energy control mechanism by the virtual power plant (VPP) for energy-sharing of multiple prosumers. Firstly, a VPP internal price mechanism based on the supply-demand ratio of prosumers in the energy-sharing alliance is proposed. Then, a two-stage economic optimization model is developed. Trading prices between VPP and prosumers are established in the first stage, and prosumers make operating plans based on those prices in the second stage. Then, considering that prosumers and VPP are independent stakeholders, a decentralized optimization algorithm based on the analytical target cascading method is developed. The upper-level VPP coordinates the energy-sharing alliance and sets the transaction price following the overall supply and demand ratio. Lower-level prosumers independently make decisions and feedback on the trading power of the VPP. Then, iterative calculations provide a distributed and independent solution. Finally, the case study verifies that the proposed energy-sharing model can reduce the operating cost of prosumers by 14.29 %. Moreover, prosumer privacy protection is achieved by the analytical target cascading-based distributed model at a cost of less than 1.5 % accuracy. [ABSTRACT FROM AUTHOR]

The paper undertakes a novel study that aims to analyze the performance characteristics of ten monocrystalline or polycrystalline silicon modules employing different emerging technologies in waters environment. In this work, monitoring data were collected over a duration of one year using a multi-technology empirical platform within a floating photovoltaic power plant. The energy performance of different module technologies was evaluated using multiple performance metrics such as array yield, performance ratio, capacity factor, efficiency and energy density. By considering environmental variables such as irradiance, ambient temperature, and water temperature, the thermal behavior of photovoltaic modules under water surface deployment conditions is revealed. Furthermore, the multiple variable coupling analysis was conducted to determine the correlation between the performance metrics of various technology type modules and meteorological variables in waters environment. The results indicate that the energy performance and reliability of monocrystalline silicon modules using double-glass double-sided P-type PERC technology is superior to other technologies in waters environment, and the performance ratio and capacity factor reach 88.95 % and 15.04 %, respectively. The heterojunction with intrinsic thin-layer (HIT) technology module exhibits better thermal stability and holds an advantage in the deployment of limited water surface areas due to its higher energy density. Moreover, the performance ratio of floating photovoltaic systems shows a weak correlation with irradiance, and is more significantly affected by the negative correlation of ambient temperature than water temperature. [ABSTRACT FROM AUTHOR]

Wind as a renewable energy source is characterized by rapid growth of installed power in many countries, including Poland, where its share in the electricity production has grown over 25 times in the last decade, now reaching about 10%. Since renewable energy has priority in access to the grid, it forces the dispatchable coal-fired power plants to adjust their load. This causes additional consumption of primary energy due to more frequent shut-downs/start-ups and due to efficiency penalty when operating below nominal parameters. In this paper, actual data on the operation of Polish power plants in several years are analysed. The analysis, together with simulations of performance of the power system without the presence of wind energy, focuses on the influence of wind power plants on the utility ones. The results of simulations are additionally processed using the concept of thermo-ecological cost to compare the "operational" impact of wind farms on the power system with their "investment" environmental burden. A conclusion is that current share of wind energy at the level of 10% is enough to have an adverse effect on the coal power plants, but depending on the structure of the power system it may actually increase its overall efficiency. • Introduction of wind power to the grid disrupts the operation of other power plants. • Average efficiency of individual utility power plants decreases. • The number of start-up/shut-down procedures greatly increases. • Depending on the structure of the system, overall efficiency may actually increase. • Thermo-ecological cost of compensation for wind energy is non-negligible. [ABSTRACT FROM AUTHOR]

This paper investigates the smart integration of a 500 ha microalgae culturing facility with a large scale coal power plant (758.6 MW e ): a fraction of the CO 2 contained in the coal plant flue gases is used for the algal cultivation, a fraction of the low-temperature flue gas heat available is used for the biomass drying, finally the produced biomass is co-fired in the coal plant. The produced algal biomass represents approximately 1% of the boiler heat input. Through the solution of energy and mass balances of each plant component, the overall system performances in terms of net energy ratio (NER) and CO 2 emissions reduction are obtained. The computed NER (1.92) guarantees an energy harvest almost twice the energetic cost needed to produce the microalgal fuel. The total CO 2 emissions are reduced of approximately 0.48%, identifying microalgae cofiring as a solution able to reduce the environmental impact of electricity generation. A simplified economic analysis has allowed an estimate of the algal system investment cost (about 235 k€ ha −1 ) and of the levelized cost of electricity (LCOE) (554.4 € MWh −1 ). A set of sensitivity analyses is finally performed to investigate the influence of the initial hypotheses on the results. [ABSTRACT FROM AUTHOR]

Abstract: Parabolic trough solar-aided coal-fired power generation system has been developed to achieve efficient use of solar energy resources by coupling conventional coal-fired power plant with solar energy. However, there are no appropriate evaluation criteria about the thermal and economic performance of the system presently. This paper proposes the evaluation standard of the solar aided coal-fired power plant, and then based on this standard an optimization of this system is applied by the genetic algorithm model. According to the optimization research of this system, a series of parameters such as the solar collector area; the way of the coupling the power plant; whether storage is needed and the relevant storage capacity are obtained. [Copyright &y& Elsevier]

Abstract: Solar energy is an attractive renewable energy source because the sun's energy is plentiful and carbon-free. However, solar energy is intermittent and not suitable for base load electricity generation without an energy backup system. Concentrated solar power (CSP) is unique among other renewable energy options because it can approach base load generation with molten salt thermal energy storage (TES). This paper describes the development of an engineering economic model that directly compares the performance, cost, and profit of a 110-MW parabolic trough CSP plant operating with a TES system, natural gas-fired backup system, and no backup system. Model results are presented for 0–12 h backup capacities with and without current U.S. subsidies. TES increased the annual capacity factor from around 30% with no backup to up to 55% with 12 h of storage when the solar field area was selected to provide the lowest levelized cost of energy (LCOE). Using TES instead of a natural gas-fired heat transfer fluid heater (NG) increased total plant capital costs but decreased annual operation and maintenance costs. These three effects led to an increase in the LCOE for PT plants with TES and NG backup compared with no backup. LCOE increased with increasing backup capacity for plants with TES and NG backup. For small backup capacities (1–4 h), plants with TES had slightly lower LCOE values than plants with NG backup. For larger backup capacities (5–12 h), plants with TES had slightly higher LCOE values than plants with NG backup. At these costs, current U.S. federal tax incentives were not sufficient to make PT profitable in a market with variable electricity pricing. Current U.S. incentives combined with a fixed electricity price of $200/MWh made PT plants with larger backup capacities more profitable than PT plants with no backup or with smaller backup capacities. In the absence of incentives, a carbon price of $100–$160/tonne CO2eq would be required for these PT plants to compete with new coal-fired power plants in the U.S. If the long-term goal is to increase renewable base load electricity generation, additional incentives are needed to encourage new CSP plants to use thermal energy storage in the U.S. [Copyright &y& Elsevier]

Abstract: Nowadays, conventional coal or gas fired power plants are the dominant way to generate electricity in the world. In recent years there is a growth in the field of renewable energy sources in order to avoid the threat of climate change from fossil fuel combustion. Solar energy, as an environmental friendly energy source, may be the answer to the reduction of global CO2 emissions. This paper presents the concept of Solar Aided Power Generation (SAPG), a combination of renewable and conventional energy sources technologies. The operation of the 300 MW lignite fired power plant of Ptolemais integrated with a solar field of parabolic trough collectors was simulated using TRNSYS software in both power boosting and fuel saving modes. The power plant performance, power output variation, fuel consumption and CO2 emissions were calculated. Furthermore, an economic analysis was carried out for both power boosting and fuel saving modes of operation and optimum solar contribution was estimated. [Copyright &y& Elsevier]