In this work, the novel concept of non-uniform temperature district heating (NUTDH) system with decentralized heat pumps and standalone heat storage units (HPHS) is proposed. In the NUTDH-HPHS ...system, the temperature within the transmission pipeline is always at the ultra-low level of 35–40 °C, which is sufficient for space heating use. The heat pumps will increase the temperature within the distribution pipes to 70 °C during a short period of time a day. This temperature is to provide the domestic hot water (DHW) need of the consumers. Heat pumps are sized in neighborhood scale, and as each neighborhood is supplied with a high temperature just for a short time a day, each heat pump may be assigned for a few neighborhoods. As not always high-temperature water is available, the substations are equipped with storage tanks. In this system, the rate of heat loss is minimal, legionella risk is absolutely zero, and there is a strong synergy between the power and heat sectors. The system is designed and analyzed for a case study. The results are also compared with the performance of other popular district heating (DH) schemes. It is demonstrated that the NUTDH-HPHS system shows the best performance.
•Heat pumps come into service for a district heating with non-uniform temperature.•The system works at ultra-low temperature level for space heating most of the time.•Medium temperature is supplied by heat pumps for domestic hot water preparation.•The proposed system offers a low rate of heat loss and ensures no legionella risk.•The system outperforms others in terms of an overall energy-economic performance.
•The waste heat recovery in an innovative waste-CHP-ORC plant is proposed.•Two alternative working fluids are considered to make the system environmentally friendly.•The combined configuration is ...designed and analyzed techno-economically.•The energy and exergy efficiencies increase up to 20% and 10%, respectively.•The payback period of the system is improved by about 10%.
A smart hybrid power plant comprising a waste-fired CHP (combined heat and power) plant accompanied by a small-scale organic Rankine cycle was recently designed and analyzed thermodynamically. The objective of this hybridization is to maximize the share of electricity production of waste-CHP plants rather than a higher heat production rate in a cost-effective manner. In this work, utilization of the exergy of the hot flue gas of the waste-fired CHP unit in order to increase the potential of the organic Rankine cycle for maximizing the net power output of the hybrid cycle is proposed and techno-economically analyzed. In addition, the effect of using alternative environmentally-friendly organic working fluids on the performance of the system was investigated. The results of the study show that by the flue gas potential utilization of the same CHP unit, the size of the organic Rankine cycle may increase significantly, leading to a larger power output of the plant. As such, the net exergy and energy efficiency values of the combined plant in various operational conditions are improved compared to its primary configuration by, respectively, about 10% and 20%, when both of the main CHP cycle and the organic Rankine cycle are working at nominal load. In addition, this exergy utilization is beneficial economically as well, decreasing the payback period of the parallelization project by about 10% (from 7.4 years to 6.7 years). The alternative organic working fluid does not make a significant change in the technical and economic performance indices of the system.
Concentrating solar power plant will be a key component of the future energy systems in which the share of renewable energy is extremely high. A major challenge of this technology is, however, its ...intermittent power output, slowing down its rate of implementation in the global energy matrix. As such, waste incineration is a popular technology in the developed countries as a smart measure for the disposal of municipal waste and generating free energy. In this study, a hybrid configuration of a concentrating solar power plant accompanied with a waste incineration unit is proposed. In the proposed system, the waste incinerator offers a variable heating duty in order to regulate the power output of the concentrating solar power plant. The hybrid plant is designed for a case study in Denmark and is thermodynamically analyzed. The results of the simulations are presented and discussed. It is shown that the hybrid system can pave the bed for increasing the share of solar thermal power and bringing more waste incinerators to the electricity market. A 10 MWe hybrid power plant may prevent up to 8000 tonnes of carbon dioxide equivalent emission per month. The overall efficiency of the hybrid system is expected to be 24%.
•A hybrid concentrating solar power plant accompanied with a waste incineration unit is proposed.•The proposed system provides a cost-effective and dispatchable electricity to the grid.•Thermodynamic performance and environmental impacts of the system are investigated.•The net annual energy efficiency of the system is approximately 24%.•The system contributes to the prevention of a large amount of CO2e emission.
Waste-fired CHP plants are largely contributing to the base load supply of heat and electricity sectors of several European countries. In such systems, about two-third of the production is heat and ...about one-third is electricity. In this study, the utilization of a certain portion of the heat production of a waste-fired CHP plant as the heat source of an Organic Rankine Cycle (ORC) is proposed. The main objective is to maximize the share of electricity production of waste-CHP plants instead of a higher heat production rate in a cost-effective way. The inspiration for this idea is that not only electricity is extremely more valued in most of the European energy markets, but also their heat sectors are to be occupied with efficient electricity-driven technologies, e.g. heat pumps. This work presents a detailed thermodynamic analysis of the proposed combined system and the best share of heat supply for driving the ORC unit is investigated. The results show that an electricity efficiency improvement of up to 25% is achievable via this integration while the heat production capacity of the power plant still remains significant. It is shown that the integration picks up of exergy efficiency of the power cycle.
•The combination of a waste-CHP plant with an Organic Rankine Cycle is proposed.•The aim is to maximize power output of the system instead of a higher heat output.•The combined configuration is designed and analyzed thermodynamically.•The power output may increase up to 25% via the proposed integration.•A power-to-heat value of 4.8 is needed to make the system feasible economically.
This is quite common to supply the heating demand of absorption chillers via the local district heating system. This can be technically challenging during summer when the district heating system does ...not have enough load to take advantage of the high-temperature discharged flow from the absorption machine. In this study, employing parabolic trough solar collectors for the co-supply of a major heating demand of the chiller and district heating network is proposed. As the expansion of district heating systems for the newly built areas is mainly implemented in lower supply temperatures, the proposed solution works more cost-effective for such cases. The proposed solution is thermodynamically analyzed for an entire year in a case study. The results show that the system totally resolves the technical problem of the case study, offers a significant contribution to supply the district heating demand and presents an impressively better economic index compared to the conventional configuration. Results show that heat demand of the chiller is zero for one-third of the year, the system feeds district heating with a heat supply rate of over 1 MW for about three months, and the internal rate of return of the system is 5.7% for 8 years of operation.
•Solar-driven absorption chiller used to supply district heating and cooling.•Nearly 40% of the cases, solar field provides 14 kg/s hot water.•Nearly 60% of the cases, solar field has no contribution in heat production.•25% of the cases, solar supplied heat is more than 1 MW.•The IRR value was found to be 5.7%.
In this work, a thorough exergoeconomic analysis of a hybrid solar-waste driven power plant is presented. The objective is to give a clearer picture of the main irreversibilities, their corresponding ...costs and to find some effective yet feasible solutions to improve the efficiency and cost-effectiveness of the power plant. For this, the power plant is exergetically modeled, the exergoeconomic assessment is accomplished, the exergy losses are weighted, the cost of these losses are estimated and finally, the solutions are given. The cost of electricity was improved from 0.202 US$/MJ to 0.137 US$/MJ, after the application of the recommendations. Results show that electricity cost decreases in daily hours from a maximum of 10% in winter to the maximum of 26% in summer. Furthermore, the results of sensitivity analysis on the plant indicates that a hybrid cycle with turbine isentropic efficiency of 0.85, steam extraction ratio of 0.36 and inlet turbine temperature of 400 °C offers a 32% lower electricity cost compared to a cycle with a turbine isentropic efficiency of 0.75, steam extraction ratio of 0.16 and inlet turbine temperature of 500 °C.
•A hybrid CSP plant accompanied with a WI unit is proposed.•The proposed system provides a cost-and energy-effective electricity, highly dispatchable to the grid.•A detailed thermodynamic model of the system is accomplished.•Three different scenarios, i.e. configurations and operation strategies, are considered and analyzed.•The environmental impact of the system is studied and compared to the competitor systems.
A novel hybrid configuration of solar parabolic trough collectors–waste incineration power plant was recently analyzed energetically in Denmark. Taking into account the true meaning of sustainability ...which is environmental friendliness and cost-effectiveness, and considering the existing gap of knowledge on the thermodynamic performance aspects of this hybrid system, this work conducts a thorough thermodynamic and sustainability analysis of this power plant. The main aim is to give a clear picture of the main advantages and any possible shortcomings of the hybrid power plant. For this purpose, the performance of the system is simulated for an entire year of operation under realistic solar irradiation fluctuations. The energy performance indices of the system are quantified and discussed. The exergy assessment of the hybrid cycle is accomplished, and the main sources of exergy destruction and economic losses are identified. The results show that the steam generator and the turbine cause the largest rates of irreversibilities of 36% and 20.8%. The environmental benefits and the overall cost of energy production of the system are calculated and compared to some other alternative power plants. In addition to the consistency of electricity production, the LCOE of the hybrid power plant decreases by 67% in comparison with the solar power plant. Comparing the system with a natural gas-fired power plant in terms of CO
2
emission, it is shown that the hybrid system leads to less 74.5 thousand tonnes of CO
2
emitted over an entire year.
Creating greater thermal efficiency is desirable yet challenging in many industrial applications. Employing nanofluids for increasing the thermal behavior of the working fluid and consequently the ...overall heat transfer rate is an interesting solution that has widely been studied in the literature. This study, however, proposes the use of a special geometry of disturber (i.e., a helical-twisting shape) for a circular duct with nanofluid (water–CuO) as the heat transfer medium and a forced convective flow for this objective. To assess the effect of this instrument, FVM is employed to simulate the hydrothermal performance of the flow through the duct and the disturber. The main parameters of the study include the effects of the width of the disturber blade and inlet velocity on Darcy factor and the heat transfer coefficient. The homogenous model was used for the properties of nanomaterial. The results of the simulations show that better turbulence, i.e., a greater performance, is observed as the width of the flow disturber blade increases and the Reynolds number picks up.
•A solar assisted bifunctional absorption chiller is proposed, designed and analyzed.•The aim is to adjust the operation of district heating connected absorption chillers.•The system supplies heat to ...the district heating network during the cold months.•A thorough energetic and economic assessment of the system is done for a case study.•The effectiveness of the system is assessed in terms of greenhouse gases emission.
Supplying the heating demand of the absorption chillers connected to district heating systems is challenging during summertime when there is not enough demand to take advantage of the high temperature discharge water of the chillers. In this work, a new configuration of a bifunctional solar assisted absorption chiller is proposed by which the heating demand of the chiller is efficiently supplied. This innovative system takes advantage of an evacuated tube solar thermal system and has no cooling tower. The proposed system is designed and simulated for a case study in Denmark, i.e. the Aarhus University Hospital. The effect of applying the proposed system to the performance of the hospital cooling systems and the local district heating network is assessed over an entire year. The results show that the proposed system could make a 30% contribution to the heat preparation process of the absorption chiller during the summer and a 17% contribution seen over the entire year. Aside from this, the system can contribute a large amount of heat production for district heating purposes during the cold months. As such, the effect of replacing the conventional system with the proposed configuration on the CO2 emission of the case study is evaluated. Finally, the two economic criteria of net present value and internal rate of return are used to assess the effectiveness of the project economically, finding it very feasible and economical with a payback period of less than two years.
Subcooled compressed air energy storage (SCAES) is a system cogenerating heat, cooling, and power at a high coefficient of performance. In this study, hybridization of a SCAES system with a ...large-scale solar-powered absorption chiller (SPAC) is proposed. The hybrid system sustainably provides cooling and power at high efficiency. The combined SPAC-SCAES system is appropriate for locations with large cooling demand and grid-connected renewable power plants. Employing this system, the renewable power plant may efficiently operate in the power market, maximizing the financial benefits by storing its surplus power and reclaiming the stored energy for balancing the demand and the production. In addition, a large amount of cold is produced, increasing the profitability of the system. This combined system is designed and simulated for a typical wind farm plus an absorption chiller of a hospital. Non-linear programming (NLP) is used to optimize the operation strategy of the SCAES and based on the given results; the components of the system are sized. The results show that by the combined system a massive amount of balancing power can be produced for the grid, a reliable integration between the cold and electricity sectors is made, and the levelized cost of energy (LCOE) decreases remarkably.
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•A new hybrid configuration for trigeneration of heat, cold and electricity is proposed.•The system comprises a solar driven absorption chiller plus an electricity storage unit.•The operation of the electricity storage unit is determined via optimization methods.•The components of the hybrid system are sized based on techno-economic criteria.•The performance of the hybrid system is simulated and analyzed for a case study.
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