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In the present study, innovative energy efficiency enhancement methods and cleaner production in conventional waste-fired CHP plants are presented. This includes the medium- and low-grade solar thermal systems and flue gas condensation for feedwater heating in different arrangements. The article presents a thorough thermodynamic, economic, and environmental assessment of all the possible scenarios and then ranks the best solutions in different aspects. For making the results reliable, the solutions are applied to a waste-fired CHP plant in Denmark. For this, a transient simulation of the proposed configurations is performed via TRNSYS software for an entire year. The results indicate that the proposed models can produce more power and heat than the conventional plant but with different effectiveness factors. According to the economic results, a design consisting of a flue gas condensation circuit and parabolic trough collectors for the open and closed feedwater heater form the best configuration. The exergy assessment results indicate that the waste incinerator with annual irreversibility of 128.4 GWh is the most important component exergetically. Finally, the parametric study results show that the increase of incineration temperature significantly affects the power and heat exergy efficiency ratios.

In the present work, a novel hybrid solar-based smart building energy system is introduced and studied. The system comprises innovative photovoltaic-thermal-cooling (PVTC) panels integrated with hot and cold storages with two-way interaction with electricity, heat, and cooling networks (if any). The proposed system is compared with PV-based systems integrated with battery and heat pump for a case study complex building in Aarhus, Denmark. The comparison is conducted by evaluating the performance and economic indicators and investigating the effect of significant parameters on each scenario via a parametric study. Furthermore, the optimal operating conditions and sizing of the proposed system are determined using the genetic algorithm method considering initial cost and traded energy with local energy networks as the objective functions. The comparison results show that the proposed solution is the most cost-effective scenario with the lowest initial cost of about 457,000 $ and a payback period of 6.6 years. This is mainly due to the simultaneous interaction with electricity/heat/cooling networks as well as the elimination of the battery and the heat pump, which are offered by the proposed scenario. It is shown that, in comparison to PV panels, the PVTC can produce 328.7 MWh and 125.6 MWh extra heat and cooling annually. The scatter distribution of significant parameters shows that the panel area and heat storage capacity are not sensitive parameters, and keeping the cold storage capacity at the lower bound is a techno-economically better option.

In the present study, a novel design of large-scale biomass-based heat-driven building cooling system is proposed and investigated for different regions of India. The study is enriched by a thorough benchmarking analysis of various scenarios (24 scenarios in total) for assessing the influence of different types of biomass, various configurations of the cooling system, and different biomass heater layouts on thermodynamic, economic, and environmental aspects of the proposed solution. For this, developing a MATLAB code, hourly, monthly, and annual comparisons are made to ascertain the best scenario from different aspects. The economic investigations reveal the superiority of the scenario comprising a specific design of biomass-heater using Prosopis and double-effect chiller with the lowest levelized cost of cooling (LCOC) of 0.031 $/kWh. The integration of a double-effect chiller with this heater using wood chips leads to the lowest emission index of 0.19 kg/kWh. The results further demonstrate that the LCOC is highly sensitive to the fluctuation of the cost of the biomass type, which is a function of availability in different regions of India. Therefore, the study is a secure reference indicating which scenario would result in the best techno-economic-environmental performance among all possibilities in different areas of the country.

There is a variety of solar-based energy system designs for buildings. Although these systems are economically profitable, reducing the energy cost of the buildings over time, their penetration has not been that impressive yet due to their high initial cost. In this study, an energy system comprising a few PVT panels (without any batteries) and a heat storage tank is proposed and investigated for smart buildings with two-way interactions with both heat and electricity grids. Removing the battery from the system would result in a sharp reduction of the cost of the system and, thereby, will make incentives for the end-users to adopt the solution. This novel system will not only supply the buildings’ real-time electricity and domestic hot water needs but also will compensate for a significant portion of the buildings’ energy expenses by selling the surplus generations to the electricity and heat networks. The dynamic model of the proposed system is comprehensively analyzed from thermodynamic and economic points of view using TRNSYS software. Additionally, defining the overall annual exergy efficiency, and the total product cost as the objective functions, optimization of the design and size of the system employing the TRNOPT tool has been done. It is shown that the optimized system results in 16.7 €/MWh and 7.7 €/MWh lower energy costs for electricity and heat of the buildings compared to when the buildings’ demand is only supplied by heat and electricity grids.

This forward-looking perspective article presents a status overview of solar photovoltaic-thermal (PVT) panels in net-zero energy buildings from various points of view and tries to picture the future of the technology in this framework. The article discusses the pros and cons of PVTs' state of practice, design developments, and integration possibilities. Investigations show that for sufficiently benefiting from the potential of PVT panels for smart buildings, some major challenges such as high investment cost and lack of two-way interaction with district energy systems must be addressed. In addition, some of the most promising research focuses of the field are discussed as the further possible solutions for advancing the state-of-the-art in this context. These are finding feasible ways to reduce the cost of PV cells, downsizing battery and heat pumps based on optimal two-way interactions with thermal and power grids, tri-generating via enabling the panel for passive cooling (PVTC), and developing concentrating PVTs and PVTCs. The potential impact of this article's advice for future research may be an increased motivation of buildings to be furnished by such solar-based energy systems and thus a higher contribution of PVT panels in net-zero and smart energy buildings.

This article presents an innovative combined heat and power system comprising a solid oxide fuel cell (SOFC), a heat recovery unit, and a lithium bromide absorption power cycle (APC). The energy, exergy, economic, and environmental perspectives of the proposed system are compared against the same configuration using an organic Rankine cycle (ORC), recovering the waste heat of the SOFC. A multi-criteria optimization based on the Grey Wolf approach is applied to each system to specify the best operation conditions having the exergy efficiency and total cost rate as the objectives. Furthermore, a parametric investigation is conducted to assess the effects of changing the decision variables on the systems proficiencies. The results indicate that although the ORC-based cycle is economically very slightly superior, the integration of the SOFC with the APC offers a much higher exergy efficiency due to the better temperature matching between the working fluid and heat source. Optimization can increase the exergy efficiencies of the SOFC-ORC and the SOFC-APC systems by about 13.8% and 14.7% while reducing the total cost rate by 11.2 $/h and 11.0 $/h, respectively, compared to the base system. Environmental analysis results reveal that APC use leads to a lower emission of 2.8 kg/MWh.