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The methanol and electricity poly-generation system based on coal partial gasification is proposed. Techno-economic analysis of the system is conducted by using Aspen Plus and the effects of methanol synthesis temperature and cyclic gas reflux ratio on the system performance are studied. The detailed economic data are obtained. The IGCC system is established simultaneously and compared with the poly-generation system. The results show that both methanol production and system efficiency decrease with the increase of methanol synthesis temperature. Methanol production increases while system efficiency decreases with increase of the recycle gas ratio. System efficiency would reach as high as 56.8%, while the system efficiency of IGCC is 53.11%. By the calculation of the economic data, the IRR and the payback period of the poly-generation system are 24.1% and 4.14 years, respectively. While IRR and payback period of IGCC system are 3.4% and 18.06 years, respectively. The results show that methanol and electricity poly-generation system based on coal partial gasification has a promising prospect.

Energy management is very important for the effective operation of a hybrid system composed of various energy sources. The present work aims to develop an effective control strategy in order to reduce the grid-maximal contracted power of a hybrid building containing PV systems, combined heat and power (CHP) unit and battery energy storage system (BESS). The proposed solutions (new control strategy and increased PV system size) were carried out based on the analysis of monitored data collected from May 2016 to April 2017 representing the real behaviour of the hybrid system. The obtained results demonstrated the effectiveness of the developed control strategy in decreasing the grid-maximal contracted power from 140 kW to 120 kW and increasing the self-sufficiency of the building. Furthermore, by combining the proposed control strategy and the proposed PV system, the self-sufficiency can be even more increased and the grid-maximal power can be reduced by 30% leading to an annual savings of almost 4000 €/year. Finally, the financial assessment revealed that the payback period of the proposed solution is less than 10 years confirming the profitability of the investment.

In hot climates, performance of vapor compression cooling cycles decreases sharply, and consequently, energy consumption rises. Pre-cooling the air before it enters the condensing system can enhance the system performance and protect our environment. In this study, an experimental investigation on energy savings of a split air-conditioning utilizing evaporative cooling technology is conducted under a wide range of weather conditions. Thermal performance of commercial corrugated papers which are available at low cost is investigated experimentally in a wind tunnel. These characteristics are used in designing the evaporative cooling system. Depending on the maximum saturation efficiency, low pressure drop, and maximum performance, the optimum pad thickness was observed at 100 mm. Results showed that at this thickness, the power consumption decreased from 15 to 22% and the overall COP increased from 29% to 53%. Depending on the energy cost and regional usage, the maximum savings in the overall energy cost is $21.6/year. The cost of water consumption is $ 1.82/year. The payback period for the proposed system is less than three years and finally the life-cycle cost saving is between 242 and $ 400.

One main obstacle to the implementation of low-temperature district heating is the existing infrastructure along with consumer heating devices that were usually designed for higher operating temperatures. If a DHN is installed for a new urban area, these obstacles can be avoided. This study presents an analysis of alternative heat supply scenarios for the newly developing city subdistrict of Kopli (Tallinn, Estonia). The following scenarios were analysed from economic and environmental aspects: scenario A-connection to the existing DHN (supply/return temperatures 95 °C/55 °C, gas-fired boiler house); scenario B-small local DHN (80 °C/40 °C, small gas-fired boiler house); scenario C-small local LTDHN (60 °C/35 °C, small gas-fired boiler house, integrated large-scale heat pump using seawater as heat source). The results of the study have shown that the primary energy consumption per 1 MWh of heat consumed is 1.33 MWh for scenario A, 1.15 MWh for scenario B, and 0.71 MWh for scenario C. To achieve IRR = 7%, a 4 year discounted payback period was calculated for scenario B, with the NPV of 1.000.000 EUR after the period of 10 years. For scenario C, the payback period is more than 5 years, and the NPV is 2.600.000 EUR after 10 years.

Process level integration of solar energy could give an economically feasible solution if the industrial process allows its practical integration. The solar-augmented industrial process behaves as a complex system influenced by uncertainty of solar radiation, variability of demand temperature and process time schedule as well as possibility of thermal stratification in the storage. Addressing these issues to reach the most economical solution has two dimensions to it. First, the solar thermal system needs to be optimally designed. This requires the development of a performance criterion that will deliver maximum solar energy to the industrial process, avoid large variations of energy in the storage, and meet investment constraints. Second, the identified optimal system should be dynamically controlled to enable uniform heat distribution and efficient auxiliary heat utilization. This paper presents a holistic design optimization and control approach for a solar-augmented industrial process to facilitate decision support. The proposed solution is designed and optimized for a dyeing industrial process case study that resulted in a 5.7 year payback period, 56.3% solar fraction, and 252.2 tons equivalent carbon emission reduction. Furthermore by implementing dynamic control, about 12.4% increase in solar gain that led to a 5.6% reduction in payback period is identified.

This paper presents an integrated mathematical optimisation approach to synthesise a bioelectricity supply chain network with minimal costs. Detailed economic evaluation was performed to determine the optimum location of centralised or decentralised biomass pre-treatment and power plants. Once the optimum bioelectricity supply chain network is established, input-output modelling of the network is formed. Next, feasible operating range analysis is performed. A palm-based bioelectricity supply chain case study in Malaysia is used to illustrate the proposed approach. Based on the optimised results, a total of 80.90 MW of bioelectricity are generated with an estimated net present value of USD 123.94 million and a payback period of 5 years. Meanwhile, the feasible operating range analysis indicated that the synthesised bioelectricity supply chain network possessed multiple feasible operating ranges; 5.06–10.04 MW, 11.88–36.08 MW and 44.26–101.16 MW. Based on the result, the decision makers can determine the potential of the future bioelectricity projects according to different seasons of supply and demand variations.

Distributed energy systems (DESs) are becoming increasingly popular because of their high-energy efficiency and low pollution emissions. Accurate performance evaluation of such systems is critical for processes at the early design stages. However, there are considerable uncertainties in terms of the parameters used for performance evaluation and design optimization, including component efficiencies, customer demands, and energy markets. These uncertainties can significantly influence the performance of DESs. Without consideration of these uncertainties, the performance of DESs can be overestimated or underestimated, which leads to inaccurate decision-making. Therefore, this paper presents a comprehensive evaluation of the performance of DESs by considering uncertainties in 12 parameters that relate to the electrical and thermal efficiencies of generators, efficiency of chillers and pumps, load density, energy markets, and so on. The energy and economic performance of DESs under each uncertainty are analyzed and compared with that of conventional energy systems. The suitable conditions for using DESs and other factors that can influence their performance are determined. The results of this study can serve as a guide for design optimization and policy development to promote the use of DESs in China.

The study of supply and demand match increasingly becomes an enormous challenge in park integrated energy system (PIES) because it has a comprehensive relationship between multiple energy sources and multiple energy demand. This paper proposes a new type of supply and demand matching to accomplish the economic optimality of match under the same criteria, considering supply and demand changing simultaneously. The quantitative indexes of supply and demand energy conversion technologies (ECTs) is established considering the economic and technical characteristics of full life cycle comprehensively, which are defined as supplied technical cost level and demand technical cost level. Then, the novel energy supply and demand matching model is established. The loop iteration algorithm of the new matching model is established based on linear programming model. Numerical study is introduced based on the data of the cooling, heating and electrical load in a typical day. The results show that the priority order of each ECT is different when the output of all ECTs increasing gradually. The investment payback period is only 1.94 years. The new supply and demand matching model can reduce carbon emissions by 80,555 tons.

The need for refrigeration in the food retail industry and specifically in supermarkets, currently accounts for about 30% to 60% of the total energy consumed in the UK stores. A key characteristic of this consumption, is the high amount of low-grade heat rejected by the condensation units to the ambient air. The aim of this study, which focuses on transcritical CO2 (R744) refrigeration cycles, is to assess whether the use of a water-cooled condenser rejecting heat to the soil via an intermediate closed-loop water-circuit, can improve the overall cooling performance, while also considering the economic implications of this modifications. In this work, a detailed model simulating the operation of an existing supermarket refrigeration system is presented and validated against field data measurements taken from a refrigeration system in a UK supermarket. The examined direct-expansion system comprises an air-cooled condenser coupled with two sets of compressors for the provision of intermediate and low-temperature cooling. This baseline model is then modified and used to evaluate the performance of a similar system, in which a water-cooled condenser is used instead of the existing air-cooled unit or in parallel to it. Preliminary results indicate that the use of water-cooled condensers has the potential to reduce the energy consumption of these refrigeration systems by up to a factor of 5 when the external temperature is high. However, in cold ambient conditions, the air-cooled condensers reject 10% less heat, resulting in a better system performance. Furthermore, a more thorough case study is developed in order to examine the yearly operation of the existing system, and to compare this to various water-cooled alternatives. The analysis indicates a reduction of approximately 3% in the energy consumed by the water-cooled system (compared to the reference benchmark air-cooled system), and a reduction of almost 6%, for a hybrid system with coupled air-cooled and water-cooled condensation units in parallel operation. The economic evaluation of these systems shows that electricity costs can be reduced by up to $4000 (£3450) per year for a large supermarket (1400 m2 (15000 ft2)) with a system using a water-cooled condenser. The annual maintenace costs of the system are increased by about $600-$1000 (£500-£800) per year, and the capital costs are marginally reduced by less than 5% leading to a promising investment for commercial refrigeration with a payback period of less than 5 years, when the system is installed in a new store.

This paper addresses the techno-economic, energetic and environmental assessment of the indirect and direct production of bioenergy using Pinus patula (PP) as raw material. Ethanol and synthesis gas are evaluated as main products through biochemical (fermentation) and thermochemical (gasification) routes, respectively. The complete characterization of the raw material was performed aiming to determine the chemical, proximate and elemental composition of the PP that is used as starting point for the simulation procedure. Mass and energy balances were obtained from the simulation of both processes using the software Aspen Plus v9.0. Different economic criteria such as Net Present Value (NPV) and Payback Period (PBP) were used to determine the profitability of both processes. The overall energy efficiency was calculated considering the relation between the energy content of the products and the energy content of the inputs (raw materials and utilities). The environmental assessment involves an attributional life-cycle assessment (LCA) of different systems such as seedlings production, PP cultivation, harvesting and collection, and the evaluated processes using a cradle-to-gate approach. As a result, the production of ethanol evidenced a low production cost (0.549 USD/L), higher energy efficiency (45.1%) and higher CO2 emissions (0.17 kg per MJ EtOH) in comparison to the biomass gasification.

In this study, the cost analysis of solar power system, where is located in Elazig, Turkey is calculated according to levelized cost analysis method. In the economic feasibility studies carried out by the firms, many parameters such as interest rates, cost of money, detailed sunshine duration, monthly net profit-loss status in one year, cost of investment according to changing interest rates are not taken into consideration. All these parameters, which were not considered by the firms, have been calculated in this study. The payback period of investing in the solar power plant is calculated as 13 years, the payback period of it is calculated as an average of 6.6 years by the firms. The annual profit of a 1 MW solar energy plant is 89,467 US $. Present worth and annual capital cost of the solar power plant are calculated as 1,156,763 US $ and 1,181,875 US $, respectively. The capital cost flow of the investing in solar power plant is determined as 5.628 US $/h. When the results obtained from this study are evaluated in a general framework, the high interest rates in developing countries will have a negative effect on the investments in the solar power plants.

The application of an innovative translucent superinsulated latent heat storage wall, combining transparent insulation material and phase change materials (TIM-PCM wall), on the envelope of a typical office under different climates is evaluated. Energy and economic analysis related to this application are presented. The simulation process is carried out using an experimentally validated numerical model. The results show that the incorporation of the TIM-PCM wall, on the south orientation, is more efficient than the use of a double-glazed in all considered climates. The optimum TIM-PCM wall area is evaluated economically through life-cycle cost and payback period analysis. The purpose is to ensure effective performance of the wall in each climate and at the same time to ensure economic viability. The results show that, in polar and subarctic climates, the application of the TIM-PCM wall has a high economic value and the investment appears to be attractive, the payback period being 10.5 years and 7.8 years respectively. In Dras (continental climate), the use of the wall is found economically unfeasible due to low energy prices and high discount rates. At current prices, the TIM-PCM wall investment in Sacramento (Mediterranean climate) and Toronto (Humid continental) does not offer economic benefits.

Passive design strategies are the most feasible and economic ways of energy and thermal management in buildings, if appropriately incorporated at the conceptual design stage. Though many works have been reported on the application of external shading options, a shading strategy that incorporates the features of both external shading devices and self-shading envelope, is yet to be explored. The present study was focused on the energy saving potential and economics of incorporating external shading devices with self-shading envelope for a multi-story hotel building in hot-humid climate of Saudi Arabia. The modeling and the energy simulations were performed by DesignBuilder (Version 4.5.0.148). According to the base-design geometry of the building, appropriate shading options were proposed for the north, south, north-east, north-west, south-east and south-west facades. External walls and roof were insulated with fiber glass and windows were double-glazed (DG), in compliance with the Saudi Building Code - 601. The shading strategy was chosen in such a way that it forms part of a self-shading envelope while improving energy performance and contributing additional space at very affordable cost. The results show that the proposed shading could save the annual energy consumption of the building by 20.5% compared to the base case. The payback period for the additional investment required for incorporating the passive shading strategy is estimated to be 2 years. Study of another option by improving the baseline insulation and glazing (with polyurethane in walls and roof and triple low-e glazed shows, without shading) shows that it saves only 5% of annual energy consumption, and the payback period is unacceptably long (84 years).

As a highly urbanised city-state with limited rooftop space but large facade areas of skyscrapers, Singapore is particularly suitable for the implementation of building-integrated photovoltaics (BIPV). This study aims to identify relevant barriers that still hinder the greater adoption of BIPV perceived by stakeholders in Singapore, as well as the drivers for BIPV that would lead building sector to adopt BIPV technologies. The study involved five important groups of stakeholders i.e. governmental authorities, building developers, architects, engineers, and PV/BIPV manufacturers to participate in a questionnaire survey. The results identified that on-site generation of clean energy bundled with economic benefits, Green Mark certification, and avoidance of CO2 emissions are the most influential drivers, while long-term payback period, high upfront cost, and low energy conversion efficiency are the three most substantial barriers to BIPV. Furthermore, one-way analysis of variance (ANOVA) was conducted to examine whether the various stakeholder groups perceive the drivers and barriers differently. It was discovered that various stakeholder groups perceive the drivers similarly, but the significantly different opinions have been perceived on several barriers. This study provides suggestions to overcome barriers to BIPV not only in Singapore, but also other countries that aim to promote BIPV technologies.

Environmentally-friendly working fluid selection and multi-objective evaluation have been paid a great attention in organic Rankine cycle (ORC). Based on a modified analytic hierarchy process, a multi-factor evaluation method for trans-critical ORC (TORC) is developed first. The multi-factor indicator consists of eight indicators including energetic, exergetic, economic and environmental criteria (4E). The net power output, system efficiency, total exergy loss, exergy efficiency, cost per unit of time, electricity production cost, dynamic payback period, and emissions of CO2 equivalent (ECE) during life-time are considered. R134a, R32, R1270, R290 and R1234yf are selected as potential working fluids. The results show that the performance of R134a is the best followed by R32, R290, R1270 and R1234yf when only thermo-economic performances are considered. R290 shows the maximum comprehensive emission reduction of 8019 tons CO2, eq during life-time followed by R1270 being 7529 tons CO2, eq. The primary source of ECE from R134a, R32, R1270 and R290 is fluid leakage, accounting for over 68–83%. In multi-factor evaluation, R290 and R1270 exhibit higher feasibility level than R134a when the environmental impact is paid great attention. The multi-factor evaluation method is effective and valid to conduct comprehensive feasibility evaluation for decision-making.

The fossil energy crisis is a great test for human society, and the technology of methanol reforming for hydrogen fuel cell has attracted much attention. Based on Aspen Plus - the large business process simulation software, this paper constructs a distributed energy system based on solar methanol reforming SOFC. It is combined with GT-ST power generation system and AHP-AR. We optimized the design of system integration mode, and the steady-state model of thermal calculation of the system is constructed. The calculation results show that, power, heating and cooling output of MR-SOFC-CCHP system are 226.9 kW, 46.6 kW and 36.4 kW respectively under design conditions. The power output efficiency and thermal efficiency were 59.7% and 81.6% respectively. System annual profit: 517,000 yuan/year. Compared with the annual profit of CCHP system of 275,000 yuan per year, its annual profit is increased by 242,000 yuan/year. The investment payback period of MR-SOFC-CCHP system decreases with the decrease of SOFC price. With the price of SOFC reduced from 50,000 yuan/kW to 15,000 yuan/kW, the investment payback period of MR-SOFC-CCHP system decreased from 14.0 to 5.8 years.

In this paper, a novel power generation system integrating a natural gas expansion plant with a geothermal organic Rankine cycle (ORC) was proposed. The paper begins with an introduction to the thermodynamic and economic models of the system. Secondly, contrastive analyses of three candidate working fluids were made, leading to the selection of R600 as the best fluid for the system, and the effects of gas pipeline parameters fluctuation on the system performance were originally investigated and analyzed based on the actual operating data of a natural gas PRS, located in Xiqing district, Tianjin, China. Finally, a multi-objective optimization for the system using R600 as working fluid was done to find the optimal evaporation temperature based on the TOPSIS decision-making method, and exergy loss analysis was accomplished at the optimal condition. The results indicated that the proposed system had a net profit of 3.97 M$ in the life time and a small payback period around 2.0 years at the optimal evaporation temperature of 45.5 °C where the system had a high thermal efficiency of 89.8% and exergy efficiency of 84.13%. Additionally, the condenser has the greatest potential to reduce the total exergy loss of the system.

As the main solid waste in the iron and steel industry, the waste heat recovery and comprehensive utilization of blast furnace slag had great significance for energy conservation and sustainable development. This paper proposed a novel full-chain blast furnace slag utilization system to solve the problem of waste heat recovery and high value-added production. Cascade recovery of slag waste heat was realized by using coal gasification reaction and the waste heat recovery ratio reached 73.61%. Meanwhile, two kinds of high value-added products of X-type zeolite and hydrotalcite-like compounds were synthesized simultaneously by using the beneficial components of blast furnace slag after fully recovering waste heat. Ultimately, the economic feasibility of the system was analyzed from two aspects of investment and profit. Under the reasonable economic assumptions, payback period of the project was 0.14 years, 10-year net present value was $ 326493.98 million, return on investment and internal rate of return were 737.74% and 312.82%, respectively. The sensitive factors of the system fluctuated within 40% through sensitivity analysis. The project could still be profitable in the production year. With great economic benefit and anti-risk ability, the novel full-chain blast furnace slag utilization system had potential in energy saving and emission reduction.

Effective waste heat recovery is a key solution toward meeting the increasingly stringent fuel economy and CO2 emission standards. In this paper, the cogeneration of electricity and freshwater was devised to recover the waste heat of a Diesel engine. The dual-pressure Kalina cycle and the humidification-dehumidification desalination system were used for power generation and freshwater production through exhaust gas energy and jacket water energy, respectively. In addition, energy, exergy, exergoeconomic, and economic analyses were applied for modeling the proposed system. The optimum performance of the system was determined by applying the multi-objective genetic algorithm. A parametric analysis was also performed to assess the effect of various parameters on the system's performance. The feasibility of the plant for investment was studied using the net present value (NPV) and payback period concepts. Based on the findings, the maximum exergy destruction rate was obtained for the condenser with a value of 39.88 kW . Moreover, the payback period and NPV values were calculated to be 7.4 years and 165814 $ for the electricity price of 0.09 $ / kWh . For the η ex ‐NPV‐SUCP optimization scenario, the optimum values were obtained to be η ex = 34.85 % , NPV = 0.260 $M , SUCP = 51.33 $ / GJ , W ˙ net = 83.55 kW , m ˙ fw = 0.115 kg / s , and PP = 5.67 years .

A walk-in type solar greenhouse dryer supplemented with solar air heating system has been developed with an objective of sustainable development. One of its novel features is the use of an evacuated tube solar air heating system with the greenhouse dryer to achieve required drying temperature for different products in north India plains. This dryer was tested in laboratory in both batch and semi-continuous mode for turmeric (Curcuma longa). The open sun drying was used as control. The thermal efficiency of the dryer for batch and semi-continuous drying obtained are 18.5% and 22.5% respectively. Drying time in comparison to open sun drying has been found to be 55% approximately. The quality of dried turmeric obtained using this dryer is superior to open sun drying in terms of polishing loss, curcumic content, volatile oil content and colour. Its energy payback period and cost payback period were estimated as 2.95 and 1.10 years, respectively, which is very low as compared to its life of 20 years. In the entire lifetime, the CO2 mitigation was found to be 209.21 tons, which proves its suitability.

This investigation aims to present thermo-environmental and thermo-economic parametric studies for a new hybrid tri-generation energy system. In system, a regenerative gas turbine cycle (RGTC) is the runner system, while Kalina cycle (KC) and ejector refrigeration cycle (ERC) are considered as companion elements. The parametric study is done through validated computational program developed in EES software. Two new functions of levelized total annual emissions and costs ( LTAE and LTAC ), with two conventional indices of energetic and exergetic efficiencies ( η en and η ex ) are defined for system evaluation. Thermodynamics modeling revealed that almost 75 % of total exergy destruction is related to the RGTC. The outputs of parametric study prove that pressure ratio of compressor and pinch-point temperature of heat exchanger 2 are the most and least effective parameters, respectively. Also, for the bottoming cycles, changes in KC design parameters resulted in creation of peak points in all the evaluation criteria; but changes in the ERC design parameters resulted in uniform (ascending or descending) behavior in the evaluation criteria. The NSGA-II optimization procedure (using MATLAB software) results in η en , opt = 77.17 %, η ex , opt = 38.94 %, LTAE opt = 9.36 kg/kW.yr, and LTAC opt = 106.04 €/kW.yr. The payback period and net present value of the tri-generation system are found as 3.74 yr and 1184525.43 €.

Massive heat in the exhaust air of cryogenic air separation purification system is wasted in conventional systems. Its intermittent and dynamic characteristics are major constraints to achieve heat recovery. Cascaded latent thermal energy storage (LTES) is considered as a promising solution, but actual application is rarely reported. This paper initially investigates a two-stage LTES tank which is incorporated with a pilot plant of cryogenic air separation purification system, and a test under a real operation condition is performed. The tank contains five heat storage units in high-temperature stage and five units in low-temperature stage, which are loaded with commercial paraffin of melting temperatures 70 °C and 48 °C, respectively. Moreover, heat pipes combined with vertical fins are assembled to increase the heat transfer rate. Results show that 51369.5 kJ heat is saved in a charging-discharging cycle by introducing LTES tank to air separation system. 64.7% of waste heat in the exhaust air could be recovered based on waste heat criterion of 40 °C. Also worth noting that payback period of LTES tank is 2.3 years, and 25784.3 kg CO2 emission is reduced per year. The LTES demonstrates good performance when compared with other reported LTES for industrial application.

With the increasing proportion of renewable energy represented by photovoltaic (PV) and wind power in the grid, the existing grid has faced some new challenges owing to is intermittent and uncontrollable characteristics. It is important to evaluate the impact of PV and wind on the public electricity supply system when they are introduced into the grid. We present a new method to predict the maximum penetration of renewable energy and its impact on the public electricity supply system from both qualitative and quantitative perspectives. Based on the residual load duration curve method, the new method combines a renewables capacity credit analysis indicator and dynamic investment payback period (DIPP) to explain the impacts on the reduction of peak load and renewables curtailment. Real data were used from the power grids of Kyushu, Tokyo, Kansai, and Hokkaido in Japan. The results indicate that the capacity credit increases with an increase in PV and wind shares in the grid. However, it seems to be saturated when the share of PV and wind power in the grid reaches 25% and 60%, respectively. Compared with the wind integration in Kansai and Hokkaido, the PV penetration in Kyushu and Tokyo reaches saturation more rapidly. In addition, PV shows more power suppression, which prolongs its payback period compared to wind energy. The significant difference in the results of capacity credit and DIPP is limited by the characteristics of power demand in mixed regions and the relevance of renewables distribution.

Iron and steel industry is one of the main energy and water consumer globally which produces high amount of waste heat and air pollution. Numerous regulations, agreements and commitments ask the industry to reduce its energy and water consumption further to its environment fingerprints. MIDREX process is one of the leading technology for direct reduction of iron oxide to sponge iron which is dominant in Iran industry with annual capacity of more than 21 million metric tons. So, recovery of waste heat is essential for this industry. In this regard, using Kalina cycle as an efficient method is investigated in terms of thermodynamic study and economically. The results for analysis of a conventional MIDREX plant in Iran with capacity of annual 1.38 Mt of sponge iron shows that more than 2 MW electricity is extractable via Kalina cycle with mixture of ammonia and water. It also reveals that the heat exchanger and condenser are the main causes of exergy destruction of the proposed system with amount of 70%. The sensitivity analysis demonstrates that concentration and pressure at evaporator affect the energy and exergy efficiencies of the system. Changing the flue gas temperature also can be controlled by changing the concentration of the mixture to keep the stability of the net power. The economic investigations represent the long term for payback period for more than 17 years based on the present feed-in-tariff prices for waste heat recovery. For making the proposed system more profitable, technical and policy modifications are considered simultaneously which is associated with payback period of less than 9 years.

In order to limit global warming of 1.5 °C before 2050, the heat pump with waste heat recovery has been acknowledged as an effective technical solution. In this paper, a new kind of centrifugal heat pump system is applied to recover the waste heat from a steel plant for district heating. Two centrifugal compressors with vapor injection and two-cycle parallel connected system configuration are adopted to achieve higher energy efficiency and larger heating capacity. From simulation, the COP is expected to be more than 6 with a temperature rise of above 30 °C. To validate the calculation results, a 10 MW scale (9.5 MW) centrifugal heat pump was installed and tested in Angang Lingshan steel plant of China. With the waste water inlet temperature of 32.5 °C and hot water outlet temperature of 62.5 °C, the tested COP and heating capacity were 6.67 and 9.67 MW, respectively. The heating capacity of the system was greater than the heating load under severe conditions. Environmental and economic analyses of the waste heat recovery system are presented, showing advantages compared to the conventional heating methods. The PER of megawatt compression heat pump is as high as 2.53 and the payback period of this waste heat recovery system is 1.66 years.

Desert areas are the favorable geographical locations for desired solar resource and temperature variations for improving the performance of hybrid photovoltaic-thermoelectric generator (HPV-TEG) systems. Therefore, economic feasibility analysis of HPV-TEG system is carried out under real environment and market conditions for the Atacama Desert, Chile. The thermal, electrical and economic models of HPV-TEG system are developed and analyzed in MATLAB. Five different possible scenarios are considered for economic feasibility based on energy losses, system costs, nominal efficiencies of TEG and photovoltaic module and their contribution in the economic feasibility of HPV-TEG system is identified and payback period for all scenarios is determined at minimum and maximum PV temperatures for Atacama Desert including residential and industrial electricity prices. The results showed that with existing market costs and TEG efficiency, HPV-TEG system could not be economically competitive with photovoltaic system for environmental conditions of the Atacama Desert. However, the calculated levelized cost of energy (LCOE) of the HPV-TEG system is 0.071 USD/kWh which is relatively close to current LCOEs for PV systems in Chilean energy market. Further, LCOE analysis economically quantifies the advantages of HPV-TEG system over PV system and opens the possibility for HPV-TEG systems to be competitive in desert locations.

Power-to-gas system produces synthetic methane through two-step processes: H2 production via water electrolysis and methanation of CO2. The technology valorizes CO2 as a useful commodity from biogas plants. Biogas upgrading technologies have the capacity to capture CO2 and supply it as a source of carbon to methanation processes hence to produce synthetic methane. In this study, we have carried out a techno-economic assessment of biomethane production and estimation of its production costs via the integration of landfill biogas to methanation process. The study assessed four different scenarios, scenario 1: water-scrubbing, scenario 2: membrane, scenario 3: direct methanation and scenario 4: methanation with membrane. Production costs in case of power-to-gas scenarios 3&4 are competitive with standard upgrading scenarios 1&2 for electricity price below 20 €/MWh. Presence of electrolyzer unit contributes to more than 75% of the total biomethane production costs. Scenarios 1&2 are insensitive to changes in electricity prices as well as to operating time, but scenarios 3&4 are extremely sensitive to both electricity prices variation and operating time. Increase in the plant size and vol% of CH4 in raw biogas presented shorter payback period in case of scenarios 1&2 due to lower specific production costs.

[EN] The present study analyses the performance of a heating system controlled by a model predictive control strategy, where the impact of different combinations of thermal energy storage tank volumes and installed PV power capacities are analysed. The novelty of the paper lies in studying both economic and energy impacts of each equipment combination in different locations, buildings, and indoor occupancy schedules. The payback period, the reduction of the electricity grid consumption, and the behaviour of the coefficient of performance of the heat pump are studied in detail for all cases. Results point out that from an economic point of view, to invest in a thermal energy storage tank provides shorter payback periods in comparison to scenarios with PV panels, due to the high price of the solar elements. However, the energy performance analysis highlighted that the use of PV panels contributes to achieve up to 34%, 54%, and 90% of reduction of the electricity grid consumption in Helsinki, Strasbourg, and Athens, respectively. Finally, it is worth noting that the increase of the thermal energy storage volume improves the coefficient of performance of the heat pump., This work was partially funded by the Ministerio de Ciencia, Innovacion y Universidades de Espana (RTI2018-093849-B-C31-MCIU/AEI/FEDER, UE) and the Agencia Estatal de Investigacion (AEI) (RED2018-102431-T) . The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2017 SGR 1537) . GREiA is a certified TECNIO agent in the category of technology developers from the Government of Catalonia. This work is partially supported by ICREA under the ICREA Academia programme. A.L. Pisello's acknowledgements are due to the National Ministry of Research for supporting NEXT.COM project under the framework of PRIN 2017 (cod. 20172FSCH4_002) and the IEA EBC Annex 79 "Occupant-centric building design and operation" for inspiring human-centric research.

The impact of industrial EE projects have previously been understated by the omission of non-energy benefits (NEBs). As a result, several fruitful projects have not been implemented which could have dire consequences for energy intensive industries, such as the mining industry. Typically, project feasibility is determined through financial evaluation techniques such as payback period, internal rate of return and return on investment. These techniques are limited to the monetisation of benefits, NEBs therefore, has to be quantified, monetised and included in these techniques. However, not all NEBs have direct costs, there are NEBs which affects productivity but the relationship cannot be empirically calculated. Therefore, this paper aims to develop a comprehensive financial model that can be used by energy advocates to quantify and monetise NEBs for EE projects in the mining industry.

This research work aims to assess the performance of an innovative exhaust air energy recovery system consisting of a building integrated photovoltaic/thermal (BIPV/T) and a thermal wheel (TW). This BIPV/T-TW system has two main operating modes, namely winter and summer. The exhaust air is used for pre-heating and pre-cooling the ambient fresh air through a TW in the winter and summer modes of operation, respectively. Besides, the pre-heated fresh air (in the winter mode) and the heated exhaust air (in the summer mode) is used for reducing the temperature of PV panels and consequently improving their electrical efficiency. The electrical and thermal performance of the system is calculated and compared with those of the conventional BIPV/T and TW systems. Besides, a performance evaluation criterion (PEC) is defined in this study to investigate the overall performance of the studied systems. The results shows that the BIPV/T-TW system has higher PEC than the BIPV/T and TW systems. Furthermore, the effect of various important parameters on the yearly average PEC of the BIPV/T-TW system is analyzed. The economic assessment of BIPV/T-TW represents that the return time of investment according to simple payback (SP) and net present value (NPV) is a reasonable value.

The wastewater entering the treatment facility has a significant energy content providing sufficient circumstances for the biological processes, but it passes through the system without further utilization and it is released in the receiving water body causing heat pollution. If recovered, the heat could be used for several purposes; this paper addresses the options for using the wastewater excess heat in district heating systems in Hungary. Geographic information system tools were used to determine the distance between heat sources and areas with district heating to show where the excess heat could be used. Five scenarios were created as a function of distance in which the reclaimed heat would be transported to an already existing district heating station. Considering a temperature drop of 2 K, calculation showed that installing the system under 14,000 population equivalents would not be possible. In the other 79 cases, the major factors of return were the distances from the district heating station and the expenditures of the heat pump and pipelines. Under the chosen circumstances only a fraction of the investments (40% for the best scenario) showed return in less than 10 years. In only 12 cases would the payback period be below 5 years. The situation may be improved by increasing the amount of reclaimed heat (68 under 10 years and 22 in 5 years for the same scenario) or case of higher natural gas prices.

Hybrid systems, which use more than one renewable energy sources, are quite advantageous, because they can eliminate or at least vitiate the interrupted characteristics of the renewable sources. In the present study, a hybrid system, which consists of a small scale wind turbine and photovoltaic panels, was focused on. The system supplies the required electricity demand for a detached house, with a 117 m2 area, in five different locations (Izmir, Madrid, Budapest, Paris and Helsinki) according to European climate zones. A detailed dynamic hourly electricity generation analysis for the two components of the hybrid system was performed. As a result, the coverage ratio of the hybrid system electricity generation for the total electricity demand of the house, simple payback time and energy payback time of the system were calculated for each city. The results revealed that yearly electrical energy demand of the house can be entirely met by the evaluated hybrid system for each city. Maximum yearly coverage ratio of 176.6% was observed for Izmir, Turkey, while minimum coverage ratio was 103.1% for Helsinki, Finland. The simple payback time and energy payback time of the hybrid system were determined in the range of 7–25.5 years and 4.6–6.8 years, respectively.

The successful deployment of distributed solar generation in urban areas involves the evaluation of how suitable a building is for installing the rooftop solar photovoltaic (PV) system within a region. When evaluating the rooftop solar PV suitability of a building, it is crucial to consider not only its technical but also its economic performance as the difference in technical performance can lead to different financial returns for rooftop solar PV adopters. Towards this end, this study aimed to propose a method for developing a rooftop solar PV rating system using cluster analysis based on the technical and economic suitability criteria. As a result, a rooftop solar PV rating system was developed for 21,681 buildings in the Gangnam district in Seoul, South Korea by dividing them into four grades according to their rooftop solar PV potential, return on investment, and payback period. The effectiveness of the proposed rating system was validated by comparing it with the rating systems developed using the classification method and suitability criteria from the previous studies. This study has significant contributions in that it can provide the rooftop solar PV suitability information on a grade scale for intuitive decision-making based on scientific evidence and reasonable criteria.

Through various solar assisted heating systems installed worldwide, large industrial scale applications include a very small fraction and further research is still needed in this area. Electrowinning in the copper complex is an industrial scale process that needs thermal energy for electrolyte heating. In this work, for the first time, the techno-economical assessment of using solar energy for this application is performed. Sarcheshmeh copper mine, Kerman, Iran is selected as the case study. System components are modeled and the annual performance is evaluated. To economically optimize the collector arrangement and sizes of storage tank and solar farm, a single-objective as well as a multi-objective genetic algorithm is used. Then, the effects of type and orientation of collector and heat transfer fluid on the system performance are studied. Results demonstrated that a system of 5000–6000 square meters of collectors (depending on the selected collector), facing south, 150–250 cubic meters of stratified storage tank with a height to diameter ratio of three can supply 40–78% of the total heat demanded. This leads to around a 970 tonnes reduction in carbon dioxide emissions each year, which is quite significant, especially in terms of reducing global warming. Payback period varies between 6 and 10 years.

In the present study, an experimental setup for a PVT system is designed and fabricated to investigate the economic and environmental aspects of using different nano-oxides/water fluids. Selected coolant fluids are: pure water, ZnO/water, Al2O3/water and TiO2/water nanofluids. To make nanofluids, nanoparticles are dispersed in distilled water by 0.2% weight fractions (wt%), separately. Based on the experimental results the amount of annual emission reduction and cost saving are investigated for different coolants. Furthermore, the payback period of the PVTs is compared with that of a conventional PV unit. The results are presented in five different scenarios due to increasing of the electricity price, up to the final price and the government subsidies for the renewable energy sources (1st: 10% annual price increasing, with no subsidy, 2nd: linear increasing price, with no subsidy, 3rd: 10% the annual price increasing, 50% subsidy, 4th: linear price increasing, 50% subsidy and 5th: linear price increasing, 75% subsidy). From the energy viewpoint, by using pure water, PVT/TiO2, PVT/ZnO and PVT/Al2O3, the size reduction of the PVT system in comparison with that of the PV is 21, 32, 33 and 24%, respectively, and from the exergy viewpoint these values are about 5, 6, 7, 6%, respectively.