Short Payback Time Research Articles

ROGER: A method for determining the geothermal potential in urban areas

Shallow geothermal energy is increasingly adopted for heating and cooling purposes because of the short pay-back time of initial installation investments. As a result, a relevant concentration of Ground Heat Exchangers is being experienced in urban areas. Planning issues thus arise to manage interferences and optimize the use of underground heat resources without depletion, harm to the environment nor efficiency losses on heat pumps or plant oversizing. This study provides a rational approach to optimise geothermal resources based on the use of Geographic Information Systems and transient 3D Thermo-Hydro numerical models. An optimised semi-analytical formula for the assessment of Borehole Heat Exchangers geothermal potential in hydrodynamic conditions is developed through a parametric numerical study. The long-term performances of BHE subjected to groundwater velocity in the range of 0 to 1 m/day were analysed with multiple aquifer thermal parameters. This analytical expression allows a fast and accurate assessment of the potential even in large areas without leading to excessively conservative evaluations. This may serve designers in the preliminary sizing of installations and city planners in the development of appropriate policies for the promotion and management of shallow geothermal resources. An example of the application to the central district of the city of Turin (Italy) is also shown.

The Optimal Selection of Renewable Energy Systems Based on MILP for Two Zones in Mexico

This paper presents a series of enhancements to a previously proposed mixed-integer linear programming (MILP) model for investment decisions and operational planning in distributed generation (DG) systems. The main contribution of this study consists of integrating a wind generation system and multiple loads at different buses in a network. The model considers dynamic weather data, energy prices, costs related to photovoltaic and wind systems, storage systems, operational and maintenance costs, and other pertinent factors, such as efficiencies, geographical locations, resource availability, and different load profiles. The simulation results obtained through implementation in Julia’s programming language illustrate that the MILP formulation maximizes the net present value, and four configurations for hybrid power generation systems in Mexico are analyzed. The objective is to enable profitability assessment for investments in large-capacity DG systems in two strategic zones of Mexico. The results show that the configurations in the NE zone, especially in Tamaulipas, are the most cost-effective. Case 1 stands out for its highest net present value and shortest payback time, while Case 2 offers the highest energy savings. In addition, Cases 3 and 4, which incorporate storage systems, exhibit the longest payback periods and the lowest savings, indicating less favorable economic performance compared with Cases 1 and 2. Moreover, the sales of two case studies, one without a storage system and the other with a storage system, are shown. The model also incorporates instruments for buying or selling energy in the wholesale electricity market, including variables that depict the injected energy into the electrical grid. This comprehensive approach provides a detailed overview of optimal energy management.

Mathematical modeling and performance evaluations of a wood drying process using photovoltaic thermal and double-pass solar air collectors

This research conducts a novel and complete 4E assessments and introduces an innovative method for examining solar wood drying systems. The software TRNSYS and MATLAB programming are combined to simulate and create a numerical program. This novel combination allows for a thorough examination that goes beyond conventional assessments of wood drying. The aim is to evaluate the effectiveness of a solar wood dryer using two different collectors, a double-pass and a photovoltaic thermal collectors, in terms of four key aspects: energy, exergy, economic, and environmental. Further, the drying process was investigated under various climates in three African cities (Errachidia, Dakar, and Nouakchott). The moisture content of wood was reduced from 74% to 12% in the three cities. Elaborate simulations were performed and the results were confirmed by experimental validation, using methods including Mean Absolute Error, Mean Relative Error, and Root Mean Square Error. The primary findings of this study are the following: In the double-pass dryer, the drying time required in Errachidia, Dakar, and Nouakchott was 139h, 189h, and 170h, respectively. Whereas in the photovoltaic thermal dryer, it needed 192h in Errachidia, 210h in Dakar, and 189h in Nouakchott. Further, using photovoltaic thermal, the dryer exhibited superior exergy efficiency compared to the use of double pass collector. Photovoltaic thermal collector reduces yearly CO2 emissions by an average of 54.87, 66.2, and 44.11 tonnesCO2 in Errachidia, Dakar, and Nouakchott, respectively. In contrast, double pass collector reduces CO2 emissions by an average of 38.49, 57.9, and 38.56 tonnesCO2 in Errachidia, Dakar, and Nouakchott, respectively, throughout the year. Further, the solar dryer, using double pass collector, has a shorter payback time than using photovoltaic thermal collector, indicating a quicker economic return.

Renewable Energy Analysis and Evaluation with Economic Utilization of Solar Powered Air Conditioning System in Nigeria

This article focuses on the analysis and integration of PV systems to load ratio correlation and the economic importance of the left over to grid supply and integration. The paper focusses on the different methods of PV generation to load utilization using the solar powered air conditioner as the load while minimizing the use of fossil fuel (petroleum, natural gas and coal) which have serious environmental implications. Air conditioners are becoming more commonly used load power consumption metrics and are a major strain on energy demands especially in tropical rainforest climate countries like Nigeria. The photovoltaic electricity is a clean and sustainable energy. In this paper, we present a techno-economic feasibility study for solar powered air conditioning system in Nigeria. The method used made a correlation of four alternatives of PV to load ratio factor being investigated. In the first instance, the PV system supplied 50% of the energy to the loads. In the second method, the PV system supplied 75% of the energy to the loads. Thirdly, the PV system supplied 100% of the energy to the loads. Fourthly, on a final design, the PV system supplied 125% of the energy to the loads. In the first two case the PV energy generated is used solely to power the air conditioner system. In the last two design, there is excess electrical energy which is proposed to be sold to the Nigeria grid system especially if the grid system optimized and broken down into smaller grid array within 0.3$ feed-in tariff. The best alternative method is the grid-connected PV system with 125% capacity factor which is chosen due to its short payback time period as well as high profit rate over the lifetime of the project.

Kinetics of Charge Transfer at Carbon-Based Counter Electrodes for Dye-Sensitized Solar Cells with Aqueous Electrolytes

Dye-sensitized solar cells (DSSCs) might provide a highly sustainable alternative for next generation photovoltaics. This is due to their low-energy production from abundant materials, short energy payback time, high efficiency under low illumination intensities (i.e., diffuse light or indoor conditions), and versatile concepts of applications. However, some commonly used electrolyte components are environmentally problematic. Acetonitrile or other volatile organic solvents, e.g., as well as carcinogenic cobalt complexes should not leak from DSSCs. Sealing foils, however, which are typically used to prevent such leakage, carry a risk of long-term failure.Replacing the organic solvent by water offers several advantages, as it is environmentally benign, less volatile and the cell function, further, cannot be damaged by the intrusion of water vapor. Instead of Co-complexes, e.g., the stable organic radical TEMPO (2,2,6,6-tretramethylpiperidine-1-oxyl) can serve as an alternative redox mediator with a highly positive redox potential (0.71 V vs. NHE). Using TEMPO, power conversion efficiencies (PCE) of up to 4.3% and high open-circuit voltages (V oc = 0.955 V) have been reported.[1] However, the use of TEMPO is limited by its solubility in water (C max < 0.15 M). Its derivative 4-hydroxy-TEMPO (OH-TEMPO) possesses a significantly higher solubility in water (C max > 2 M) and a more positive redox potential (0.81 V vs. NHE), making it a promising candidate as a redox mediator.In this work, we built DSSCs with TEMPO and OH-TEMPO based aqueous electrolytes, Y123-sensitized TiO2 photoanodes, and counter electrodes coated with poly(3,4-ethylenedioxythiphene) (PEDOT). For OH-TEMPO, the short-circuit current density (j sc) and open-circuit voltage were higher than with TEMPO, but the fill factor (FF) and the PCE were significantly lower. By impedance studies, large charge transfer resistances at the counter electrode (R CE) were obtained for OH-TEMPO in combination with additives such as 1-methylbenzimidazole (MBI), indicating a strong kinetic limitation of the OH-TEMPO+ reduction. However, we found that such additives as MBI or other organic compounds, are necessary to suppress recombination at the photoanode/electrolyte interface. Thus, we subsequently studied different counter electrode materials, such as platinum (reference), conducting polymers, and carbon materials, in contact to OH-TEMPO electrolytes with MBI to determine R CE and find suitable materials for the application in DSSCs.[1] Yang, W., Söderberg, M., Eriksson, A. I. K. & Boschloo, G. Efficient aqueous dye-sensitized solar cell electrolytes based on a TEMPO/TEMPO+ redox couple. RSC Advances 5, 26706–26709 (2015).

Use of a residential building’s foundation as Energy Geo-Structures: A case study in the Mediterranean environment

Geothermal energy, a type of renewable energy obtained from the Earth, can be used by Ground Source Heat Pumps (GSHPs) for space heating and cooling. GSHP systems extract/reject heat from/into the earth via a network of pipes or tubes known as Ground Heat Exchangers (GHEs),. GHEs can be horizontal or vertical and come in a variety of forms, including slinky loops and vertical spiral loops for horizontal configurations, and single U-tube, double U-tube in series or parallel, coaxial pipe, and spiral/helical pipe for vertical configurations. Although GSHPs exhibit a higher performance than conventional Air Source Heat Pumps (ASHPs), the systems are less appealing as investments due to their longer payback times and greater upfront costs. A competent design of the GSHP system with the appropriate GHE sizing, including the case of employing the GHEs in the structures foundations, can minimize the initial cost. Such structures are referred to as Thermo-Active Structure systems or Energy Geo-Structures (EGS), which have already found applications as energy piles, barrette piles, diaphragm walls, shallow foundations, retaining walls, embankments, and tunnel linings [1, 2, 3].&#x0D; Residential buildings in Cyprus have a higher cooling than heating demand, with an extended payback period for the investment, especially if the system is solely utilized for heating [4]. EGS coupled with a GSHP could offer a substitute to reduce the system’s initial expenses and make it more attractive as an investment. EGS have not yet seen applications in Cyprus, therefore an initial computational analysis utilizing the COMSOL software and relevant data is taken into consideration. To determine the heating and cooling loads, a three-bedroom, two-storey house with a total floor space of 190 m2, with nearly Zero Energy Building (nZEB) characteristics, is used as the typical case for a single detached residential building in Cyprus. The TRNSYS software was used to calculate the heating and cooling loads. In order to analyze the rejected/absorbed energy from the earth, typical foundations were constructed as full sized models in COMSOL (Figure 1). With the exception of pipes, where a 1D solution is employed, the convection diffusion equation for heat transfer is utilized with 3D conservation of heat transfer for an incompressible fluid. A detailed methodology can be found in Aresti et al. [5].&#x0D; For the COMSOL compuations, the site ground temperature characteristics and the local ambient temperature were taken into account. Based on the provided loads, the inlet and outlet temperatures were hourly calculated for the highest demand months: February for winter – heating, and July for summer – cooling.&#x0D; To assess the potential of using the foundation bed as an alternative to energy piles, a comparison on the performance of the two cases is presented in Figure 2 for both summer and winter conditions. The foundation bed is seen to work in a steady manner, which is highly desired in a system. However, it performs less well, with a lower COP than the energy piles system, which exhibits greater COP values than the foundation bed system both in winter and summer. It remains that both systems exhibit high enough COPs and nearly steady conditions. The COPs vary between 4.4 and 4.8. A yearly simulation (not shown here) yielded a lowest COP value of 4.5.&#x0D; The systems were also assessed economically by being compared to a convectional ASHP system. The economic study demonstrated that the suggested foundation systems had relatively short payback times, making them a plausible alternative. More detailed discussion on the results can be found in Aresti et al. [5]. As a future objective, an environmental and Life Cycle Analysis investigation, similar to the one performed by Aresti et al. [6], could provide a deeper insight of the plausibility of using the building foundation as EGS.

Digital Twin Modeling of Flexible Perovskite Nano-Films with In-Situ Mechanical Microscopy Validation.

Flexible perovskite solar cells introduce opportunities for high throughput, high specific weight, and short energy payback time photovoltaics. However, they require additional investigation into their mechanical resiliency. This work investigates the mechanical properties and behaviors of perovskite thin films and builds a robust model for future research. A two-pronged approach was utilized. Perovskite thin films were flexed in a three-point bend mode with in-situ SEM. Novel insights into the perovskite mechanical behaviors with varying substrate layers were gained. Modeling and validation, the second prong, was completed with finite element analysis. Model coupons of the imaged perovskite architectures were built, with sensitivity analysis completed to provide mechanical property estimates. The results demonstrate that mechanical degradation of perovskite thin films on polyethylene terephthalate (PET) primarily presents as a crack in the grain boundaries between crystals. Perovskite thin films on Indium Tin Oxide (ITO) and PET primarily crack in a periodic pattern regardless of the placement of perovskite crystals.

Rapid Thermal Processing of Kesterite Thin Films

Multinary chalcogenides with Kesterite structure Cu2ZnSn(S,Se)4 (CZTSSe) are a prospective material base for the enhancement of the photovoltaics industry with abundant and environmentally friendly constituents and appropriate electro-physical properties for building highly efficient devices at a low cost with a short energy pay-back time. The actual record efficiency of 13.6%, which was reached recently, is far below the current isostructural chalcopyrite’s solar cells efficiency of near 24%. The main problems for future improvements are the defects in and stability of the Kesterite absorber itself and recombination losses at interfaces at the buffer and back contacts. Here, we present an investigation into the rapid thermal annealing (RTA) of as-electrodeposited thin films of Cu2ZnSnS4 (CZTS). The treatment was carried out in a cold wall tubular reactor in dynamic conditions with variations in the temperature, speed and time of the specific elements of the process. The effect of annealing was investigated by X-ray diffractometry, Raman scattering and Scanning Electron Microscopy (SEM). The phase composition of the films depending on treatment conditions was analyzed, showing that, in a slow, prolonged, high-temperature process, the low-temperature binaries react completely and only Kesterite and ZnS are left. In addition, structural investigations by XRD have shown a gradual decrease in crystallite sizes when the temperature level and duration of the high-temperature segment increases, and respectively increase in the strain due to the formation of the phases in non-equilibrium conditions. However, when the speed of dynamic segments in the process decreases, both the crystallite size and strain of the Kesterite non-monotonically decrease. The grain sizes of Kesterite, presented by SEM investigations, have been shown to increase when the temperature and the duration increase, while the speed decreases, except at higher temperatures of near 750 °C. The set of experiments, following a scrupulous analysis of Raman data, were shown to have the potential to elucidate a way to ensure the fine manipulation of the substitutional Cu/Zn defects in the structure of CZTS thin films, considering the dependences of the ratios of Q = I287/I303 and Q′ = I338/(I366 + I374) on the process variables. Qualitatively, it can be concluded that increases in the speed, duration and temperature of RTA lead to increases in the order of the structure, whereas, at higher temperatures of near 750 °C, these factors decrease.

Energetic, exergetic, environmental and economic (4E) analysis of a direct-expansion solar-assisted heat pump with low GWP refrigerant

The main objective of this study was to develop, validate and apply a mathematical model for analysing the performance of a Direct-Expansion Solar-Assisted Heat Pump (DX-SAHP) based on the energetic, exergetic, environmental, and economic (4E) analysis. The DX-SAHP produces domestic hot water using the low-global-warming-potential (GWP) refrigerant R290 which is the best candidate for energy, environmental, and logistical performance among six previously evaluated candidates (R152a, R744, R1234yf, R1234ze(E), R170, R290). Environmental and economic analysis are founded, respectively, on Total Equivalent Warming Impact (TEWI) and payback. The proposed model was validated using an experimental test bench developed for this study. Using the validated model, simulations were conducted to investigate the influence of geometric parameters (evaporator area and condenser length) on the system's performance. The results show that increasing the evaporator area yields the greatest increase in COP (117 and 80.4%) and the greatest decrease in TEWI (53.8 and 44.5%) for final water temperatures of 45 and 65°C, respectively. However, this also leads to a drop in collector efficiency (58.7 and 60.8%) but results in a shorter payback time (6.06 and 3.87 years) for final water temperatures of 45 and 65°C, respectively. The greatest increase in exergy efficiency (11.5 and 14.1%) occurs with an increase in condenser length for final water temperatures of 45 and 65°C, respectively.

Factors influence analysis and life cycle assessment of innovative bifacial photovoltaic applied on building facade

Bifacial PV (BPV) could use both radiation on the front and back for power generation. The challenge is that reflected radiation absorbed by the back is limited when BPV is applied on building. BPV cannot be effectively utilized. In this research, BPV was innovatively combined with reflective film to form BPV curtain wall system, which is conducive to higher power output and could be applied to the facade of building directly. Compared with mono-facial PV, power generation of the system could be increased by 24% on average. Life cycle assessment (LCA) was used to analyze the influence of multi-factors on this system, which makes the evaluation of the performance more comprehensive. It could be found that the energy and greenhouse gas payback time could reach the shortest when the system is faced South. The results of the system become better with the increase of photovoltaic coverage, but this trend will gradually slow down when the coverage is greater than 75%. Besides, when the distance with reflective layer is about 1/12 L, the system has the shortest payback time. This research explored a new form of BPV system, and has beneficial effect on the field of application of BPV in buildings.

Techno-economic evaluation of supercritical fluid extraction of flaxseed oil

Green and promising technologies are current interests of the developing societies. Advantages of supercritical fluid extraction (SFE) overcome traditional extraction processes due to the quality aspects and environmental benefits. However, the relative high cost of the system makes these technologies commercial applicability in question for some products species. In our study, we intended to investigate the SFE of flaxseed oil in pilot scale system. Techno-economic analyses of SFE of flaxseed oil was evaluated using computational simulation software. The results demonstrated that high scales of SFE systems are feasible due to the high productivity. Although high investment is necessary for high-capacity extraction systems, low Cost of Manufacturing (COM) and short payback time can be accomplished.

Economic Assessment of Polypropylene Waste (PP) Pyrolysis in Circular Economy and Industrial Symbiosis

Plastic waste has a high energy content and can be utilized as an energy source. This study aims to assess the economic feasibility of polypropylene plastic waste (PP) pyrolysis. A literature review was carried out to determine the optimal pyrolysis conditions for oil production. The preferred pyrolysis temperature ranges from 450 °C to 550 °C, where the oil yields vary from 82 wt.% to 92.3 wt.%. Two scenarios were studied. In the first scenario, pyrolysis gas is used for the pyrolysis heating needs, whereas in the second scenario, natural gas is used. An overview of the economic performance of a pyrolysis plant with a capacity of 200,000 t/year is presented. Based on the results, the plant is economically viable, as it presents high profits and a short payback time for both scenarios considered. Although the annual revenues are smaller in scenario 1, the significant reduction in operating costs makes this scenario preferable. The annual profits amount to 37.3 M€, while the return on investment is 81% and the payback time is 1.16 years. In scenario 2, although the plant is still feasible and shows high profitability, the annual profits are lower by about 1.5 M€, while the payback time is 1.2 years.

Evaluations of energy upgrading interventions in social housing neighbourhoods in Greece: An approach that takes into account residents’ views

The European Union (EU) has committed to actions aimed at the energy efficiency of buildings, with a focus on the domestic sector. Most residential buildings in Greece are classified in the lowest energy categories, while the government attempts to upgrade them energy wise, through state subsidy programs. This study aims to evaluate the energy upgrading interventions in social housing areas, built in the capital of Greece, Athens. For this purpose, energy audits are performed in social housing in three different neighborhoods, in order to find the current building stock and later suggest energy upgrading solutions. The study is followed by a questionnaire survey to citizens of the neighborhoods under study. The majority of respondents consider significantly beneficial the energy-saving upgrade programs that the Greek Government has run in recent years, as they demand to be easier for everyone to participate. At the same time, respondents seem to be positive for future energy upgrade interventions, such as external insulation, frame replacement and implementation of renewable energy systems. Through the implementation of energy upgrade scenarios in the official national software for energy audits (TEE KENAK), results show that dwellings can upgrade up to 7 energy categories, with short payback time, reducing CO2 and primary energy emissions.

Effects of shape-stabilized phase change materials in cementitious composites on thermal-mechanical properties and economic benefits

• The effects of PCMs to save building energy consumption was investigated. • Physical-thermal-mechanical testing and cost analysis were conducted. • Energy saving efficiency was calculated via computational modeling. • Findings infer the potential application of coconut oil as an engineered PCM. Phase change materials (PCMs) have been utilized to improve the thermal properties of cementitious composites by using their latent heat capacity. Applying them to building components can reduce their heating and cooling loads through energy absorption during the phase change period. The shape-stabilized method using porous lightweight aggregates can prevent PCM leakage during the phase transition process. While many attempts have been made to develop and improve shape-stabilized PCM composites to achieve a high level of energy savings, their economic benefits have not been fully investigated, as most analyses are based on initial material costs with a limited linkage of their thermal-mechanical properties. This study used an integrated experimental-computational method to evaluate the effects of different PCMs in building components by considering the core thermal-mechanical properties with an economic benefit analysis. Toward that end, two different PCMs (PureTemp® and coconut oil) were selected to fabricate Thermal Energy Storage Aggregates (TESA) using the vacuum impregnated method: TESA-P (with PureTemp®) and TESA-C (with coconut oil). The thermal-mechanical properties were experimentally determined and used for building energy simulation for a typical small office in Houston, Texas. The cementitious composites incorporated with PCM showed lower thermal conductivity and heat transfer than the non-PCM specimens. The TESA-P specimens showed a more prolonged time lag and better energy-saving performance than the TESA-C specimens due to better thermal properties of PCM itself. In contrast, the costs of TESA-C applications could be less with a shorter pay-back time. The findings of this study infer the potential application of coconut oil as an engineered PCM in building construction.

A thermal performance-enhancing strategy of photovoltaic thermal systems by applying surface area partially covered by solar cells

In this work, a single unit called photovoltaic thermal with solar thermal collector enhancer has been developed, whose absorber plate is partially covered by photovoltaic cells. This design increases the photothermal energy conversion ratio and absorbed energy by the system, resulting in a higher thermal power, thermal exergy, and outflow temperature compared to a conventional photovoltaic thermal module. This research examines the impacts of different glazing arrangements on the system performance using a three-dimensional transient model to determine the most efficient design from energy and exergy viewpoints. Moreover, the effects of various parameters on system performance, such as tilt angle, azimuth angle, mass flow rate, and dust accumulation on the system surface, are discussed. Finally, a comparative study between the proposed system, the standalone solar thermal collector, and the standalone photovoltaic thermal system is carried out in terms of energy, exergy, and economics. Results indicate that the proposed system has 31.24 % greater overall power and 35.07 % shorter payback time than a conventional standalone unglazed photovoltaic thermal system when only its solar collector enhancer part is covered by glass.

Techno-economic analysis of evaporative cooling enhancement methods of a 21 MW air-cooled geothermal power plant

Ambient temperature is a critical parameter for the performance of binary-type geothermal power plants with air-cooled condensers. Significant losses occur in this type of geothermal power plant's performance during summer. In this study, direct spray, ecomesh, and wetted media evaporative cooling techniques have been proposed, and they are analyzed from thermodynamics and economic perspectives for cooling the inlet air of the air-cooled condenser of an existing geothermal power plant. The results indicated that the investigated evaporative cooling methods could cause a notable increase in power plant performance. The study's findings show that wetted media, ecomesh, and direct spray systems could increase the power generation of the power plant by 4.6%, 3.8%, and 2.9% on an annual basis, respectively. Besides, the economic analysis results demonstrated that direct spray, ecomesh, and wetted media systems in the studied power plant yield an internal rate of return values of 19.85%, 14.40%, and 11.00%, respectively. Conversely, the payback period is 10.08, 13.7, and 17.5 years for direct and ecomesh spray systems and a wetted media system, respectively. Therefore, the direct spray evaporative cooling method can have a nearly 43% shorter payback time than a wetted media system for the investors. Consequently, geothermal power plants with air-cooled condensers should be investigated for possible alternative evaporative cooling systems to diminish the negative effect of ambient temperature on power generation capacities during warm days of the years to meet United Nation's Sustainable Development Goal #7 and mainly target 7.1, 7.2, and 7.3.

Energy, exergy and economic analysis of an air cavity appended passive solar still of different basin material at varying depth

Developing countries are severely affected by water scarcity. To meet the growing demand for clean drinking water, minimal, small-scale methods that don't use much energy are needed. Saline water desalination utilising the solar still, which depends only on solar radiation, is a realistic option for rural coastal communities. The current research focuses on increasing the daily production of solar still distillate yield. This paper provides a modified design that incorporates an air cavity connected to a solar still absorber plate and an effort to calculate the solar stills technological and economic assessment. The current study extensively focuses on the usefulness of an air cavity in improving solar still performance under diverse climatic conditions. The experimentation was performed at varying depths of saline water in two different material solar stills. During the experimentation, the maximum saline water temperature observed was 89°C and the lowest temperature was found as 29 °C. Aluminium and polycarbonate stills had an average energy and exergy efficiency of 48.8 %, 3.44 %, and 42.4 %, 2.3 %, respectively. The daily yields for aluminium and polycarbonate stills were 2.8 to 3.8 l/m2/day and 1.8 to 3.4 l/m2/day, respectively. The cost per litre of the distillate from aluminium and polycarbonate stills was determined to be Rs. 0.723 and Rs. 1.361, respectively, with a payback time of 10 and 11 months. Overall, at 1.8 cm saline water depth, the aluminium still provides improved distillate yield than the polycarbonate still, and the addition of air cavity reprises in the improvement of the efficiency of the solar still. From the experimental findings of both the solar stills, we can conclude that they are long-term viable and cost-effective in producing more distillate than expected with a short payback time.

Process design and techno-economic analysis of fuel ethanol production from food waste by enzymatic hydrolysis and fermentation

In this study, fuel ethanol production from food waste using enzymatic hydrolysis and fermentation was evaluated from techno-economic viewpoint. The plant was designed with a capacity of 10 t/d food waste and a lifetime of 15-year. The total capital cost, annual operation cost and annual net profits of the plant were US$ 367,552, US$ 155,959 and US$ 74,995.57, respectively. The plant was economically viable as long as the internal rate of return remained below 29.8%. The shortest payback time was 5 years with discount rate of 5%. The price of fuel ethanol and food waste treatment fee were the most important variables for the economic performance of the plant by sensitivity analysis. This work could provide the basic knowledge for techno-economic analysis of food waste treatment and promote the industrial production of fuel ethanol.

Techno-economic analysis of Cellulase Production by Trichoderma reesei in Submerged Fermentation Processes using a Process Simulator

Enzymes are valuable in many biofuels production processes, and their wide application has generated significant market demand in recent years. To develop lignocellulosic fuels in a biorefinery, high cost and low catalytic efficiency of cellulase are a major obstacle in the industrial use of this enzyme. A techno-economic assessment of cellulase production by Trichoderma reesei in submerged fermentation (SmF) processes was carried out in this study. SuperPro Designer Software was used to develop a process model that estimated the economic analysis of the fermentation processes by creating alternative schemes (batch and fed-batch) to improve the process. Sensitivity analysis study was carried out using Monte Carlo Software. Economic profitability indicators were used to assess cellulase yield, productivity, aeration rate, and specific power input on the unit production cost (UPC) of cellulase enzyme. Results show that the batch process had a higher aeration requirement when compared to the fed-batch process. Fed-batch process route had a shorter payback time (1.88 years), higher internal rate of return IRR (36.95%), and a more positive Net present value ($140,328,000) than the batch process. In addition, the Fed-batch process route is more economically viable than the batch process route, since the certainty of achieving its base case value of UPC is at the optimum. This study has been able to design a process route that reduces the production cost of cellulase, while increasing its availability in the market for sustainable fuel production in a biorefinery.

Technology selection for capturing CO2 from wood pyrolysis

Emerging negative emission technologies (NETs) are considered as effective measures to reduce carbon dioxide emissions to achieve the climate goal set by the Paris Agreement, and bioenergy with carbon capture and storage (BECCS) is one of the most important NETs. Integrating CO2 capture with biomass pyrolysis (PyrCC) is attracting increasing interest, because biomass pyrolysis has been widely used to produce biooil to replace fossil fuel for decarbonizing the transport sector. In order to provide guidance to the selection of CO2 capture technologies, this paper evaluated the technical and economic performances of PyrCC when different CO2 capture technologies are integrated, including monoethanolamine-based chemical absorption (MEA-CA), temperature swing absorption (TSA), calcium looping (CaL), and chemical looping combustion (CLC). Generally speaking, CLC can realize the highest capture amount of CO2 with the lowest energy penalty. Meanwhile, CLC and CaL show the lowest levelized cost of CO2 (LCOC), which are around 56$/tCO2; and on the contrary MEA-CA shows the highest one of 83$/tCO2. In addition, the key process parameter of pyrolysis, reaction time, has clear effects on the performance of CO2 capture as the longer reaction time leads to an increased amount of captured CO2 and reduced energy penalty. As a result, when the reaction time increases, the LCOCs of all assessed technologies decrease. Moreover, the net present value and the payback time are also estimated for different technologies. At the carbon price of 70.1$/tCO2, MEA-CA and CLC show the longest and shortest payback time that are 5.9 years and 3.2 years respectively.