Payback Time Research Articles

Sustainability assessment of rooftop solar photovoltaic systems: A case study

The study combined conventional life cycle assessment (LCA) with energy benefit and economic feasibility analysis for a 1 MW rooftop solar photovoltaic (PV) system. The study analyzed two solar PV system scenarios: in Case 1, the solar PV system was connected directly to the college's internal grid, while in Case 2, it was integrated with a battery storage system. The environmental impact was assessed in terms of global warming (GWp) and other impact indicators using the ReCiPe (H) midpoint and endpoint methodology. The study found a 73% increase in GWp, a 739% increase in mineral resource scarcity, and an increase in all toxicity indicators observed in Case 2, primarily due to battery utilization. Endpoint impact indicators also increased, affecting human health, ecosystems, and resources. The study also evaluated the energy benefits using energy payback time (EPBT) and energy return on investment (EROI), as well as the economic feasibility using the levelized cost of electricity (LCOE). The EPBT increased from 3.71 years in Case 1 to 6.74 years in Case 2, while the EROI decreased from 5.38 in Case 1 to 2.96 in Case 2, indicating a reduced energy feasibility with the battery storage system. Additionally, the LCOE increased from 3.17 Rs/kWh to 16.96 Rs/kWh in Case 2, primarily due to the high cost of the battery and its replacement. This study shows that converting solar power to firm power in the current scenario has a higher environmental, energy, and economic impact.

Contemporary roof pattern for energy efficient buildings: Air conditioning cost alleviation, CO2 emission mitigation potential and acceptable payback period

Buildings account for a significant portion of global energy use and consumption. Buildings have substantial energy consumption due to the use of heating, ventilation, and cooling systems. It is evident that the use of insulation materials and phase change materials (PCMs) in the design of buildings can effectively reduce the cost of air conditioning by reducing external heat gains and losses. Additionally, the use of environmentally friendly, cost-effective, and natural materials can be beneficial from an environmental standpoint. This paper aims to evaluate the potential for cost savings in the air conditioning of various PCMs and insulation-stuffed building roof configurations. In that respect, four types of phase change materials (HS29, HS36, FS42, and FS30) and four insulation materials (Therma cork, sawdust, aerogel, and sheep wool) were selected. The thermophysical properties of PCMs (solid and liquid state), insulation materials, and building elements were determined experimentally as per ASTM D 5334 standards. Ten various building roof models (contemporary roof pattern) are studied with four various PCMs and four various insulations. In addition, novel building roof design integrated with PCM/insulation were analysed numerically, related to environmental conditions that refer to two different scenarios in India (hot dry and composite climates). It further analyses the reduction in greenhouse gas emissions associated with different roof configurations. The aforementioned PCM/insulation materials were stuffed in the void spaces of the contemporary roof pattern. Thermo-economic analysis of novel roof design with PCM/insulation materials on air-conditioning costs, carbon dioxide emissions and payback time are compared with conventional roofs (CR) and contemporary roof patterns (CRP). The thermo-economic analysis was carried out based on the number of degree-hours of heating and cooling to determine the building's annual energy usage. HS29 PCM stuffed roof pattern (HS29RP) saved the highest total energy cost savings of 11.89/14.71 $/m2/year when compared with conventional roof and 11.35/13.89 $/m2/year compared with contemporary roof pattern for Jabalpur/Kota climatic conditions. HS29 PCM stuffed roof pattern (HS29RP) exhibits the maximum carbon emission mitigation of 215.32/275.37 kg/kWh when compared with conventional roof and 204.95/259.57 kg/kWh for climatic conditions of Jabalpur/Kota. While considering shortest payback span, sawdust stuffed roof pattern shows the minimum payback period of 0.69 and 2.15 years when compared with conventional roof and contemporary roof pattern. The findings of this research offer significant contributions to the development of energy-efficient building envelopes applicable to a wider range of buildings, including those with and without air conditioning systems.

Optimal energy concept for decarbonisation of sea-buckthorn processing plants

The decarbonisation of the industrial sector is required to achieve the objectives defined within the European Climate and Energy framework, since industry accounts for 37% of the total global energy consumption and for a quarter of global energy system CO2 emissions [1]. In this context, this work aims the decarbonisation of a sea-buckthorn processing plant using structural and operational optimisation for the analysis of proposed energy supply concepts based on the integration of renewable energy sources, energy conversion components and storage systems. Different configurations are evaluated to select the concept that leads to a minimisation of the operating costs and a CO2 emissions reduction of the industrial site with installation costs within the investment range defined and the minimum payback period. Thus, the selected decarbonisation concept is able to achieve a reduction of 25% in operation costs (OPEX) and 31% in CO2 with an investment (CAPEX) of 288.7 T€ and a payback time of 5.8 years. Additionally, the developed methodology can be used for the analysis of decarbonisation concepts for other industrial processes by the integration of an adapted techno- economic definition of the components for each energy concept proposed.

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.

Spatially-explicit land use change emissions and carbon payback times of biofuels under the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA)

The Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) requires airlines to offset their greenhouse gas (GHG) emissions above 2019 levels by either buying carbon offsets or using Sustainable Aviation Fuels (SAFs). These are drop-in jet fuels made from biomass or other renewable resources that reduce GHG emissions by at least 10 % compared to kerosene and meet certain sustainability criteria. This study assesses the direct land use change (DLUC) emissions of SAF, i.e., GHG emissions from on-site land conversion from previous uses (excluding primary forests, peatlands, wetlands, and protected and biodiversity-rich areas) into alternative feedstocks, considering spatial variability in global yields and land carbon stocks. The results provide DLUC values and carbon payback times at 0.5-degree resolution for six SAF pathways, with and without irrigation and a medium-input intensity, according to CORSIA sustainability criteria. When excluding CORSIA non-compliant areas, soybean SAF shows the highest mean DLUC factor (31.9 ± 20.7 gCO2/MJ), followed by reed canary grass and maize. Jatropha SAF shows the lowest mean DLUC factor (3.6 ± 31.4 gCO2/MJ), followed by miscanthus and switchgrass. The latter feedstocks show potential for reducing GHG emissions over large areas but with relatively greater variability. Country-average DLUC values are higher than accepted ILUC ones for all pathways except for maize. To ensure the GHG benefits of CORSIA, feedstocks must be produced in areas where not only carbon stocks are relatively low but also where attainable yields are sufficiently high. The results help identify locations where the combination of these two factors may be favourable for low-DLUC SAF production. Irrigated miscanthus offers the highest SAF production potential (2.75 EJ globally) if grown on CORSIA-compliant cropland and grassland areas, accounting for ∼1/5 of the total kerosene used in 2019. Quantifying other environmental impacts of SAFs is desirable to understand sustainability trade-offs and financial constraints that may further limit production potentials.

An Industrial Perspective for Sustainable Polypropylene Plastic Waste Management via Catalytic Pyrolysis—A Technical Report

Recycling plastics on an industrial scale is a key approach to the circular economy. This study presents a techno-economic analysis aimed at recycling polypropylene waste, one of the main consumer plastics. Specifically, it evaluates the technical and economic feasibility of achieving a large-scale cracking process that converts polypropylene waste into an alternative fuel. Pyrolysis is considered as a promising technique to convert plastic waste into liquid oil and other value-added products, with a dual benefit of recovering resources and providing a zero-waste solution. This study concerns a fast catalytic pyrolysis in a fluidized bed reactor, with the presence of a fluid catalytic cracking catalyst of low acidity for high heat transmission, for an industrial plant with a capacity of 1 t/h of polypropylene waste provided by the Greek Petroleum Industry. From the international literature, the operational conditions were chosen pyrolysis temperature at 430 °C, pressure at 1atm, heating rate at 5 °C/min, and yields of products to 71, 14, and 15 wt.%, for liquid fuel, gas, solid product, respectively. The plant design includes a series of apparatuses, with the main one to be the pyrolyzer. The catalytic method is selected over the non-catalytic because the presence of catalyst increases the quantity and quality of the liquid product, which is the main product of the plant. The energy loops of recycling pyrolysis gas and char as a low-carbon fuel in the plant were considered. The production cost, annual revenue, for 2023, are anticipated to reach €13.7 million (115 €/t) and €15 million (15 €/t), respectively, with an estimated investment equal to €5.3 million. The Payback Time is estimated to 2.4 years to recover the cost of investment. The endeavor is rather economically sustainable. A critical parameter for large scale systems is securing feedstock with low or negligible price.

Are alpine floatovoltaics the way forward? Life-cycle environmental impacts and energy payback time of the worlds’ first high-altitude floating solar power plant

Floating photovoltaics (FPV) and high-altitude PV installations are increasingly gaining importance in the sustainable energy sector, each technology holding its own potential. A pioneering high-altitude FPV installation in Switzerland represents the first implementation of combining the two technologies. In order to determine the environmental performance of such an installation, the present study examines the life-cycle environmental impact of the world’s first high-altitude FPV system, using Life Cycle Assessment (LCA). Our results record life-cycle greenhouse gas emissions of 94 g of CO2–eq per kWh of electricity produced by the high-altitude FPV system. The non-renewable primary energy demand amounts to 10′810kWh oil-eq/kWp, which equals an energy payback time of 2.8 years. Environmental hotspots in the life cycle of the installation were found to be the production of the PV panels, due to the wafer production, and the mounting system, dominated by the production processes of the aluminium. Comparison to other PV installations identifies the mounting system as the main point of issue in the high-altitude FPV installation, due to a more intensive aluminium use. It was found that the high-altitude FPV installation can generally compete with alternative PV systems in the lowland, with its environmental impacts lying in the range of −45 % and + 15 %, while being largely outperformed by ground-mounted PV installations at high altitude. By implementing measures such as transitioning to renewable energies in the PV panel and mounting system supply chains, as well as reducing aluminium use for the mounting system, FPV systems hold great potential to help meet the increasingly growing demand of renewable energy sources.

Energetic and exergetic analysis of jet impingement solar thermal collector featuring discrete multi-arc shaped ribs absorber surface

This study analytically examines the thermal, effective, and exergetic efficiency of a jet impingement solar thermal collector (JISTC) roughened with discrete multi-arc-shaped ribs (DMASRs). To accurately estimate the energy usage of the JISTC, these efficiencies are assessed using a parametric design and the temperature rise parameter. A numerical model of the thermal, effective, and exergy analyses of the STC is presented to examine its impacts on each design variable. Optimized parameters increase exergetic efficiency (ηexergetic) by 2.77 times over smooth plates. A multi-objective optimization of the JISTC roughened with DMASRs is carried out. Effective and exergetic efficiency are used as objective functions to find Pareto front optimal solutions. Additionally, an economic, enviroeconomic, exergoeconomic, and energy payback time (EPBT) examination of the JISTC is presented in this investigation. According to the economic evaluation of the JISTC system, the energy cost is found to be 0.08 $/kWh and the exergoeconomic parameter (Rg,ex) is computed to be 0.26 kW h/$. The enviroeconomic analysis findings suggest that the JISTC can reduce approximately 51.15 tons of CO2 emissions per year. The energy payback time based on energy streams ((EPBT)en) is determined to be 0.34 years, while the energy payback time based on exergy streams ((EPBT)ex) is found to be 14.9 years.

Aqueous extracts of composted oil refinery sludge and their possible environmental impacts

ABSTRACT Oil refinery sludge (ORS) management is a global concern, yet information on its low-cost biotransformation possibility is fairly limited. We present a novel approach for ORS mitigation by Eisenia fetida and Eudrilus eugeniae and aerobic composting (AC) in producing clean aqueous extracts (compost teas). Detailed physicochemical characterization, phytotoxicity assays, economic feasibility comparisons, and mathematical equation-based environmental and human health hazard prediction studies were done for all the earthworm and non-earthworm processed compost teas. The E. eugeniae-compost tea reduced Cr, Pb, Cu, Cd, and Zn contents by 52.7, 61.2, 41.8, 80, and 93.8%, respectively. The earthworm-sourced teas showed lower ecological risk (<300) than their aerobic counterparts. Seed germination in Pisum sativum and Cicer arietinum was 2–2.5 folds higher with vermi-derived tea application. Economic assessments illustrated the superiority of E. eugeniae-based biotransformation with higher cash flow and a lower payback time of 1.53 years. The mathematical predictions on human health showed no alarming status for any of the vermi/aerobic compost teas. Overall results implied that vermicomposting is safer and more beneficial than AC in the ORS bioconversion. However, this study warrants further research in exploring the efficiency of other earthworm species, feedstock selection, or seasonal variability in ORS management.

Experimental investigation on productivity enhancement of conical solar distillers using various sand bed types based on energy, exergy, and exergo-economic analysis

In this study, performance enhancement of conical distillers was investigated with various natural sand bed types. Four sand types with different colors (compositions and concentrations of chemical compounds) were tested and used as thermal storage materials to reduce heat loss, enhance evaporation process, and daily production. Three similar distillers were designed and investigated experimentally under the same climatic parameters over two consecutive days. Performance parameters of the proposed distillers, including yield, energy, exergy, and exergo-economic were analyzed and compared with those of reference distiller and other related studies. Results showed that the highest yield and performance values were achieved by the distiller combined with a golden sand bed. The utilization of golden sand bed achieves a daily production of 7.38 lm−2day−1 with enhancement of 10.31 %, 22.79 %, 35.91 %, and 60.43 % compared with yellow sand, red sand, white sand, and reference distillers, respectively. The daily energy and exergy efficiency of conical distillers combined with golden, yellow, red, and white sand beds 59.59 %, 44.84 %, 30.33 %, and 17.85 % and 143.52 %, 103.44 %, 64.73 %, and 36.39 %, respectively, higher than that of the reference distiller. Integrating golden, yellow, red, and white sand beds with conical distillers reduces the yield price and payback time by 60.43 %, 45.43 %, 30.65 %, and 18.04 %. The annual energy and exergy output of conical distillers combined with golden, yellow, red, and white sand beds were 130.54, 118.47, 106.60, 96.41, and 81.76 kWh/year and 6.08, 5.08, 4.00, 3.31, and 2.49 kWh/year, respectively.

Techno-economic assessment of high-temperature aquifer thermal energy storage system, insights from a study case in Burgwedel, Germany

High-temperature aquifer thermal storage (HT-ATES) is an effective method to mitigate the increasing greenhouse gas emissions, and it is attracting industry attention as an alternative to traditional fossil fuels for heating and cooling. However, the uncertainty of exploration and long profit cycles impede the popularization of HT-ATES technology. In this paper, to optimize HT-ATES evaluation and make the results more convictive, we demonstrate a numerical study based on a real district and a proven aquifer. An integrated HT-ATES model includes the wellbore and aquifer is used to simulate the fluid flow and heat transfer. Moreover, a dynamic economic assessment is demonstrated depending on the HT-ATES fluctuation performance. A 30-year HT-ATES cycling simulation shows that the wellbore and aquifer have had a continuous heating loss since the operation started. Working well and balancing the well lost 2.7% and 2.2% of total energy through the wellbore. The aquifer lost 4.1% of total energy due to heating transfer to overburden and other layers. HT-ATES could recover around 90% of stored total energy. The HT-ATES economic performance is affected by the heating store and production cycling, the benefit mainly comes from the heating production season. The initial investment and heat exchange efficiency between the HT-ATES & end-application system determines the levelized heat (LCOH) cost and payback time, the optimist case still needs 3 years to be profitable. HT-ATES have considerable green benefits, it could reduce local CO2 emissions 1937 t/year.

Experimental ginger drying by a novel mixed-mode vertical solar dryer under partial and fully loaded conditions

An innovative and compact mixed-mode vertical solar dryer (MVSD) with a circular solar collector is developed and tested for ginger slices drying under partial and fully loaded conditions. Ginger slices samples of 4, 5 and 6 mm thick were used for natural convective drying in MVSD under partially loaded condition. The thickness of the ginger slices was observed to affect the performance of the MVSD. The drying rate and thermal efficiency were observed to be highest for 5 mm thick ginger slices sample under partially loaded condition. The MVSD was further tested with full loading capacity for 5 mm thick ginger slices drying under natural and forced convection modes (NC and FC modes). The drying behavior of ginger slices was well described by Midilli-Kucuk model. Heat transfer coefficients and efficiency (thermal and exergy) were observed to be higher under forced convection mode. Embodied energy and energy payback time were observed as 554.44 and 585.53 kWh; and 2.85 and 2.99 years under NC and FC modes, respectively. The values of annualized capital cost and payback period were observed as INR 389.41 and 408.17; and 1.85 and 6.86 years under NC and FC modes, respectively. The quality of the ginger dried under FC mode was found comparatively better than that of under NC mode.

A Sustainable Solution for Urban Transport Using Photovoltaic Electric Vehicle Charging Stations: A Case Study of the City of Hail in Saudi Arabia

As the global shift toward sustainable transportation gains momentum, the integration of electric vehicles (EVs) becomes imperative, necessitating a robust and environmentally friendly charging infrastructure. Leveraging the abundant solar potential in the region, this study examines the technical, economic, and environmental feasibility of deploying photovoltaic electric vehicle charging stations (PV-EVCSs) in Hail City, Saudi Arabia, as a case study. This study examines factors such as the energy demand, grid integration, and user accessibility, aiming to address the challenges and opportunities presented by the urban fabric. The proposed solar charging station network seeks to catalyze a paradigm shift toward a cleaner and more sustainable transportation ecosystem, embodying a forward-thinking approach to meeting the evolving needs of urban mobility in the 21st century. The analysis encompasses many scenarios, encompassing a range of car battery sizes, charger powers, and car slots per station. Zone 4 is identified as the most crucial area, where seven charging stations are needed to fulfill the expected demand in the absence of any private charging alternatives. The economic evaluation of the 1047.35 kWp PV system reveals an estimated conventional payback time of 11.69 years, accompanied by a return on assets of 10.17%. The system generates accumulated cash flows amounting to SR 7,169,294.62 over 30 years, while the estimated operational and maintenance expenses are predicted to be SR 50,000 per year. The overall investment cost for the solar PV and EV charging stations is SR 4,487,982. This cost is offset by the yearly electricity savings from solar and grid sources, which can reach up to SR 396,465.26 by year 30. This work presents a detailed plan for the future of sustainable transport. It combines technical, environmental, and economic aspects to promote a cleaner and more sustainable urban mobility system.

Techno-economic assessment of solar photovoltaic electrification and calcium looping technology as decarbonisation pathways of alumina industry

Aluminium industry stands out as a significant source of CO2 emissions, due partially to the high energy demand of the alumina extraction stage. Accordingly, this study explores the implementation of direct resistive heating of mid-temperature processes in alumina production as an alternative to decrease CO2 emissions. Additionally, two different strategies are evaluated to decarbonize alumina industry: the generation of renewable electricity through solar photovoltaic panels and the integration of a CO2 capture plant based on calcium looping technology. This work comprehends the modelling and sizing of these plants and the assessment of their economic performance through the calculation of their Net Present Value and their respective payback periods. The integration of both strategies into an alumina refinery model reveals that electrification of low and mid-temperature processes yields a 15 % reduction in CO2 direct emissions, whereas calcium looping demonstrates the potential to capture 97 % of emissions with a 7 % energy penalty. Also, economic assessments indicate substantial potential for improvement through in-site electricity generation via solar photovoltaic panels, exhibiting a payback time of 4.5 years. Conversely, the feasibility of a calcium-looping plant is hindered by high capital expenses, necessitating a longer payback period of 19–24 years. Sensitivity analyses underscore the suitability of in-site renewable electricity generation, whereas carbon emission taxes emerge as crucial in incentivizing carbon-neutral processes, with thresholds around 95–125 €/tonne of CO2. Despite potential deviations from real industrial settings, this study provides evidence for environmentally friendly strategies in alumina production that demonstrate limited adverse effects on economic performance.

Hierarchical model for design and operation optimization of district cooling networks

District cooling systems offer a promising alternative to conventional cooling, thanks to overall larger efficiencies and reduced carbon footprint. On the other hand they are characterized by large capital and operational costs that impede their diffusion. Optimizing the design and operation of these systems is therefore fundamental to fully exploit their potential. This paper proposes a novel optimization framework for the simultaneous optimization of design and operation of these systems. The model integrates a genetic algorithm at a master level with Mixed Integer Linear Programming models at a lower level. This approach enables the optimization of various aspects, including network topology, plant locations, supply temperatures and the selection of thermal storage technology. The study showed that in the specific case of Singapore, where the cost for space occupancy is significant, latent heat thermal storages are preferred. In addition, the results highlighted the cost benefits of thermal storage, as district cooling networks lacking it can be from 6.2% to 20.8% more expensive, depending on the scenario. Furthermore, the study demonstrated that the utilization of waste heat through absorption chillers enhances the economic feasibility of district cooling, lowering the payback time by up to 5 years. Lastly, it was observed that 3 °C increase of the indoor set point temperature could reduce the payback time by 3 years and increase the final net present value by 43%, as larger network supply temperatures allow chillers to operate with better performances. The developed model allows to estimate various crucial outcomes with few input parameters, representing a useful tool for both research and planning.

Tomato Residue Management from a Biorefinery Perspective and towards a Circular Economy.

The tomato industry is a relevant socio-economic activity in the European Union, while it generates a large variety of residues. Tomatoes unfit for consumption, tomato peels, seeds, industrial pomace, and plants are examples of residues of this industry. Commonly, some of the residues can be left in the field, composted, used for animal feeding, or valorized through anaerobic digestion. However, more economic value can be attributed to these residues if a biorefinery approach is applied. Indeed, many value-added compounds can be obtained by the integration of different processes while closing the carbon and nutrient loops. The extraction of bioactive compounds followed by anaerobic digestion and composting seems to be a viable proposal for a biorefinery approach. Thus, this study aims to review the biorefinery strategies for valorizing tomato residues, highlighting the main processes proposed. The recovery of lycopene, β-carotene, and phenolic compounds has been widely studied at the lab scale, while energy recovery has already been applied at the industrial scale. Although techno-economic analysis is scarce for tomato residue valorization processes, positive net present values (NPV) and low payback times (PBT) have been reported in the literature. Thus, more work comparing multiple extraction technologies and biorefinery strategies coupled with economic and environmental assessment should be performed to select the most promising management route for tomato residues.

Investigation on a novel hybrid system based on radiative sky cooling and split thermoelectric cooler driven by photovoltaic cell

This paper develops a novel cooling and heating system by integrating a novel split thermoelectric cooler (STEC) with photovoltaic power generation and radiative sky cooling. The system uses photovoltaic driven STEC modules to generate cooling and heating combined with radiative sky cooling to improve cooling capacity. By harnessing the distinctive characteristics of photovoltaic technology and radiative sky cooling, the new system is capable of operating continuously for 24 h without requiring any additional energy input. The system mathematical model is established, and the effects of STEC module number, solar illumination intensity, area ratio and ambient temperature on the performance are studied. Results demonstrate that the cooling efficiency of the system is 3.02 and the heating efficiency is 1.86 when the number of STEC modules is 3. In a year, the monthly average heat production of the system fluctuates due to changes in the solar illumination intensity, while the fluctuation of cooling capacity is small. The system cold production is larger than heat production, which is more suitable for application in the area with high demand for year-round refrigeration. The new system has good energy and economic performance with payback time being shorter than that of the photovoltaic-air conditioning system.

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.

Assessment of wind energy resource in the western region of Somaliland

As the population of Somaliland continues to grow rapidly, the demand for electricity is anticipated to rise exponentially over the next few decades. The provision of reliable and cost-effective electricity service is at the core of the economic and social development of Somaliland. Wind energy might offer a sustainable solution to the exceptionally high electricity prices. In this study, a techno-economic assessment of the wind energy potential in some parts of the western region of Somaliland is performed. Measured data of wind speed and wind direction for three sites around the capital city of Hargeisa are utilized to characterize the resource using Weibull distribution functions. Technical and economic performances of several commercial wind turbines are examined. Out of the three sites, Xumba Weyne stands out as the most favorable site for wind energy harnessing with average annual power and energy densities at 80 m hub height of 317 kW/m2 and 2782 kWh/m2, respectively. Wind turbines installed in Xumba Weyne yielded the lowest levelized cost of electricity (LCOE) of not more than 0.07 $/kWh, shortest payback times (i.e., less than 7.2 years) with minimum return on investment (ROI) of approximately 150%.