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The objective of this study is to thermodynamically investigate the performance of solar dryers by delaying the airflow in the collector. For this reason, a triple air path on a single pass collector with the fan powered by a wind generator was developed and evaluated in a very humid climate. The evaluation parameters were drying efficiency, energy and exergy analysis, sustainability assessment, CO2mitigation ability and effective moisture diffusivity of dried product. The results showed that the collector efficiency of triple air passage path collector designs improved the direct passage collector by 119%. The overall collector and drying efficiencies were 8.43% and 2.6% higher than the direct flow path collector. The specific energy consumption was 1.1033 kWh/kg while the specific moisture extraction rate was obtained as 0.273 kg/kW, respectively. The average exergy efficiency ranged between 38.09 and 63.81% while the waste exergy ratio, improvement potential and sustainability index for the three dryers ranged from 0.00 to 1.13, 7.54 × 10–7to 2.003 kW and 0.00 to 11.47, respectively. Using the solar dryers instead of the coal-powered dryer will mitigate more CO2into the atmosphere in the range of 9741.334 to 21,481. 476 tons of CO2per year while using grid-based electricity will limit the least amount of CO2in the range of 12.981 to 14.153351.50 tons of CO2per year. more...

The paper presents the environmental sustainability of the Nigeria transport sector (NTPS) through the decomposition and decoupling analysis from 1988–2019. The study’s objective is to determine ways of saving energy in the NTPS and reduce carbon emission for a sustainable environment. The approach was based on the Logarithmic Mean Divisa Index (LMDI) and the Tapio approach, built on Kaya extended identity. Five decoupling indicators were considered based on the four energy carriers consumed in the NTPS. The indicators include economic activity, energy structure, economic structure, population and energy intensity. The results identified three decoupling states, weak negative decoupling, weak decoupling and strong decoupling. The energy intensity, economic activity, population and energy structure prevented decoupling during the study period, while the economic structure factor promoted decoupling. The overall impact of carbon emissions from NTPS was calculated at 44.45 million tonnes of CO2. The study suggests frameworks that will support policy makers to formulate broad base policies for environmental sustainability. more...

The paper presents 3E (energy, exergy and economic) analysis of a modified Kalina power-cooling vapour absorption cycles (KLPCCs) for better thermo-economic figures of merit to drive affordable energy access and climate change mitigation. The analysis presents a balanced technical and economic conclusion in view of resource management and sustainability. The system utilized a Kalina power-cooling system at the topping cycle and an embedded vapour absorption system (VAB) at the bottoming cycle, which is a novelty. In the modified KLPCC, a supplementary evaporator and heat exchangers are integrated with the bottoming cycle. The considered performance indicators include energy efficiency, exergy efficiency, cooling rate, turbine net output, COP, and cost rate. From the results, about 1077 kW cooling rate was produced, while the energy efficiency, exergy efficiency, COP, and turbine output were estimated at 16.97 %, 8.15 %, 0.706, and 291 kW, respectively. The LCC of $ 1.573 million was achieved, with the break-even point and unit energy cost calculated at five years and 0.0134 $/ kWh, respectively. The outcomes are holistic and adequate for policymakers in the field of energy access and environmental sustainability. more...

AbstractThe performance and thermo-sustainability indicators (TSI) of non-hybrid organic Rankine cycles (ORCs) are considered at varying evaporator pressure (EVP) and heat source temperature (HST). The ORCs structures include the ORC-basic, ORC-internal heat exchanger (ORC-IHE), ORC-turbine bleeding and ORC-turbine bleeding/regeneration. The TSI considered exergy efficiency, waste exergy ratio (WER), exergetic sustainability index (ESI) and environmental effect factor (EEF). The calculated overall exergy efficiency varies from 35.35 to 47.23 for evaporator pressure between 2 and 3 MPa and 49.02 to 52.71 for HST between 500 and 650 K. Additionally, WER, ESI and EEF were found to vary from 0.253 to 0.278, 1.15 to 1.87 and 0.547 to 0.82, respectively while ESI decreases for all variants of HST. The results indicate high ESI and low WER in ORC-IHE and the ORC-turbine bleeding /regeneration for all variations in EVP and HST. more...

Relevant meteorological files are needed by simulation software to assess the energy performances of buildings or efficiency of renewable energy systems. This paper adopts the Sandia method to generate typical meteorological year (TMY), using a 35-year hourly measured meteorological dataset from four stations in the northern region of Nigeria. The cumulative distribution function (CDF) for each year was compared with that of the long-term composite of all the years in the period for the seven major weather indices made up of relative humidity, wind speed, minimum temperature, global solar radiation, precipitation, mean temperature and maximum temperature. The 12 typical meteorological months (TMMs) selected from the different years were used for formulation of a TMY for the zone. In addition, performance assessment of a 72-cell polycrystalline solar PV module using the generated TMY and long-term (LT) values was also conducted. Two statistical indicators, the mean percentage error and the root mean square error, were adopted to evaluate the performance of each TMY with the LT mean, and also that of the PV energy system. Findings show that the TMMs are evenly spread within the data periods across the sites while closest fit between the long-term mean and TMY are obtained with the global solar radiation followed by the mean temperature in all the sites especially in Bida and Minna. From the energy system analysis carried out, it was found that TMY data are able to predict the performance of the PV system to within 5% of the LT data. more...

The study presents the wind energy potential (WEP) for six locations in Cross River State, Nigeria. The objective of the study was to assess the WEP of the selected sites for electricity generation, using small size wind energy conversion systems (WECs). The wind data were measured at 10 m height and ranged from 4 to 10 years. Additionally, the data were evaluated using the two-parameter Weibull function. Results obtained show that annual mean wind speed, vm, and Weibull parameters kand crange from 3.21 to 4.55 m/s, 3.32 to 6.69 and 2.99 to 5.40 m/s, in that order. The cost per kWh of energy for the selected WECs fluctuated between 0.0626 ≤ COE ≤ 0.1375 USD/kWh, while the avoidable CO2emissions exist between 0.64 and 38.21 tons/year. However, the probable savings made from diesel was not greater than 14,524.94 litres/year for the locations with high WEP for small-scale stand-alone applications. more...

ABSTRACTThe wind characteristics of six locations in Niger Delta, Nigeria, and the economics of the application of wind energy for water pumping and possible avoidable CO2emissions through wind utilisation were examined. The wind data were measured at 10 m height and analysed using the two-parameter Weibull model. Small size wind turbines were accessed with Goulds 45J03 water pump series. The average power density, average energy density and annual energy across locations ranged between  W/m2,  kWh/m2and  kWh/m2/year, respectively. Bergey Excel-10 kW turbine had the lowest cost of energy and water pumping cost of $/kWh and $/m3, respectively. The annual capacity of water yield varies from 21,847 to 120,206 m3/year on a total dynamic head of 50 m. Furthermore, the annual diesel saved across the locations ranged from 1605 to 8696 l/year (17.47 to 94.67 GJ/year), while the annual averaged CO2saved was between 4.32 and 22.93 tons/year. more...

The CO2emissions trend and their reduction potential in the Nigerian manufacturing sector from 2010 to 2020 were studied. The Logarithmic Mean Divisia Index was applied to decompose the change in CO2emissions into pre-set factors: carbon intensity effects, firm energy intensity effects, cost structure effects, asset-turnover effect, asset-to-equity effect, equity-funded production effect and productive capacity utilization. The results show that the change in emissions increased by 1668×1012GJ between 2010 and 2020. Energy intensity and equity-funded production were the leading drivers of increased emissions, while productive capacity utilization reduced emissions. The CO2emissions increased throughout the study, except for a few periods. Without a carbon tax policy, the results show that firm-level drivers increased CO2emissions in the business-as-usual scenario. However, under the 5% carbon tax (CAT) policy scenario on energy consumption, there was a reduction in CO2emissions between 2010 and 2020. Furthermore, a CAT policy of 5% on energy consumption reduced CO2emissions by 22%. A further implication of CAT policy, given its interaction with firm-level drivers, resulted in lowering CO2emissions in the interactional scenario. The findings indicate productive capacity utilization, equity-funded production, and CAT impacted CO2emissions variation. more...

The study presents a power-cooling organic Rankine cycle with an ejector system (ORCPCES). The objective is to determine the thermodynamic, economic and sustainability of the ORCPCES from the manufacturing, commissioning and decommissioning phases. Component-wise modelling was first performed based on the exergy concept. The system simulation was carried out using a developed source code in Engineering Equation Solver (EES). The refrigerant leakages and the material component impact on the environment were evaluated at all phases of the plant life cycle. The results indicate that the evaporator cooling rate (ECR) and the power-cooling efficiency (PCE) varied from 120.8 to 153 kW and 28.87 to 34.43 % across the refrigerants with the highest PCE and exergy efficiency obtained using R1234ze. The maximum power output was obtained using R1234ze. The overall environmental impact due to the components occurred at5.1×105mPts, 5.24×105mPtsand 5.4×105mPtsfor R245fa, R1234yf, and R1234ze, respectively, while 4.01×105mPts7.81×104mPtsand9.33×105mPtswas due to the working fluids in that order. The unit cost of electricity (UCOE) across the refrigerants varies from 0.181$/kWh to 0.2291$/kWh with the least UCOE, 0.181$/kWh obtained using R1234ze. The highest exergetic sustainability index of 0.56 was achieved using R1234ze. more...