Optimum configuration and design of a photovoltaic–diesel–battery hybrid energy system for a facility in University of Port Harcourt,Nigeria

Optimum configuration, using a hybrid optimisation model for electric renewable software, and design of a photovoltaic (PV)–diesel–battery hybrid energy system has been proposed to power a facility in the University of Port Harcourt, which is located in the suburb of Port Harcourt city, Nigeria. The configuration of the optimum hybrid system is selected based on top-ranked system configuration, according to the net present cost. An optimal system design delivers the best components alongside appropriate operating strategies to provide the most efficient, reliable cost-effective system possible. The system investigated reduces CO₂ emissions by 36.3%/year. This will reduce costs imposed on CO₂ emissions by future environmental legislation. The system has a better potential for providing the energy needs of the facility considered in this paper compared with a stand-alone PV–battery system as capital costs are reduced by 55%. Reliability was improved as the diesel generator can provide power as and when it is needed.     

Optimal size and cost analysis of stand-alone hybrid wind/photovoltaic power-generation systems

Design of sustainable energy systems for the supply of electricity need correct selection and sizing to reduce investment costs. In this article, a new sizing methodology is developed for stand-alone hybrid wind/photovoltaic (PV) power systems, using multi-objective optimisation algorithms. Multi-objective particle swarm optimisation algorithm and non-dominated sorting genetic algorithm-II are selected related to their match with the nature of renewable energy sizing problem. A match evaluation method is developed based on renewable energy supply/demand match evaluation criteria, to size the proposed system in the lowest cost. As an example of application of this technique, six different wind turbines (WTs) and also six different PV modules have been considered. The sizing methodology determines a multi-objective design, obtaining the best solutions that the applied algorithm has found simultaneously considering three objectives: inequality coefficient, correlation coefficient, and annualised cost of system. The optimal number of WTs, PV modules, and batteries ensuring that the system total cost is minimised while guaranteeing a highly reliable source of load power is obtained. A management strategy has been designed to achieve higher electricity match rate. Based on the proposed technique, the algorithm developed for different cases, using the climatic condition data of the city Zabol, located in south-east of Iran. Additionally, a study of operating hours of diesel generator in optimal configuration is carried out.     

Assessment of electricity generation by wind power in nine costal sites in Malaysia

In this article, the wind power potential in Malaysia is examined. Hourly wind speed data for nine sites in Malaysia are used to optimally design wind power systems for remote housing electrification. These nine sites are Bintulu, Kota Kinabalu, Kuala Terengganu, Kuching, Kudat, Mersing, Sandakan, Tawau and Pulau Langkawi. The designed wind power systems are supposed to supply hourly load demand 6.13?kWh/day, 0.52?kW peak with 1% loss of load probability. The unit cost of the energy produced by each system is calculated and compared to the unit cost of the energy produced by a standalone photovoltaic (PV) power systems and a diesel generator power systems. The results show that the average unit cost of the energy produced by a wind power system in Malaysia is 1.6–7.29?USD/kWh while it is 0.35–0.5?USD/kWh and 0.27–0.30?USD/kWh for PV power system and diesel generator power system, respectively. Based on this, the use of wind power systems as standalone systems is not recommended for the selected sites.     

Simplified method of sizing and life cycle cost assessment of building integrated photovoltaic system

This paper presents methodology to evaluate size and cost of PV power system components. The simplified mathematical expressions are given for sizing of PV system components. The PV array size is determined based on daily electrical load (kWh/day) and number of sunshine hours on optimally tilted surface specific to the country. Based on life cycle cost (LCC) analysis, capital cost (US$/kW_P) and unit cost of electricity (US$/kWh) were determined for PV systems such as stand-alone PV (SAPV) and building integrated PV (BIPV). The mitigation of CO₂ emission, carbon credit and energy payback time (EPBT) of PV system are presented in this paper. Effect of carbon credit on the economics of PV system showed reduction in unit cost of electricity by 17-19% and 21-25% for SAPV and BIPV systems, respectively. This methodology was illustrated using actual case study on 2.32 kW_P PV system located in New Delhi (India).     

A heat pipe photovoltaic/thermal (PV/T) hybrid system and its performance evaluation

Building-integrated photovoltaic/thermal (BIPV/T) system has been considered as an attractive technology for building integration. The main part of a BIPV/T system is PV/T collector. In order to solve the non-uniform cooling of solar PV cells and control the operating temperature of solar PV cells conveniently, a heat pipe photovoltaic/thermal (PV/T) hybrid system (collector) has been proposed and described by selecting a wick heat pipe to absorb isothermally the excessive heat from solar PV cells. A theoretical model in terms of heat transfer process analysis in PV module panel and introducing the effectiveness-number of transfer unit (?-NTU) method in heat exchanger design was developed to predict the overall thermal-electrical conversion performances of the heat pipe PV/T system. A detailed parametric investigation by varying relevant parameters, i.e., inlet water temperature, water mass flow rate, packing factor of solar cell and heat loss coefficient has been carried out on the basis of the first and second laws of thermodynamics. Results show that the overall thermal, electrical and exergy efficiencies of the heat pipe PV/T hybrid system corresponding to 63.65%, 8.45% and 10.26%, respectively can be achieved under the operating conditions presented in this paper. The varying range of operating temperature for solar cell on the absorber plate is less than 2.5 °C. The heat pipe PV/T hybrid system is viable and exhibits the potential and competitiveness over the other conventional BIPV/T systems.     

浅谈风光互补发电系统的应用

本文介绍了风光互补发电系统的构成、特点及前景,并通过一个实例,分析了整个系统的造价,指出了风光互补发电系统的成本问题仍然是限制它应用的主要因素。现在风光互补发电系统的造价虽然很高,但是因为太阳能和风能有着良好的互补性,同时它们的污染也非常小,是一种极具发展前景的可再生能源组合。最后提出了一种在风光互补发电系统上的PV/T混合系统,指出通过混合应用将有可能进一步降低系统的成本。     

Thermal behavior of a novel type see-through glazing system with integrated PV cells

Steady natural convective airflow in a novel type glazing system with integrated semi-transparent photovoltaic (PV) cells has been analyzed numerically using a stream function vorticity formulation. Based on the resulting numerical predictions, the effects of Rayleigh numbers on airflow patterns and local heat transfer coefficients on vertical glazing surfaces were investigated for Rayleigh numbers in the range of 10³ ≤ Ra ≤ 2 × 10⁵. Significant agreement for the Nusselt numbers was observed between numerical simulation results in this study and those of earlier experimental and theoretical results available from the literature. In addition, the effect of air gap thickness in the cavity on the heat transfer through the cavity is evaluated. The optimum thickness of the air layer in this research is found to be in the range of 60–80 mm. This novel glazing system type could not only generate electricity but also achieve potential energy savings by reducing the air conditioning cooling load when applied in subtropical climatic conditions and simultaneously provide visual comfort in the indoor environment.     

Techno-economic analysis of 1 MWp grid connected solar PV plant in Malaysia

Most of the public and private technical universities in Malaysia have considerably abundant free areas, which could be a better place for equipping the renewable energy harvesters. The main objective of this paper is to analyse the feasibility of developing a solar PV plant at two different campuses of Universiti Malaysia Pahang (UMP). This paper proposes 1 MW solar PV power plant at the Pekan Campus (Rural Campus), and Gambang (Suburban Campus) of UMP located in the east coast state of Pahang, which is biggest among other states in Peninsular Malaysia. The technical viability of the proposed crystalline technology based PV plant with open rack or free stand mounting position is analysed using PVGIS (Photovoltaic Geographical Information Systems) and PV Watts’s software. The economic and environmental aspects of the proposed plant are also analysed based on standard parameters. The proposed plant of 1?MWp Solar PV plant can generate around 1390?MWh, of electricity per annum with a GHG emission reduction of 818.71 tCO₂ per annum. The PV power plant can contribute in meeting 5% of total energy requirements of the campus. The technical performance obtained through PVGIS is quite comparable with the PV Watts results.     

Condenser heat recovery with a PV/T air heating collector to regenerate desiccant for reducing energy use of an air conditioning room

This paper presents an experimental test along with procedures to investigate the validity of a developed simulation model in predicting the dynamic performance of a condenser heat recovery with a photovoltaic/thermal (PV/T) air heating collector to regenerate desiccant for reducing energy use of an air conditioning room under the prevailing meteorological conditions in tropical climates. The system consists of five main parts; namely, living space, desiccant dehumidification and regeneration unit, air conditioning system, PV/T collector, and air mixing unit. The comparisons between the experimental results and the simulated results using the same meteorological data of the experiment show that the prediction results simulated by the model agree satisfactorily with those observed from the experiments. The thermal energy generated by the system can produce warm dry air as high as 53 °C and 23% relative humidity. Additionally, electricity of about 6% of the daily total solar radiation can be obtained from the PV/T collector in the system. Moreover, the use of a hybrid PV/T air heater, incorporated with the heat recovered from the condenser to regenerate the desiccant for dehumidification, can save the energy use of the air conditioning system by approximately 18%.     

Theoretical performance assessment of an integrated photovoltaic and earth air heat exchanger greenhouse using energy and exergy analysis methods

In this paper, a simplified mathematical model develops to study round the year effectiveness of photovoltaic/thermal (PV/T) and earth air heat exchanger (EAHE) integrated with a greenhouse, located at IIT Delhi, India. The solar energy application through photovoltaic system and earth air heat exchanger (EAHE) for heating and cooling of a greenhouse is studied with the help of this simplified mathematical model. Calculations are done for four types of weather conditions (a, b, c and d types) in New Delhi, India. The paper compares greenhouse air temperatures when it is operated with photovoltaic/thermal (PV/T) during daytime coupled with earth air heat exchanger (EAHE) at night, with air temperatures when it is operated exclusively with photovoltaic/thermal system (PV/T) and earth air heat exchanger (EAHE), for 24 h. The results reveal that air temperature inside the greenhouse can be increased by around 7-8 °C during winter season, when the system is operated with photovoltaic (PV/T), coupled with earth air heat exchanger (EAHE) at night. From the results, it is seen that the hourly useful thermal energy generated, during daytime and night, when the system is operated with photovoltaic (PV/T) coupled with earth air heat exchanger (EAHE), is 33 MJ and 24.5 MJ, respectively. The yearly thermal energy generated by the system has been calculated to be 24728.8 kWh, while the net electrical energy savings for the year is 805.9 kWh and the annual thermal exergy energy generated is 1006.2 kWh.     

Economic optimization of a cogeneration system for apartment houses in Korea

A cogeneration system which can be used as a distributed generation source produces electricity and heat energy simultaneously from a single source of fuel. For industrial and domestic applications, where both kinds of energy are required, the cogeneration system can return fossil fuel energy savings up to 30%, and can reduce CO₂ emissions correspondingly as compared with a conventional system. In this study, eight apartments with residential areas in the range of 57200 m² to 182760 m² were chosen to study how much energy savings can be achieved by adoption of the cogeneration system in those apartments. Based on the energy demand data for heat and electricity, an optimum configuration of the cogeneration system for each apartment was determined by a developed computer program. The economic gain achieved by introducing the cogeneration system in those apartments was estimated and the monitored values compared with the estimated ones. By adoption of the cogeneration system, the natural gas saved was more than 30% and an average economic gain of US$ 3.6 m⁻²/year in the overall energy cost was obtained.     

Removal of boron from ceramic industry wastewater by adsorption-flocculation mechanism using palm oil mill boiler (POMB) bottom ash and polymer

Boron is extensively used in the ceramic industry for enhancing mechanical strength of the tiles. The discharge of boron containing wastewater to the environment causes severe pollution problems. Boron is also dangerous for human consumption and causes organisms' reproductive impediments if the safe intake level is exceeded. Current methods to remove boron include ion-exchange, membrane filtration, precipitation-coagulation, biological and chemical treatment. These methods are costly to remove boron from the wastewater and hence infeasible for industrial wastewater treatment. In the present research, adsorption-flocculation mechanism is proposed for boron removal from ceramic wastewater by using Palm Oil Mill Boiler (POMB) bottom ash and long chain polymer or flocculant. Ceramic wastewater is turbid and milky in color which contains 15 mg/L of boron and 2000 mg/L of suspended solids. The optimum operating conditions for boron adsorption on POMB bottom ash and flocculation using polymer were investigated in the present research. Adsorption isotherm of boron on bottom ash was also investigated to evaluate the adsorption capacity. Adsorption isotherm modeling was conducted based on Langmuir and Freundlich isotherms. The results show that coarse POMB bottom ash with particle size larger than 2 mm is a suitable adsorbent where boron is removed up to 80% under the optimum conditions (pH = 8.0, dosage = 40 g bottom ash/300 ml wastewater, residence time = 1 h). The results also show that KP 1200 B cationic polymer is effective in flocculating the suspended solids while AP 120 C anionic polymer is effective in flocculating the bottom ash. The combined cationic and anionic polymers are able to clarify the ceramic wastewater under the optimum conditions (dosage of KP 1200 B cationic polymer = 100 mg/L, dosage of AP 120 C anionic polymer = 50 mg/L, mixing speed = 200 rpm). Under the optimum operating conditions, the boron and suspended solids concentration of the treated wastewater were reduced to 3 mg/L and 5 mg/L respectively, satisfying the discharge requirement by Malaysia Department of Environment (DOE). The modeling study shows that the adsorption isotherm of boron onto POMB bottom ash conformed to the Freundlich Isotherm. The proposed method is suitable for boron removal in ceramic wastewater especially in regions where POMB bottom ash is abundant.     

Correlation between thermal conductivity and the thickness of selected insulation materials for building wall

Correlation between thermal conductivity and the thickness of selected insulation materials for building wall has been analyzed. The study has found that a relationship between the thermal conductivity (k) and optimum thickness (x_opt) of insulation material is non-linear which obeys a polynomial function of x_opt = a + bk + ck², where a = 0.0818, b = −2.973, and c = 64.6. This relationship will be very useful for practical use to estimate the optimum thickness of insulation material in reducing the rate of heat flow through building wall by knowing its thermal conductivity only.     

Optimally sized hybrid energy system for auxiliaries of a cement manufacturing unit with diesel fuel price sensitivity analysis

Prices of fuels such as coal and diesel are showing uptrend continuously in India due to which the manufacturing sector is finding it hard to control the production cost. The manufacturing units are emphasising upon innovative practices to reduce the electrical energy consumption in order to reduce production cost. They are recognising renewable energy as one of the options to save fuel cost to some extent by running some partial load on this energy. This paper is presenting a technical and economic analysis for proposing a hybrid renewable energy system, comprising Solar Photovoltaic, wind, a storage battery and a diesel unit, for running auxiliary load of a cement manufacturing unit located in Durg district of Chhattisgarh, India. As the diesel prices are continuously increasing almost rupees 0.5 per month in India for the last few months, the diesel price sensitivity analysis is also done for optimal system sizing. The results show that diesel price increment from $1.01 to $1.09 does not affect optimal system size but only net present cost and levelised cost of energy. When diesel price increases beyond $1.09, the optimal system size increases resulting in capital cost increment. It attains a new optimal system size at a diesel price of $1.13.     

Naphthenic acids and other acid-extractables in water samples from Alberta: What is being measured?

There is increasing international interest in naphthenic acids (NAs, classical formula C_nH_2n + ZO₂) found in the oil sands from Alberta, Canada and in petroleum from around the world. The complexity of NAs poses major analytical challenges for their quantification and characterization. We used ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR MS) to probe the make up of NAs from various sources by searching for peaks corresponding to the formula C_nH_2n + ZO_x, for combinations of n = 8 to 30, Z = 0 to −12, and x = 2 to 5. The sources included three commercial NAs preparations, and the acid-extractable organics from eight oil sand process-affected waters (OSPW) and from six surface fresh waters. Extracts from OSPW contained between 1 and 7% sulfur. The mass spectra showed between 300 and 1880 peaks, with > 99% of the peaks having m/z between 145 and 600. In most cases, < 20% of the peaks were assigned as classical NAs (x = 2) and oxy-NAs (x = 3 to 5). The classical NAs from the OSPW were predominantly Z = −4 and −6, whereas those from the fresh waters were mainly Z = 0, with palmitic and stearic acids being the major components in the fresh waters. Remarkably, when the peak abundances were considered, < 50% of the total abundance could be assigned to the classical and oxy-NAs. Thus, > 50% of the compounds in the extracts of OSPW were not “naphthenic acids”. Based on these findings, it appears that the term “naphthenic acids”, which has been used to describe the toxic extractable compounds in OSPW, should be replaced by a term such as "oil sands tailings water acid-extractable organics (OSTWAEO)". Classical and oxy-NAs are components of OSTWAEO, but this term would not be as misleading as “naphthenic acids”.     

Compromises between form and function in grid-connected,building-integrated photovoltaics (BIPV) at low-latitude sites

The integration of photovoltaic (PV) modules on building façades and rooftops is an ideal application of solar electricity generators in the urban environment. Maximum annual performance of grid-connected PV is usually obtained with modules tilted at an angle equal to the site latitude, facing the equator. The performance of PV systems not tilted and oriented ideally can drop considerably, depending on site latitude. With grid parity – when the cost of solar electricity becomes competitive with conventional electricity – expected in many countries in the present decade, a more widespread application of PV on buildings is expected, and in this context the main goal of this paper is to demonstrate that good compromises between form and function are possible. In this work we compare the annual energy generation of a curved BIPV system installed as a car port rooftop, with an ideally-oriented and tilted, flat BIPV system installed as a building’s rooftop cover at a low-latitude site (27°S). For the one-year period analysed, the curved-shape BIPV system annual yield was 12% lower than that of the reference BIPV system, and during the summer months (November to February), the curved BIPV installation presented a higher energy yield than the latitude-tilted generator. With these results we show that a good compromise can be reached between form and function in BIPV systems.     

Transport and retention of a bacteriophage and microspheres in saturated, angular porous media: effects of ionic strength and grain size

Eight saturated column experiments were conducted to examine the effects of solution chemistry and grain size on the transport of colloids through crushed silica sand. Two sizes of colloids, 0.025-μm bacteriophage (MS-2) and 1.5-μm carboxylated microspheres, were used as surrogates for the transport of pathogenic viruses and bacteria, respectively. Increasing the Ca²⁺ concentration from 1 to 4.8 mM (along with background monovalent ions) resulted in complete attenuation (>6-log decrease in C/C₀) of MS-2, but caused only a 1-log reduction (C/C₀ = 0.1) in the concentration of the microspheres. Decreasing grain size from medium sand (d₅₀ = 0.70 mm) to fine sand (d₅₀ = 0.34 mm) resulted in substantial decreases in effluent concentrations of both the MS-2 (5-log decrease) and microspheres (>2.5-log decrease). Comparison of observed colloid retention to that predicted by a recently published correlation equation for colloid filtration revealed that the model can considerably underpredict (by 4 orders of magnitude or more) colloid retention by angular sand over distances as short as 20 cm. This indicates that state-of-the-art colloid filtration models are still limited in applicability to natural systems.     

Modeling of a novel Trombe wall with PV cells

A novel Trombe wall with PV cells is presented in this paper. A two-dimensional model of PV glass panel and a model of the PV-Trombe wall system are established. The temperature distribution and electrical performance of the PV-Trombe wall system are also obtained. Results show that according to the measured weather data and the special simulation condition, the temperature difference between the elements with and without PV cell on the glass panel reaches a maximum value of 10.6 ^°${}^{°}$C; the temperature difference between the room with and without PV-Trombe wall reaches a maximum value of 12.3 ^°${}^{°}$C during 3 days; after 7 days’ operation, the all-day temperature of the room with PV-Trombe wall retains at about 13.4 ^°${}^{°}$C and an increase of 5.00% for the electrical efficiency can be achieved.     

Exposure assessment of PM2.5 and urinary 8-OHdG for diesel exhaust emission inspector

Animal studies have shown exposure to diesel exhaust particles (DEPs) to induce production of reactive oxygen species (ROSs) and increase levels of 8-hydroxydeoxyquanosine (8-OHdG). Controversial results have been obtained regarding the effects of workplace exposure on urinary 8-OHdG level. This study assessed concentrations of environmental PM_2.5 in DEP (DEP_2.5), personal DEP_2.5 and urinary 8-OHdG of diesel engine exhaust emission inspector (inspector) at a diesel vehicle emission inspection station (inspection station). The analysis specifically focuses on the factors that influence inspector urinary 8-OHdG. Repeated-measures study design was used to sample for five consecutive days. A total of 25 environmental PM_2.5 measurements were analyzed at 5 different locations by using a dichotomous sampler, and a total of 55 personal PM_2.5 measurements were analyzed from inspectors by using PM_2.5 personal sampler. During the sampling period, a total of 110 pre- and post-work urine samples from inspectors, and 32 samples from the control group were collected. Following age and sex matching between the inspectors and the control group, levels of urinary 8-OHdG were analyzed.Environmental and personal concentrations of DEP_2.5 were 107.25 ± 39.76 (mean ± SD) and 155.96 ± 75.70 μg/m³, respectively. Also, the concentration of urinary 8-OHdG differed significantly between inspector and control non-smokers, averaging 14.05 ± 12.71 and 6.58 ± 4.39 μg/g creatinine, respectively. Additionally, urinary 8-OHdG concentrations were associated with diesel exposure after controlling for smoking and cooking at home. Compared with the control group, the inspector displayed significantly increased levels of urinary 8-OHdG. Diesel exhaust is the single pollutant involved in the exposure of DEP_2.5 at the inspection station, as confirmed by the final results.     

Modelling air pollution for epidemiologic research — Part I: A novel approach combining land use regression and air dispersion

A common limitation of epidemiological studies on health effects of air pollution is the quality of exposure data available for study participants. Exposure data derived from urban monitoring networks is usually not adequately representative of the spatial variation of pollutants, while personal monitoring campaigns are often not feasible, due to time and cost restrictions. Therefore, many studies now rely on empirical modelling techniques, such as land use regression (LUR), to estimate pollution exposure. However, LUR still requires a quantity of specifically measured data to develop a model, which is usually derived from a dedicated monitoring campaign. A dedicated air dispersion modelling exercise is also possible but is similarly resource and data intensive.This study adopted a novel approach to LUR, which utilised existing data from an air dispersion model rather than monitored data. There are several advantages to such an approach such as a larger number of sites to develop the LUR model compared to monitored data. Furthermore, through this approach the LUR model can be adapted to predict temporal variation as well as spatial variation. The aim of this study was to develop two LUR models for an epidemiologic study based in Greater Manchester by using modelled NO₂ and PM₁₀ concentrations as dependent variables, and traffic intensity, emissions, land use and physical geography as potential predictor variables. The LUR models were validated through a set aside “validation” dataset and data from monitoring stations.The final models for PM₁₀ and NO₂ comprised nine and eight predictor variables respectively and had determination coefficients (R²) of 0.71 (PM₁₀: Adj. R² = 0.70, F = 54.89, p < 0.001, NO₂: Adj. R² = 0.70, F = 62.04, p < 0.001). Validation of the models using the validation data and measured data showed that the R² decreases compared to the final models, except for NO₂ validation in the measured data (validation data: PM₁₀: R² = 0.33, NO₂: R² = 0.62; measured data: PM₁₀: R² = 0.56, NO₂: R² = 0.86). The validation further showed low mean prediction errors and root mean squared errors for both models.