Size optimization of a PV/wind hybrid energy conversion system with battery storage using response surface methodology

Reliability evaluation of stand-alone hybrid photovoltaic energy system for rural healthcare centre

Telecommunications industry requires efficient, reliable and cost-effective hybrid system as alternative to the power supplied by diesel generator. This paper proposed a solar - photovoltaic (PV)/Diesel hybrid power generation system suitable for Global System for Mobile communication (GSM) base station site. The study is based on simulation and optimization of hybrid system for a GSM base station site located in Abuja (FCT), Nigeria with a daily load of 318kWh/d. Solar radiation for the design of the system was obtained from NASA surface Meteorology and solar energy website at a location of 9° 00' N latitude and 7° 00' E longitude, with annual average solar radiation of 5.45 kWh/m²/d. The HOMER software was used for the design of the proposed power system. The study evaluates savings associated with conversion of the diesel powered system to a PV/Diesel hybrid power system. From the simulation results, the proposed system has total Net Present Cost (NPC) and amount of CO 2 as ($995,774; 65.270 tonnes), saves ($716,397; 57.835 tonnes) when compared with the diesel only system ($1,712,171; 123.105 tonnes). A control system for the Hybrid PV-Diesel Energy System with Battery Storage was developed to coordinate when power should be generated by PV panels and when it should be generated by diesel generator. This hybrid system could be applied in any other electrical system.

Proposed generalized models for estimating the reliability of a stand-alone solar photovoltaic power system

A novel sizing method of a standalone photovoltaic system for powering a mobile network base station using a multi-objective wind driven optimization algorithm

Levels of radiofrequency radiations around two global systems for mobile communication (GSM) base stations located in the vicinity of a residential quarter and workplace complex were measured. The effects of the radiofrequency radiations on albino mice placed in exposure cages and located around the base stations over a six months period were carried out. The levels of radiofrequency (RF) radiations around the base stations were found to be between 488.51mV/m to 625.49mV/m compared to 59 mV/m in control stations. The results of the weight change experiment showed that over the 180 days of observation, there was weight gain in the exposed and control mice groups. Statistical comparisons of mean weight changes between exposed mice and control mice showed that there were no significant (P>0.05) differences between the weight of the test animals. The hematological studies revealed an elevation of white blood cell (WBC) counts in mice exposed to RF radiations compared to control group. There was however no significant (P>0.05) difference between the red blood cell counts in the exposed and control mice. There was also no significant (P>0.05) difference in the hemoglobin and glucose levels in the blood of both exposed and control mice groups. The red blood cells in exposed mice were however found to contain a higher number of macrocytes, poikilocytes, polychromatic cells and fewer target cells than the control mice. Histological studies of the heart and kidney of exposed mice showed only slight tissues deformities in kidneys of exposed mice compared to control. The relevance of these findings in setting radiofrequency radiation exposure guidelines and the need for more studies with widely varying biological parameters is very necessary as Nigeria leaps further into the communication age.

This paper discusses the influence of different Radial Basis Function (RBF) in metamodel construction to be applied to 3D aerodynamic wing optimization problems using the Constrained Optimization with Response Surface (CORS) methodology in conjunction with a stochastic Controlled Random Search Algorithm (CRSA). CORS methodology is based on the iterative construction and optimization of response surfaces with a robust search pattern application. In the CORS methodology the response surface may be generate by at least three types of methods: (i) Classical (polynomials and parametric surfaces), (ii) Statistical (K-Nearest, Kriging and Gaussian Processes) and (iii) Advanced (RBF and Neural Network). The response surfaces used in this paper are constructed using six different types of RBF: Gaussian, Hardy’s Multiquadric and Inverse Multiquadric, which depend on a shape parameter, and linear, cubic and thin plate spline, which do not depend on a shape parameter. The RBF’s are directly applied on the response surface construction inside the CORS structure. Thus the choice of a RBF and of a shape parameter (being the case) may influence significantly the methodology efficiency. The CORS methodology is here applied for accelerating the optimization process of wing aerodynamic designs with a solver based on a first order 3D panel method and a 2D boundary layer model. Since the main objective of this paper is of prospective nature, the choice of a relatively low-fidelity flow computation solver is justified. One considers problems of minimizing the aerodynamic coefficient relation (CD/CL) and the inverse of lift coefficient (1/CL). Comparative influence of the RBF choice on the acceleration induced by CORS methodology is investigated taking into account the number of expensive objective function evaluations necessary to find the minimum value in each problem.

Development of flexible grouting material for cement-stabilized macadam base using response surface and genetic algorithm optimization methodologies

A certain degree of machining must be done on hybrid composites (glass and carbon fibres), created by basic manufacturing procedures, so as to achieve close fits and tolerances. End milling is a common method for finishing machined flat plate hybrid composite products, having aerospace, automobile, wind turbine blade and prosthetic applications. This study was performed using, PVD TiAlN coated carbide tools, under dry conditions. Three input parameters, namely nose radius, having two levels, cutting speed and feed rate, having three levels each were considered. Surface roughness parameter Ra was considered as the output performance measure. Taguchi L18 orthogonal array (OA) was applied for the design of experiments. Response surface methodology was adopted to optimize the input performance parameters. A response surface was generated to investigate the effect of input variables and their interactions on the response. From the analysis of the mean effect plot, it was observed that the most significant input parameter on surface roughness was the feed rate. Optimization results revealed that the best surface roughness was observed at a combination of A1B2C1, i.e. nose radius of 1 mm, cutting speed of 94.69 m/min and feed rate of 300 mm/min.KeywordsCarbon fibreHybrid compositeCFRPResponse surface methodologySurface roughness

We are today surrounded almost constantly by high-frequency electromagnetic fields (EMFs) from mobile communications base stations. To date, however, there has been little concern regarding nonthermal effects of EMFs on cognition. In the present study, male and female rats were subjected to continuous far-field exposure to a frequency of 900-MHz (Global System for Mobile Communications [GSM]) or 1.966-GHz (Universal Mobile Telecommunications System [UMTS]) at 0.4 W/kg. Memory performance of adult EMF-exposed and sham-exposed female rats (at 6 months of age) and male rats (at 3 and 6 months of age) was tested using a social discrimination procedure. For this procedure, a target juvenile male was introduced to the subject's home cage for 4 min (Trial 1). After 30 min, the same target animal and a novel juvenile male were simultaneously presented to the subject for 4 min (Trial 2). Differences in sniffing duration to the familiar and novel target rats during Trial 2 were used to assess memory performance. EMF-exposed females exhibited no differences in sniffing duration compared with controls. In contrast, the sniffing durations of EMF-exposed males at 3 months of age were significantly affected. At 6 months of age, GSM-, but not UMTS-, exposed male adults showed a memory performance deficit. These findings provide new insight into the nonthermal effects of long-term high-frequency EMF exposure on memory.

Recent advances in non-gradient based optimization methods (e.g., Genetic Algorithms, Particle Swarm Optimization) enhanced the abilities of discrete, integer, and mixed optimization problems. However, the very nature of non-gradient based algorithms is that the number of analyses required to get to an optimal solution is several orders of magnitude higher than for traditional gradient based optimization methods or response surface optimization methods, when considering continuous problems. Instead of these approaches we propose to use a response surface approximate optimization method modified to work with discrete design variables. In this case whenever it is required to perform the actual analysis of responses for the purpose of fitting a response surface approximation, the design variables will be converted to corresponding discrete values. Two discretization techniques are proposed. We demonstrate that although lacking global search properties like Genetic Algorithms and Particle Swarm Optimization, the discrete response surface optimization provides a computationally efficient way of improving an initial design and getting into a region of an optimum using only discrete points for analysis.

An improved numerical optimization algorithm for sizing and configuration of standalone photo-voltaic system components in Yemen

A battery storage has emerged as the most widely-used storage option, due to its flexible and complementary functionality for renewable energy systems such as solar PV and wind power. In order to ensure the efficient operation of batteries in energy systems, a proper battery model is essential in predicting realistic battery performance under various operating conditions. Accurate knowledge of the state of charge, state of power, and battery efficiency is a necessity for the development of advanced grid management applications. This paper investigates the techno-economic impacts of two battery modelling scenarios on the sizing and optimization of a grid-connected PV-battery system. Scenario 1 is based on a common simple battery model and control strategy which represents the battery status without reflecting dynamic behavior. By contrast, Scenario 2 is based on a complex battery model involving estimation of battery current-voltage characteristics under various operating conditions. A rule-based operational strategy linked to a non-dominated sorting genetic algorithm is further employed for the simulation and multi-objective optimization of a grid-connected hybrid PV-battery system. The battery life cycle cost and the self-sufficiency ratio are analyzed and optimized as objective functions, and battery capacity constitutes as a decision variable. The results show that in order to reach the same self-sufficiency ratio, the optimization of a hybrid energy system based on Scenario 1 leads to solutions with a higher life cycle cost and requiring bigger battery capacity, compared to that of Scenario 2. Moreover, under the same design parameters, the system optimization based on Scenario 2 delivers more power to the end-user, which leads to a higher self-sufficiency ratio compared to when the system is simulated based on Scenario 1. This study proves that an efficient battery model with sufficient accuracy is techno-economically more beneficial, and leads to more accurate battery sizing.

This paper presents the use of a novel approach in assessing the generation reliability of a hybrid mini-grid system (HMS) based on the optimal design result obtained from the HOMER software. A typical Nigerian rural community – Lade II in Kwara State was used as a case study where the energy demand for the residential and commercial loads was 2.5MWh/day and 171kWh/day respectively. The optimized HMS results from HOMER comprising of a solar photovoltaic (PV) array (1.5MW), diesel generators (350kW) and battery storage (1200 units) has a combined least net present cost of $4,909,206 and a levelized electricity tariff of $0.396 per kWh. Contrasting the HMS with a diesel-only system for the community, an approximate 97% reduction in all pollutant emissions was observed. Furthermore, fluctuations in diesel fuel prices, variations in average solar insolation, and variations in the solar PV's capital/replacement costs were utilized in conducting a sensitivity analysis for the HMS. The capacity outage probability table (COPT) was utilized in validating the reliability of the simulation results obtained from HOMER. The HMS was observed to experience a load loss of 0.769MW, 0.594MW & 0.419MW when zero, one and two diesel generator(s) respectively were operational for all of the Solar PV's and Batteries being off-line. The loss of load probability (LOLP), loss of load expectation (LOLE), and total expected load loss (ELL) obtained from the COPT were 5.76 × 10−8, 5.0457 × 10−4 hr/yr and 0.025344Watt respectively. The results show the reliability of the HMS and also depicts a highly economical and feasible hybrid energy system.

ABSTRACTBioactive peptides are small molecular peptides with some physiologically active functions. These peptides have been shown to possess antibacterial, antioxidant, and blood pressure lowering activities. Although walnuts are rich in high-quality plant proteins, the extracted walnut dregs have low utilization by the walnut industry chain. Therefore, the aim of the study was to investigate the nutritional value and antioxidant activity of walnut dregs in order to increase the added value of walnut by-products. Using the response surface methodology, the optimum process parameters of purification and stability for walnut polypeptide liquid were determined as follows: pH 4.5, 8 column/hours (h) column speed and 3:2 ratio of anion to cation. The scavenging reaction rates for hydroxyl radicals and superoxide anion by 3, 5, 10 u ultrafiltration membrane fractionation screening were found to be 73.3% and 64.4%, 66.1% and 58.9%, 59.2%, and 51.6%, respectively. After comparison, walnut polypeptide liquid showed some degree of antioxidant capacity. The stability of walnut polypeptide liquid was optimized by the response surface. Under the homogeneous pressure of 35 Mpa, the use of a certain amount of stabilizers improved the stability of walnut polypeptide liquid. In conclusion, with the addition of additives, the optimum values of parameters for walnut polypeptide liquid obtained using response surface methodology were determined as follows: the ratio of solid to liquid was 15%; the amount of protein sugar was 0.2%; the amount of citric acid was 0.25%; and the addition of walnut powder flavor was 0.15%. Also, the study has provided a theoretical basis for the waste utilization of walnut by-products, and partial support for the intensive processing of the walnut industry chain.

A large amount of radioactive waste resin will be produced in the production and operation of the nuclear industry, which needs to be treated and disposed safely. The microwave-assisted Fenton reaction is used in this study for the degradation of radioactive waste resin, and the response surface method is adopted to optimize and establish the high-efficiency degradation process. The four-factor (pH value, the dosage of FeSO4 and H2O2 reagents, and the microwave power) and three-level response surface method was used to analyze the influence degree of various factors on the experimental results, screening the key factors affecting the degradation effect, and exploring the best process conditions for the experiment. The research results show that based on the response surface optimization scheme, the optimal process conditions for degrading cationic resin are: pH = 1.637, 41.3 mL of 0.02 mol/L FeSO4, 116.1 mL of (30%) H2O2, 438.31 W of microwave power. Under the optimal condition, the cation exchange resin is rapidly degraded within 1 hour, and the COD of degradation solution is as low as 1.04 g/L. The findings indicate that the microwave-assisted Fenton reaction is an effective method to treat the cation exchange resin, and the response surface optimization method is reliable to the research of cationic resin degradation, which is conducive to design the treatment process of radioactive waste resin.