Experimental and Theoretical Investigation of Performance of a Solar Chimney Model Part II: Model Development and Validation

A mathematical model based on the momentum, continuity and energy balance equations was developed to simulate the behavior of the air flow inside the solar chimney system. The model can estimate the power output and performance of solar chimney systems. The developed mathematical model is validated by the experimental data that were collected from small pilot solar chimney; (experiment was presented in part I). Good agreement was obtained between the experimental results and that from the mathematical model. The model can be used to analyze the solar chimney systems and to determine the effect of geometrical parameters such as chimney height and collector diameter on the power output and the efficiency of the system

Optimal Operating Point of a Hydrogen Fueled SOFC Models Using Al-Nour Software

The solid oxide fuel cell (SOFC) is considered extremely suitable for electrical power plant application. Both high temperature (HT) and intermediate temperature (IT) SOFC performances are investigated using models which are built in Aspen customer modeller. Moreover, this paper introduces a new simulation software, called Al-Nour V.1.0-2012 software application. The interface of Al-Nour V.1.0-2012 software was mainly implemented based on the educational theory of User’s Split Attention, that is; the entire software works with only one screen for all operations without any scrolling (user-friendly interface). This application reflects the fact that Al-Nour software does not require the user to have any previous training. The performance of HT-SOFC and IT-SOFC models is evaluated and compared using both software applications . The simulation results show that, the cell voltage value increases by raising the operating pressure, operating temperature, and hydrogen partial pressure. The electrical power output value from the SOFC is increased simultaneously by increasing the current density . Furthermore, the IT-SOFC has a higher cell voltage than the HT-SOFC.

Effect of Full Implementation of Domestic Solar Water Heaters on the Electricity Peak Load in Libya

Electricity plays an important role in the contemporary life, and it has become indispensable nowadays. Reducing the peak electricity load and increasing the load factor have been considered as one of the main tasks that have to be accomplished by both electricity generation-side and demand-side managements.The residential sector of Libya consumes over 31% of the total sold electricity, and 29.8% of that is delivered to the electric water heating load. This is an inefficient way of electricity utilization. Usually, the electricity supplier in Libya used to increase the local generation capacity or import electricity from neighboring countries. Both solutions did not resolve the problem. This work attempts to investigate the effect of replacing electric water heaters in the residential sector of Libya by solar water heaters on reducing the electricity peakload and increasing the load factor. The results show that on average 3% of the peak load demand can be saved. This is equivalent to 149.5 MW of reduced power. The study also revealed that the annual amount of energy saved is up to 2.55TWh, and the load factor is improved by 2% (i.e. from 65% to 67%). This saved energy is equivalent to a power plant with a nominal capacity of 448 MW considering a load factor of 0.65

The Prediction of Solar Radiation for Five Meteorological Stations in Libya Using Adaptive Neuro-Fuzzy Inference System (ANFIS)

The prediction of solar radiation is very important tool in climatology, hydrology and energy applications, as it permits estimating solar data for locations where measurements are not available. In this paper, an adaptive neuro-fuzzy inference system (ANFIS) is presented to predict the monthly global solar radiation on a horizontal surface in Libya. The real meteorological solar radiation data from 5 stations for the period of 1982 - 2009 with diffrent latitudes and longitudes were used in the current study. The data set is divided into two subsets; the fist is used for training and the latter is used for testing the model. (ANFIS) combines fuzzy logic and neural network techniques that are used in order to gain more effiency. The statistical performance parameters such as root mean square error (RMSE), mean absolute percentage error (MAPE) and the coeffient of effiency (E) were calculated to check the adequacy of the model. On the basis of coeffient of effiency, as well as the scatter diagrams and the error modes, the predicted results indicate that the neuro-fuzzy model gives reasonable results: accuracy of about 92% - 96% and the RMSE ranges between 0.22 - 0.35 kW.hr/m2/day

Estimating the Annual Global Solar Radiation In Three Jordanian Cities by Using Air Temperature Data

Estimating solar radiation is an imperative requirement for solar energy development in Jordan. In this paper, a quantitative approach, based on Artifiial Neural Network, was developed for estimating the annual global solar radiation of three Jordanian cities: Amman, Irbid and Aqaba. Thse cities are currently witnessing huge development and increasing demand for energy supply. Using a set of known meteorological parameters, two Artifiial Neural Network (ANN) models with diffrent architectures, called case 1 and case 2, fed with three types of learning algorithms for data training and testing, were designed to identify the optimum conditions for obtaining reliable and accurate prediction of the solar radiation. Th results showed that model case 1 performed generally better in terms of predicting the annual GSR (96%) compared to model case 2 (95%). Furthermore, the algorithms LM and SCG in general, ensured the highest effiency in training and testing the data in the designed models compared to the GDX algorithm. Threfore, model case 1, designed with one of these two algorithms, is selected as the optimal model design that is able to compute with high accuracy the annual solar radiation for the three studied cities.

Energy Saving Potential of Dynamic Lighting Control in Street Lighting Systems in Libya

This paper studies the manner of energy consumption in Libyan street lighting systems and general road section. It also suggests proposal system with two cases of operation for an attempt to apply the energy saving program by adopting an optimum method in order to decrease the demand of energy in this section and to reduce the use of uneconomic equipment.The proposal system in this paper introduces the Light Emitting Diode (LED) street lighting technology to be used instead of traditional luminaries High Pressure Sodium (HPS). The proposed system is divided into two cases. The first case discusses the replacement of traditional luminaries (HPS) with energy saving luminaries (LED), while second case explains how integrating control node (dynamic dimmer) into LED in order to dim output lighting in streets will save more energy.This study reaches a result that a significant amount of energy of %47 (about 1092.23 GWh/year) of total energy consumed in street lighting sector could be saved if first case is applied. Moreover, it suggests that more energy of %58 (about 1380.02 GWh/year) of total energy consumed in the same sector cloud be saved if the second case is adopted.

Low Cost High Altitude Automatic Weather Station Design

When looking at installing a renewable energy generator, you need to be confident of the resource (solar, wind) at your particular location as this affects the energy generated at the selected site. With solar photovoltaic (PV) systems, this can be done by looking at historic data, generally from satellite readings, for the particular latitude. This will yield pretty accurate resource data. However, the wind resource is incredibly variable and depends upon the exact topology of the area. Houses, trees, and valleys all can affect the local wind resource. For this reason, wind speed data is collected at a potential wind turbine installation site. This gives real data which can be used to assess the wind speed. When installing a number of very expensive large wind turbines, one must be very confident about the wind speed data. The data must be robust and reliable and the developer will be willing to spend a lot of money on accurate industrial equipment to have lots of confidence in the data. This project intends to overcome this barrier by providing a low-cost, reusable, open-source wind speed recording unit, which can be left at high altitude in a remote location to record data and help improve the site’s wind speed assessment. We have proposed and developed a low-cost hardware module based on Arduino open source platform, which measures the meteorological data, including air, temperature, relative humidity, wind speed and solar radiation, with two options: The first is the wireless option at which it sends the measured information to Excel spreadsheet running on a PC through wireless link. The second is the data logger option at which it records the measured data to SD card as Excel file with date and time every 10 seconds..

Thermodynamic Study of Operation Properties Effect on Polymer Electrolyte Membrane Fuel Cells (PEM)

The thermodynamic analysis of PEM fuel cell energy production depends on the entropy and enthalpy of reaction with the changing of the operating temperatures that ranges between 50 and 100ºC, the electrical work done will be equal to the Gibbs free energy released. This paper presents a mathematical model of PEM fuel cells, based on physical-chemical procedures of the phenomena occurring inside the fuel cell, and it was theoretically studied the performance at different operation variables and conditions. The C++ program is designed to calculate all thermo-chemical parameters, i.e. enthalpy of formation, Gibbs free energy, work and efficiency for any type of fuel cells. The results are plotted as a function of fuel cell operating temperature. The results shows that the highest value of Gibbs energy is at the lowest operating temperature, and decreases gradually with increasing the temperature, the output voltage is determined by cell’s reversible voltage that arises from potential difference produced by chemical reaction and several voltage losses that occur inside a cell. In addition the results showed that the efficiency of this type of the fuel cells is much higher than the ideal Carnot’s efficiency, it changes between 82% to 85% depends on temperature operation. The heat output (required heat) from the fuel cell increases with increasing the operating temperature, this heat is used for many thermal applications such as buildings space heating.

Validation of Thermal Models for Polycrystalline Photovoltaic Module Under Derna City Climate Conditions

The main objective of the present paper is to compare nine different cell temperature models available in the literature with data measured under real Derna city climatic conditions (a semi arid climate) for month of August. The study focuses on a comparison of nine theoretical models to calculate the cell temperature based on the experimental measurements such as the ambient temperature, irradiance, and wind speed in some of the models. The presently used models are explicit, depending on the easily measurable parameters and of wide applicability. Six statistical quantitative indicators are used to evaluate the cell temperature models analysed, namely, R2, RMSE, RRMSE, MAE, MBE and MARE. The cell temperature correlations presently studied, first order linear models depending on the ambient temperature, solar irradiation incident on the panel and voltage output, provide the most accurate cell temperature estimations at Derna city climatic conditions.

Review on Solar Thermal Electricity in Libya

Libya is facing an increasing deficit in electrical energy supply which needs great efforts to find new and renewable alternative sources of power. Solar thermal electricity is one of the most promising and emerging renewable energy technologies to substitute the conventional fossil fuel systems. A review of the research literature of solar thermal electricity in Libya is presented in this article. The state of the art of these technologies including design, operation principles and global market is demonstrated. Detailed reviews of research activities that have been conducted by Libyan researchers or institutions are presented. It has been found that Libya as a country needs a strategic plan and more research efforts in order to adopt these new technologies and put them in production mode.