Alexandros G. Charalambides

Numerical investigation of VOC levels in the area of petrol stations

In the area of petrol stations several Volatile Organic Compounds (VOCs) leak into the atmosphere due to the evaporation of liquid fuels, especially of gasoline that is predominantly composed of light hydrocarbons. The aim of the present study is to investigate the spatial distribution of various VOCs when leaked into the atmosphere in the area of a petrol station. The study is based on numerical simulations. The effect of wind speed and direction, as well as of air temperature has been studied. Gasoline components of different properties have been studied (e.g. pentane, iso-octane, o-xylene, toluene, benzene), as well as ethanol that is considered a new fuel blend component that can be found in different fractions in new gasoline blends worldwide. The area of flammable cloud near the source of the leak is investigated for various atmospheric conditions taking into account the lower and higher flammable limits of each compound. Lastly, the exposure to gasoline vapour is studied taking into consideration the recommended occupational exposure limits of various organisations.

Assessing Undergraduate University Students' Level of Knowledge, Attitudes and Behaviour Towards Biodiversity: A case study in Cyprus

Biodiversity is a key resource as it provides both goods and services to society. However, humans value these resources differently, especially when biodiversity is exploited for its economic potential; a destruction on a scale rarely seen before. In order to decrease the threats that biodiversity is facing due to human activity, globally (climate change) and locally (economic development), individuals must have fundamental knowledge and exhibit appropriate behaviour towards biodiversity and its values. Nevertheless, the effect of humans knowledge, policies and attitudes towards biodiversitys protection are often limited by insufficient education and public support. A balance between the use of resources and technology, reconciling economic development and the need to maintain biodiversity is a challenge. The current paper looks into the knowledge level, attitudes and behaviour of university students of the Department of Environmental Science and Technology at the Cyprus University of Technology towards biodiversity. The investigation was carried out using a closed format questionnaire on a sample of first- and second-year university students (n = 44), in order to access their perceptions and attitudes towards environmental issues regarding biodiversity. The questionnaire was derived from relevant literature. The test results showed that there are significant differences with regard to the level of knowledge about biodiversity between the two groups. However, no significant differences were found on attitudes and behaviour towards biodiversity. The results have also shown that all students have a positive attitude towards biodiversity, while on the other hand, they find themselves, most of the time, unwilling to engage in environmental behaviour.

Axial fuel stratification of a homogeneous charge compression ignition (HCCI) engine

Homogeneous charge compression ignition (HCCI) combustion is a method of internal engine combustion that incorporates principles from both spark ignition (SI) and compression ignition (CI) engines. The advantages of HCCI combustion are low NOx and soot emissions and high volumetric efficiency. Knocking at high loads is among the disadvantages of HCCI and fuel stratification can offer the possibility of reducing the knocking effect. In this study, infrared (IR) absorption was used to quantify the charge stratification in the engine, and pressure traces and fast camera images were acquired to investigate any variations between a strongly and a weakly stratified mixture.

The effect of axial charge stratification and exhaust gases on combustion ‘development’ in a homogeneous charge compression ignition engine

Abstract A high-swirl low-compression-ratio, optically accessed engine that was able to produce a stratified charge was used to investigate the differences in homogeneous charge compression ignition (HCCI) combustion and in the propagation of the autoignition front between a non-stratified and a stratified charge. Natural-light images were acquired using a fast camera to visualize HCCI combustion and to quantify the location of autoignition, the apparent ‘propagation speed’ of the autoignition front, and its variations between closed-valve injection timing (leading to a nearly homogeneous charge) and open-valve injection timing (leading to a strongly axially stratified charge), owing to temperature inhomogeneities that were introduced by utilizing a camshaft which allowed 40 per cent internal exhaust gas recirculation (iEGR). Experimental results show that, in the case without exhaust gas recirculation (EGR) and with closed-valve injection timing, autoignition started under the primary intake valve near the cylinder wall, while, in the case without EGR and with open-valve injection timing, autoignition started between the exhaust valve and the secondary intake valve, closer to the centre of the piston. With 40 per cent iEGR and closed-valve injection timing, autoignition started between the exhaust valve and the primary intake valve near the cylinder wall. These differences can be explained by the difference in the location of hot gases due to the injection timing or due to iEGR. Finally, without EGR, a ‘uniform’ autoignition front of HCCI combustion from the original sites of autoignition was observed compared with a more ‘random development’ of the autoignition front with 40 per cent iEGR. Strong local inhomogeneities (possibly a very rich mixture at a low temperature) could be present with 40 per cent iEGR.

A Payoff-Based Learning Approach to Cooperative Environmental Monitoring for PTZ Visual Sensor Networks

This paper addresses cooperative environmental monitoring for Pan-Tilt-Zoom (PTZ) visual sensor networks. In particular, we investigate the optimal monitoring problem whose objective function value is intertwined with the uncertain state of the physical world. In addition, due to the large volume of vision data, it is desired for each sensor to execute processing through local computation and communication. To address these issues, we present a distributed solution to the problem based on game theoretic cooperative control and payoff-based learning. At the first stage, a utility function is designed so that the resulting game constitutes a potential game with potential function equal to the group objective function, where the designed utility is shown to be computable through local image processing and communication. Then, we present a payoff-based learning algorithm so that the sensors are led to the global objective function maximizers without using any prior information on the environmental state. Finally, we run experiments to demonstrate the effectiveness of the present approach.

Schlieren-based temperature measurement inside the cylinder of an optical spark ignition and homogeneous charge compression ignition engine

Schlieren [Schlieren and Shadowgraphy Techniques (McGraw-Hill, 2001); Optics of Flames (Butterworths, 1963)] is a non-intrusive technique that can be used to detect density variations in a medium, and thus, under constant pressure and mixture concentration conditions, measure whole-field temperature distributions. The objective of the current work was to design a schlieren system to measure line-of-sight (LOS)-averaged temperature distribution with the final aim to determine the temperature distribution inside the cylinder of internal combustion (IC) engines. In a preliminary step, we assess theoretically the errors arising from the data reduction used to determine temperature from a schlieren measurement and find that the total error, random and systematic, is less than 3% for typical conditions encountered in the present experiments. A Z-type, curved-mirror schlieren system was used to measure the temperature distribution from a hot air jet in an open air environment in order to evaluate the method. Using the Abel transform, the radial distribution of the temperature was reconstructed from the LOS measurements. There was good agreement in the peak temperature between the reconstructed schlieren and thermocouple measurements. Experiments were then conducted in a four-stroke, single-cylinder, optical spark ignition engine with a four-valve, pentroof-type cylinder head to measure the temperature distribution of the reaction zone of an iso-octane-air mixture. The engine optical windows were designed to produce parallel rays and allow accurate application of the technique. The feasibility of the method to measure temperature distributions in IC engines was evaluated with simulations of the deflection angle combined with equilibrium chemistry calculations that estimated the temperature of the reaction zone at the position of maximum ray deflection as recorded in a schlieren image. Further simulations showed that the effects of exhaust gas recirculation and air-to-fuel ratio on the schlieren images were minimal under engine conditions compared to the temperature effect. At 20 crank angle degrees before top dead center (i.e., 20 crank angle degrees after ignition timing), the measured temperature of the flame front was in agreement with the simulations (730-1320 K depending on the shape of the flame front). Furthermore, the schlieren images identified the presence of hot gases ahead of the reaction zone due to diffusion and showed that there were no hot spots in the unburned mixture.

Monitoring Cloud Motion in Cyprus for Solar Irradiance Prediction

Solar Energy is the feedstock for various applications of renewable energy sources; thus, the knowledge of the intensity of the incident solar irradiance is essential for monitoring the performance of such systems. The major unpredictable factor in defining the solar irradiance and the performance of solar systems is the presence of clouds in the sky. So far, various researchers proposed several models to correlate solar irradiance to cloud coverage and cloud type. The present work describes the development of a simple method for cloud detection and computation of short-term cloud motion. The minimum accuracy of the model was 95% for the prediction of the cloud location seven timesteps in advance with only three cloud images processed. When including the dimensions of the cloud to the accuracy calculation, the minimum accuracy was 88%.

Homogenous Charge Compression Ignition (HCCI) Engines

With stricter regulations imposed by the European Union and various governments, it is not surprising that the automotive industry is continuously looking for alternatives to Spark Ignition (SI) and Compression Ignition (CI) Internal Combustion (IC) engines. A promising alternative is Homogeneous Charge Compression Ignition (HCCI) engines that benefit from low emissions of Nitrogen Oxides (NOx) and soot and high volumetric efficiency. In an IC engine, HCCI combus‐ tion can the achieved by premixing the air-fuel mixture (either in the manifold or by early Direct Injection (DI) – like in a SI engine) and compressing it until the temperature is high enough for autoignition to occur (like in a CI engine). However, HCCI enignes have a limited operating range, where, at high loads and speeds, the rates of heat release and pressure rise increase leading to knocking and at low loads, misfire may occur. Thus, a global investigation is being undertaken to examine the various parameters that effect HCCI combustion.

Monitoring Cloud Coverage in Cyprus for Solar Irradiance Prediction

The penetration and acceptance of Renewable Energy Sources has already taken place in our lives. Solar Energy is the feedstock for various applications of Renewable Energy Systems (RES), thus, the knowledge of the intensity of the incident solar irradiance is essential for monitoring the performance of such systems. The only unpredictable factor in defining the solar irradiance and the performance of the systems is clouds. So far, various researchers proposed several models for the estimation of solar irradiance in correlation to cloud coverage and cloud type. The present work describes the development of a simple method for cloud detection and computation of short-term cloud motion using a Nikon D3100 camera with a 18–55 mm VR lens, positioned on a tripod in Limassol, Cyprus. The method used for distinguishing clouds from the sky is the “Red-Blue threshold”. Additionally, the results of the cloud distinction are used to calculate the future position of clouds. The developed methodology will provide a useful tool for researchers that want to focus on the effect of small local clouds on the energy production of their solar RES. The maximum error in our model was 12% for the prediction of the cloud location eight time steps in advance with only two cloud images processed.

The impact of Energy Performance Certificates on building deep energy renovation targets

ABSTRACT The purpose of this paper is to investigate the effect of Energy Performance Certificates (EPCs) on the renovation of buildings. Thus, through the European project ENERFUND, 2 online web-based surveys were conducted in 12 countries of the European Union. It was shown that the results varied significantly both between countries and age groups and, that, on average, EPCs did play a role both in renovation decisions and whether to rent/buy a certain flat. In addition, this paper presents major key drivers and parameters related to energy renovation investment mobilisation and suggests actions that can contribute to the promotion of investments for deep energy renovation of buildings. Furthermore, it highlights potential benefits and effectiveness of using retrofitting online tools, such as the ENERFUND tool, pinpoints market failures in the building sector and provides suggestions on increasing the deep energy renovation market in Europe.