N. Abas

Parametric Quantification of Low GWP Refrigerant for Thermosyphon Driven Solar Water Heating System

Abstract Modern lifestyle, growing industrial and economy thrive on energy which is getting expensive over time. Natural convection based systems are getting attraction for their promising heat transfer efficiency and zero energy utilization. Refrigerants having ozone depletion potential (ODP) and high Global Warming Potential (GWP) have been banned or under time bared permission under the Montreal (1987) and Kyoto (1997) protocols. To retrofit and modify existing cooling and heating systems, various natural and synthetic refrigerants are being investigated worldwide. We have devolved a Refrigerant Parametric Quantification (RPQ) method for the choice of optimal refrigerant for thermosyphon driven solar water heaters. A set of 29 refrigerants are simulated Using REFPROP under various temperature and pressure conditions. The optimal parameters of thermosyphon system are identified from governing equations, international environmental and safety protocols. The proposed RPQ method shows most appropriate refrigerant for given temperature range. In the second part, a glass evacuated tube collector is designed; fabricated and tested employing the best refrigerant emerged from a simulation study.

Smart grids: An approach to integrate the renewable energies and efficiently manage the energy system of Pakistan

This paper describes the reasons behind the crisis in energy sector and the actual status of the energy supply demand gap. With old infrastructure and increasing demand for electricity, Pakistan critically needs the addition in the current energy production and also efficient utilization. Pakistan is incapable to fulfil its energy demands, and the energy crisis is damaging the economy growth and we want to efficiently manage the power system in the current crisis scenario. There are challenges to smartly manage the power system and opportunities for new technologies to be implemented. Smart grid technology is the state of the art technology to manage the power system. The main objective of this study is to discuss the role of smart grid to the integration of renewable energies and cut down the energy produced from oil and gas. We discuss the potential of renewable energies and available wireless technologies in Pakistan that can be applied in smart grids along with the proposed techniques to interconnect the national power system and organizations. In this study, we also find the smart grid as the best option and show that how a smart grid can manage the energy system and how this technology can be implemented in this country. We describe the basic building blocks for smart grid technology and offered an approach for applying suitable applications of the smart grid in Pakistan.

Experimental study of earth batteries

We report successful design, construction and operation of an earth battery as an alternate energy source for low power electric supply applications. Different combinations of metallic and non-metallic solid, liquid and gas electrodes were investigated for maximum potential difference. In view of robust and cost effective use of this natural power technology by unskilled village consumers most suitable combinations of the commonly available metals were selected for further detailed characteristic studies. Combinations of Magnesium anode and Coke cathode; Zinc anode and Graphite cathode; Aluminum anode and Carbon cathode; Zinc anode and Copper cathodes gave 2.05, 1.40, 1.10 and 0.9 volts per cell. Typical rated power of a single Zn-Cu cell was measured to be few tens of microamperes. Small power electronic devices such as calculators, electronic watches, baby toys and cell phones and white light LEDs were operated on site. The voltage level was found to increase linearly by connecting multiple earth battery cells in series like commercial lead acid battery. The load current was found to increase by connecting earth cells in parallel. The source current capacities were also found to increase by increasing surface areas of the electrodes. However, single cell voltage was found to remain constant irrespective of the electrode sizes. This paper reports detailed characteristic study of the most cost effective and accessible metal electrodes earth batteries. Operation of earth battery as a free electricity source was demonstrated successfully.

Review of solar thermal water heater simulations using TRNSYS

Worlds 47% energy utilization is consumed on heating, 27% on transportation and 16% on electricity. The large amount of heat energy substantially explains its importance in modern life style. Solar water heaters are getting attraction for zero energy utilization and becoming an essential part of modern buildings around the globe. In this regard, energy simulation softwares are widely used by designers to investigate system efficiency and behavior. These provide us convenient methods and tools to perform energy calculations and power flow analysis. TRNSYS is one of such graphical based multi-purpose softwares to simulate thermal and electrical energy systems. Its standard library includes a significant number of variable components required for simulations. Also, it can be extended to include new mathematical models. This paper presents a concise survey and review on applications of TRNSYS to analyze: Solar thermal water heaters with forced circulation and Thermo-syphon systems using Flat Plate Collectors (FPC), Heat Pipe Evacuated Tube Collectors (HPETC). A comparison between various simulation results relating to system efficiency has been also presented.

A Solar Water Heater for Subzero Temperature Areas

There is a general consensus that prevailing Energy Crises 2050 will lead towards a serious shortage of fossil fuels in near future. Avoiding Global warming and energy crises are two major challenges to be faced in the coming decade. In this scenario, synthetic refrigerants are well known to create global warming and ozone depletion phenomena. Among natural refrigerants, CO2 having favourable properties in terms of heat transfer and thermodynamics, has been chosen as refrigerants in this study. This paper presents an optimal design and implementation of CO2 based solar water heater using evacuated glass tubes for low insulation area like Gilgit-Baltistan. The performance of designed/fabricated system has been measured using Thermosyphon arrangements. Several parameters, i.e. header design, filling pressure and temperature, height of tank, heat exchanger design, pipe size and its material, of this self-sustained energy free system have been thoroughly studied. Further, they have been optimized for the best performance.

Experimental investigation of unidentified helium–neon lasers

The helium–neon (HeNe) laser used to be a staple in every industrial or university lab having anything to do with photonics, as well as in numerous commercial products such as barcode scanners. They are now less common but still essential for many areas of research and education, and may turn up without any documentation. This paper describes an interesting experience of attempting to operate a HeNe laser without any prior information about its input–output specifications. A HeNe tube was encapsulated in a plastic cover with a copper-foil-wrapped power supply jack attached to it. It was like an optoelectronic gadget without any mention of its operating instructions, wiring, or power requirements. This HeNe laser was investigated as part of a research methods course case study. One week’s testing and investigation led us to conclude that the plasma tube was either defective due to mirror misalignment or internal contamination. As a result of this troubleshooting experience, a well-engineered investigation procedure was developed for testing HeNe lasers. A systematic approach helped to prioritize investigation of mirror alignment, mirror coating damage, possible debris inside the cavity, and power supply problems. General guidelines as well as this specific diagnostic experience can be very useful for laser technicians and engineers.

Earthy, solaris and atmospheric energy sources

Earth, sun and atmosphere are the ultimate energy resources. In addition to fossil fuels, earth radiates over 45 TW geothermal energy. Sun radiates about 89 PW energy to earth’s surface. Lunar gravity supplies over 100 GW tidal ocean energy. Accessible energy from geothermal, solar, tides, waves and winds is far more than our current 17 TW energy demand, yet there are new avenues like tornadoes and lightning energies. We have to harness storms to serve humanity rather than destroying it. Fossil fuels and uranium reserves will continue to exist beyond 21st century, yet energy transition from fossil fuels to renewable energy sources is necessary to fight against looming climate changes.

CO 2 Utilization Drivers, Opportunities and Conversion Challenges

Energy, economy, and population scenarios steer the greenhouse gas (GHG) emissions that accelerate the climate change process across the globe. Combustion of fossil fuels and land use patterns annually produce 54 Gt of GHGs with CO 2 ’s share of 40 Gt accelerating its emission in the atmosphere causing 70% rise in the concentration as compared to the level that existed 265 years ago. A steady rise in CO 2 emission caused an increase in the earth’s temperature, which can be decelerated by reducing CO 2 emissions, increasing carbon capture and sequestration; and converting CO 2 into chemicals, fuels and value-added industrial products. Natural solar refinery uses eight to ten photons to convert a CO 2 molecule into glucose and oxygen. Molecular engineering tools offer innovatory chemical, biological, and thermal processes using electrolysis, catalysis, thermolysis, and pyrolysis techniques. This article reviews CO 2 capturing technologies, utilization drivers, conversion barriers, material limitations, and immediate challenges. To demonstrate the use of supercritical CO 2 as a next generation refrigerant (R-744) for domestic, industrial, and commercial heat transfer applications, a gravity driven (thermosiphon) solar water heater is reported.

A model of twenty one lines DFB dye laser

Multiple tunable laser lines were obtained by pumping solution of Rh6G in ethanol (1mM) by five pairs of the second harmonic of a passively Q. switched and mode locked Nd:YAG laser. The time delays among the excitation pulses were varied within coherence length of 1cm. Twenty one equally spaced lines were obtained by pumping dye solution with ten pairs of excitation beams derived from the same source. It was possible to tune the wavelengths by a microcontroller based mirror mounted stage. Number of lasing lines varied from minimum five to maximum twenty one. The wavelength of output lines varied from 540 to 590nm. The pulse lengths were measured, using Hadland Streak Camera, to vary from minimum 10 to maximum 30ps. The experimental results have lead to maturity of a 21-lines model of a distributed feedback dye laser. The dye cell was excited by the 2nd harmonic of a laboratory built passively Q. switched and mode-locked Nd:YAG laser to induce simultaneous temperature phase grating in the dye solution. This work on distributed feedback dye laser is in agreement with most of the published results on semiconductor DFB lasers. Simultaneous operation of 21-lines of slightly varying wavelengths opens a new era of research in biosensors, multiphoton ignition and measurements. This multi-wavelength operation of DFDL is based on mutual couplings of five overwritten dynamic gratings.

Filamentation and discrete supercontinuum generation in dielectric materials

A new method of filamentary discrete lines supercontinuum generation is reported. It is based on distributed feedback dye laser action instead of the conventional propagation of femtosecond pulses through open air or photonic molecules. Novelty of the technique, ease and economy make it attractive for continual spectral lines generation. Although, this work was carried out by pumping dye solution with only six pulses to generate 45 nm wide supercontinuum, consisting of nine distinct coherent lines, but the principle may be extended to any desired spectral range, depending upon the available gain medium and number of pumping pulses. Successful design and operation of multi-wavelength laser source, an off white supercontinuum, using a mode-locked and frequency doubled picosecond Nd:YAG laser is presented to demonstrate filamentation in atmosphere.