Nesrin Ozalp

Development of energy efficiency and management implementation in the Turkish industrial sector

Abstract The importance of energy efficiency was first realized following the two oil crises of the 1970s. The world has trimmed its energy budget by utilizing higher efficiencies, while still growing economically, and has realized the importance of protecting the environment. The main objective of this paper is to investigate the development of industrial energy efficiency and management studies in Turkey up until August 2001. In Turkey, the demand for energy efficiency started in the 1980s. Planned energy conservation activities were first implemented in 1981 by the General Directorate of Electrical Power Resources Survey Administration (called EIE in Turkey). Since 1981, EIE has been conducting these activities. In the beginning of the year 1993, the National Energy Conservation Center (NECC) was established within the body of EIE. EIE/NECC investigated the nationwide potential for energy conservation. The study concluded that the Turkish industrial sector has an annual energy saving potential of approximately 30%. After this study, a regulation on industrial energy efficiency was issued in 1995, followed by two announcements related to designing energy management courses and performing energy audits in 1996 and 1998, respectively. By means of these regulations, the Turkish industrial sector has significantly accelerated efforts in implementing energy efficiency and management studies in the country.

Present status and potential of renewable energy sources in Turkey

The effects on global and environmental air quality of pollutants released into the atmosphere from fossil fuels in power plants provide strong arguments for the development of renewable energy resources. In this regard, the objective of this study is to investigate the present status, the technical potentials, and the regional distribution of renewable energy resources in Turkey. The following resources were taken into consideration: solar energy, wind energy, hydro energy, geothermal energy, biomass, and wave energy. The present study shows that Turkey has extensive renewable energy resources that can be developed as a significant source of energy.The effects on global and environmental air quality of pollutants released into the atmosphere from fossil fuels in power plants provide strong arguments for the development of renewable energy resources. In this regard, the objective of this study is to investigate the present status, the technical potentials, and the regional distribution of renewable energy resources in Turkey. The following resources were taken into consideration: solar energy, wind energy, hydro energy, geothermal energy, biomass, and wave energy. The present study shows that Turkey has extensive renewable energy resources that can be developed as a significant source of energy.

Present status of cogeneration applications in Turkey

In a process plant where there is a simultaneous demand for power and process heat, cogeneration or combined heat and power (CHP) is an attractive means of meeting the energy needs of industry, and it can contribute significantly to the efficient use of energy. The objective of this paper is to investigate many aspects of the present implementation of CHP systems in Turkey, giving private energy investment models. Cogeneration has played, or will play, a significant and increasing role in dictating the energy strategies for Turkey, with plans to satisfy a considerable portion of Turkeys requirements for electricity from cogeneration.

Development of Cogeneration in Turkey

Cogeneration or combined heat and power (CHP) offers an efficient method to support the heat for industrial processes by producing electricity and useful thermal energy from a common energy source. The objective of this paper is to investigate the development of CHP systems in Turkey. For the last few years cogeneration has played a significant part in Turkish energy strategy, with plans to satisfy the considerable portion of Turkeys requirements for electricity from cogeneration. Up until 1994, only four cogeneration plants were operating, representing a total capacity of 30 MWe. As of March 2000, 80 autoproduction (the production of electricity by industrial facilities for their own use in Turkey based on the Turkish Trade Law is called autoproduction) facilities with a total capacity of 2,079 MW were placed in operation. The annual energy produced was 10,848 GWh in 1999, constituting 9.3% of the annual GWh produced in Turkey. The total capacity of autoproducers is expected to grow by 281% by 2005, representing 20% of the total capacity of Turkey.

A CFD study on the effect of carbon particle seeding for the improvement of solar reactor performance

With the increasing concern of CO2 emissions and climate change, efforts have grown to include solar technologies in chemical processes to manufacture products that can be used both as a commodity and as a fuel, such as hydrogen. This study focuses on a technique, referred to as “solar cracking” of natural gas for the co-production of hydrogen and carbon as byproduct with zero emission footprint via the following reaction: CH4 →C(s)+2H2 (g). However, some portion of the incoming solar energy absorbed by the cavity greatly exceeds the surface absorption of the inner walls because of multiple internal reflections. Studies have shown that by seeding the reactor with micron-sized carbon particles, methane conversion improves drastically due to the radiation absorbed by the carbon particles and additional nucleation sites formed by carbon particles for heterogeneous decomposition reaction. This can maintain more heat at the core and can reduce the carbon deposits on the reactor walls. Present study numerically tries to investigate the above fact by tracking carbon particles in a Lagrangian frame-work. Initially, the numerical model is validated qualitatively by comparing the particle deposition on reactor window with the experimental observations. Effect of particle loading, particle emissivity, injection point location, and effect of using different window screening gases on a flow and temperature distribution inside a confined tornado flow reactor are studied. It is observed that the methane conversion substantially increases by particle seeding. The results of this research can be used in thermo-chemical reactor design.Copyright

Numerical and Optical Analysis of Solar Power Level Adaptable Solar Reactor

Solar energy is an abundant renewable energy resource that can be used to provide high process heat necessary to run thermochemical processes for production of various solar fuels and commodities. In a solar reactor, sunlight is concentrated into a receiver through a small opening called the aperture. However, obtaining and maintaining semiconstant high temperatures inside a solar reactor is a challenge. This is because the incident solar radiation can fluctuate depending on the position of the sun and the weather conditions. For fixed aperture size reactors, changes in incident solar flux directly affect the temperature inside the reactor. This paper presents a novel solar reactor with variable aperture mechanism that is designed and manufactured at our lab. Radiation heat transfer analysis of this reactor concept is studied via Monte Carlo (MC) ray tracing. MC ray tracing module is coupled to a steady-state one-dimensional energy equation solver. Energy equation is solved for the wall and gas, accounting for the absorption, emission, and convection. Incoming direct flux values for a typical day are obtained from National Renewable Energy Lab database. Results show that for a perfectly insulated reactor, the average temperature of the working fluid may be kept appreciably constant throughout the day if aperture diameter is varied between 3 cm and 1.5 cm for incoming fluxes starting with 400 W/m2 at 05:12 a.m., reaching peak value of 981 W/m2 at noon, and eventually receiving 400 W/m2 at 6:58 p.m., which can make the solar reactor run about 13 hr continuously at 1500 K semiconstant temperature.

Effect of Cameralike Aperture in Quest for Maintaining Quasi-Constant Radiation Inside a Solar Reactor

Solar reactors can convert intermittent solar radiation into storable chemical energy in the form of fuels that are transportable. In order to use solar energy as a source of high temperature process heat in a solar reactor, incident radiation needs to be concentrated over a small surface area, the inlet of which is called the aperture. The image of the incoming solar radiation over the aperture can be approximated by a Gaussian distribution where the solar radiation inside the reactor varies by the peak value and aperture size. Due to the transient nature of solar energy, there is a critical need for proper control to maximize system efficiency under field conditions. The objective of this paper is to present numerically proven advantages of having a camera-like variable aperture, one that is sensitive to natural variations in solar flux, and having the ability to shrink or enlarge accordingly in order to maintain quasi-constant radiation inside the reactor. Since the internal temperature has a major impact on reactant to product conversion efficiency, by maintaining the temperature constant, process efficiency is kept high. By maintaining the internal temperature despite transient operating conditions, the system can maintain peak performance through a wider insolation range than fixed aperture systems. Our numerical results from optical, thermodynamic, and flow dynamic simulations led us to develop a computational two dimensional heat transfer distribution model inside the reactor in order to validate our optical results. The combined simulation results show that correctly varying the aperture diameter with respect to transient incoming solar flux densities facilitates the maintenance of quasi-constant temperature distributions inside the reactor.

Numerical Study on the Thermal Interaction of Gas-Particle Transport for a Vortex Flow Solar Reactor

Solar reactors, by nature of their high temperature, are nearly experimentally inaccessible. Most instruments capable of measuring fluid flow cannot survive the harsh temperatures inside the reactor. As such, computational fluid dynamics (CFD) has been relied on to provide insight into the flow within the reactor. Because of the size of the computing resources necessary to properly account for all of the physical mechanisms within the solar reactor, the current state of numerical simulations only provide a limited level of insight. The present study provides an analysis of flow behavior and thermal interaction of gas-particle flow for a directly irradiated vortex flow solar reactor. The thermal hydraulics between gas flow and particle has been considered by two way coupled Euler-Lagrange approach. A two band discrete ordinate (DO) model has been considered to solve radiative transport between walls and entrained particles. The effect of main flow, secondary flow, particle loading, particle diameter and residence time are studied to analyze flow physics and heat transfer. Results are presented in terms of static temperature contours, temperature distribution along the center line of the cavity, path lines and particle temperature. It is observed that with the increase in main flow, secondary flow and particle diameter average outlet temperature of the fluid increases, and with the increase in particle loading the outlet temperature decreases. The particle exit temperature is observed to increase with the increase in residence time.© 2010 ASME

A Smart Solar Reactor for Environmentally Clean Chemical Processing

Solar thermal process reactors can convert intermittent solar radiation and reactants into energy dense, storable and transportable chemical fuels. This method uses concentrated solar energy as the source of high temperature process heat for the production of many commodities such as zinc, cadmium, magnesium, hydrogen and carbon with zero or minimal emissions. Transient inefficiencies due to natural fluctuations in solar radiation degrade product throughput in all solar reactors. It is therefore important to design a system that allows the reactor to respond to environmental factors in order to maintain semi-constant temperatures inside the reactor. Maintaining reactor operating conditions stabilizes process efficiency. Previously, the effects of various aperture geometries have been investigated through the use of ray-tracing and discrete ordinance numerical simulations. In this paper, a more complete concept for the aperture mechanism entitled the “sliding variable aperture” is presented. This variable aperture allows the solar reactor to dynamically respond to changing flux conditions. Optical simulations have been carried out in conjunction with a numerical method for determining the output of the reactor with a dynamic aperture and changing flux conditions. Historical weather data was gathered from the National Renewable Energy Laboratory (NREL). Convective losses were modeled based on a desired isothermal temperature and static standard operating environmental temperatures. Results from the optics simulations, reaction kinetics and the heat transfer model were used to find the range for the area of the gap for the aperture mechanism, which resulted with ranges between 13.8 to 52.3 cm for beam normal insolation amounts between approximately 165-1100 in order to maintain a minimum 1500 K internal cavity temperature inside the solar reactor.

Design, Manufacturing and Testing of a Camera-Like Aperture Mechanism for a Solar Reactor

Changes in weather conditions, such as passing clouds, haze, or too sunny etc., result with fluctuation in solar radiation entering a solar reactor. This creates a major problem in solar reactor efficiency. Because: solar reactors must be operated at certain temperatures depending on the required dissociation temperature of the feedstock. For example, natural gas cracking solar reactors require temperatures of about 1500K to produce hydrogen and carbon. Fluctuation in solar radiation due to weather changes creates temperature fluctuation inside the solar reactor preventing from maintaining constant or semi-constant production rate. In this paper, we present our most recent research results toward solving this problem by designing, manufacturing, and testing a camera-like aperture mechanism. With this mechanism, it is possible to achieve semi-constant temperatures inside the solar reactor by adjusting the solar reactor itself against changes in the incoming solar radiation. Results show that when the incoming solar radiation is 5kW, the aperture radius should be 1.8cm to have reactor temperature at 2100K. However, to keep this temperature when the incoming radiation is 7kW, the aperture radius should be 3.2cm. It should be also noted that at lower temperatures, optimum aperture radius converges to one value, which is about 4.7cm.Copyright