Birol Kılkış

Flow and Performance Characteristics of a Double-Blade Hydrofoil

While our planet is rapidly approaching an environmental crisis under the dominant use of depleting fossil fuels, the need for exploiting all forms of new, small carbon foot-print, renewable, and clean energy resources are increasing in the same proportion. Therefore, the need for exploring all types of clean energy resources that the world has- some of which might have not attracted sufficient attention before- is essential in order to implement sufficient, efficient, and widely use all them. In this respect, operational effectiveness of the wind and hydrokinetic turbines depend on the performance of the airfoils chosen. Using double-blade airfoils in the wind and hydrokinetic turbines, minimum wind and hydrokinetic flow velocities to produce meaningful and practical mechanical power reduces to 3- 4 m /s for wind turbines and 1-1.5 m/s or less for hydrokinetic turbines. Consequently, double-blade hydrofoils may re-define the potentials of wind power and hydrokinetic power of the countries in positive manner.

Performance Analysis of a Hydrofoil with and without Leading Edge Slat

Operational effectiveness of the wind and hydrokinetic turbines depend on the performance of the airfoils chosen. Standard airfoils historically used for wind and hydrokinetic turbines had and have the maximum lift coefficients of about 1.3 at the stall angle of attack, which is about 12o. At these conditions, the minimum flow velocities to generate electric power are about 7 m/s and 3 m/s for wind turbine and hydrokinetic turbine, respectively. Using leading edge slat, the fluid dynamics governing the flow field eliminates the separation bubble by the injection of the high momentum fluid through the slat over the main airfoil-by meaning of the flow control delays the stall up to an angle of attack of 20o, with a maximum lift coefficient of 2.2. In this study, NACA 2415 was chosen as a representative of hydrofoils while NACA 22 and NACA 97, were chosen as slat profiles, respectively. This flow has been numerically simulated by FLUENT, employing the Realizable k-e turbulence model. In the design of the wind and hydrokinetic turbines, the performance of the airfoils presented by aerodynamics CL = f (a,d), CD = f (a,d) and CL/CD = f (a,d) are the basic parameters. In this paper, optimum values of the angle of attack, slat angle and clearance space between slat and main airfoil leading to maximum lift and minimum drag, and consequently to maximum CL/CD have been numerically determined. Hence, using airfoil and hydrofoil with leading edge slat in the wind and hydrokinetic turbines, minimum wind and hydrokinetic flow velocities to produce meaningful and practical mechanical power reduces to 3-4 m /s for wind turbines and 1-1.5 m/s or less for hydrokinetic turbines. Consequently, using hydrofoil with leading edge slat may re-define the potentials of wind power and hydrokinetic power potential of the countries in the positive manner.

Exergetic Optimization of Generated Electric Power Split in a Heat Pump Coupled Poly-Generation System

This study analyzes environmental, energy, and economical benefits of a ground source heat pump coupled poly-generation system by incorporating exergy into the energy efficiency analysis. Two additional terms, namely the rational exergy efficiency and the coefficient of performance were introduced to the primary energy savings equation in the European Union Directive 2004/8/EC. Based on the new equation, an optimization algorithm was developed, which can quantify the environmental, energy and economy benefits of any poly-generation system in a broader extent and scope. This algorithm was used to investigate the factors affecting the optimum split of the power generated by a poly-generation system between the heat pump and the customer. A base system was analyzed, which consists of a ground-source heat pump (GSHP) and a combined heat and power (CHP) system. Results show that any increase in the split in favor of the heat pump boosts the primary energy savings potential and thus CO2 emissions reducing potential while the pay-back period of the system is reduced. When all the constraints, including electricity and fuel costs in the energy market are taken into account, a one-to-three split seems to be optimal for many practical applications. It is concluded that benefits of CHP may be enhanced by GSHP coupling pending a careful exergy balance analysis between the resource supply and the application demand. This paper provides the fundamentals of the algorithm and discusses that a win-win-win situation among the environment, energy, and economy is feasible, most importantly, from the global warming perspective.© 2007 ASME

A road map for emerging low-exergy HVAC systems

An exergy-conscious life cycle costing algorithm was developed. This algorithm establishes a reference tool to compare conventional air conditioning systems with alternative HVAC systems, which can directly operate with low-exergy alternative energy resources. The cost of exergy waste in conventional heating, ventilating, and air-conditioning systems (HVAC) is included in terms of the difference between energy supply and HVAC operation temperatures. In order to establish a robust road map for a solution, this paper introduces a composite radiant wall panel system, which optimally integrates HVAC functions at moderate temperatures without any modification or add-on equipment.

Parametric Analysis of Pumped Storage Hydropower-Coupled Wind Turbine Plants

The concept of a hybrid system consisting of a wind turbine plant and a pumped storage hydropower plant is a promising idea with respect to a number of important factors. Wind turbine plant power output has a fluctuating and interrupted nature, and the penetration of the electrical energy to the grid usually poses problems to the steady operation of the system. Pumped storage hydropower is a mature technology in the energy storage sector. Pumped storage hydropower has advantages compared to other energy storage technologies such as CAES, batteries, etc. due to its short discharge time, high energy storage capacities, and high power output. The first objective of this study is to time-shift the power output of the wind turbine plant to the peak-demand periods by means of storage and thus realizing increase in the penetration level to the grid. The second objective is to obtain a more stable power output from the wind turbine plant that inevitably has a variable power output. A 1-year operation simulation of the hybrid system was carried out under peak tariff strategy within the scope of these two objectives. An operation simulation was also made covering only the wind turbine plant with same power output data and same demand strategy and the results were compared. Without storage, the wind turbine plant feeds 6,350.30 MW h of electrical energy into the grid; this value increases to 7,656.00 MW h for the hybrid system, and this means that there is 17.05 % increase in penetration and the system is technically applicable for the first objective. Annual stable power output ratio that shows the fulfillment of demand is approximately 72.49 % for wind turbine plant without storage, and this value is approximately 87.40 % for the hybrid system. This means that there is a 14.91 % increase and that the system is technically applicable for the second objective. This paper provides the details of the year-long analysis, draws generalized conclusions, and provides recommendations for future studies.

An exergetic approach to the age of universe

Recent finding by Bond et al. (2013) about the age of the star HD 140283 (14.46 ± 0.8 Gyr) requires us to reconsider the estimates about the age of the universe, namely 13.817 ± 0.048 Gyr. Their conflicting result is analytically supported by the paper in Int. J. Exergy by Kilkis (2004). This paper, which introduced the Radiating Universe Model (RUM) with exergy flow to an infinitely-sized thermal bath at 0 K, predicted that the age of the universe is 14.885 ± 0.040 Gyr. It further calculated that Hubble constant is 65.7 km s–1Mpc–1 and the expansion of the universe has been accelerating since the cosmic age of 4.4 Gyr due to a positive, time dependent cosmological number that is slightly decreasing and presently it is 8.8 × 10–36 s–2. The exergy flow rate, solved by the lumped-capacitance method, changes with the square of cosmic time and is currently 1.224 × 1050 erg·s–1.

A simplistic thermal model for solving the exergy flow of the universe with continuous functions of cosmological parameters

A new thermo-mathematical model of the universe presented in this paper solves the large-scale cosmological parameters as continuous functions of the cosmic age and establishes a composite correlation among them. The universe is assumed to be thermally radiating to an infinitely large thermal bath at 0 K. This model permits and enables to calculate the exergy flow from the universe, which may explain the currently accelerating rate of expansion of the universe and the preceding decelerating phase. Calculations predicted the present time Hubble constant to be 65.7km s-1 Mpc-1 and the cosmic age to be 14.9 Gyr. The same calculations showed that the expansion of the universe has been accelerating since the cosmic age of 4.4 Gyr due to a positive, time dependent cosmological number whose present magnitude is 8.8x10-36 s-2, and it is decreasing. This Model predicts that there is an exergy flow from the universe, which diminishes in the infinite size of the thermal bath.