Abstract: A hybrid energy system is a combination of renewable energy sources with back up, as well as a storage system used to respond to given load energy requirements. Given that the electrical output of each renewable source is fluctuating with changes in weather conditions, and since the load demand also varies with time; one of the main attributes of hybrid systems is to be able to respond to the load demand at any time by optimally controlling each energy source, storage and back-up system. The induced optimization problem is to compute the optimal operation control of the system with the aim of minimizing operation costs while efficiently and reliably responding to the load energy requirement. Current optimization research and development on hybrid systems are mainly focusing on the sizing aspect. Thus, the aim of this paper is to report on the state-of-the-art of optimal operation control of hybrid renewable energy systems. This paper also discusses different challenges encountered, as well as future developments that can help in improving the optimal operation control of hybrid renewable energy systems.
Abstract: Enterprises need a strategic plan to retain their skillful employees and provide their career management, sustain their existence, to have growth and leadership qualities, to reach the objectives to increase the value of the enterprise and to not to be affected from changing demographic structure. In the cases when the long term career expectations of skillful employees are in integrity with the enterprise’s interests, skill management process is directly related to the career management. With a long term plan, the enterprises should cover the labor force need that may arise in the future by using systematic career development programs and be prepared against developments for all times. Skill management is considered as a practice with which career mobility is planned for the skillful employee to be prepared for high level positions. Career planning is the planning of an employee’s progress or promotion within an organization for which he works by developing his knowledge, skills, abilities and motives. Career planning is considered as an individual’s planning his future and the position which he wants to have, the area which he want to work in, the objectives which he want to reach. With the aim of contributing the abovementioned discussion process, career management concept and its perception manner are examined in this study in a comparative manner.
Abstract: Recent articles have addressed the problem to construct the confidence intervals for the mean of a normal distribution where the parameter space is restricted, see for example Wang [Confidence intervals for the mean of a normal distribution with restricted parameter space. Journal of Statistical Computation and Simulation, Vol. 78, No. 9, 2008, 829–841.], we derived, in this paper, analytic expressions of the coverage probability and the expected length of confidence interval for the normal mean when the whole parameter space is bounded. We also construct the confidence interval for the normal variance with restricted parameter for the first time and its coverage probability and expected length are also mathematically derived. As a result, one can use these criteria to assess the confidence interval for the normal mean and variance when the parameter space is restricted without the back up from simulation experiments.
Abstract: Batteries and fuel cells contain a great potential to back up severe photovoltaic power fluctuations under inclement weather conditions. In this paper comparison between batteries and fuel cells is carried out in detail only for their PV power backup options, so their common attributes and different attributes is discussed. Then, the common and different attributes are compared; accordingly, the fuel cell is selected as the backup of Photovoltaic system. Finally, environmental evaluation of the selected hybrid plant was made in terms of plant-s land requirement and lifetime CO2 emissions, and then compared with that of the conventional fossilfuel power generating forms.