Zuhal Oktay

Investigation of some renewable energy and exergy parameters for two Geothermal District Heating Systems

In this study, three new exergy parameters, namely total exergy destruction ratio, component exergy destruction ratio and dimensionless exergy destruction are introduced in addition to energetic renewability ratio, exergetic renewability ratio, energetic reinjection ratio and exergetic reinjection ratio, and compared for Edremit and Bigadic Geothermal District Heating Systems (GDHSs) based on their actual data. The respective daily graphs of these parameters are presented. Also, regression analyses using the actual data are performed to obtain some correlations for practical use. In brief, these parameters help us to identify the degree of renewability and other aspects and provide some insights.

Utilization of Olive Cake as a Potential Energy Source in Turkey

With the energy picture getting worse every day, it is now desirable to search for alternative energy sources. This has led to renewed interest in olive cake (OC) as an alternative energy source in Turkey due to some of its advantages, such as negligible sulfur content, reducing environmental impact, low cost compared to fossil fuels, problem-free storage, and lack of transportation requirements if used in an olive oil production facility. OC is a byproduct of olive oil production and is a solid material consisting of seed particles and the fleshy parts of olives. The Mediterranean region represents 98% of the worlds olive tree population. In this regard, Turkey is among the top 5 main olive oil-producing countries in the world. The main objective of the present study is to investigate the potential and utilization of OC in the country. It is estimated that over 360,000 tons of OC, corresponding to an average of 150,000 tons of oil equivalent (toe), were produced in the 2000–2001 season in Turkey. Suitable combustion systems, such as fluidized bed systems, stoker fed from the bottom with secondary air supply, etc., should be used for efficient energy production from the OC. There are no limiting values related to emissions for OC in the Turkish regulations of air quality yet. There are, however, some studies being conducted by the Ministry of Environment for the determination of these limiting values. In light of the present study, it may be concluded that OC is a very promising source of energy in Turkey.

Investigation of effect of varying dead-state temperatures on energy and exergy efficiencies of a Raw Mill process in a cement plant

Dead-state temperature directly affects the exergy efficiency of thermal systems. The main objectives of the present study are twofold, namely, to investigate the effects of varying dead-state temperatures on the energy and exergy analyses of a Raw Mill in a cement plant; to examine the sensitivity of the energy and exergy analyses results, calculated according to the varying dead-state temperatures. The exergy efficiency values ranged from 44.5% to 18.4% at varying dead-state temperature values between −18°C and 41°C. The sensitivity analyses results have indicated that varying dead-state temperatures have an effect on the exergy efficiency.

Olive cake as a biomass fuel for energy production

Olive cake (OC) is a by-product of olive oil production and is a solid material consisting of seed particles and the fleshy parts of olive. The Mediterranean region represents 98% of the worlds olive tree population, and Turkey is among the top five main olive oil producer countries around the world. The main objective of the present study is to investigate the potential and utilization of olive cake (OC) in the country. It is estimated that over 360,000 tons of OC, corresponding to an average of 150,000 tons of oil equivalent (toe), were produced in the season of 2000–2001 in Turkey. From the combustion experiments performed in the conventional OC-fired boilers in the country, the values for CO-emissions were found to vary from 1,800 to 10,000 mg/m 3 . Suitable combustion systems, such as fluidized bed systems, stoker fed from the bottom with secondary air supply, etc., should be used for efficient energy production from the OC. Determination of values of the flue gas can be used in calculating for heating surfaces.

Energy and exergy analyses in a thermal process of a production line for a cement factory and applications

The objective of this study is to determine the actual energy losses by performing energy and exergy analyses and to evaluate energy and exergy efficiency in each process for the cement factory. In these analyses, for each process energy and exergy diagrams have been constituted on the production line. Efficiencies (energy/exergetic) of the processes for the raw mill, the rotary kiln, the trass mill and the coal mill on the production line have been found as 84%/25%, 61%/49%, 74%/13%, 74%/18%, respectively. In addition, some suggestions concerning the reduction of energy losses have been proposed.

The techno-economic and environmental aspects of a hybrid PV-diesel-battery power system for remote farm houses

In this study, the solar radiation data of Balikesir in Turkey are analysed to assess the techno-economic viability and environmental performance of a hybrid Photovoltaic (PV)-diesel-battery system to meet the load requirements of a typical remote farm house. Several aspects of the system are studied through the Cost of Energy (CoE), the operational hours of diesel generator, unmet load, excess electricity generation, percentage of fuel savings, etc. The CoE for this kind of hybrid system is found to be 1.245 US

Investigation of a hybrid solar and geothermal driven absorption cooling system for district applications

/kWh. Simulations are performed for three cases (diesel only, PV-diesel and PV-diesel-battery). It is found that a diesel-only system produces 63 900 kWh of electricity and 69.7 tonnes of CO2, 13.0 kg of PM, 1.53 tonnes of NOx emissions per year. Using PV-diesel and PV-diesel-battery systems helps reduce the emissions for CO2 to 61.0 and 42.0 tonnes, for PM to 11.4 and 7.83 kg and for NOx to 1.34 and 0.92 tonnes, respectively. The diesel-only system is more economical if the fuel price remains below US

Impact assessment of CO2 emissions caused by exergy losses in the cement sector

2/L. Otherwise, PV-diesel and PV-diesel-battery systems become more cost-effective. Also, the environmental impact improvement factor is found as 0.127 and 0.399 for CO2, 0.123 and 0.397 for PM and 0.124 and 0.398 for NOx for both PV-diesel and PV-diesel-battery systems, respectively.

A case study of hybrid wind-solar power system for reduction of CO 2 emissions

In this paper, a new hybrid geothermal and solar driven absorption cooling system (ACS) is proposed for low–temperature district energy applications. Two approaches are proposed in this study, namely: a) a new model for determining the specific entropy values of LiBr–water solution and (b) two new energetic and exergetic parameters, namely geothermal contribution index and solar contribution index. A feasibility study of incorporating a solar driven ACS into Bigadic Geothermal District Heating System is considered and investigated in this regard. Some parametric studies are conducted to highlight the importance of the present study and make a practical illustration.

Investigating the Exergetic and Environmental Effects of Subcooling and Superheating Processes on the Performance of Direct Expansion Systems

In this study, global effects caused by exergetic inefficiency are examined for rotary kiln of the cement plant. For this purpose, a rotary kiln process of a cement plant in Turkey is modelled, and the annual operation data of this process is analysed. As a first step, an exergy analysis is carried out for all of the thermal processes of the cement plant. Then exergy losses and carbon dioxide (CO2) emissions of the rotary kiln process taken exemplary according to annual dead state temperature changes are determined. Annual averages of the exergy efficiency of the kiln and its exergetic improvement potential are found as 48.5% and 110.58 GJ/h, respectively. In this system, CO2 emissions caused by exergetic losses are calculated for the coal mixture and the natural gas as an average of 38,004 kg/h and 12,668 kg/h, respectively. At the end of the study, some suggestions concerning reduction of the global effects for these systems are made.