Browsing by Author "Kilkis, Birol"

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Determination of Heat Transfer Coefficient Between Heated Floor and Space Using the Principles of ANSI/ASHRAE Standard 138 Test Chamber
(2017) Evren, M. Fatih; Ozsunar, Abuzer; Biyikoglu, Atilla; Kilkis, Birol; 0000-0003-2580-3910; A-5233-2016; A-5233-2016
In this study, heat transfer coefficients for radiant floor heating systems were investigated in a special test chamber that is one of the very first implementations of ANSI/ASHRAE Standard 138 in the world. Radiant systems offer high energy- and exergy-efficient sensible heating and cooling potential. These systems can be directly coupled with low enthalpy, renewable, or waste heat resources. Heat transfer coefficients are important design parameters for radiant systems that effect the heat transfer capacity of the heated/cooled surface to the indoors. In this study, radiant, convective, and total heat transfer coefficients for radiant floor heating were investigated experimentally. Experiments were conducted in a special test chamber that was established according to ANSI/ASHRAE Standard 138 with minor differences. The test chamber dimensions are 2.74 x 2.25 x 2.45 m (8.99 x 7.38 x 8.04 ft) and there are no floor coverings during the test. Coefficients were determined through two difference methods. Heat fluxes from the heated floor that calculated via both methods and obtained from the "Design Graph for Sensible Heating and Cooling with Floor and Ceiling" in ASHRAE Handbook-HVAC Systems and Equipment (ASHRAE 2008). According to the experimental results, total heat transfer coefficients for the radiant heating system were obtained between 8.8 and 12.1 W/m(2)K (1.43 and 2.13 Btu/h.ft(2).degrees F).
Ecological Sanitation, Organic Animal Farm, and Cogeneration: Closing the Loop in Achieving Sustainable Development-A Concept Study with On-Site Biogas Fueled Trigeneration Retrofit in A 900-Bed University Hospital
(2016) Taseli, Basak K.; Kilkis, Birol; 0000-0003-2580-3910; AAJ-2321-2020
Healthcare facilities mostly consume natural gas or fuel oil, utilize grid power, and are the second most energy intensive sector in the USA. Besides their high fossil fuel expenditures, hospital buildings generate large amounts of plumbing wastes and others, such that they are the largest producer of GHG emissions in the building sector. Energy costs are consuming up to 15% of their annual profits. In this paper the overall environmental and economic problems that may be associated especially with large healthcare facilities are addressed by showing ways to convert their energy and environmental disadvantages into advantages. In this respect, a concept study with ecological sanitation and formation of an energy, water, food, and education nexus by primarily employing a trigeneration system operating with biogas at an optimum fuel share with natural gas for retrofitting an existing 900-bed University hospital is presented. This case study covers two scenarios. The first scenario is the base scenario, which utilizes three trigeneration engines, with one 1,25 MWe, and two 2,2 MWe capacity each, all running on natural gas with a total capacity of 5,65 MWe. The second scenario includes three stages. The first stage mixes natural gas with biogas, which is to be produced on-site by primarily using plumbing wastes, for driving the 1,25 MWe engine, which satisfies the constant base load of the hospital for 24h a day. The second stage produces biogas by making use of the widely available surrounding free land of the hospital in a new eco-farm development and replaces the fuel input of the first 2,2 MWe engine, which operates 16 h a day on average. In the third stage the second trigeneration unit with 2,2 MWe capacity remains on natural gas fuel input and operates approximately 8 h a day (peaking engine). Both scenarios have an absorption cooling system with the same capacity and an 8 MWc-h ice tank. This common base of identical power, heat, and cold capacities was aimed to independently focus on the environmental and economic benefits of biogas substitution covering a ten-year operational period. The next system for stage two involves a new organic 6000 livestock-animal organic farm and a dairy factory to be owned by the University, which completes the food, water, energy, education and environment nexus and serves as a full-scale hands-on farm for the Department of Agriculture students and provide an R&D platform. It has been shown that such an application closes the loop towards sustain ability. The organic venture is expected to have a large economic impact and important contributions also on the dietary needs of the patients. The organic farm is envisioned to incorporate greenhouses, wind, and solar farms. Yet this study only covers the impact of the biogas supply to the trigeneration system: CO2 emissions from biogas generation is assumed to be captured and utilized for dry ice production. Analyses show that the additional cost of on-site biogas anaerobic digester and its ancillaries of the. first-stage (1,25 MWe) may pay back themselves in four years. The corresponding prediction for the second stage biogas trigeneration system with biogas fuel (2,2 MWe) is also four years. Total reduction in CO2 emissions attributable to the biogas conversion of the trigeneration system is 161558,2 t CO2 over a ten-year period, taking into account the additional reductions due to improvements in rational exergy management of the energy resources. The net total savings from biogas conversion in two stages is expected to be about 4 M(sic) for a ten-year period. (C) 2016 Elsevier B.V. All rights reserved.
Energy Consumption and CO2 Emission Responsibilities of Terminal Buildings: A Case Study for The Future Istanbul International Airport
(2014) Kilkis, Birol; https://orcid.org/0000-0003-2580-3910; AAJ-2321-2020
Airport terminal buildings are used to be treated as stand-alone buildings for their energy performance. Previous studies in the literature fall short of recognizing functional and physical relations of terminal buildings with landside and airside airport operations. In order to avoid these shortcomings, this paper extends the terminal building energy performance analysis to a broader context and expands the analysis envelope to expose the true impact of a terminal building on energy consumption and the combined emissions that it is responsible for. In this respect, this study investigates whether a green terminal building in a new airport planned for the city of Istanbul with an annual 150 million passenger capacity may off-set the loss of CO2 sequestration potential from cutting at least 657000 trees for the airport construction or not. Additional CO2 emissions corresponding to the estimated longer approach and climb out flights due to the unfavorable site selection have also been considered. This article compares a business as usual type of terminal building with four green terminal building scenarios having different CO2 emission reduction potentials. The first-law and the second-law analysis of thermodynamics have shown that constructing a green terminal building complex may not offset its CO2 emissions responsibility unless a very intensive re-forestation activity is implemented and the site is properly re-selected. As a result, this study has exemplified the essential boundaries for energy consumption analysis envelope for an airport terminal building and its true emissions responsibility. (C) 2014 Elsevier B.V. All rights reserved.
Exergetic Comparison of Wind Energy Storage with Ice Making Cycle Versus Mini-Hydrogen Economy Cycle in Off-Grid District Cooling
(2017) Kilkis, Birol; 0000-0003-2580-3910; AAJ-2321-2020
For the feasible and continuous utilization of intermittent wind and solar energy sources for electricity generation in district energy systems in hot-climates, where cooling loads are dominant, ice storage maybe an option. In this study, the rationality of the ice storage system for wind energy was investigated using the Rational Exergy Management Model, REMM for two options and compared with a base scenario, which comprises a wind turbine system, grid connection, conventional chillers, and the district cooling system. The main objective is to minimize exergy destructions and thus to improve the exergy performance. The first ice storage option is composed of wind turbines, deep chillers for ice making, ice storage tanks, and the district cooling system. The second option is similar to the first option but it also includes a ground-source heat pump upstream the deep chiller. These options were also compared against a mini-hydrogen economy (District size) alternative, which encompasses a hydrogen-water cycle with excess renewable energy-powered PEM electrolysis unit, hydrogen tank, fuel cell, absorption chiller, gas compression chiller, and the district cooling system. These two options and the hydrogen-water cycle alternative were compared in terms of their REMM efficiency, First and Second-law efficiencies, and the primary energy ratio. A new Sustainability Performance Index, namely SPI was also defined. SPI is the product of the REMM efficiency, First-Law Efficiency, and the load coincidence factor, CF of wind energy. In order to establish a realistic application background for the comparisons, first a nearly-net-zero exergy farmland (nZEXF) utilizing biogas, cogeneration, solar photovoltaics, heat, absorption cycle, ground-source heat pump, Organic Rankine Cycle, and wind turbines was introduced as a model. The primary objective of this study is to determine the best option with the least avoidable CO2 emissions responsibility of the systems considered in terms of the REMM efficiency in thermal or hydrogen storage systems. Results have been compared in terms of SPI with the base scenario and it has been concluded that the second option (SPI = 0.88) is better than the first option (SPI = 0.38). However, hydrogen storage is an even better alternative with an SPI value of 1.06. These figures according to REMM with the coincidence factor being considered, mean that the avoidable CO2 emissions may be reduced by up to 54% compared to the base case. Hydrogen cycle option may also be used with the same effectiveness in district heating, while ice storage options are limited to district cooling only. This paper provides the relevant theory, shows the fundamental calculations about the option rankings based on a unit cooling load, makes recommendations for future district energy systems, and refers to a conceptual hydrogen economy driven city. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Experimental Investigation Of Energy-Optimum Radiant-Convective Heat Transfer Split For Hybrid Heating Systems
(2016) Evren, Mustafa Fatih; Ozsunar, Abuzer; Kilkis, Birol; https://orcid.org/0000-0003-2580-3910; AAJ-2321-2020
In this study, indoor radiant-convective heat transfer split of hybrid heating systems has been experimentally investigated in order to quantify the advantages of hybrid heating systems for thermal comfort in terms of operative temperature for thermal comfort and energy consumption. Operative temperature is a key parameter which is a function of indoor surface temperatures, clothing, air movement and dry-bulb air temperature. Controlled experiments were carried out in a special test chamber which was constructed according to ANSI/ASHRAE Standard 138. In this test chamber all interior surface temperatures and the dry-bulb air temperature were independently controlled. Two different types of electric fan heaters, with equal heating capacities but different fan powers, were hybridized with hydronic floor heating. In the series of experiments; fan heaters and the floor heating system were operated with different heating capacities simultaneously and hereby radiant-convective split was varied where the corresponding energy consumptions were recorded. During the process of obtaining the optimum radiant-convective heat transfer split; human comfort and energy consumption parameters were analyzed in terms of the operative temperature and exergy. According to the results of the experimental data and operative temperature-based optimization, optimum interval of radiant-convective split has been found to be between 0.65 and 0.75. (C) 2016 Elsevier B.V. All rights reserved.
Hydrogen Economy Model for Nearly Net-Zero Cities with Exergy Rationale and Energy-Water Nexus
(2018) Kilkis, Birol; Kilkis, Siir; AAJ-2321-2020
The energy base of urban settlements requires greater integration of renewable energy sources. This study presents a "hydrogen city" model with two cycles at the district and building levels. The main cycle comprises of hydrogen gas production, hydrogen storage, and a hydrogen distribution network. The electrolysis of water is based on surplus power from wind turbines and third-generation solar photovoltaic thermal panels. Hydrogen is then used in central fuel cells to meet the power demand of urban infrastructure. Hydrogen-enriched biogas that is generated from city wastes supplements this approach. The second cycle is the hydrogen flow in each low-exergy building that is connected to the hydrogen distribution network to supply domestic fuel cells. Make-up water for fuel cells includes treated wastewater to complete an energy-water nexus. The analyses are supported by exergy-based evaluation metrics. The Rational Exergy Management Efficiency of the hydrogen city model can reach 0.80, which is above the value of conventional district energy systems, and represents related advantages for CO2 emission reductions. The option of incorporating low-enthalpy geothermal energy resources at about 80 degrees C to support the model is evaluated. The hydrogen city model is applied to a new settlement area with an expected 200,000 inhabitants to find that the proposed model can enable a nearly net-zero exergy district status. The results have implications for settlements using hydrogen energy towards meeting net-zero targets.
Integrated Circular Economy and Education Model to Address Aspects of An Energy-Water-Food Nexus in A Dairy Facility and Local Contexts
(2017) Kilkis, Siir; Kilkis, Birol; 0000-0003-3466-3593; 0000-0003-2580-3910; E-5934-2015; AAJ-2321-2020
Universities have responsibilities for accelerating pedagogical innovation to enable a more sustainable future. This research work develops a three-phased approach for integrating principles of a circular economy system within a course in energy policy. The phases involve scanning available resources, identifying possible matches based on the quality of energy, namely exergy, and determining solution areas. The case study is a university-founded dairy facility in the province of Ankara, Turkey with a biogas production potential of 982 m(3) per day. Four scenarios are analyzed based on options for combined heat and power, organic Rankine cycle, waste heat recovery, absorption chillers, ground source heat pumps, photovoltaic thermal arrays, and/or low-speed wind turbines. In total, 184.1 kW(e) of high exergy power and 285.3 kW(t) of low exergy thermal power may be produced. Further evaluation of the scenarios indicates that the level of exergy match may reach 0.87 while primary energy and primary exergy savings over separate energy production from renewables may be 38% and 61%, respectively. The solution areas can address aspects of an energy, water, and food nexus based on energy from waste, energy for irrigation and agriculture, and other linkages. The results are used to engage students in advancing the Sustainable Energy Action Plans of local municipalities. The approach has applicability to other cases in a time when pedagogical innovation is urgently needed to stimulate environmental sustainability. (C) 2017 Elsevier Ltd. All rights reserved.
New Exergy Metrics for Energy, Environment, and Economy Nexus and Optimum Design Model for Nearly-Zero Exergy Airport (Nzexap) Systems
(2017) Kilkis, Birol; Kilkis, Siir; 0000-0003-2580-3910; 0000-0003-3466-3593; AAJ-2321-2020; E-5934-2015
This paper introduces the Nearly-Zero Exergy Airport (nZEXAP) concept that brings an energy, environment, and economy nexus to a common basis using the Second-Law of Thermodynamics. An nZEXAP airport has a district energy plant of its own, which receives at least 70% of the total exergy input at winter design conditions and 60% at summer design conditions, from onsite renewable energy resources and sustainable systems. These numerical criteria are consistent with the fact that especially ground heat, and solar heat have low exergy, compared to fossil fuels, and solar and wind energy applications in airports are limited. This definition is the basis of the new optimum plant design model for satisfying these new conditions with the least cost that is attributed to the cogeneration (aka CHP) system using an optimum mix of fossil and alternative fuels, such as on site-produced biogas. The main renewable exergy inputs are biogas, ground heat, building integrated or attached PV, and waste heat. Extensive use of on site wind and roof-top or on-land type of solar applications are limited in compliance to Federal Aviation Administration (FAA) regulations against glint and glare to pilots and air traffic controllers besides potential electromagnetic hazards on avionics. The exergetic performance of the airport district plant is defined and analyzed with the use of the Rational Exergy Management Model (REMM). New exergy metrics for the performance analysis and rating of nZEXAP airports, based energy, economy, and environment nexus were also developed. The optimization problem has three primary design variables, namely the ratio of the optimum cogeneration engine capacity to the peak power load, the split of the generated power supply between the airport and the groundsource heat pumps, and the natural gas to biogas mixing ratio. The objective function solves the primary design variables by a simple search method. The new tool was applied to a conceptual study for the Amsterdam Schiphol Airport in order to compare the impact of an nZEXAP design with the ongoing deep retrofit work. Amsterdam Schiphol Airport aims to make its own activities climate neutral and to generate 10% of its own energy sustainably by 2020. In this comparison, the relative impact of the biogas share, solar input, size and performance of the ground-source heat pumps, and the power-to-heat ratio of cogeneration and absorption cooling were investigated. The results indicate that with the new optimization model, nZEXAP objectives may be satisfied, if techno-economic constraints are also satisfied. Further refinements in the definition may be needed. (C) 2017 Elsevier Ltd. All rights reserved.