Birol I. Kilkis

• Professor
• Chair at Başkent University

Addressing climate change is an urgent issue that requires effective and sustainable solutions at multiple scales from the building to the district and city scales. This study focuses on the avoidable carbon dioxide emissions responsibilities due to exergy mismatches between supply and demand at multiple scales based on the Rational Exergy Manageme...

This paper highlights the significance of optimizing district energy systems with solar prosumers from an exergy-based perspective to minimize carbon dioxide emission responsibilities. As a case study, the Dezonnet solar district energy project in Haarlem, the Netherlands, which incorporates solar prosumers with traditional rooftop photovoltaic-the...

Aligning with the decarbonization roadmap of the EU and fifth-generation district heating systems, an exergy-based optimization and decision-making model was developed for minimum CO2 emission responsibilities. Nine environmental, thermal, and electromechanical constraints were applied. Seven cases are presented, including sewer heat in Bavaria and...

This paper deals with the existing carbon dioxide mitigation efforts toward the Paris agreement and shows that current economic rules and the first law of thermodynamics, all of which are linear, are necessary but not sufficient tools to solve the nonlinear problems of global warming. In this respect, the quasi-linear, Pareto principle-based green...

An exergy-based model hypothesizes that labyrinth-type ground-to-air heat exchangers are responsible for carbon dioxide emissions if the exergy of power demand concerning ancillaries like fans and pumps exceeds the thermal exergy gain. This hypothesis was analyzed for a novel solar greenhouse proposal in northern Holland, primarily using heat pipes...

This paper responds to the EU goals of decarbonization with solar energy leading to fifth-generation district energy systems (5DE). The dilemma of low-exergy (low-temperature) district heating systems with renewable and waste thermal sources and the temperature-incompatibility of the current comfort heating equipment demanding higher supply tempera...

This paper addresses the challenges the policymakers face concerning the EU decarbonization and total electrification roadmaps towards the Paris Agreement set forth to solve the global warming problem within the framework of a 100% renewable heating and cooling target. A new holistic model was developed based on the Rational Exergy Management Model...

Total decarbonization strategies are facing technical and environmental challenges according to the 2nd Law of Thermodynamics, such as equipment oversizing versus temperature peaking by heat pumps to accommodate low-temperature renewable and waste energy sources. As a method of this paper, the Rational Exergy Management Model (REMM) derived fourtee...

This paper discusses whether the exergy destruction minimization or energy efficiency maximization comes first in resolving the climate emergency problem and provides sustainable solution options regarding the 2nd Law of thermodynamics. It has been shown that low-temperature district energy systems with renewable energy sources and waste heat are e...

According to the 2018 IEA Key World Energy Statistics Report, the share of buildings in energy consumption has lately exceeded the individual shares of industry and transport.

This chapter redefines the concept of sustainable aviation (SA) in a holistic model that encompasses the landside and the airside of aviation. It also covers the type of the aviation fuel, ground transport, safe utilization of renewable energy resources near airports, waste management, biogas, new HVAC technologies, aviation and passenger safety, e...

Along with continuing the efforts of decoupling CO2 emissions from sustainable development, exergy-rational cities are becoming universally important. This statement does not mean that energy rationality and energy efficiency are ignored. But it is a fact that the mission of the First-Law of Thermodynamics has been almost completed in a pretty good...

The realization of net-zero exergy districts can be supported by urbanization options for district density and building characteristics. This research work formulates an urbanization algorithm to minimize the carbon dioxide emissions responsibility of districts based on energy usage and aspects of embodied energy to tackle multiple drivers of urban...

In this paper, a new model for the embodied exergy payback period is presented, which considers the exergy savings during acceleration and take-off, climb, trim-level cruise, descent and thrust reversal in landing for each flight versus higher exergy embodiment of composites that are used during manufacturing when compared to metals. The research w...

In this paper, a new model for the embodied exergy payback period is presented, which considers the exergy savings during acceleration and take-off, climb, trim-level cruise, descent and thrust reversal in landing for each flight versus higher exergy embodiment of composites that are used during manufacturing when compared to metals. The research w...

Within the broad range of sustainability and decarbonization efforts, energy and exergy-rational cities are becoming universally important. Within this context, both ORC systems, which are touted as primarily useful for utilizing low-enthalpy geothermal resources and heat pumps, which are considered as the primary tool for decarbonization are criti...

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 powe...

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 co...

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...

Net‐zero buildings have a variety of definitions according to their boundary selection. Because these definitions are based only on the quantity of the electrical power exchange with the grid in a given period of time, those boundaries do not make much difference, because exergy and energy of electricity are close to each other. When thermal energy...

Radiant panels are known to be energy efficient sensible heating and cooling systems and a suitable fit for low-exergy buildings. This paper points out the little known fact that this may not necessarily be true unless their low-exergy demand is matched with low-exergy waste and alternative energy resources. In order to further investigate and metr...

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- so...

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 generat...

Turkey is rich in both geothermal energy and lignite reserves, which in many cases, are co-located. This condition makes it feasible to utilize both lignite and geothermal energy in a hybrid form for combined power heat, and cold generation, which may lead to optimally energy and exergy efficient, environmentally benign, and economically sound appl...

Indoor thermal comfort depends on the operative temperature, which is a function of the dry-bulb air temperature and the mean radiant temperature. For maximum comfort, an optimum combination of these temperatures is necessary, because each of them independently affects the heat losses (gains) and thus the energy and exergy demand of the building. T...

A high performance building needs to optimally satisfy human comfort, environmental concerns, energy efficiency, and economy. In order to achieve this collective goal with a minimum compromise among these four sustainability parameters, buildings need to reduce their exergy demand besides energy demand. In the so-called low-exergy buildings, the ra...

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 Europ...

Recognizing that the energy-saving potential of combined heat and power (CHP) systems is underused, the Council of the European Union has issued a Cogeneration Directive. In terms of specific guidelines and rating parameters based on energy efficiency, the objective was to promote "high-energy cogeneration." This paper makes a critical review of th...

A composite radiant wall panel was developed, which collectively performs heating, ventilating, and air-conditioning tasks at moderate temperatures such that low-enthalpy energy resources can be directly utilized. This technology eliminates the need for costly equipment over sizing and supply temperature conditioning, which are all associated with...

Floor heating has been the most basic version of panel heating and cooling systems since ancient times. Recently newer applications are becoming widely used, especially in Europe. For all panel applications, whether the most basic or the most innovative, their attributes are mainly focused on energy efficiency and better comfort. So far, little att...

Energy, exergy, environment, and comfort advantages of panel heating and cooling systems in green buildings are especially important for hybrid HVAC (Heating Ventilating and Air-conditioning) systems, which co-locate radiant floor panels with forcedair convection systems. In spite of their advantages, implementation of hybrid HVAC systems is diffic...

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 syste...

Heating and air-conditioning systems have very low exergetic efficiency as they dissipate primary energy resources at low temperatures usually between 90 and 60°C. This compounds the problem that buildings spend approximately 30% of all the energy consumed in the U.S. for heating and air-conditioning. The overall result is a large entropy productio...

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...

Effective utilization of low-enthalpy energy resources in heating, ventilating, and air-conditioning (HVAC) of sustainable buildings require a careful optimization to assure the most economical coupling of HVAC systems with low-enthalpy energy resources. In one of the two separate prior studies an optimization algorithm for the optimal coupling of...

Low-temperature district heating permits the use of energy resources formerly discarded or could not be claimed. However, its investment may be capital intensive because of equipment oversizing and temperature peaking required by conventional equipment. In classical design philosophy, flow is minimised in order to compensate some of the oversizing...

This article identifies and explains several attributes of geothermal energy. High exergetic efficiency due to a close temperature tie between geothermal energy and district heating and cooling was noted. Parameters governing the rational use and management of geothermal energy systems with special emphasis on integrated-cascaded district energy sy...

A new cost optimization algorithm has been developed as a robust tool for engineers with the objective of designing cost-effective heating and cooling systems with low-enthalpy energy resources. Three modules for minimum combined life-cycle cost were prepared, which involve the analysis of conventional terminal units, panel systems, and hybrid HVAC...

The geothermal district energy system with new rating parameters was evaluated. The new rating and evaluating parameters were developed for the comparison of geothermal district energy system alternatives with the main emphasis on heating and cooling. It was shown that the hybrid cycle, cascaded and integrated systems offer the best alternatives no...

A thermal connectivity between radiation and conduction was established based on Planck's theory such as, photons were described as particles with an equivalent atomic weight of 3.5 x 10-4. Using this connectivity, matter properties of the universe were estimated, and it was modeled as a thermally radiating enclosure in an infinitely large thermal...

An analytical solution for the optimum equipment oversizing and temperature peaking is presented, which is intended to resolve conflicts between heat pumps and high-temperature equipment. Advantages of using low-temperature heating equipment and its impact on energy economy and environment are discussed. An alternative design composition of wind en...

It is postulated that energy fields in space and matter are quantized by an entity having coincident properties of wave and virtual matter. A unified link between thermal radiation and conduction was established as confirmed by Planck's quantum theory, and a unified heat transfer equation was developed. One-dimensional, steady-state thermal conduct...

Approximately one-third of the primary energy resources are consumed in space heating, cooling, and air-conditioning with a very low exergetic efficiency. The depleting nature of primary energy resources, negative environmental impact of fossil fuels and low exergetic efficiencies obtained in conventional space heating and cooling are the main ince...

In the rating and design of the geothermal district energy (DE) systems the technology, cost, benefits, and environmental effects of the alternatives need to be carefully compared. This study deals with the evaluation of several alternatives of district energy systems for the city of Denizli. These alternatives vary from the existing geothermal pla...

Heat pumps, hybrid HVAC systems, thermal energy storage, waste, and alternative energy utilization are some of the reasons why today's complex hydronic space conditioning and snow melting circuits operate at moderate supply temperatures, at an expense of large temperature drop and wide diversity of generally oversized equipment. Increasingly comple...

This article identifies the attributes and limitations of low-temperature district energy systems and discribes the factors affecting the feasibility. Equipment oversizing characteristics in series and parallel arrangements, such as capacity improvement, temperature drop, and energy loss in the circuitry, are analytically expressed.

One of the earliest examples of large scale use of the geothermal energy is the district heating system in Boise, Idaho. Established in 1892, this system now serves 266 customers--mostly residential. Today, excluding heat pumps, there are about 300 sites in America where geothermal energy is currently used in various applications; including distric...

This paper discusses the optimum selection of equipment oversizing and peaking capacities in low enthalpy geothermal district heating systems. Alternative techniques of increasing the geothermal system effectiveness are explained, and a design example is given for the city of Nevsehir in Turkiye

This articles describes when the sensible, latent, and other functions of an HVAC system should be decoupled. The concept of coupling the HVAC functions at the plant, distribution, and delivery levels dominated the industry until recently. Diversity of HVAC functions, and the precise control requirements now call for the relief of a single and over...

Panel heating systems offer various advantages in sensible space conditioning. These include, but are not limited to, energy-saving potential and favorable tie-in capabilities with low-temperature and low-intensity energy sources such as solar systems and heat pumps. In order to predict and implement the attributes of panel systems, a comprehensive...

Radiant panel heating and cooling systems for sensible space conditioning have several attributes. These include, but are not limited to, energy savings potential and ability to favorably tie-in with moderate temperature, low-intensity energy sources like solar systems and heat pumps. In order to predict and incorporate such attributes of panel sys...

A universal and simple technique that does not require extensive manipulation of meteorological data was require extensive manipulation of meteorological data was developed. In this connection, a new design algorithm was proposed that requires only design air temperature, wind speed, and maximum recorded daily snowfall in order to calculate the hea...

A simple analytical technique was developed to predict the transfer of heat in a snow-melting slab. The primary objective was to develop a simple design tool while retaining sufficient accuracy. This analytical model is intended to enrich the rules given by ASHRAE guidelines, which apply for a limited design range using metal pipes. The model disti...

The aim of this paper is to provide the fundamentals of and a design algorithm for radiant panel cooling systems with special emphasis given to solar energy utilization and to demonstrate its feasibility with a case design. A steady-state heat transfer model was developed to determine the heat diffusion in a cooled ceiling slab and to predict its i...

According to the basic nature of radiant floor heating, it is possible to operate at an average water temperature as low as 35°C. The objective of this paper is to investigate how this feature when combined with other attributes of radiant floor heating may enhance the performance of an air to water type heat pump especially in adverse climates. A...

Fluidized bed to external wall heat transfer phenomena play an important role in the design and rating of a fluidized bed. In fluidized beds where the heat exchanging surfaces are located along the external walls, maximum heat transfer rates are desirable with a rather uniform distribution over the wall height. Although available models rely upon l...

Some of the basic concerns in the analysis of spouted-bed hydrodynamics are the flow pattern and the pressure field of the fluid and the spout shape. These are closely related with other design concerns such as spoutability, minimum spouting velocity and maximum spoutable bed depth. A computer program was developed in order to determine the flow pa...

Utilization of small and local energy supply systems using renewable resources draw more attention due to the well known energy crisis. Only 18% of the hydraulic energy potential of Turkey is utilized by large hydroelectric systems. This paper presents a vertical axis water-wheel with tilting vanes during rotation. After a brief survey, details and...

The possibility of using the fluidized-bed principle for solar drying of fruits economically and simply is explored. With the aid of computerized design methods, an optimized fluidized bed/packed bed combination was achieved, that in addition functions as a solar air heater. Based on this configuration, a novel aparatus was designed in Turkey for d...

Solar heat gain of buildings may provide an appreciable portion of the total heating energy for sunny climates. Typical heat load calculations made for sample buildings show that solar heat gain may play a significant role in reducing the heating energy. A computer program was developed for the design purpose of heating-air conditioning systems of...