Canan Acar

Comparative Environmental Impact Evaluation of Hydrogen Production Methods from Renewable and Nonrenewable Sources

In this chapter, a comparative environmental impact study of possible hydrogen production methods from renewable and nonrenewable sources is undertaken with a special emphasis on Turkey. The goal is to make useful and practical recommendations to the authorities in terms of research and development, demonstration projects and applications. Environmental impacts (global warming potential, GWP and acidification potential, AP), production costs, energy and exergy efficiencies of eight different methods are compared. These methods are natural gas steam reforming, coal gasification, water electrolysis via wind and solar electrolysis, thermochemical water splitting with a Cu–Cl and S–I cycles, and high temperature electrolysis. The relations between environmental impacts and economic factors are also presented using the social cost of carbon (SCC) concept. The global warming and acidification potentials of the selected production methods show that thermochemical water splitting with the Cu–Cl and S–I cycles are advantageous over the other methods, followed by wind, solar, and high temperature electrolysis. In terms of hydrogen production costs, electrolysis methods are found to be least attractive. Energy and exergy efficiency comparisons show that biomass gasification becomes advantageous over the other methods.

A review on potential use of hydrogen in aviation applications

In this paper, utilisation of hydrogen as an alternative aviation fuel is reviewed, along with some past and present-day activities, covering three critical topics of energy consumption, environmental impact and emission related cost. It also evaluates the energy consumptions, environmental impacts, emission-related costs of jet fuel A, natural gas and hydrogen from selected production methods in short and long distance aircrafts. Furthermore, costs and efficiencies of hydrogen production from steam methane reforming and wind, PV, and hydro-based electrolysis are compared for a more detailed comparative assessment. Aviation fuel evaluation results show that hydrogen from hydro- and wind-based electrolysis is a promising clean, efficient and less costly candidate among the selected fuels in this study. The assessment study shows that compared to selected hydrogen production options, hydro-based electrolysis is the most advantageous one.

Targeted use of LEDs in improvement of production efficiency through phytochemical enrichment

Based on available literature, ecology and economy of light emitting diode (LED) lights in plant foods production were assessed and compared to high pressure sodium (HPS) and compact fluorescent light (CFL) lamps. The assessment summarises that LEDs are superior compared to other lamp types. LEDs are ideal in luminous efficiency, life span and electricity usage. Mercury, carbon dioxide and heat emissions are also lowest in comparison to HPS and CFL lamps. This indicates that LEDs are indeed economic and eco-friendly lighting devices. The present review indicates also that LEDs have many practical benefits compared to other lamp types. In addition, they are applicable in many purposes in plant foods production. The main focus of the review is the targeted use of LEDs in order to enrich phytochemicals in plants. This is an expedient to massive improvement in production efficiency, since it diminishes the number of plants per phytochemical unit. Consequently, any other production costs (e.g. growing space, water, nutrient and transport) may be reduced markedly. Finally, 24 research articles published between 2013 and 2017 were reviewed for targeted use of LEDs in the specific, i.e. blue range (400-500 nm) of spectrum. The articles indicate that blue light is efficient in enhancing the accumulation of health beneficial phytochemicals in various species. The finding is important for global food production.

Chapter 1.1 – Potential Energy Solutions for Better Sustainability

Abstract In this study, critical challenges related to increasing global energy demand and drawbacks of traditional fuels are discussed along with some potential solutions including the cutting-edge research taking place at the University of Ontario Institute of Technologys Clean Energy Research Laboratory. Renewable energies, hydrogen, thermodynamic and hybrid cycles, photonic hydrogen production, ammonia, system integration, and multigeneration are covered, and their importance in addressing global energy challenges in sustainable, clean, affordable, and reliable manners is given by examples. In addition to providing examples from the recent literature, renewable energies are comparatively assessed based on their performance criteria and environmental effect. Hydrogen and ammonia production performances of coal, oil, natural gas, nuclear, biomass, geothermal, hydropower, ocean, solar, and wind are comparatively assessed based on their energy and exergy efficiencies, production costs, and emissions. Our results show that when emissions, efficiencies, and production costs are taken into account, natural gas has the highest performance in terms of hydrogen while hydropower has the highest performance in terms of ammonia production.

Environmental impact assessment of renewables and conventional fuels for different end use purposes

In this study, we present a comparative environmental impact assessment of renewables and conventional fossil fuels for electricity and hydrogen generation. The conventional fossil fuels investigated in this study are coal, oil, and natural gas. Renewables considered in this study are geothermal, hydropower, ocean, solar, and wind energies. Furthermore, nuclear and biomass energies are taken into consideration while assessing environmental impact and performances. Environmental impact criteria considered in this study are CO2, NOx, and SO2 emissions, land use, water consumption, water quality of discharge, solid waste and ground contamination, and biodiversity. For comparison purposes, all collected data are normalised and ranked between 0 and 3 while 0 giving highest negative environmental impact and 3 giving lowest negative environmental impact. Our results showed that overall, in terms of both electricity and hydrogen production, oceans give the highest rankings (2.71 for electricity and 2.73 for hydrogen). Coal has the lowest rankings in terms of environmental impact (0.26 for electricity and 0.30 for hydrogen).

Energy and Exergy Analyses of a Zero Emission Power Plant for Coproduction of Electricity and Methanol

In this study, we study and evaluate a zero emission integrated system, as taken from the literature, for coproduction of electricity and methanol. The investigated integrated system has three subsystems: water electrolysis, Matiant power plant (oxy-fuel combustion of pure methane), and methanol production unit. The system and its components are analyzed energetically and exergetically. The rates of exergy destructions, relative irreversibilities, and sustainability indexes of each subunit of each subsystem, as well as the overall system are analyzed to identify the greatest exergy losses and possible future research directions. The total rate of exergy destruction of the overall system is calculated to be around 280 MW. The greatest rate of exergy destruction, therefore the greatest irreversibility, occurs within the power plant unit (about 60 % of the total rate of exergy destruction). The energy efficiencies of electrolysis, power plant, and methanol synthesis unit are found to be 30 %, 76 %, and 41 %, respectively. The exergy efficiencies of electrolysis, power plant, and methanol synthesis unit are found to be 30 %, 64 %, and 41 %, respectively. Depending on the utilization of the heat rejected from the different units of each subsystem, the overall system could have energy and exergy efficiencies up to 68 % and 47 %, respectively.

Performance Assessment of a Two–stage Heat Pump–Drying System

In this study, energy and exergy analyses of a two–stage heat pump–drying system are conducted, and the performance of the overall system is then evaluated. The system has two cycles: a heat pump and a drying cycle. The working fluid of the heat pump and the drying cycles are R-134 A and air, respectively. The two–stage heat pump consists of two evaporators; one operates at high pressures while the other one operates at lower pressures for additional cooling and dehumidification of the drying air. After the condenser, two sub–coolers are used for additional heating. Also, the exergy destruction rates, energy and exergy efficiencies of each unit, cycle, and the overall system are calculated. Each unit and cycle’s exergy destruction rate is investigated to identify the corresponding unit’s relative irreversibility, and as a result, potential points to improve the system’s exergetic performance. Parametric studies are conducted to understand the effect of ambient temperature on exergy efficiencies and exergy destruction rates of each unit, cycle, and the overall system. The selection and design of these to reduce exergy destruction, and as a result, increase the exergy efficiency of the system by minimizing irreversibilities is discussed in this study. Furthermore, the effect of air mass flow rate on system COP is studied. The initial results with 0.5 kg/s air flow rate at ambient temperature and pressure of 5 °C and 1 atm gives energy and exergy efficiencies of 62 % and 35 %, respectively. The COP of the system is calculated to be about 3.8.

2.17 Photoactive Materials

This chapter introduces and examines photoactive materials and their role in clean energy systems to address local and global environmental issues during the transition to a sustainable future. Some advantages and disadvantages of various photoactive materials and processing technologies, with a special prominence on photocatalytic hydrogen generation, are considered in this chapter. Societal, ecological, and financial characteristics of photoactive materials are kept in mind during the comparative assessment of various photoactive materials and processing technologies and hydrogen production options. This chapter provides key background information on photoactive materials including photocatalysts, photoelectrochemical (PEC) cells, photoelectrodes, and photoelectrode processing is presented. After that, solar driven hydrogen generation methods are explained more in depth in conjunction with comparative performance assessments. Later, photocatalytic hydrogen generation methods are presented, and the photocatalysis mechanism and principles are introduced. Some of the main photocatalyst groups, specifically titanium oxides, cadmium sulfides, zinc oxides and sulfides, and other metal oxides are investigated in details. Subsequently, photocatalyst recycling issues are explained and comparative performance assessment criteria are introduced as hydrogen production rates (both per mass and surface area of photocatalysts), band gaps, and quantum yields.

3.1 Hydrogen Production

This chapter describes existing and potential future hydrogen production methods and investigates a variety of alternative hydrogen production methods via the utilization of renewable and nonrenewable energy resources. In addition, these alternative hydrogen production methods are comparatively assessed by taking their emissions, hydrogen production cost, and energy and exergy efficiencies. Furthermore, the relationship between environmentally harmful emissions and their economic impact is evaluated based on a concept called the social cost of carbon (SCC). Electrical, thermal, biochemical, photonic, electrothermal, photoelectric, and photobiochemical are the principal energy resources evaluated in this chapter. The comparative assessment outcomes of this chapter indicate that photonic energy is more environmentally benign compared to other principal energy resources evaluated in this chapter. In this chapter, the selected photonic energy-based hydrogen production methods are photocatalysis, photoelectrochemical (PEC) method, and artificial photosynthesis. Among other selected hydrogen production methods, thermochemical water dissociation and hybrid thermochemical (such as Cu–Cl, S9I, and Mg–Cl) cycles are environmentally benign with less emissions compared to other selected methods too. When it comes to hydrogen production cost and energy and exergy efficiencies, PEC and photovoltaic (PV) electrolysis-based hydrogen production have the lowest performance. For that reason, it is concluded that in order to make these environmentally very benign solar-based hydrogen production options the preferred components of future energy systems, their energy and exergy efficiencies should be enhanced by using novel materials and integrated systems. With the introduction of more advanced systems and materials and the increase in efficiencies, solar-based hydrogen production methods are expected to become more cost competitive, reliable, clean, and sustainable. Due to their highly developed technologies and mostly already available infrastructures, fossil fuel reforming and biomass gasification-based hydrogen production have the highest energy and exergy efficiencies among the selected options. Overall, the results of the comparative assessment are presented by average rankings, which state that hybrid thermochemical cycles are predominantly favorable hydrogen production alternatives with their relatively low emissions and production costs and high efficiencies.

2.32 Future Directions in Energy Materials

The developments and applications of new materials have resulted in significant effects on our consumption, conversion, and production of energy, our daily lives, our health, our use of technology, and our security. In short, materials play an increasingly important role in our everyday lives. It is clear that a manufacturing and innovation strategy which highlights advanced materials development is more likely to play a substantial role in future energy systems. This chapter is an essential part of the process to identify new opportunity for industry, government, and academia. It stands as a signpost to the future. In this chapter, future directions in energy materials are discussed in detail to understand the role of energy materials in future energy systems and sustainability.