Dissertation
Master's degree
Department: MBA
Abstract
About two-thirds of the world's energy is consumed in cities. Along with the many solutions that have been provided to reduce the energy demand, some technologies and researches have also been aimed at optimizing the energy supply. The technology of simultaneous production of electricity and heat is among the technologies that have been developed in the last few decades. The management of the urban energy system in the supply sector using this technology has many problems and complications that have prevented it from being operational in big cities.
In this thesis, after examining the city and its required resources, the technical issues and the strengths and weaknesses of the cogeneration technology have been examined.
The developed model was simulated with the aim of maximizing the use of fuel energy for five different scenes. There has been a 20% saving in fuel costs and a total of 20% compared to the current scene. Based on the simulation results, the average heat produced in cogeneration units is about 429 megawatts. The total thermal energy produced in these units will be about 3.75 million megawatt hours during the year.
Assuming the sale of this resource at the full price of hot water for the domestic consumer, about 163 million dollars in energy savings will be generated annually, which is a return on investment of about 240 million dollars for the installation of cogeneration plants. The capital return of this project will be in less than two years (about 1.5 years) and assuming that the price of energy carriers does not increase, the return of this investment for a three-year period will be about 46%.
Key words: simultaneous production of electricity and heat, urban energy network, economic analysis, optimization of energy supply
Chapter One
1 Introduction and general research
1.1 Introduction
In this chapter, first the city and its needs for resources and then the solutions to meet these needs are examined. Among the solutions, the study of technology and tools for the simultaneous production of electricity and heat (and cold) as a basic mechanism for optimizing energy supply is done with more precision and detail. 1.2 The city The city can be compared to the body of living beings. Because for life, it needs primary resources such as water, energy, food and air, numerous interactions and processes are carried out inside it, and finally the materials that are the waste and sewage of these processes are disposed to the surrounding environment.
The urban energy system[1] represents the interconnected set of energy supply and consumption processes to meet the needs of the population in the city.[20] In the past, this need was much simpler and generally summarized in the need for general heating and the energy needed for cooking. Today, this need has become much wider and includes the need for cooling and heating the building, providing lighting for indoor and outdoor environments, electricity for general purposes, energy needed for transportation, energy needed for communication and so on.
1.2.1 Resources required by the city
International Energy Agency estimates show that currently about two-thirds of the world's primary energy resources are used to meet the needs of cities, and this figure will reach 73% by 2030, and the result of this energy consumption is the release of 70% of the total carbon dioxide produced in cities.[21] This significant volume of energy consumption has led to an increase in studies to improve the efficiency of energy production and distribution as well as demand management. Moving towards more sustainable sources and solutions instead of using fossil fuels[2] is also one of the concerns of researchers and governments.
Urban energy system is directly dependent on heating, cooling, fuel and electricity sources. Other resources such as air, water and space in the city also indirectly affect this system, but their effect is usually significant and decisive. (Tables, diagrams and pictures are available in the main file) 1.2.1.1 Heat People need heat in different parts. The most energy consumption in this sector is for heating residential, office, commercial, recreational, etc. places, providing hot water for bathing and sanitary purposes, as well as heat for cooking.
Although the heating systems in the mentioned environments are technically similar, they differ in terms of energy consumption at different hours of the day and night, which can reduce initial investment and costs in the integrated urban energy management system.
Although the heating systems in the mentioned environments are technically similar, they differ in terms of energy consumption at different hours of the day and night, which can reduce the initial investment and operating costs in the integrated urban energy management system.
Most of the heating needs are provided directly through fossil fuels (gas and diesel) and in some countries where electricity is produced from renewable sources (such as water dams) and coal-burning and nuclear power plants are available, the share of electricity in meeting people's needs has increased, especially for cooking purposes.
Using solar water heaters is another solution that is used to provide heat needs in cities and villages, and in areas where access to sunlight is suitable, it has an acceptable efficiency. [1]
Cities located in tropical regions usually do not need heating systems and their heat consumption is only for providing hot water and cooking.
1.2.1.2 Electricity
Electricity in the city has a variety of consumers, which are general uses for household and office electrical equipment, providing internal lighting for residential and non-residential environments, providing lighting for urban environments (such as streets), providing energy for The need for equipment and urban infrastructure (such as hospitals, airports, fuel stations, telecommunications antennas, traffic lights, CCTV cameras) is one of them.
Electricity consumers can be distinguished from each other in two ways:
Consumption patterns around the clock and days of the year
Sensitivity to power cuts
Sensitivity of some centers such as hospitals, Airports and Due to power outages, these centers are equipped with emergency power supply systems. Power outages can be caused by increased demand over supply, technical problems in the transmission and distribution network, or natural disasters. Dispersed production of electricity and the construction of small-scale power plants inside the cities, taking into account the environmental limitations, can also increase the security factor of power supply to sensitive centers. Work at a certain temperature throughout the year.
Cooling required for residential, commercial, office, recreational buildings. In the hot seasons of the year, the first part has a very small contribution in terms of consumption, but its consumption is permanent. The need for the second part is temporary, but in hot days of the year (and especially very hot hours), its amount increases a lot. The need of the first part is usually met by using condensation refrigeration systems, therefore, due to the small share of these consumers, we consider their consumption as part of electricity consumption (condensation refrigeration system).
To provide cooling of buildings, there are three tools (or a combination of them):
Condensation refrigeration system (consumes electricity)
Absorption refrigeration system (consumes heat in the form of hot water, water vapor or direct flame)
Humidification systems (consumes water and electricity)
1.2.1.4 Air, water and space
Air and water are two necessary and available but limited resources in every city. The space (usable surface) also has a similar situation, with the difference that the space of cities (especially megacities) cannot be increased, and the limitation of space and the density of residential tissue limit the ability to implement many optimization plans.
The amount of access to air and clean water depends on the geographical location of the city. In choosing the electricity generation solution in each region, the amount of available water should be taken into account. Centralized electricity production produces about 25.6% more carbon dioxide than cogeneration systems, but cogeneration systems emit more pollutants near the place of energy consumption (city). [22] Therefore, the development of cogeneration systems in big cities that are plagued by pollution problems should be done with care and study. 1.1.1 Urban resource management Until the period of using fossil fuels, urban energy was provided through biomass resources, which were mainly wood and coal. The sources of these materials should be located in a certain area around the city. The limitation of these resources, along with the limitation of water and food, limited the size of the city and its potential expansion.
Coal was the first fossil fuel that was widely used as an energy source in the city, industry and transportation (steam train). After that, in the 20th century, electricity, oil and gas made their way into the lives of most people.