Electric energy system planning and the second principle of thermodynamics

This thesis deals with the long-term planning of electric energy systems. Such systems are defined by complex interconnections of end-uses, energy conversion devices and natural resources. The planning process is usually guided by a number of design criteria, namely, economic, social and environmental impacts as well as system reliability and efficiency. The planning challenge is to find an acceptable compromise among these often conflicting objectives. System efficiency is a critical design criterion normally measuring the ratio of the system output and input energies. In electric energy systems, efficiency is normally defined according to the First Principle of Thermodynamics which states that energy cannot be destroyed. In this thesis, the definition of efficiency in electric energy system planning is broadened to include interpretations according to both the First and Second Principles of Thermodynamics. The Second Principle essentially states that the "quality" of energy decreases or, at best, remains constant in any conversion process where the quality of energy (denoted here by exergy) is a measure of the ability of a form of energy to be converted into any other form. Work, hydroelectric potential and electricity are examples of high quality energy sources while low temperatures heat end-use applications are at the low end of the quality scale. Since certain types of energy conversion processes may show high levels of exergy destruction, even though energetically efficient, it is important to design energy systems such that the energy quality of an end-use is matched as much as possible to that of the energy supply thus avoiding situation where a high quality supply is used for a low quality purpose.;The electric energy industry has virtually ignored exergetic considerations in system planning due, to a large extent, to a lack of familiarity with the Second Principle and its implications. Nevertheless, exergy is an attribute which must be planned and conserved with at least the same priority as energy. It is demonstrated here that the planning of energy systems will be drastically affected when both energy and exergy are considered. However, to be able to rationally use the natural resources, exergetic analysis must become an integral part of system planning. This thesis analyses the application of the Second Principle of Thermodynamics in the planning of electric energy systems through theory, examples and case studies including economic considerations.;In order to achieve electric energy systems that are more exergetically efficient, a new type of electric energy tariff called type-of-use, is proposed. Analogous to the time-of-use rate that assigns different monetary values for the time of the day considered, the type-of-use tariff assigns a monetary value to the end-uses. Simulations are performed in different electric energy systems to demonstrate that type-of-use tariffs will indeed lead to more exergetically efficient systems.;The benefits of exergetic analysis are supported by a number of studies presented in this thesis. These studies analyse from the points of view of energetic and exergetic efficiency and cost the following: (i) A space heating system; (ii) The impact of a major introduction of electric vehicles in Canada and (iii) The long range planning of a regional electric power system consisting of two interconnected provinces.