The Hierarchy of Energy in Architecture

Emergy Analysis

Ravi Srinivasan, Kiel Moe

• Editorial: Routledge
• Año: 2015
• ISBN:
  9781317621812
• Edición: 1
• Categoría: Architektur
• Categoría: Architektur Allgemein

The laws of thermodynamics—and their implications for architecture—have not been fully integrated into architectural design. Architecture and building science too often remain constrained by linear concepts and methodologies regarding energy that occlude significant quantities and qualities of energy.

The Hierarchy of Energy in Architecture addresses this situation by providing a clear overview of what energy is and what architects can do with it. Building on the emergy method pioneered by systems ecologist Howard T. Odum, the authors situate the energy practices of architecture within the hierarchies of energy and the thermodynamics of the large, non-equilibrium, non-linear energy systems that drive buildings, cities, the planet and universe.

Part of the PocketArchitecture series, the book is divided into a fundamentals section, which introduces key topics and the emergy methodology, and an applications section, which features case studies applying emergy to various architectural systems. The book provides a concise but rigorous exposure to the system boundaries of the energy systems related to buildings and as such will appeal to professional architects and architecture students.

Part 1
Fundamentals

chapter 1
Energy, entropy, exergy, and emergy

1.0 Energy systems

TO UNDERSTAND EVEN THE MOST RUDIMENTARY aspects of the energy systems inherent to architecture requires an expanded, if not new, set of vocabulary and concepts. To cogently act on the purpose and potential of design in the context of energy demands an even more exacting vocabulary and conceptual understanding of energy systems. The aim of this chapter is to introduce the intricate concepts and structures of energy systems as a basis for design. Without a broad introduction, the structure, behavior, and purpose of energy systems will remain abstract and unknown to designers.

Currently, the term energy is widely used in confusing, obfuscating, and incomplete ways (Figure 1.1). It is used as an overly generalized term to describe an enormous range of processes and concepts for which there is a more precise vocabulary. To clarify understanding, it is necessary to grasp the roles and relationships of the following four terms: energy, entropy, exergy, and emergy (spelled with an “m”).

In this context, emergy – the focus of this book – in particular, is a most revealing concept. The concept of emergy developed in ecosystem science and offers a more totalizing description of the thermodynamics of large scale energy systems such as buildings and cities. Emergy is a contraction of “energy memory,” and this contraction offers a hint about the more broad system boundaries of its concern. Given the systemic origin of this term, emergy most fully articulates the many implications of thermodynamics in the context of architecture and urbanization. Often misunderstood as a type of embodied energy analysis, emergy is the best way to gain a comprehensive understanding of energy systems. One of its primary contributions is the way in which it radically clarifies and illustrates the actual dynamics of energy systems. Its relevance, then, is both instructive and methodological insight into the hierarchies of energy and relative orders of magnitude that constitute the energy systems of architecture.

1.1 Energy is an umbrella term for far more specific terms

For many readers, emergy might appear as a new term. Other readers, with mixed exposure to the term and its use, might benefit from a clear explication of the term and its uses. All readers, we hope, will benefit from both the concept and the example applications of emergy analysis in this book. Our aim is to help articulate more powerful and efficacious agendas for energy in architecture. Emergy is an important conceptual and practical tool towards this end.

To understand the many implications of energy, entropy, exergy, and emergy, it is first necessary to review some fundamental aspects of energy systems and their universal thermodynamic tendencies. The first section of this chapter will thus restate some of the basic principles of energy systems that are routinely absent from energy system considerations in architecture and urbanization. This first section will thus focus on the structure and behavior of energy systems.

Systems and boundaries

All energy systems consist of the following structure: a system, its boundary, and its surroundings. The system is a portion of the universe – a body, a building, a planet – that is the focus of concern. Everything that surrounds that system is its surroundings (Figure 1.2). The boundary that separates the system and its surroundings varies and must be situationally determined. The boundary is less an object than a stated type of exchange, a change in behavior, or a shift of energetic activity pertinent to the analysis at hand. Thus it is critical to select a relevant system boundary that simplifies, but does not over-simplify, the system and its exchanges with its surroundings. In this regard, designers must develop the habit of routinely asking, “What is my system boundary, and why?”

1.2 Energy system components

The selection of a system boundary – and what it does and does not encompass spatially and temporally – is one of the most consequential design decisions for energy systems. Yet, it remains one of the least considered decisions in current energy methodologies. Without an awareness and adequate definition of the system boundary, it is very common to ignore or externalize consequential energetic exchanges and relationships. Given the potential magnitude of this systemic error, not understanding the system boundary might undermine the very purpose of energy system analysis and design.

Open, closed, or isolated

Depending on the selected system boundary, an energy system will either be designated as open, closed, or isolated. These categories stipulate the type of interaction between a system and its surroundings. Each boundary type identifies if any matter and/or energy is exchanged between the system and its surroundings.

An open system will exchange both matter and energy across the boundary (Figure 1.3). Human bodies, buildings, and cities are examples of open systems. Each of these open systems will exchange many forms of matter and energy over time with its surrounding milieu. Bodies, buildings, and cities not only exist and survive as open systems, but also thrive as open systems. Especially as open systems, it is important to ask, however, what is the system boundary of a body or a building? There are multiple appropriate systems boundaries that all depend on the type of inquiry guiding the analysis. The energetic exchanges of a body or a building, for example, extend well beyond their respective skin and envelope systems. What should be considered inside the system and what should surround the system? How the system boundary is construed greatly impacts the relevance and significance of the analysis or design. In this way, current energy system design in architecture frequently suffers unconsidered or inadequate system boundary definition.

1.3 An open thermodynamic system

A closed system will exchange energy, but not matter, across a boundary (Figure 1.4). A hermetically sealed glass jar of water is a closed system. One can add or remove heat from the jar system but the quantity of matter inside the jar system will remain constant. There are phases of a building – such as construction or demolition – when the exchange of matter is perhaps paramount. There are other phases – such as in the amount of solar energy gained in a greenhouse in a four-hour period – when just the exchange of energy is paramount. The latter can be considered a closed system for the stated boundary period, but only for that stated time period.

1.4 A closed thermodynamic system

An isolated system exchanges neither energy nor matter across the boundary (Figure 1.5). It is difficult to construe system boundaries wherein a building is understood to exchange no matter or energy. The universe as a whole is most likely an isolated system. Isolated systems often only exist as conceptual abstractions and there are few actual isolated systems. For instance, the most common statement of the second law of thermodynamics – that a system tends towards maximum entropy – presumes an isolated system. It is extremely important to recognize, however, that all buildings and urbanization exist as non-isolated systems.

1.5 An isolated thermodynamic system

With the basic system-surrounding structure of energy systems in place, it is possible to consider more directly the laws of thermodynamics that govern the behavior of all energy system structures.

1.1 Thermodynamic laws

WITHOUT EXCEPTION, ENERGY SYSTEMS follow a set of universal tendencies. Over the past two centuries, scientists in a range of disciplines have observed energy system principles and dynamics that are so consistent and inviolable as to be deemed universal “laws.” (For familiarity, we’ll maintain this metaphor of law-based system governance, even though there is no juridical entity that adjudicates system tendencies.) The zeroth law establishes the concept of heat and its equivalence in all energy systems. The third law establishes the concept of absolute zero, the theoretical minimum possible energy state. The first and second of these laws, in particular, bear consideration.

The first law of thermodynamics states that energy can be neither created nor destroyed. This is the conservation of energy. All energy is conserved. It is therefore by definition confusing to claim that a particular design aims to “conserve energy.” This outcome is spontaneously guaranteed regardless of the design. Likewise, it is impossible to “produce” energy in a building or otherwise. Rather, energy is only transformed or converted to other forms and states. The construction and occupation of a building requires the transformation of many forms of energy. This fact is a very valid premise for the design of energy systems, whereas frequent references to the “production” or “conservation” of energy in a building through design simply do not have any thermodynamic correspondence in reality.

The second law states that isolated systems tend toward a state of equilibrated matter and energy. The universe, you see, abhors available energy gradients and forms emerge that degrade those gradients. A fully equilibrated system would fully degrade available gradients. Such systems would ...