Office densification effects on comfort, energy, and carbon lifecycle performance: An integrated and exploratory study

Generally, the environmental impacts of buildings are benchmarked per square meter as a functional unit. However, this practice prevents developing a user-centered approach in which performance is linked to real usage and not building size. Currently, the less a building is used, the lower the energy consumed during its use and, consequently, the impact per square meter, which does not make sense regarding both usability and environmental performance. Following user-centered design principles, the goal of the present research is to assess the environmental impact of buildings based on novel user-based functional units and to understand the environmental impact consequences of office occupation density. An experiment within the area of an academic office offered the opportunity to test the densification of working spaces and evaluate the resulting environmental and comfort impacts. In the end, the new user-based functional units highlight a reduction of all environmental indicators by almost 50 %. Also, the functional unit "eq-nominal people per effective presence" is introduced as most suitable to evaluate environmental performance according to real building usage, as a complement to square meter function units.

Reuse in Architecture & Structural Design

Jan Friedrich Georg Brütting

Introduction The construction industry has an extensive impact on the global environment and will be facing three big challenges in the next decades: reducing its resource consumption, decreasing its energy use, and limiting its waste production. This is even more crucial, considering global population growth and increasing urbanization. Consequently, a shift of paradigm from a linear economy of make-use-dispose, towards a circular economy that advocates closed loops within the service life of materials and components is required. Recycling currently is the common strategy to make use of obsolete materials; however, it involves energy for reprocessing (e.g. melting steel scrap). Instead, direct reuse of components close to their original form has the potential to reduce environmental impacts further because sourcing additional raw material is avoided and only few energy is spent for transformation [1]. In the case of buildings and infrastructures, load-bearing systems contribute the most to the embodied environmental impacts. This is because of their big mass and energy intensive construction process. These observations suggest that reusing structural elements has large potential to reduce the environmental footprint of building structures. Reused components may consequently have a longer service life than the systems to which they initially belonged and disassembled buildings become a mine for new constructions. This idea is of course not a today’s invention, but has found application already far in the past as well as in recent building projects. Before industrialization, most building materials were sourced locally and reuse of building materials and components was the rule because it was more cost and time efficient than new production [1]. The scarcity of building materials had to be considered in design and construction. A classic example is the reuse of bricks throughout the Roman and Greek eras or in post-war times. Remarkable are also the stone columns of the Great Mosque of Cordoba, Spain, which were reused from nearby Roman and Visigoth ruins to support Moorish double arches (Fig. 1a). More recently, the steel structure of the BedZED project in London (Fig. 1b) was constructed from 90 % locally reclaimed elements [2]. Many other contemporary case studies in which bricks, timber, or steel elements have been reused are reported in [1] and [2]. An outstanding structure is the London Olympic Stadium (Fig. 1c), whose roof truss incorporates 2000 tons of steel pipeline tubes reused from a nearby development project [3]. At smaller scale, a strained grid-shell pavilion made of reclaimed skis has been built by the researchers at EPFL’s Structural Xploration Lab (Fig 1d). Recently this environmental-aware architectural and structural design is evolving. In addition, governments have understood the potential of circular economy and circular design. For instance, the European Commission has issued an EU action plan for the circular economy in order to reduce waste and landfill. Research While historic and contemporary projects, especially in Europe, highlight the environmental, time or cost benefits of building with reclaimed (structural) elements, many technological challenges remain. Buildings have to be carefully disassembled, which is often only possible for steel or wooden structures that are joined with reversible connections, or when elements can be cut and member ends are reshaped to fit new settings. Further, the quality and structural capacity of reclaimed elements has to be ensured. Under these assumptions, this research focuses on the standpoint of composing building structures from a stock of reclaimed elements. This entails reversing the conventional design process. The constrained availability of elements dictates the layout (topology and geometry) of the designed structure due to the a-priori set geometric and mechanical properties. The design shifts towards a “form follows availability” paradigm [1]. Structural optimization methods, which traditionally seek best performing structural systems under given boundary conditions, can be extended to integrate and facilitate element reuse in structural design. This research uses the combination of combinatorial optimization and form-finding methods to design reticulated structures from a given stock of reclaimed elements [4], where: 1) available elements are grouped by material, structural capacity and dimensions, 2) an optimal assignment of a subset of stock elements into a structural system is performed, and 3) the structure geometry is optimized. Generally, the assignment step 2) minimizes the structural weight to optimally utilize the available element capacities, whereas the geometry optimization step 3) is carried out to match truss geometry and available element lengths. This method is applied to optimize truss systems subject to differently composed stocks. In each case, varying cross section sizes or element lengths result in a different outcome of the designs. Figure 2 (a) shows a typical roof truss design, which is loaded at the top chord and is used as the initial topology for the introduced optimization method. The obtained layout for the case of using Stock A is reported in Fig. 1b. This stock consist of elements with 3.00m length which are n = 4 times available for each of the six cross-section groups. The use of the stock is indicated by the superimposed magenta colored bars on top of the grey ones. Due to limitations of the stock to 3.00 m elements only, the truss layout contains two arrays of three almost equilateral triangles. For the truss made from Stock B, which is composed of equivalent cross section groups but with variable element lengths, the found geometry is shallower and vaulted. In both cases, the geometry optimization allows to use most of the stock members with their full length. The exploration of these case studies concludes that the availability of elements has a significant influence on the final structural design as well as its structural performance. For example, if an insufficient amount of elements with small cross-sections is available, the structure will be oversized (i.e. the capacity of available members is not utilized) and environmental savings are diminished. Conclusion The proposed optimization and form finding method renders a first step towards facilitating the design with reused elements where the outcome is not as predictable as in the well-established conventional structural design process. Future research will extend this method towards different structural typologies such as bending and frame systems. Further, the question of customized connection details enabling the joining of stock elements has to be addressed.

2018

Integration of LCA in a thermo-economic model for synthetic natural production from woody biomass

Martin Gassner, Léda Gerber, François Maréchal

Environmental impacts of emerging technologies such as the production of biofuels have become an important concern. To assess these impacts, life cycle assessment (LCA) is a well-established and widely used method. However, conventional LCAs for these technologies are generally based on an average technology at lab- or pilot-scale. Therefore, the changes in process design, future installation size and technology evolution are not considered. Moreover, it is not possible for engineers to use the LCA as a design tool at the conception stage to target not only economic competitiveness and energy efficiency, but also minimal environmental impacts. The objective of the present survey was to develop a methodology allowing to link process design and scaling with the LCA. It is illustrated by an application to an existing thermo-economic model used for the multi-objective optimization of the thermo-chemical production of synthetic natural gas (SNG) from woody biomass. First, the functional unit (FU) and the system limits are defined for the LCA model, according to the established LCA methodology. In the present case, a cradle-to-gate LCA approach was applied, and the chosen FU was 1 MJout of SNG, ready to be injected in the gas grid. All the energy or materials flows of environmental concern falling within these boundaries as input or output are identified and form the life cycle inventory (LCI). Secondly, the driving parameters which allow for quantifying the LCI flows as a function of the process design and scale are identified. These driving parameters are then directly taken from the thermo-economic model to perform the scaling of the LCI within the LCA model. If some of these parameters relevant for the LCA are not available from the thermo-economic model, the latter is extended. Each LCI flow is thus adapted to the process design and scale. Necessary process equipment for plant infrastructure is also included in the LCI, and its impacts are scaled. The life cycle impact assessment (LCIA) is then performed with one or more established impact assessment methods in order to interpret a particular process design in terms of environmental consequences. The obtained model including both the LCA and thermo-economic parts can be termed as a thermo-environomic model. The environmental indicators given by the LCIA of such a model were used in the frame of an economic optimization at multiple scale for six different scenarios for SNG production, representing different technological choices and stages of technology evolution. The effects of economic optimization on the environmental impacts were then studied. It appeared that for five of the six scenarios studied, there was a trade-off between SNG production costs and environmental impacts, since costs were decreasing while impacts were increasing with respect to installation size.

2009

Socio-Economic Assessment of Fusion Energy Research, Development, Demonstration and Deployment Programme

Denis Bednyagin

Providing safe, clean and affordable energy supply is essential for meeting the basic needs of human society and for supporting economic growth. From the historical perspective, the constantly growing energy use was one of the main factors, which drove the industrialised countries to the current level of prosperity. Meanwhile, in recent decades, the issue of global energy security became a topic of increasing concern in the international policy agenda. On the one hand, the world is facing the problem of exhaustion of most convenient and cheep fuel reserves. The situation is becoming worse, because of the constantly growing demand in developing countries, and the oligopolistic behaviour of major energy exporting countries. On the other hand, the society is becoming more and more sensitive to the environmental pollution problems, caused by the excessive consumption of fossil fuels. In the face of energy security challenge, national governments ought to implement adequate strategies aimed at liberalisation of energy markets, diversification of energy supply mix, enhancement of energy efficiency, encouragement of investments in energy infrastructures, and promotion of innovation in energy sector. In a longer term perspective, the latter point becomes increasingly important, because the world is relying currently on the consumption of non-renewable fossil fuels, and the development of new safe, clean and resource unconstraint energy technologies is vitally needed. In line with this strategy, the major world economies pursue the joint R&D programme on thermonuclear Fusion technology, which represents numerous advantages due to its inherent safety, avoidance of CO2 emissions, relatively small environmental impact, abundance and world-wide uniform distribution of fuel resources. Considering the importance of the projected environmental and economic benefits of Fusion, the questions are raised whether the current level of financial support is sufficient, and what could be the optimal strategy to proceed with the demonstration of Fusion technology, given the time span and potential risks of Fusion RDDD programme. To put these questions into the context, one has to consider the current trends in energy R&D funding, which has seen a drastic decline ( ~50%) over the last three decades. The liberalisation of energy sector poses additional problem due to the fact that free markets partially failure to provide public goods, such as basic science and R&D, because of the so-called spillover effects meaning that the firms are not able to appropriate the integral results of their R&D investments. Regarding the thermonuclear Fusion technology, the decision makers responsible for national energy policies and allocation of public R&D funds may face the following specific questions: What is the expected net socio-economic payoff (social rate of return) of Fusion R&D programme, including both internal and external costs and benefits? What are the reasonable economic arguments that could justify the increase in public funding of the ongoing and future Fusion R&D activities and would stimulate greater involvement of the private sector? What additional value can be obtained through undertaking a more ambitious Fusion R&D programme (accelerated development path), which requires bigger number of experimental facilities, increased funding, and more intense overall efforts of international scientific and industrial community? In order to provide sound arguments for policymakers seeking to optimise public R&D funding, a robust socio-economic evaluation of the whole Fusion research, development, demonstration and deployment (RDDD) programme is needed. At the present stage, prospective analyses of Fusion technology have been emphasised mainly on the investigation of technological issues, estimation of the direct costs of Fusion power and analysis of its potential role in future energy systems. Meanwhile, methodological tools and practical studies aiming at a more comprehensive socio-economic assessment of global long-term energy R&D programmes, such as Fusion, are still incomplete. The primary difficulty concerns the evaluation of positive externalities that may reveal through different types of spillover effects, including but not limited to knowledge, network and market spillovers. While the presence of these effects has been identified in the economic theory and confirmed by empirical studies, their quantitative analysis in the specific case of large scale energy R&D programmes represents some methodological lacuna and deserves further investigation. Another problem relates to the methodology of cost-benefit analysis, which oftentimes ignores the hidden value of R&D projects arising due to the possible flexibility in managerial decisions. In fact, throughout the course of any R&D project, its prospective cash-flows can be significantly improved by pro-active management of different implementation stages, e.g. expanding the production, if market conditions are favourable, or abandoning, if R&D process appears to be unproductive. As a result, the strategic value of any R&D project normally exceeds its net present value (NPV) calculated with the traditional discounted cash flow (DCF) method. Although this strategic approach to capital budgeting, known as Real Options, has been propagated recently in several publications dealing with appraisal of lumpy irreversible investments, its practical application in the context of Fusion RDDD programme has not been mastered yet to the required extent. A particular challenge consists in the need for adequate treatment of different types of uncertainty in the model structure, parameters and input data. Accordingly, the main objective of this thesis consists in complementing the existing studies with an in-depth analysis of the positive externalities (spillover benefits) of Fusion RDDD programme and calculation of its strategic real options value subject to different managerial strategies throughout demonstration and deployment stages. Net social present value of Fusion RDDD programme and potential impact of Fusion R&D activities on the economic performance of the involved private companies are estimated using an integrated modelling framework, which includes the following components: (1) assessment of technological potential for deployment of Fusion power plants based on the simulation of multi-regional long term electricity supply scenarios with PLANELEC model; (2) economic evaluation of Fusion RDDD programme and analysis of different implementation strategies using Real Options model; (3) estimation of the economic value of spillover benefits from participation in Fusion R&D projects at the microeconomic level with the help of financial evaluation model; (4) strategic evaluation of Fusion RDDD programme, taking into account both spillover benefits and real options value, and policy recommendations.

EPFL2010