William O. Collinge

Enabling dynamic life cycle assessment of buildings with wireless sensor networks

This paper summarizes the goals and initial findings from a project whose aim is to create robust and practical life cycle assessment (LCA) tools to assess the performance of buildings. A central feature of this project is the concept of a dynamic LCA framework for buildings, which should include, but is not limited to; considering temporal variations in internal and external conditions during a buildings operating lifetime, and incorporating the ability to rapidly update the LCA results based on changes to the buildings design or operation (dynamic scenario modeling). A life cycle assessment (LCA) framework is necessary to understand how buildings and their occupants use materials, water, and energy resources, and are affected by the buildings internal environmental quality throughout the its lifetime. However, LCA is not commonly used in building industry practice. This disparity is hypothesized to be the result of several factors: the perceived and actual complexity of LCAs application; the lack of inclusion of internal building effects important to practitioners and users, such as indoor environmental quality (IEQ); and the lack of detailed information on the dynamics of the buildings use phase. This paper describes the feasibility of deploying a real-time, wireless sensor network to generate a dynamic LCA for buildings. Using the data collected from a sensor network, projections of the environmental impact of a buildings use phase can be validated or improved. Building systems that demonstrate a highly variable impact on the LCA results or diverge widely from current predictions can be selected for additional study, and choices regarding where to expend finite resources in sensor applications can be refined.

Towards a commodity solution for the internet of things

Embedded-class processors found in commodity palmtop computers continue to become increasingly capable. Moreover, wireless connectivity in these systems provides new opportunities in designing flexible and smarter wireless sensor networks (WSNs). In this paper, we present Lynx, a self-organizing wireless sensor network framework. Leveraging palmtop systems as sensor hubs, Lynx provides fundamental functionality to make a distributively managed, customizable WSN system implementation. Second, we describe Ocelot, a mobile distributed grid-like computing engine for commodity palmtop platforms. The combination of Lynx and Ocelot provides sensor nodes that are capable of collecting, recording, processing, and communicating data without any central server support. Significant energy savings can be achieved for light to medium weight tasks through the Lynx and Ocelot combined system compared to traditional server-class grid-solutions such as BOINC. We demonstrate Lynx and Ocelot in the context of life-cycle building energy usage.

Evaluating the Life Cycle Environmental Benefits and Trade-Offs of Water Reuse Systems for Net-Zero Buildings

Aging water infrastructure and increased water scarcity have resulted in higher interest in water reuse and decentralization. Rating systems for high-performance buildings implicitly promote the use of building-scale, decentralized water supply and treatment technologies. It is important to recognize the potential benefits and trade-offs of decentralized and centralized water systems in the context of high-performance buildings. For this reason and to fill a gap in the current literature, we completed a life cycle assessment (LCA) of the decentralized water system of a high-performance, net-zero energy, net-zero water building (NZB) that received multiple green building certifications and compared the results with two modeled buildings (conventional and water efficient) using centralized water systems. We investigated the NZBs impacts over varying lifetimes, conducted a break-even analysis, and included Monte Carlo uncertainty analysis. The results show that, although the NZB performs better in most categories than the conventional building, the water efficient building generally outperforms the NZB. The lifetime of the NZB, septic tank aeration, and use of solar energy have been found to be important factors in the NZBs impacts. While these findings are specific to the case study building, location, and treatment technologies, the framework for comparison of water and wastewater impacts of various buildings can be applied during building design to aid decision making. As we design and operate high-performance buildings, the potential trade-offs of advanced decentralized water treatment systems should be considered.

Considering fabrication in sustainable computing

The term green computing has become effectively synonymous with low-power/energy computing. However, for computing to be truly sustainable, all phases of the system life-cycle must be considered. In contrast to the considerable effort that has been applied to address the use-phase energy consumption issue - ranging from battery powered embedded systems to data center servers - there is limited awareness or attention to the considerable energy consumption and environmental impacts from semiconductor fabrication. Current research indicates that fabrication is responsible for a significant factor of the energy utilized by these systems throughout their life-cycle. The trends of technology scaling coupled with developing hybrid fabrication solutions for integration of emerging technologies, while beneficial for use-phase power consumption, exacerbate these increasing environmental impacts from fabrication. Thus, design for sustainability is a grand challenge that must be addressed over the next decade.

Green computing: A life cycle perspective

Green computing has become synonymous with low-power/energy computing. However, many environmental impacts of computing, such as manufacturing, are significant, possibly moreso than the operational/use phase. In this paper we motivate manufacturing as an issue of sustainable computing. We also demonstrate the manufacturing component of chips plays a significant role in the overall energy consumption of the computer over its life-cycle. Current trends indicate this component will increase at more aggressive technology nodes. In the context of life-cycle assessment of larger systems, manufacturing of computer systems deployed in buildings can be significant compared to the construction of the building itself.

Integrating Indoor environmental quality metrics in a dynamic life cycle assessment framework for buildings

A framework was developed for integrating indoor environmental quality (IEQ) into life cycle assessment (LCA). The framework was explored using a university building as a case study. Results showed that including IEQ aspects in whole-building LCA revealed internal impacts at least as high or higher than external impacts. For human health respiratory effects, building-specific indoor impacts from the case study were 50% higher than general impacts in conventional LCA. Tradeoffs and synergies with traditional LCA impact categories appear to result mainly from differences in energy consumption relating to different IEQ parameters such as ventilation and filtration.

Improving efficiency of wireless sensor networks through lightweight in-memory compression

Data compression is an enabling technique to many applications, such as data center storage, multimedia streaming, and lightweight computing platforms, amongst others. These special-purpose compression approaches typically achieve incomparable compression ratios as core features of the application and dataset are leveraged to reduce duplication of identical or similar features in the original data. Sensor data in systems such as wireless sensor networks, often includes a variety of data types. However, within a particular data or sensor type, typically the data has a low dynamic range which can be leveraged to increase its compressibility. In this paper we present a memory and network system co-design approach that stores data using in-place lightweight compressed pages in memory, and utilizes this compressed data to send shortened blocks over a wireless point to point network. Additionally, we propose a technique named source-aware layout reorganization (SALR) to improve the compressibility of the sensor data, using either software- or hardware-based approaches. We demonstrate that our proposed lightweight compression approach in hardware with SALR, while achieving a slightly lower compression ratio to traditional software compression, can outperform software compression in wireless communication by 7.3% for relatively slow Bluetooth links and 65.4% with faster WiFi-Direct links.

Dynamic Response of a Solid Oxide Fuel Cell Stack to Changes in a University Building’s Load

The load-following performance of a solid oxide fuel cell (SOFC) stack is investigated for meeting the power demand of a university building. A numerical model is developed based on charge, species mass, energy, and momentum balances, and an equivalent circuit is used to combine the fuel cell’s irreversibilities. The fuel cell stack is sized to meet the peak electric load of a building located on the University of Pittsburgh’s campus. The SOFC model is verified on electrochemical, mass, and thermal timescales. Results indicate that higher inlet gas pressures improve load-following by generating power closer to demand after settling has occurred, but higher pressures do not guarantee a desired power level. It is also found that lower fuel utilizations correspond to faster settling times on the mass flow timescale but with the disadvantage of lower efficiency. Lastly, it is shown that the thermal settling time decreases as the excess air ratio increases, with a slight increase in the air’s exhaust temperature.Copyright

Erratum to: Dynamic life cycle assessment: framework and application to an institutional building

Fig. 3 Comparison of results from static and DLCA models, using the TRACI method. Results are normalized to the total static LCA results for each category. Static LCA results were calculated as the total of the initial construction and projection of the initial year’s operating energy consumption for the 75-year life of the building. DLCA results are classified into four categories: original construction materials; prerenovation operations (operating energy consumption through 2008); renovation and addition materials; and post-renovation operations (operating energy consumption 2009 through end of lifetime). GW global warming potential, AC acidification potential, CA human health cancer effects, NC human health noncancer effects, RE human health respiratory effects, EU eutrophication, OD ozone depletion potential, ET ecotoxicity, PO photochemical smog, NREU nonrenewable energy use The online version of the original article can be found at http://dx.doi.org/ 10.1007/s11367-012-0528-2.

Indoor Air Quality Assessments of Diverse Buildings in an Energy Conservation District from a Life Cycle Assessment Lens: Short Paper

The historic reliance on fossil fuels as a primary energy source has made combating climate change one of the leading environmental challenges facing society today. Buildings account for 72%, 39%, 38%, and 14% of electricity consumption, energy use, carbon dioxide emissions, and water consumption, respectively [1-2]. Twelve cities have joined the Architecture 2030 District Challenge to aim to achieve 50% reductions in water use, energy consumption, and carbon emissions by the year 2030 [3]. Unique to the Pittsburghs 2030 District is the inclusion of evaluating and improving indoor air quality (IAQ). Using life cycle assessment (LCA) based models and real-time pollutant monitoring, we aim to quantify the longitudinal impact energy conservation districts (ECD) have on ambient air quality and IAQ. Indoor parameters included within our research study include ozone, carbon monoxide, carbon dioxide, temperature, relative humidity, volatile organic compounds, black carbon, and particulate matter. IAQ assessments have been completed in six representative commercial buildings ranging from LEED Platinum certified to older, building stock, vintage 1900s. Preliminary results suggest significant difference in pollutant concentrations across ventilation functionality, showing a dominant effect on pollutant dilution related to newer buildings having continuous forced air, filtered and then supplied to the workspace through fans and ducts. Older buildings rely on operable windows and window air conditioners for ventilation, which provide minimum filtration and limited manual control of outdoor air intake influenced by plumes of ambient air pollution which vary temporally and spatially, attributable to industrial and traffic sources [4].