Estimating the potential of U.S. urban infrastructure albedo enhancement as climate mitigation in the face of climate variability

The climate mitigation potential of U.S. urban infrastructure albedo enhancement is explored using multidecadal regional climate simulations. Increasing albedo from 0.2 to 0.4 results in summer daytime surface temperature decreases of 1.5°C, substantial reductions in health-related heat (50% decrease in days with danger heat advisory) and decreases in energy demand for air conditioning (15% decrease in cooling degree days) over the U.S. urban areas. No significant impact is found outside urban areas. Most regional modeling studies rely on short simulations; here, we use multidecadal simulations to extract the forced signal from the noise of climate variability. Achieving a ±0.5°C margin of error for the projected impacts of urban albedo enhancement at a 95% confidence level entails using at least 5 simulation years. Finally, single-year higher-resolution simulations, requiring the same computing power as the multidecadal coarser-resolution simulations, add little value other than confirming the overall magnitude of our estimates.This work was supported by the Concrete Sustainability Hub at MIT, with sponsorship provided by the Portland Cement Association and the RMC Research & Education Foundation, and by the US Department of Energy, Office of Biological and Environmental Research, under grant DE-FG02-94ER61937. The MIT Joint Program on the Science and Policy of Global Change is funded by a number of federal agencies and a consortium of 40 industrial and foundation sponsors. For a complete list of sponsors, see http://globalchange.mit.edu

Changing Paths: The Impact of Manufacturing Offshore on Technology Development Incentives in the Optoelectronics Industry

This paper presents a case study of the impact of manufacturing offshore on the technological trajectory of the firm and the industry. It looks in particular at the optoelectronics industry. The paper uses a combination of simulation modeling and qualitative research methods to develop grounded theory. The results suggest that firms face an important dilemma. In the case of optoelectronic firms, they are able to reduce short-term costs by manufacturing offshore; however, manufacturing offshore creates a combination of cost and knowledge constraints which limit the firms’ ability to pursue critical innovations. These results are also of interest to those concerned with trade policy. The interest here is two fold. First, the optoelectronics industry is of strategic importance in the evolution of industrial technology and thus is important to national policy. The paper’s principal finding that manufacturing offshore reduces incentives for innovation raises serious questions about the appropriateness of an offshore manufacturing policy in the long run. Second, the case challenges more generally conventional theories of trade, particularly their underlying assumptions about the long term dynamic effects which work through technological change. This case raises the troublesome question of whether these effects might be generally perverse and reduce or possibly eliminate the gains from trade over the long term

Channel plasmon subwavelength waveguide components including interferometers and ring resonators

Abstract: In recent years, many nanophotonic devices have been developed. Much attention has been given to the waveguides carrying surface plasmon polariton modes with subwavelength confinement and long propagation length. However, coupling far field light into a nano structure is a significant challenge. In this work, we present an architecture that enables high efficiency excitation of nanoscale waveguides in the direction normal to the waveguide. Our approach employs a bowtie aperture to provide both field confinement and high transmission efficiency. More than six times the power incident on the open area of the bowtie aperture can be coupled into the waveguide. The intensity in the waveguide can be more than twenty times higher than that of the incident light, with mode localization better than λ 2 /250. The vertical excitation of waveguide allows easy integration. The bowtie aperture/waveguide architecture presented in this work will open up numerous possibilities for the development of nanoscale optical systems for applications ranging from localized chemical sensing to compact communication devices

Cascaded logic gates in nanophotonic plasmon networks

Optical computing has been pursued for decades as a potential strategy for advancing beyond the fundamental performance limitations of semiconductor-based electronic devices, but feasible on-chip integrated logic units and cascade devices have not been reported. Here we demonstrate that a plasmonic binary NOR gate, a 'universal logic gate', can be realized through cascaded OR and NOT gates in four-terminal plasmonic nanowire networks. This finding provides a path for the development of novel nanophotonic on-chip processor architectures for future optical computing technologies

Determining molecular orientation via single molecule SERS in a plasmonic nano-gap

In this work, plasmonic nano-gaps consisting of a silver nanoparticle coupled to an extended silver film have been fully optimized for single molecule Surface-Enhanced Raman Scattering (SERS) spectroscopy. The SERS signal was found to be strongly dependent on the particle size and the molecule orientation with respect to the field inside the nano-gap. Using Finite Difference Time Domain (FDTD) simulations to complement the experimental measurements, the complex interplay between the excitation enhancement and the emission enhancement of the system as a function of particle size were highlighted. Additionally, in conjunction with Density Functional Theory (DFT), the well-defined field direction in the nano-gap enables to recover the orientation of individual molecules

Design for Location: The Impact of Manufacturing Offshore on Technology Competitiveness in the Optoelectronics Industry

Atlanta Conference on Science and Innovation Policy 2009This presentation was part of the session : Globalization of Science and InnovationM.I.T. Microphotonics Cente

Understanding Associated Effects of Policy Tools in Promoting Industrial Ecology in the Construction Industry: Case Studies of European Virgin Material Tax and US Forest Management Regulations

11th Annual International Sustainable Development Research Society (ISDRS) Conference, Helsinki, Finland, 6-8 Jun 200

Actionable insights with less data: guiding early building design decisions with streamlined probabilistic life cycle assessment

Abstract Purpose Two obstacles that impede wider use of life cycle assessment (LCA) are its time- and data-intensiveness and the credibility surrounding its results—challenges that grow with the complexity of the product being analyzed. To guide the critical early-design stages of a complicated product like a building, it is important to be able to rapidly estimate environmental impacts with limited information, quantify the resulting uncertainty, and identify critical parameters where more detail is needed. Methods The authors have developed the Building Attribute to Impact Algorithm (BAIA) to demonstrate the use of streamlined (not scope-limiting), probabilistic LCA for guiding the design of a building from early stages of the design process when many aspects of the design are unknown or undecided. Early-design uncertainty is accommodated through under-specification—characterizing the design using the available level of detail—and capturing the resulting variability in predicted impacts through Monte Carlo simulations. Probabilistic triage with sensitivity analyses identifies which uncertain attributes should be specified further to increase the precision of the results. The speed of the analyses allows for sequentially refining key attributes and re-running the analyses until the predicted impacts are precise enough to inform decision-making, such as choosing a preferable design alternative. Results and discussion Twelve design variants for a hypothetical single-family residential building are analyzed. As information is sequentially added to each variant, the significance of the difference in performance between each variant pair is calculated to determine when enough information has been added to resolve the designs (identify which design is preferable) with high confidence. At the sixth step in the analysis, all variant pairs whose mean impacts differ by at least 4% are resolvable with 90% confidence, even though only six attributes are specified and dozens of attributes remain under-specified. Furthermore, the comparative results for each variant pair are validated against a set of conventional LCA results, showing that BAIA identifies the correct preferable design among each resolvable pair at this step. Conclusions Iterative specification guided by probabilistic triage can help identify promising early-design alternatives even when details are only provided for key attributes. The analysis of hypothetical design variants demonstrates that BAIA is both efficient (arrives at statistically defensible conclusions from design variant comparisons based on few pieces of information) and effective (identifies the same preferable design variants as conventional LCAs)

What is the potential for prefabricated buildings to decrease costs and contribute to meeting EU environmental targets?

The European Union (EU-27) targets buildings’ decarbonization by 2050, and prefabrication presents an op-portunity to reduce buildings and construction sector impacts. A stock-based approach was developed to measure the influence of wide adoption of building prefabrication in the EU-27 building stock from 2020 to 2050. Impacts and costs of five typologies using conventional or prefabricated construction systems were assessed for three cities – Lisbon, Berlin, and Stockholm – and three insulation levels. Results were calculated at the building and country levels and then combined at the stock level. Global warming (GW) varies between 5kgCO2eq/m2 for prefabricated light steel framing (prefab_LSF) medium- or a high-rise in France and 85kgCO2eq/m2 for the conventional concrete single-family (SF) in Poland. Life cycle costs vary between around 900€/m2 for multi- family buildings in prefabricated LSF in Bulgaria and over 11 000€/m2 for an SF in conventional concrete in Luxembourg. Prefabrication can further decrease building stock burdens up to 6% and reduce building stock costs up to 10%. The developed building stock model has proven to be a fast and reliable tool to forecast the market dynamics when introducing a technological innovation, such as prefabrication. Prefabrication can contribute to achieving the EU-27 targets and reduce construction costs, increasing the construction sector’s productivity and sustainability.This work was carried out in the framework of the Sustainable Energy Systems focus area of the MIT-Portugal Program, and it was partially supported by the Portuguese Foundation for Science and Technology (FCT