DESIGN AND RELIABILITY ASSESSMENT OF HIGH POWER LED AND LED-BASED SOLID STATE LIGHTING

Lumen depreciation and color quality change of high power LED-based solid state light (SSL) are caused by the combination of various degradation mechanisms. The analytical/experimental models on the system as well as component-level are proposed to analyze the complex reliability issues of the LED-based solid SSL. On the system-level front, a systematic approach to define optimum design domains of LED-based SSL for a given light output requirement is developed first by taking cost, energy consumption and reliability into consideration. Three required data sets (lumen/LED, luminaire efficacy, and L70 lifetime) to define design domains are expressed as contour maps in terms of two most critical operating parameters: the forward current and the junction temperature (If and Tj). Then, the available domain of design solutions is defined as a common area that satisfies all the requirements of a luminaire. Secondly, a physic of failure (PoF) based hierarchical model is proposed to estimate the lifetime of the LED-based SSL. The model is implemented successfully for an LED-based SSL cooled by a synthetic jet, where the lifetime of a prototypical luminaire is predicted from LED lifetime data using the degradation analyses of the synthetic jet and the power electronics. On the component-level front, a mathematical model and an experimental procedure are developed to analyze the degradation mechanisms of high power LEDs. In the approach, the change in the spectral power distribution (SPD) caused by the LED degradation is decomposed into the contributions of individual degradation mechanisms so that the effect of each degradation mechanism on the final LED degradation is quantified. It is accomplished by precise deconvolution of the SPD into the leaked blue light and the phosphor converted light. The model is implemented using the SPDs of a warm white LED with conformally-coated phosphor, obtained before and after 9,000 hours of operation. The analysis quantifies the effect of each degradation mechanism on the final values of lumen, CCT and CRI

Development of effective thermal management strategies for LED luminaires

The efficacy, reliability and versatility of the light emitting diode (LED) can outcompete most established light source technologies. However, they are particularly sensitive to high temperatures, which compromises their efficacy and reliability, undermining some of the technology s key benefits. Consequently, effective thermal management is essential to exploit the technology to its full potential. Thermal management is a well-established subject but its application in the relatively new LED lighting industry, with its specific constraints, is currently poorly defined. The question this thesis aims to answer is how can LED thermal management be achieved most effectively? This thesis starts with a review of the current state of the art, relevant thermal management technologies and market trends. This establishes current and future thermal management constraints in a commercial context. Methods to test and evaluate the thermal management performance of a luminaire system follow. The defined test methods, simulation benchmarks and operational constraints provide the foundation to develop effective thermal management strategies. Finally this work explores how the findings can be implemented in the development and comparison of multiple thermal management designs. These are optimised to assess the potential performance enhancement available when applied to a typical commercial system. The outcomes of this research showed that thermal management of LEDs can be expected to remain a key requirement but there are hints it is becoming less critical. The impacts of some common operating environments were studied, but appeared to have no significant effect on the thermal behaviour of a typical system. There are some active thermal management devices that warrant further attention, but passive systems are inherently well suited to LED luminaires and are readily adopted so were selected as the focus of this research. Using the techniques discussed in this thesis the performance of a commercially available component was evaluated. By optimising its geometry, a 5 % decrease in absolute thermal resistance or a 20 % increase in average heat transfer coefficient and 10 % reduction in heatsink mass can potentially be achieved . While greater lifecycle energy consumption savings were offered by minimising heatsink thermal resistance the most effective design was considered to be one optimised for maximum average heat transfer coefficient. Some more radical concepts were also considered. While these demonstrate the feasibility of passively manipulating fluid flow they had a detrimental impact on performance. Further analysis would be needed to conclusively dismiss these concepts but this work indicates there is very little potential in pursuing them further

Potential for Solar Energy in Food Manufacturing, Distribution and Retail

The overall aim of the study was to assess the potential for increasing the use of solar energy in the food sector. For comparative purposes the study also included an assessment of the benefits that could arise from the use of other renewable energy sources, and the potential for more effective use of energy in food retail and distribution. Specific objectives were to: i) establish the current state of the art in relevant available solar technology; ii) identify the barriers for the adoption of solar technology; iii) assess the potential for solar energy capture; iv) appraise the potential of alternative relevant technologies for providing renewable energy; v) assess the benefits from energy saving technologies; vi) compare the alternative strategies for the next 5-10 years and vii) Consider the merits of specific research programmes on solar energy and energy conservation in the food sector. To obtain the views of the main stakeholders in the relevant food and energy sectors on the opportunities and barriers to the adoption of solar energy and other renewable energy technologies by the food industry, personal interviews and structured questionnaires tailored to the main stakeholders (supermarkets, consultants for supermarket design; energy and equipment suppliers) were used. The main findings from the questionnaires and interviews are: - Key personnel in supermarkets and engineers involved in the design of supermarkets are aware of the potential contribution of renewable energy technologies and other energy conservation measures to energy conservation and environmental impact reduction in the food industry. A number of supermarket chains have implemented such technologies at pilot scale to gain operating experience, and more importantly, for marketing reasons, to gain competitive advantage through a green image. - From installations to date in the UK the most notable are a 600 kW wind turbine at a Sainsbury's distribution centre in East Kilbride and a 60 kWp photovoltaic array at a Tesco store in Swansea. - The main barrier to the application of renewable energy technologies in the food sector is the capital cost. Even though significant progress has been made towards the improvement of the energy conversion efficiencies of photovoltaic technologies (PVs) and reduction in their cost, payback periods are still far too long, for them to become attractive to the food industry. - Wind energy can be more attractive than PVs in areas of high wind speed. Apart from relatively high cost, the main barrier to the wide application of wind turbines for local power generation is planning restrictions. This technology is more attractive for application in food distribution centres that are normally located outside build-up areas where planning restrictions can be less severe than in urban areas. In these applications it is likely that preference will be for large wind turbines of more than 1.0 MW power generation capacity as the cost of generation per unit power reduces with the size of the turbine

Controlled Ecological Life Support Systems (CELSS) conceptual design option study

Results are given of a study to explore options for the development of a Controlled Ecological Life Support System (CELSS) for a future Space Station. In addition, study results will benefit the design of other facilities such as the Life Sciences Research Facility, a ground-based CELSS demonstrator, and will be useful in planning longer range missions such as a lunar base or manned Mars mission. The objectives were to develop weight and cost estimates for one CELSS module selected from a set of preliminary plant growth unit (PGU) design options. Eleven Space Station CELSS module conceptual PGU designs were reviewed, components and subsystems identified and a sensitivity analysis performed. Areas where insufficient data is available were identified and divided into the categories of biological research, engineering research, and technology development. Topics which receive significant attention are lighting systems for the PGU, the use of automation within the CELSS system, and electric power requirements. Other areas examined include plant harvesting and processing, crop mix analysis, air circulation and atmosphere contaminant flow subsystems, thermal control considerations, utility routing including accessibility and maintenance, and nutrient subsystem design

Screening of energy efficient technologies for industrial buildings' retrofit

This chapter discusses screening of energy efficient technologies for industrial buildings' retrofit

A Practical Review to Support the Implementation of Smart Solutions within Neighbourhood Building Stock

The construction industry has witnessed an increase in the use of digital tools and smart solutions, particularly in the realm of building energy automation. While realising the potential benefits of smart cities, a broader scope of smart initiatives is required to support the transition from smart buildings towards smart neighbourhoods, which are considered critical urban development units. To support the interplay of smart solutions between buildings and neighbourhoods, this study aimed to collect and review all the smart solutions presented in existing scientific articles, the technical literature, and realised European projects. These solutions were classified into two main sections, buildings and neighbourhoods, which were investigated through five domains: building-energy-related uses, renewable energy sources, water, waste, and open space management. The quantitative outcomes demonstrated the potential benefits of implementing smart solutions in areas ranging from buildings to neighbourhoods. Moreover, this research concluded that the true enhancement of energy conservation goes beyond the building’s energy components and can be genuinely achieved by integrating intelligent neighbourhood elements owing to their strong interdependencies. Future research should assess the effectiveness of these solutions in resource conservation

Energy-led, non-domestic building refurbishment : decision support for a whole-building approach to improvement of operational performance

Pressure is growing upon non-domestic building owners and occupiers to measure and improve the energy performance, and associated carbon emission levels, of the portfolio in which they operate. In line with this, the need for energy-led refurbishment of existing buildings is increasingly evident, with approximately 60% of the current building stock expected to still exist in 2050 and less than 1% being replaced annually. However, energy-led refurbishment of existing non-domestic property faces a number of barriers, including an ill-defined decision-making process and a lack of low carbon skills required to guide building owners in this complex transition. This thesis examines first, the need for a re-alignment of disciplines within the construction industry to fulfil the growing requirement for low carbon skills, specific to energy-led refurbishment. A comprehensive desk study was undertaken, evaluating the competencies of the established construction industry professions, as defined by their governing bodies. This was supported by structured interviews with users of large, nondomestic property and industry professionals to establish whether a need existed and how they proposed it be fulfilled. A deficiency in expertise was identified, and from this a competency specification for professionals leading energy-led refurbishment in existing, non-domestic property has been developed. Second, this thesis explores the different forms of automated decision support within the construction sector, identifying opportunities for a structured decision-making approach to energy-led refurbishment. An optimum decision support tool (DST) process was proposed, consisting of seven steps from assessment of the existing building’s state through to continuous evaluation and improvement of the refurbished building. A key module within this process was developed in detail to address the complex multiple attribute decision making (MADM) approach required during selection of energy performance improvement measure (EPIM). A set of assessment criteria, addressing a variety of performance characteristics, was designed using an online Delphi survey with a select group of ‘energy in buildings’ experts. The criteria range from short term impact (EPIM installation) to long term impact (EPIM operation and disposal) upon the existing property’s performance. Subsequent weighting of the assessment criteria in terms of their relative importance was undertaken using the same expert group through a paired comparison survey methodology. This revealed the relative importance of each criterion, consequently aiding prioritisation of EPIMs within the optimum DST and supporting decision-making

Improving Building Sustainability: Lighting Life Cycle Optimization and Management, and HVAC Demand Response

Residential and commercial buildings represent 39% of global energy carbon emissions. In the U.S., buildings consume 40% of the total energy consumption and thus represent a substantial energy saving opportunity. Additionally, building energy flexibility, or the ability to reduce or move demand to a different time, is playing an increasingly important role in grid modernization and renewable integration by helping to balance supply. Material efficiency is another foundation to sustainability, as many energy-efficient and renewable technologies depend on the use of specialty materials, which are dwindling in supply and many face geopolitical conflicts. This dissertation advances methods of life cycle analysis and data analytics while addressing some of these issues and opportunities in three key aspects – how to choose better products, how to better manage products at their end of life, and how to use energy more effectively. Chapter 2 and 3 examine the keep vs. replace conundrum by studying the replacement of residential and commercial lighting, in which the rapidly changing LED technology creates unclear tradeoffs with incumbent lighting in terms of cost, energy savings, and emissions. The results suggest that while LED lighting offers competitive performance and life cycle cost as fluorescent lighting, there is less advantage (or benefit) for immediate LED adoption in a lower use, upfront cost-sensitive, or slowly decarbonizing grid situation. Chapter 4 evaluates the life cycle impacts of recovering rare earth and critical metals from spent linear fluorescent and LED fixtures, respectively. This chapter also assesses the impacts of extended use and modular (component) replacement to assess the value of reverse logistics (reuse, remanufacturing, and recycling). The results show that both types of metal extraction create net environmental impacts, which can be mitigated with process optimization and waste preprocessing to increase extraction efficiency. While modular replacement leads to overall lower environmental burdens, full replacement can offer incentive for LED recycling as their metal-heavy housing structure and heat sink are attractive to recyclers. Chapter 5 performs piecewise log-linear-Fourier regressions on whole-home smart meter data and outdoor temperature data to disaggregate the thermostatically controlled loads from whole-home consumption and to estimate the technical thermal demand response potentials in the Midwest. The results suggest that single family buildings, being the higher energy users and larger customer base than multi-family, can provide higher per customer and aggregated demand flexibility. However, multi-family buildings, particularly those with a central HVAC system, may have the advantage of pooled demand across multiple units and should therefore be considered accordingly. By examining the three decision-making questions related to technology and product selection (Chapter 2 - 3), waste management and material recovery (Chapter 4), and energy use and demand response (Chapter 5), the research helps inform decision making for building managers and energy consumers, and provide industry with insights regarding product design, reverse logistics, and demand response program recruitment.PHDMech Eng & Nat Res Env PhDUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/163086/1/lixiliu_1.pd