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KoSny J.,Fraunhofer Center for Sustainable Energy Systems | Biswas K.,Oak Ridge National Laboratory | Miller W.,Oak Ridge National Laboratory | Kriner S.,Metal Construction Association
Solar Energy | Year: 2012

For decades, residential and commercial roofs have been considered a prime location for installation of building integrated solar systems. In climatic conditions of East Tennessee, USA, an experimental solar roof was tested during 2009/2010, by a research team representing Metal Construction Association (MCA), and a consortium of building insulation companies, photovoltaic (PV) manufacturers, and energy research centers. The main objective was to thermally evaluate a new roofing technology utilizing amorphous silicon PV laminates integrated with the metal roof panels. In order to mitigate thermal bridging and reduce roof-generated thermal loads, this novel roof/attic assembly contained a phase change material (PCM) heat sink, a ventilated air cavity over the roof deck, and thermal insulation with an integrated reflective surface. During winter, the experimental roof was expected to work as a passive solar collector storing solar heat absorbed during the day, and increasing overall attic air temperature during the night. During summer, the PCM was expected to act as a heat sink, reducing the heat gained by the attic and consequently, lowering the building cooling-loads. In this paper, field thermal performance data of the experimental PV-PCM roof/attic system are presented and discussed. Performance of the PV-PCM roof/attic is evaluated by comparing it to a control asphalt shingle roof. The test results showed about 30% heating and 50% cooling load reductions are possible with the experimental roof configuration. © 2012 Elsevier Ltd. Source


Zeifman M.,Fraunhofer Center for Sustainable Energy Systems
IEEE Transactions on Consumer Electronics | Year: 2012

Home energy displays are emerging home energy management devices. Their energy saving potential is limited, because most display whole-home electricity consumption data. We propose a new approach to disaggregation electricity consumption by individual appliances and/or end uses that would enhance the effectiveness of home energy displays. The proposed method decomposes a system of appliance models into tuplets of appliances overlapping in power draw. Each tuplet is disaggregated using a modified Viterbi algorithm. In this way, the complexity of the disaggregation algorithm is linearly proportional to the number of appliances. The superior accuracy of the method is illustrated by a simulation example and by actual household data. © 2006 IEEE. Source


Zeifman M.,Fraunhofer Center for Sustainable Energy Systems
Conference Proceedings - IEEE International Conference on Systems, Man and Cybernetics | Year: 2014

Massive rollout of residential smart meters has spurred interest in processing the highly granular data available from these devices. Whereas the majority of smart meter data analytics is devoted to characterization of household electric appliances and their operational schedules, little work has been done to leverage these data to predict household propensity to enroll in energy efficiency and demand response programs. The state-of-the-art methodology for household enrollment prediction involves measurable household characteristics (e.g., age, household income, education, presence of children, average energy bill) and a multivariate logistic regression that connects these predictor variables with the probability to enroll. Unfortunately, the prediction accuracy of this method is just slightly better than 50%, and the required household data are not freely available to utilities/ program contractors. We developed a new method for prediction of household propensity to enroll using only hourly electricity consumption data from households' smart meters, collected over twelve months. The method implements advanced machine learning algorithms to reach an unprecedented prediction accuracy of about 90%. This level of accuracy was obtained in our study of a US West Coast behavior-based residential program. © 2014 IEEE. Source


Kosny J.,Fraunhofer Center for Sustainable Energy Systems | Kossecka E.,Polish Academy of Sciences | Brzezinski A.,LaserComp | Tleoubaev A.,LaserComp | Yarbrough D.,RandD Services
Energy and Buildings | Year: 2012

Experimental and theoretical analyses have been performed to determine dynamic thermal characteristics of fiber insulations containing microencapsulated phase change material (PCM). It was followed by a series of transient computer simulations to investigate the performance of a wood-framed wall assembly with PCM-enhanced fiber insulation in different climatic conditions. A novel lab-scale testing procedure with use of the heat flow meter apparatus (HFMA) was introduced in 2009 for the analysis of dynamic thermal characteristics of PCM-enhanced materials. Today, test data on these characteristics is necessary for whole-building simulations, energy analysis, and energy code work. The transient characteristics of PCM-enhanced products depend on the PCM content and a quality of the PCM carrier. In the past, the only existing readily-available method of thermal evaluation of PCMs utilized the differential scanning calorimeter (DSC) methodology. Unfortunately, this method required small and relatively uniform test specimens. This requirement is unrealistic in the case of many PCM-enhanced building envelope products. Small specimens are not representative of PCM-based blends, since these materials are not homogeneous. In this paper, dynamic thermal properties of materials, in which phase change processes occur, are analyzed based on a recently-upgraded dynamic experimental procedure: using the conventional HFMA. In order to theoretically analyze performance of these materials, an integral formula for the total heat flow in finite time interval, across the surface of a wall containing the phase change material, was derived. In numerical analysis of the southern-oriented wall the Typical Meteorological Year (TMY) weather data was used for the summer hot period between June 30th and July 3rd. In these simulations the following three climatic locations were used: Warsaw, Poland, Marseille, France, and Cairo, Egypt. It was found that for internal temperature of 24 °C, peak-hour heat gains were reduced by 23-37% for Marseille and 21-25% for Cairo; similar effects were observed for Warsaw. © 2012 Elsevier B.V. All rights reserved. Source


Patent
Fraunhofer Center for Sustainable Energy Systems | Date: 2011-06-21

A photovoltaic module includes a plurality of solar cells, each solar cell having an active front side and a back side. A busbar is provided and has a first portion that is electrically connected to an active front side of a first solar cell, and a second portion that is electrically connected to a back side of a second solar cell. At least a front side of the first portion of the busbar includes a diffuse reflective coating.

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