Effect of building integrated photovoltaics on microclimate of urban canopy layer

Building integrated photovoltaics (BIPV) has potential of becoming the mainstream of renewable energy in the urban environment. BIPV has significant influence on the thermal performance of building envelope and changes radiation energy balance by adding or replacing conventional building elements in urban areas. PTEBU model was developed to evaluate the effect of photovoltaic (PV) system on the microclimate of urban canopy layer. PTEBU model consists of four sub-models: PV thermal model, PV electrical performance model, building energy consumption model, and urban canyon energy budget model. PTEBU model is forced with temperature, wind speed, and solar radiation above the roof level and incorporates detailed data of PV system and urban canyon in Tianjin, China. The simulation results show that PV roof and PV façade with ventilated air gap significantly change the building surface temperature and sensible heat flux density, but the air temperature of urban canyon with PV module varies little compared with the urban canyon of no PV. The PV module also changes the magnitude and pattern of diurnal variation of the storage heat flux and the net radiation for the urban canyon with PV increase slightly. The increase in the PV conversion efficiency not only improves the PV power output, but also reduces the urban canyon air temperature. © 2006.

Effect of urban climate on building integrated photovoltaics performance

It is generally recognized that BIPV (building integrated photovoltaics) has the potential to become a major source of renewable energy in the urban environment. The actual output of a PV module in the field is a function of orientation, total irradiance, spectral irradiance, wind speed, air temperature, soiling and various system-related losses. In urban areas, the attenuation of solar radiation due to air pollution is obvious, and the solar spectral content subsequently changes. The urban air temperature is higher than that in the surrounding countryside, and the wind speed in urban areas is usually less than that in rural areas. Three different models of PV power are used to investigate the effect of urban climate on PV performance. The results show that the dimming of solar radiation in the urban environment is the main reason for the decrease of PV module output using the climatic data of urban and rural sites in Mexico City for year 2003. The urban PV conversion efficiency is higher than that of the rural PV system because the PV module temperature in the urban areas is slightly lower than that in the rural areas in the case. The DC power output of PV seems to be underestimated if the spectral response of PV in the urban environment is not taken into account based on the urban hourly meteorological data of Sao Paulo for year 2004. © 2006 Elsevier Ltd. All rights reserved.

Influence of a building's integrated-photovoltaics on heating and cooling loads

Building integrated photovoltaics (BIPV) has the potential to become a major source of renewable energy in the urban environment. BIPV has significant influence on the heat transfer through the building envelope because of the change of the thermal resistance by adding or replacing the building elements. Four different roofs are used to assess the impacts of BIPV on the building's heating-and-cooling loads; namely ventilated air-gap BIPV, non-ventilated (closed) air-gap BIPV, closeroof mounted BIPV, and the conventional roof with no PV and no air gap. One-dimensional transient models of four cases are derived to evaluate the PV performances and building cooling-and-heating loads across the different roofs in order to select the appropriate PV building integration method in Tianjin, China. The simulation results show that the PV roof with ventilated air-gap is suitable for the application in summer because this integration leads to the low cooling load and high PV conversion efficiency. The PV roof with ventilation air-gap has a high time lag and small decrement factor in comparison with other three roofs and has the same heat gain as the cool roof of absorptance 0.4. In winter, BIPV of non-ventilated air gap is more appropriate due to the combination of the low heating-load through the PV roof and high PV electrical output. © 2005 Elsevier Ltd. All rights reserved.

Interactions between Building Integrated Photovoltaics and microclimate in urban environments

BIPV(Building Integrated Photovoltaics) has progressed in the past years and become an element to be considered in city planning. BIPV has influence on microclimate in urban environments and the performance of BIPV is also affected by urban climate. The effect of BIPV on urban microclimate can be summarized under the following four aspects. The change of absorptivity and emissivity from original building surface to PV will change urban radiation balance. After installation of PV, building cooling load will be reduced because of PV shading effect, so urban anthropogenic heat also decreases to some extent. Because PV can reduce carbon dioxide emissions which is one of the reasons for urban heat island, BIPV is useful to mitigate this phenomena. The anthropogenic heat will alter after using BIPV, because partial replacement of fossil fuel means to change sensible heat from fossil fuel to solar energy. Different urban microclimate may have various effects on BIPV performance that can be analyzed from two perspectives. Firstly, BIPV performance may decline with the increase of air temperature in densely built areas because many factors in urban areas cause higher temperature than that of the surrounding countryside. Secondly, the change of solar irradiance at the ground level under urban air pollution will lead to the variation of BIPV performance because total solar irradiance usually is reduced and each solar cell has a different spectral response characteristic. The thermal model and performance model of ventilated BIPV according to actual meteorologic data in Tianjin(China) are combined to predict PV temperature and power output in the city of Tianjin. Then, using dynamic building energy model, cooling load is calculated after BIPV installation. The calculation made based in Tianjin shows that it is necessary to pay attention to and further analyze interaction between them to decrease urban pollution, improve BIPV Performance and reduce colling load. Copyright © 2005 by ASME.

Operation of a high frequency piezoelectric ultrasound array with an application specific integrated circuit

Integration of a piezoelectric high frequency ultrasound (HFUS) array with a microfabricated application specific integrated circuit (ASIC) performing a range of functions has several advantages for ultrasound imaging. The number of signal cables between the array/electronics and the data acquisition / imaging system can be reduced, cutting costs and increasing functionality. Electrical impedance matching is also simplified and the same approach can reduce overall system dimensions for applications such as endoscopic ultrasound. The work reported in this paper demonstrates early ASIC operation with a piezocomposite HFUS array operating at approximately 30 MHz. The array was tested in three different modes. Clear signals were seen in catch-mode, with an external transducer as a source of ultrasound, and in pitch-mode with the external transducer as a receiver. Pitch-catch mode was also tested successfully, using sequential excitation on three array elements, and viable signals were detected. However, these were relatively small and affected by interference from mixed-signal sources in the ASIC. Nevertheless, the functionality and compatibility of the two main components of an integrated HFUS - ASIC device have been demonstrated and the means of further optimization are evident.

Tuneable planar integrated optical systems

Planar integrated free-space optical systems are well suited for a variety of applications, such as optical interconnects and security devices. Here, we demonstrate dynamic functionality of such microoptical systems by the integration of adaptive liquid-crystal-devices. © 2007 Optical Society of America.

Integrated avalanche diode for 600 v Trench IGBT over-voltage protection

Avalanche multiplication has been one of the major destructive failure mechanisms in IGBTs; in order to avoid operating an IGBT under abnormal conditions, it is desirable to develop peripheral protecting circuits monolithically integrated without compromising the operation and performance of the IGBT. In this paper, a monolithically integrated avalanche diode (D av) for 600V Trench IGBT over-voltage protection is proposed. The mix-mode transient simulation proves the clamping capability of the D av when the IGBT is experiencing over-voltage stress in unclamped inductive switching (UIS) test. The spread of avalanche energy, which prevents hot-spot formation, through the help of the avalanche diode feeding back a large fraction of the avalanche current to a gate resistance (R G) is also explained. © 2011 IEEE.

Modular distributed manufacturing systems and the implications for integrated control

Driven by the need for more responsive manufacturing processes and as a consequence of increasing complexity in products and production systems, this short paper introduces a number of developments in the area of modular, distributed manufacturing systems. Requirements for the development of such systems are addressed and, in particular, the relevance to current and future integrated control systems is examined. One of the key issues for integrated control systems in the future is the need to provide support for distributed decision-making in addition to existing distributed control capabilities.

SoC energy savings = reduce+reuse+recycle: A case study using a 660MHz DC-DC converter with integrated output filter

This paper advocates 'reduce, reuse, recycle' as a complete energy savings strategy. While reduction has been common to date, there is growing need to emphasize reuse and recycling as well. We design a DC-DC buck converter to demonstrate the 3 techniques: reduce with low-swing and zero voltage switching (ZVS), reuse with supply stacking, and recycle with regulated delivery of excess energy to the output load. The efficiency gained from these 3 techniques helps offset the loss of operating drivers at very high switching frequencies which are needed to move the output filter completely on-chip. A prototype was fabricated in 0.18μm CMOS, operates at 660MHz, and converts 2.2V to 0.75-1.0V at ∼50mA.1 © 2008 IEEE.

A 660MHz ZVS DC-DC converter using gate-driver charge-recycling in 0.18μm CMOS with an integrated output filter

The design and manufacture of a prototype chip level power supply is described, with both simulated and experimental results. Of particular interest is the inclusion of a fully integrated on-chip LC filter. A high switching frequency of 660MHz and the design of a device drive circuit reduce losses by supply stacking, low-swing signaling and charge recycling. The paper demonstrates that a chip level converter operating at high frequency can be built and shows how this can be achieved, using zero voltage switching techniques similar to those commonly used in larger converters. Both simulations and experimental data from a fabricated circuit in 0.18μm CMOS are included. The circuit converts 2.2V to 0.75∼1.0V at ∼55mA. ©2008 IEEE.