W.A. Beckman

University of Wisconsin–Madison | UW · Department of Mechanical Engineering

A method for obtaining the optimum gridline spacing for photovoltaic cells operating at high solar fluxes is presented. Using a distributed resistance and diode model of a photovoltaic cell, a differential equation is obtained which relates voltage to position on the cell surface. This equation was solved numerically to obtain the maximum power poi...

The one-dimensional steady-slate temperature distribution within an isotropic porous bed subjected to a collimated and/or diffuse radiation heal flux and a transparent flowing fluid has been determined by numerical methods. The porous bed was assumed to be nonscallering and to have a constant absorption coefficient. Part of the radiation absorbed b...

The National Renewable Energy Laboratory (NREL) and the National Climatic Data Center (NCDC) have released the 1991–2005 National Solar Radiation Database (NSRDB), an update of the 1961–1990 NSRDB released in 1992. The updated NSRDB data sets are available in several forms, including an hourly ground-based data set of solar and meteorological field...

The National Renewable Energy Laboratory and collaborating agencies are working towards an update of the 30-year 1961-1990 National Solar Radiation Data Base (NSRDB). This update will include hourly solar radiation values (almost entirely modeled) for global, direct, and diffuse solar values, as well as accompanying meteorological data. The data se...

Manufacturers of photovoltaic panels typically provide electrical parameters at only one operating condition. Photovoltaic panels operate over a large range of conditions so the manufacturer’s information is not sufficient to determine their overall performance. Designers need a reliable tool to predict energy production from a photovoltaic panel u...

The National Renewable Energy Laboratory and collaborating agencies are working towards an update of the 30-year 1961-1990 National Solar Radiation Data Base (NSRDB). This update will include hourly solar radiation values (almost entirely modeled) for global, direct, and diffuse solar values, as well as accompanying meteorological data. The data se...

Solar radiation data are available for many locations on an hourly basis. Simulation studies of solar energy systems have generally used these hourly values to estimate long-term annual performance, although solar radiation can exhibit wide variations during an hour. Variations in solar radiation during an hour, such as on a minute basis, could res...

In 1992, The National Renewable Energy Laboratory (NREL) released the 1961-1990 National Solar Radiation Data Base (NSRDB), a 30-year set of hourly solar radiation data. In April 2003, NREL convened a meeting of experts to investigate issues concerning a proposed update of the NSRDB. The panel determined that an important difficulty posed by the up...

In 1992, The National Renewable Energy Laboratory (NREL) released the 1961-1990 National Solar Radiation Data Base (NSRDB), a 30-year set of hourly solar radiation data. In 2003, NREL undertook an NSRDB update project for the decade of 1991-2000. Recent work on the project includes the production of a two-year test data set, which allowed us to eva...

Immersion lithography has been proposed as a method of improving optical lithography resolution to 50 nm and below. The premise behind the concept is to increase the index of refraction in the space between the lens and wafer through the insertion of a high refractive index liquid in place of the low refractive index air that currently fills the ga...

Immersion lithography has been proposed as a method of improving optical lithography resolution to 50 nm and below. The premise behind the concept is to increase the index of refraction in the space between the lens and wafer through the insertion of a high refractive index liquid in place of the low refractive index air that currently fills the ga...

Immersion lithography has been proposed as a method of improving optical lithography resolution to 50 nm and below, by increasing the index of refraction in the space between the lens and wafer by substituting a high refractive index liquid for the low refractive index air that currently fills the gap. During exposure, energy is deposited onto the...

To extend optical lithography technology to the sub-65 nm linewidth regime, all mask-related distortions must be eliminated or minimized. Thermal distortion during the scanning exposure process can be a significant contribution to the total pattern placement error budget for advanced photomasks. This paper presents an equivalent finite element mode...

Hybrid lighting is a new approach to lighting that integrates light from natural and electric sources. A two-axis tracking concentrator collects beam radiation which is reflected onto a mirror that divides the solar radiation into infrared and visible spectra. The visible light is distributed through optical fibers and combined with fluorescent lig...

To extend optical lithography technology to the sub-65-nm linewidth regime, all mask-related distortions must be eliminated or minimized. Thermal distortion during the exposure process can be a significant contribution to the total pattern placement error budget for advanced photomasks. Consequently, several finite element (FE) models were develope...

For the 30 MWe SEGS VI parabolic trough collector plant, one task of a skilled plant operator is to maintain a specified set point of the collector outlet temperature by adjusting the volume flow rate of the heat transfer fluid circulating through the collectors. For the development of next generation SEGS plants and in order to obtain a control al...

In a solar electric generating system (SEGS), it is important to maintain a specied set point for the collector outlet temperature. Currently, a skilled plant operator adjusts the volume ¯ ow rate of the heat transfer ¯ uid circulating through the collectors to achieve this goal. In this paper, a linear model predictive controller that approximates...

Immersion lithography has been proposed as a method for improving optical lithography resolution to 50 nm. The premise behind the concept is to increase the index of refraction in the space between the lens and wafer by insertion of a high refractive index liquid in place of the low refractive index air that currently fills the gap. Because the liq...

The assumption that probability density functions of daily clearness indices are unimodal was tested. Bimodal behaviour was observed in almost 60% of 600 monthly data sets and was shown to be the most usual shape at 50 locations between latitudes 18.43°N and 64.81°N and at between 2 and 2297m above sea level. A bi-exponential probability density fu...

Extreme ultraviolet (EUV) lithography has emerged as the forerunner in the selection process to become the industry's choice as the technology for next-generation lithography (NGL). An advantageous characteristic of the EUV reticle is that it is reflective, so it can be chucked across the entirety of its backside. This chucking will aid in meeting...

The clearness index for hourly and daily radiation is an important parameter in describing solar radiation. Liu and Jordan demonstrated that the monthly average daily clearness index could be used to predict the long-term distribution of daily solar radiation in a month. This paper reviews recent literature on the prediction of hourly and daily fre...

To extend optical lithography technology to the sub-100 nm linewidth regime, all mask-related distortions must be eliminated or minimized. Thermal distortion during the exposure process can be a significant contribution to the total pattern placement error budget for advanced photomasks. Consequently, several finite element (FE) models were develop...

For analyzing systems with high solar gains it is important that design tools have a reliable and accurate means of predicting the solar radiation on surfaces. Since solar radiation on a surface is often greatly influenced by self-associated facade obstructions, neighbor buildings and the surrounding landscape, a prerequisite of solar modeling is t...

If optical lithography is to be extended into the 157 nm regime, controlling mask-related distortions will be a necessity. Thermomechanical distortions during exposure could be a major source of pattern placement error, especially if alternative materials such as CaF2 or MgF2 are employed. Full 3D finite element heat transfer and structural models...

Meeting the stringent requirements on pattern placement in the sub-130 nm regime will be a challenge for any Next Generation Lithography. A key issue for all technologies will be the development of a low distortion mask. This paper describes the thermomechanical simulations performed on the ion-beam projection lithography (IPL) mask to predict dist...

This paper presents a technique for developing models that can accurately replicate equipment performance of heat exchangers and coils. The technique employs mechanistic relations with unspecified parameters as the basis for the model relations. Catalog information is then used to estimate the best value of the parameters. Only a few geometric spec...

A search methodology for the optimum configuration of a photovoltaic pumping system in a solar domestic hot water (PV-SDHW) system is presented. The main premise of this methodology is the decoupling of the optimum search process in two phases. In phase one the goal is to find, among the possible PV pumping systems' flow rate profiles, the profile...

A method is developed to predict the long-term performance of direct-coupled PV pumping systems. The method uses only information available from the PV module and pump-motor manufacturers. Weather data are “generated” from monthly averages of horizontal radiation and ambient temperatures using well-known weather data statistics. The method predicts...

The performance of photovoltaic powered pumps in direct solar domestic hot water (PV-SDHW) systems has been studied. The direct PV- SDHW system employs a photovoltaic array, a separately excited DC- motor, a centrifugal pump, a thermal collector, and a storage tank. A search methodology for an optimum PV-SDHW system configuration has been proposed....

A methodology to assess the economic and environmental impacts of a large scale implementation of solar domestic hot water (SDHW) systems is developed. Energy, emission and demand reductions and their respective savings are quantified. It is shown that, on average, an SDHW system provides an energy reduction of about 3200 kWH, avoided emissions of...

The benefits to a utility and to the environment resulting from the installation of a large number of solar domestic hot water systems are identified and quantified. The environmental benefits of a large number of solar domestic hot water systems replacing conventional electric hot water systems include reduced energy use, reduced electrical demand...

Simulation studies of solar energy systems have traditionally been performed using hourly data because data for shorter time periods are generally unavailable for extended periods. If simulations using hourly data are to provide accurate results, the variation of radiation within an hour must have a negligible effect on a system's performance. This...

TheTRNSYS simulation program is a sequential-modular transient simulation program whichis widely used for both solar and nonsolar simulation studiesdespite its near 20-year-old origins. There have been many revisionsto TRNSYS between its original release and the current version13.1 but they have maintained the same sequential computational schemefo...

The tradeoffs between chiller and tank capacity for different load profiles and two storage strategies are evaluated in this article. Air-conditioning systems that employ ice storage incorporate equipment that produces ice during one period and melts it in another period to provide cooling for the building. In designing such systems, there are two...

A physiologically based objective function for identifying a combination of ferromagnetic seed temperatures and locations that maximizes the fraction of tumor cells killed in pretreatment planning of local hyperthermia. An objective-function is developed and coupled to finite element software that solves the bioheat transfer equation. The sensitivi...

Finite element heat-transfer models of ferromagnetic thermoseeds and catheters are developed for simulating ferromagnetic hyperthermia. These models are implemented into a general purpose, finite element computer program to solve the bioheat transfer equation. The seed and catheter models are unique in that they have fewer modeling constraints than...

This study applies indoor air quality modelling to investigate the potential advantages and drawbacks of demand-controlled ventilation as an indoor air quality control strategy. The study uses a multiple zone pollutant transport model to evaluate the performance of several indoor air quality control strate gies under a variety of conditions. The po...

Simulations provide the only practical method for designing solar energy systems. Meteorological data are needed to drive the simulations. However, long-term meteorological data (e.g., 20 years) are not available in most locations so simulations often rely on a reduced set of data or data which have been synthesized with statistical models. Even in...

The settings on the controller for a solar domestic hot water system can have major impact on the [open quotes]ratings[close quotes] obtained from a 1-day test or simulation. The settings become more critical as the effectiveness of any freeze protection heat exchanger decreases. This paper develops equations for optimal controller settings that wi...

The five computer programs TRNSYS, PRESIM, TRNSED, ONLINE and PREBID have been put together into a program package which is the most complete solar energy system modeling and simulation software that is available today.

Finite-element solutions to the Pennes bioheat equation are obtained with a model of a tumour-containing, human prostate and surrounding normal tissues. Simulations of ferromagnetic hyperthermia treatments are conducted on the tissue model in which the prostate is implanted with an irregularly spaced array of thermoseeds. Several combinations of th...

This paper explores some of the basic thermodynamic and technical considerations involved in using water as a working fluid for refrigeration and heat pump cycles down to its freezing point of 0 C. It is first shown how the integration of the functions of refrigerant and heat transfer fluid can lead to energy savings, especially for the case of ice...

Short-term experimental tests of drain-back solar water heaters are compared to ratings obtained using TRNSYS to determine if computer simulations can effectively replace laboratory thermal ratings of solar domestic hot water heating systems. The effectiveness of TRNSYS in predicting changes in rating due to limited changes in collector area, colle...

Two basic approaches are used to model the temperature distribution in thermal storage tanks for solar domestic hot water (SDHW) systems. In the multinode approach, the tank is divided into N nodes, with an energy balance written for each node. This approach results in a set of N differential equations that can be solved for the temperatures of the...

Alternative methods to provide space conditioning in supermarkets were studied. Four basic air-conditioning systems were selected for evaluation in a store in Miami, Florida: (1) conventional vapor compression systems, (2) vapor compression air-conditioning systems designed for supermarket loads, (3) hybrid desiccant air-conditioning systems, and (...

This paper presents a new method for predicting the radiative transfer in an absorbing and isotropically scattering, non-gray plane-parallel atmosphere. The technique is based upon the F̂ (“F-hat”) concept and was developed to determine the radiative transfer at short wavelengths for the transparent insulation material, monolithic silica aerogel. T...

Many previously studied natural convection enclosure problems in the literature have the bounding walls of the enclosure responsible for driving the flow. A number of relevant applications contains sources within the enclosure which drive the fluid flow and heat transfer. The motivation for this work is found in solar thermal storage tanks with imm...

The NEMO program, one of ten Finnish energy research programs, has supported research and development in wind energy storage and solar energy systems since 1988. The focus is on problems of particular interest to Finland with emphasis on technologies that may be important within the next 10 years. The projects covered the range from product develop...

A rating method for solar domestic hot water (SDHW) systems is presented that provides site-specific annual performance estimates based on ASHRAE-95 test results. An overall loss and overall gain coefficient are estimated by lumping the entire thermal behavior of the actual system exhibited during the ASHRAE-95 test into the collector parameters of...

Heat pump water heaters (HPWH) are ideally suited for water heating in restaurant applications, since restaurant kitchens have both a high demand for hot water and a nearly year round space cooling load. The heat pump can be used to heat the water while cooling the kitchen air. To account for the performance of the heat pump as both a water heater...

A methodology is developed for fault detection in heating, ventilating, and air-conditioning (HVAC) systems based on optimal control. The optimal control strategy is determined using information that could come from an energy management and control system (EMCS). This information is also used to detect faults in system operation. Deviations from op...

The influence of climatic and geometric variables on the hourly diffuse fraction has been studied, based on a data set with 22,000 hourly measurements from five European and North American locations. The goal is to determine if other predictor variables, in addition to the clearness index, will significantly educe the standard error of Liu- and Jor...

This study investigates the performance of the isotropic and four anisotropic hourly tilted surface radiation models by using monthly average hourly utilizable energy as a standard of measure. Utilizable energy is the radiation above a specified threshold level. Differences between the utilizable energy measured and the utilizable energy predicted...

Transfer function methods are more efficient for solving long-time transient heat transfer problems than Euler, Crank-Nicolson, or other classical techniques. Transfer functions relate the output of a linear, time-invariant system to a time series of current and past inputs, and past outputs. Inputs are modeled by a continuous, piecewise linear cur...

The mass incorporated in the structure of a building has long been used to store energy and offset heating requirements. The amount of mass to employ has been a subject of debate. Existing passive solar design manuals in the United States give recommendations for the amount of mass to employ in different building types, and establish optimum levels...

This paper describes a method in which the transfer functions describingheat flow in building elements can be combined into a single tranfer functionfor an enclosure, referred to as a comprehensive room transfer function (CRTF).The method accurately models long-wave radiation exchange and convection in anenclosure through an approximate network, re...

Finite difference or finite element methods reduce transient multidimensional heat transfer problems into a set of first-order differential equations when thermal physical properties are time invariant and the heat transfer processes are linear. This paper presents a method for determining the exact solution to a set of first-order differential equ...

A general method is presented for estimating the loss-of-load probability (LLP) of stand-alone photovoltaic systems. The method was developed by correlating simulation results. The simulations were driven with synthetic radiation sequences having the same statistical significance as available historical data. The method assumes a constant nighttime...

This paper investigates three sensible air coolers: a single- and a multiple-stage indirect evaporative cooler, and a combination cooling tower/heat exchanger air cooler. Relations and performance characteristics are developed. The single-stage indirect evaporative cooler is capable of cooling inlet air to temperatures approaching the inlet wet-bul...

A detailed model for use with TRNSYS, capable of modelling a wide range of boiling collector types, was used to analyze boiling flat-plate collector systems. This model can account for a subcooled liquid entering the collector, heat losses in the vapor and the liquid return line, pressure drops due to friction in the collector and piping, and press...

A performance prediction methodology is developed which is applicable to most commercially available integral collection-storage passive solar domestic hot water systems. A computer model of a general ICS component was created to be compatible with the transient simulation program TRNSYS[3], and was used to develop and verify the simpler monthly pe...

This article presents the results of a joint research effort between ASHRAE, IBM and the University of Wisconsin-Madison to optimize the HVAC process within a building. The goals of the project were to determine, via computer simulations, the effect of the time between control decisions in the dynamic control of the HVAC system and to develop HVAC...

Classical thermodynamics is based primarily upon two postulates, the first and second laws. These laws have been eloquently formulated so that they are of universal generality. Despite this apparent simplicity, understanding the concepts of thermodynamics is difficult, as most engineering students will testify. The CP/Thermo program reinforces the...

A method is presented for predicting the long-term average performance of photovoltaic systems having storage batteries and subject to any diurnal load profile. The monthly-average fraction of the load met by the system is estimated from array parameters and monthly-average meteorological data. The method is based on radiation statistics, and utili...

This paper presents the results of an investigation of open cycle cooling systems using rotary desiccant dehumidifiers. Three systems, the ventilation, recirculation, and Dunkle cycles have been modeled. The performance of these systems coupled with an air-based solar system has been determined using TRNSYS simulations of system operation in four r...

Supermarkets are major consumers of electrical energy. The presence of refrigerated cases in supermarkets makes moisture removal the primary air-conditioning requirement. Hybrid desiccant cooling systems have been proposed as an alternative to conventional vapor compression systems as a means of reducing electrical energy consumption and energy cos...

A development history is presented for the concept and methodology of solar radiation 'utilizability', which is defined as the fraction of solar radiation that is incident on a surface exceeding a specified threshold or critical level. The concept, which was initially applied to flat plate solar collector thermal performance calculations, has more...

The performance of open-cycle desiccant air conditioners for residential applications is evaluated. The performance of these systems is compared to that of vapor compression air conditioners on the basis of primary energy use and cost. Systems with improved dehumidifiers can achieve seasonal COP's on the order of 1.1. These systems, when coupled wi...

A general procedure is presented for estimating the seasonal performance of solar-assisted heat pumps with refrigerant-filled collectors. The procedure accounts for variations in collector design and orientation and also for heat pump capacity and efficiency. The results from this design procedure for space heating applications are compared against...

The f-chart design method, and the design methods based on utilizability concepts (\(\bar \Phi\) and \(\bar \Phi\) f-charts) were developed for meteorological data of North America. These methods have been built into two design programs, FCHART 3 and FCHART 4, which have been widely used to predict the performance of standard types of systems. Comp...

The extent to which a passive system degrades the performance of an active solar space heating system was investigated, and a correction factor to account for these interactions was developed. The transient system simulation program TRNSYS is used to simulate the hour-by-hour performance of combined active-passive (hybrid) space heating systems in...

A generic model of a cooled dehumidifier suitable for use in estimating the seasonal performance of cooled desiccant dehumidifier air-conditioning systems is developed. A system configuration appropriate for using a cooled dehumidifier is presented. Estimates of the seasonal performance of the cooled system are presented and compared with adiabatic...

A computationally simple algorithm is presented for evaluating the hourly utilizability function, /phi/, defined as the fraction of the long-term, monthly-average, hourly solar radiation incident on a surface which exceeds a specified threshold intensity. The algorithm was developed by correlating values of /phi/ obtained by numerical integration o...

A set of relationships is developed which allow the estimation of sol-air heating and cooling degree-days at any base temperature. The method makes use of existing relationships for hourly utilizability and degree-days, and the only input required is the monthly-average solar radiation and ambient temperature. Solar radiation which is absorbed on o...

The development of a short term in situ testing methodology and associated instrumentation is described. Test data from several SDHW systems are presented. The methodology involves a one-day or more test cycle in which tank losses and collector loop performance are measured. The measured collector loop performance includes the effect of piping loss...

This chapter offers a method which only needs the monthly average ambient temperature to obtain estimates of daily bin data and the monthly heating or cooling degree-days for any base temperature. A relationship is established between ambient temperature bin data and degree-days. Long-term temperature data for nine US locations is used to develop a...

This paper investigates the use of four different hybrid desiccant air conditioning systems in commercial buildings. The hybrid systems use a desiccant dehumidifier to provide the latent cooling, and an indirect evaporative cooler and a vapor compression machine to provide the sensible cooling. Annual air conditioning energy requirements for the fo...

A detailed hourly computer routine which models the thermal response of a building-attached sunspace has been developed for use with the TRNSYS simulation system (1). The model is described, and monthly results are compared to the Solar-Load Ratio method (2). Parametric studies demonstrate the effects of venting the sunspace air to the building, lo...