Project Objectives

Goals

Design a software package to operate in the Windows operating system which will:

1.   Calculate the solar energy available on a surface:

located anywhere on earth

of fixed or sun tracking orientation

at any time of day or year

for time periods of a few minutes to all day or for several days

under clear, hazy, or long term climate influenced sky conditions,

2.    Display the results of calculations in tables or graphs as appropriate to the data

Introduction

Almost any solar energy use requires the knowledge of how much is available to select the proper size collector for gathering it. Some uses require the solar energy to be concentrated to generate high enough temperatures to be useful, others do not. Often a system designer doesn't know what the best orientation is for a solar collector without some prior experience or an ability to calculate availability for a variety of orientations and then pick the best one. There is a need therefore, for a software package which will allow the user to enter or select with a mouse the parameters defining the desired collection situation and have the package output the amount of solar energy available. To model performance of a solar energy system one often needs to know solar energy availability every few minutes from sunrise to sunset on clear days; there are other modeling tasks in which one wants to know the availability over a long time period of many years, and then one must be able to take into account the amount of cloudiness, fog or haze present on average in the atmosphere at that location. Here one uses different correlations which give daily totals rather than minute by minute variation over a day.

Background

The equations and correlations needed to do the calculations are available and many years ago I implemented them in a FORTRAN language program. I compiled the file and generated an executable file for use on PCs using the MSDOS operating system. This software did not attempt to draw graphs of the results or even display complete tables of the results. It wrote the results to file names specified by the user, and displayed on the screen only a brief summary of information. To see the tables of results, one had to stop the calculation program and open the data files with a word processor or spreadsheet. Input of information was very "clunky" since one couldn't use a mouse to point and click to select items from an options table, nor could one display all entered situation information on the screen at once and have the cursor shift from one location to another as information was entered. Today's programming language environment in Visual Basic allows a user to do all of the things one should do with the software package desired. An option is to generate the on screen presentation of information in Visual Basic and the calculation of results in FORTRAN, although it seems easier to do it all in Visual Basic. Spreadsheet software and probably Mathcad or Matlab are also possible software packages for creating the solar energy availability package. Visual Basic is fairly easy to learn and uses loop and conditional execution statements similar to FORTRAN language. It is also fairly easy to generate the package's "on screen" appearance by selecting "controls" from a menu, dragging them to a location on the screen and modifying their size and a few other properties to create a "form" of pleasing appearance. An example of an input form which should work for the package is shown below. After defining the appearance of information on the screen, one then enters the language code to store the information in the screen blocks as constants so the package processes the information in each of the controls properly at calculation time.

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