| Description |
ix, 29 leaves : illustrations ; 29 cm + 1 CD-ROM. |
| Summary |
"In the field of innovative power sources, photovoltaics are playing an important role as a clean energy source. Because performance is dependent on instantaneous weather conditions, all stand-alone photovoltaic (PV) systems require an energy storage device. Batteries are not suitable for PV source applications due to depth of discharge restrictions, maintenance requirements and minimal power density availability. However, ultracapacitors (UCAPs) have a high power density, require little maintenance, and can be used in sequence with a dc-dc converter to maintain power output at an increased depth of discharge. This paper describes a PV-UCAP power system used to collect and compare solar radiation dependent charge rates over two voltage ranges: the traditional battery range from 35V to 48V and a longer, UCAP-specific range from 13V to 48V. A dataset of 800 charge cycles over 10 days was collected and analyzed. Using the Mann-Whitney hypothesis test, we found that the charge rates collected over the smaller voltage range are systematically different from the charge rates collected over the larger voltage range. The following three methods were used to estimate the variable instantaneous solar radiation during a given charge cycle: Simple Model of the Atmospheric Radiative Transfer of Sunshine Version 2.9.5 (SMARTS) method, vector angle of incidence (i vector) method, and direct beam solar radiation on collector (I[subscript bc]) method. The I[subscript bc] method shows the best correlation between charge rate and solar radiation estimation. The SMARTS method is preferred over the i vector method"--Abstract, leaf iv. |
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