Page 328 - A Comprehensive Guide to Solar Energy Systems

P. 328

Small-Scale PV Systems Used

in Domestic Applications

Nesimi Ertugrul

UNIVERSITY OF ADELAIDE, ADELAIDE, AUSTRALIA
nesimi.ertugrul@adelaide.edu.au

16.1 Introduction

Solar energy is greatly utilized by PV technology, and is simply limited by PV cell efficiency,
availability of suitable area for installation, and associated power electronics converter
technology. Commercial PV cells (Fig. 16.1A) commonly used in small domestic and indus-
trial applications have a typical working photo-electrical efficiency of 10%–20% and have
an open-circuit voltage of 600 mV, which is usually not a suitable level for practical appli-
cations [1]. To produce higher voltages and more power (between 10 and 300 W), PV cells
are interconnected (about 40) to form larger units called panels or modules (Fig. 16.1B).
Multiple modules are also installed on roofs of a building or at the ground level in a rack to
form a PV array (Fig. 16.1C), which offer much higher voltage and power levels.
In addition to multiple PV cells, a typical PV module (or panel) consists of a number of
auxiliary components which bring the module to usable form a transparent top surface
(e.g., glass); an encapsulant (to hold together the top surface and rear surface of the cells);
a rear layer (for sealing); and a metal frame around the outer edge for additional rigidity
and ease of assembly.
Note that although Fig. 16.1 illustrates a type of PV technology, the structure of end
products may vary to suit specific technology as well as target installations. For example,
architecturally and structurally integrated PV arrays are emerging in the form of roof tiles
and window glasses and with increased level of integrated power electronic circuits at cell
and string levels. To enable higher packing density on roof tops, shade-tolerant design
using static reflectors in tandem structures have also been implemented which can offer
increased power output.
Although PV technologies can come in different forms, to utilize PV energy effective-
ly, its DC output should be converted to match load characteristics of applications. A PV
module/array is rarely connected to an electrical load directly (Fig. 16.2A) unless its voltage
near the maximum power point (MPP) is higher than the operating voltage of the load. As
classified in Fig. 16.2, complexity and topology of intermediate circuits (converters, filters

323 324 325 326 327 328 329 330 331 332 333