Aharon Roy/Department of Chemical Engineering/Ben-Gurion University, P. O. Box 653, Beer-Sheva 84105, Israel. <rovaaron@.baumail. bgu. ac. il>

Phone: +(972)8-646-1484; Fax: +(972)8-647-2916.

Introduction

The hybridization of PV with a diesel or other types of fuel-fired generators is one of the ways for creating new markets, accelerating PV deployment and driving the cost down. The hybridization is a practical way for enabling the PV hybrid plant to supply uniform power and operate for a long time throughout the year. However, in order to meet environmental goals some fundamental considerations should be applied. If a renewable hybrid system is not appropriately designed, environmental achievements could diminish. So much so, that in some cases the absolute quantity of the environmental benefits of the PV subsystem (prior to fuel hybridization) may undergo a significant decline or even annihilation by the fuel used in the PV-hybrid plant. There is an immediate, acute problem to solve, how and why it happens, and to help perfect technologies amenable to a global strategy of integrating renewable energy in sustainability policies.

Green energy and sustainability

The term "green power” has come to signify electricity generated from renewable energy sources like wind, solar, geothermal and biomass. The key point is that every kilo-Watt-hour electricity (kWhe) generated from a renewable energy source is a kWhe that need not be generated from fossil or nuclear sources [1]. Namely, every green kWhe output replaces a fossil-derived kWhe; and thus must decrease the use of fuel by the amount needed for producing one kWhe. The task of green power is to mitigate pollution and global greenhouse gases and consequent future hazards; also, to decelerate world fossil reserves depletion. Thus, green power contributes to world sustainability. Various technologies are being developed worldwide for enhancing PV systems effectiveness and marketability.