A comparison of the solar-gas and solar-electric interface

Abstract

Solar energy has several distinguishing features that bear heavily upon the eventual interfacing with gas and electric utility systems. Chief among these is its intermittent or diurnal nature, which presents differing considerations and challenges for use in conjunction with gas and electric utilities. Gas utilities provide for a winter peaking by producing year-round and storing natural gas in large underground formations, principally aquifers. Electric utilities produce on demand and rely on reserve capacity to meet summer peaks. The gas production-pipeline-storage-distribution system is chemical in nature and relatively tolerant to addition of gas of varying composition and nature. Electric systems are dynamic in nature and relatively intolerant ot the introduction of off-specification energy forms, and thus require elaborate interface protection. The storability of natural gas complements the noncontinuous aspect of solar energy and makes gas-augmented solar systems attractive. These systems can, and in many cases must, be located near the end-use site. Dispersed solar systems are attractive for electrical energy production and consumption at remote locations, for example, for irrigation water pumping. Solar electric systems that are grid connected must be of sufficient magnitude to justify the interface costs with the national grid. Solar-gas systems are preferable for space and water conditioning for homes and institutional buildings. Solar-electric systems can be either dispersed or grid connected, but the scale of technology required is considerably different in these two applications.