Hydrogen as a vector for central receiver solar utilities

Abstract

An assessment is presented to use hydrogen or hydrogen-rich fuels as a vector in the Central Receiver Solar Utility (CRSU) concept. The CRSU is conceived to meet primarily the domestic energy requirements for space heating and hot water production of a community. It normally operates to provide low grade heat with sensible seasonal heat storage and district heating systems. However, there are institutional problems connected with using sensible heat storage and low grade energy distribution systems into dwellings. An alternative to this would be to produce hydrogen and hydrogen-rich fuels by using an advanced conversion technology and eliminate low grade heat storage and distribution systems. Two developing technologies, namely high temperature electrolysis and thermochemical processes, are considered for production of the vector. Then, an assessment is carried out at the conceptual level for fully dedicated Central Receiver Solar Utility Plants which integrate a central receiver system, thermochemical plant or electrical power generating system and synthetic fuel production plant with necessary auxiliary sub-systems. It is shown that for a 10% capital recovery factor, the cost of hydrogen at the plant will be about $18 per GJ using thermochemical processes and about $20 per GJ using high temperature electrolysis processes. The solar-hydrogen can also be converted to a more easily stored fuel for domestic use such as methanol, ethanol, ammonia or fuel oil. In this case, there is a distinct possibility that by using waste heavy fuels, tar sands and biomass, the cost of synthetic fuel can be considerably reduced.