J. Hill’s scientific contributions

A series of studies were undertaken to assess the safety hazards in proposed solar thermal power systems (STPS). Among the risks identified are distributed heliostat defocussing, interruption of working fluid flow, receiver meltdown, and leakage of hazardous fluids. It is concluded that unique hazards are presented by sensible heat, latent heat, and thermochemical energy storage systems, although specific sources of danger vary widely among the three types. A tentative preference is established for the salt phase change, latent heat storage type from the standpoint of worker safety.

Routine failure events in selected solar thermal power system designs are examined, and their rates of occurrence estimated. The results are used to compare and rank the systems considered. Modules of 1 to 100 MWe are developed based on reference or other near-term designs. Technologies used include parabolic trough, parabolic dish, and central tower focusing; central and distributed power generation; and proximate and independent siting of power modules. Component counts and failure rates estimated include heat transfer system leaks, sensor failures, and mechanical and electrical component failures, such as pumps, motors, and wire and cable. Depending on the technology chosen, leak rates can approach 1000 per year per 100 MWe system capacity, while component failure rates can be several times that level. Within categories of failures, the various technologies can have rates differing by a factor of 1000 or more. A uniform weighting for the consequences of the various failure types is proposed. Under this weighting, central tower systems are most favored, followed by parabolic trough, parabolic dishes with dispersed power generation, and parabolic dishes with central power generation. This weighting does not account for possible variations in the technologies. A sensitivity analysis is used to bound the relative hazards of the various failure events required to invert one or more of the system rankings.