A SOLAR-POWERED DIRECT STEAM GENERATION BOILER FOR AN EDUCATIONAL DESKTOP RANKINE CYCLE

This paper presents the design and hardware validation of a unique solar powered boiler for powering a desktop scale steam Rankine power cycle. The primary purpose of the desktop Rankine cycle is to improve engineering education through a hands-on laboratory learning approach. Within this context, we have designed and validated a novel, glass-enclosed boiling chamber that generates steam entirely from the sun. Using a solar concentrator, the sun's heat is focused onto an absorber plate that acts as a heating element. The absorber plate receives solar power via radiation and heats the working fluid through convection. Since this is a direct steam generation boiler, the entering fluid is water that stratifies upon boiling into two steady-state flow regions with both liquid and gaseous phases. A thermal model is developed to characterize the concentrated solar power (CSP), chamber geometry, and heat transfer to the working fluid. A complete solar-to-steam efficiency analysis is presented and validated with the hardware. The boiler's estimated efficiency is 27.7% for converting typical daily solar irradiance to steam. The solar water boiling process can clearly be observed and is an excellent educational tool for both concentrated solar power as well as Rankine cycle power systems.