Abstract
Particle-based power tower systems are a promising technology that can allow operation of concentrating solar power (CSP) systems at temperatures higher than what today's commercial molten salt systems can achieve, making them suitable for use in a variety of applications, including supercritical CO2 cycles, air Brayton cycles, and high temperature process heat. In this concept, particles, instead of molten salt, are heated by the concentrated sunlight. In 2015, this concept was successfully tested at Sandia National Laboratories. In the mean time, an integrated system incorporating a particle heating receiver, a particle-to-air heat exchanger and a 100-kWe microturbine was designed, built, and tested at King Saud University in Riyadh, Saudi Arabia. The integrated system was run in 2018, and results from that test campaign were very promising, with temperatures of the particles leaving the receiver exceeding 600 degrees C despite a number of challenges. The utility sponsoring the project is now planning to move forward with building a 1-MWe plant using the same concept, thereby moving closer to large-scale deployment, and making this facility the world's first commercial concentrating solar power plant that uses the particle heating receiver concept. Moving from a 100-kWe scale to a 1-MWe scale requires modifications to the design of some components. The most likely plant location is the city of Duba in northwestern Saudi Arabia where the average daily total DNI is 7,170 Wh/m(2) and an integrated solar combined cycle power plant exists on the premises. This paper discusses the design features of the main components of the new plant. Those features include a north field design, a 7.22-m(2) single-sheet heliostat design, a cavity receiver to improve receiver efficiency by reducing radiative and convective losses, temperature-based particle flow regulation within the receiver, six hours of full-load thermal energy storage, with the tanks integrated into the tower structure and made of cost-effective masonry material, a shell-and-tube particle-to-air heat exchanger, a 45% efficiency recuperated intercooled gas turbine, and a high-temperature bucket elevator. The heliostat field was optimized using SolarPILOT. Results show that 1,302 heliostats are needed. The aperture area was found to be approximately 5.7 m(2), while the total illuminated receiver surface area is about 16.8 m(2). This design was found to be capable of achieving the particle temperature rise of 416 degrees C, which is necessary to allow the turbine to rely entirely on the solar field to bring the temperature of air to the firing temperature of the turbine, thereby eliminating the need for fuel consumption except for back-up and for assistance at off-design conditions.