Commercial SSRs are expensive, bulky, and have high dissipation. MOSFETs can be used to achieve better performance and lower dissipation at lower costs and, can integrate better into a system design. This project examines the use of an isolated flyback to drive them.
Hi K.C., good points on the creepage & clearance. I chose to stay away from that area due to the complexity of the requirements and rather focus on the concept. That said, yes the design would require modifications to meet.