A floating solar steam generator, called the One-Sun Ambient Steam Generator (OAS), enables steam generation under one sun (1000 W/m²) without optical concentration. This system uses thermal concentration and heat localization to minimize heat losses, achieving 100°C steam generation with high efficiency. The OAS consists of a spectrally selective absorber, thermal insulation, and a transparent cover to reduce convective losses. It is constructed from low-cost materials and can generate steam continuously under ambient solar conditions. Laboratory experiments confirmed that the OAS can produce steam at 98°C with a thermal concentration of 1300x, and outdoor tests validated its performance under varying solar flux and wind conditions. The OAS can reach 100°C temperatures even during low and variable solar flux periods. The system's efficiency is influenced by factors such as bubble wrap transmittance, absorber surface absorptance, and emittance. The OAS is more cost-effective than optical concentration methods, with an estimated cost of $6/m², potentially reducible to $2/m². The floating structure also enables solar desalination and has potential applications in remote locations for distillation and sterilization. The study demonstrates that thermal concentration can be a more cost-effective approach for solar steam generation than optical concentration, opening new possibilities for solar thermal energy harvesting.A floating solar steam generator, called the One-Sun Ambient Steam Generator (OAS), enables steam generation under one sun (1000 W/m²) without optical concentration. This system uses thermal concentration and heat localization to minimize heat losses, achieving 100°C steam generation with high efficiency. The OAS consists of a spectrally selective absorber, thermal insulation, and a transparent cover to reduce convective losses. It is constructed from low-cost materials and can generate steam continuously under ambient solar conditions. Laboratory experiments confirmed that the OAS can produce steam at 98°C with a thermal concentration of 1300x, and outdoor tests validated its performance under varying solar flux and wind conditions. The OAS can reach 100°C temperatures even during low and variable solar flux periods. The system's efficiency is influenced by factors such as bubble wrap transmittance, absorber surface absorptance, and emittance. The OAS is more cost-effective than optical concentration methods, with an estimated cost of $6/m², potentially reducible to $2/m². The floating structure also enables solar desalination and has potential applications in remote locations for distillation and sterilization. The study demonstrates that thermal concentration can be a more cost-effective approach for solar steam generation than optical concentration, opening new possibilities for solar thermal energy harvesting.