Abstract:Harvesting solar energy as heat has many applications, such as power generation, residential water heating, desalination, distillation and wastewater treatment. However, the solar flux is diffuse, and often requires optical concentration, a costly component, to generate high temperatures needed for some of these applications. Here we demonstrate a floating solar receiver capable of generating 100°C steam under ambient air conditions without optical concentration. The high temperatures are achieved by using thermal concentration and heat localization, which reduce the convective, conductive, and radiative heat losses. This demonstration of a low-cost and scalable solar vapor generator holds the promise of significantly expanding the application domain and reducing the cost of solar thermal systems. Keywords: solar thermal, steam generation, thermal concentration, water treatmentThe sun is a promising and abundant source of renewable energy that can potentially solve many of society's challenges. Solar thermal technologies, i.e., the conversion of the sunlight to thermal energy, are being developed for many applications such as power generation, domestic water heating, desalination, and other industrial processes. [1][2][3][4][5][6][7] Steam and vapor generation is often desired in these applications, but the dilute solar flux (1000 W/m 2 ) does not provide enough power per unit area of the absorber to reach the required high temperatures and to compensate for the large latent heat of water vaporization. Optical

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Summary An observer‐based output feedback predictive control approach is proposed for linear parameter varying systems with norm‐bounded external disturbances. Sufficient and necessary robust positively invariant set conditions of the state estimation error are developed to determine the minimal ellipsoidal robust positively invariant set and observer gain through offline computation. The quadratic upper bound of state estimation error is updated and included in an ℋ∞‐type cost function of predictive control to optimize transient output feedback control performance. Recursive feasibility of the dynamic convex optimization problem is guaranteed in the proposed predictive control strategy. With the input‐to‐state stable observer, the closed‐loop control system states are steered into a bounded set. Simulation results are given to demonstrate the effectiveness of the proposed control strategy. Copyright © 2016 John Wiley & Sons, Ltd.