FIELD AND SPACE ROBOTICS LABORATORY
Prof. Steven Dubowsky
Prof. Richard Wiesman
Elizabeth Anne Reed
The supply of energy and clean water to remote locations, such as desert facilities, farming operations, resorts, and small villages in the developing world can be logistically complex and expensive. This project explores the feasibility, design and control of small smart power units to provide clean water and energy to remote sites by using solar power and reverse osmosis modules, such as those shown conceptually in the Figure 1.
Figure 1: A simple mobile solar powered reverse osmosis system
This work focuses on four main areas to make solar energy practical for these relatively small-scale applications: modular design methodologies, smart control, and the design of robust and low cost solar collectors and concentrators for challenging environments as described below.
Small-scale photovoltaic and reverse osmosis systems need to be designed, and fabricated to meet the specific demands of an application and its location. Unfortunately, the manufacturing of a custom design system is expensive and requires significant expertise. Also, with the decreasing cost of basic elements, the cost of system design and assembly is becoming increasingly significant. Systems will need to be assembled from inventories of standard components and subsystems that can be cost-effectively mass-produced. For a given inventory of available modules there are a very large number of possible combinations to be considered. In addition, the stochastic nature power available from the sun and the water demand make the optimal sizing of such a system difficult. The analysis required to best configure a system would be beyond the expertise that is likely to found in many parts of the developing world. Developing design rules, algorithms and software to optimally configure these systems is a major component of this research.
Figure 2: Conceptual Diagram of Experimental System First Stage.
Photovoltaic and reverse osmosis systems will need to controlled so that the full system performance is optimal. These systems will need to be controlled when there are stochastic inputs such as changing solar insolation or system demand. For cases when external energy storage devices are eliminated from the system, the optimal control problem becomes even more complex. Smart control algorithms and electronics are currently being developed to optimize the performance of a photovoltaic powered reverse osmosis system without energy storage elements.
Robust and Low Cost Solar Collectors and Concentrators
With the currently available technology, the costs of custom solar collectors and concentrators can be excessive. Also, the current collector and concentrator technologies degrade in challenging environments, requiring substantial maintenance. New solar collector design concepts and manufacturing technologies can potentially significantly reduce the total lifetime cost of these devices. Approaches being considered include: modular design techniques, new materials to improve system life in challenging environments, adaptive structures and intelligent controls to enhance performance.
In support of the program research, a small-scale photovoltaic powered reverse osmosis unit is being designed and built. This system will be fully instrumented and will be intelligently controlled. This test bed will be used to demonstrate the advantages of optimally designing and controlling a solar-powered system and allow for validation of analytical models. The initial stages of this system are currently being constructed and tested in the laboratory. A conceptual diagram of the final experimental system is shown in Figure 2.
A sequence of time-lapse photos of the system operating on a partly cloudy day in Boston
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