The output power produced by high-concentration solar thermal and photovoltaic systems is directly related to the amount of solar energy acquired by the system, and it is therefore necessary to track the sun's position with a high degree of accuracy. Many systems have been proposed to facilitate this task over the past 20 years. Accordingly, this paper commences by providing a high level overview of the sun tracking system field and then describes some of the more significant proposals for closed-loop and open-loop types of sun tracking systems.

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This study investigates indoor air environment via the flow fields, temperature fields and air contaminants (carbon monoxide) distributions in conventional residential kitchens, and looks for effective methods to solve those problems through natural ventilation techniques. Numerical simulations of the physical problem under consideration have been performed via a finite volume method for solving the governing equations and boundary cond itions. It is obvious that location of accumulation of air contaminants is highly relevant to the location of gas fires, and realizing the dominant flow pattern will be successful in eliminating air contaminants. An architectural design alternative, utilizing transoms, is then proposed to improve indoor air environment in kitchens.

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