In wide-area wireless access systems such as satellite communications systems and stratospheric platform systems, electric power supply for radio communications is realized by using solar photovoltaic cells and/or fuel cells. Hence, not only frequency band but also electric power is a limited and crucial radio resources for those systems. Although radio channel allocation algorithms taking account of the frequency constraint only or the power constraint only have been proposed, radio channel allocation algorithms taking account of the both constraints simultaneously have not been studied enough so far. This paper proposes a radio channel allocation algorithm utilizing the linear programming method to address this issue. The proposed algorithm firstly allocates radio channels in proportion to the traffic demand distributed over the area and then maximizes the total radio channels allocated to systems. Some numerical results are given for a stratospheric platform system that covers a part of Japanese land, for example, in order to demonstrate the effectiveness of this algorithm.