group 3 is the height that is assumed by means of individual weighted averages for the height of each individual plant the average height b from the roof surface of the light receiving surface of the solar cell module is preferably greater than the average height a from the roof surface of the plant group this is in order to prevent the occurrence of shadows caused by the plant group on the light receiving surface of the solar cell module and to prevent the solar cell module from obstructing light reception further the projection distancec between the nearest plant group and the solar cell module as shown in fig1 preferably satisfies equation 1 below this is because when equation 1 above is not satisfied and equation 3 below is satisfied a shadow caused by the solar cell module is cast on the plant group and obstructs cultivation of the plant group although not shown regions where people can walk are maintained as paths during maintenance between the plant group 3 and the solar cell system 10 mutually between the plant groups 3 and mutually between the solar cell systems 10 and heat insulating material and moisture rich material and so forth.