Electronic Spreadsheet Tools for Layout Design of Greenhouses M. Eben-Chaime 1 , A. Bechar 1,2 and A. Baron 1 1 Department of Industrial Engineering & Management, Ben-Gurion University P.O. Box 653, 84105 Be'er Sheva, Israel 2 The Institute of Agricultural Engineering, ARO, Bet Dagan, Israel Keywords: greenhouses, protected horticulture, layout design, structure, configuration Abstract As noted by one author, "Far to often, the grower finds himself locked into an inefficient operation if he has not spent some time to arrange structures properly," but "explanation of suitable layouts is difficult to find in the horticulture literature." In response to this need, tools have been developed for layout design purposes and are presented herein. These tools evaluate the annual operational profit associated with a specific layout – yield and sales income less operational cost and return of investment in infrastructure. Alternative layouts can be evaluated and the most profitable is selected. The tools have been designed to be highly accessible, and to this end they are implemented with any spreadsheet software and any computer. Further, the design of the tools facilitates WHAT-IF analyses via the changing of parameter values. The applicability of design tools is demonstrated via numerical analyses of the layout design of a 1-hectare greenhouse for pepper growing using the Holland method. Evidently, the layout design can have significant effect on the economical efficiency of the greenhouse – annual profit increases by, at least 12%, and up to 40%! INTRODUCTION "Greenhouse production remains the most intensive agricultural process known. It is intensive in terms of labor. It is intensive in terms of capital since the erection of a covering over ground is a large investment" (Hanan, 1998). This statement underlines not only the problem associated with greenhouses but also the major contributors to its existence. A major advantage of greenhouses over open area is higher area utilization – higher yield per area unit. Greenhouse design literature over the past 3 decades aimed at increasing the yield of individual plants by optimizing climatic conditions: radiation, temperature, moisture and gas (e.g., air, CO 2 ) distribution and flows in the greenhouse space (e.g., Weihong et al., 2005; Shklayr and Arbel, 2004; Gupta and Chandra, 2002; Ali and El-mansy, 1990). To this end, the effect of orientation, height, roof-shape, shape, size and distribution of air openings, etc., have been studied and optimal value combinations have been sought. These are general factors, which are more relevant to greenhouse constructors and suppliers. The growth in area utilization, however, has a price – it requires a proper and costly infrastructure and maintenance – "the erection of a covering over ground is a large investment". Thus, area utilization should be maximized by reducing unused area – pathways, etc. to minimum. On the other hand there is labor. In an early survey during the mid 1970's, growers attributed approximately 25 % of plant production costs to labor (Aldrich and Bartok, 1992). Nelson (1991, page 574) estimate labor contribution to the total costs at 34.81 %, and includes 5.58 % depreciation and 2.5 % interest among other contributors. Unlike labor, the later two are not "operational costs" and when excluded, labor contribution to the operational cost rises to 38%. Greenhouse operational costs of various types of crops and in different places on the globe are listed in Table 1-5 of Hanan (1998, page 6). Despite all differences and the large variability in absolute magnitudes, labor contributes about 40% of the operation cost, in all cases! Moreover, in all these references, labor is the largest single cost contributor. This can be attributed to the unique nature of horticulture. Horticultural crops, including greenhouses, are 'production systems' whose products – fruits and/or flowers, have two unique characteristics. First, they are highly 433