Greenhouse tomato production with electricity generation by roof-mounted flexible solar panels

Abstract

The integration of renewable energy sources into greenhouse crop production in southeastern Spain could provide extra income for growers. Wind energy could be captured by small to medium-sized wind turbines, gas could be produced from biomass, and solar energy could be gathered by solar panels. The aim of this study was to examine the effect of flexible solar panels, mounted on top of a greenhouse for electricity production, on yield and fruit quality of tomatoes (Solanum lycopersycum L., cv Daniela). This study was undertaken in a commercial raspa y amagado greenhouse, typical of the Almería region (Spain). Tomato plantlets were planted at a density of 0.75 plants m −2 . The flexible solar panels were mounted on two parts of the roof in different arrangements (T1 and T2), each blacking out 9.8 % of its surface area. A control area (T0 arrangement) was fitted with no panels. No difference was found in terms of total or marketable production under these three arrangements, although fruit mean mass and maximum diameter of T0 were significantly greater than T1 and T2. Fruit in T0 matured earlier with more intense color compared with those in T1 and T2. However, these differences had no effect on price as the tomatoes produced under three conditions fell into the same commercial class (G class; diameter 67-81 mm). Solar panels covering 9.8 % roof area of the greenhouse did not affect yield and price of tomatoes despite of their negative effect on fruit size and color.

Growth and Physiological Characteristics of Lettuce (Lactuca sativa L.) and Rocket (Eruca sativa Mill.) Plants Cultivated under Photovoltaic Panels

“…The particular configuration of the PV panels was selected in order to achieve a shading "moving" mode during the day and consequently to minimize the possible permanent shading for some plants in East-West orientation greenhouses (Trypanagnostopoulos et al, 2017). Considering that it has been proposed a maximum of 25% PV shading, in order to achieve the optimal balance between shade reduction and energy production (Buttaro et al, 2016), the coverage percentage of the experiment is similar with other studies which applicate 9.8-12.9% greenhouse PV coverage (Kadowaki et al, 2012;Ureña-Sánchez et al, 2012).…”

“…Except for lettuce which has been discussed before, studies have been conducted on Welsh onion, tomato, wild rocket, basil and zucchini (Kadowaki et al, 2012;Ureña-Sánchez et al, 2012;Minuto et al, 2009;Cossu et al, 2014;Buttaro et al, 2016). Although the inherent characteristics of different species or varieties of the same species may play a role for the plant growth response against shading (Marrou et al, 2013), the PV induced shading effect on plants' growth characteristics and crop productivity seems to depend on several other factors, too.…”

“…Finally, we have to take into account that for some plants the PV induced shading may affect their growth characteristics (some of them with commercial interest), just as leaf development, fruit size or color, without affecting their yield (Minuto et al, 2009;Ureña-Sánchez et al, 2012). Moreover, it has also been reported that the PV shading effect may favor the development of fungal diseases (Minuto et al, 2009) a phenomenon which may be associated with possible changes of the greenhouse environmental conditions caused by the shading as the decrement of the temperature or the increment of the relative humidity, as we observed during our experiment (Table 2).…”

“…The fertilization of the chosen crop was based on soil analysis prior to the installation plant biomass (roots, stems, leaves) as well as the photosynthetic rate, the transpiration and the stomatal conductance are decreased under low solar radiation, while on the other hand the plant height is increased (De Salvador et al, 2008;An and Shangguan, 2009;Wang et al, 2009;Zervoudakis et al, 2012). The shading by straight-line arranged PV panels on the greenhouse roof has been reported to decrease the plant growth and consequently the crop yield while the checkerboard arrangement may diminish the above inhibitory effect (Kadowaki et al, 2012;Ureña-Sánchez et al, 2012). On the other hand, it seems that the solar intensity demand for maximum plant growth differs between species considering that it has been reported that intermediate solar radiation conditions (about 50% of full ambient light) were more adequate for some species to reach higher levels of biomass productivity (de Carvalho Gonçalves et al, 2005).…”

Analysis of the internal shading in a photovoltaic greenhouse tunnel

“…The spatial distribution of the shades is an important parameter for choosing the best combination of PV panels and crops (AlShamiry et al, 2007;Dupraz et al, 2011;Lopez-Marin et al, 2012;Urena-Sanchez et al, 2012).…”