물-에너지-식량 넥서스 분석을 위한 시설재배지의 기준작물증발산량과 난방 에너지 부하 관계 분석

Relationship Analysis of Reference Evapotranspiration and Heating Load for Water-Energy-Food Nexus in Greenhouse

Abstract

Increasing crop production with the same amount of resources is essential for enhancing the economy in agriculture. The first prerequisite is to understand relationships between the resources. The concept of WEF (Water-Energy-Food) nexus analysis was first introduced in 2011, which helps to interpret inter-linkages among the resources and stakeholders. The objective of this study was to analyze energy-water nexus in greenhouse cultivation by estimating reference evapotranspiration and heating load. For the estimation, this study used the physical model to simulate the inside temperature of the agricultural greenhouse using heating, solar radiation, ventilated and transferred heat losses as input variables. For estimating reference evapotranspiration and heating load, Penman-Monteith equation and seasonal heating load equation with HDH (Heating Degree-Hour) was applied. For calibration and validation of simulated inside temperature, used were hourly data observed from 2011 to 2012 in multi-span greenhouse. Results of the simulation were evaluated using $R^2$, MAE and RMSE, which showed 0.75, 2.22, 3.08 for calibration and 0.71, 2.39, 3.35 for validation respectively. When minimum setting temperature was $12^{\circ}C$ from 2013 to 2017, mean values of evapotranspiration and heating load were 687 mm/year and 2,147 GJ/year. For $18^{\circ}C$, Mean values of evapotranspiration and heating load were 707 mm/year and 5,616 GJ/year. From the estimation, the relationship between water and heat energy was estimated as 1.0~2.6 GJ/ton. Though additional calibrations with different types of greenhouses are necessary, the results of this study imply that they are applicable when evaluating resource relationship in the greenhouse cultivation complex.

Fig. 1 Diagram of the energy-water-food nexus in greenhouse cultivation

Fig. 2 Location map of experimental site and weather stations (Hong et al., 2013)

Fig. 3 Scatter plots of the observed and simulated temperature for calibration in 2011

Fig. 4 Scatter plots of the observed and simulated temperature for validation in 2012

Fig. 5 Comparison of observed and simulated inside temperature for model calibration in 2011

Fig. 6 Comparison of observed and simulated inside temperature for model validation in 2012

Fig. 7 Sum of reference evapotranspiration and seasonal heat load from 2013 to 2017 depending on the minimum temperature settings (12, 14, 16, 18℃)

Fig. 8 Comparison of yearly reference evapotranspiration on different temperature settings

Fig. 9 Comparison of yearly seasonal heat load on different temperature settings

Table 1 Comparison of parameter specifications between van Henten (1994) and this study

Table 2 Adjust coefficient (kc) depending on the duration of sunshine

Table 3 Specification of the greenhouse and AWS in the experimental site

Table 4 Evaluation results of temperature simulation model calibration (2011) and validation (2012)

Table 5 Yearly reference evapotranspiration (mm/year) and increment rate on different temperature settings

Table 6 Yearly seasonal heat load (GJ/year) and increment rate on different temperature settings

Table 7 Average resource demands and resource relationship on different setting temperatures