Sustainable Protected Cropping: A Case Study of Seasonal Impacts on Greenhouse Energy Consumption during Capsicum Production

Abstract

Sustainable food production in protected cropping is increasing rapidly in response to global climate change and population growth. However, there are significant knowledge gaps regarding energy consumption while achieving optimum environmental conditions for greenhouse crop production. A capsicum crop cultivated in a high-tech greenhouse facility in Australia was analysed in terms of relationships between key environmental variables and the comparative analysis of energy consumption during different seasons. We showed that daily energy consumption varied due to the seasonal nature of the external environment and maintenance of optimal growing temperatures. Total power consumption reported throughout the entire crop cycle for heating (gas hot water system) and cooling (pad and fan) was 12,503 and 5183 kWh, respectively; hence, heating consumed ca. 70% of the total energy requirement over the 8-month growing period (early spring to late autumn) in the greenhouse facility. Regressions of daily energy consumption within each season, designated either predominantly for heating or cooling, indicated that energy consumption was 14.62 kWh per 1 °C heating and 2.23 kWh per 1 °C cooling. Therefore, changing the planting date to late spring is likely to significantly reduce heating energy costs for greenhouse capsicum growers in Australia. The findings will provide useful guidelines to maximise the greenhouse production of capsicum with better economic return by taking into consideration the potential optimal energy saving strategy during different external environment conditions and seasons.

Energy Minimisation in a Protected Cropping Facility Using Multi-Temperature Acquisition Points and Control of Ventilation Settings

“…Since cooling, energy consumption in a comparable compartment within the same protected facility is around 2.23 kWh per 1 • C cooling [23], the potential saving of cooling energy consumption could be significant. Furthermore, significant cost savings can be achieved over a crop cycle of nine months in a large greenhouse under warmer conditions.…”

“…Daily and average energy consumption across four combinations are compared as a basis for developing an optimal cooling strategy for energy management. An optimal cooling strategy for energy management using multi-temperature acquisition points for opening/closing of vents and shade screens could be used to extend the overall energy consumption profile of the selected protected cropping facility [16,23]. These studies form the basis for setting the opening or closing of vents, using the most reliable temperature measurements within the facility, to reduce energy costs during 6-9 months of cropping cycles.…”

“…For example, ref. [23] reported energy consumption of protected cropping of the capsicum production cycle and indicated the cycle of 247 days with a broader temperature range outside the facility, including a maximum temperature difference of 21.3 • C between the internal and outside temperature.…”

“…When this saving of 2 kWh per 1 • C cooling is considered from the perspective of an overall temperature profile of the compartment and outside temperature, it is significant since the temperature difference between gutter level and outside during day time (08:00 to 16:00) is significant (Tables A2 and A3). This saving of 2 kWh per 1 • C cooling will lead to a significant amount of energy savings over many fully enclosed greenhouse vegetable crops subject to (i) warmer outside weather conditions and (ii) greenhouse crops with longer crop cycles such as 277 days of capsicum crop [23]. Therefore, total savings of cooling energy consumption should be evaluated, based on savings of each day of the entire crop cycle, taking into consideration of temperature profile of the facility and the outside temperature during the whole crop cycle.…”

Smart glass impacts stomatal sensitivity of greenhouse Capsicum through altered light

“…These include the even-span greenhouse designed for crop cultivation at high latitude (Sethi, 2009), optimal orientation allowing plants to receive more radiation (Xu et al, 2015), different greenhouse shapes to improve the ventilation (Katsoulas et al, 2006), and building materials utilising a special plastic film to block UV radiation and enhance light diffusion (Hemming et al, 2004). Other techniques such as vent, fog, fan cooling systems, dehumidification, and regeneration process of liquid desiccant also improve glasshouse climatic control (Lefers et al, 2016;Rabbi et al, 2019;Samaranayake et al, 2020;White, 2014). However, the high cost of these solutions indicates that an innovative alternative technique of using low emissivity 'smart glass' film, should significantly reduce the costs while maintaining adequate climate control in glasshouses (Lin et al, 2020).…”