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Iranian researchers have studied the operation of a real solar-powered greenhouse in Alborz province and found that only 4% of the greenhouse roof needs to be covered with photovoltaic modules to meet the demand for lighting and water pumping.
A research group from Tehran University in Iran has conducted a feasibility study for the use of photovoltaic systems in commercial hydroponic greenhouses across the country.
Their work involved calculating the total energy input of a strawberry greenhouse in a case study that currently runs on natural gas and electricity, and then simulating the surface area required by a photovoltaic system to completely replace grid electricity.
“This study aims to assess the energy and environmental aspects, as well as the feasibility of using photovoltaic cells to meet the energy needs of a commercial hydroponic greenhouse in the Alborz province,” the scientists explain. “Data from a 3,000 m2 hydroponic strawberry greenhouse were collected through on-site visits, surveys and measurements.”
Alborz is located in northern Iran and has an average annual temperature of 14.1 °C and an annual rainfall of 252 mm. According to official data from 2000 to 2021, the average total daily radiation is about 10.9 MJ m2, reaching a maximum of about 29 MJ m2 in June and a minimum of about 9 MJ m2 in December.
In their calculation of energy input, the researchers included parameters such as human labour, equipment and fertilisers, along with the use of natural gas and electricity. From there, they found that, over the course of the year, the total energy input was 228,000 MJ per hectare.
“The results indicated that the highest input energy consumption corresponds to natural gas, which represents 68% of the total input energy. The percentage of electrical energy was around 20% of the energy consumed,” they noted. “The total electricity consumption in the greenhouse studied is 44,250 kWh (159,300 MJ).”
For their analysis, the academics sought to replace only grid-sourced electricity, which is used primarily for water pumping and lighting. In their simulation software, they designed a south-facing photovoltaic system installed on the greenhouse roof, with panels installed at a 35-degree tilt. The earths reflectivity coefficient was assumed to be 0.3.
“The photovoltaic system was considered connected to the grid, which has a maximum panel efficiency equal to 18% and the efficiency of the inverter and distribution cables is 96%,” the group further explained.
“The results showed that 7,736 MJ of solar energy can be received per year per square meter of panel surface. Therefore, approximately 120 m2 of panel surface is needed to generate this amount of electricity. This panel surface represents approximately 4% of the greenhouse roof surface and can supply renewable solar electricity to the greenhouse without significantly reducing the lighting level of the plants inside,” they concluded.
Calculating the impact of replacing grid-connected electricity with locally produced photovoltaic power, the group also found that it reduced the adverse environmental effects of non-renewable energy sources. The rate of damage to human health decreased by 7% and the rate of damage to the ecosystem by 15%.
Their findings were presented in “ Feasibility study of using photovoltaic cells for a commercial hydroponic greenhouse: Energy analysis and life cycle assessment, ” published in e-Prime – Advances in Electrical Engineering, Electronics and Energy . |
