Researchers in Iran investigated the operation of a real solar-powered greenhouse in Alborz province and found that only 4% of the greenhouse’s roof needs to be covered with PV modules to meet the demand for lighting and water pumping comply.
A research group from Iran’s University of Tehran has conducted a feasibility study on the use of PV systems in commercial hydroponic greenhouses across the country.
Their work involved calculating the total energy input of a strawberry greenhouse in a case study currently running on natural gas and electricity, and then simulating the area required for a PV system to completely replace electricity from the grid.
“This study aims to assess the energy and environmental aspects as well as the practical feasibility of using photovoltaic cells to meet the energy needs of a commercial hydroponic greenhouse in the province of Alborz,” the scientists said. “Data was collected from a 3,000 m2 strawberry hydroponic greenhouse through site visits, surveys and measurements.”
Alborz is located in the north of Iran and has an average annual temperature of 14.1 C and an annual precipitation of 252 mm. Based on official data from 2000 to 2021, the average daily total radiation is about 10.9 MJ m2, with a high of about 29 MJ m2 in June and a low of about 9 MJ m2 in December.
In their calculation of energy input, the researchers included parameters such as human labor, equipment and fertilizers, along with natural gas and electricity consumption. Based on this, they found that the total energy input for the entire year was 228,000 MJ per hectare.
“The results indicated that input energy consumption is highest for natural gas, which accounts for 68% of total input energy. The electricity energy percentage was approximately 20% of the energy consumed,” they said. “The total electricity consumption in the greenhouse examined is 44,250 kWh (159,300 MJ).”
For their analysis, the academics sought to replace only electricity from the grid, which is mainly used for pumping water and lighting. In their software simulation, they designed a south-facing PV system, installed on the greenhouse roof, with panels installed at a 35-degree slope. The Earth’s reflectivity coefficient was assumed to be 0.3.
“The photovoltaic system was assumed to be grid connected, which has a maximum panel efficiency of 18% and the inverter and distribution cables efficiency is 96%,” the group further explained.
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“The results showed that 7,736 MJ of solar energy can be received annually per square meter of panel surface. To generate this amount of electricity, approximately 120 m2 of panel surface is required. This panel area covers roughly 4% of the greenhouse roof area and can provide renewable solar energy to the greenhouse without significantly reducing the lighting level for the plants within,” they found.
When calculating the impact of replacing grid-connected electricity with locally produced PV power, the group also found that this reduced the negative environmental impacts of non-renewable energy sources. They found that damage to the human health index decreased by 7% and damage to the ecosystem index decreased 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 on e-Prime – Advances in electrical engineering, electronics and energy.
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