Greenhouse vegetable production plays a vital role in providing year‐round fresh vegetables to global markets, achieving higher yields, and using less water than open‐field systems, but at the expense of increased energy demand. This study examines the life cycle environmental and economic impacts of integrating semitransparent organic photovoltaics (OPVs) into greenhouse designs. We employ life cycle assessment to analyze six environmental impacts associated with producing greenhouse‐grown tomatoes in a Solar PoweRed INtegrated Greenhouse (SPRING) compared to conventional greenhouses with and without an adjacent solar photovoltaic array, across three distinct locations. The SPRING design produces significant reductions in environmental impacts, particularly in regions with high solar insolation and electricity‐intensive energy demands. For example, in Arizona, global warming potential values for a conventional, adjacent PV and SPRING greenhouse are found to be 3.71, 2.38, and 2.36 kg CO2eq/kg tomato, respectively. Compared to a conventional greenhouse, the SPRING design may increase life cycle environmental burdens in colder regions because the shading effect of OPV increases heating demands. Our analysis shows that SPRING designs must maintain crop yields at levels similar to conventional greenhouses in order to be economically competitive. Assuming consistent crop yields, uncertainty analysis shows average net present cost of production across Arizona to be $3.43, $3.38, and $3.64 per kg of tomato for the conventional, adjacent PV and SPRING system, respectively.
Organic solar powered greenhouse performance optimization and global economic opportunity
Greenhouses conserve land and water while increasing crop production, making them an attractive system for low environmental impact agriculture. Yet, to achieve this goal, there is a need to reduce their large energy demand. Employing semitransparent organic solar cells (OSCs) on greenhouse structures provide an opportunity to offset the greenhouse energy needs while maintaining the lighting needs of the plants. However, the design trade-off involved in optimizing solar power generation and crop productivity to maximize greenhouse economic value is yet to be studied in detail. Here, a functional plant growth model is integrated with a dynamic energy model that includes supplemental lighting to optimize the economics of growing lettuce and tomato. The greenhouse optimization considers 64 different OSC active layers with varying roof coverage for 25 distinct climates providing a global perspective. We find that crop yield is the primary economic driver, and that crop yield can be maintained in OSC-greenhouses across diverse climates. The crop productivity along with the energy produced by the OSCs results in improved net present value of the OSC-greenhouses relative to conventional systems in most climates for both lettuce and tomato. In addition, we find common solar cell active layers that maximize greenhouse economic value resulting in guidelines for scaling up OSC-greenhouse design. Through this model framework, we highlight the opportunity for OSCs in greenhouses, uncover designs and locations that provide the most value, and provide a basis for further development of OSC-greenhouses to achieve a sustainable means of food production.
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- Award ID(s):
- 1639429
- NSF-PAR ID:
- 10380060
- Date Published:
- Journal Name:
- Energy & Environmental Science
- Volume:
- 15
- Issue:
- 4
- ISSN:
- 1754-5692
- Page Range / eLocation ID:
- 1659 to 1671
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract -
Recognizing the growing interest in the application of organic photovoltaics (OPVs) with greenhouse crop production systems, in this study we used flexible, roll-to-roll printed, semitransparent OPV arrays as a roof shade for a greenhouse hydroponic tomato production system during a spring and summer production season in the arid southwestern U.S. The wavelength-selective OPV arrays were installed in a contiguous area on a section of the greenhouse roof, decreasing the transmittance of all solar radiation wavelengths and photosynthetically active radiation (PAR) wavelengths (400–700 nm) to the OPV-shaded area by approximately 40% and 37%, respectively. Microclimate conditions and tomato crop growth and yield parameters were measured in both the OPV-shaded (‘OPV’) and non-OPV-shaded (‘Control’) sections of the greenhouse. The OPV shade stabilized the canopy temperature during midday periods with the highest solar radiation intensities, performing the function of a conventional shading method. Although delayed fruit development and ripening in the OPV section resulted in lower total yields compared to the Control section (24.6 kg m−2 and 27.7 kg m−2, respectively), after the fourth (of 10 total) harvests, the average weekly yield, fruit number, and fruit mass were not significantly different between the treatment (OPV-shaded) and control group. Light use efficiency (LUE), defined as the ratio of total fruit yield to accumulated PAR received by the plant canopy, was nearly twice as high as the Control section, with 21.4 g of fruit per mole of PAR for plants in the OPV-covered section compared to 10.1 g in the Control section. Overall, this study demonstrated that the use of semi-transparent OPVs as a seasonal shade element for greenhouse production in a high-light region is feasible. However, a higher transmission of PAR and greater OPV device efficiency and durability could make OPV shades more economically viable, providing a desirable solution for co-located greenhouse crop production and renewable energy generation in hot and high-light intensity regions.more » « less
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Abstract Greenhouses provide a controlled environment for plant growth, which increases crop yields, reduces the use of water and fertilizers, and offers resilience to droughts and extreme weather. However, greenhouse operation is energy intensive due to their heating and cooling loads. Luminescent solar concentrators (LSCs) are promising for semitransparent greenhouse roofs that produce clean electricity, thus reducing the greenhouse energy demand, while also transmitting enough light to satisfy plant growth. Herein, we model the performance of LSC roofs designed as glass panels coated with quantum dot (QD)/polymer nanocomposite films and front‐facing surface‐mounted photovolatic cells. Five widely studied QD materials are examined to demonstrate that the proposed QD LSC roofs can have effective power conversion efficiencies exceeding 10% while also increasing the red‐light fraction, which is beneficial for plant growth. The effect of LSC integration on the greenhouse thermal energy demands is studied for the example of silicon (Si) QD LSC roofs. In warm climates, solar power generated by the Si QD LSC roofs satisfies the entire greenhouse energy demand and thus enables net‐zero energy operation. Overall, the results of the current research demonstrate the strong potential of integrating QD LSCs into greenhouses to reduce energy costs and enhance plant growth.
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Lighting is a major component of energy consumption in controlled environment agriculture (CEA) operations. Skyscraper farms (multilevel production in buildings with transparent glazing) have been proposed as alternatives to greenhouse or plant factories (opaque warehouses) to increase space-use efficiency while accessing some natural light. However, there are no previous models on natural light availability and distribution in skyscraper farms. This study employed climate-based daylight modeling software and the Typical Meteorological Year (TMY) dataset to investigate the effects of building geometry and context shading on the availability and spatial distribution of natural light in skyscraper farms in Los Angeles (LA) and New York City (NYC). Electric energy consumption for supplemental lighting in 20-storey skyscraper farms to reach a daily light integral target was calculated using simulation results. Natural lighting in our baseline skyscraper farms without surrounding buildings provides 13% and 15% of the light required to meet a target of 17 mol·m−2·day−1. More elongated buildings may meet up to 27% of the lighting requirements with natural light. However, shading from surrounding buildings can reduce available natural light considerably; in the worst case, natural light only supplies 5% of the lighting requirements. Overall, skyscraper farms require between 4 to 11 times more input for lighting than greenhouses per crop canopy area in the same location. We conclude that the accessibility of natural light in skyscraper farms in dense urban settings provides little advantage over plant factories.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d1ee03474j
