Collaborative Design of Photovoltaic-Powered Ventilation for Deep Winter Greenhouses in the North Central Region Using Computational Fluid Dynamics

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Collaborative Design of Photovoltaic-Powered Ventilation for Deep Winter Greenhouses in the North Central Region Using Computational Fluid Dynamics (CFD)

Deep Winter Greenhouses (DWGs), developed by the University of Minnesota, are structures designed to extend the growing season in cold regions. Their design incorporates an angled south-facing glazing wall that collects sunlight and a subsurface rock bed that stores heat during the day and releases it at night. This design supports continuous winter crop production while minimizing reliance on conventional heating sources.

Deep Winter Greenhouses (DWGs) are gaining popularity in Minnesota due to their sustainable design, which not only supports winter crop production but also attracts agrotourism by engaging visitors interested in local food systems and year-round farming practices. However, the south-facing wall causes excessive heat buildup in the summer, which limits the usability of DWGs for growing warm-season crops.

This study aims to develop and evaluate a photovoltaic (PV)-powered ventilation system as a sustainable solution for managing temperatures in DWGs throughout the year, with a focus on three NC states: Minnesota, Wisconsin, and Illinois. In this study, computational fluid dynamics (CFD) simulations will be used to assess airflow and temperature distributions under both winter and summer conditions. The simulations will be validated using a full-scale DWG located in Lake City, Minnesota. The System Advisor Model (SAM) will be applied to estimate heat generation and assess the economic feasibility of integrating PV-powered ventilation by calculating monthly heat generation, levelized cost of heat, net present value, and payback period.

The project will be conducted in collaboration with a DWG owner who has expressed a willingness to adopt the design developed during the course of the study. Educational materials, including fact sheets, webinars, and podcasts, will be developed and distributed through Extension networks in Minnesota, Wisconsin, and Illinois to facilitate broader adoption.

As a result of this study, growers will gain knowledge of DWGs, seasonal crop strategies, and PV-powered ventilation. At least one, and potentially up to five, growers will adopt the PV-powered ventilation system. The project will support the expanded adoption of DWGs in Wisconsin and Illinois (two neighboring states to Minnesota) through Extension and outreach efforts. In the long term, the project will support local food production systems and reduce heat in greenhouse operations. Outcomes will be evaluated through surveys, grower engagement, and web analytics.

This project targets Deep Winter Greenhouse (DWG) owners in the North Central (NC) region.

Learning Outcomes:

• Growers will gain practical knowledge of how PV-powered ventilation systems can regulate temperatures in DWGs throughout the year.

• Guidelines will be provided on fan sizing, placement, and PV modules and inverters in Minnesota, Wisconsin, and Illinois.

• Participants will also gain practical insights into crop selection based on seasonal variations.

Action Outcomes:

• At least one grower, and likely up to five, will install PV-powered ventilation systems based on the project's design recommendations.

• The project will increase the number of growers using DWGs year-round, reducing seasonal downtime and improving return on infrastructure investment.

• While DWGs are well established in Minnesota, this study will support their expanded promotion and adoption in Wisconsin and Illinois.

• Through Extension networks, recommendations are expected to reach more than 100 additional growers across Minnesota, Wisconsin, and Illinois within one year of project completion.

Broader Impact:

• Long-term outcomes include improved regional food resilience and greater interest in renewable technologies for controlled-environment agriculture.

All these outcomes will be assessed through pre- and post-surveys, on-site discussions, and evaluations conducted at Extension and outreach events (e.g., webinars).