Project Overview
Commodities
Practices
Proposal abstract:
Title: Utilizing Shallow Geothermal Resources for Low-Cost Season Extension of Controlled Environmental Agriculture: Performance Evaluation and Design Tool Development
Context: Season extension using high tunnels is a formidable tool for growers, allowing them to grow, harvest, and sell produce during an extended time period at a higher price point, providing economic sustainability. Unfortunately, heating and cooling high tunnels can be energy-intensive and costly, so finding lower-energy alternatives could offer financial benefits to farmers and decrease their reliance on fossil fuels. Just 1-2 m underground, the soil is cooler than ambient air in the summer, and warmer from fall through spring. An earth-to-air heat exchange (EAHX) system utilizes these shallow geothermal resources as air pulled through the system will gain heat from or lose heat to the soil, depending on the season. My previous project has shown EAHX systems can be installed on-farm for a low cost (comparable to a propane heater) and provide supplemental heating and cooling. It is desirable to investigate the heating and cooling provided by a standalone EAHX system compared to a passive high tunnel, and to apply these findings into an extension-ready tool for more farmers to adopt sustainable season extension infrastructure.
Approach: An on-farm research study will be performed comparing the growing conditions of two side-by-side high tunnels - one which only uses passive ventilation fans and roll-up sides, and another additionally outfitted with an EAHX system. Local weather conditions, soil temperatures alongside the EAHX, and air temperature and relative humidity in both high tunnels will be monitored. Additional soil temperature monitoring will investigate the seasonal temperature changes under different land covers that are relevant to high tunnels in urban agricultural applications.
Outcomes: Through this project, an on-farm shallow geothermal EAHX system will be installed and demonstrated through field days and conferences. Additionally, a user-friendly design tool will be developed to show the thermal and cooling capabilities and costs of EAHX systems based on the comparison of a passive and EAHX-aided high tunnel and the seasonal soil temperatures under urban landcovers adjacent to high tunnels. These findings and training in the decision-making tool will be disseminated through OSU Extension and farmer’s organizations. Research outcomes will also be disseminated through publication of fact sheets and journal articles.
Evaluation: Post-impact assessments will be collected during field days, conference presentations, and design tool workshops. Additional follow-up of workshop attendees will investigate if any farmers have adopted this technology.
Project objectives from proposal:
Learning outcomes: Farmers will learn about a sustainable tool for low-energy season extension. They will be able to use a decision-making tool to estimate economic and environmental costs and benefits of different heating and cooling techniques for high tunnels. Through workshops, conference presentations, and field days, farmers will learn the principles of how shallow geothermal resources can be used to provide seasonal heating and cooling. The background research into seasonal soil temperatures under different land covers will ensure wider applicability to different configurations of EAHX systems in urban and rural high tunnels.
Action outcomes: Equipped with a greater understanding of EAHX systems and their costs and benefits, farmers will adopt a low-energy season extension infrastructure as a supplementary or stand-alone heating and cooling system. This will in turn increase their profits and reduce their energy costs and reliance on fossil fuels or inefficient passive high tunnels. These outcomes will be assessed through post-impact surveys and six-month follow-up surveys of all farmers participating in design tool workshops, field days, and conference presentations.