NEXUS: Integrated Sustainable Energy for Enhancing Farm Productivity

NEXUS is developing inexpensive and efficient sustainable energy greenhouse heating technologies that provide affordable and sustainable means to improve the food-growing capacities and the standard of living for farmer communities in rural Appalachia while reducing the use of fossil fuels.
Authors: O-Y Yu1, J Ferrell1, H-Y Kim and J Houser
 
Published under licence by IOP Publishing Ltd
IOP Conference Series: Earth and Environmental Science, Volume 188, conference 1
 
Abstract
 
The NEXUS at Appalachian State University, NC, USA is a multidisciplinary team of faculty and students housed in the Department of Sustainable Technology and the Built Environment whose research lies at the intersection of agriculture, energy, and natural resources.
 
NEXUS is developing inexpensive and efficient sustainable energy greenhouse heating technologies that provide affordable and sustainable means to improve the food-growing capacities and the standard of living for farmer communities in rural Appalachia while reducing the use of fossil fuels. This is done by using on-farm biomass resources/wastes such as agricultural waste and wood chips to produce energy. Growing season extension with heated greenhouses increases the availability of local food throughout the year, expands available markets and increases farmers' profits. The 7 m by 10 m greenhouse (conventional hoop) includes an above ground 5,700-liter water storage tank and an aquaculture pond. It is supported by a small-scale pyrolysis system, an anaerobic digestion system, solar thermal, and compost heating. The heat from various heating methods is delivered and stored in the water storage tank inside the greenhouse.
 
An Arduino module controls the flow rate of water from the tank to various heat exchangers based on temperature differentials. A closed loop heat exchanger circulates heated water from the tank to the aquaculture pond to maintain an optimal temperature for tilapia growth. The pond also acts as a thermal storage, and holds/distributes heat to the greenhouse.
 
The main purpose of this study is to test the integrated sustainable energy heating system for growing season extension with less energy cost. Our preliminary result shows that compared to a conventional space heating system, about 30% of energy was saved to keep the greenhouse temperature available for growing by radiation from the water storage tank.

Photo: Inside the greenhouse, thermal battery (left) and raised aquaponics grow beds (right). (credits: O-Y Yu1, J Ferrell1, H-Y Kim and J Houser)

 
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