Energy saving and solar electricity in fan-ventilated greenhouses

Philip A. Davies, Abul K. Hossain, George Lychnos, Carol Paton

Research output: Chapter in Book/Report/Conference proceedingConference publication

Abstract

Greenhouse cultivation is an energy intensive process therefore it is worthwhile to introduce energy saving measures and alternative energy sources. Here we show that there is scope for energy saving in fan ventilated greenhouses. Measurements of electricity usage as a function of fan speed have been performed for two models of 1.25 m diameter greenhouse fans and compared to theoretical values. Reducing the speed can cut the energy usage per volume of air moved by more than 70%. To minimize the capital cost of low-speed operation, a cooled greenhouse has been built in which the fan speed responds to sunlight such that full speed is reached only around noon. The energy saving is about 40% compared to constant speed operation. Direct operation of fans from solar-photovoltaic modules is also viable as shown from experiments with a fan driven by a brushless DC motor. On comparing the Net Present Value costs of the different systems over a 10 year amortization period (with and without a carbon tax to represent environmental costs) we find that sunlight-controlled system saves money under all assumptions about taxation and discount rates. The solar-powered system, however, is only profitable for very low discount rates, due to the high initial capital costs. Nonetheless this system could be of interest for its reliability in developing countries where mains electricity is intermittent. We recommend that greenhouse fan manufacturers improve the availability of energy-saving designs such as those described here.
Original languageEnglish
Title of host publicationInternational Workshop on Greenhouse Environmental Control and Crop Production in Semi-Arid Regions
EditorsC. Kubota, M. Kacira
Place of PublicationLeuven (BE)
PublisherInternational Society for Horticultural Science
Pages339-346
Number of pages8
Volume797
ISBN (Print)978-90-66055-81-0
Publication statusPublished - 30 Sep 2008
EventISHS International Workshop on Greenhouse Environmental Control and Crop Production in Semi-Arid Regions - Tucson, AZ, United States
Duration: 20 Oct 200824 Oct 2008

Publication series

NameISHS Acta Horticulturae
Volume797
ISSN (Print)0567-7572

Conference

ConferenceISHS International Workshop on Greenhouse Environmental Control and Crop Production in Semi-Arid Regions
CountryUnited States
CityTucson, AZ
Period20/10/0824/10/08

Bibliographical note

The original publication is available at http://www.actahort.org/books/797/797_48.htm

Keywords

  • fan and pad
  • solar energy
  • energy efficiency

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  • Research Output

    • 1 Conference contribution

    A solar powered liquid-desiccant cooling system for greenhouses

    Lychnos, G. & Davies, P. A., 30 Sep 2008, International Workshop on Greenhouse Environmental Control and Crop Production in Semi-Arid Regions. Kubota, C. & Kacira, M. (eds.). Leuven (BE): International Society for Horticultural Science, Vol. 797. p. 95-102 8 p. (ISHS Acta Horticulturae; vol. 797).

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    Open Access
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  • Cite this

    Davies, P. A., Hossain, A. K., Lychnos, G., & Paton, C. (2008). Energy saving and solar electricity in fan-ventilated greenhouses. In C. Kubota, & M. Kacira (Eds.), International Workshop on Greenhouse Environmental Control and Crop Production in Semi-Arid Regions (Vol. 797, pp. 339-346). (ISHS Acta Horticulturae; Vol. 797). International Society for Horticultural Science. http://www.actahort.org/books/797/797_48.htm