Technical and economic assessment of geothermal soil heating systems in row covered protected crops: A case study from Greece

The application of soil heating can securely transfer the harvest procedure of cultivated plantations to the early or very early season, maximizing in this way the marketable yield and added value. Extended experimentations with geothermal soil heating were elaborated under real operating field conditions based on the running harvest practices and asparagus rows protection techniques. Production and energy data have been collected and processed systematically during the harvest seasons 2002-2007 for direct use of geothermal waters in Neo Erasmio-Xanthi and for the seasons 2006-2016 for low grade shallow energy (heat pumps) applications in Chrysoupoli-Kavala, both in Northern Greece. The application of maximum heating loads in the order of 100-110 kW/ha along with maximum entering water temperatures at 35 °C has been demonstrated as the most cost effective energy option for off season harvest onset. The main objectives of the present comparative approach are (i) the conclusion on a suitable geothermal soil heating scheme for asparagus cultivation and (ii) the quantification and financial evaluation of soil heating impact on asparagus precocity and total yield at commercial scale. The performed analysis gives prominence to low enthalpy and shallow low grade geothermal energy as efficient, valuable and cost effective energy tools in soil heating.