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The utilisation of geothermal energy in the agricultural sector of Greece

Tomato sales at farmers' market in Greece (source: flickr/ Didier BIGAND, creative commons)
Alexander Richter Alexander Richter 23 Dec 2018

While there is no geothermal power plant in Greece yet - maybe the time is ripe? - geothermal energy is widely used in the agricultural sector of the country heating greenhouses for the production of tomatoes, vegetables etc. - and also for dehydrating food.

A recent article in Greek publication Ypaithros describes how geothermal energy is being used in the agricultural sector in Greece. This is a great overview, applicable to so many other geographics.

Geothermal energy as the heat of the Earth, a mild, renewable energy source with negligible to zero environmental impact. It can be used either for power generation (> 90 degrees Celsius) or “directly”, ie directly as heat, in various applications such as bathing, industrial use, agricultural, space heating, district heating, etc. (> 25 degrees Celsius). In the case of lower temperatures (<25 degrees Celsius), the utilization of the Earth’s heat is achieved by means of Geothermal Heat Pumps (GHG). This is the so-called “shallow geothermal”, which has been enormously applied in recent decades, mainly for space heating and cooling, but also in the primary sector.

Greece is a particularly favourable geothermal country with many areas of significant geothermal interest , of which 32 have been officially designated as “geothermal fields”. The systematic exploitation of geothermal resources in our country began in the 1980s, but almost four decades later, it is limited to bathing and the farming sector (mainly greenhouse heating), and its huge geothermal potential is not used for electricity generation. The exploitation of shallow geothermal energy is the only industry that has been impressively growing for Greek data, with more than 3,000 installed GMP units, almost exclusively for indoor air conditioning geothermal in Greece.

A sleeping energy giant

Excluding shallow geothermal energy, the most significant investments that have been made in the geothermal market in recent years are all in low enthalpy (25-90 degrees Celsius) and in the primary sector. Over the last five years, more than € 20 million has been invested in the construction of infrastructure projects for the exploitation of geothermal energy (drilling, transmission and distribution networks of hot water, thermal power stations, etc.) and greenhouse units in only two geothermal fields, Neos Erasmus-Manganos Xanthi and Eratino Chrysoupoli in Kavala.

In the New Erasmus-Manganos field of Xanthi , geothermal is used to meet the heating needs of 140 acres of tomato and cucumber greenhouses with 60 degrees Celsius geothermal water. Cost savings from geothermal use are estimated to exceed 60% compared to other conventional fuels. Also, the warm waters of the region have been used since 2001 for the dehydration of tomatoes and other agricultural products and since 1997, a world-wide greenhouse application of green and white asparagus (100 acres), through subsoil heating.

In 2016, the Municipality of Nestos completed the construction of projects in the Erateinos geothermal field in Kavala, with a budget of more than EUR 10 million. In 2017, the first investment in the area concerned the construction of a standard greenhouse unit of 35 acres, producing rooted cuttings of ornamental plants. The thermal needs of the unit are covered by 70 degrees Celsius geothermal fluids through the municipality’s distribution network. The first phase of the investment has already been completed and amounted to EUR 7 million, while an extension of 25,000 acres is planned, with an estimated additional cost of EUR 3 million.

Open-cropping under low coverage can also be done by exploiting shallow geothermal energy and the use of GAT , as is the case in Chrysoupoli, Kavala. This is 190 hectares of white asparagus plantations, for the use of which water is used at <20 degrees Celsius). According to ELGO – “Dimitra”, the extra revenues, compared to adjacent unheated plantations, amount to EUR 1,000-1,200/ acre.

The cultivation of spirulina with the help of geothermal is also an interesting application, which is being implemented in Therma Nigrita of Prefecture of Serres since the 1990s. Currently, two companies with three units are operating in the area, using heat exchangers water (50 degrees Celsius) of the area.

Several and very remarkable works are underway, such as district heating of public buildings and settlements and the heating of greenhouses in the geothermal field of Aristos Alexandroupolis, as well as the construction of 100 acres of tomatoes greenhouses in the area of Kesani , Xanthiwhich will be heated by 82 degrees Celsius. These are two investments with a total budget of over EUR 13 million so far. In the earliest stage, the geothermal exploration projects in the Akropotamou Kavala area are located, where the development of greenhouses and the heating of soil crops are in a relatively mature stage.

New perspectives on the use of geothermal energy in the agricultural sector

An interest in the development of geothermal energy has been expressed by several local government authorities in Northern Greece, who are apparently aware of the significant benefits of the use of geothermal resources and intend to take action to attract investment and create geothermal plants , having the alliance with the great acceptance of local societies. However, in a country with such rich potential and very good operating conditions, geothermal has not yet found its role in the national and local energy balance.

On the basis of today’s technology, the use of geothermal energy in the agricultural sector has become particularly competitive given the very low production costs of thermal MWh (10-30 euros), the possibility of total peak load coverage and constant availability. In the near future, the penetration of shallow geothermal energy systems in the agricultural sector should be significantly strengthened. Due to favourable geological conditions, proper and long-term experience of significant economic and energy savings that are proven to be achieved, the use of GMHPs in the energy support of small productive operations is considered particularly attractive.

Geothermal: In the greenhouses the main exploitation applications

The exploitation of geothermal energy in the agricultural sector is broad, including a number of application areas. According to a report by the European Geothermal Energy Council (EGEC), 7% of the global use of geothermal energy is exploited in the primary sector. More specifically, 4.5% is used for the heating of open-grown greenhouses and subsoil, 2% for aquaculture facilities and 0.4% for food processing (mainly drying).

The most common application is found in the Netherlands , which ensures optimal temperature conditions for plant growth with mild environmental impact. “But the most important benefit is the cost reduction of the energy produced, even reaching 80%. In addition, the operating cost of a greenhouse unit is reduced by 5% -6%, “EGEC said. According to the report, 31 countries used geothermal energy for heating greenhouses in 2015, with Turkey, Russia, Hungary, China and the Netherlands leading the world. It is estimated that the same year was heated by geothermal energy over 13,000 acres worldwide, an increase of 16% compared to 2010.

Source: Ypaithros