31-10-2026146
Heating greenhouses during winter requires significant amounts of energy, particularly in Uzbekistan. The challenge is therefore not only to find alternative energy sources but also to reduce the energy required for heating. One promising approach involves the use of earth-to-air heat exchangers (EAHEs).
The technology relies on the relatively stable temperature of the ground. Outdoor air passes through underground pipes, exchanging heat with the surrounding soil. In winter, when the ground is warmer than the outside air, the system preheats the incoming air. In summer, the cooler soil helps lower its temperature. This reduces the heating or cooling demand placed on conventional equipment and can consequently lower energy consumption.
The potential of this technology has been demonstrated in experimental greenhouse studies. In February 2020, researchers conducted an experiment in Covilhã, Portugal, with the results published in 2023. The study compared two small-scale greenhouse models, each with a volume of approximately 5 m³. One was equipped with an earth-to-air heat exchanger consisting of a 29-metre-long spiral pipe installed at a depth of 3 metres, where the soil temperature was 13°C. Under one of the experimental operating conditions, heating energy consumption was reduced by 44.7% compared with the control greenhouse. However, the experiment involved small-scale models rather than commercial greenhouses. The findings therefore cannot be directly extrapolated to large-scale operations without further testing.
A separate study conducted in the Béchar region of southwestern Algeria demonstrated the technology's potential under arid climatic conditions. Researchers tested an earth-to-air heat exchanger consisting of a 66-metre-long polyvinyl chloride (PVC) pipe buried at a depth of 1.5 metres. Operating without mechanical fans, the system was able to increase the air temperature by up to 10°C in heating mode and decrease it by up to 11.9°C in cooling mode. Although the experiment was not conducted in a greenhouse, its findings demonstrate the potential of earth-to-air heat exchange for preheating and cooling air in arid regions.
The adoption of such technologies would align with Uzbekistan's efforts to improve energy efficiency and promote environmentally sustainable heating in the greenhouse sector. Under Presidential Resolution No. PP-371 of 13 October 2026, subsidies are provided from 1 November 2026 to 1 April 2030 to greenhouse operators using special heat-saving covers and/or specified energy-efficient and environmentally friendly heating systems. The subsidy covers 50% of the cost of electricity consumed for greenhouse operations during the October–March period. However, earth-to-air heat exchangers are not explicitly listed as a separate category of eligible equipment.
Against this background, the technology should be regarded as a promising option requiring further assessment under Uzbekistan's climatic and soil conditions, rather than as a solution automatically eligible for government subsidies. Local pilot projects should evaluate installation costs, fan electricity consumption where applicable, maintenance requirements, soil temperature and moisture, potential condensation, and actual energy savings. A comprehensive assessment of these factors would help determine the economic feasibility of the technology and the payback period for the initial investment.
If pilot projects demonstrate technical reliability and economic viability under local conditions, the inclusion of earth-to-air heat exchangers among government-supported energy-saving technologies could be considered.
Alisher Azizov
Chief Specialist, Center for Sustainable Development (NGO)