There is no doubt that horticulture has become a new track to promote the development of modern agriculture and a new way to increase food supply. Facing the increasingly changing and unstable environment, the construction of horticulture systems is accelerating to varying degrees around the world. However, the high energy consumption continues to hinder the industrial development. With the advancement of technology, the discussion and application of new energy methods such as biomass fuel, geothermal energy, combined heat and power, and solar energy are gradually increasing.
Caijin Smart Agricultural Industrial Park in Dezhou, Shandong, is one of the projects utilizing new energy. The park covers an area of around 34 hectares, with a total investment of 473 million RMB. The park uses 'medium-deep geothermal energy' to replace 'natural gas.' In accordance with the balance between recharge water and extracted water, it has built 4 extract wells and 6 return wells. At the same time, it has adopted "high-temperature water source heat pump" technology to build a geothermal energy station. The total heating capacity is about 21,712kw, which can meet the heating demand of 254,000 square meters of greenhouse.
The project utilizes Neogene Guantao Formation thermal storage, with a burial depth of more than 1,200m, a single well water output of 100m3/h, and a water temperature of 52°C. The well casing adopts standard petroleum casing (J55-steel), with a service life of more than 50 years. Geothermal wells adopt directional well-forming technology to ensure reasonable well spacing, which can effectively prevent 'thermal breakthroughs' during the tailwater reinjection process.
Also, the project adopts a three-stage heat exchange mode. After the geothermal water (52℃) is exchanged by the three-stage heat exchanger (about 17℃), it is recharged through the recharge well to more than 1200m deep, achieving "equal recirculation of the same layer, obtain heat without consuming water" and promote the sustainable development and utilization of geothermal energy.
"This is the first time that 'high-temperature water source heat pump' technology is used in Dezhou City to perform three-stage heat exchange and temperature increase. The heating circulating medium is heated to (35-46°C) by primary heat exchange, then raised to (46-65°C) by the second-level customized high-temperature centrifugal heat pump unit, and finally enters the third-level customized high-temperature screw heat pump unit to raise the temperature to (65-80℃) to provide heat to the greenhouses. Through the efficient use of geothermal resources, it can save 101,500 tons of standard coal and reduce carbon dioxide emissions by 24,000 tons. The smart agricultural greenhouse can save more than 11 million RMB in annual operating costs," said the project leader.
"We also built a smart energy control system and monitoring platform during the project. The control system can automatically control the outlet water temperature and flow according to changes in outdoor temperature and the heat demand of the greenhouse, ensuring efficient, energy-saving, and stable operation of the entire system. The monitoring platform monitors the water level, water outlet temperature, flow rate of the extraction well and the water level, recharge temperature, recharge volume, and other data of the recharge well in real time to achieve efficient management and scientific utilization."
Dai Jinlei