A closed two-phase system can also be used in an active mode, and is applicable when the ambient air temperature is above freezing. Such systems are termed “hybrid thermosyphons” and are often needed in temperate applications where reliance on low ambient air temperatures is not feasible. A typical system consists of multiple Thermoprobes, an active (powered) condensing unit, a two-phase working fluid, an interconnecting supply and return piping network, and a control system. Thermoprobes consist of an evaporator and a passive condenser section. Coupled with an active condenser, a Thermoprobe functions actively and removes heat from the ground without direct dependency on the ambient air temperature. The hybrid system can function in both passive and active modes simultaneously when ambient temperatures are sufficiently low, reducing energy costs.
Current state of development and certification
This technology has been in use since 1960 and has been utilized on over 900 installations. Most of these applications have been in arctic climates where soil freezing is accomplished passively (i.e. without the use of power). Active-passive “hybrid” systems have been used in climates where low winter temperatures do not prevail. Such systems are normal for temperate climates. The essence of thermosyphon technology is well developed irrespective of the climate it is applied in.
Availability of technology
AFI has been continuously developing, fabricating, installing, operating, and advancing thermosyphon technology since the corporation’s inception in the early 1970s. As such, the company has the capability and capacity to apply the technology to almost any situation in a very expeditious and professional manner. The technology is well developed and available for application in real situations — it is not an embryonic technology that needs years of developmental engineering to prove.
Improvements are developed with every new project, and as techniques improve in-house and in related sectors of the geotechnical industry. Drilling and installation techniques are examples of related technologies that are rapidly advancing, improving the practicality of placing thermoprobes in complex underground configurations.