User:M.ali.sajjadi/Formation Thermal Conductivity Test for Geothermal Applications

A formation thermal conductivity test is important in determining the rate that heat is transferred from the earth into the ground heat exchanger and is a critical part of the accurate sizing calculations for geothermal system.

The performance of an earth energy ground loop system can be greatly dependent on the characteristics of the ground underlying the site and the field configuration design. A Formation Thermal Conductivity (FTC) test allows an opportunity to predict the performance of a singular test well, so that the information can be applied to the design of a full scale ground loop system.

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The geothermal system designer uses the FTC test information to size the ground loop with respect to the calculated design heating and cooling loads. Without the FTC information, over-sizing or under-sizing of the ground loop may occur. An over-sized ground loop will increase capital costs, while delivering little increased performance. An under-sized ground loop could diminish system economics by requiring increased energy use from the system heat pumps and causing the field to fall below or climb above the acceptable operating temperature. It is strongly recommended that the thermal conductivity and diffusivity values are used by an experienced geothermal field designer. It is imperative that the geo exchange field be sized for the anticipated design heating and cooling load of the future facility in order to adequately predict the effect of loads on the borehole field. Final field configuration can also greatly affect the final operating success of a geothermal system. To minimize field design errors, FTC information and field design, should be analyzed by a qualified Professional Engineer who regularly practices in the field of geothermal design and energy modeling.

With accurate geological data, decisions regarding the design of the ground heat exchanger, the number and size of boreholes, the type of grout to be used, and the size of heat pumps can be made with accuracy. Because the design and overall loop length of the ground heat exchanger could impact the efficiency of a geothermal system, the cost of this test can be economically justified in larger installations.

Ali Sajjadi 18:17, 4 August 2009 (UTC) [http://www.meggeothermal.ca/index.php?id=9 Ref. website]