closed or open loop geothermal- NCARB practice question
For the question below, why is vertical open loop not the correct choice? It is more economical for the condition mentioned in question:
An architect is specifying a geo-exchange heat pump system for an office building. The building is on a site that has a significant concentration of groundwater and is conducive to well drilling. The owner wants the heat pump system that is the most cost-effective and energy-efficient.
Which heat pump system should the architect specify?
CORRECT RESPONSE
Vertical closed loop
For ground that is conducive to well drilling, the deep ground will be warmer in the winter and cooler in the summer than ground closer to the surface. Vertical systems are most efficient in ground that is conducive to well drilling. Closed loop systems use much less pumping energy than open loop systems.
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Page 605 from heating cooling and lighting states " A closed vertical loop is usually preferred because much less pumping energy is required", this statement compared both vertical loops, I assume that the correct answer was based on this statement... however there is no mention of which is most cost effective out of both system....or why less pumping energy is required....based on heating cooling and lighting (primary resource) vertical closed loop are the better choice over vertical open loop.
But I agree with Prof. Ermann,it would be great to hear from a geothermal heat pump expert.
Just doing a quick chatGPT :
"vertical closed-loop systems, the fluid is circulated in a closed circuit with less head pressure and lower flow rates, consuming less energy for pumping. "
It seems that closed loop systems although cost a bit more outperforms vertical open loop systems making it more energy efficient which is one of the keywords in the problem..
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