<?xml version="1.0" encoding="utf-8"?><!DOCTYPE Zthes SYSTEM "http://zthes.z3950.org/xml/zthes-05.dtd">  <Zthes><term><termId>31377317</termId><termName>borehole heat exchangers</termName><termType>PT</termType><termNote><![CDATA[ Borehole heat exchangers are used to extract heat stored in the ground by means of a vertical borehole with a “closed loop” collector installation with the help of a geothermal heat pump. A collector hose filled with a carrier fluid is installed in the borehole which is drilled into a geothermal aquifer. This circulating carrier fluid absorbs heat from the surrounding bedrock, which is then extracted by the heat pump for use in space-heating via piping connected to the heat exchanger. ]]></termNote><termCreatedDate>2026-03-30 20:41:46</termCreatedDate><relation><relationType>UF</relationType><termId>31377318</termId><termName>borehole heat exchanger</termName><termType>ND</termType></relation><relation><relationType>UF</relationType><termId>31377319</termId><termName>downhole heat exchangers</termName><termType>ND</termType></relation><relation><relationType>UF</relationType><termId>31377320</termId><termName>heat exchanger, borehole</termName><termType>ND</termType></relation><relation><relationType>BT</relationType><termId>31347233</termId><termName>heat exchangers</termName><termType>PT</termType></relation></term>  </Zthes>