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Direct Use of Geothermal Resources 203

Table 11.1
capacity of Installed direct Use applications in 2005 (continued)
capacity Use Use capacity
country (mwt) (TJ/yr) (Gwh/yr) Factor
New Zealand 308.1 7086 1968.5 0.73
Norway 600 3085 857 0.16
Papua, New Guinea 0.1 1 0.3 0.32
Peru 2.4 49 13.6 0.65
Philippines 3.3 39.5 11 0.38
Poland 170.9 838.3 232.9 0.16
Portugal 30.6 385.3 107 0.4
Romania 145.1 2841 789.2 0.62
Russia 308.2 6143.5 1706.7 0.63
Serbia 88.8 2375 659.8 0.85
Slovak Republic 187.7 3034 842.8 0.51
Slovenia 49.6 729.6 202.7 0.47
South Korea 16.9 175.2 48.7 0.33
Spain 22.3 347.2 96.5 0.49
Sweden 3840 36,000.00 10,000.80 0.3
Switzerland 581.6 4229.3 1174.9 0.23
Thailand 2.5 79.1 22 1
Tunisia 25.4 219.1 60.9 0.27
Turkey 1495 24,839.90 6900.5 0.53
Ukraine 10.9 118.8 33 0.35
United Kingdom 10.2 45.6 12.7 0.14
United States 7817.4 31,239.00 8678.2 0.13
Venezuela 0.7 14 3.9 0.63
Vietnam 30.7 80.5 22.4 0.08
Yemen 1 15 4.2 0.48
Total 28,268.00 273,372.10 75,942.80 0.31

Source: Lund, J. W., Freeston, D. H., and Boyd, T. L., Geothermics, 34, 691–727, 2005.

share certain engineering approaches. Underlying all of these are the basic principles of heat trans-
fer. The following section describes these principles and how they are employed to address specific
design needs.

The naTUre oF Thermal enerGy TransFer

Thermal equilibrium is achieved when coexisting systems or components of a system reach the same
temperature, as discussed in Chapter 3. Therefore, heat will spontaneously transfer from a warm to a
cold body. It is this fundamental principle upon which all direct use applications rely. It is, however,
the driving force that also results in unwanted heat losses as heat is moved from one place to another.
The ability to manage heat movement by minimizing unwanted losses and maximizing useful heat
is required to construct and operate an efficient direct use application. The mechanisms that accom-
plish heat transfer are conduction, convection, radiation, and evaporation. Each of the applications
shown in Figure 11.1 are affected by one or more of these heat transfer mechanisms and it is for
this reason that the transfer mechanisms are discussed below. Although these were also covered in
Chapter 2, this discussion emphasizes materials and processes that will be encountered in the devel-
opment of direct use applications, rather than the bulk Earth processes discussed previously.