Jökull - 01.12.1982, Page 27

Fig. 1. The geothermal field
at Reykholtsdalur in Borgar-
fjördur. (From Saemundsson
and Fridleifsson, 1980).
Mynd 1. Jarðhitasvœðið í Reyk-
holtsdal.
en in the sketch in Fig. 1. The total integrated flow
of all springs is about 400 kg/s with a temperature of
80°C to 100°C. The base temperature of the system
is probably 130°C (Bodvarsson 1979). Using this fig-
ure as the eflective temperature of the thermal water
being generated, the total dissipation of heat by the
Reykholtsdalur system is found to be 220 MW.
Since this result does not include any subsurface
fiow losses, the figure is probably a low estimate.
Arnason (1976) has traced the recharge of the
system to the highland 40 to 50 km to the east of the
area. The recharge is indicated in Fig. 2.
Because of the great power of the Reykholtsdalur
system it is of interest to estimate the physical
dimensions of the rock/water heat transfer struc-
tures that are required to support the dissipation of
heat in the area. For this purpose, we will apply the
concepts and relations presented in the previous
section. Moreover, leaning on the arguments set
forth above, it appears appropriate to assume that
any transient heating state was initiated about 104
years ago. In view of the possibilities for elevated
subsurface temperatures inthis region (Saemundsson
and Noll 1974), the regional vertical temperature
gradient is taken to be g = 80°C/m. The procedures
involved are straight forward and it is therefore
convenient to present the results as in Table 1.
JÖKULL 32. ÁR 25
DISCUSSION
Table 1 includes the essential results with regard
to the Reykholtsdalur system. Clearly, since the
heat transfer models applied represent idealiza-
tions, the data have to be viewed with proper caut-
ion. In particular, the single pipe model is pure
idealization of doubtful geological relevance. How-
ever, it is instructive to observe that the single pipe is
Fig. 2. Estimated location of the recharge of the
Reykholtsdalur system.
Mynd 2. Upþrunasvteði jarðhitavatnsins í Reykholtsdal.