Jökull - 01.12.1961, Page 53

TABLE II.
Data on the exbloitation of three major thermal areas.
(One Gcal = 108 cal, one Tcal = 1019 cal).
(1) Natural flow of springs ..................
(2) Temperature of springs ...................
(3) Total natural heat output of area (as sen-
sible heat above 4° C) ..................
(4) Number of boreholes ......................
(5) Total drilling............................
(6) Free flow of boreholes....................
(7) Temperature of free flow .................
(8) Total heat output of boreholes (as sensible
lieat above 4° C) .......................
(9) Effective heat output of boreholes (as sen-
sible heat above 4° C)...................
(10) Annual load-factor assumed in item (9') . .
(11) Estimated total present cost of drilling and
installations ...........................
(12) Operation cost ..........................
(13) Production cost at present prices per unit
heat in thermal area ....................
(14) Efficiency of distribution ..............
(15) Production cost at present prices per unit
heat delivered in Reykjavik .............
of comparing the output of the thermal areas
on a unified basis. Distribution costs are taken
into account in item (15).
In item (9) the annual load-factor selected for
Reykjavik and Reykir is 0.80 whereas a figure
of 0.40 is applied in the case of the Hengill.
The reason for the latter figure is the fact that
considerable calcite scaling is encountered in
the case of the high-temperature boreholes.
The holes have to be cleaned at short intervals,
resulting in a considerable reduction of the ef-
fective annual flow.
The cost in item (11) includes piping to one
point in the areas. The operation cost in item
(12) includes interest, clepreciation, mainten-
ance and cost of pumping the water to the point
of collection. No pumping is included in the
case of the Hengill area.
The relatively high operation cost in the case
of the Hengill area is due to the fact that the
high-temperature boreholes have to be cleaned
and redrillecl at regular intervals.
Unit Reykjavik Reykir Hengill
(southern part)
Liters/sec 10 120
”C 88 83
Gcal/hour 6 40 100
40 70 8
Kilometers 18 24 6
Liters/sec 134 370 500
°C 80-138 80-96 180-220
Gcal/hour 55 116 380
Tcal/year 270 440 1,000
0.80 0.80 0.40
Million $ 0.92 1.20 0.80
Million f/year 0.13 0.17 0.30
f/Gcal 0.48 0.39 0.30
0.83 0.75
f/Gcal 0.58 0.52
Item (13) representing the production cost per
unit heat is sirnply the ratio between items (12)
and (9). On the other hand, item (15) is the
ratio between items (13) and (14). The pro-
duction cost per unit heat given in item (13) is
very low compared with the cost per unit heat
in ordinary fuel, as coal and oil. On the other
hand, the figures given are of the same order
as the well-liead cost per unit heat in natural
gas at conditions in oilfields in the U. S. A.
(b) Field operation.
The figures in item (9) in TABLE II are
computed on the basis of the free flow of the
boreholes and a relatively high annual load-
factor in the case of the Reykjavik and Reykir
areas. The load-factor of 0.80 is higher than
can be obtained in ordinary space heating in
Iceland.
This procedure is based on the assumption of
the application of submerged pumps in the
boreholes. Pumping has the advantage that wat-
51