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A feasibility study for Seltjarnarnes medium temperature geothermal field
Utilizing ORC cycle to cool geothermal fluid for district heating
Smári GuðfinnssonSunna Björg Reynisdóttir
Seltjarnarnes geothermal area
Well nr. Average well Temperature 2014
Depth Year drilled
SN-04 103°C 2.025 m 1972
SN-05 101°C 2.207 m 1981
SN-06 120°C 2.701 m 1985
SN-12 109°C 2.714 m 1994
Production Wells at Seltjarnarnes
Existing district heating system at Seltjarnarnes
Pump
District heating
T
~35°C
100-120°C
SN-04 SN-05 SN-06 SN-12
Buffer tank
Pump
Return water
Geothermal fluidCooling WaterORC Working fluidReturn water
District heating system with ORC utilization
Pump
Condenser
Turbine
Evaporator
Preheater
Geothermal fluidCooling WaterORC Working fluid
2
Regenerator
80°C
100-120°C
Seawater
SN-04 SN-05 SN-06 SN-12
Pump
District heating
T
~35°C
Pump
Buffer tank
Return water
Return water
Logged data series of 2014
1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep 1-Oct 1-Nov 1-Dec0
20
40
60
80
100
120
140 Well flow [L/s] Mixing of return water [L/s]
Date
Flow
[L/s
]
ORC power production based on installed capacity
0 100 200 300 400 500 600 700 800 900 1,000 1,100 1,2000
100
200
300
400
500
600
700
800
0%
13%
25%
38%
50%
63%
75%
88%
100%
Average production [kW] Average capacity utilization [%]
Installed capacity [kW]
Pow
er p
rodu
ction
[kW
]
Utiliz
ation
of i
nsta
lled
capa
city
[%]
Need for increased well flow with ORC installed
0 100 200 300 400 500 600 700 800 900 1,000 1,100 1,20005
1015202530354045505560
Average increased well flow [L/s] Maximum increased well flow [L/s]Minimum increased well flow [L/s]
Installed ORC capacity [kW]
Incr
ease
d w
ell fl
ow [L
/s]
Need for increased well flow with 700 kW ORC installed
1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep 1-Oct 1-Nov 1-Dec0
20
40
60
80
100
120
140
160Well flow in 2014 [L/s] Return water [L/s] Incresed well flow [L/s]
Date
Flow
[L/s
]
PRO’s Electricity production – for own use / sold to the grid Better control of water temperature to the end-users Further utilization of lower temperatures – spa/bathing/thermal beachCON’s Increased need for well flow Limited area available for industrial development Grótta – a delicate recreation area
Future possibilities
Any questionsThank you
Smári GuðfinnssonSunna B. Reynisdóttir
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