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