ENhanced hanced G Geothermal eothermal I Innovative nnovative N Network for etwork for E Europe ( urope (ENGINE ENGINE) ) EN Optimized geothermal Optimized geothermal binary power cycles binary power cycles Kontoleontos E., Mendrinos D., Karytsas C. Kontoleontos E., Mendrinos D., Karytsas C. Centre for Renewable Energy Sources 19 th km Marathonos ave., 19009 Pikermi Attikis, Greece
LOW- -BIN project BIN project LOW • ORC power plant ORC power plant • for 65 65- -90 90° °C C geothermal water geothermal water for • ORC heat & power ORC heat & power • cogeneration plant cogeneration plant for 120 120- -150 150° °C C geo geo- -water water for and 60/80 60/80° °C C district heating district heating and Industrial partner: TURBODEN Industrial partner: TURBODEN Supported by DG-TREN (FP6)
Isobutane (R600a) and R134a Isobutane (R600a) and R134a as working fluids as working fluids • widely used with excellent results in the heat widely used with excellent results in the heat • pumps and cooling/refrigeration industry pumps and cooling/refrigeration industry • available in the market available in the market • • The necessary parts for a Rankine cycle machine The necessary parts for a Rankine cycle machine • are available in the market are available in the market • CARRIER, lately developed low cost 200 kWe CARRIER, lately developed low cost 200 kWe • ORC units using R134a. Two units commenced ORC units using R134a. Two units commenced operation in August- -December 2006 December 2006 in “Chena”, in “Chena”, operation in August Alaska, USA, utilizing 74°C water Alaska, USA, utilizing 74°C water
Shell & tubes condenser Shell & tubes condenser 1 = U ( ) Overall heat transfer: ln / Overall heat transfer: 1 1 o A A r r + + o o o i π 2 A h kL h i i o ( ) 0 . 25 ⎡ ⎤ 3 ρ ρ − ρ Laminar condensation Laminar condensation gh k = ⎢ ⎥ v fg f 0 . 725 ( ) h on tubes surface: µ − on tubes surface: o ⎢ ⎥ d T T ⎣ ⎦ f g w Nuk = h i D Turbulent flow in tubes: Turbulent flow in tubes: = 0 . 8 0 . 4 0 . 023 Re Pr Nu ⋅ ⋅ ρ u D = Re µ
Plate H.E. as evaporator Plate H.E. as evaporator Second side: working fluid Second side: working fluid One side: Geothermal water One side: Geothermal water ⇒ Two Phase ⇒ Vapor Liquid ⇒ Two Phase ⇒ Vapor Liquid 1 1 1 1 = = = = , , U U U U ∆ ∆ ∆ 1 1 1 / 1 1 1 1 / 1 1 total sp l tp sp g x x x + + + + + + + + U U U h ktit h h ktit h h ktit h / / / / sp l tp sp g sp l gw tp gw sp g gw __________________________________________________________________ 0 . 4124 ⎡ ⎤ 0 . 12 2 0 . 35 ⎛ ⎞ ⎛ ⎞ Re ⎛ ⎞ Evaporation heat transfer 65 Evaporation heat transfer h k p ⎜ ⎟ ⎜ ⎟ = ⎢ ⎥ ⎜ ⎟ l fg l h C ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ β tp ⎝ ⎠ ⎢ ⎥ ⎝ ⎠ ⎝ ⎠ D L p ⎣ ⎦ e P cr ⋅ ⋅ ρ u L = Re µ 0 . 074 1050 = − c 0 . 2 f Re Re Single phase heat transfer Single phase heat transfer c 1 = ⋅ f St 2 2 Pr 3 = ⋅ ⋅ Re Pr Nu St ⋅ Nu k = h / , sp l g L
Rankine cycle optimisation optimisation Rankine cycle Objectives: Objectives: • Maximize Maximize overall net conversion efficiency conversion efficiency of the plant • ( ) − − ⋅ − W N h h m N 4 5 η = = turbine pump wf pump ( ) − ⋅ cycle Q h h m 3 2 heatexch wf • Minimize Minimize the cost cost of the plant → Minimize both Heat Exchangers surface → Minimize both Heat Exchangers surface Constraints: Constraints: Variables: Variables: Net Power Output P 2 , m gr , m wf , ∆Τ ∆Τ Η , ∆Τ ∆Τ C P 2 , m gr , m wf , Η , ± 5kW C e ± 200 kW e 5kW e 200 kW e using the EASY software code (Evolutionary Algorithm System) by National Technical University of Athens, ref. http://velos0.ltt.mech.ntua.gr/EASY
ORC machine for 65° °C: R134a C: R134a ORC machine for 65 optim al solutions - R134a 10 9.8 9.6 exchangers' surface 9.4 9.2 9 8.8 8.6 8.4 0.066 0.067 0.068 0.069 0.07 0.071 0.072 0.073 0.074 binary plant's overall efficiency
ORC machine for 65° °C: R600a C: R600a ORC machine for 65 optim al solutions - isobutan 16 15 exchangers' surface 14 13 12 11 10 0.06 0.062 0.064 0.066 0.068 0.07 0.072 binary plant's overall efficiency
ORC machine for 65° °C: C: ORC machine for 65 R134a vs Isobutane R134a vs Isobutane Com parison R134a - isobutan 18 isobutan R134a 16 exchangers' surface 14 12 10 8 0.06 0.062 0.064 0.066 0.068 0.07 0.072 0.074 binary plant's overall efficiency
ORC machine for 65° °C: C: ORC machine for 65 R134a vs Isobutane R134a vs Isobutane Variable Isobutane R134a Variable Isobutane R134a P 2 (bar) 6.19 11.99 P 2 (bar) 6.19 11.99 m geothermal water (kg/sec) 46 6 51.2 m geothermal water (kg/sec) 4 51.2 m working (kg/sec) 10.2 17.5 m fluid (kg/sec) 10.2 17.5 working fluid ( ° C) 21.8 1.8 18.6 ∆Τ H ∆Τ H ( ° C) 2 18.6 ( ° C) 7.5 7.5 ∆Τ C ∆Τ C ( ° C) 7.5 7.5 pump power pump power ( ( kW kW) ) 3. 3 .9 9 13.4 13.4 cooling water flow water flow (kg/sec) (kg/sec) 119 116 cooling 119 116 surface of the condenser (m 2 2 ) ) 7.0 5.5 surface of the condenser (m 7.0 5.5 surface of the heat exchanger (m 2 2 ) ) 5.7 4.0 surface of the heat exchanger (m 5.7 4.0 total H.E. surface (m 2 2 ) ) 12.7 9.5 total H.E. surface (m 12.7 9.5 net conversion efficiency 7.04 7.16 net conversion efficiency 7.04 7.16
ORC heat & power cogeneration ORC heat & power cogeneration source: 120° °C, cooling: 60/80 C, cooling: 60/80° °C C source: 120 optim al solutions - R134a 40 35 exchangers' surface 30 25 20 15 0.048 0.05 0.052 0.054 0.056 0.058 0.06 0.062 binary plant's overall efficiency
R134a ORC plants R134a ORC plants R134a - tem perature threshold at 65,100,120 45 65 100 Cogeneration 120 ° C-60/80 ° C 40 120 surface of the exchangers 35 30 25 20 15 Low temperature 65 ° C 10 Standard 100 ° C 5 0.045 0.05 0.055 0.06 0.065 0.07 0.075 0.08 0.085 overall efficiency of the binary plant
R134a ORC plants R134a ORC plants Heat & power Power Standard binary Variable cogeneration generation power plant, 120 ο C 100 ο C 65 o C P 2 (bar) 34.99 11.99 15.52 m geothermal (kg/sec) 52 51.2 45 m R134a (kg/sec) 35 17.5 17.8 ∆Τ H ( ° C) 26 18.6 20.0 ∆Τ C ( ° C) 20 7.5 7.5 Cooling Temp ( ° C) 60 10 10 Condensing Temp ( ° C) 80 30 27 R134a pump power (kW) 58 13.4 18.5 cooling water flow (kg/sec) 66 116 110 Condenser surface (m²) 22.0 5.5 4.6 Surface of the PHE (m²) 2.0 4.0 5.4 Total H.E. surface (m²) 24.0 9.5 10 Net conversion efficiency 5.93 7.16 7.7 Net electrical Power (kW) 207 202 204
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