Thermo-economic evaluation of low global warming potential alternatives to HFC-245fa in Organic Rankine Cycles

Thermo-economic evaluation of low global warming potential alternatives to HFC-245fa in Organic Rankine Cycles

Available online at www.sciencedirect.com ScienceDirect Availableonline onlineatatwww.sciencedirect.com www.sciencedirect.com Available Energy Energ...

827KB Sizes 0 Downloads 25 Views

Available online at www.sciencedirect.com

ScienceDirect

Availableonline onlineatatwww.sciencedirect.com www.sciencedirect.com Available Energy Energy Procedia Procedia 00 00 (2017) (2017) 000–000 000–000

ScienceDirect ScienceDirect

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

Energy Procedia 142 Energy Procedia 00(2017) (2017)1199–1205 000–000 www.elsevier.com/locate/procedia

9th International Conference on Applied Energy, ICAE2017, 21-24 August 2017, Cardiff, UK

Thermo-economic evaluation of low global warming potential alternatives to HFC-245fa in on Organic Rankine Cycles The 15th International Symposium District Heating and Cooling Francisco Molésa,*, Joaquín Navarro-Esbría, Bernardo Perisa,

a a

Francisco Molés *, Joaquín Navarro-Esbrí , Bernardo Peris , Assessing thea, Ángel feasibility of usinga,the heat demand-outdoor Adrián Mota-Babiloni Barragán-Cervera Konstantinos (Kostas) Kontomarisb ISTENER Research Department and Campus Riu s/n, I, ISTENER Research Group. Group. function Department of of Mechanical Mechanical Engineering and Construction, Construction, Campus de de Riu Sec Secdemand s/n, Universitat Universitat Jaume Jaume I, E12071, E12071, temperature for aEngineering long-term district heat forecast Castellón (Spain). bb

Castellón (Spain). DuPont Fluorochemicals, Centre Road, Chestnut Run Wilmington, Delaware 19805 (USA). DuPonta,b,c Fluorochemicals, 974 974 Centre Road, Chestnut Run Plaza Plaza 711, 711, a a b Wilmington, Delawarec19805 (USA).

I. Andrić

*, A. Pina , P. Ferrão , J. Fournier ., B. Lacarrière , O. Le Correc

a

IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal Abstract b

Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France In the present work, a thermo-economic evaluation of the low global warming potential fluids HCFO-1233zd-E, HFO-1336mzzc

Z and HFO-1234ze-Z as alternatives to HFC-245fa in organic Rankine cycle systems for low temperature heat sources is carried out. A thermodynamic organic Rankine cycle model is extended with the overall cost of the system, and it is used to identify the system parameter values for each working fluid considered that minimize the specific investment cost at a given set of the heat Abstract source and sink inlet temperatures. Thereby, the results show that HCFO-1233zd-E and HFO-1336mzz-Z present higher efficiencies than HFC-245fa, while HFO-1234ze-Z presents efficiency HFC-245fa. The low global warming potential District heating networks are commonly addressed in thelower literature as onethan of the most effective solutions for decreasing the working fluids result in lower specific investment cost values than HFC-245fa. HFO-1336mzz-Z presents the lowest specific greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat investment and changed highest efficiency values among working fluids of interest the range operating conditions sales. Duecost to the climate conditions and the building renovation policies,throughout heat demand in theoffuture could decrease, studied. prolonging the investment return period. © 2017 The Authors. Published by Elsevier Ltd. main of this paper isby to Elsevier assess the feasibility of using the heat demand – outdoor temperature function for heat demand ©The 2017 Thescope Authors. Published Ltd. Peer-review under responsibility of thelocated scientific committee of the 9thwas International Conference Applied Energy. forecast. The district of Alvalade, in Lisbon (Portugal), used as aConference case study.on district is consisted of 665 Peer-review under responsibility of the scientific committee of the 9th International onThe Applied Energy. buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district

Keywords: low GWP HFC-245fa; Organic Rankine Cycle; Keywords: lowscenarios GWP fluids; fluids; HFC-245fa; Organic Rankine Cycle; thermo-economic. thermo-economic. renovation were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were

compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications Nomenclature (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation P pressure (kPa) scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). QThe valuethermal power (kW) increased on average within the range of 3.8% up to 8% per decade, that corresponds to the of slope coefficient in theinnumber heating volumeofratio (-) hours of 22-139h during the heating season (depending on the combination of weather and rvvdecrease built renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the Wcoupled electric power scenarios). The (kW) values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations. © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and ** Corresponding Corresponding author. author. Tel.: Tel.: +34-964-728-134; +34-964-728-134; fax: fax: +34+34- 964-728-106. 964-728-106. Cooling. E-mail E-mail address: address: [email protected] [email protected]

Keywords: Heat demand; Forecast; Climate change 1876-6102© 2017 1876-6102© 2017 The The Authors. Authors. Published Published by by Elsevier Elsevier Ltd. Ltd. Peer-review Peer-review under under responsibility responsibility of of the the scientific scientific committee committee of of the the 9th 9th International International Conference Conference on on Applied Applied Energy. Energy.

1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling.

1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the 9th International Conference on Applied Energy. 10.1016/j.egypro.2017.12.381

1200 2

Francisco Molés et al. / Energy Procedia 142 (2017) 1199–1205 Author name / Energy Procedia00 (2017) 000–000

Greek symbols ε regenerator effectiveness (%) η efficiency (%) Subscripts cond condenser evap evaporator exp expander n net Acronyms GWP Global Warming Potential (-) HCFO Hydrochlorofluoroolefin HFC Hydrofluorocarbon HFO Hydrofluoroolefin ODP Ozone Depletion Potential (-) ORC Organic Rankine Cycle SH Superheating (K) SIC Specific Investment Cost (€/kW) 1. Introduction The Organic Rankine Cycle (ORC) has been attracting increasing attention in recent years. The choice of the ORC working fluid has an important influence on the system efficiency. Quoilin et al. [1] highlighted HFC-245fa as a common working fluid in commercial ORC installations, used mainly in waste heat recovery from low temperature sources. Additionally, they observed that, at present, most commercial ORC plants follow a simple design: sub-critical operating conditions, single-component working fluids, single evaporation pressure, and possible use of a recuperator heat exchanger. Turning attention to environmental issues, HFC-245fa has zero Ozone Depletion Potential (ODP) but presents a Global Warming Potentials (GWP) of 858 [2]. Some low GWP working fluids are being studied to replace HFC245fa in various applications, including ORC systems. HCFO-1233zd-E is a hydrochlorofluoroolefin (HCFO) with a GWP of 1 [2]. Despite the presence of chlorine in its molecule, HCFO-1233zd-E was found to have a low ODP (of 0.00034) due to its very short atmospheric lifetime. HFO-1336mzz-Z (commercially also referred to as DR-2) is a hydrofluoroolefin (HFO) with a GWP of 2 [2] and zero ODP. HFO-1234ze-Z is an HFO with a GWP of 1 [2] and zero ODP; it is expected to be slightly flammable. Molés et al. [3] predicted the attractive thermodynamic performance of ORC systems for low temperature heat recovery using HCFO-1233zd-E and HFO-1336mzz-Z as alternatives to HFC-245fa. They also concluded that the energy efficiency of ORCs with HCFO-1233zd-E and HFO-1336mzz-Z is benefitted substantially by the use of a recuperator. However, a thermodynamic comparison alone cannot conclusively indicate the optimal working fluid; the effect of differences among working fluids in thermodynamic and heat transfer properties on the size and cost of the system equipment components [4] must also be considered. In the present work, a thermo-economic evaluation of the low GWP fluids HCFO-1233zd-E, HFO-1336mzz-Z and HFO-1234ze-Z as alternatives to HFC-245fa in ORC systems for low temperature heat sources is carried out. The rest of the paper is organized as follows: Section 2 describes the ORC system model developed; Section 3 reports and discusses the main results; finally, Section 4 summarizes the main conclusions. 2. ORC system model A thermodynamic steady state model of the ORC system is made using Engineering Equation Solver [5] in combination with the REFPROP [6] and CoolProp [7] libraries for retrieving working fluid properties.



Francisco Molés et al. / Energy Procedia 142 (2017) 1199–1205 Author name / Energy Procedia00 (2017) 000–000

1201 3

A regenerative ORC system, shown in Fig. 1, has been considered. It works in subcritical condition, and it is very similar to the basic ORC cycle. The working fluid is pumped through the economizer and the evaporator where it is heated to the highest enthalpy state in the cycles. Then it is expanded to produce mechanical power, which is transformed into electricity through a generator. Finally, the fluid is condensed, subcooled and pumped again to close the loop. The system includes an internal heat exchanger as a regenerator to transfer heat from the superheated vapor exiting the expander to preheat the pressurized liquid entering the economizer, and at the same time reduce the thermal load on the condenser. The efficiency of an ORC unit beneficiates from the use of a regenerator whenever the fluid is dry, and it is usually used in ORC systems working with medium to high temperatures, as in this case. The system includes the heat transfer fluid (HTF) loop and the heat sink loop, as this is the case in most of the ORC commercial units in the market. 10

8

9 Evaporator

Economizer

4

5

Expander

3

Generator

Regenerator 6

7

2

Pump

Condenser

1

11

12

Fig. 1. ORC system.

The ORC system model is based on the following assumptions:  Steady-state conditions are assumed in all components.  Heat and frictional losses in the pipes are neglected.  The fluid transferring heat from the heat source is thermal oil Therminol66.  The fluid transferring heat from the ORC to the heat sink is water.  The difference between thermal oil inlet and outlet temperatures is 20 K.  The difference between water outlet and inlet temperatures is 5 K.  The combined thermal power supplied to the economizer and the evaporator is 10 kW, in order to consider micro scale systems.  The state of the working fluid at the evaporator inlet is saturated liquid.  The subcooling of the working fluid at the pump inlet is 5 K.  Counter-flow plate-type heat exchangers are selected as the economizer, evaporator, regenerator and condenser.  A volumetric-type expander is selected, as this type of expander is commonly used in micro and small scale systems.  The expander mechanical efficiency is 70%.  The expansion process is assumed adiabatic.  The pump overall efficiency is 40%, in order to account electromechanical losses.  The pump process is assumed isentropic.

Francisco Molés et al. / Energy Procedia 142 (2017) 1199–1205 Author name / Energy Procedia00 (2017) 000–000

1202 4

The detailed model development and equations can be found in Reference [8]. The main performance parameter is the specific investment cost (SIC), defined as:

SIC 

Cost Wn

(1)

The cost of the ORC system is calculated by means of the cost correlations used in Reference [9]. The heat source and sink inlet temperatures are specified and nine system parameters are optimized with the objective of minimizing the SIC for each selected working fluid: regenerator effectiveness (  ), expander internal

built-in volume ratio ( rv ), superheating of the working fluid at the expander inlet ( SH ), heat exchanger pinch points ( pinchevap ,

pinchcond ) and heat exchanger pressure drops ( Pevap , Pecon , Pcond , Preg ).

3. Results and discussion Table 1 shows the values of the nine optimized variables (  ,

rv , SH , pinchevap , pinchcond , Pevap , Pecon ,

Pcond , Preg ) that minimize the SIC. The four working fluids of interest for the case of an ORC system with a heat source and sink inlet temperatures of 428 K (155ºC), and 298 K (25ºC) are also included. Optimal regenerator effectiveness values are similar to the different working fluids, approximately 80%. The optimal internal built-in volume ratio is higher for HFO-1336mzz-Z compared with HFC-245fa and HCFO-1233zd-E, and lower for HFO1234ze-Z. Optimal superheating at the expander inlet varies between about 15 K and 25 K, depending on the working fluid. The optimal evaporator pinch points vary between about 5 K and 13 K, while the optimal condenser pinch points vary more narrowly between 3.9 K and 4.9 K among the working fluids studied. The optimal evaporator and economizer pressure drops are notably higher than the optimal condenser and regenerator pressure drops. Table 1. Optimal parameters with the different working fluids.



rv

SH

pinchevap

pinchcond

Pevap

Pecon

Pcond

Preg

(%)

(-)

(K)

(K)

(K)

(kPa)

(kPa)

(kPa)

(kPa)

HFC-245fa

82.43

12.73

20.89

9.78

4.07

97.33

31.74

13.03

7.97

HCFO-1233zd-E

78.26

11.74

19.12

7.29

4.60

106.20

32.70

11.62

6.29

HFO-1336mzz-Z

78.55

15.88

15.77

5.07

4.90

88.10

38.79

7.97

5.16

HFO-1234ze-Z

82.09

10.68

23.91

12.41

3.86

90.70

23.68

14.35

7.54

Working fluid

Table 2. Selected performance indicators with the different working fluids. Working fluid

Wexp (kW)

 n (%)

SIC (€/kW)

HFC-245fa

1.52

13.31

2283

HCFO-1233zd-E

1.51

13.37

2276

HFO-1336mzz-Z

1.51

13.77

2243

HFO-1234ze-Z

1.51

13.18

2278



Francisco Molés et al. / Energy Procedia 142 (2017) 1199–1205 Author name / Energy Procedia00 (2017) 000–000

1203 5

Table 2 shows selected performance indicators resulting from the thermo-economic optimization with each of the four working fluids of interest for the case of an ORC system with a heat source and sink inlet temperatures of 428 K (155ºC) and 298 K (25ºC), respectively. The expander electrical power is practically the same for all the working fluids, with values consistent with the available thermal power of 10 kW. However, the power consumed by the pump, consistently with previous work [3], is significantly lower and results in higher net electrical power output and net electrical system efficiency for HCFO-1233zd-E and HFO-1336mzz-Z. The three low GWP working fluids lead to lower SIC values than HFC-245fa; the lowest SIC is achieved for the cycle with HFO-1336mzz-Z as working fluid. Fig. 2 shows the relative cost of the system components for each working fluid. The system cost structure is similar for all the working fluids studied. Heat exchangers, expander and labor cost compute more than half of the total cost of the system. Working fluid and piping contribute only a small fraction of the total system cost.

Fig. 2. Relative component cost with the different working fluids.

Fig. 3 presents the effect of the heat source inlet temperature on the minimum SIC and net electrical system efficiency of ORC system operating with the four fluids of interest at a constant heat sink inlet temperature of 298 K (25ºC). Fig. 4 presents the effect of the heat sink inlet temperature on the minimum SIC and net electrical system efficiency of ORC system operating with the four fluids of interest at a constant heat source inlet temperature of 428 K (155ºC). Increasing the inlet temperature of the heat source results in lower SIC values and higher efficiency values with all the working fluids studied. Increasing the inlet temperature of the heat sink results in higher SIC values and lower efficiency values with the working fluids studied. HFO-1336mzz-Z presents lower SIC and higher efficiency values than the rest of the working fluids throughout the range of operating conditions studied.

(a)

(b)

Fig. 3. Variation of the performance indicators with the heat source inlet temperature.

Francisco Molés et al. / Energy Procedia 142 (2017) 1199–1205 Author name / Energy Procedia00 (2017) 000–000

1204 6

(a)

(b)

Fig. 4. Variation of the performance indicators with the heat sink inlet temperature.

4. Conclusions In the present work, a thermo-economic evaluation of the low GWP fluids HCFO-1233zd-E, HFO-1336mzz-Z and HFO-1234ze-Z as alternatives to HFC-245fa in ORC systems for low temperature heat sources is carried out. A thermodynamic ORC model is extended with the overall cost of the ORC system, determined from the summation of the component costs. It is used to identify ORC system parameter values for each working fluid that minimize the SIC at a given set of the heat source and sink inlet temperatures. The optimized system design parameters and performance indicators are presented. HCFO-1233zd-E and HFO-1336mzz-Z present higher efficiencies than HFC245fa, while HFO-1234ze-Z presents lower efficiency than HFC-245fa. The low GWP working fluids result in lower SIC values than HFC-245fa. HFO-1336mzz-Z presents the lowest SIC and highest efficiency values among the working fluids of interest throughout the range of operating conditions studied. Acknowledgements The authors thankfully acknowledge DuPont Corporation for supporting this work. The authors acknowledge the Spanish Government for the financial support under project ENE2015-70610-R. Dr. Adrián Mota-Babiloni would like to acknowledge the funding received from the Plan for the promotion of research of the University Jaume I for the year 2016 [Grant number POSDOC/2016/23]. References [1] S. Quoilin, M. Van Den Broek, S. Declaye, P. Dewallef, V. Lemort, Techno-economic survey of Organic Rankine Cycle (ORC) systems, Renewable and Sustainable Energy Reviews 22 (2013) 168 – 186. [2] G. Myhre, D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: “Anthropogenic and Natural Radiative Forcing”, In: Climate Change: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [T.F. Stocker, D. Qin, G.K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)], Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. [3] F. Molés, J. Navarro-Esbrí, B. Peris, A. Mota-Babiloni, A. Barragán-Cervera, K. Kontomaris, Low GWP alternatives to HFC-245fa in Organic Rankine Cycles for low temperature heat recovery: HCFO-1233zd-E and HFO-1336mzz-Z, Applied Thermal Engineering 71 (2014) 204 – 212. [4] M. Astolfi, Matteo C. Romano, P. Bombarda, E. Macchi, Binary ORC (Organic Rankine Cycles) power plants for the exploitation of medium – low temperature geothermal sources – Part B: Techno-economic optimization, Energy 66 (2014), 435 – 446. [5] S.A. Klein, Engineering Equation Solver, F-Chart Software, Middleton, WI, 2010. [6] E.W. Lemmon, M.L. Huber, M.O. McLinden, REFPROP, NIST Standard Reference Database 23, v.8, National Institute of Standards, Gaithersburg, MD, USA, 2007. [7] I. Bell, S. Quoilin, J. Wronski, V. Lemort, CoolProp library, www.coolprop.org. [8] F. Molés, Theoretical and experimental analysis of low GWP working fluids as alternatives to HFC-245fa in low temperature organic Rankine cycles, Ph.D. Thesis, University Jaume I, Castellón, Spain, 2015.



Francisco Molés et al. / Energy Procedia 142 (2017) 1199–1205 Author name / Energy Procedia00 (2017) 000–000

1205 7

[9] S. Quoilin, S. Declaye, B.F. Tchanche, V. Lemort, Thermo-economic optimization of waste heat recovery Organic Rankine Cycles, Applied Thermal Engineering 31 (2011), 2885 – 2893.