Exergy performance assessment of direct steam generation with glasshouse enclosed parabolic trough installation used for solar thermal Enhanced Oil Recovery (EOR) application

ABSTRACT

Solar thermal Enhanced Oil Recovery (EOR) is the process of producing heavy oil by means of steam generated using solar energy. The present investigation was carried out on an operating Glasshouse enclosed parabolic trough (GPTC) plant at Sultanate of Oman. Exergy performance aspects were studied in detail for an evaporator loop. The study explored that the overall second law efficiency and exergy destruction are in the range of 34–43% and 57–56%. Exergy received from the sun was in the range of 4580 to 5820 kW. Exergy expended for steam generation inside the receiver tubes varies between 1580 and 2300 kW. The maximum exergy loss due to the glasshouse enclosure was about 420 kW. Similarly, exergy destruction in radiation concentration process was in the range of 1070–1620 kW. Exergy destructions in the receiver tube is found to be the highest followed by exergy destructions due to solar radiation concentration. The exergy factor is observed to be varying between 0.65 and 0.82. This method of exergy analysis of GPTC installations could support to mitigate the design challenges and enhance the opportunities for design improvement and development, and finally helps to reduce capital investment.

KEYWORDS:

• Glasshouse enclosed parabolic trough
• direct steam generation
• exergy performance
• exergy destruction
• irreversibility

Nomenclature

CSP	=	Concentrating Solar Power
DNI	=	Direct Normal Irradiance
DSG	=	Direct Steam Generation
EOR	=	Enhanced Oil Recovery
GPTC	=	Glasshouse enclosed Parabolic Trough Collector
OTSG	=	Once-Through Steam Generator
PLC	=	Programmable Logic Control
PTC	=	Parabolic Trough Collector
SPA	=	Solar Positioning Algorithm

Symbols

$A_{ap}$	=	Aperture area of the collectors, m2
$A_{RT\left(surface\right)}$	=	Surface area of the receiver tube, m2
$c_{ps}$	=	Specific heat of steam at constant pressure, KJ/Kg deg C
$c_w$	=	Specific heat of water, KJ/Kg deg C
d	=	Inside diameter of tube, m
$\frac{d{P}_L}{dZ}$	=	Liquid phase flow pressure gradient, KJ/m
$\frac{d{P}_{TP}}{dZ}$	=	Two phase flow pressure gradient, KJ/m
E	=	Internal Energy, KW
${\dot{E}}_{xu}$	=	Useful exergy, kW
${\dot{E}}_{xe}$	=	Exergy at exit, kW
${\dot{E}}_{xi}$	=	Exergy at inlet, kW
${\dot{E}}_{xS}$	=	Exergy from Sun, kW
${\dot{E}}_{xPTC}$	=	Exergy supplied to PTC, kW
${\dot{E}}_{xRT}$	=	Exergy supplied to receiver tube, kW
$e_x$	=	Specific exergy, kJ/kg
$e_{xi}$	=	Inlet specific exergy, kJ/kg
$e_{xe}$	=	Exit specific exergy, kJ/kg
$E_{xf}$	=	Exergy factor
$f$	=	Focal length, m
h	=	Specific enthalpy, KJ/Kg
$h_g$	=	Specific enthalpy of saturated steam, KJ/Kg
$I_D$	=	Direct Normal Irradiance (W/m2)
$K_{\theta }$	=	Incidence angle modifier, dimensionless
$L$	=	Latent heat of vapourisation of water, KJ/Kg
$L_{RT}$	=	Length of receiver tube, m
${\dot{m}}_e$	=	Exit mass flow rate, Kg/S
${\dot{m}}_i$	=	Inlet mass flow rate, Kg/S
$n$	=	Day of the year
$\dot{Q}$	=	Heat transfer rate, KW
${\dot{Q}}_l$	=	Heat loss flux, KW
${\dot{Q}}_{PTC}$	=	Energy received at the collector, KW
${\dot{Q}}_{RT}$	=	Energy received on the receiver tube, KW
${\dot{Q}}_{RT\left(loss\right)}$	=	Thermal loss in receiver tube, KW
${\dot{Q}}_s$	=	Energy received from sun, KW
${\dot{Q}}_u$	=	Useful energy, KW
$s_{gen}$	=	Entropy generated, kJ/(kg·K)
$T_a$	=	Ambient temperature, degree K
$T_f$	=	Saturation temperature, deg C
$T_{GH}$	=	Transmittance of the glass house, dimensionless
$T_{ref}$	=	Reference temperature, deg C
$T_{RT}$	=	Receiver tube average skin temperature, degree K
$T_s$	=	Superheated steam temperature, Deg C
$T_{sa}$	=	Apparent sun temperature, K
$T_0$	=	Temperature that system being evaluated, K
$v$	=	Velocity of flow, m/S
$\dot{W}$	=	Work transfer rate, KW
$w_a$	=	Aperture width, m
X	=	Martinelli parameter
x	=	Steam quality, dimensionless

Greek letters

$\alpha$	=	Absorbance of the receiver tube, dimensionless
$\gamma$	=	Intercept factor, dimensionless
$\delta$	=	Declination angle, degrees
$\epsilon$	=	Emissivity of the receiver tube surface, dimensionless
${\eta }_I$	=	First law efficiency
${\eta }_s$	=	Ground efficiency of the sun, dimensionless
${\eta }_{IPTC}$	=	First law efficiency of PTC
${\eta }_{IOverall}$	=	Overall first law efficiency
${\eta }_{II}$	=	Second law efficiency
${\eta }_{opt}$	=	Optical efficiency, dimensionless
${\rho }_c$	=	Reflectance of the reflector surface, dimensionless
$\sigma$	=	Stefan Boltzman constant, 5.670373 × 10−8 W/(m2K4)
${\varphi }_L^2$	=	Two phase multiplier, dimensionless
${\rho }_G$	=	Density, gas phase, Kg/m3
${\rho }_L$	=	Density, liquid phase, Kg/m3
${\mu }_L$	=	Dynamic viscosity of water, Pa.S
${\mu }_G$	=	Dynamic viscosity of steam, Pa.S
$\lambda$	=	Darcy’s friction factor
$\phi$	=	Latitude of location
$\theta$	=	Angle of incidence, degrees
${\theta }_z$	=	Zenith angle, degrees
${\mathrm{\varnothing }}_r$	=	Rim angle, degrees
$\omega$	=	Hour angle, degrees

Acknowledgments

Authors would like to thank M/s Glasspoint Solar, Inc. and M/s Petroleum Development Oman LLC for providing access to the data required for the analysis.

Data availability statement

Raw data were generated at Petroleum Development Oman, Miraah Plant, Sultanate of Oman. The data that support the findings of this study are openly available in repository (Ramesh and Chintala, 2021) ‘figshare’ at https://doi.org/10.6084/m9.figshare.13713742

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Ramesh Vakkethummel Kundalamcheery

Ramesh Vakkethummel Kundalamcheery is a post graduate (M Tech) in Quality Management from Birla Institute of Technology and Science (BITS), Pilani, India and  is  a doctoral fellow at University of  Petroleum and Energy Studies (UPES), Dehradun, India. He is a working professional in energy industry and his area of expertise is project management and solar thermal EOR.

V Chintala

Dr. V Chintala is an Associate Professor at National Rail and Transportation Institute (Deemed to be university). He is an expert in the fields of waste to energy  (WTE) conversion technologies, solar thermal energy utilization for WTE. He has completed several R&D projects in solar thermal pyrolysis for production valuable fuels for transportation sector.