Coordination of thermal/wind energies in power-to-gas process for cost/pollution abatement considering wind energy recovery

ABSTRACT

This paper utilizes the thermal and wind energies in power to gas (P2G) process. The purpose of the proposed P2G system is to reduce the operating costs and environmental pollutions. The wind energy is used to produce Hydrogen (H₂) via water electrolyzer. The Carbon dioxide (CO₂) of thermal energies is also captured by Carbon Capture and Storage (CCS). The achieved H₂ and CO₂ are combined to make Methane (CH₄) through Methanation reaction. The unit commitment denotes the optimal operation schedule of thermal generating units at each hour. The proposed model also determines the optimal size of wind energy. In the case of any event or outage, the wind energy recovery is studied by application of hybrid battery-capacitor storage system. The achieved CH₄ from wind energy is sold to make profit. The wind speed volatility is included in the model and handled by stochastic programming. The proposed P2G achieves several purposes including optimal wind turbine sizing, uncertainty management, CO₂ decrease and operating cost reduction. It is demonstrated that the Carbon tax can reduce the CO₂ pollutions up to 8%. The high-cost and high-polluting generating systems like oil fired steam turbines are only used at on-peak hours like 17–21. These units produce about 6% of total energy but releases 11% of total CO₂. The optimal capacity of wind generating system is obtained equal to 107 MW and the profit of process is estimated about 2.383 million $ in year.

KEYWORDS:

• Carbon capture and storage
• carbon reduction
• power to gas
• wind energy recovery

Disclosure statement

No potential conflict of interest was reported by the author(s).

Nomenclature

Parameter	=	Description
$C_k^c$	=	Carbon dioxide tax ($/kg)
$C_k^f$	=	Fuel cost ($/MWh)
$c{M}^k$	=	Charged Methane into reservoir (kg)
$d{M}^k$	=	Discharged Methane from reservoir (kg)
$EEN{S}_{\hspace{0.17em}}^h$	=	Expected Energy Not Served (MW/year)
$EEN{S}_{\hspace{0.17em}}^{max}$	=	Maximum permitted EENS (MW/year)
$h,H$	=	Index of time interval, set of time interval
$k,K$	=	Index of machines, set of machines
$i,j,Sb$	=	Index of grid buses, set of grid buses
$K_k^C$	=	Carbon dioxide rate (kg/MWh)
$K_{\hspace{0.17em}}^W$	=	Coefficient of converting electricity to Hydrogen
$L_h^H$	=	Produced Hydrogen (kg)
$L_h^M$	=	Produced Methane (kg)
$M^h$	=	Stored Methane (kg)
$P_{k,h}^T$	=	Total power of generating system (MW)
$P_{k,h}^P$	=	Scheduled power to supply the demand (MW)
$P_{k,h}^R$	=	Reserved power to regulate the frequency (MW)
$P_{k,h}^D$	=	Load demand (MW)
$P_{k,h}^L$	=	Power losses (MW)
${\mathrm{P}}_h^W$	=	Wind power (MW)
$P_k^V$	=	Ramp rate of generator (MW/hour)
$P^{i,j}$	=	Power between two buses (p.u.)
$P_{max}^{i,j}$	=	Capacity of grid line (p.u.)
${P_L}^i,{P_G}^i$	=	Load and generation of bus (p.u.)
${\bar{P}}^T,{\underset{\_}{P}}^T$	=	Maximum and minimum levels of total power (MW)
${\bar{P}}^P,{\underset{\_}{P}}^P$	=	Maximum and minimum levels of scheduled power (MW)
${\bar{P}}^R,{\underset{\_}{P}}^R$	=	Maximum and minimum levels of reserved power (MW)
$R_{k,h}^C$	=	Released Carbon dioxide (kg)
${\bar{R}}_k^{Cd}$	=	Released Carbon dioxide by each generator (kg/day)
${\bar{R}}_{\hspace{0.17em}}^{Cd}$	=	Released Carbon dioxide by network (kg/day)
$rM$	=	Rate of charge and discharge (kg)
$V_b^{min},V_b^{max}$	=	Minimum and maximum voltage limit (p.u.)
$z$	=	Operational cost ($/day)
$Y^{i,j}$	=	Admittance between two grid buses (p.u.)
${\eta }_{ms}$	=	Efficiency of Methane storage system (%)
${\omega }_1,{\omega }_2$	=	Coefficient of Methane formulation
${\mathrm{\Theta }}^i,V_b^i$	=	Angle and magnitude of voltage on grid bus (Rad, p.u.)