AU2021105749A4

AU2021105749A4 - Method for designing and modeling integrated energy system for realizing carbon cycle

Info

Publication number: AU2021105749A4
Application number: AU2021105749A
Authority: AU
Inventors: Tianen Chen; Tao Ding; Yuqi FAN; Ouzhu Han; Yuankang HE; Yan Li; Ruifeng LIU; Chenlu Mu
Original assignee: Northwest Branch Of State Grid Corp Of China; Xian Jiaotong University
Current assignee: Northwest Branch Of State Grid Corp Of China; Xian Jiaotong University
Priority date: 2021-08-18
Filing date: 2021-08-18
Publication date: 2021-10-21
Anticipated expiration: 2029-08-18

Abstract

The invention discloses a comprehensive energy system design and modeling method for realizing carbon cycle, which is suitable for industries with multiple energy requirements and high energy consumption. In the system, renewable energy is used to replace fossil energy to reduce the release of carbon in the formation, biomass energy is used as combustion fuel to realize the reuse of carbon in the biological world, electricity, heat and hydrogen carbon-free energy are used to supply energy for high energy-consuming industries, and carbon capture devices are used to recover carbon produced by human production and seal the formation. According to the proposed carbon cycle integrated energy system, the mathematical modeling methods of energy production module, energy dispatching module, energy storage module and energy consumption module are given. The invention innovatively puts forward the carbon cycle of the comprehensive energy system, promotes the improvement of the energy structure, helps to enhance the awareness of decarbonization and emission reduction of enterprises, and provides a new idea for exploring the future development of the comprehensive energy system.

Description

Method for designing and modeling integrated energy system for realizing

carbon cycle

TECHNICAL FIELD

The invention belongs to the field of comprehensive energy systems, and particularly

relates to a design and modeling method of a comprehensive energy system for realizing

carbon cycle, which is used for providing a new idea for future energy system structural

development and realizing carbon neutralization.

BACKGROUND

Climate change caused by carbon emissions has become a global security issue. The

Greenhouse Gas Bulletin issued by the World Meteorological Organization in 2020

pointed out that the increase of greenhouse gases in the atmosphere has become a long

term trend. In 2019, the global average concentration of carbon dioxide (C0 2 ) reached

410.5 ppm, which is very close to the warning line recognized by the international

scientific community. Therefore, in the context of the energy revolution, accelerating

the emission reduction and decarbonization of the energy system and achieving the

ultimate goal of carbon neutralization have become a hot issue in global research.

In the integrated energy system, both energy producers and energy consumers can help

to reduce carbon emissions. In energy production, the use of renewable energy is an

important way to achieve carbon neutrality. Wind power generation and photovoltaic

power generation do not produce greenhouse gases in the production process. Solid

biomass fuel mainly comes from plants and crop residues in nature, and biogas mainly

comes from feces, municipal solid waste, wastewater, etc. The use of both can realize recycling of resources to recover C02 and improve energy efficiency. In terms of energy consumption, low carbonization of high energy-consuming industries is one of the important means to achieve the goal of double carbon. China's traditional industrial sectors account for about 40% of the total carbon emissions. Therefore, it is of great strategic significance and application value to design a carbon cycle integrated energy system for users in high energy-consuming industries.

SUMMARY

The invention provides a comprehensive energy system design and modeling method

for realizing carbon cycle. First of all, the system design idea is to reduce carbon release

from the energy production side and realize carbon sequestration from the energy

consumption side, so that the integrated energy system can realize high-efficiency and

low-carbon cycle with electricity, heat and hydrogen energy in the operation process.

Secondly, the system modeling method is to establish mathematical models from four

aspects: energy production module, energy dispatching module, energy storage module

and energy consumption module, which is conducive to making the dispatching plan

for the efficient operation of the system.

To achieve the above purpose, the present invention provides the following scheme:

The invention provides a comprehensive energy system design and modeling method

for realizing carbon cycle.

A method for designing and modeling an integrated energy system for realizing carbon

cycle is characterized by comprising the following parts:

1) Design and implement a comprehensive energy system of carbon cycle, which is suitable for industries with multiple energy demands and high energy consumption;

2) According to the designed system, mathematical modeling is carried out from energy

production module, energy dispatching module, energy storage module and energy

consumption module;

3) Further, the design of the carbon cycle integrated energy system includes the

following steps:

301) An integrated energy system for realizing carbon cycle includes an energy

production module, an energy dispatching module, an energy storage module and an

energy consumption module;

302) The energy production module includes a new energy power generation hydrogen

production subsystem, a solid biomass gasification power generation subsystem, and a

biogas reforming hydrogen production subsystem; The energy dispatching module

includes the integration and distribution of electric energy, heat energy and hydrogen,

and also includes injecting the trapped carbon dioxide into the stratum for sealing; The

energy storage module contains flexible storage and release of heat energy and electric

energy. The energy consumption module is an enterprise user with multiple energy

demands and high energy consumption;

303) In the energy production module, renewable energy is used to replace fossil energy

to reduce the release of carbon in the formation, and biomass energy is used as

combustion fuel to realize the reuse of carbon in the biological world; The energy

dispatching module and the energy storage module use electricity, heat and hydrogen

carbon-free energy to supply energy for high energy-consuming industries, thus reducing the carbon emission burden of energy-consuming industries; The carbon capture device recovers the carbon generated by the energy production module and the energy consumption module, and seals the stratum in the energy dispatching module;

304) The energy production module includes a new energy power generation hydrogen

biogas reforming hydrogen production subsystem; The new energy power generation

hydrogen production subsystem uses clean electric energy generated by photovoltaic

fan for hydrogen production equipment by electrolysis of water, and the other part can

be directly output; The solid biomass gasification power generation subsystem gasifies

solid biomass fuel into synthesis gas, and then purifies it into fuel gas, thus realizing

the recycling of carbon dioxide; The biogas reforming hydrogen production subsystem

first separates impurities in biogas to obtain fuel gas mainly composed of methane, then

reforms the fuel gas to produce hydrogen, and at the same time, recovers heat in the

combustion process and outputs it;

305) the energy dispatching module integrates and distributes electric energy, heat

energy and hydrogen; Substation integration and distribution of electric energy need to

meet the real-time balance between supply and demand; The heat exchange station

integrates and distributes heat energy, and needs to meet the real-time balance between

supply and demand without considering the heating network pipeline; Hydrogenation

station integrates and distributes hydrogen, which does not need to meet the real-time

balance between supply and demand;

306) The energy storage module includes electric storage equipment and heat storage equipment, and the electric storage equipment/heat storage equipment releases electric energy/heat energy when the electric energy/heat energy generated by the energy production module is less than the electric energy/heat energy required by the energy consumption module; When the electric energy/heat energy generated by the energy production module is greater than the electric energy/heat energy required by the energy consumption module, the electric energy storage equipment/heat storage equipment absorbs the electric energy/heat energy from the substation/heat exchange station;

307) The types of energy used by the energy consumption module are electric energy,

heat energy and hydrogen, all of which are high-quality carbon-free secondary energy,

thus reducing the utilization of traditional high-carbon energy by the energy

consumption side.

4)Further, the mathematical modeling of the energy production module, the energy

dispatching module, the energy storage module and the energy consumption module in

the system comprises the following steps:

401) In the energy production module, three subsystems need to be modeled separately.

The energy power generation hydrogen production subsystem uses clean electric energy

generated by photovoltaic fan, one part of which is used for hydrogen production

equipment by electrolysis of water, and the other part can be directly output. Power

generation, such as hydrogen production rate, is related to the power consumption of

hydrogen production equipment by electrolysis of water, and hydrogen production rate,

such as, hydrogen production rate range constraints, such as:

',PV + ,,WT ,PWE ,C te T (1)

Qt,C,H 2 =m 7 F RPE t(E T zH 2 FVPWE (2)

0 Qt,C,H 2 Qma tET (3)

T is a set of scheduling time periods; ',v and ',WT is the generating power of

P photovoltaic generator set and fan generator set in t time period; t,PWE is the power

consumption of hydrogen production equipment by electrolysis of water in t time period;

tC P is the generation power of the subsystem in t time period; Q, ,c H is the hydrogen

production rate of the subsystem in t time period; V is the molar volume of gas

7 (22.41/mol); F is Faraday efficiency; ZH2 is the number of electrons transferred per

mole of hydrogen generated in the water electrolysis reaction (2 mol e-/mol H 2 ); F is

Faraday constant (96485 C/mol); PWE is the working voltage of hydrogen production

equipment by electrolysis of water; Qc,H2,max is the maximum hydrogen production

rate.

Solid biomass gasification power generation subsystem gasifies solid biomass fuel into

synthesis gas, and then purifies it into fuel gas, so as to recycle carbon dioxide. The

generation power of this subsystem is related to the consumption rate of biomass fuel,

and the generation power is related to the generation power. The climbing power

constraint and biomass energy consumption rate constraint are respectively related to

the sum of power generation and heat generation, such as:

,M = M2 GECU V tET (4)

H = PHCU tET (5) -1,M -- t,M - Emax,CU 6 0I,-P <AP tT (6)

O<! Vm! <V. tE T (7)

CMCo2 -- mI ,m+ HM)At teT (8) In which: IM and Hm is the electric power and thermal power output by the

subsystem in t time period; tm is the consumption rate of biomas solid fuel of the

subsystem in t time period; 7M2G is the conversion efficiency of solid biomass fuel

into fuel gas; qECU is the power generation efficiency of co-generation devices in this

subsystem; qHCU is the thermal efficiency of the co-generation device in the

subsystem; Im is the combustion calorific value of solid biomass fuel (15MJ/KG);

A- ax,Co is the maximum regulate power of the co-generation device in the subsystem;

VTax,m is the maximum consumption rate of solid biomass fuel; At is time period;

CM,Co2 is the total amount of carbon dioxide captured in the scheduling period; ;m is

the carbon dioxide emission coefficient.

Methane reforming hydrogen production subsystem firstly separates impurities from

methane to obtain fuel gas, and then reforms the fuel gas to produce hydrogen, at the

same time, it can recover heat from combustion process and output it. The hydrogen

production rate and output thermal power of the subsystem are as follows, and the

biogas consumption rate constraint is as follows, and the carbon dioxide emission is as

follows:

PH2Qt,G,H2 =H2CH4V,G tE T (9)

Ht'G ?H7CH4 CH4 ,G tE T (10)

0 F,G G,max tE T (11)

CtG,CO 2 =4GHt,G tE T (12)

Where, Qt,G,H2 is the hydrogen production rate of the subsystem in t time period; V,G is the methane consumption rate of the subsystem in t time period; qCH4 is the efficiency of convert biogas into methane; qH 2 is the efficiency of reforming fuel gas to produce hydrogen; pH2 is the hydrogen density at standard temperature and pressure (0.089kg/m3); Ht,G is the thermal power output by the subsystem in t time period; ACH4 is the calorific value of methane combustion (50MJ/KG); Ct,G,cO 2 is the total amount of carbon dioxide emitted during the scheduling period; 4 G is the carbon dioxide emission coefficient; VG,m is that maximum rate of biogas consumption.

402)In the energy dispatching module, it is necessary to model the integration and

distribution of electric energy, heat energy and hydrogen, and also to model the carbon

dioxide captured by the energy production module and the energy consumption module.

Substation integration and distribution of electric energy needs to meet the real-time

balance of supply and demand, and the constraints are as follows:

't,C +£=-- -- + PMe,P,Deh te T (13)

The heat exchange station integrates and distributes heat energy, and needs to meet the

real-time balance between supply and demand without considering the heating network

pipeline. The constraints are as follows:

HtM + Ht,G = H, + HtC -H h te T (14)

The hydrogen refueling station integrates and distributes hydrogen, which does not

need to meet the real-time balance of supply and demand. The constraints are as follows:

S,I = S,+At(Qt,CH 2+Qt,G,H 2 -A t,L,H 2 te T (15)

0 St, H2 Smax,H 2 te T (16)

0 Qt,C,H2 + Qt,G,H2 QH2,max te T (17)

Carbon dioxide sequestration can inject captured carbon dioxide into underground

cities or seabed. The total amount of captured carbon dioxide is as follows:

CCO 2 =(MCCMG,02+(GCCO2 3 L LCO2 (18)

CLC2 4 LC (,L + Ht,L)At teT (19) Where, PL is the power load of the users of the energy consumption module; PCh

and 13,Deh is the charging power and discharging power of the energy storage station;

H,L is the heat load of energy consumption module users; HtCh and Ht,Dch is the

heat storage power and heat release power of the energy storage station; S, is the total

amount of hydrogen remaining in the hydrogen refueling station during t time period;

Q,L,H2 is the amount of hydrogen required by energy consumption module users in t

time period; Smx,H2 is hydrogen capacity of hydrogen station; QH2,ax is the

maximum amount of hydrogen that can be inject into the hydrogen refueling station in

t time period; CC 2 is the total amount of carbon dioxide captured by the industrial

comprehensive energy system; CL,C2 is the carbon dioxide emissions of energy

consumption module users; (M, G, (L is the carbon dioxide capture rate of users of

solid biomass gasification power generation subsystem, biogas reforming hydrogen

production subsystem and energy consumption module; (L is the carbon dioxide

emission coefficient of energy consumption module users.

403) In the energy storage module, electrical storage equipment and thermal storage

equipment need to be modeled, and the modeling methods of the two equipment are

similar. Here, take electrical energy storage equipment as an example.

The charging and discharging states of electric storage equipment cannot be carried out at the same time. The charging and discharging power constraints are shown as follows:

C "VCht 'Ch,t !ChVCh,t

PmhVDch,t PDh,t Dch Deh,t VteT (20)

LVch,t VDch,t 1

The calculation of the charging energy state in each period is shown as follow:

X,,I = (1-o-)X, +(ChCh,t+ Dch,t+1/qDch)AT (t=... T-1) (21)

XO = i"it (22)

CO x t X m(23)

Where Ch,t and Dch,t respectively represent the charging and discharging power of

the electric storage equipment; both VCht andVDcht are 0-1 variables, indicating its

charging and discharging state, VCh,' is 1 indicates that the electric storage equipment

is charged,vDeh,t is 1 indicates that the electric storage equipment is discharged;

indicates the charged energy state in the t-th period; 0' indicates its power loss rate;

17 ch indicates its charging rate; 7Dch indicates its discharge rate; X indicates its init min max power storage equipment capacity; I , , respectively representing the

percentage of the capacity of the initial, minimum and maximum charge energy states.

404) In the energy consumption module, the main work is to predict the electric energy

demand, heat energy demand and hydrogen demand of energy-consuming users, which

is the boundary condition of the model.

The beneficial effects of the invention are as follows:

(1) The invention designs a comprehensive energy system with strong universality, and

proposes to classify according to energy production module, energy dispatching module, energy storage module and energy consumption module. The model is aimed at the integrated energy system where the users of high energy-consuming enterprises are located, and has important value for popularization.

(2) The design method of the present invention promotes the transformation of energy

from fossil fuel to renewable energy and clean carbon-free secondary energy, the energy

production module is driven by renewable energy, and the energy dispatching module

and energy storage module take clean carbon-free secondary energy as the hub, which

provides feasible reference for future comprehensive energy system planning, design

and optimal dispatching.

(3) Considering the carbon emissions of each module will help enhance the awareness

of decarbonization and emission reduction of enterprises, and lay a solid foundation for

achieving the goal of double carbon.

BRIEF DESCRIPTION OF THE FIGURES

In order to explain the embodiment of the present invention or the technical scheme in

the prior art more clearly, the drawings required in the embodiment will be briefly

introduced below. Obviously, the drawings in the following description are only some

embodiment of the present invention, and for ordinary technicians in the field, other

drawings can be obtained according to these drawings without paying creative labor.

Fig. 1 schematic diagram of integrated energy system for realizing carbon cycle;

Fig. 2 working principle of hydrogen production subsystem by new energy power

generation;

Fig. 3 working principle of solid biomass gasification power generation subsystem;

Fig. 4 working principle of biogas reforming hydrogen production subsystem;

Fig. 5 is the load diagram of electricity, heat and hydrogen in metallurgical plants and

chemical plants;

Fig. 6 shows the output results of fans and photovoltaic panels in the hydrogen

production subsystem of new energy power generation;

Fig. 7 shows the energy operation scheduling results of the designed integrated energy

system on typical working days.

DESCRIPTION OF THE INVENTION

Various exemplary embodiments of the present invention will now be described in

detail, which should not be regarded as a limitation of the present invention, but rather

as a more detailed description of certain aspects, characteristics and embodiments of

the present invention.

It should be understood that the terms described in the present invention are only for

describing specific embodiments, and are not intended to limit the present invention. In

addition, as for the numerical range in the present invention, it should be understood

that every intermediate value between the upper limit and the lower limit of the range

is also specifically disclosed. Intermediate values within any stated value or stated range

and every smaller range between any other stated value or intermediate values within

the stated range are also included in the present invention. The upper and lower limits

of these smaller ranges can be independently included or excluded from the range.

Unless otherwise stated, all technical and scientific terms used herein have the same

meanings as commonly understood by those of ordinary skill in the art to which this invention belongs. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe methods and/or materials related to the documents. In case of conflict with any incorporated documents, the contents of this specification shall prevail.

Without departing from the scope or spirit of the invention, it is obvious to those skilled

in the art that many modifications and changes can be made to the specific embodiments

of the specification of the invention. Other embodiments derived from the description

of the present invention will be apparent to the skilled person. The specification and

examples of this application are only exemplary.

As used herein, "including", "including", "having", "containing", etc. are all open terms,

which means including but not limited to.

Unless otherwise specified, "parts" mentioned in the present invention are calculated

by mass parts.

The invention will be further described in detail with reference to the drawings and

examples.

(I) The system design method

The comprehensive energy system design that can realize carbon cycle is shown in

Figure 1, and users with high energy consumption choose metallurgical plants and

chemical plants. China's traditional industrial sectors account for about 40% of the total

carbon emissions. Among them, the C02 emissions of metallurgical industry and chemical industry account for 40% and 10% of the total C02 emissions, respectively, which are the main C02 emission industries. Each module will be modeled separately below.

(II) Energy production module modeling

The working principle of hydrogen production subsystem by energy generation is

shown in Figure 2. For the energy power generation hydrogen production subsystem,

part of clean electricity is supplied to the hydrogen production equipment, and the other

part of clean electricity is integrated into the power grid, which can be described as

follow:

'I,PV + ,WT ,PWE P,C teT (1)

Hydrogen production rate is related to the power consumption of hydrogen production

equipment by electrolysis of water, which can be described as follow:

QtC,H2 Vm 7F ,PWE tE T (2) ZH 2 FVPWE

Hydrogen production rate range constraint can be described as follow:

0 Q,C,H2 C,H2,ma teT (3)

Where: T is the set of dispatch time period; P,, with 1,,WT is the power of

photovoltaic generator set and wind turbine generator set in t time period; 1,,PWE isthe

power consumption of electrolytic water hydrogen production equipment in t time

period; P c is the generation power of the subsystem in t time period; Q,C,H2 is the

hydrogen production rate of the subsystem in t time period; Vm is the molar volume

77 of gas (22.4 L/mol); F is Faraday efficiency. ZH 2 is the number of electrons

transferred per mole of hydrogen generated in the electrolytic water reaction(2 mol e-/ mol H 2 ); F is Faraday constant (96485 C/mol); VWE is the working voltage of hydrogen production equipment by electrolysis of water; QC,H2,max is the maximum hydrogen production rate.

The working principle of the solid biomass gasification power generation subsystem is

shown in fig. 3, which gasifies solid biomass fuel into syngas and then purifies it into

fuel gas, thus realizing the recycling of carbon dioxide. The generation power of this

subsystem is related to the consumption rate of biomass fuel, and the generation power

is related to the generation power, which are shown as follow:

lm - 7M2GECU4 ,M te T (4)

H - 7HCU ,M te T (5)

The climbing power constraint and biomass energy consumption rate constraint are

shown as follow:

Ift' -P CAP te T (6)

0 Fm V~xm te T (7)

The quality of C02 captured by the Solid biomass gasification power generation

subsystem is related to total output energy, as shown below:

CMC02 = (t,+HM)At (8)

[CT

In which: 'tm and Htm is the electric power and thermal power output by the

subsystem in t time period; K is the consumption rate of biomass solid fuel of the

subsystem in t time period; qM2G is the conversion efficiency of solid biomass fuel

subsystem; qHCU is the thermal efficiency of the co-generation device in the subsystem; A,,, is the combustion calorific value of solid biomass fuel (15MJ/kg);

A-Jax,Co is the maximum regulate power of the co-generation device in the subsystem;

Vax,m is the maximum consumption rate of solid biomass fuel; At is time period;

the carbon dioxide emission coefficient.

The working principle of biogas reforming hydrogen production subsystem is shown in

fig. 4. firstly, impurities in biogas are separated to obtain fuel gas mainly composed of

methane, and then the fuel gas is reformed to produce hydrogen, and at the same time,

the heat in the combustion process can be recovered and output. The hydrogen

production rate and output thermal power of the subsystem are as follows:

PH2Qt,G,H2 =H2CH4V,G tE T (9)

Ht'G 7 7 H CH4 CH4 r,G tE T (10)

The biogas consumption rate constraint is as follows:

0 JFt,G VG,max ET (11)

The carbon dioxide emission is as follows:

CtG,C2 =4GHt,G tE T (12)

Where, Qt,G,H2 is the hydrogen production rate of the subsystem in t time period; V,G

is the methane consumption rate of the subsystem in t time period; qCH4 is the

efficiency of convert biogas into methane; qH2 is the efficiency of reforming fuel gas

to produce hydrogen; pH 2 is the hydrogen density at standard temperature and

pressure (0.089kg/m 3); Ht,G is the thermal power output by the subsystem in t time

period; ACH4 is the calorific value of methane combustion (50MJ/KG); Ct,G,C0 2 is the total amount of carbon dioxide emitted during the scheduling period;G is the carbon dioxide emission coefficient; VG,m is that maximum rate of biogas consumption.

(III) Modeling of Energy Dispatching Module

In the energy dispatching module, it is necessary to model the integration and

balance of supply and demand, and the constraints are as follows:

=P,C+P -- ±P, ±P+ eC -P,Dch +g teT (13)

pipeline. The constraints are as follows:

HI,M+Ht,G =H, +H, +H,,h -H,Dch teET (14)

S,, = S,+At(QtCH 2 +Q,H2 ) - At(QLCH 2+Q,LM,H2 ) tE T (15) O<'S1,<"S~x 0 r S,H2- smax,H2 tET (16)

0 Qt,C,H2 + Q,G,H2 H2, T (17)

cities or seabed. The total amount of captured carbon dioxide is as follows:

CC0 2 -- MCM,CO2+ 3 GC,G,CO2+LM CLMC02+LC CLCCO2 (18)

CLC,CO2 - 4 LCZ (,LC + HLc)At tcT (19)

CLMCO2 = 4 LM (,LM + HLM)At tcT (20)

Where, '" and '''' is the electricity load of chemical plants and metallurgical

P P plants; iCh and t,Dch is the charging power and discharging power of the energy

H H storage station; ',LC and ',LM is the heat load of chemical plants and metallurgical

H H plants; t,Ch and t,Dch is the heat storage power and heat release power of the

energy storage station; Sr is the total amount of hydrogen remaining in the hydrogen

refueling station during t time period; QLC,H2 andtQ,LM,H2 is the amount of hydrogen

SH 2 required by chemical plants and metallurgical plants in t time period; max,H2 is

hydrogen capacity of hydrogen station; H2,max is the maximum amount of hydrogen

that can be inject into the hydrogen refueling station in t time period; CC02 is the total

amount of carbon dioxide captured by the industrial comprehensive energy system; C C LM,CO2 and LC,CO2 is the carbon dioxide emissions of chemical and metallurgical

factories; 5M , 'G LC , 3 LM is the carbon dioxide capture rate of solid biomass

gasification power generation subsystem, biogas reforming hydrogen production

subsystem, chemical plant and metallurgical plant; LC and LM is the carbon dioxide

emission coefficient of chemical plants and metallurgical plants.

(IV) Modeling of Energy Storage Module

In the energy storage module, electrical storage equipment and thermal storage

equipment need to be modeled, and the modeling methods of the two equipment are

similar, here, take electrical energy storage equipment as an example.

The charging and discharging states of electric storage equipment cannot be carried out

at the same time, and the charging and discharging power constraints are shown as follow:

Ch vCh~t P h VCh,t

D h Deh,t Deh,t- Dch Deh,t ET

Vch,t + VDch,tr1 (21)

The calculation of the charging energy state in each period, the charging energy state

constraints in the initial period and other remaining periods are shown as follow:

X,,=(1-o-)X,+(ChCh,t+l- Dch,t+1/qDch)AT (t=... T-1) (22)

XO = co'"'', (23)

Wq % X, <( (24)

Where, Ch,t and Dch,t respectively represent the charging and discharging power of

the electric storage equipment; both VCht and VDch,t are 0-1 variables, indicating its

charging and discharging state, VCht is 1 indicates that the electric storage equipment

is charged,vDCh,t is 1 indicates that the electric storage equipment is discharged;

indicates the charged energy state in the t-th period; 1 indicates its power loss rate;

qCh indicates its charging rate; 17 Dch indicates its discharge rate; X indicates its init min max power storage equipment capacity; 9 , , respectively representing the

(V) Energy consumption module

In the energy consumption module, the main work is to predict the electric energy

demand, heat energy demand and hydrogen demand of energy-consuming users, which

is the boundary condition of the model. Figure 5 shows the predicted electricity, heat

and hydrogen demand of metallurgical and chemical plants, with the same heat load

and electricity load, but different hydrogen load.

(VI) Run target

The integrated energy system designed for simulation verification takes the lowest

operating cost of the integrated energy system as the objective function, which is

expressed as:

min F=F,+F,+F, (25)

F Among them, P is the energy purchase cost of purchasing solid biomass fuel and

biogas for industrial integrated energy system, expressed as:

F=oM ,M + wG VG (26) teT te T

Among them, F, is the operation and maintenance cost of each energy production

subsystem and energy storage station in the industrial integrated energy system,

expressed as:

Fm ,=PcI QC,H2 +C2 I C +PM ,M +PG Qt,G,H2 teT teT teT tr (27) +pS,E ,Ch ,Dch S,H (HtCh + Ht,Dch reT reT

Where, FC is the cost of capturing and sealing carbon dioxide in the industrial

comprehensive energy system, expressed as:

Fc =o-CC 0 2 (28)

Where, 9m and WG is the unit cost of purchasing solid biomass fuel and biogas;

Pci and PC2 is the unit operation and maintenance cost of hydrogen production

subsystem by new energy power generation; PM and PG is the unit operation and

maintenance cost of solid biomass gasification power generation subsystem and biogas

reforming hydrogen production subsystem; PS,E andPS,H is the unit operation and

maintenance cost of electricity storage and heat storage in the energy storage station; is the unit cost for carbon dioxide capture and storage.

(VII) Simulation analysis

The parameters of integrated energy system for realizing carbon cycle are shown in

Table 1. The calculation factors of carbon emissions in chemical plants and

metallurgical plants are 0.5 and 0.6 respectively. The installed capacity of wind turbine

and photovoltaic turbine is 8MW. Total capacity of electric energy storage and thermal

energy storage is 5MW.

Table 1 Comprehensive energy system parameters for realizing carbon cycle

Parameter Value Parameter Value Parameter Value F 0.9 QC,H 2 ,lax 3500 Nm3 /h 5M 0.9 qM 2 G 0.9 Aa,CU 0.5 MW (G 0.9 7ECU 0.5 KI .x,M 4000 kg/h SLM 0.7 77HCU 0.46 CM 0.46 MW/t SLC 0.5 R 0.6 CG 0.16 MW/t Pci 0.2 V/Nm3 qCH 4 0.7 Gma 1000 kg/h PC2 150 Y/MWh 2 0.5 Smnax,H2 80000 Nm 3 PM 150 Y/MWh 20000 H2 QH 2 ,max Nm 3 /h PG 0.3 V/Nm 3

qH 0.8 07 100 4½ PS,E PS,H 50 Y/MWh

In the simulation results, the total operating cost of the industrial integrated energy

system is 97.279 million yuan, of which the energy purchase cost accounts for 8.4%,

the operation and maintenance cost accounts for 79.4%, and the carbon dioxide capture

cost accounts for 12.2%. The results show that the carbon neutral oriented system needs

to spend a lot of money to maintain the system. In addition, the input energy is

renewable energy, which minimizes the proportion of energy purchase cost. Although

the system uses solid biomass energy and biogas to realize carbon recycling, the energy

system needs to minimize the emission of carbon dioxide to the environment, so it is of great significance and value to use carbon capture devices in addition.

The actual power generation of wind turbine and photovoltaic generator is 186.5 MWh,

of which 90.6 MWh is delivered to substation, and the remaining 95.8 MWh is used for

hydrogen production by electrolysis of water. It can be seen from fig. 6 that there is an

obvious phenomenon of abandoning wind and light in the 10th and 11th time periods.

The main reason for this situation is that the maintenance cost of wind turbine and

photovoltaic turbine is high, and the solid biomass gasification power generation

subsystem and biogas reforming hydrogen production subsystem in these two periods

have already met the factory load requirements.

Figure 7 shows the supply and demand of electricity, heat and hydrogen, reflecting the

operation of each subsystem in the industrial integrated energy system. It is worth

noting that the working state of the storage station has nothing to do with time. In this

model, the storage station does not need to return to its initial charging state at the end

of the day. Therefore, the energy storage station can fully and flexibly adjust the

relationship between supply and demand. In addition, it can be seen from figure (c) that

the supply and demand of hydrogen has never been balanced in real time. Because the

heat energy and electric energy generated by the energy production module have a great

correlation with the amount of hydrogen generated. In other words, the supply amounts

of electricity, heat and hydrogen are coupled in each time period. However, there is no

relationship among heating load, electricity load and hydrogen load in chemical and

metallurgical plants. Therefore, the gap between energy production and consumption is

made up by hydrogen refueling stations.

According to the invention, an industrial comprehensive energy system is established

for industries with high energy consumption to promote carbon neutralization.

Especially, the energy production subsystem using wind energy, solar energy, solid

biomass energy and biogas is described by detailed mathematical formulas. A

scheduling model for optimizing the integration and distribution of electricity, heat and

hydrogen is proposed and verified by simulation. The results show two main

conclusions. First of all, the optimal results show that the carbon neutral oriented system

needs a large proportion of funds for maintenance costs. Second, energy storage stations

and hydrogen refueling stations play a vital role in adjusting the matching between

supply and demand.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method for designing and modeling an integrated energy system for realizing

carbon cycle, characterized by comprising the following parts:

1) Design and implement a comprehensive energy system of carbon cycle, which is

suitable for industries with multiple energy demands and high energy consumption;

2) According to the designed system, mathematical modeling is carried out from energy

production module, energy dispatching module, energy storage module and energy

consumption module.

2. The method for designing and modeling an integrated energy system for realizing

carbon cycle according to claim 1, which is characterized in that the design of the

integrated energy system for realizing carbon cycle:

201) An integrated energy system for realizing carbon cycle includes an energy

production module, an energy dispatching module, an energy storage module and an

energy consumption module;

202) The energy production module includes a new energy power generation hydrogen

production subsystem, a solid biomass gasification power generation subsystem, and a

biogas reforming hydrogen production subsystem; The energy dispatching module

includes the integration and distribution of electric energy, heat energy and hydrogen,

and also includes injecting the trapped carbon dioxide into the stratum for sealing; The

energy storage module contains flexible storage and release of heat energy and electric

energy; The energy consumption module is an enterprise user with multiple energy

demands and high energy consumption;

203) In the energy production module, renewable energy is used to replace fossil energy

to reduce the release of carbon in the formation, and biomass energy is used as

combustion fuel to realize the reuse of carbon in the biological world; The energy

dispatching module and the energy storage module use electricity, heat and hydrogen

carbon-free energy to supply energy for high energy-consuming industries, thus

reducing the carbon emission burden of energy-consuming industries; The carbon

capture device recovers the carbon generated by the energy production module and the

energy consumption module, and seals the stratum in the energy dispatching module;

204) The energy production module includes a new energy power generation hydrogen

production subsystem, a solid biomass gasification power generation subsystem, and a

biogas reforming hydrogen production subsystem; The new energy power generation

hydrogen production subsystem uses clean electric energy generated by photovoltaic

fan for hydrogen production equipment by electrolysis of water, and the other part can

be directly output; The solid biomass gasification power generation subsystem gasifies

solid biomass fuel into synthesis gas, and then purifies it into fuel gas, thus realizing

the recycling of carbon dioxide; The biogas reforming hydrogen production subsystem

first separates impurities in biogas to obtain fuel gas mainly composed of methane, then

reforms the fuel gas to produce hydrogen, and at the same time, recovers heat in the

combustion process and outputs it;

205) The energy dispatching module integrates and distributes electric energy, heat

energy and hydrogen; Substation integration and distribution of electric energy need to

meet the real-time balance between supply and demand; The heat exchange station integrates and distributes heat energy, and needs to meet the real-time balance between supply and demand without considering the heating network pipeline; Hydrogenation station integrates and distributes hydrogen, which does not need to meet the real-time balance between supply and demand;

206) The energy storage module includes electric storage equipment and heat storage

equipment, and the electric storage equipment/heat storage equipment releases electric

energy/heat energy when the electric energy/heat energy generated by the energy

production module is less than the electric energy/heat energy required by the energy

consumption module; When the electric energy/heat energy generated by the energy

production module is greater than the electric energy/heat energy required by the energy

consumption module, the electric energy storage equipment/heat storage equipment

absorbs the electric energy/heat energy from the substation/heat exchange station;

207) The types of energy used by the energy consumption module are electric energy,

heat energy and hydrogen, all of which are high-quality carbon-free secondary energy,

thus reducing the utilization of traditional high-carbon energy by the energy

consumption side.

3. The method for designing and modeling an integrated energy system for realizing

carbon cycle according to claim 1, characterized that building mathematical module of

an energy production module, an energy dispatching module, an energy storage module

and an energy consumption module comprises the following steps:

301) In the energy production module, three subsystems need to be modeled separately.

For the energy power generation hydrogen production subsystem, part of clean electricity is supplied to the hydrogen production equipment, and the other part of clean electricity is integrated into the power grid, which can be described as follow:

PI,PV P,WT,rPWE ,C tT(1

Hydrogen production rate is related to the power consumption of hydrogen production

equipment by electrolysis of water, which can be described as follow:

QC,H 2 =m 17F <PWE t(E T (2) ZH 2 FVPWE

Hydrogen production rate range constraint can be described as follow:

0< Qt,C,H2 ,H2,lax te T (3)

Where: T is the set of dispatch time period; Pp with 1,,WT is the power of

photovoltaic generator set and wind turbine generator set in t time period; 1tPWE isthe

power consumption of electrolytic water hydrogen production equipment in t time

period; P, eis the generation power of the subsystem in t time period; Qt,C,H2 is the

hydrogen production rate of the subsystem in t time period; Vm is the molar volume

77 of gas (22.4 L/mol); F is Faraday efficiency. ZH 2 is the number of electrons

transferred per mole of hydrogen generated in the electrolytic water reaction(2 mol e-/

mol H 2 ); F is Faraday constant (96485 C/mol); VPWE is the working voltage of

hydrogen production equipment by electrolysis of water; QC,H2,max is the maximum

hydrogen production rate.

Solid biomass gasification power generation subsystem gasifies solid biomass fuel into

synthesis gas, and then purifies it into fuel gas, so as to recycle carbon dioxide. The

generation power of this subsystem is related to the consumption rate of biomass fuel,

and the generation power is related to the generation power, which are shown as follow: tm - 7M2GECU4 ,M te T (4)

H, - HCu ,M te T (5)

The climbing power constraint and biomass energy consumption rate constraint are

shown as follow:

m P-mx,cU teT (6)

0J <m' .,m te T (7)

The quality of C02 captured by the Solid biomass gasification power generation

subsystem is related to total output energy, as shown below:

CM'Co 2 - mI ,m+ Hm)At (8) teT

In which: and Hm is the electric power and thermal power output by the

subsystem in t time period; tm is the consumption rate of biomass solid fuel of the

subsystem in t time period; qM2G is the conversion efficiency of solid biomass fuel

into fuel gas; qECU is the power generation efficiency of co-generation devices in this

subsystem; qHCU is the thermal efficiency of the co-generation device in the

subsystem; 1M is the combustion calorific value of solid biomass fuel (15MJ/KG);

A-,,cU is the maximum regulate power of the co-generation device in the subsystem;

F,.axm is the maximum consumption rate of solid biomass fuel; At is time period;

CMC02 is the total amount of carbon dioxide captured in the scheduling period; ;m is

the carbon dioxide emission coefficient.

Methane reforming hydrogen production subsystem firstly separates impurities from

methane to obtain fuel gas, and then reforms the fuel gas to produce hydrogen, at the

same time, it can recover heat from combustion process and output it. The hydrogen production rate and output thermal power of the subsystem are as follows:

PH2Qt,G,H2 =H2CH4V,G tE T (9)

Ht'G 7 7 H CH4 CH4 r,G tE T (10)

The biogas consumption rate constraint is as follows:

0 JFt,G G aVG,, ET (11)

The carbon dioxide emission is as follows:

CtG,C2 =4GHt,G tE T (12)

Where, Qt,G,H2 is the hydrogen production rate of the subsystem in t time period; V,G

is the methane consumption rate of the subsystem in t time period; 7CH4 is the

efficiency of convert biogas into methane; qH2 is the efficiency of reforming fuel gas

to produce hydrogen; pH 2 is the hydrogen density at standard temperature and

pressure (0.089kg/m 3); Ht,G is the thermal power out

put by the subsystem in t time period; ACH4 is the calorific value of methane

combustion (50MJ/KG); Ct,G,C02 is the total amount of carbon dioxide emitted during

the scheduling period; (G is the carbon dioxide emission coefficient; VG,m is that

maximum rate of biogas consumption.

302) In the energy dispatching module, it is necessary to model the integration and

distribution of electric energy, heat energy and hydrogen, and also to model the carbon

dioxide captured by the energy production module and the energy consumption module.

Substation integration and distribution of electric energy needs to meet the real-time

balance of supply and demand, and the constraints are as follows:

't,C + =P ±P + e, --P,Deh te T (13)

The heat exchange station integrates and distributes heat energy, and needs to meet the

real-time balance between supply and demand without considering the heating network

pipeline. The constraints are as follows:

HIM + Ht,G = H, + HI, e - Ht,Dh te T (14)

The hydrogen refueling station integrates and distributes hydrogen, which does not

need to meet the real-time balance of supply and demand. The constraints are as follows:

S,I = S,+At(Qt,C,H 2 +Qt,G,H 2 -A t,L,H 2 te T (15)

0 StH 2 Smax,H 2 te T (16)

0O Qt,C,H2 + Qt,G,H2 QH2,ma te T (17)

Carbon dioxide sequestration can inject captured carbon dioxide into underground

cities or seabed. The total amount of captured carbon dioxide is as follows:

CCO 2 =(MCCMG,02+(GCCO2 3 L LCO2 (18)

CLC2 4 LC (,L + Ht,L)At teT (19) Where, PL is the power load of the users of the energy consumption module; PCh

and 13,Deh is the charging power and discharging power of the energy storage station;

H,L is the heat load of energy consumption module users; HtCh and Ht,Dch is the

heat storage power and heat release power of the energy storage station; S, is the total

amount of hydrogen remaining in the hydrogen refueling station during t time period;

Q,L,H2 is the amount of hydrogen required by energy consumption module users in t

time period; Smx,H2 is hydrogen capacity of hydrogen station; QH2,max is the

maximum amount of hydrogen that can be inject into the hydrogen refueling station in

t time period; CCo 2 is the total amount of carbon dioxide captured by the industrial comprehensive energy system; CL,C02 is the carbon dioxide emissions of energy consumption module users; (M G, (L is the carbon dioxide capture rate of users of solid biomass gasification power generation subsystem, biogas reforming hydrogen production subsystem and energy consumption module; (L is the carbon dioxide emission coefficient of energy consumption module users.

303) In the energy storage module, electrical storage equipment and thermal storage

equipment need to be modeled, and the modeling methods of the two equipment are

similar. Here, take electrical energy storage equipment as an example.

The charging and discharging states of electric storage equipment cannot be carried out

at the same time. The charging and discharging power constraints are shown as follows:

PCh vCh,t Ch,t- Ch Ch,t

DhVDeh,t Deh,t- Dch Deh,t tE T (20)

LVch,t VDch,t 1

The calculation of the charging energy state in each period are shown as follow:

X,,1 = (1-o-)X, +±(ChCh,t+l D (t=0... T-1) /h,t+1qDeh)AT (21)

XO = wi""z (22)

ct)' ! x t! X,(23)

Where, Ch' and Deh,t respectively represent the charging and discharging power of

the electric storage equipment; both VCht and vDcht are 0-1 variables, indicating its

charging and discharging state, VCht is 1 indicates that the electric storage equipment

is charged, VDh,t is 1 indicates that the electric storage equipment

is discharged; X X indicates the charged energy state in the t-th period; 07 indicates

its power loss rate; 7Ch indicates its charging rate; 7 Dch indicates its discharge rate; int min max Z indicates its power storage equipment capacity; ) , ) , O respectively representing the percentage of the capacity of the initial, minimum and maximum charge energy states.

304) In the energy consumption module, the main work is to predict the electric energy

demand, heat energy demand and hydrogen demand of energy consuming users, which

is the boundary condition of the model.