Accounting method for carbon emission and carbon emission reduction of medium-deep geothermal system

Abstract

The invention belongs to the technical field of carbon emission accounting, and discloses an accounting method for carbon emission of a medium-deep geothermal thermal system, which comprises the following steps of: defining an accounting boundary based on a life cycle theory, and respectively constructing carbon emission accounting models for the medium-deep geothermal thermal system according to different characteristics of three stages of production, construction and operation of raw materials and equipment; the problems that the carbon emission is reduced only through conversion of consumed electric energy in the operation stage at present, and calculation is inaccurate are solved. The invention further discloses an accounting method for carbon emission reduction of the medium-deep geothermal system, carbon emission reduction measures can be implemented in a targeted manner according to the influence factors and the calculation method of carbon emission in different stages of the full life cycle of the medium-deep geothermal system, so that the carbon emission of the medium-deep geothermal system is further reduced, and the application advantages of the medium-deep geothermal system are expanded.

Description

Technical Field

[0001] This invention belongs to the field of carbon emission accounting technology, and specifically relates to a method for calculating carbon emissions and carbon reduction in medium-deep geothermal systems. Background Technology

[0002] Medium-deep geothermal technology is currently the main technology in the field of geothermal energy development and utilization. It mainly extracts geothermal energy in the range of burial depth of 100-3000m and has the characteristics of "closed heat exchange, heat extraction without water extraction, and no environmental interference".

[0003] A carbon footprint refers to the sum of greenhouse gas emissions and removals directly or indirectly caused by a specific entity over a certain period of time, expressed in carbon dioxide equivalents. The specific entity can be an individual, organization, country, product, etc. Commonly used methods for calculating carbon footprints include the life cycle approach and the input-output approach.

[0004] Currently, the carbon emission calculation in the practical application of medium-deep geothermal technology only calculates the amount of conventional energy substitution during the operation phase and converts it into carbon dioxide emission reduction using the carbon emission factor method. However, it does not calculate the carbon dioxide emissions during the manufacturing and construction phases of products such as coaxial tube heat exchangers and heat pumps used in this technology. Therefore, it cannot accurately reflect the carbon emissions and emission reductions of this technology. Furthermore, there are few patents for carbon emission calculation methods in the application of medium-deep geothermal technology, which cannot accurately guide the calculation of carbon emissions and carbon emission reductions in the practical application of this technology.

[0005] Furthermore, the main raw materials consumed during the construction phase of medium-deep geothermal engineering are bentonite and lubricating oil; the main energy consumed is electricity and diesel; and the equipment that needs to be transported mainly includes towers, drill pipes, mud tanks, bases, and motors. Due to variations in the transportation methods and distances of raw materials and machinery during actual construction, the energy consumed and carbon emissions also differ, and carbon emissions vary for different construction sites, making it difficult to accurately calculate the carbon emissions during the construction process.

[0006] Therefore, there is an urgent need for a simplified calculation method for carbon emissions and carbon reduction in medium-deep geothermal systems. Summary of the Invention

[0007] The purpose of this invention is to provide a method for calculating carbon emissions from medium-deep geothermal systems, characterized by the following steps:

[0008] Based on the life cycle theory, S1 divides the entire life cycle of the medium-deep geothermal system into three stages, obtaining the full life cycle of the medium-deep geothermal system; wherein, the full life cycle of the medium-deep geothermal system includes the equipment and raw material manufacturing stage, the construction stage, and the system operation stage;

[0009] S2 determines the carbon emission accounting boundaries for different stages based on the entire life cycle of the medium-deep geothermal system;

[0010] S3 constructs carbon emission accounting models for different stages based on the accounting boundaries of the medium-deep geothermal system, including carbon emission accounting models for the equipment and raw material manufacturing stage, carbon emission accounting models for the construction stage, and carbon emission accounting models for the system operation stage.

[0011] S4 collects data on the medium-deep geothermal system and uses a carbon emission accounting model for each stage of the entire life cycle to calculate the carbon emission value of the medium-deep geothermal system throughout its entire life cycle.

[0012] As a preferred embodiment, the carbon emission accounting model for the equipment and raw material manufacturing stage is as follows:

[0013]

[0014] In the formula q i Let be the mass (kg) of the i-th material;

[0015] Eq i The carbon emission per unit mass of material i (kgCO2 / kg).

[0016] As a preferred embodiment, the carbon emission accounting model for the construction phase is as follows:

[0017] C2 = C 21 +C 22 +C 23

[0018]

[0019] Where: C 21 Carbon emissions from raw materials consumed during the construction phase;

[0020] C 22 Carbon emissions generated from energy consumption during construction;

[0021] C 23 Carbon emissions generated during preparation processes such as the transfer of mechanical equipment;

[0022] q i Let i be the mass of the i-th type of raw material consumed, in kg;

[0023] E qi Carbon emissions per unit mass during the production of raw material i, kgCO2 / kg

[0024] F ij Carbon emissions per unit distance for raw material i transported by mode j, kgCO2 / km;

[0025] dij Let be the distance (in km) that can be transported using transportation method j for raw material i.

[0026] Q i The amount of type i energy consumed during construction;

[0027] P i The carbon emission factor of the i type of energy consumed during construction;

[0028] X i Let be the total mass of the i-th type of mechanical equipment;

[0029] F ij The carbon emission per unit mass per unit distance for the i-th type of mechanical equipment using the j-th transportation method is expressed as kgCO2 / km / kg.

[0030] d ij Let represent the transportation distance of the i-th type of mechanical equipment using the j-th transportation method.

[0031] As a preferred embodiment, the carbon emission accounting model for the system operation phase is as follows:

[0032]

[0033] Where: C3 represents carbon emissions during the system operation phase;

[0034] Qi represents the amount of energy consumed by the system during its operation phase.

[0035] Pi is the carbon emission factor of the i-th energy source.

[0036] Preferably, the construction phase is divided into the production and transportation of required raw materials, the transportation and assembly preparation of construction machinery and equipment, and the drilling construction phase, and carbon emission models are constructed for each phase, as follows:

[0037] The required raw material production and transportation costs are calculated as follows: y1 = 54.3 * X1 - 13345.50

[0038] The preparation stage for the transportation and assembly of construction machinery and equipment: y2 = 3.55 * X2 + 3248.29

[0039] In the drilling operation phase, y3 = 2.66 * X3

[0040] In the formula: the total amount of raw materials consumed is X1 (kg), the total mass of transportation machinery and equipment is X2 (t), and the total amount of energy consumed in the drilling construction process is X3 (tce) converted to standard coal; the carbon emissions of the raw materials consumed in the production stage are y1, the carbon emissions of the transportation and assembly preparation of construction machinery and equipment are y2, and the total indirect carbon emissions of energy consumption in the drilling construction process are y3.

[0041] Preferably, based on the equipment and materials involved in the medium-deep geothermal energy system, the total mass method is used to simplify the accounting. The carbon emission calculation formula for the equipment and raw material manufacturing stage is as follows:

[0042] C1 = E q合金钢 q 合金钢 +E q高密度聚乙烯 q 高密度聚乙烯 +E q紫铜 q 紫铜 +E q碳素钢 q 碳素钢

[0043] Another objective of this invention is to provide a carbon emission reduction accounting method for medium-deep geothermal systems, employing the aforementioned carbon emission accounting method, as detailed below:

[0044] The amount of conventional energy that can be replaced by medium-deep geothermal systems is:

[0045]

[0046] Where: Qs represents the equivalent amount of standard coal equivalent of replacing conventional energy, (kgce);

[0047] Q represents the heat supply of the medium-deep geothermal system (MJ);

[0048] η is the efficiency of conventional energy heating equipment;

[0049] q is the calorific value of standard coal, taken as 29.307 (MJ / kgce);

[0050] The carbon emissions (C4) from conventional energy sources are:

[0051] C4=Qs*Vco2

[0052] Where: C4 represents carbon emissions from conventional energy sources; kgCO2;

[0053] VCo2 is the carbon emission factor of conventional energy (kgCO2 / kg);

[0054] The reduction in carbon emissions (C5) over the entire life cycle is:

[0055] C5 = C4 - C1 - C2 - C3

[0056] C5 represents the carbon emission reduction over the entire life cycle of a medium-deep geothermal system, expressed in kgCO2.

[0057] The present invention has the following beneficial effects:

[0058] 1. This invention conducts a full life-cycle carbon emission accounting study on medium-deep geothermal systems, defines the accounting boundaries, and constructs carbon emission accounting models according to the different characteristics of the three stages of raw material and equipment production, construction, and operation. This solves the problem of inaccurate calculations caused by only converting the reduction of carbon emissions into the amount of electricity consumed during the operation stage.

[0059] 2. Addressing the challenges of numerous factors influencing carbon emissions during the construction phase of medium-deep geothermal systems, the varying raw material and fuel consumption across different regions and types of geothermal systems, and the complexity of carbon emission statistics, this paper utilizes mathematical tools to process carbon emissions during the construction phase, based on data from completed projects. By fitting a relationship curve, carbon emissions during the construction phase can be predicted. Furthermore, the calculation requires only a single variable, making statistical analysis convenient. This calculation method and prediction curve are particularly suitable for medium-deep geothermal system projects located in Northwest my country, where the transportation distance for raw materials is within 500 kilometers and the transportation distance for construction machinery is within 1000 kilometers.

[0060] 3. Based on the carbon emission influencing factors and calculation methods at different stages in this patent, targeted carbon emission reduction measures can be implemented to further reduce carbon emissions from medium-deep geothermal systems and expand their application advantages. Detailed Implementation

[0061] This invention provides a method for calculating carbon emissions from medium-deep geothermal systems. The method includes steps S1-S4, each of which is detailed below:

[0062] S1. Based on the life cycle theory, the life cycle of medium-deep geothermal energy is divided to obtain the full life cycle of medium-deep geothermal energy; wherein, the full life cycle of medium-deep geothermal energy includes the equipment and raw material manufacturing stage, the construction stage, and the system operation stage.

[0063] S2. Based on the characteristics of different stages of the entire life cycle of the medium-deep geothermal system, determine the carbon emission accounting boundaries of the medium-deep geothermal system.

[0064] During the equipment and raw material manufacturing stage, the accounting boundaries are determined based on the equipment and materials involved in the application of medium-deep geothermal technology.

[0065] During the construction phase, the accounting boundary is determined based on the consumption of raw materials, energy, and transportation of machinery and equipment required for construction.

[0066] During the system operation phase, the accounting boundary is determined based on energy consumption.

[0067] S3. Based on the accounting boundaries of different stages of the medium-deep geothermal system, carbon emission accounting models are constructed respectively, including carbon emission accounting models for the equipment and raw material manufacturing stage, carbon emission accounting models for the construction stage, and carbon emission accounting models for the system operation stage.

[0068] (1) Carbon emission accounting model for the equipment and raw material manufacturing stage, as detailed below:

[0069]

[0070] In the formula: q i Let be the mass (kg) of the i-th material;

[0071] Eqi represents the carbon emission per unit mass of material i (kgCO2 / kg);

[0072] The equipment and materials involved in medium-deep geothermal systems mainly include coaxial tube heat exchangers, heat pump units, and conventional pipelines and valves. The outer shell of the coaxial tube heat exchanger is made of low-alloy high-strength stainless steel, and the inner shell is made of high-density polyethylene; the pipelines are mainly made of ordinary carbon steel. As a specialized piece of equipment in medium-deep geothermal technology, the heat pump unit consists of various components, making it difficult to calculate the carbon footprint of each component individually. Therefore, this invention innovatively adopts the total mass method for calculation. The principle is as follows: the heat pump unit is mainly composed of ordinary carbon steel and copper. By calculating the mass of steel and copper, and the CO2 generated per unit mass of different materials during the manufacturing process, the carbon emissions of the entire heat pump unit manufacturing process can be calculated. This method simplifies the carbon footprint calculation of the heat pump unit and is consistent with the carbon footprint calculation method for coaxial tube heat exchangers, offering excellent convenience and scientific validity.

[0073] Based on the above principles, the formula for calculating carbon emissions during the equipment and raw material manufacturing stage is as follows:

[0074] C1 = E q合金钢 q 合金钢 +E q高密度聚乙烯 q 高密度聚乙烯 +E q紫铜 q 紫铜 +E q碳素钢 q 碳素钢

[0075] (2) Carbon emission accounting model during the construction phase, as detailed below:

[0076] C2 = C 21 +C 22 +C 23

[0077]

[0078] Where: C 21Carbon emissions from consuming raw materials;

[0079] C 22 Carbon emissions generated from energy consumption during construction;

[0080] C 23 Carbon emissions generated during preparation processes such as the transfer of mechanical equipment;

[0081] q i Let i be the mass of the i-th type of raw material consumed, in kg;

[0082] E qi Carbon emissions per unit mass during the production of raw material i, kgCO2 / kg

[0083] F ij Carbon emissions per unit distance for raw material i transported by mode j, kgCO2 / km;

[0084] d ij Let be the distance (in km) that can be transported using transportation method j for raw material i.

[0085] Q i The amount of type i energy consumed during construction;

[0086] P i The carbon emission factor of the i type of energy consumed during construction;

[0087] X i Let be the total mass of the i-th type of mechanical equipment;

[0088] F ij The carbon emission per unit mass per unit distance for the i-th type of mechanical equipment using the j-th transportation method is expressed as kgCO2 / km / kg.

[0089] d ij Let represent the transportation distance of the i-th type of mechanical equipment using the j-th transportation method.

[0090] To accurately express and calculate the carbon emissions of deep geothermal systems during the construction phase, carbon emissions are calculated separately for raw material consumption, energy consumption, and machinery transportation during the construction phase.

[0091] To address the challenge of accurately calculating carbon emissions during construction, this invention compiles and summarizes actual engineering data, processes it using mathematical tools, and employs the least squares method to fit a carbon emission regression curve. This allows for the calculation and prediction of carbon emissions during different construction stages of medium-deep geothermal systems, thereby determining the carbon emission value for that process. The specific method is as follows:

[0092] 1) Based on the above formula, organize the relevant data of the actual project and divide the construction stage into the production and transportation of required raw materials, the transportation and assembly preparation of construction machinery and equipment, and the drilling construction stage. Then, calculate the carbon emissions of each stage, as shown in Table 1-3 below.

[0093] Table 1. Raw material and energy consumption data during the construction phase of Project 1

[0094]

[0095] Table 2. Raw material and energy consumption data during the construction phase of Project 2

[0096]

[0097]

[0098] Table 3. Raw material and energy consumption data during the construction phase of Project 3

[0099]

[0100] All three projects are located in Northwest my country. While the raw materials needed for construction can be sourced within a 500-kilometer radius, the machinery and equipment require transportation from neighboring provinces, with an average transport distance of approximately 1000 kilometers – a pattern consistent with the transportation of most drilling equipment. The drilling depth for the medium-deep geothermal systems is around 2500 meters. Based on actual drilling and sampling analysis, the geological strata, from top to bottom, are mostly fine sandstone, gravelly medium sandstone, and gray mudstone, classifying the drilling difficulty as moderate.

[0101] 2) Based on the actual data of typical engineering projects I, II, and III of different regions and types, the data were sorted and analyzed, and the following conclusions were drawn: ① Since all carbon emissions during the drilling construction stage come from indirect carbon emissions generated by the energy consumed, and the carbon emissions vary depending on the type of energy consumed, the consumption of different types of energy is converted into standard coal equivalent for ease of calculation; ② Carbon emissions during the construction machinery production stage are negligible because construction machinery can be reused, and the carbon emissions during the production stage account for a very small proportion in a single construction operation, so they are not included in the construction stage.

[0102] To facilitate accurate calculation and prediction of carbon emission data for the three stages of construction, let: the total amount of raw materials consumed be X1, the total mass of transportation machinery and equipment be X2, the energy consumed in the drilling stage (converted to standard coal equivalent) be X3, the carbon emissions of raw materials consumed in the production stage be y1, the carbon emissions of construction machinery and equipment during transportation and assembly preparation stage be y2, and the total indirect carbon emissions of energy consumed in the drilling stage be y3.

[0103] Since the carbon emission factor per unit mass of standard coal is a fixed value of 2.66 in the above data, y3 can be directly calculated based on X3. In order to obtain the relationship between X1 and y1, and X2 and y2, and to facilitate the calculation of carbon emissions for other different actual engineering projects at different construction stages, this invention uses the least squares method to perform curve fitting on the relationship between the types and quantities of raw materials consumed in the construction process, the distance and quantity of construction machinery transportation, and carbon emissions, thereby realizing the calculation and prediction of carbon emissions in the production stage of construction raw materials and the transportation and assembly preparation stage of construction machinery and equipment.

[0104] The calculations and relationship curves are shown in the table below:

[0105]

[0106] Therefore, it can be seen that the carbon emissions of medium-deep geothermal systems during the construction phase can be calculated and predicted based on the consumption of raw materials, the total mass of construction machinery and equipment transported, and the energy consumed in drilling. Furthermore, it provides a calculation method and prediction curve for carbon emissions during the construction phase, reducing the difficulty of accurately calculating carbon emissions during the construction phase of medium-deep geothermal systems. Combining this method with other methods can provide guidance for targeted reduction of carbon emissions during the construction process.

[0107] This calculation method and prediction curve are particularly applicable to medium-deep geothermal system projects in Northwest my country, where the required raw material transportation distance is within 500 kilometers and the construction machinery and equipment transportation distance is within 1000 kilometers.

[0108] (3) System operation phase

[0109] Carbon emissions from medium-deep geothermal systems during operation are mainly generated by the electrical energy consumed by heat pumps and circulating pumps.

[0110]

[0111] Where: C3 represents carbon emissions during the system operation phase;

[0112] Qi represents the amount of energy consumed by the system during its operation phase.

[0113] Pi is the carbon emission factor of the i-th energy source.

[0114] S4 collects carbon emission data from the corresponding medium-deep geothermal system and calculates the full life-cycle carbon emission accounting results for the medium-deep geothermal system. Details are as follows:

[0115] C 总 =C1+C2+C3

[0116] To further clarify the advantages and role of medium-deep geothermal systems in carbon emission reduction, this invention also provides a method for calculating carbon emission reduction of medium-deep geothermal systems. The principle is as follows: Although medium-deep geothermal systems generate carbon emissions to varying degrees during the equipment manufacturing, construction, and operation phases, the total carbon emissions of the medium-deep geothermal system throughout its entire life cycle still have a significant advantage compared to the carbon emissions generated by traditional energy consumption. To further explore the carbon emission reduction potential of medium-deep geothermal systems, the carbon emissions from replacing conventional energy by medium-deep geothermal systems are used as a benchmark, and the difference between this and the total carbon emissions of the medium-deep geothermal system throughout its entire life cycle is the carbon emission reduction.

[0117] If a medium-deep geothermal system is used to meet the heating or other heating needs of a certain scale of building, and its heating capacity is Q within a certain period of time, and other conventional energy sources are used to meet the same heating or heating needs, considering that the efficiency of conventional energy heating equipment is η, the amount of conventional energy replaced by the medium-deep geothermal system is calculated as follows:

[0118]

[0119] Where: Qs represents the equivalent amount of standard coal equivalent of replacing conventional energy, (kgce);

[0120] Q represents the heat supply of the medium-deep geothermal system (MJ);

[0121] η is the efficiency of conventional energy heating equipment;

[0122] q is the calorific value of standard coal, taken as 29.307 (MJ / kgce);

[0123] The carbon emissions (C4) from conventional energy sources are:

[0124] C4=Qs*Vco2

[0125] Where: C4 represents carbon emissions from conventional energy sources; kgCO2;

[0126] VCo2 is the carbon emission factor of conventional energy (kgCO2 / kg);

[0127] Based on the carbon emissions from replacing conventional energy sources with medium-deep geothermal systems, the carbon emission reduction (C5) over the entire life cycle of this medium-deep geothermal system is:

[0128] C5 = C4 - C1 - C2 - C3

[0129] C5 represents the carbon emission reduction over the entire life cycle of a medium-deep geothermal system, expressed in kgCO2.

[0130] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calculating carbon emissions from a medium-deep geothermal system, characterized in that, Includes the following steps: Based on the life cycle theory, S1 divides the entire life cycle of the medium-deep geothermal system into three stages, obtaining the full life cycle of the medium-deep geothermal system; wherein, the full life cycle of the medium-deep geothermal system includes the equipment and raw material manufacturing stage, the construction stage, and the system operation stage; S2 determines the carbon emission accounting boundaries for different stages based on the entire life cycle of the medium-deep geothermal system; S3 constructs carbon emission accounting models for different stages based on the accounting boundaries of the medium-deep geothermal system, including carbon emission accounting models for the equipment and raw material manufacturing stage, carbon emission accounting models for the construction stage, and carbon emission accounting models for the system operation stage. S4 collects data on the medium-deep geothermal system and uses a carbon emission accounting model for each stage of the entire life cycle to calculate the carbon emission value of the medium-deep geothermal system throughout its entire life cycle.

2. The method for calculating carbon emissions from medium-deep geothermal systems as described in claim 1, characterized in that, The carbon emission accounting model for the equipment and raw material manufacturing stage is as follows: In the formula: q i Let be the mass (kg) of the i-th material; Eq i The carbon emission per unit mass of material i (kgCO2 / kg).

3. The method for calculating carbon emissions from medium-deep geothermal systems as described in claim 2, characterized in that, The carbon emission accounting model for the construction phase is as follows: C2=C 21 +C 22 +C 23 Where: C 21 Carbon emissions from raw materials consumed during the construction phase; C 22 Carbon emissions generated from energy consumption during construction; C 23 Carbon emissions generated during preparation processes such as the transfer of mechanical equipment; q i Let i be the mass of the i-th type of raw material consumed, in kg; E qi Carbon emissions per unit mass during the production of raw material i, kgCO2 / kg F ij Carbon emissions per unit distance for raw material i transported by mode j, kgCO2 / km; d ij Let be the distance (in km) that can be transported using transportation method j for raw material i. Q i The amount of type i energy consumed during construction; P i The carbon emission factor of the i type of energy consumed during construction; X i Let be the total mass of the i-th type of mechanical equipment; F ij The carbon emission per unit mass per unit distance for the i-th type of mechanical equipment using the j-th transportation method is expressed as kgCO2 / km / kg. d ij Let be the transportation distance of the i-th type of mechanical equipment using the j-th transportation method.

4. The method for calculating carbon emissions from medium-deep geothermal systems as described in claim 3, characterized in that, The carbon emission accounting model for the system operation phase is as follows: Where: C3 represents carbon emissions during the system operation phase; Qi represents the amount of energy consumed by the system during its operation phase. Pi is the carbon emission factor of the i-th energy source.

5. The method for calculating carbon emissions from medium-deep geothermal systems as described in claim 4, characterized in that, The construction phase is divided into three stages: raw material production and transportation, construction machinery and equipment transportation and assembly preparation, and drilling construction. Carbon emission models are constructed for each stage, as detailed below: The required raw material production and transportation costs are calculated as follows: y1 = 54.3 * X1 - 13345.50 The preparation stage for the transportation and assembly of construction machinery and equipment: y2 = 3.55 * X2 + 3248.29 In the drilling operation phase, y3 = 2.66 * X3 In the formula: the total amount of raw materials consumed is X1 (kg), the total mass of transportation machinery and equipment is X2 (t), and the total amount of energy consumed in the drilling construction process is X3 (tce) converted to standard coal; the carbon emissions of the raw materials consumed in the production stage are y1, the carbon emissions of the transportation and assembly preparation of construction machinery and equipment are y2, and the total indirect carbon emissions of energy consumption in the drilling construction process are y3.

6. The method for calculating carbon emissions from medium-deep geothermal systems as described in claim 4, characterized in that, Based on the equipment and materials involved in the medium-deep geothermal energy system, a simplified accounting method using the total mass method is adopted. The carbon emission calculation formula for the equipment and raw material manufacturing stage is as follows: C1=E q合金钢 q 合金钢 +E q高密度聚乙烯 q 高密度聚乙烯 +E q紫铜 q 紫铜 +E q碳素钢 q 碳素钢。 7. A method for carbon emission reduction accounting of a medium-deep geothermal system, employing the carbon emission accounting method described in claim 5, characterized in that, The amount of conventional energy that can be replaced by medium-deep geothermal systems is: Where: Qs represents the equivalent amount of standard coal equivalent of replacing conventional energy, (kgce); Q represents the heat supply of the medium-deep geothermal system (MJ); η is the efficiency of conventional energy heating equipment; q is the calorific value of standard coal, taken as 29.307 (MJ / kgce); The carbon emissions (C4) from conventional energy sources are: C4=Qs*Vco2 Where: C4 represents carbon emissions from conventional energy sources; kgCO2; VCo2 is the carbon emission factor of conventional energy (kgCO2 / kg); The reduction in carbon emissions (C5) over the entire life cycle is: C5 = C4 - C1 - C2 - C3 C5 represents the carbon emission reduction over the entire life cycle of a medium-deep geothermal system, expressed in kgCO2.

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