Prospects for reducing greenhouse gas emissions in the energy sector of the Russian Federation
Savitenko M. A. Director of the ANO “Center for Research and Scientific Developments in the Field of Energy” Hydrogen Technological Solutions»
Rybakov B. A. Development Director of SC Engineering LLC»
The Paris Climate Agreement was adopted on 12 December 2015 following the 21st Conference of the Framework Convention on Climate Change (UNFCCC) in Paris.
The document was signed by 175 countries, including Russia.
The purpose of the agreement is to “strengthen the implementation” of the UN Framework Convention on Climate Change, in particular, to keep the increase in global average temperature “well below” 2 °C and “make efforts” to limit the increase in temperature to 1.5 °C.
In this article, we want to clarify the main factors that influence global warming, as well as outline ways to reduce the impact of these factors in the energy sector of the Russian Federation.
To conduct the analysis, we will distinguish four factors::
- Water vapor (H2O)
- Carbon dioxide (CO2)
- Nitrogen oxides (NOx)
- Thermal pollution of the atmosphere (TK).
Consider the five main types of power plants that produce electricity:
- Thermal power plants – thermal power plants (burn fossil fuels)
- Nuclear power plants-nuclear power plants
- Hydroelectric power stations
- Wind farms – wind farms
- SES-solar power plants
Table 1 below shows what factors are typical for these types of power plants:
|Factors||TPP||HYDROELECTRIC POWER STATION||NUCLEAR POWER PLANTS||WES||SES|
At hydroelectric power plants, water vapor enters the atmosphere when water in reservoirs evaporates.
At nuclear power plants, water vapor enters the atmosphere when steam from steam turbines condenses in ” wet ” cooling towers.
According to the annual report of the SO UES of Russia, as of 01.01.2021, the installed capacity of power plants located on the territory of the Russian Federation is 245313.25 MW. At the same time, the installed capacity of TPP is 163292.16 MW (66.65%), HPP – 49912.02 MW (20.35%), NPP – 29354.84 MW (11.97%), WPP – 1027.5 MW (0.42%), WPP-1726.72 (0.7%). The share of steam power plants (PSU) in the installed capacity of thermal power plants is 77.92%, combined cycle gas plants (CCGT) – 16.06%, gas turbine plants (GTU) – 5.12%.
The electricity balance in 2019 and 2020 is shown in table 2:
|Units of measurement||Million kW.hours||Million kW.hours|
|HYDROELECTRIC POWER STATION||190295,4||207416,3|
|NUCLEAR POWER PLANTS||208773,3||215682,1|
The average values of the installed capacity utilization factor in % by generation type are shown in Table 3:
|TPP||HYDROELECTRIC POWER STATION||NUCLEAR POWER PLANTS||WES||SES|
The main contribution to the increase in atmospheric temperature is made by thermal power plants, while steam power units, the main equipment of which consists of a boiler unit and a steam turbine unit, burn coal and natural gas. At the same time, if coal – fired power plants emit mainly carbon dioxide into the atmosphere, then natural gas-fired power plants emit carbon dioxide and water vapor. The combustion of 1 kg of methane, which is the main component of natural gas, produces 2.75 kg of carbon dioxide and 2.25 kg of water vapor.
When burning fuel, nitrogen oxides are formed, which are greenhouse gases, and when combined in the atmosphere with water vapor, they fall to the Ground in the form of acid rain.
In addition to greenhouse gases, thermal power plants emit a large amount of thermal energy into the atmosphere, which contributes to the increase in ambient air temperature.
Specific emissions of thermal energy into the atmosphere have a simple relationship with the efficiency of the power plant:
Thermal power / Electrical power = 1 / EFFICIENCY – 1,
that is, the ratio of the thermal power (TM) of the flue gases to the electrical power (EM) is inversely proportional to the electrical efficiency of the installation.
There are higher and lower specific heat of combustion. The highest heat of combustion is equal to the maximum amount of heat released during the complete combustion of the fuel, taking into account the heat spent on the evaporation of the moisture contained in the fuel. Lower gorenje calorific value is less than the value of the highest by the value of the heat of condensation of water vapor, which is formed from the moisture of the fuel and the hydrogen of the organic mass, which turns into water during combustion.
In thermal engineering calculations, the lowest specific heat of combustion is usually used. In this article, the lowest heat of combustion was used to determine the efficiency values.
Table 4 shows the calculations of the specific heat output from the efficiency:
|TM / EM||2,33||1,5||1,0||0,7|
|kJ / kWh||8,9||5,4||3,6||2,5|
The bottom row of this table shows how many kilojoules of thermal energy is released into the atmosphere per kilowatt-hour of energy generated, depending on the efficiency of the installation.
How are carbon dioxide emissions and efficiency related?
The specific mass of carbon dioxide released into the atmosphere during methane combustion is related to the efficiency of the power plant by the following ratio:
MSO2/kW.h = 198 / EFFICIENCY (kg / kW.hour)
Table 5 shows the calculations of specific carbon dioxide (CO2) emissions from methane combustion, depending on the efficiency of the power plant.
|СО2||kg / kWh||660||495||396||330|
From these calculations, it can be seen that the higher the efficiency of the power plant, the lower the values of specific greenhouse gas emissions into the atmosphere.
The specific mass of water vapor released into the atmosphere during methane combustion is related to the efficiency of the power plant by the following ratio:
MN2O/kW.h = 162 / EFFICIENCY (kg / kW.hour)
Table 6 shows the calculations of specific emissions of water vapor (H2O) during methane combustion, depending on the efficiency of the power plant.
|Н2О||kg / kWh||540||405||324||270|
As the efficiency increases, the specific emissions of water vapor into the atmosphere decrease.
The highest heat of methane is 11% higher, lower than its lowest heat of combustion. In power plants that use the condensation of water vapors of flue gases, the highest heat of combustion of the fuel must be used to determine the heat utilization coefficient of the fuel.
It is obvious that one of the ways to reduce the specific emissions of carbon dioxide, water vapor and heat energy into the atmosphere is to increase the efficiency of power plants.
One of the ways to increase the efficiency of gas turbines and combined-cycle gas plants, which is practically not used in the energy sector of the Russian Federation, is heating fuel gas.
In modern gas turbine installations, the fuel gas temperature is allowed to exceed 200°C.
Efficiency of power plants in Russia
At present, the efficiency of modern combined-cycle gas plants exceeds 60%. As part of such installations, H-class gas turbine units are used. The first such installation with a capacity of 850 MW is being designed at the Zainskaya GRES of PJSC Tatenergo.
The average efficiency of thermal power plants in the Russian Federation is about 37%. The maximum efficiency of steam power units built in the USSR is 40%. We are talking about power units with a capacity of 800 MW with supercritical steam parameters.
The efficiency of combined-cycle gas plants (CCGT) depends on the class of gas turbine plants( GTU), so the efficiency of CCGT with GTU E-class is 0.5-0.52, F – class-0.56-0.58, H-class exceeds 0.6 (60%).
The fleet of gas turbine units used at Gazprom’s compressor stations exceeds 3 thousand units. At the same time, the average efficiency of these installations is about 0.3 (30%).
During the operation of the PDM (Power Supply Agreement), energy consumers paid for the construction of combined-cycle gas plants with an efficiency higher than that of steam power plants.
At the first stage of the implementation of the PDM-2, existing steam power units were selected in order to carry out their major repairs, which does not contribute to reducing greenhouse gas emissions into the atmosphere.
Prospects for the production of “green” hydrogen in Russia
One of the ways to reduce carbon dioxide emissions into the atmosphere (decarbonization) is to use hydrogen as a fuel.
Figure 1 shows the dependence of the relative concentration of carbon dioxide on the volume concentration of hydrogen in the fuel gas, which is a mixture of hydrogen and natural gas.
Abroad, the most popular is the so-called “green” hydrogen.
According to the international classification,” green ” hydrogen refers to hydrogen produced by electricity from renewable energy sources.
In developed countries, the production of” green ” hydrogen is planned on the basis of electricity generated by wind power plants at night.
In many European countries and in the United States, the issue of using a gas supply system as a storage tank is being considered. It is considered that the safe volume fraction in the mixture with natural gas should not exceed 5%.
In Russia, the installed capacity of wind power plants at 1.01.2021 is 1027.5 MW, which is 0.42% of the total installed capacity of thermal power plants, hydroelectric power plants, nuclear power plants, wind farms and SES. By 2030, it is planned to put into operation 4.5 thousand MW of wind power plants.
If all this power is used for the production of hydrogen, it is possible to produce about 800 thousand cubic meters of hydrogen per hour.
For comparison, in 2020, Russia produced 700 billion rubles. cubic meters of natural gas. That is, the hourly production of natural gas is about 80,000 thousand cubic meters.
Therefore, if you mix all the hydrogen produced by wind power plants in 2030 with natural gas, its concentration will not exceed 1%.
It should be taken into account that the utilization rate of wind farms in 2020 was below 30%.
It is possible to significantly increase the volume of hydrogen produced by using electricity generated at hydroelectric power plants. This is also convenient due to the presence of large volumes of water at the hydroelectric power station, which is necessary for the production of hydrogen.
RusHydro and the holding company RAO ES of the East, together with the Japanese corporation Kawasaki Heavy Industries, are building a pilot complex for the production of liquefied hydrogen. The plant’s capacity will be 11.3 tons of hydrogen per day.
Hydrogen combustion in gas turbine plants
Foreign manufacturers of gas turbine plants conduct intensive research on the use of methane-hydrogen mixtures as fuel. In accordance with /1/:
The most popular Ansaldo Energia gas turbines are the GT36 H – class and the AE94.3A F-class. The GT36 H-class gas turbine can burn gas with a hydrogen content of up to 50%, and the AE94 gas turbine can burn gas with a hydrogen content of up to 50%.3A F-class up to 25%.
GE’s 384 MW gas turbine 7NA, equipped with a multi-tube combustion system known as DLN2.6e can run on a mixture of natural gas and hydrogen with a volume fraction of hydrogen up to 50%.
The company “OPRA” – the Danish manufacturer of gas turbine engines-has developed a combustion system that allows you to burn 100% of hydrogen.
In 2018, Kawasaki Heavy Industries demonstrated that the 1 MW M1A-17 turbine can burn 100% hydrogen.
Mitsubishi Power has developed a turbine that can run on a mixture consisting of 30% hydrogen and 70% natural gas. Work is underway to increase the proportion of hydrogen to 100%. The Advanced Class JAC gas turbine of the J series allows you to achieve an efficiency of 64% in the combined cycle. For this purpose, Mitsubishi Power develops low-emission multi-claster combustion chambers for operation on 100% hydrogen. The technology is borrowed from rocket technology developed by MHI.
All high-capacity Siemens Energy gas turbine units from SGT5-2000E to SGT5/6-9000HL are capable of operating on a mixture of natural gas and hydrogen with a volume concentration of up to 30%. The SGT600 GTU can operate with a hydrogen concentration of up to 60%. In the near future, this gas turbine will be able to work on a mixture with a hydrogen concentration of 75%. The SGT800 GTU can operate with a hydrogen concentration of up to 50%. In the near future, this gas turbine will be able to work on a mixture with a hydrogen concentration of 75%.
When switching to hydrogen-containing gas in gas turbine installations, it is necessary to take into account that as a result of its combustion, in addition to water vapor and carbon dioxide, nitrogen oxides are formed.
Among the main pollutants of the atmosphere, nitrogen oxides occupy a special place due to their high toxicity. In the gross emission of all toxic substances, they account for 6-8%, but in terms of toxicity, their share is estimated at ~35%.
The most important nitrogen oxides are NO monoxide and NO2 dioxide, which are combined by the common formula NOx.
The reason for the formation of nitrogen oxides is the oxidation of nitrogen in the air in the torch of the burner devices. The Gorenje NOx formation occurs directly in the combustion zone, and is most intense in the zone of the highest flame temperatures.
Experimental studies/ 2 / show that with an increase in the proportion of hydrogen in the fuel gas, the emissions of nitrogen oxides in the exhaust gases of GTU increase.
Figure 1 shows that as the proportion of hydrogen in natural gas increases, carbon dioxide emissions decrease, but water vapor emissions increase.
The specific mass of water vapor released into the atmosphere during the combustion of hydrogen is related to the efficiency of the power plant by the following ratio:
MN2O/kW.h = 270 / EFFICIENCY (kg / kWh).
The higher heat of combustion of hydrogen is 18.37% higher than its lower heat, so it makes sense to condense the water vapor generated during the combustion of hydrogen to increase the share of thermal energy production in the power plant.
The condensation of water vapor will increase the heat utilization rate of the fuel of the power plant, as well as reduce the impact of thermal energy on the environment.
The influence of water vapor on the increase in the temperature of the Earth’s atmosphere
Below are excerpts from the publications of foreign researchers of the influence of water vapor on the climate of our planet:
- Ramanathan & Coakley (1978): “The importance of water vapor in climate regulation is undeniable. It is the dominant greenhouse gas that holds the Earth’s heat more strongly than other substances.”
- Goody & Yung (1989):”Water vapor is the most important greenhouse gas. Carbon dioxide is the second most important greenhouse gas.”
Lindzen (1996): “the Authors found that in the case of clear sky, the contribution of water vapor in the reflection of the long-wave radiation is 75 W/m2, while carbon dioxide – 32 W/m2.”
- Kiehl & Trenberth (1997): “Water vapor is the dominant greenhouse gas, the most important source of infrared opacity in the atmosphere”.
Soden, Jackson, Ramaswamy, Schwarzkopf & Huang (2005):”The dominant role of water vapor as a greenhouse gas has been noticed for a long time.”
- Vardavas & Taylor (2007): “Generally speaking, water vapor is the only atmospheric absorber of infrared radiation.”
- Rick Panpaleo, (2014): “In society, only carbon dioxide is known as a greenhouse gas. In reality, water vapor makes a more significant contribution to the increase in atmospheric temperature.”
- Scientists from the University of Miami Rosenstiel School of Marine and Atmospheric Science have confirmed that water vapor in the troposphere will play an increasing role in climate change in the future.
If this is the case, then along with reducing carbon dioxide emissions into the atmosphere, it is also necessary to control water vapor emissions.
Comprehensive criteria for estimating greenhouse gas emissions
To assess the total impact of greenhouse gases and thermal energy on the increase in atmospheric temperature, the following criterion is proposed:
Cpta = K1 (H2O) + K2 (CO2) + K3 (NOx) + K4 (TE/EM),
K1-coefficient that characterizes the effect of water vapor emissions on the increase in the temperature of the Earth’s atmosphere,
K2-coefficient that characterizes the effect of carbon dioxide emissions on the increase in the temperature of the Earth’s atmosphere,
K3-coefficient characterizing the effect of nitrogen oxide emissions on the increase in the temperature of the Earth’s atmosphere,
K4 is a coefficient that characterizes the effect of thermal energy emissions on the increase in the temperature of the Earth’s atmosphere.
List of literature
- «Turbomachinery International». “Gas turbine innovations, with or without hydrogen”. Rosy Pasquariello. Dec. 4, 2020.
- “Turbines and diesels”. Study of the combustion chamber of gas turbines on the flexibility of fuel and load. September-October 2020.
Andreas Lanz, Annika Lindholm, Daniel Lorstadt-Siemens Energy AB, Finspong, Sweden.
Arman Ahamed Sabah, Haisol Kim, Sven-Inge Moeller, Mttias Richter, Christian Brakmann, Markus Alder-Lund University, Sweden.