Electricity generation in the world and Ukraine: Current status and future developments

Electricity generation is the key factor for advances in industry, agriculture, technology and the level of living. Also, strong power industry with diverse energy sources is very important for country independence. In general, electricity can be generated from: 1) non-renewable energy sources such as coal, natural gas, oil, and nuclear; and 2) renewable energy sources such as hydro, biomass, wind, geothermal, solar, and wave power. However, the major energy sources for electricity generation in the world are: 1) thermal power – primarily using coal (~40%) and secondarily natural gas (~23%); 2) “large” hydro power plants (~17%) and 3) nuclear power from various reactor designs (~11%). The rest of the energy sources for electricity generation is from using oil (~4%) and renewable sources such as biomass, wind, geothermal and solar (~5%), which have just visible impact in selected countries. In addition, energy sources, such as wind and solar, and some others, like tidal and wave-power, are intermittent from depending on Mother Nature. And cannot be used alone for industrial electricity generation. Nuclear power in Ukraine is the most important source of electricity generation in the country. Currently, Ukrainian Nuclear Power Plants (NPPs) generate about 45.5% of the total electricity followed with coal generation ‒ 38%, gas generation 9.6% and the rest is based on renewable sources, mainly on hydro power plants – 5.9%. Nuclear-power industry is based on four NPPs (15 Pressurized Water Reactors (PWRs) including the largest one in Europe ‒ Zaporizhzhya NPP with about 6,000 MWel gross installed capacity. Two of these 15 reactors have been built and put into operation in 70-s, ten in 80-s, one in 90-s and just two in 2004. Therefore, based on an analysis of the world power reactors in terms of their maximum years of operation (currently, the oldest reactors are ~45-year old) several projections have been made for future of the nuclear-power industry in the world and Ukraine. Unfortunately, all these projections are quite pessimistic. There is a possibility that around 2030‒2040 the vast majority of the world reactors and Ukrainian reactors will be shut down, and, in particular, Ukraine can be left without the basic and vital source of electricity generation..


INTRODUCTION
It is well known that electricity generation is the key factor for advances in industry, agriculture, technology and the level of living (for details, see Table 1 and Figure 1) (Handbook, 2016; Pioro and Duffey, 2015; Pioro and Kirillov, 2013a). Also, strong power industry with diverse energy sources is very important for country independence. In general, electricity can be generated from: 1) non-renewable energy sources such as coal, natural gas, oil, and nuclear; and 2) renewable energy sources such as hydro, biomass, wind, geothermal, solar, and wave power. However, as of today the major energy sources for electricity generation in the world (for details, see Figure 1a) are: 1) thermal powerprimarily using coal (~40%) and secondarily -natural gas (~23%); 2) "large" hydro power plants (~17%) and 3) nuclear power from various reactor designs (~11%). The rest of the energy sources for electricity generation is from using oil (~4%) and renewable sources such as biomass, wind, geothermal and solar (~5%), which have just visible impact in selected countries (for details, see Figures 1 and 2; Tables 2 and 3). In addition, energy sources, such as wind and solar, and some others, like tidal and wave-power, are intermittent from depending on Mother Nature (see Figures 3 and 4; for more details, see Handbook, 2016; and Pioro and Duffey, 2015), and cannot be used alone for industrial electricity generation. Population, Millions × 10 6 . ** HDI -Human Development Index by United Nations (UN); HDI is a comparative measure of life expectancy, literacy, education and standards of living for countries worldwide. HDI is calculated by the following formula: HDI= √LEI×EI×II 3 , where LEI -Life Expectancy Index, EI -Education Index, and II -Income Index. It is used to distinguish whether the country is a developed, a developing or an under-developed country, and also to measure the impact of economic policies on quality of life. Countries fall into four broad human-development categories, each of which comprises ~42 countries: 1) Very high -42 countries; 2) high -43; 3) medium -42; and 4) low -42 (Wikipedia, 2016).
It should be noted that the following two parameters are important characteristics of any power plant: 1) overall (gross) or net efficiency 1 of a plant (for details, see Table 4a,b); and 2) Capacity factor 2 of a plant (for details, see Table 5).
Usually, thermal-and nuclear-power plants operate semi-continuously, because of a high capital cost and low operating costs. The relative costs of electrical energy generated by any system are not only dependent on building capital costs and operating expenses, but also dependent on the capacity factor. The higher the capacity factor the better, as generating costs fall proportionally. However, some renewable-energy sources with exception of large hydroelectric power plants can have significantly lower capacity factors compared to those of thermal-and nuclear-power plants (Handbook, 2016;Pioro and Duffey, 2015). Therefore, thermal power plants, NPPs and large hydro power plants are considered as the basis for any electrical grid as concentrated and reliable sources of electricity generation. Also, NPPs have essentially negligible operating emissions of carbon dioxide into atmosphere compared to alternate thermal plants. Due to that this source of energy is considered as the most viable one for electrical generation for the next 50 -100 years (Handbook, 2016; Pioro and Duffey, 2015) (see Tables 6 and 7). 1 Gross efficiency of a unit during a given period of time is the ratio of the gross electrical energy generated by a unit to the energy consumed during the same period by the same unit. The difference between gross and net efficiencies is internal needs for electrical energy of a power plant, which might be not so small (5% or even more). 2 The net capacity factor of a power plant is the ratio of the actual output of a power plant over a period of time (usually, during a year) and its potential output if it had operated at full nameplate capacity the entire time. To calculate the capacity factor, the total amount of energy a plant produced during a period of time should be divided by the amount of energy the plant would have produced at the full capacity. Capacity factors vary significantly depending on the type of a plant.            (Handbook, 2016). Five reactors have been put into operation in 1969, i.e., they operate for more than 46 years. It is clear from this diagram that the Chernobyl NPP accident has tremendous negative impact on the world nuclear-power industry, which lasts for decades. And currently, we have additional negative impact of the Fukushima Daiichi NPP accident. Figure 6 shows possible scenarios of nuclear-power development in the world. In general, in spite of all current advances into nuclear power, modern NPPs have the following deficiencies: 1) Generate radioactive wastes; 2) Have relatively low thermal efficiencies, especially, water-cooled NPPs (up to 1.6 times lower than that for modern advanced thermal power plants; 3) Risk of radiation release during severe accidents; and 4) Production of nuclear fuel is not an environment-friendly process. Therefore, all these deficiencies should be addressed in next generation -Generation IV NPPs (for details, see Table 8.

~40
Interaction between various electricity-generating sources inside one system (electrical grid) can be illustrated based on that in the Province of Ontario 5 (Canada) (Handbook, 2016). Figure 7a shows installed capacity and Figure 7b electricity generation by energy source in Ontario (Canada) in 2012. Figure 7a shows that in Ontario major installed capacities in 2012 were nuclear (34%), gas (26%), hydro (22%), coal (8%), and renewables (mainly wind) (8%). However, the electricity (see Figure 7b) was mainly generated by nuclear (56%), hydro (22%), natural gas (10%), renewables (mainly wind) (5%), and coal (2%). Figure 8a shows power generated by various energy sources in Ontario (Canada) on June 19, 2012 (a peak power on hot summer day, when major air-conditioning was required) and corresponding to that Figure 8b shows capacity factors of these energy sources. Figure 8 shows that electricity that day from midnight till 3.00 in the morning was mainly generated by nuclear, hydro, gas, wind, "other" and coal. After 3.00 in the morning, wind power fell due to Mother Nature, but electricity consumption started to rise. Therefore, "fast-response" gas-fired power plants and, later, hydro and coal-fired power plants plus "other" power plants started to increase electricity generation to compensate for both decreasing in wind power and increasing demand for electricity. After 18.00 in the evening, energy consumption slightly dropped in the province, and at the same time, wind power started to be increased by Mother Nature. Therefore, gas-fired, hydro and "other" power plants decreased energy generation accordingly. After 22.00 o'clock in the evening, energy consumption dropped even more. Therefore, coal-fired power plants with the most emissions decreased abruptly their electricity generation followed by gas-fired and hydro-power plants. However, currently, the Province of Ontario (Canada) has completely eliminated coal-fired power plants from the electrical grid (Handbook, 2016). Some of them were closed, others -converted to natural gas. Figure 9a shows installed capacity, and Figure 9b electricity generation by energy source in the Province of Ontario (Canada) in 2015. Figure 9a shows that in Ontario major installed capacities in 2015 were nuclear (38%), gas (29%), hydro (25%), and renewables (mainly wind) (8%). However, electricity (see Figure 9b) was mainly generated by nuclear (60%), hydro (24%), natural gas (8.7%), and renewables (mainly wind) (4.9%).  Figure 10 shows that electricity that day from midnight till 3.00 in the morning was mainly generated by nuclear, hydro, gas, wind, and biofuel. After 3.00, biofuel power plants increased slightly electricity generation followed by hydro and gas-fired power plants. Also, at the same time, wind-power plants started to generate slightly more electricity due to Mother Nature. However, after 7.00 wind power started to fluctuate and, eventually, decreased quite significantly. After 6.00 in the morning, solar-power plants started to generate some electricity 6 . During a day, hydro, gas-fired and biofuel power plants had variable electricity generation to compensate changes in consumption of electrical energy and variations in generating electricity with wind and solar power plants. After 21.00 in the evening, energy consumption started to drop in the province, and at the same time, wind power increased by Mother Nature. Therefore, gas-fired, hydro and biofuel power plants decreased energy generation accordingly. In both cases, i.e., June 19 of 2012 and June 17 of 2015, NPPs operated at about 100% of installed capacity providing reliable basic power to the grid. These examples show clearly that any grid that includes NPPs and/or renewable-energy sources must also include "fast-response" power plants such as gas-and/or coal-fired and/or large hydro-power plants. This is due not only to diurnal and seasonal peaking of demand, but also the diurnal and seasonal variability of supply. Thus, for any given market, the generating mix and the demand cycles must be matched 24/7/365, independent of what sources are used, and this requires flexible control and an appropriate mix of base-load and peaking plants.
Also, it should be noted here that having a large percent of variable power sources mainly such as wind and solar, and other, i.e., which generating capacity depends on Mother Nature, an electrical grid can collapse due to significant and unpredicted power instabilities! In addition, the following detrimental factors are usually not considered during estimation of variable power-sources costs: 1) costs of fast-response power plants with service crews on site 24/7 as a back-up power and 2) faster amortization / wear of equipment of fast-response plants.

CURRENT AND FUTURE STATUS OF UKRAINIAN POWER INDUSTRY
Ukraine has about 42 million people and is the largest European country by a territory with exception of Russia. Ukraine consumes about 182 TW h/year electrical energy from various sources (mainly from nuclear -~45.5 % and coal -38% (for details, see Figure 2c)) or has about 461 W/Capita (see Table 1 and Figure 1). Due to that Ukraine is currently on the 78 th place by HDI in the world, which is at the lower end of the second group of countries with High HDI (countries from 43 rd and up to 85 th places by HDI).
The Ukrainian nuclear-power industry consists of four NPPs with the total of 15 reactors (see Table 9 and Figure  11). Thermodynamic layout of a VVER-1000 NPP is shown in Figure 12. Major parameters of the Russian-design PWRs -VVERs operated in Ukraine are listed in Table 10 and T-s diagram of the VVER-1000 turbine cycle -in Figure 13.
Analysis of the Ukrainian power industry shows that two of these 15 th reactors have been built and put into operation in 70-s, ten in 80-s, one in 90-s and just two -in 2004. Also, it should be noted current problems of Ukrainian NPPs, which are: 1) lower capacity factors (around 80%) compared to those in other countries (~90%) (Handbook, 2016); 2) uncertainties with nuclear-fuel supply due to political situation; and 3) service and repairs of relatively old reactors.
Based on an analysis of the world power reactors in terms of their maximum years of operation (currently, the oldest reactors are 45-year old Nuclear News, 2016)) several projections have been made for future of the nuclearpower industry in Ukraine (for details, see Figure 14). Unfortunately, all these projections are quite pessimistic.
There is a possibility that around 2030-2035 the vast majority of the Ukrainian reactors will be shut down, and Ukraine can be left without the basic and vital source of electricity generation.   Analysis of the Ukrainian thermal-power industry shows that 8 large thermal power plants have been built in 60s, 9 -in 70s, and 3 in 80s. Due to this, the vast majority of them quite old and not very efficient plants.
Therefore, Ukraine has to move quickly with building new NPPs with modern reactors. Interesting point here is that Ukraine has its own resources of uranium (up to 800 tonnes per year, which is about 30% of the country's requirements) and own resources of Zirconium. In addition, there are ten scientific-research institutes related to nuclear science/engineering, nuclear energy, fuel and waste management. Based on that Ukraine might consider as an option to build CANDU reactors, which operate with natural uranium. Through that Ukraine has a possibility to develop its own closed fuel cycle and to have more independent and diversified nuclear-power industry.
Of course, NPPs require to be supported with fast-response thermal power plants, which will cover peaks and drops in electricity consumption per day. Therefore, Ukraine has to move to modern high-efficiency thermal power plants such as combined-cycle power plants (combination of Brayton gas-turbine cycle (fuel -natural gas or liquefied natural gas; combustion-products parameters at the gas-turbine inlet: T in ≈1650°C) and Rankine steam-turbine cycle (steam parameters at the turbine inlet: T in ≈620°C (T cr =374°C)) with gross thermal efficiencies of up to 62% and/or supercritical-pressure coal-fired power plants (Rankine-cycle steam inlet turbine parameters: P in ≈25-38 MPa (P cr =22.064 MPa), T in ≈540-625°C (T cr =374°C) and T reheat ≈540-625°C) with thermal efficiencies of up to 55% (Handbook, 2016; Pioro and Kirillov, 2013). Also, strong power industry with diverse energy sources is very important for country independence. 2. In general, electricity can be generated from: 1) non-renewable energy sources such as coal, natural gas, oil, and nuclear; and 2) renewable energy sources such as hydro, biomass, wind, geothermal, solar, and wave power. However, the major energy sources for electricity generation in the world are: 1) thermal power -primarily using coal (~40%) and secondarily -natural gas (~23%); 2) "large" hydro power plants (~17%) and 3) nuclear power from various reactor designs (~11%). The rest of the energy sources for electricity generation is from using oil (~4%) and renewable sources such as biomass, wind, geothermal and solar (~5%), which have just visible impact in selected countries. In addition, energy sources, such as wind and solar, and some others, like tidal and wavepower, are intermittent from depending on Mother Nature. And cannot be used alone for industrial electricity generation. 3. Currently, Ukraine covers its needs for electricity through using nuclear, thermal and hydro power plants.
However, nuclear and thermal power plants are quite old and less efficient than modern NPPs and thermal plants. Also, hydro resources almost used completely. 4. Nuclear power in Ukraine is the most important source of electricity generation in the country. Currently, Ukrainian Nuclear Power Plants (NPPs) generate about 45.5% of the total electricity followed with coal generation -38%, gas generation 9.6% and the rest is based on renewable sources, mainly on hydro power plants -5.9%. Nuclear-power industry is based on four NPPs (15 Pressurized Water Reactors (PWRs) including the largest one in Europe -Zaporizhzhya NPP with about 6,000 MW el gross installed capacity. 5. Two of these 15 reactors have been built and put into operation in 70-s, ten in 80-s, one in 90-s and just two in 2004. Therefore, based on an analysis of the world power reactors in terms of their maximum years of operation (currently, the oldest reactors are ~45-year old) several projections have been made for future of the nuclear-power industry in the world and Ukraine. Unfortunately, all these projections are quite pessimistic. There is a possibility that around 2030-2040 the vast majority of the world reactors and Ukrainian reactors will be shut down, and, in particular, Ukraine can be left without the basic and vital source of electricity generation. 6. Therefore, to decrease these negative trends the following measures should be taken: (a) extension of current NPPs terms of operation; (b) building new NPPs with reactors from various nuclear vendors; and (c) building modern high-efficiency thermal power plants.