The Importance of Heat Emission Caused by Global Energy Production in Terms of Climate Impact

energies

Article The Importance of Heat Emission Caused by Global Energy Production in Terms of Climate Impact

Anna Manowska * and Andrzej Nowrot Department of Electrical Engineering and Automation in Industry, Faculty of Mining, Safety Engineering and Industrial Automation, Silesian University of Technology, Akademicka 2, 44-100 Gliwice, Poland * Correspondence: [email protected]

Received: 20 June 2019; Accepted: 6 August 2019; Published: 9 August 2019

Abstract: The global warming phenomenon is commonly associated with the emission of greenhouse gases. However, there may be other factors related to industry and global energy production which cause climate change—for example, heat emission caused by the production of any useful form of energy. This paper discussed the importance of heat emission—the final result of various forms of energy produced by our civilization. Does the emission also influence the climate warming process, i.e., the well-known greenhouse effect? To answer this question, the global heat production was compared to total solar energy, which reaches the Earth. The paper also analyzed the current global energy market. It shows how much energy is produced and consumed, as well as the directions for further development of the energy market. These analyses made it possible to verify the assumed hypothesis.

Keywords: global heat production; energy market; energy conversion; electricity

1. Introduction Our daily life on Earth requires the production of large amounts of energy. The energy is produced mainly in the forms of electrical energy and mechanical energy as a result of liquid fuels and gases combustion in engines in various types of vehicles. Unfortunately, the various types of useful energy also cause the production of a huge amount of heat. Moreover, these useful energies are eventually converted to heat energy in machines, vehicles, and devices. An important question arises here—whether this release of a large amount of thermal energy is comparable to solar energy and can it significantly affect the global temperature and climate change. In this paper, the thesis was verified whether the heat emission, which is the final result of energy generated by our civilization, has an effect comparable to that of greenhouse warming. The greenhouse effect is well known and is comprehensively presented in many papers—among others [1–4]. However, the effect and greenhouse gas emission have not been discussed in the presented work so far. Nuclear and fossil fuel power plants are thermal power stations and have a maximum efficiency of around 40%. It means that during the production of electrical energy, around 60% of nuclear or chemical energy in fossil fuel is converted to heat energy and is emitted directly into the atmosphere and water (seas, lakes, rivers). Thus, most of the energy contained in any fuel is lost, but there is currently no technically more efficient way to generate electricity. Unfortunately, that also applies to the combustion of biofuels. Wind and water power plants have much higher energy efficiency, and the production of electricity is accompanied by a low heat emission. Much more information about the energy conversion efficiency in thermal power stations is presented in the papers [5–7]. However, regardless of the way how electricity is produced, almost all electricity is ultimately turned into heat. It may seem surprising, but the following analysis proves this thesis. Electrical energy is distributed to different electricity consumers—factories, buildings, hospitals, railway electrification

Energies 2019, 12, 3069; doi:10.3390/en12163069 www.mdpi.com/journal/energies Energies 2019, 12, x FOR PEER REVIEW 2 of 13 Energies 2019, 12, 3069 2 of 12 energy is distributed to different electricity consumers—factories, buildings, hospitals, railway electrification systems, etc. For example, any computer consumes electrical power and uses it to systems,perform etc. calculations, For example, which any computeris accompanied consumes by electrical heat production power and in uses semiconductor it to perform calculations,components which(microprocessors, is accompanied transistors, by heat production diodes, resistors). in semiconductor In practice, components considering (microprocessors, the field of physics, transistors, all the diodes,electric resistors). power in Inany practice, computer considering is finally the converted field of physics, to heat. all In the a fridge, electric an power electric in any motor computer drives is a finallyheat pump, converted which to pumps heat. In out a fridge,heat from an electricinside the motor fridge drives to the a heat outside. pump, According which pumps to the outprinciple heat fromof energy inside conservation, the fridge to the the heat outside. energy According released tointo the the principle atmosphere of energy (outside) conservation, is equal to the the heat sum energyof heat released energy intocollected the atmosphere from the (outside)fridge interior is equal and to thethe sumconsumed of heat electricity. energy collected A very from similar the fridgesituation interior occurs and in the any consumed device. While electricity. an electrical A very similartrain moves, situation electric occurs motors in any cause device. acceleration While an electricaldriving at train a constant moves, velocity electric and motors partial cause energy acceleration recovery driving during atbraking. a constant When velocity the velocity and partial of the energyvehicle recoveryis constant, during all the braking. consumed When electrical the velocity energy of compensates the vehicle is the constant, work of all friction the consumed forces in electricalmechanical energy components compensates (in thebearings, work of frictionetc.) and forces of inair mechanical resistance componentsforces. The (in friction bearings, in etc.)the andcomponents of air resistance causes their forces. heating, The friction and air in resistance the components causes the causes heating their of heating, the train’s and surface air resistance and air. causesThe same the heatingsituation of theoccurs train’s in cars. surface In anda modern air. The pe sametrol situationengine, the occurs chemical in cars. energy In a modern in the petrolfuel is engine,converted the chemicalto heat (about energy 60%) in the and fuel useful is converted mechanical to heat energy (about (about 60%) 40%). and useful All mechanical mechanical energy energy is (aboutused to 40%). compensate All mechanical friction energy forces isand used air to resist compensateance, so frictionalways forcesa heat and is produced. air resistance, Thousands so always of avarious heat is produced.devices and Thousands machines of can various be considered devices and in machines which the can energy be considered would finally in which be the converted energy wouldinto heat—similar finally be converted to what intoit is shown heat—similar in Figure to what1. it is shown in Figure1.

Figure 1. Electrical energy changes into other forms of energy and makes useful work, but almost 100% Figure 1. Electrical energy changes into other forms of energy and makes useful work, but almost is ﬁnally converted to heat energy (own study). 100% is finally converted to heat energy (own study). Consequently, sooner or later, almost 100% of electrical energy or chemical energy in fuels is ﬁnallyConsequently, converted to heatsooner energy. or later, To determine almost 100% the globalof electrical heat production, energy or chemical it is necessary energy to in calculate fuels is thefinally global converted production to ofheat electricity energy. and To petrol determine fuels. the global heat production, it is necessary to calculate the global production of electricity and petrol fuels. Energies 2019, 12, 3069 3 of 12

Energies 2019, 12, x FOR PEER REVIEW 3 of 13 2. Energy Market 2. Energy Market The right energy structure and the increase in energy efficiency are the key issues on the way to theThe transformation right energy structure in the field and of the energy, increase which in isen toergy ensure efficiency a safe futureare the for key all issues [8–11]. on The the current way way to the transformation in the field of energy, which is to ensure a safe future for all [8–11]. The of generating energy is associated with high greenhouse gas emissions because it is based mainly on current way of generating energy is associated with high greenhouse gas emissions because it is fossil fuels and the inefficient use of traditional bioenergy, especially in developing countries [12–16]. based mainly on fossil fuels and the inefficient use of traditional bioenergy, especially in developing Besides, the world’s demand for energy is growing, which is largely due to the economic growth that countries [12–16]. Besides, the world's demand for energy is growing, which is largely due to the drives global energy consumption. Rapid growth occurs in developing countries, such as China and economic growth that drives global energy consumption. Rapid growth occurs in developing India, while in countries belonging to the OECD (The Organisation for Economic Co-operation and countries, such as China and India, while in countries belonging to the OECD (The Organisation for Development), for example, Germany or Italy, energy consumption is beginning to stabilize but is still Economic Co-operation and Development), for example, Germany or Italy, energy consumption is at a high level. These tendencies are in line with the assumptions of the Singer report [17], and this beginning to stabilize but is still at a high level. These tendencies are in line with the assumptions of can also be confirmed by analyzing current trends, both in consumption and in energy production, as the Singer report [17], and this can also be confirmed by analyzing current trends, both in shown in Figure2. consumption and in energy production, as shown in Figure 2.

FigureFigure 2. Total 2. Total energy energy consumption consumption and production, and production, source: source: own elaboration own elaboration based basedon data on [18]. data [18].

Let Letus usfirst ﬁrst take take a alook look at howhow global global energy energy production production has has changed changed from from a long-term a long-term perspective, perspective,both in terms both in of terms quantity of quantity and sources and (Figuresources3 (Figure). 3). Energies 2019, 12, 3069 4 of 12 Energies 2019, 12, x FOR PEER REVIEW 4 of 13

FigureFigure 3. 3.Global Global primary primary energy energy consumption consumption 1800–2017 1800–2017 [ 19[19].].

InIn the the 1800s, 1800s, almost almost all ofall theof world’sthe world's energy energy was produced was produced by burning by burning wood and wood other and organic other matterorganic [19 matter]. Oil consumption[19]. Oil consumption started in started the 1870s in [19the]. 1870s Twenty [19]. years Twenty later, thereyears werelater, natural there were gas andnatural hydroelectricity gas and hydroelectricity in the energy mix.in the Since energy 1900, mi coalx. consumptionSince 1900, coal has increasedconsumption significantly, has increased and, now,significantly, it constitutes and, almost now, it half constitutes of the world’s almost energy half of [19 the]. Inworld's the 20th energy century, [19]. the In energythe 20th mix century, changed the significantly,energy mix coalchanged took oversignificantly, traditional coal biofuels, took over and oiltraditional constituted biofuels, up to aroundand oil 20%constituted of the energy up to market,around and20% since of the 1960, energy the market, world has and had since nuclear 1960, electricitythe world [has18]. had Today, nuclear on the electricity energy market,[18]. Today, we haveon the renewable energy market, energy sources—RES,we have renewable not appearing energy sources—RES, until the 1980–1990s not appearing [19]. until the 1980–1990s [19].Besides, apart from analyzing the total consumption of primary energy, we could also compare the contributionBesides, apart of di fromfferent analyzing energy sources. the total As consumption shown in Figure of primary4, changes energy, in the we energy could mix also are compare slow, so,the mainly, contribution fossil fuels of different dominate energy [19]. Exceptsources. for As the shown emergence in Figure of nuclear 4, changes electricity, in the theenergy energy mix mix are wasslow, fairly so, stablemainly, for fossil at least fuels fifty dominate years [18]. [19]. Except for the emergence of nuclear electricity, the energyChanges mix was in the fairly structure stable offor the at least energy fifty mix years began [18]. after 1997 [20,21] when the first EU regulations on energyChanges from renewablein the structure sources of appeared the energy [22–25 mix]. They began were after stated 1997 in the[20,21] European when Commission’s the first EU Whiteregulations Paper on Energy energy for from the Future—Renewable renewable sources appear Energyed Sources [22–25]. RES They (December were stated 1997). in the In 2001,European the EuropeanCommission's Parliament White andPaper the CouncilEnergy for adopted the Future—Renewable Directive 2001/77/EC Energy on the Sources promotion RES of electricity(December production1997). In 2001, from the RES European on the internal Parliament market, and which the determinedCouncil adopted the share Directive of RES 2001/77/EC in total electricity on the consumptionpromotion of by electricity 2010 (replaced production by Directive from RES 28 /on2009 th/eIN). internal A breakthrough market, which in the determined development the share of RES of tookRES placein total in Marchelectricity 2006, consumption after the publication by 2010 (replaced of the Green by BookDirective [26]. 28/2009/IN). A breakthrough in the development of RES took place in March 2006, after the publication of the Green Book [26]. Energies 2019, 12, 3069 5 of 12

Energies 2019, 12, x FOR PEER REVIEW 5 of 13 Energies 2019, 12, x FOR PEER REVIEW 5 of 13

FigureFigure 4. 4.Primary Primary energy energy consumptionconsumption by by source, source, European European Union Union [19]. [19 ]. Figure 4. Primary energy consumption by source, European Union [19]. FigureFigure5 shows 5 shows primary primary energy energy consumption consumption fromfrom 1965–2017 in in continental continental regions regions [19]. [19 ]. Figure 5 shows primary energy consumption from 1965–2017 in continental regions [19].

Figure 5. Global energy consumption by region [19]. FigureFigure 5. 5.Global Global energyenergy consumption by by region region [19]. [19 ]. In 1965, most of the total energy was consumed in North America, Europe, and Eurasia. In total,In 1965,In they 1965, mostaccounted most of theof for the total over total energy 80% energy of was global was consumed enerconsumedgy consumption. in Northin North America, America,Consumption Europe, Europe, in andother and Eurasia. partsEurasia. of Inthe In total, theytotal, accounted they accounted for over for 80% over of global80% of energyglobal ener consumption.gy consumption. Consumption Consumption in other in other parts parts of theof the world has been increasing, most dramatically in the Asia Pacific. In 2015, Asia Pacific was by far the largest Energies 2019, 12, x FOR PEER REVIEW 6 of 13 Energies 2019, 12, 3069 6 of 12 world has been increasing, most dramatically in the Asia Pacific. In 2015, Asia Pacific was by far the largest regional consumer. The total consumption (about 43%) was the same as in North America, regional consumer. The total consumption (about 43%) was the same as in North America, Europe, Europe, and Eurasia combined [19]. The Middle East used 7%, Latin America 5%, and Africa 3% and Eurasia combined [19]. The Middle East used 7%, Latin America 5%, and Africa 3% [18,19]. [18,19]. In 2017, the production of energy from coal increased due to China. Higher energy prices in the In 2017, the production of energy from coal increased due to China. Higher energy prices in world had caused a drop in oil and gas production in the United States. Energy production in the the world had caused a drop in oil and gas production in the United States. Energy production in European Union decreased due to moderate growth in energy consumption, lower primary energy the European Union decreased due to moderate growth in energy consumption, lower primary production (nuclear and hydro), depletion of oil and gas resources, and climate policy, which ultimately energy production (nuclear and hydro), depletion of oil and gas resources, and climate policy, means giving up coal. Large oil and gas exporting countries, such as Russia, Iran after international which ultimately means giving up coal. Large oil and gas exporting countries, such as Russia, Iran sanctions, Canada or Nigeria, as well as fast-developing countries (India, Indonesia, Turkey, and after international sanctions, Canada or Nigeria, as well as fast-developing countries (India, Brazil), were the main energy donors. In 2017, total consumption was at 567 EJ (EJ = exajoule = 1018 Indonesia, Turkey, and Brazil), were the main energy donors. In 2017, total consumption was at 567 joules), and it is forecast that by 2020, there would be a 10% increase [19]. EJ (EJ = exajoule = 1018 joules), and it is forecast that by 2020, there would be a 10% increase [19]. Prices can have a big impact on the choice of energy sources. While comparing costs between Prices can have a big impact on the choice of energy sources. While comparing costs between sources, it is important to have relative prices [19]. In the literature, the levelized cost of electricity sources, it is important to have relative prices [19]. In the literature, the levelized cost of electricity (LCOE) is used [27]. The concept of LCOE is defined in the following way: (LCOE) is used [27]. The concept of LCOE is defined in the following way: it measures the cost of living divided by energy production, • • it measures the cost of living divided by energy production, • it calculates the current value of the total cost of construction and operation of the plant during • it calculates the current value of the total cost of construction and operation of the plant during thethe assumed assumed period period of of use, use, • it allows comparison of different technologies (e.g., wind, solar, natural gas) with uneven life span, • it allows comparison of different technologies (e.g., wind, solar, natural gas) with uneven life projectspan, size,project diff size,erent different capital costs, capital risk, costs, return, risk, and return, capacity and capacity [27]. [27]. FigureFigure6 shows6 shows the the levelized levelized cost cost of of electricity electricit (LCOE).y (LCOE). The The cost cost range range is representedis represented on on the the columncolumn chart chart for for each each technology. technology. The The white white line line in in each each of of them them represents represents the the global global cost cost of of each each technology.technology. The The average average range range of of fossil fossil fuel fuel costs costs is is shown shown as as a graya gray column. column. In In this this chart, chart, it it is is shownshown that, that, in in 2016, 2016, most most renewable renewable technologies technologies were were in in a competitivea competitive range range to to fossil fossil fuels. fuels. The The keykey exception exception was was the the thermal thermal solar solar radiation, radiation, which which remained remained about about twice twice as as expensive, expensive, but but began began toto decrease decrease [19 [19].]. Hydropower Hydropower is is the the oldest oldest renewable renewable source. source. InIn this this technology, technology, the the price price is is low. low. AnalyzingAnalyzing how how the the average average cost cost of technologyof technology changed changed in the in yearsthe years 2010–2016, 2010–2016, we can we see can that see the that cost the ofcost solar of photovoltaic solar photovoltaic system droppedsystem dropped significantly significan [19]. Thistly [19]. reduction This reduction of cost in photovoltaicof cost in photovoltaic cells has beencells deep has overbeen the deep past over few decades.the past Thefew pricedecades. of solar The photovoltaic price of solar modules photovoltaic has decreased modules more has thandecreased 100 times more since than 1976 100 [19 times]. since 1976 [19].

FigureFigure 6. 6.Levelized Levelized cost cost of of electricity electricity (LCOE) (LCOE) in in 2010 2010 and and 2016 2016 [19 [19].]. Energies 2019, 12, x FOR PEER REVIEW 7 of 13 Energies 2019, 12, 3069 7 of 12 Measuring the number of people with electricity access is a very important social and economic indicator. We think that the growth of population has caused an increase in energy consumption.Measuring theFigure number 7 shows of people that the with percentage electricity of access people is awith very access important to electricity social and has economic increased indicator.at a global We level think [19]. that the growth of population has caused an increase in energy consumption. Figure7 shows that the percentage of people with access to electricity has increased at a global level [ 19].

Figure 7. Share of the population with access to electricity [19]. Figure 7. Share of the population with access to electricity [19]. In 1990, about 73% of the population had access to electricity, and this level increased to 85% in In 1990, about 73% of the population had access to electricity, and this level increased to 85% in 2014 [19]. High-income countries typically have access between 95–100% [19]. The growing global 2014 [19]. High-income countries typically have access between 95–100% [19]. The growing global share was, therefore, driven by increased access in low- and middle-income economies. In many share was, therefore, driven by increased access in low- and middle-income economies. In many countries, this trend has developed, for example, access in India has increased from 45% to 80%, and in countries, this trend has developed, for example, access in India has increased from 45% to 80%, Indonesia, it has increased to 97% from 60% in 1990 [19]. While the trend is upward for most countries, and in Indonesia, it has increased to 97% from 60% in 1990 [19]. While the trend is upward for most there are some countries where this access is very low, for example, only 8.8% of Chad’s population countries, there are some countries where this access is very low, for example, only 8.8% of Chad's has electricity access. Therefore, we can assume that this factor will increase, and thus also energy population has electricity access. Therefore, we can assume that this factor will increase, and thus consumption, in the future. also energy consumption, in the future. 3. Materials and Methods 3. Materials and Methods The structures of the energy market and total energy production are important to determine the global heatThe emission.structures Whileof the producing energy market useful and energy, total as energy it is shown production in the introduction, are important heat to energydetermine is emittedthe global (as an heat adverse emission. side e ffWhileect)—Equation producing (1). useful Moreover, energy, sooner as it oris later,shown almost in the 100% introduction, of that useful heat energy—electricalenergy is emitted energy (as an oradverse chemical side energy effect)—Equati in fuels—ison finally(1). Moreover, converted sooner to heat or later, energy. almost Because 100% averageof that e ffiusefulciency energy—electrical of a thermal electric energy plant or is aboutchemical 40% energy [5–7], most in fuels—is of the primary finally energyconverted (chemical to heat energyenergy. in coalBecause or natural average gas, efficiency nuclear energy of a inthermal nuclear elec fuel,tric etc.) plant is converted is about directly 40% [5–7], to heat. most Engines of the inprimary cars, where energy chemical (chemical energy energy in petrol in coal is converted or natural to mechanicalgas, nuclear energy, energy have in nuclear similar fuel, efficiency. etc.) is Theconverted results in directly Figure2 showto heat. that Engines the values in ofcars, global wh energyere chemical production energy and energyin petrol consumption is converted are to verymechanical similar—they energy, are approximatelyhave similar efficiency. the same. The Because resu thelts in global Figure annual 2 show useful that energy the values production of global is knownenergy (Figures production2 and 3and), taking energy the consumption e fficiency about are 40%,very totalsimilar—they annual energy are approximately produced on the the Earth same. couldBecause be written the global by Equations annual (1)useful and energy (2). Unfortunately, production asis itknown is shown (Figures in Figure 2 and3, the 3), amount taking of the energyefficiency produced aboutby 40%, renewable total annual sources energy is still produced very low on on the a global Earth scale.could Therefore,be written itby is Equations reasonable (1) toand adopt (2). the Unfortunately, average efficiency as it ofis theshown energy in Figure production 3, the process amount at of 40%, energy as in produced thermal power by renewable plants, becausesources this is still dominates. very low The on totala global power scale. produced Therefor bye, our it is civilization reasonable onto theadopt Earth the isaverage determined efficiency by Equationof the energy (3). production process at 40%, as in thermal power plants, because this dominates. The total power produced by our civilization on the Earth is determined by Equation (3). Etotal = Eheat + Euse f ul (1) E 0.4 E (2) use f ul ≈ × total Energies 2019, 12, x FOR PEER REVIEW 8 of 13

= + Etotal Eheat Euseful (1) ≈ × Euseful 0.4 Etotal (2)

Energies 2019, 12, 3069 Etotal 8 of 12 P = (3) total 3600× 24× 365 Etotal where Euseful—annual useful energy productiP =on (electricity, motion, etc.)—it is given in Figures 2 (3)and total 3600 24 365 3, Etotal—total annual energy, which is converted× to ×heat (as an adverse side effect) and useful where E —annual useful energy production (electricity, motion, etc.)—it is given in Figures2 energy,useful Eheat—annual heat energy production, Ptotal—total power produced on the Earth (in Watts). andAll3 ,energiesEtotal—total are in annual joules energy,per year. which is converted to heat (as an adverse side effect) and useful energy, E —annual heat energy production, P —total power produced on the Earth (in Watts). Basedheat on the global energy production oftotal useful energy (Euseful), it is possible to estimate the Alltotal energies energy are (heat in joules energy per and year. useful energy), which is also finally converted to heat in consumers. Based on the global energy production of useful energy (E ), it is possible to estimate the At this point, the question arises whether the value of the calculateduseful Etotal (in global terms) is high, totallow, energy significant, (heat energyor insignificant. and useful To energy), answer whichthis question, is also finally the total converted power produced to heat in on consumers. the Earth Atwould this point, be compared the question to arisesthe total whether solar theirradiation value of thereaching calculated the Earth’sEtotal (in surface. global terms) It is presented is high, low, by significant,factor n in orEquation insignificant. (4). To answer this question, the total power produced on the Earth would be compared to the total solar irradiation reaching the Earth’s surface. It is presented by factor n in Equation (4). Ptotal n =P (4) n = total (4) PGNDPGND wherewheren —then—the ratio ratio of of total total power power produced produced on on the the Earth Earth to to the the power power of of solar solar irradiation irradiation hitting hitting the the Earth’s surface, P —solar irradiation power hitting the Earth’s surface (the ground). Earth’s surface, GNDPGND—solar irradiation power hitting the Earth’s surface (the ground). TheThe heat heat produced produced on the on Earth the combinesEarth combines with the energywith the supplied energy from supplied the Sun. from Consequently, the Sun. theseConsequently, two energies these together two energies cause the together energetical cause eff thecte asenergetical if the Earth effect was as a if little the closerEarth towas the a Sun. little Tocloser illustrate to the this Sun. effect, To we illustrate imagined this the effect, Earth we before imagined the industrial the Earth revolution before (beforethe industrial the 19th revolution century) in orbit with a radius of r —Figure8. Nowadays, additional heat emission causes an e ffect of the (before the 19th century)0 in orbit with a radius of r0—Figure 8. Nowadays, additional heat emission seeming shortening of the Earth’s orbit to a radius of r . causes an effect of the seeming shortening of the Earth’s1 orbit to a radius of r1.

FigureFigure 8. 8.Global Global heat heat emission emission causes causes the the seeming seeming energetical energetical eﬀect effect as ifas the if the Earth Earth was was a little a little closer closer to theto Sun.the Sun.

TheThe seeming seeming shortening shortening of of the the Earth’s Earth’s orbit orbit is is given given by by Equation Equation (5). (5).

s ==r0 r−1 (5)(5) s r−0 r1 SunSun radiance, radiance, it it means means the the radiant radiant power power per per unit unit area area emitted emitted over over all all wavelengths wavelengths and and all all directionsdirections (watts (watts per per squaresquare meter)meter) of the Sun’s Sun’s surface surface area, area, is is given given by by the the Stefan-Boltzmann Stefan-Boltzmann law law[8]—Equation [8]—Equation (6). (6). The The total total power power emitted emitted by bythe the Sun Sun is given is given in Equation in Equation (7). (7).

4 R∗ = σ T (6) ×

P = R∗ A (7) Sun × Sun where: Energies 2019, 12, 3069 9 of 12

R*—Sun radiance—power emitted by one square meter of the Sun’s surface area (W/m2)

PSun—total power emitted by the Sun (Watts) 2 ASun—Sun’s surface area (m ) T—the temperature of the Sun’s surface σ—Stefan-Boltzmann constant 5.67 10 8 (W m 2K 4) · − − − The sunrays are emitted over all directions from the Sun. As we move away from the Sun (the distance from the Sun increases), the intensity of light decreases. For the distance “r” from the Sun, the solar radiation strikes the surface (sphere) whose area is equal to 4πr2. The surface power density (called also solar constant, ﬂux density) for the distance “r” is represented by Equations (8)–(11).

PSun Pd(r) = (8) 4 π r2 × × 4 ASun σ T Pd(r) = × × (9) 4 π r2 × × introducing the constant “k”, we obtain:

A σ T4 k = Sun × × (10) 4 π × 1 P (r) = k (11) d × r2 where Pd—power density, solar constant, power per unit of surface reached to place at a distance of “r” from the Sun in a unit of W/m2, r—distance from the center of the Sun (in meters) Finally, the surface power density for the point at a distance of “r“ from the Sun is inversely proportional to the square of the distance. Because the mean distance of the Earth from the Sun is about 149.6 106 km [9], the surface power density above the atmosphere of the Earth is about 1380 W/m2, × theoretically based on Equation (9), and about 1366 W/m2 in reality [10].

4. Results and Discussions Global useful energy produced on the Earth (Figure2) in 2000 was equal 10,016 Mtoe (419.35 1018 J), and in 2017 was equal 14,080 Mtoe (589.50 1018 J). Total produced energy (heat + × × useful energy) is given in Equation (12) (transforming Equation (2)).

Euse f ul E (12) total ≈ 0.4 The Sun always illuminates the surface of the Earth seen as a wheel. Total power of the solar rays reaching the top of the Earth’s atmosphere (Equation (13)) can be computed by multiplying the surface power density (Equation (9)) and illuminated Earth’s surface—the wheel with a radius of 6378 km [9]. Very rare phenomena, such as the solar eclipse, are omitted.

P = P π R2 1.7 1017, W (13) SE d × × Earth ≈ × where REarth—radius of the Earth, PSE—the power of the solar irradiation reaching the top of the Earth’s atmosphere. This result is conﬁrmed by the Authors in work [11]. Around 8.1 1016 W of solar radiation × passes through the atmosphere and arrives at the surface of the Earth, which accounts for 47% of the solar energy that reaches the Earth [11]—Equation (14).

P 0.47 P (14) GND ≈ × SE Energies 2019, 12, 3069 10 of 12

where PGND—solar irradiation power hitting the Earth’ surface (the ground). The “n” ratio (total power produced on the Earth to the power of the solar irradiation ratio) is obtained in Table1.

Table 1. Calculated values of P and “n” ratio. P = 8.1 1016 W. total GND × Year E ,J/Year P ,W n= Ptotal total total PGND 0.414 10 3 2000 1048.37 1018 3324 1010 × − × × (0.0414%) 0.577 10 3 2017 1473.75 1018 4673 1010 × − × × (0.0577%)

Taking Equations (11) and (14), (15) could be written as:

2 1 PGND(r) = 0.47 k π R (15) × × × Earth × r2 where PGND(r)—solar irradiation power hitting the Earth’s surface (the ground) as a function of the distance between the Earth and the Sun. Next, we introduced the radius r0 of the actual (real) orbit of the Earth and the hypothetical radius r1 of the orbit, which is shorter and corresponds to a little higher solar power. It means the heat emission causes the eﬀect of the seeming shortening of the Earth’s orbit to a radius of r1. Because the PGND is inversely proportional to the square of the distance (Equation (16)), it is possible to determine the hypothetical radius r1 (Equations (17)–(19)). Finally, the seeming shortening of the radius of the Earth’s orbit is given by Equation (20). 1 PGND (16) ∼ r2 P = P + P = P + n P (17) GND1 GND0 total GND0 × GND0 r PGND0 r1 = r0 (18) × PGND1 s PGND0 r0 r1 = r0 = (19) × PGND0 (1 + n) √n + 1 × r0 s = r0 (20) − √n + 1 where r0—radius of the actual (real) orbit of the Earth, r1—radius of a hypothetical orbit where the little higher solar power is the equivalence of the total energy produced on the Earth, s—seeming shortening of the radius of the Earth’s orbit. In conclusion, the heat emission as a consequence of energy production on the Earth gives the same eﬀect as shortening the radius of the Earth’s orbit by about 31,000 km in 2000 and about 43,300 km in 2017 with respect to the time directly before the industrial revolution (before the 19th century).

5. Conclusions Total energy produced by our civilization on the Earth consists of the useful energy (electricity, mechanical energy, etc.) and heat, as an adverse side effect. Unfortunately, the various types of useful energy are finally converted to heat in machines, vehicles, and devices. The estimated calculations presented in this work prove that the total power produced by us was 0.0414% in 2000 and 0.0577% in 2017 of the global solar power reaching the Earth’s surface—it means reaching the lowest layers of the atmosphere, almost the ground. A significant increase in the “n” factor between 2000 and 2017 results from the increase in global energy production. Energies 2019, 12, 3069 11 of 12

A few questions arise here—are these values high or low? Are they important? A very good determiner of the importance of these values is the value of cyclic, annual changes of the Earth’s orbit. The orbits of planets are not circles; they are ellipses. The eccentricity of planets is a very well-known natural phenomenon in the solar system. As a result of the elliptical trajectory of the Earth around the Sun, the solar light power density varies about 3.3% [11], and that is over 50 times more than the “n” factor in Table1. After inserting data into Equation (20), the total heat produced on the Earth causes an effect like a seeming shortening of the radius of the Earth’s orbit around the Sun by about 31,000 km in the year 2000, and about 43,300 km in the year 2017. Consequently, the seeming radius shortening (“s” in Equation (5), Figure8) is about 2.4 (for 2000) and 3.4 (for 2017) times bigger in comparison to the Earth’s diameter (12,756 km). These distances are significant compared to the Earth’s dimensions, but, in the field of astronomy, they are very small. Taking into account that the average Earth-Sun distance is about 1496 105 km, the seeming shortening “s” is 3455 times smaller (in 2017). However, × the key factor in assessing the importance of the heat emitted during the global energy production in terms of climate impact is the comparison of the parameter “n” to the natural changes of the solar light power density reaching the Earth. That power density varies about 3.3% cyclically during every year (the “n” is about 50 times smaller), and this is why the total heat energy produced by our civilization has a small impact on the global warming in the time horizon of several dozen years. We can say that there would be a one-year increase of supplied energy by about 3.3% of the average solar energy once every 50 years. It would probably have significance over several hundred years. Therefore, the use of renewable energy sources makes sense regardless of their energy efficiency because the emitted heat during the generation of electric power in such sources does not significantly affect the climate. For example, photovoltaic solar cells have a low energy efficiency—a dozen or so percent [28]. The fact that more than 80% of solar energy is converted into heat in photovoltaic panels should not be a limitation in their widespread use.

Author Contributions: Conceptualization, A.M. and A.N.; Methodology, A.M. and A.N.; Validation, A.M. and A.N.; Formal Analysis, A.M. and A.N.; Investigation, A.M. and A.N.; Resources, A.M. and A.N.; Data Curation, A.M. and A.N.; Writing—Original Draft Preparation, M.A. and A.N.; Writing—Review & Editing, M.A. and A.N.; Visualization, A.M. and A.N.; Supervision, A.M.; Project Administration, A.M.; Funding Acquisition, A.M. Funding: This research received no external funding. Conﬂicts of Interest: The authors declare no conﬂict of interest.

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