Potential Lives Saved by Replacing Coal with Solar Photovoltaic Electricity Production in the U.S.

1 2 Preprint: Emily W. Prehoda & Joshua M. Pearce. Potential Lives Saved by Replacing Coal with Solar Photovoltaic Electricity Production 3 in the U.S. Renewable and Sustainable Energy Reviews. doi: http://dx.doi.org/10.1016/j.rser.2017.05.119 4 5 6 Potential Lives Saved by Replacing Coal with Solar Photovoltaic Electricity Production in the 7 U.S. 8 Emily W. Prehoda a & Joshua M. Pearce b,c,* a 9 Department of Social Sciences, Michigan Technological University, USA b 10 Department of Materials Science and Engineering, Michigan Technological University, USA c 11 Department of Electrical and Computer Engineering, Michigan Technological University, USA 12 13 *Corresponding author. E-mail: pearce@mtu.edu. 1400 Townsend Drive, Houghton, Michigan 49931- 14 1295, Telephone: (906) 487-1466. 15 16 17 Abstract 18 19 Poor air quality from coal combustion adversely impacts human health including mortality and 20 morbidity effects on respiratory, cardiovascular, nervous, urinary, and digestive systems. However, the 21 continued use of coal are no longer necessary to provide for society's electrical needs because of 22 advances in solar photovoltaic (PV) technology. In order to inform health policy this paper reviews the 23 data for quantifying the lives saved by a replacement of U.S. coal-fired electricity with solar PV 24 systems. First the geospatial correlation with coal fired power plants and mortality is determined for the 25 U.S. at the state level. Then, current life cycle mortality rates due to coal combustion are calculated and 26 current energy generation data is collated. Deaths/kWh/year of coal and PV are calculated, and the 27 results showed that 51,999 American lives/year could be saved by transitioning from coal to PV- 28 powered electrical generation in the U.S. To accomplish this, 755GW of U.S. PV installations are 29 needed. The first costs for the approach was found to be roughly $1.45 trillion. Over the 25 year 30 warranty on the PV modules the first cost per life saved is approximately $1.1 million, which is 31 comparable to the value of a human life used in other studies. However, as the solar electricity has 32 value, the cost per life is determined while including the revenue of the solar electric generation using a 33 sensitivity analysis on the value of the electricity. These results found that for most estimations of the 34 value, saving a life by offsetting coal with PV actually saved money as well, in some cases several 35 million dollars per life. It is concluded that it is profitable to save lives in the U.S. with the substitution 36 of coal-fired electricity with solar power and that the conversion is a substantial health and 37 environmental benefit. 38 39 Keywords: public health; pollution; photovoltaic; lives; coal; solar energy 40 41 1. Introduction 42 Coal combustion for electrical generation not only contributes to high levels of carbon dioxide 43 emissions [1-3] with the concomitant climate disruption [3-6], but also to conventional air pollution 44 [5,7]. Coal fired electrical power plants released 23% of air pollutants [8] and the largest contributors to 45 U.S. carbon dioxide emission is electrical generation (31%) [9]. While coal use is declining due to 46 natural gas resources and renewable energy growth [10], coal combustion still accounts for roughly 30- 47 40% of U.S. carbon dioxide pollution, contributing to ever-expanding climate change [3,12]. Air 1 48 pollutants are classified into four groups: gaseous, persistent organic, heavy metals, and particulate 49 matter [11]. The literature shows a positive correlation between mortality and morbidity due to outdoor 50 air pollution [12-15]. Specifically, it is well established in the historical and current literature that coal 51 combustion results in emissions of carbon dioxide, methane (gaseous pollutants), particulate matter, 52 nitrogen and sulfur oxides (gaseous), and mercury (heavy metal) [2,4,7,12,16-19]. A review of poor air 53 quality from coal combustion is shown in Table 1. Poor air quality from coal is well known to 54 adversely affect human health including: mortality and morbidity effects on respiratory, cardiovascular, 55 nervous, urinary, and digestive systems. This paper will focus on a review of the mortality due to 56 emissions from coal-fired electrical generation. 57 58 Table 1. Major health effects from coal combustion emissions. 59 Estimated Affected Coal Emissions Medical Condition Individuals* Responsible Respiratory Asthma 22.9 million NOx, PMx* Chronic Obstructive Pulmonary Disease 12.1 million NOx, PMx Lung Cancer 159,217* PMx Heart Attack 7.9 million PMx Cardiovascular Congestive Heart Failure 5.7 million PMx Ischemic Stroke 104,000 NOx, PMx, SO2 Neurological Developmental delays 637,233 Mercury70 60 *Estimated affected individuals include both mortality and morbidity rates. PMx (particulate matter) 61 encompasses particulate matter size between 2.5 and 10 micrometers. NOx (nitrogen oxide) [3,11- 62 13,20]. 63 64 A full life cycle accounting of coal reveals an estimated $523.3 billion in damages (including 65 social and environmental externalities), which is roughly $0.27/kWh generated [7]. Thus, the 66 externalities of coal-fired electricity are more than double the average cost of residential electricity in 67 the U.S. of $0.12/kWh [21]. Although coal is detrimental in all stages of its life cycle, combustion is 68 the stage with the heaviest health burden [16] in the form of mortality and morbidity effects due to 69 outdoor air pollutants/emissions (see Table 1). 70 Most research devoted to addressing issues of coal degraded air quality has focused on 71 mitigation of coal plant emissions using regulations and mechanisms such as cap and trade through 72 permits [22], which are vigorously opposed by the coal industry [23]. These mechanisms decreased 73 some gaseous pollutants by targeting sulfur and nitrogen oxides through a cap and trade regulatory 2  74 policy [24]. Particulate matter (absorbed through inhalation and ingestion) and carbon dioxide (impacts 75 climate processes) continue to pose severe risks [17,25]. Particulate matter is directly linked to 76 increased mortality due to lung cancer and respiratory disease [12,26]. 77 Fortunately, the continued use of coal and the required complicated emissions controls are no 78 longer necessary to provide for society's electrical needs because of advances in renewable energy 79 sources such as solar photovoltaic (PV) technology [1,4,27]. PV produces no emissions or generate 80 liquid or solid wastes during use and has a well-established environmentally-friendly ecological 81 balance sheet [28-33]. The environmental benefits of PV are found in net energy studies [28], life cycle 82 analysis studies [29,32], emission studies from PV [30], sustainability indicators [31] and when 83 compared to other energy sources [33]. Integrating rooftop solar has potential to provide 39% of the 84 total U.S. electrical generation [34] and with the potential to build solar farms on unused tracks of land 85 [35], transitioning to solar PV has potential to replace coal as an energy source entirely [36-37]. Thus, 86 by replacing coal-fired electricity with PV-generated electricity there is an expected decrease in air and 87 waste emissions (e.g. greenhouse gases and air pollution particulates) that affect overall air quality and 88 would be expected to improve human health. However, how significant this health impact would be is 89 not known. 90 In order to inform health policy the objective of this review is to evaluate past research to 91 quantify the American lives saved by a complete elimination of the domestic coal industry with the 92 scale up of solar PV systems. First the geospatial correlation with coal fired power plants and mortality 93 is determined for the U.S. at the state level. Then, current life cycle mortality and morbidity rates due to 94 coal combustion are reviewed and current energy generation data is used to determine the current lives 95 saved by PV and the increase in U.S. PV installations to replace coal-fired electrical generation entirely. 96 Then, American deaths/kWh of coal and PV per year are calculated, enabling health policy analysts to 97 determine the number of lives currently saved by existing PV production and the potential for 98 eliminating all premature deaths from coal combustion in the U.S. The first costs for the approach is 99 calculated per lives saved over the life time of the PV systems. Finally, the cost per life is determined 100 while including the revenue of the solar electric generation using a sensitivity analysis on the value of 101 the electricity. Public health impact results and policy interventions are discussed. 102 103 2. Methods 104 Coal-fired electricity emissions [38] were geolocated in the U.S to illustrate the geospatial 105 relationship between coal emissions related mortality. Two shapefiles were obtained from the ArcGis 106 database to analyze current air pollution due to coal-fired electrical production in the United States: (1) 107 a shapefile of the U.S. [39], and (2) a shapefile of the current U.S. coal electrical plants [40]. This data 108 was then transcribed on a map utilizing ArcMap 10.3.1 to indicate potential areas for PV penetration. 109 Then annual mortality due to coal emissions per 100,000 people was added to the map [41]. 110 Total U.S. electrical generation was obtained to quantify the percentage of kWh produced by 111 coal and solar PV in the U.S. [42]. Current U.S. solar penetration data was obtained to provide for the 112 baseline of PV lives saved now and in order to calculate the amount of PV needed to replace coal-fired 113 electrical generation entirely. Current solar PV penetration has reached roughly 27.4 GW [43]. This 114 aggregate of solar PV produces 2.32x107 kWhrs/year [44]. 115 In order for PV to completely eliminate coal, the total DC rated power of PV needed, ST, is 116 calculated as follows: 117 118 [GW] (1) 3 119 120 where CT is the total amount of coal-fired electricity produced per year (1.32 x1012 kWh/year) 121 [45], and I, which is measured in kWh/m2/day, is the population weighted average U.S. peak sun hours 122 per day that represents solar flux for solar PV generation and is determined by: 123 124 [kWh/m2/day] (2) 125 Where Ps is the 2015 population of each state [46], Is is the average solar flux in each state [47], 126 and PT is the total 2015 U.S. population [40]. It was found to be 4.79 kWh/m2/day. 127 There is a rich history of mortality studies on energy sources. The contribution to mortality was 128 quantified utilizing a review of the secondary sources for coal [13,14,48-50] and PV [29,32,51,52]. A 129 quantification of emissions throughout the entire life cycle of coal was necessary to determine the 130 average U.S. number of premature deaths per year, Fc. The coal-fired electricity life cycle is divided 131 into four components: extraction, transport, processing, and combustion [7]. The solar-photovoltaic 132 system life cycle is divided into 5 components: mining, purification, manufacturing, operation, and 133 recycling [30]. Waste, in the form of emissions, is calculated at each stage of the technologies life 134 cycle and is aggregated. 135 Thus, the electricity generation death rate for coal, rc is given by: 136 137 [American deaths/kWh/year] (3) 138 139 where DTC is the total number of deaths due to coal fired electrical emissions, which is 140 52,000/year [53]. 141 The electricity generation death rate for solar photovoltaic technology, rPV, is given by: 142 143 [U.S. deaths/kWh/year] (4) 144 145 where the total energy generated by PV, ETPV is 2.32x107 kWh/year [44] or 2.65x10-3 GW- 146 yr/year, where the GW-yr is a unit of energy. The total deaths per year due to PV is more challenging to 147 determine. For thin film amorphous silicon PV the value is currently zero based on the limited number 148 of cases in the U.S. Environmental Protection Agencies Risk Management Program database [29]. The 149 actual values of deaths from other PV materials is similarly not available. To remain conservative, the 150 values for crystalline silicon-based PV (both mono- and multi-crystalline silicon) with crystal silicon 151 (c-Si)-based semiconductor industry. This assumption is reasonable because both the semiconductor 152 industry and the PV industry are dominated by the processing of silicon materials [54]. c-Si-base solar 153 cells can be fabricated via a chemical route (quartz, carbothermic reaction, chemical purification and 154 then wafer and cell production) or a metallurgical route (quartz, carbothermic reduction, metallurgical 155 purification and then wafer and cell production). Up to the wafer stage the processing is identical for 156 both industries with the semiconductor industry refining the silicon only to a higher purity for wafers. 157 In addition, many of the processes for cleaning are used by both industries as well (e.g. the use of four 158 step RCA clean using water, ammonium hydroxide , and hydrogen peroxide (5:1:1); aqueous 159 hydrofluoric acid (1:50 or 1:100); water, hydrochloric acid and hydrogen peroxide (6:1:1); and 4 160 deionized water). For device fabrication the doping processes are also the same (e.g. p doping boron 161 with and n doping with phosphorus). The steps to form a transistor in the semiconductor are different 162 from a p-n junction PV device, however, they result in the deposition of relatively small amounts of 163 other materials (e.g. gate oxides and contacts). Thus, the deaths for c-Si-based PV will be estimated 164 from the values of material used weighted number of deaths from chemical accidents in the larger 165 chemical industry involving listed hazardous substances that are also used in solar cell or PV module 166 manufacturing (e.g. SiHCl3 and SiH4 for silicon processing AsH3, PH3, and B2H6 for doping , and HF 167 and Hcl for cleaning). This provides less than 10-4 deaths per GWyr, which is far safer than coal 168 [29,32]. The DTPV, deaths per year from PV, is currently amounts to 2.648x10-7deaths/year (e.g. far less 169 than 1). 170 The total lives (L) saved per kWh of solar PV electricity production offsetting coal-fired 171 electrical generation is given by: 172 173 [U.S. lives saved/kWh] (5) 174 175 176 Utilizing current industrial PV costs, P, of $1.92/W [55], the first cost per life, CFL, saved by 177 purchasing a PV system to offset coal use nationally is calculated as follows: 178 [First cost $ invested/U.S. lives saved in PV lifetime] (6) 179 180 Where ST x 109 is total solar in GW converted to W, and Fc represents the number of fatalities due to 181 coal combustion emissions per year and lpv is the lifetime of the PV. However, unlike conventional 182 health policy interventions that only have a first cost, this policy would also generate revenue, which 183 must be taken into account, which allows for a cost per life, CL, over a specific period, T: 184 [$/U.S. lives saved over T years] (7) 185 Where v is the $/kW-hrs of the PV generated electricity replacing all of coal. A sensitivity analysis is 186 run on v and to avoid complications the energy cost escalation rate is assumed to track with inflation. 187 3. Results 188 189 There is a clear correlation between annual mortality due to coal emissions and the geographic 190 locations of coal fired power plants in the U.S. as can be seen in Figure 1. Dense regions of mortality 191 are correlated with high coal-fired electrical emissions in the central and northeast of the U.S. 192 Emissions from coal-fired electricity total 1.57x109 million metric tons in 2013 [9]. 193 194 195 196 5 197 198 Using equations 1 and 2, to completely replace coal-fired electricity would require 755 GW of solar 199 PV. As the death rate from coal is 3.9393939x10-8 deaths/kWh from equation 3 and that of PV is 200 1.14x10-14 deaths/kW-hr from equation 4. It is clear that from a human mortality standpoint PV is far 201 safer than coal produced electricity. This is quantified in equation 5, which provides 3.9393927x10-8 202 lives saved per kW-hr as the respective death rates are 6 orders of magnitude larger for coal than PV. If 203 the entire U.S. coal fired electricity production were switched to PV production. This would result in 204 51,999 American lives saved per year. 205 206 Installing 755GW of PV in the U.S. at $1.92/W [56], would cost the U.S roughly $1.45 trillion dollars. 207 Following equation 6 and using a 25 year warranty on the PV modules as the lifetime this results in a 208 first cost per American life saved of roughly $1.1 million per life. However, there are several 209 complicating factors, first the output efficiency of PV modules degrades with time. For most technical 210 studies this has been shown to be 0.5% per year degradation rate or less and that is what is used in PV 211 economic studies [57]. The warranty for PV and its effective lifetime is set at 25 years, although it is 212 clear the real lifetime of the PV would be much greater than that. In general the 25 year warranty for 213 PV guarantees the PV power is performing at 80% of the initial rated power or better. Thus, to remain 214 conservative these factors both decrease and increase cost per life respectively, they have been assumed 215 to roughly cancel out and be ignored. The far more important complicating factor of using PV 216 replacement of coal as a public health policy measure is the value of PV-generated electricity. Using 25 217 years again and equation 7 the cost per life varies substantially depending on the value assigned to the 218 electricity as seen in Table 2, which ranges from over $1.1 million per life saved if the electricity has no 219 value, through coal generation with zero value placed on externalities [57], and net metering through 220 various scenarios [58], the calculated value for solar [59] to -$4.6m per life saved if the residential 221 retail rate is used in an isolated rural community [60]. 222 Table 2. The Value of solar PV-generated electricity and the impact on the cost per life saved. Method of Valuing Solar Elec- Solar PV US$ Cost per Life tricity US$/kWhr value/year (US$/life) No value 0 0 $1,115,076 Coal generation only [57] $0.0323 $4.26 x1010 $295,153 Net metering industrial [58] $0.068 $8.98 x1010 -$611,077 Net metering commercial [58] $0.1050 $1.39 x1011 -$1,550,308 Net metering residential [58] $0.1261 $1.66 x1011 -$2,085,923 Value of Solar Minnesota [59] $0.145 $1.91 x1011 -$2,565,693 Net metering Houghton, MI [60] $0.2273 $3.00x1011 -$4,654,847 223 224 4. Discussion 225 226 Although, Figure 1 illustrates areas of high emissions due to coal-production, it is important to 227 note that air pollution can be dispersed through the air and affect regions at large distances from the 228 source [5, 15]. Carbon dioxide indirectly results in premature death due to climate change events and 229 according to WHO analyses, climate change is expected to cause 250,000 additional deaths per year 230 between 2030 and 2050 [3,64]. Decreases in sulfur dioxides results from burning “clean coal”, washing 231 coal, and utilizing scrubbers to chemically remove sulfur dioxide from coal burning smokestacks, 6 232 resulted in decreasing sulfur dioxide levels from 15.7 m tons in 1990 to 10.2 m tons in 2005 [61]. This 233 was completed through cap and trade-based policy. The EPA issued control standards under clean air 234 act, which includes NOx, SO2, and PMx. Decreases in particulate matter may not be correlated with 235 decreased mortality as there is no well-defined safe threshold for particulate matter [12]. Particulate 236 matter made up of smaller particles, which travel deep into respiratory tract and become lodged 237 permanently [62]. Thus, despite improvements coal emissions remain a significant threat to mortality 238 rates in the U.S. This paper found that a large number of premature deaths, about 52,000 in the U.S. 239 due to coal-fired emissions during electrical generation, could be eliminated by a conversion to PV- 240 based electrical generation. 241 To accomplish this national health benefit the amount solar PV needed to mitigate premature 242 death due to coal-fired electrical production was 755 GW. 755GW is a significant increase over current 243 U.S. PV penetration levels (27.4GW). Thus, only 3.6% of the PV necessary to prevent the current life 244 loss from coal pollution is available. It should also be pointed out that there are some lifecycle 245 emissions from PV [7, 30, 51, 63]. However, the full life cycle of PV produces a fraction of the carbon 246 dioxide equivalent emissions when compared to coal [30, 64, 65]. Air pollution throughout full life 247 cycle of PV tends to vary with materials used during manufacture and mining [63], however, the 248 negative environmental impacts of PV generally involve accidental operation error [66,67]. In 249 summary, the substitution of coal-fired electricity with solar power is a substantial health and 250 environmental benefit and clear path towards a more sustainable state [27]. 251 This study made several estimations to obtain these values, which should be pointed out. First, 252 the population weighted average of solar flux was used to determine the energy generation rather than a 253 detailed analysis of the geographic variation of PV production potential across the U.S. For the 254 purposes of this study the error introduced with this method is small, but more detailed studies on both 255 the rooftop PV potential [68-70] and the solar farm [35] and even agrivoltaic [71,72] potential, would 256 provide a more granular (e.g. including shading losses) estimates for decision makers (e.g. at the state 257 or community level). Second, the premature deaths from coal related emissions are actually 258 conservative. This study provided analyses of only the combustion step in coal electrical generation in 259 the United States. To capture the full scope of mortality rates in the U.S., analyses must be expanded to 260 include the full life cycle of coal; this includes sectors other than electrical (industry, manufacture of 261 synthetic fuel, or manufacturing steel) that utilize coal. Other externalities exist for coal, including land 262 use, water pollution, natural resource depletion, habitat destruction [73]. These uncertainties must be 263 quantified for both coal and solar PV to determine accurate measure of lives saved by replacing one 264 electrical generation source for another. However, it is clear from the results that the potential 265 American lives at stake, which can be saved by a policy intervention is warranted that encourages more 266 rapid deployment of PV. 267 Performing a similar analysis at a global scale could be of use to policy makers and the United 268 Nations to satisfy Sustainable Development Goal #7: Ensure access to affordable, reliable, sustainable, 269 and modern energy for all [74], while significantly reducing global lives sacrificed to current coal 270 combustion. Current global outdoor air pollution is concentrated in developing nations due to continued 271 increase of coal use [18]. As a result, larger mortality rates of developing nations are expected to 272 continue [12,48]. The World Health Organization estimates 7 million deaths per year due to air 273 pollution (of these 2.6 million are linked to outdoor air pollution), making it the single largest 274 environmental risk today [75]. Air pollution related mortality outweighs global car accidents (1.3 275 million people [76]) by a factor of five and natural disasters by a factor of 28 (mortality ranging from 276 20,000-250,000 people depending on the year) [77]. It can thus be assumed that the deaths per unit 277 energy will be even more extreme on the global scale as the U.S. environmental protection standards 278 are more advanced than much of the world. In addition, this does not take into account the potential 7 279 premature deaths aggravated by climate change for which the Intergovernmental Panel on Climate 280 Change (IPCC) already recommends immediate action to reduce emissions by 2050 [78]. 281 To meet the health-related demand of eliminating coal pollution with solar power in the U.S., 282 $1.45 trillion dollars would need to be invested in new PV generation. This is the total cost to save all 283 future lives in the U.S. from coal-related electricity over the next twenty-five years. Even with no 284 value the cost per life is only $1.1m, which is on the lower end of the values normally ascribed to 285 human life (between $1 and $9 million) [79-81]. However, unlike other health policy interventions, 286 which only cost money up front [82], PV replacement of coal production also has the potential to 287 generate significant revenue as shown in the third column of Table 2. Table 2 provides a sensitivity 288 analysis on the value of the solar electricity, which is currently under intense debate in the electrical 289 industry. PV is inherently distributed so using the centralized coal value of electricity of $0.03/kWhr is 290 misleadingly pessimistic. In most of the U.S. PV is currently net metered making the values between 291 $0.06-0.12/kWhr more realistic. As can be seen in Table 2, all of these values actually have a net 292 economic benefit for saving lives from only the value of electricity. There has also been a strong case 293 made [59] that net metering actually represents a subsidy to electric utilities as the value of solar can be 294 higher (e.g. $0.14/kWhr in Minnesota). When looking at the potential for isolated communities to 295 adopt solar the current high costs of electricity turn the potential economic savings per life save truly 296 substantial. As technology has progressed to such a point that PV, battery and cogen units can displace 297 the use of the grid in even the most extreme circumstances [83-86], these levels of savings are possible 298 for the small populations living in such regions [60]. The use of PV to offset coal-fired electricity 299 compares exceptionally favorably to more conventional forms of health policy interventions, the best of 300 which (e.g. helping children in developing nations [87]) still costs a few thousand per life rather than 301 conserving money. 302 The results clearly show, premature deaths due to anthropogenic effects (coal combustion and 303 pollution) can be mitigated through anthropogenic efforts (PV electrical energy conversion). Policies 304 can be developed at many scales (international, federal, state, and local levels) to contribute to the 305 concerted climate change mitigation efforts. There are several policy interventions that could accelerate 306 PV adoption: 1) Effective renewable portfolio standards (RPS) programs [88] and Mandatory Green 307 Power Option (MGPO) [89] can be implemented at the state level. As air pollution is not limited to 308 state boundaries, as is shown in Figure 1, requiring states to design RPS programs would decrease 309 emissions from electrical generation. Federal agencies, such as the EPA, can strengthen particle 310 pollution standards, which can indirectly lead the electrical industry to adopt renewable energy 311 generation systems [90, 91]. An alternative strategy includes instituting state taxes or carbon trading 312 mechanisms [92, 93] on coal usage. States and industries that continue coal usage would pay higher 313 taxes to internalize environmental and health effects. EPA regulations such as Mercury and Air Toxics 314 Standards, are responsible for the decommissioning of 72 GW of coal electrical generating capacity 315 [94]; this number is expected to rise by 2020. On the other hand, increasing federal incentives for solar 316 PV will likely result in a rapid transition to cleaner energy generation. It is important to note that a 317 portfolio of these policy implementations will be more effective in reducing emissions and promoting 318 renewables than any single policy or program [90]. In the context of mortality in the U.S., exploring 319 and adapting wartime mobilization strategies [95] to a national solar PV electrical transition may 320 provide enough emission mitigation to slow anthropogenic climate change effects. 321 Finally, this study has only explored the impact of coal-fired electricity conversion to solar PV 322 on mortality. However, current air pollution costs also occur in medical costs and lost productivity. In 323 2010, OECD nations spent roughly $1.7 trillion in attempts to combat and treat effects from outdoor air 324 pollution [96]. The U.S. spends roughly $185 billion per year on coal emission effects; these represent 325 only health related costs [7]. California alone spent $193 million in hospital care in 2007 due to air 8 326 pollution effects [97]. It has long been established that energy policy creates horrendous public health 327 problems and injustices [98], and this study makes clear large scale PV deployment to eliminate coal 328 could help alleviate this historical problem. Future work can help quantify the values of these other 329 effects from a transition from coal to solar based electrical generation. 330 331 5. Conclusions 332 333 The results of this study showed a clear geospatial correlation between coal fired power plants 334 and mortality from air pollution is the U.S. at the state level. To reduce these deaths coal-fired 335 electricity must be eliminated and the results showed that 51,999 American lives could be saved per 336 year by transitioning from coal to PV-powered electrical generation in the U.S. To accomplish this, 337 755GW of U.S. PV are needed and the first costs for such an national array are $1.45 trillion. Over the 338 25 year warranty on the PV modules the first cost per life saved is approximately $1.1 million, which is 339 comparable to the value of a human life used in other studies. However, as the solar electricity has 340 value, the cost per life for offsetting coal with PV actually saved money as well, in some cases several 341 million dollars per life. It is concluded that it is profitable to save lives in the U.S. with the substitution 342 of coal-fired electricity with solar power and that the conversion is a substantial health and 343 environmental benefit. Evolving the U.S. energy system utilizing clean, alternative technology will 344 allow the U.S. to prevent thousands of premature deaths along with becoming a global leader in 345 renewable technology adoption. 346 347 6. References 349 [1] Sims, R, Rogner, H, Gregory, K. Carbon emission and mitigation cost comparisons between 350 fossil fuel, nuclear and renewable energy resources for electricity generation. 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