Residential Solar Power Systems — Can They Help Reduce Emissions?

Proud Green Home – Fair Use

The answer is yes, but only to a limited degree. Performance of these systems vary considerably and are
especially dependent on PSH (peak sunlight hours per day). Here is a list of U.S. states with their PSH scores.

Source: https://renogy.com/blog/-what-are-the-average-peak-sun-hours-by-state/

For an area to be suitable for solar panel use, it must have a PSH of at least 4. (For reference, see https://www.solarreviews.com/blog/peak-sun-hours-explained) Ideal locations would have a PSH of 5 or more.  Only seven states have a PSH greater than 5 – Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming.  Their combined population is 56 million or 17% of the U.S. population.

Next are the states with a marginal PSH, which I’m calling 4 to 5.  They are Delaware, Florida, Georgia, Hawaii, Idaho, Kansas, Louisiana, Montana, Nebraska, North Carolina, North Dakota, South Carolina, and Tennessee with a combined population of 71 million or 22% of the total US population.  If, for argument’s sake, we
say that it’s feasible to install a solar power system in these marginal states half of the time.  That’s 11% of the population.

Add this 11% to the 17% who live in states with optimum peak sunlight hours, and we get 28%.  This leaves 72% of the US population living in areas that are unsuitable for home
solar power systems.

Commercial solar farms can overcome the local PSH problem by concentrating their panels in high PSH areas and sending the power to areas with lower PSH.  That is the strategy which we’re following. Residential solar power installations would still be useful where the PSH is adequate and there is no grid access.  So, let’s now go beyond residential solar power systems and consider the feasibility of solar power in general.

A Commercial Solar Array

Courtesy of YSG Solar – Fair Use

SOLAR PANEL EFFICIENCY 

Here’s a link to a 2019 article in Wired Magazine that addresses solar panel efficiency…

https://www.wired.com/story/new-designs-could-boost-solar-cells-beyond-their-limits/

Summary: In the past 20 years, solar panel efficiency has improved from 15% to 22%.  Continued improvement is expected, but the Shockley-Queisser Limit limits the efficiency of a single-junction solar cell to 33%.  Multi layer panels can exceed this, but they’re expensive to build.  Most research now is focused on maximizing the efficiency of the single-junction cell.  R&D could lead us anywhere, but for the near future, it looks like maximum panel efficiencies will remain in the 20 percent to 30 percent range.

PERSPECTIVE

We use energy to produce electricity, to produce heat, and to move vehicles and machinery. What seems to be often overlooked in discussions about replacing fossil fuels with renewables is that it will require converting all applications to electricity. How much of our current energy demand goes into making electricity? Here is a link to a report from the IEA (International Energy Agency).

https://www.eia.gov/outlooks/aeo/data/browser/#/?id=15-IEO2019&cases=Reference&sourcekey=0

The data show that, in 2019, a grand total of 187,000 TWh (terawatt-hours) of electricity was used, but that 51,000 TWh of this was wasted in the heat loss involved in generating electricity by burning fossil fuels.  This leaves a useful total of 136,000 TWh, 25,000 (18 percent) of which was used as electricity.  Ten percent of electricity was produced by solar energy. That means that solar power is now only providing 1.8 percent of the world’s energy.

The good news is that, since renewable energy production generates no heat waste, we will not have to replace the 51,000 TWh of energy from fossil fuel combustion.  The bad news is that, even when renewables produce all electricity, we will still be faced with converting the remaining energy from fossil fuel combustion. Add to this the need to build a global energy storage capacity and you have a trifecta of challenges:  energy production, energy storage, and energy use.

BUILDING THE SOLAR PANELS

Let’s just consider the energy production challenge.  With nuclear power currently producing 9,000 TWh and renewables currently producing 32,000 TWh, 94,000 TWh of fossil-fuel generated energy is left.  This amount will increase as demand increases, but to keep things simple, we’ll round it to 100,000 TWh.

According to an article here:

https://www.solarreviews.com/blog/how-much-electricity-does-a-solar-panel-produce a 370-watt solar panel in Arizona produces 2.7 KWh of electricity a day or just under 1,000 KWh of electricity per year.  If we divide 100,000 TWh by 1,000 KWh, we get 100 billion, which is the number of solar panels we will need.  To corroborate this calculation, I found another article that did the same thing.  Here is the link:

https://www.axionpower.com/knowledge/power-world-with-solar/#The_Facts

According to this article, it would take 50 billion 350-watt solar panels occupying 115,000 square miles, an area a little bigger than the entire state of Arizona.  This is just half the number of panels I calculated, but the article was only addressing electricity while I was addressing all energy demand.

The EIA shows global electricity demand of 25,000 TWh or about one fourth of the 94,000 TWh that is the total energy we would need to be replaced with solar. Using this article’s calculations, and adjusting for total energy and not just electricity, the global requirement is four times 50 billion or 200 billion. It’s still a very big discrepancy, but we are in the 100 billion to 200 billion range so it is close enough for government work. Let’s use the 100 billion I calculated as a midpoint.  That would bring the land required to 230,000 square miles, an area nearly the size of Texas.

Let’s consider some of the elements used in building solar panels.

Aluminum:  Roughly 20
pounds of aluminum are used in manufacturing a solar panel.  One hundred billion solar panels would require one billion tons of aluminum – fifteen times the current 65 million tons of aluminum produced globally each year.

Here are links to two articles that discuss the problems that aluminum presents in the manufacture of solar
cells.

https://pv-magazine-usa.com/2020/12/08/solar-needs-aluminum-but-the-metal-has-a-carbon-problem/

https://www.sciencealert.com/solar-panel-boom-s-demand-for-aluminium-is-a-big-carbon-problem

Aluminum is an abundant element, but producing it requires burning a lot of coal, and so it significantly adds to atmospheric CO2.  Producing one ton of new aluminum generates 17 tons of CO2.  One billion tons of new aluminum would generate 17 billion tons of carbon dioxide.  This is nearly half of the current global annual emissions. Research is underway to find cleaner ways to manufacture aluminum.

Silver:  It currently takes about 20 grams of silver to build a solar panel.  I found this article that discusses  the challenges this presents to the solar power industry. Here’s the link:

https://seekingalpha.com/article/4044219-not-enough-silver-to-power-world-even-solar-power-efficiency-to-quadruple

Using the solar panel area as the basis for calculation, the author comes up with 5.62 million tons of
silver
.  Using my weight per panel method, I came up with 2 million tons of silver.  I have not been able to determine why there is a difference, but we’re at the same order of magnitude and, since the world’s current known official recoverable silver reserves is estimated to be less than 600,000 tons, it is a moot point.  Research continues on ways to build efficient solar panels without silver, but if that is not successful, the efficiency of using silver would have to increase by two orders of magnitude to make it feasible.

Steel:  Here is a link to an article about the steel requirements of solar panel manufacture.

https://corporate.arcelormittal.com/media/case-studies/steel-is-the-power-behind-renewable-energy

It takes 35 to 45 tons of steel to build a one-megawatt solar plant.  We’ll call it 40 tons.  The plant would require about 2800 solar panels rated at 350 watts, which means that each panel would have about 28 pounds of steel.  You would need 1.4 billion tons of steel to build 100 billion of these solar panels, which is three quarters of the total global production of steel in 2021.

Glass:  There are about 44 pounds of glass in a solar cell.  You would need 2.2 billion tons of glass
to build 100 billion solar panels
.  According to a report here <https://www.iyog2022.org/images/files/77-economicsiyog-200925.pdf> the annual global
production of glass in 2022 (The International Year of Glass) is expected to be
84 million tons.  The glass required to produce 100 billion solar cells is 25 times that amount.

Although technical innovation will likely reduce these numbers, they are so large to begin with that it does
not seem feasible, especially when the required timeframes are factored in. According to the IPCC, we must reduce global emissions by 50% by 2030 and eliminate them entirely by 2050.

DEGRADATION

The solar energy industry says that the current useful life of a solar panel is 25 to 30 years, but that
doesn’t mean that the panel stops producing energy, just that power production has degraded to the point that solar energy companies want to replace them with more efficient panels, and because not replacing them means that more land is required and that increases costs.  Research may result in ways to prolong
the life of solar panels and retire them in 30 to 40 years instead of 20 to 30. But we would still need to start building the next round of solar panels before they are retired because we would have to compensate for the degradation of the panels still in use.

WASTE DISPOSAL

Here is a link to an article in the Harvard Business Review entitled: “The Dark Side of Solar Power”…

https://hbr.org/2021/06/the-dark-side-of-solar-power

It describes the gargantuan waste problem that the decommissioning of solar power plants will entail.  It isn’t
just the volume of the waste, but the toxicity of some of it, which, because of the vast scale, will be substantial even if just a small percent of the total.

FORECASTS

What is required is not just a reduction in the use of fossil fuels.  We need to eliminate them entirely by 2050 in order to stop the accumulation of greenhouse gases in the atmosphere.
But no projection comes close to this. 
Here is a link to a report by Statista:

https://www.statista.com/statistics/238610/projected-world-electricity-generation-by-energy-source/

The graphs shows that renewable growth will cover the growth in demand, but that it will be unable to reduce
the current level of fossil fuel consumption – a level that is putting 40 billion tons of CO2 into the air each year.  Over the next 28 years, that will amount to over one trillion tons of additional CO2 added to today’s current cumulative emissions of 1.5 trillion tons since 1751 (but mostly since
1960).  That is a two-thirds increase in cumulative emissions.

Here is a link to a forecast by the EIA (the US Environmental Information Administration).

https://www.eia.gov/outlooks/aeo/data/browser/#/?id=15-IEO2019&cases=Reference&sourcekey=0

This forecast is similar to Statista’s but, instead of fossil fuel production remaining level, it is projected to increase by 25%.  Renewable production is expected to almost double, from 38,000 TWh to 74,000 TWh.  Even with this growth, however, renewables are not expected to even cover the additional demand, which is why fossil fuel consumption is expected to increase.

My personal speculation on this is that the impact of the deteriorating climate will have a negative impact on population growth and economic activity, resulting in a lower than forecast demand for
energy.  Nevertheless, without unprecedented global cooperation and effort, we will still be burning massive amounts of fossil fuels and continuing to worsen the adverse climate effects we are already experiencing.

OTHER OPTIONS

The only other options we have are wind and nuclear.  Wind is beset with many of the same problems that we see with solar – the huge infrastructure required, the limited life of the facilities, emissions from construction, and daunting waste disposal issues.

I think we do have an opportunity with nuclear if and when it emerges from the populist and political doghouse it has been in for the past four decades, but nuclear plants are expensive and
take time to build.  Nuclear power currently generates about 8,000 TWh annually.  This is forecast to grow to 11,000 TWh by 2050, but this number could be considerably larger if a major global effort were undertaken to build reactors. There are currently 440 operating nuclear reactors in the world.  If we doubled that by 2050, which would entail not just building new plants but also replacing those due for decommissioning, we could double energy production to 16,000 TWh.  This is a significant amount, but far short of what is required
to eliminate the projected 181,000 TWh of energy which the EIA predicts will still be produced by fossil fuels in 2050.

CONCLUSION

Renewable energy cannot be produced in the quantities necessary to support our current global lifestyle, so energy consumption will have to be substantially reduced in order to meet the target of eliminating fossil fuel use.  There is no popular or political will to do this voluntarily, and, even if there were, the required reduction is not feasible since it would have to be about 50%. COVID caused an economic slowdown that reduced global energy consumption by 7 percent, and that shook the world.  Can you imagine our world as it is today with energy consumption cut in half? Developed countries like the U.S. with high per capita carbon footprints
would have to reduce their energy consumption even more.  Without a major decrease in the population, it can’t happen.  Climate Change will cause that population reduction to occur.