The luminosity of the Sun is measured in yottawatts. A yottawatt is 1 x 10²⁴ watts, or one septillion watts. Truly, this is an astronomical number, hard for us to comprehend. To put it into perspective, the average total power consumption of the human world is approximately 20 terawatts. A terawatt is 1 x 10¹² watts, or a trillion watts, so the average total power consumption of the human world is about 2.0 x 10¹³ watts.
“Woah, woah, woah… back up. What is a watt again?” A watt is a unit of power equivalent to one joule per second. In practical terms, a nightlight is about 4 watts and a CFL bulb is about 14 watts; a microwave oven is about 1100 watts, or 1.1 kilowatts. So, in other words, the total human power consumption is equivalent to about 5 trillion nightlights all shining at the same time, or about 18 billion microwave ovens all being used at the same time.
Humans use a lot of power. 18 billion microwave ovens all heating Hot Pockets at once is mind-blowing, but compared to the luminosity of the Sun, it is microscopic. The Sun’s power output is 385 YW (385 septillion watts), which is sufficient to power 3.5 x 10²³ microwave ovens, or about 50 trillion microwave ovens at the same time for each man, woman, and child on Earth. In short, it is this staggering solar energy output that is the alpha and omega of why Solar is Obvious.
Of course, conservatives, doubters, haters, skeptics, and nitpickers rightly point out that the Sun puts out energy in all directions and, with the Earth being a relatively small sphere in space some 93 million miles away from the Sun, the vast majority of that energy doesn’t come our way. It is radiated out into space. True. But, what fraction of solar output does hit Earth?
The surface of a sphere is given by the formula A = 4πr². The sphere of space with a radius equivalent to the Earth’s orbit is, therefore, about 1.1 x 10¹⁷ square miles. The surface of the Earth is 196.9 million, or 1.969 x 10⁸ square miles. We recall, though, that only half of the Earth is facing the Sun at once, meaning the surface on which light is incident is about 1 x 10⁸ square miles. So, we know that a ratio of 1 x 10⁸/1.1 x 10¹⁷ of the power radiated by the Sun hits Earth. Multiplying that by 385 Yw, we obtain a figure of 3.5 x 10¹⁷ watts, or 350 petawatts. This figure is obviously not exact, as space is not entirely empty, our planet has an atmosphere that blocks some light from reaching Earth, and Earth is a sphere, not a flat circle facing the Sun, floating in space. Correcting for all of this, we find the actual figure for the total incident power received by the Earth from the Sun is 174.0 PW.
This is the number that is most relevant for determining just how obvious solar really is. This is the number we’re starting with when we look at how much solar energy reaches Earth. We recall from before that the total average power consumption of the human world is about 20 terawatts. One petawatt is 1,000 terawatts, which means that 174.0 petawatts is 174,000 terawatts, far greater than the 20 terawatts we use. The ratio of incident solar power to the total power consumption of the human world is 174,000/20, or about 8,700. The Sun pours 8,700 times as much power onto us as we use.
Right here, the obviousness of solar starts to become apparent. But, we, of course, cannot cover the entire Earth with solar panels, and our solar panels don’t capture 100% of the power that hits them. First, we consider that our best solar panels are about 20% efficient, meaning they will convert 20% of the energy incident upon them into power that we can use. So, 20% of 8,700 means that, if we were to convert all of that energy to usable power, it would still be 1,740 times more than we use. But, we can’t use the entire surface of the Earth to generate solar power and, as such, we can only set up solar power production to capture a fraction of that. Fortunately for us, we only need to cover 1/1740 of the surface of the Earth to generate all the power we consume. But, how much is that?
We recall that the Earth is 196.9 million square miles. In order to power human civilization, we need 1/1740 of that to be collecting solar power, or about 113,000 square miles. Unfortunately, half of the Earth is facing the wrong way at any given moment to be able to receive energy from the Sun, so we will have to double this and accept that only half of our collectors are being used at any given time. This means that, to power human civilization, a total of about 226,000 square miles of the Earth’s surface will have to be used for the collection of solar energy. This is an area smaller than the size of Texas, which is about 269,000 square miles, or almost exactly the size of Madagascar, which is 226,658 square miles. More relevant to the discussion on a practical level, however, is that it is less than 10% of the size of the Sahara desert. In fact, the total area of deserts on Earth amounts to around 10,000,000 square miles, if we limit our definition of deserts to include those with almost no plant and animal life. Meaning, of these arid wastelands where nothing much grows or lives, we would need to use about 2.26% of their surface area to produce solar power.
The argument, then, is that we place solar arrays in deserts around the world, where the conditions are best for receiving a great deal of sunlight. Deserts have little in the way of pollution from human beings, since they are sparsely populated on the whole, they have little cloud cover reducing incident light, and, as stipulated, we can select those that are largely devoid of life. Obviously, there will be consequences if solar arrays are placed in deserts all over the world, but surely the alternatives are all worse. Solar is the least invasive, least destructive, most sensible type of energy we have. What’s more, deserts have an albedo of about 0.40, meaning that 40% of the incident light upon them is immediately reflected. In other words, the Earth is not absorbing that light anyway, and it generally ends up getting radiated back out into space, going to waste. Just capturing that energy would increase the area we need to devote to solar power collection from 226,000 square miles to 565,000 square miles, or about 5.65% of the area of the world’s inhospitable, uninhabited deserts.
The amount of space our power generation has to take may increase or decrease depending on how other variables change. Our total power consumption is on the rise, and it’s rising fast. However, solar panel efficiency has also been rising fast, and alternative forms of solar collection and storage are also on the rise, with different technologies offering different advantages and disadvantages. For instance, enormous solar thermal power plants have gone online in recent years, capable of producing hundreds of megawatts of energy.
The numbers I have used are approximations, drawn primarily from Wikipedia, and are meant to illustrate the concept that we receive significantly more power from the Sun than we use. Others have also observed this, such as the United Nations Development Programme, which found that the potential of solar energy was many times larger than the world energy consumption. It is this simple fact that makes solar the glaringly obviously choice for where to invest our time and effort when it comes to energy production. If we consider, too, that wind, ocean current, hydroelectric and other forms of renewable energy are not only more invasive to collect than solar power, but are also derived from solar power, it makes sense to bypass those and go straight to the source. Wind and ocean currents are just heat flux that arise from the equator receiving more energy from the Sun than the poles; Earth is trying to reach temperature equilibrium across the atmosphere and oceans and these mechanisms redistribute that energy accordingly.
Given these facts, we really have no excuse for not converting our civilization to solar power. It is what promises to ultimately be the cheapest, most efficient, least problematic form of power to bridge the gap from the present to the future. The old way of doing things has countless problems. Even just the simple truth that we will run out of mineable resources in a matter of decades, while the Sun will keep shining for billions of years, says more than the myriad other devastating arguments against other forms of energy. Something that lasts for billions of years is certainly more sustainable than something that lasts for mere decades. In the end, it is as clear as day that Solar is Obvious.