The useful US Department of Energy website on solar power starts with the remarkable fact that “the amount of sunlight that strikes the earth in one and a half hours is enough to handle the entire world’s energy consumption for a full year.” This remarkable fact is both fascinating and entirely useless. In theory, of course, we could strip the world of all vegetation and lay out billions of square miles of solar panels and have enough electricity to continue to watch Netflix, play video games and exchange bitcoins for several millennia. We wouldn’t have any food naturally, but we have to get our priorities right in these matters.

In practice, the ability to turn sunlight directly into electricity is possibly the most useful invention of our time. And we have only just started to really use it. About twenty or thirty years ago, solar panels were largely seen as a means to bring electricity to the remotest parts of the earth, not least for medical and educational uses. Way back in 2000, BP, then the second largest producers of these cells, decided to send a team to check on the panels they had installed on some of the remotest Philippine islands a decade early.

Funded by a New Zealand charity, these were for clinics and schools in areas that had little access to grid electricity when they were installed. As the inspectors discovered, they were all working perfectly but, as they also found, the ones at the clinic had been attached to a karaoke machine at which they were all asked to perform. As the barangay captain explained without embarrassment, they only needed the panels for the clinic’s refrigerators for the few days a month when they needed to keep their vaccines chilled. Otherwise, they had brought a new focus for evening parties and entertainment.

Much the same was going on at the schools. While the panels had brought a new awareness of life on the rest of the planet to the schoolchildren through films and pictures on computers, they had also affected adult life too. Suddenly, for a few pesos, the adults could watch Spiderman 2 in the early evening, with surprising results. As the female Governor of Southern Leyte province pointed out, it had slashed the birth-rate. When asked by an incredulous enquirer why, she pointed out that the fishermen put to sea about 10 pm at night and had previously had little to do in the early evening after dark. “We need a lot more of these panels”, she pointed out.

Quite what the charity made of this use of their money remains unknown. However, what used to be a terrific idea for remote area applications is now becoming mainstream. Not the least of the reasons for this is that the price of the panels themselves has been dropping like a stone. Since 1998, when BP put them on the islands, the cost of the photovoltaic cells has fallen by 98% and this has continued to accelerate. Back in 2012, the cost of a residential system was around $6.12 per watt. By 2021, it had fallen to $3.8 per watt.

In fact, turning sunlight into electricity is not exactly new. Alexandre Edmond Becquerel, father of the more famous radiation expert Henri, discovered the first solar cell in 1839, when he was 19. He discovered that more electricity was produced if two electrodes were running through a conducting solution if it was done in sunlight. This was nothing more than an experimental surprise, but Charles Fitts patented the idea using selenium wafers and a small amount of gold-leaf in 1898. The idea never caught on, not least because it was a lot of trouble and expense for not a lot of electricity. Einstein legitimised the whole idea with the theoretical invention of the photon in 1905, for which he got the Nobel prize in 1922.

The whole idea really remained in the area of interesting facts until 1940, when the Bell Laboratories were using silicon for semi-conductors. This was entirely due to an accident, in which one of the silicon wafers was discovered to have a crack in it. When this wafer was exposed to light by researcher Russell Ohl, he found that electricity flowed through it. The crack was a positive-negative, or p-n junction due to the different levels of impurities on either side.

It took a team of three, Gerald Pearson, Daryl Chapin and Calvin Fuller, another thirteen years to find the right mix of impurities – arsenic and boron – and a means to get the electricity out of the cell. The PV cell then burst on the planet in April 1954. Given that it had an efficiency of around 6% and was incredibly expensive to produce, the new technology hardly took off, or rather it took off only in satellites funded by the military.

Returning to earth, ARCO – Atlantic Richfield – established a solar division and concentrated on two power plants in California of respectively 1 and 6 MW in 1982-3. Given the cost, the mental mindset saw PV technology as primarily about a substitution for standard fossil fuel power plant feeding the grid. As such, their California plants shifted their panels to face the sun. (At the same time and with the same mindset, the US Department of Energy was using a huge number of mirrors to focus the sun to heat steam to run turbines, with the obvious drawback that this took up an enormous amount of space in an area obviously dangerous to humans.) It was via Arco Solar that BP got involved with PV.

By this time, PVs had reached an efficiency of around 20%. It took some experimentation with different ‘impurities’ notably gallium, iridium and phosphates and another decade to shift this efficiency above 30% and then some. It was the Japanese who first settled on the idea that solar could be used on ordinary houses as a form of electricity that did not depend on the grid, rather than putting them on skyscrapers as a form of public relations, in 1994. Germany soon followed with a “100,000 solar roofs project” in 1999 at a cost to the state of $500 million.

Since then, the growth of solar power in Germany has expanded enormously, reaching 7.9 GWs of capacity in 2022 and generating 58 TWh, or 12.1% of German electricity. From April to August last year, solar generated more power than the lignite coal, on which Germany relies for its baseload. This was a record year for sunshine and compared to 48.45 TWh in 2021 (9.9%). Significantly however, the Germans kickstarted the whole process by a very high feed-in tariff, which has subsequently fallen because of its high impact on electricity charges.

The Japanese followed. They started out putting panels on mountainsides in the usual big idea for utility operation, but rapidly realised that roof-top panels would be less intrusive and unleashed a subsidised tariff for electricity fed into the grid. This mechanism had a rapid effect and the 2030 target for 53 GW of solar capacity was overshot in 2018 and solar now accounts for around 7% of Japanese power production. The state increased its tariffs to Y42 per kWh in 2012 with predictable result but has now lowered them to Y12. Yet it still aims to get its solar capacity up to 14-16% per year with an additional 4 GW of capacity added each year. The country has calculated that it has over 7,500 square kilometres of rooftops, ripe for the panels, with panels going on 79% of new homes.

Also ahead of the game were the Chinese, having started PV research as early as 1958 with monocrystalline silicon. As usual, the early stuff was for satellites, but started to really take-off around 2001, with the creation of Suntech Power, which is now one of the largest manufacturers of cells in the world, having overtaken Germany in 2015. Having only 3.3 MW of terrestrial capacity in 2000, the country hit 20.3 MW by 2002, rose to 100 GW by 2015 and is now over 300 GW. Significantly a great deal of this capacity is in the west in the lesser populated areas, so the Chinese are unafraid of shifting the power long distances to reach demand.

India too has accelerated its use of solar. With a target of 20 GW by 2022, it overshot this in 2018. The new target of 100 GW is now in sight, having reached 60 GW in 2021. In particular, lead by Norendra Modi’s government, there has been much emphasis on rural areas in substitution for the widespread use of kerosene for lighting and cooking. India is the leader of the International Solar Alliance of 105 countries, largely between the Tropics of Cancer and Capricorn, and has used this alliance as a means to put pressure on the World Bank for funds.

Perhaps more surprisingly, the Saudis are currently planning to use the latest “economic windfall” caused by the effect of the war in Ukraine on oil prices to build the biggest ever solar power plant at Al Shuaibah, near Mecca, by the end of 2025. Rated at 2,060 MW, this will join the 15 GW now under planning, with the aim of hitting 40 GW by 2030. Somewhere deep in the recesses of the Saudi government, the realisation has struck that their oil receipts are not going to go on for ever and few places on the planet have access to so much sunshine.

The same is true of Algeria, with some 3,000 hours of sunshine a year. There is now a 60 MW plant at El Kheneg, while Oran’s new airport now has 4,500 panels on its roof. The aim is to get to at least 15 GWs by 2035. As pointed out in the country’s Nationally Determined Contribution (NDC) for the UN Convention on Climate Change, Algeria is particularly vulnerable to increased desertification and an exodus of rural population as a result. Given its extensive land area on the Sahara, the country puts its “solar deposit” at around 5 billion GWh a year. It needs a great deal of help to remotely get anywhere near this, but its government is equally well aware that if Europe goes down a green hydrogen fuel route, it will need a lot of power, not to mention water.

Both Saudi Arabia and Algeria are examples of places were the economic fallout of a shift away from hydrocarbon fuels can be mitigated by solar power. Clearly however, the sun does not shine everywhere and has an irritating habit of shining more in summer than in winter and during the day rather than the night. In short, it shines when we least need heating and light.

Naturally, given that the sun shines for 24 hours during the Arctic summer and does not shine at all during the Antarctic winter and vice-versa, there is clearly a need for an electrical connection between the two, should tourism really start to take off in either region! This is, of course, an absurdity. In fact, Antarctica has a particularly low level of sunshine that is not related to its global position. Equally anybody who has been in the Arctic in September will have observed sunsets that go on for days and nights on end.

But the shifting around of solar produced electricity certainly isn’t an absurdity. It is merely an irony that Germany is such a leader in the technology, because it has one of the lowest solar radiation levels on mainland Europe. This however should not be regarded as discouraging because even with the distinction in radiation between Hamburg and Munich, German solar power can and does replace a lot of coal-fired power in summer.

On the contrary, detailed work on global solar radiation reveals just how much could be available, if only it was not just about money. In this context, it is surprising that Australians did not wake to solar power until around 2017, given that the country has around 2.3 kWh per cubic metre of photons raining on it. This is one of the highest levels outside southern California in the developed world. The country now has 16.5 GW of capacity and cells on some two million homes and they are finally taking off, with some eight retailers in Alice Springs alone. Ironically, Sydney, Melbourne and Canberra have lower levels of radiation, but it is still a lot higher than Germany’s.

In fact, the only areas of Europe with a similar resource are southern Turkey and southern Spain. Like Australians, the Spanish have been a little slow in realising their advantage, but are now forging ahead, with 19 GW planned for the next three years. Matters in Turkey, at least at the household level, are complicated by the government subsidy on electricity. This gives non-utility solar a very long payback period. That said, the country now has its own manufacturing capability.

Elsewhere in the world, Egypt is finally waking up to its potential, although Yemen has other matters to think about. Oddly enough, the country with by far the greatest potential for the production of solar electricity in Africa is Namibia, but it is rather a long way from any perceived demand. Overall however, there is very little doubt that our capacity to produce power from the sun is available on three quarters of the planet and that we have the technology to produce it in ways that can only get better.

Yet as sceptics will point out, solar power fluctuates, delivers when demand is often at its lowest and arrives in sufficiently small quantities to make it not worth transporting. But there are several arguments that mitigate these defects. Regarding fluctuation, battery technologies have improved beyond recognition in recent years. Equally the transference of power from nation to nation – certainly within Europe – has been going on for decades. If it makes sense to transfer billions of cubic metres of natural gas for thousands of miles across the tundra of Russia to the kitchens of Germany, or under the Mediterranean from Algeria to Italy, it should not be beyond the wit of man to do the same with power down a DC wire.

It is difficult to not to be optimistic about the growing use of solar power. The meteorological world is full of scientists calculating the amount of global sunlight in strange places and using the notation ‘kWh per square metre’. The US Department of Energy’s assessment of the sun’s capacity to supply our needs is not perhaps as useless as it might sound. After all, the hydrocarbons that we now need to leave in the ground, were the product of that ‘global warming’ over eons of geological time.

Besides, there is something very democratic about rooftop power generation. It adds very little to the cost of newly built houses and it gives the owners not merely a way of providing their own electricity, but allows them to contribute, just a little,  to the well-being of all.