Academic Reading — Test 179

Reading passage

The idea of harnessing the sun's energy is far from new. Ancient civilisations positioned their buildings to capture warmth during cold seasons, and used polished metal surfaces to concentrate light for cooking and even for igniting fires. Yet the conversion of sunlight directly into electricity began only in the nineteenth century. In 1839, a young French physicist named Edmond Becquerel observed that certain materials produced a small electric current when exposed to light, a phenomenon later termed the photovoltaic effect. For several decades this discovery remained little more than a scientific curiosity, because no one could explain why it occurred or put it to any practical use. The situation changed dramatically in the middle of the twentieth century. In 1954, researchers working at Bell Laboratories in the United States built the first silicon solar cell capable of producing a useful amount of power. Their device converted roughly six per cent of the sunlight that struck it into electricity, a figure that seems modest today but represented an enormous leap forward at the time. The breakthrough attracted immediate attention from the emerging space industry, which urgently needed a lightweight, durable source of energy for satellites orbiting far from any conventional power supply. Solar panels proved ideal for this role, and within a few years they were powering spacecraft. Space, rather than the ground, thus became the first significant market for the technology. On Earth, however, progress was slow, largely because the cells were extraordinarily expensive. During the 1950s and 1960s, the cost of solar electricity was hundreds of times greater than that generated by coal or oil, which confined its use to specialised situations where no cheaper alternative existed, such as remote lighthouses, telecommunications stations and scientific instruments in isolated locations. The oil crises of the 1970s changed public attitudes considerably. As fuel prices climbed and supplies became uncertain, governments began to fund research into renewable sources of energy, and solar power received a share of this new investment. Manufacturing techniques improved, and the price of panels started a long and steady decline that has continued ever since. The most striking feature of solar power's recent history has been the speed of this fall in cost. Between 2010 and 2020, the price of solar modules dropped by close to ninety per cent, transforming the economics of the technology. Several factors combined to produce this result. Economies of scale played a central part, as factories grew larger and produced panels in ever greater quantities. Efficiency also improved, so that modern commercial panels convert around twenty per cent of incoming sunlight into electricity, with the best laboratory cells achieving considerably more. Government subsidies in countries such as Germany and later China created stable demand, encouraging manufacturers to expand. China in particular came to dominate global production, building vast factories that drove prices down further still. Despite these advances, solar power faces genuine limitations. The most obvious is that it generates electricity only when the sun is shining, producing nothing at night and far less under cloud or in winter. This variability, often called intermittency, makes it difficult to rely on solar power alone to meet demand around the clock. The usual response is to store surplus daytime energy in batteries for use after dark, but until recently batteries were too costly to deploy on a large scale. Their prices have now fallen sharply as well, partly because the same factories that supply electric vehicles also produce storage for the grid. An alternative approach is to connect distant regions with long transmission lines, so that areas still in daylight can supply those where the sun has set, though such networks require considerable cooperation between nations. Looking ahead, researchers are pursuing materials that could push efficiency higher and costs lower. One promising family of compounds, known as perovskites, can be manufactured at low temperatures and may eventually be printed onto flexible surfaces or layered on top of conventional silicon to capture a wider range of the spectrum. Questions about their long-term durability remain unresolved, however, and most experts caution that they are not yet ready for widespread commercial use. What seems clear is that solar power, once an expensive novelty restricted to satellites and remote outposts, has become one of the cheapest sources of new electricity in much of the world, and its share of global generation is expected to keep rising for decades to come.