In order to slow down climate change, it is essential to focus on renewable energies, starting with solar energy. At the moment, over 70% of global carbon emissions may be attributed to the production and use of energy, and that is why our first commitment must be to use green sources for our energy supplies. The Paris Agreement, which aims to limit the increase in average global temperatures to 1.5 degrees, has set in motion an international system to change the production of energy: IRENA – the International Renewable Energy Agency – has for its part specified that to achieve this objective it is necessary to reduce global carbon emissions by 2050.
So for the next few years, we will need a greater supply of electricity, which should be produced almost entirely from renewable sources. More specifically, we are looking at a threshold of 70,800 TWh/yr by 2050, at least 90% of which should be produced by renewable sources. As has often been pointed out, the key player here, because of the advantages which we will look at shortly, is undoubtedly solar energy, and more specifically photovoltaic solar energy.
It should be stressed that this change of pace must be achieved as soon as possible, irrespective of the climate change that is currently underway: we cannot ignore the fact that fossil-based resources such as coal, oil and gas are running out. In addition to causing serious harm to the environment, fossil fuels take very long periods of time to form; green energies, on the other hand, are renewable. As we shall see in the following paragraphs, the best way forward is to integrate solar energy production into infrastructure, thus dispensing with the need for harmful use of land.
Solar energy: definition and types
The general term solar energy refers to any type of energy produced from the rays of the sun. This is a clean and inexhaustible source of energy, that can be exploited without any impact on the environment. With solar energy, solar rays are used to produce two distinct products: electrical energy and thermal energy. More specifically, there are three different types of solar energy: solar photovoltaic, solar thermal and solar thermodynamic.
Solar photovoltaic is a system that uses a skilful arrangement of photovoltaic panels to convert solar energy into electricity, in a clean and instantaneous way. This is possible thanks to the presence of solar cells, used since the 1970s to supply devices such as artificial satellites and remote telecommunications networks. A solar photovoltaic plant consists of the following: modules or panels that comprise the photovoltaic cells, distributed in parallel rows and connected in series; the support structure for the modules; the inverter, that converts the current from direct to alternating current; and finally the electric cables, energy meters and control system.
Solar thermal energy on the other hand is a system that produces thermal energy rather than electricity. Instead of cells, it consists of solar collectors. The solar rays heat the liquid inside the collector, and the heat is then harnessed and transferred into the pre-arranged locations.
Solar thermodynamic power is different again. Here too, it involves the creation of heat without using fossil fuels, but in a different way. Solar thermodynamic power uses the atmospheric heat (so it can generally be installed at any point outside a building) to heat a building’s domestic water supply; in contrast with solar thermal energy – which does not use any type of energy other than the sun’s rays – thermodynamic solar power requires a heat pump. It should be said, though, that the same heat that is present in the system is used to produce steam, which in turn, through the use of a steam turbine, is transformed into electrical energy.
Why integrate solar energy into infrastructure?
We saw at the beginning that it is essential to increase sources of solar energy, in order to quickly reduce harmful emissions. But how can this shift be translated into reality? It would be a mistake to think that this energy transition should take place simply through replacing thermal power stations. If we look at the objectives of the Italian Integrated Energy and Climate Plan (PNIEC) and the European Green Deal, we see that by 2030 we should have at least 100 TW/h of electricity produced by photovoltaics, four times that of 2020; if this quantity of energy were produced entirely from plants on the ground, we would have to have a dedicated surface area of about 1,000 square kilometres, an area equivalent to 5% of the land use in Italy.
Unlike wind or hydroelectric power, photovoltaic energy has the advantage of being able to be integrated into buildings and infrastructure of any kind and size, and hence without using any more land. Buildings represent about 30% of land use, and consume 40% of the world’s energy: it is clear therefore that being able to generate solar energy on site is doubly successful, in that it makes it possible to have zero-energy buildings (or even buildings that supply energy to the outside) without taking up land. And this is possible with any type of building. Take the Stavros Niarchos Foundation Cultural Centre, for example, designed by Renzo Piano and built in Athens by the Salini Impregilo company: the Energy Canopy comprises a total of 5,560 photovoltaic panels that can generate 2,280 Kwh of electricity a year, making it almost entirely energy-independent. It is no surprise that the Centre has achieved the highest level of LEED certification, that is, LEED Platinum. But there is also the Sol Invictus in Melbourne, the Apple Spaceship in Cupertino and General Electric’s Solar Veil in Boston: all of these projects show how the integration of solar energy in buildings and infrastructure is the key to energy change for today and tomorrow.
Solar energy: advantages and disadvantage
Solar energy offers many different advantages. It is a clean, low-cost and inexhaustible energy, and, as we have seen, it can also be autoproduced, at a price that should come down over time. There are basically two disadvantages: it is a discontinuous source, since it cannot produce solar energy during the night or on cloudy days (a problem that could be resolved with the use of accumulators, however); and it is an energy that requires space to position the panels (although we have seen that integrating them into buildings makes it possible to use this energy source without taking up more land).