Renewable energy is at the core of transitioning to a more sustainable energy system. A greater use of innovative renewable energy technologies – while promoting less carbon-intensive energy consumption – is key to addressing future pressures on the energy system, addressing climate change mitigation, and creating more resilient economies.
In practice, ensuring universal access to modern energy and de-carbonising energy systems to meet the climate objectives of the Paris Agreement are mutually supportive goals, and hence ought to be advanced at the same time. SDG7 therefore calls for increasing electrification and greater access to clean fuels, in tandem with boosting the share of renewable resources in energy consumption and improving the rate of energy efficiency.
This integrated approach simultaneously meets the aims of SDG13, by helping to combat climate change and its impacts. In particular, renewable energy and energy efficiency have a joint potential to achieve 90% of the emissions reductions required by 2050, thus contributing greatly to climate change mitigation.
Additionally, increasing the share of renewable energy promotes the diversification of the power supply, thereby contributing to the resilience of energy systems. At the same time, climate action has knock-on developmental impacts, improving energy access and making energy systems more climate resilient.
A shift from carbon-intensive energy sources towards renewable energy is feasible both economically and technically. Although progress has been made in de-carbonisation, it falls significantly short of what is needed to meet Paris Agreement targets. This is due to slow growth of renewable energy in total final energy consumption (TFEC), coupled with the slow pace of phasing out of fossil fuels from TFEC (in 2016, more than 80% still came from fossil fuels).
As well as transforming the energy generation sector itself, a key challenge is to increase the share of renewable energy in end-use sectors. For example, heat and transport jointly account for 80% of global energy consumption, yet renewables make up less than 10% and 5% of their TFEC, respectively.
Increasing energy access across the globe without carefully considering the choices around energy resources used could also be detrimental. Energy produced by the combustion of traditional fossil fuels has a negative impact on human health while contributing to climate change – which could undo the environmental, social and economic progress made so far.
Therefore, shifting away from high-carbon fossil fuels to low-carbon energy sources on the one hand, and promoting less carbon-intensive energy consumption in end-use sectors (such as buildings, manufacturing, and transport) on the other, can significantly contribute to de-carbonising the energy system, addressing climate change mitigation, and creating more resilient economies.
Additionally, using more renewable energy produced locally can reduce dependence on imported energy sources – thereby improving regional energy security, making energy systems more resilient, and energy access more affordable. To help address future pressures on the energy system, innovation in energy technologies remains crucial.
Technologies for a renewable future
A truly sustainable renewables-based future requires a mix of energy sources (wind, solar, geothermal, hydro) and technology designs (on- and off-shore wind, solar PV and CSP, plug-in and battery electric vehicles), to avoid technology lock-in. The mining sector is expected to play a key role in providing materials to manufacture technological solutions for a low-carbon culture.
Hydroelectric power is the largest single renewable electricity source, dominating the electricity mix globally. Hydroelectric power plants capture the kinetic energy of river water, which flows into and accumulates within a dam. Water then moves through a pipe (penstock) from high to low altitude, feeding into a turbine house, where it turns the blades of a turbine to spin a generator and produce electricity (converting hydraulic energy into mechanical, and then electrical, energy). Construction materials for power plants must withstand wear and tear while resisting cavitation erosion, and corrosion. The base of dams is typically made of inexpensive rock, sand, or gravel. The dam itself is built of reinforced concrete, while penstock can be made from steel or reinforced concrete, ductile iron, asbestos cement, and fibre-reinforced composites. Steel is also used in hydraulic turbines, due to its cavitation resistance.
Wind turbine technologies convert kinetic energy from wind into electrical energy. Today, they come in different sizes and are used in different settings, ranging from the smallest designs powering street signs and signals, through medium-sized models powering buildings off-grid, to large turbines in off-shore wind parks, connected to the centralised energy grid. These are usually three-bladed turbines, mounted on towers made of either low-alloyed steel galvanised with zinc, or aluminium-based alloys, and a foundation of steel-reinforced concrete. The rotor comprises blades made of fibreglass, a cast iron hub (connecting blades to the nacelle – a housing for the generating components, including the generator, gearbox, drive train, and brake assembly) and stainless steel extenders (securing blades to the hub). The nacelle is made from stainless steel and fibreglass, housing mechanical components made of cast iron, chromium steel and low-alloyed steel. Generators additionally require aluminium and copper, while aluminium, lead, copper, tin, low-alloyed steel, high density polyethylene, polypropylene and polyvinylchloride are used for the electronic components and mains connection. Other metals used in wind turbines include manganese, nickel, cobalt, and molybdenum, while gearless models require additional metals – mainly rare earths (neodymium, praseodymium and dysprosium) and lead.
Photovoltaic solar panels
A photovoltaic (PV) system supplies solar power by means of solar panels, which absorb and convert sunlight into electricity using semiconducting materials. It’s now one of the fastest growing renewable energy technologies – used for both on-grid and off-grid power generation, and as both large-scale ground-mounted installations and small-scale rooftop systems. Metals used for solar panel construction vary, but the most used design (crystalline silicon, or first-generation solar cells) is manufactured using metals such as silicon, aluminium, iron, lead, nickel, and silver. The more recently developed thin film technology (or second-generation solar cells) involves depositing a thin layer of photovoltaic material onto glass, plastic or metal, allowing for thinner, lighter, more efficient and less costly panels. Depending on the design, these can be made of copper, zinc, cadmium and tellurium (CdTe), copper, indium, gallium, selenium (CIGS), or zinc (amorphous silicon).
Concentrated solar power
Besides PV, another technology used to generate electricity from solar power is concentrated solar power (CSP) – which tends to be more reliable and consistent than solar PV technology in terms of power output, although it can be more a more expensive process. The most common types of CSP tech are parabolic trough, solar power tower, and dish Sterling engine systems. CSP converts sunlight into heat using mirrors, with tracking systems, made of metallic reflective coatings deposited onto very high-performance low iron float glass (or alternatively silvered polymer reflectors, glass fibre reinforced polyester sandwiches, or aluminised reflectors) to concentrate large area of sunlight onto a small area. This is then used to produce steam, which in turn is used in steam-turbine generators to produce electricity (solar thermoelectricity). Additionally, the waste heat from steam turbines may be used to desalinate sea water.
Geothermal energy is thermal energy emitted from the Earth’s core to the upper crust. Geothermal heat is extracted by ground source heat pumps (GSHP) via through two drilled wells. One well pumps water into a heated area of rock, while the other transports it back to the surface. Plants then use the steam from the hot water to drive turbines and generate electricity. Alternatively, the hot water can be extracted directly and distributed to heat buildings. Both techniques are used to great effect in Iceland, where nine out of 10 households enjoy the benefits of geothermal power. During the geothermal process, piping, valves and filters are at risk of corrosion due to the carbon dioxide, hydrogen sulphide, ammonia and chloride present in groundwater. Therefore, the most used materials for their construction are steel and polyethylene, along with other materials that offer high resistance to corrosion from geothermal brine solution, such as nickel and titanium alloys, as well as stainless steels.
The global car market is changing rapidly, with sales of all-electric, hybrid, and plug-in hybrid vehicles expected to reach 1.6 million in 2018. The main materials used in vehicles are steel, aluminium, carbon fibre reinforced polymer (CFRP) and cast iron, while platinum is used in anti-pollution devices. Additionally, electric vehicles are powered by lithium-ion, nickel-metal hydride, or lead-acid batteries. These require lead alloys with small quantities of antimony, calcium, tin and selenium, nickel, rare earths (lanthanum, cerium, neodymium, and praseodymium), cobalt, manganese, aluminium, and lithium. They may use rare earth permanent magnets within their motors (containing neodymium, praseodymium, dysprosium and terbium). Rare earths can also be found in headlights (neodymium), LCD screens (europium, yttrium, cerium), glass and mirrors polishing powder (cerium), as well as in catalytic converters (made of cerium and lanthanum). A growing number of electric vehicles will also require an extended network of charging technology. Materials used in charging stations include aluminium alloys, copper, galvanised and stainless steel, and plastic, while sensors within energy meters are made from steel, brass, aluminium, and magnesium.