A 2011 study by Stanford University Professor Mark Jacobson and Mark Delucchi stated that it was entirely possible to move to 100% renewable energy supply globally. They articulated their vision based on a conviction that it is feasible to generate all new energy with renewables by 2030
They further added that all existing energy generation arrangements could be replaced with renewable sources by 2050. All this could be achieved at no additional energy costs compared to those today. They felt that all technological and cost barriers are being dismantled and no more present any obstacle to the achievement of this goal.
Given the rapid environmental degradation and the forecast of catastrophic outcomes of climate change, there is heightened dependence on renewables and technological breakthroughs have enabled meet targets well ahead of time. Historically too, before the advent of fossil fuels, the world has run of renewable energy-water power and wind power-wind to power ships over water and to power windmills to crush grains and lift water. It seems we are rapidly moving towards the safe and benign practices of our forefathers. The REN 21 Report states that in 2014 renewables contributed 19.2 per cent of human energy needs and in 2015 such sources accounted for nearly 24 percent of electricity generation. Developed and developing nations are making commitments to significantly scale up the composition of renewables in their energy baskets over shorter time frames.
Some 120 countries have various policy targets for longer-term shares of renewable energy, including a 20 per cent target of all electricity generated for the European Union by 2020. Outside Europe many countries have targeted renewable energy shares of between 10 and 50 per cent by 2020-2030. Some are even targeting 100 per cent.
Renewables for power generation and automobiles
Renewable energy flows involve the harnessing of natural phenomena such as sunlight, wind, river water, tides, plant growth, and geothermal heat. Application of renewable energy technologies is found most commonly in power generation (including for heating) and the automotive sector. Achievements of some countries particularly in power generation are noteworthy. In 2015 wind power met 42 per cent of electricity demand in Denmark, 23.2 per cent in Portugal and 15.5 per cent in Uruguay. By 2040 the global electricity generation using renewables is likely to equal that of coal and gas. As regards heating, it is estimated that rooftop and other solar devices heat up nearly 70 million households of which China itself accounts for over 50 million. Bioethanol is used as an additive to petrol and diesel to power automobiles. Brazil has achieved noteworthy success in such blending. In India there are plans to jack up ethanol blending in petrol to 22.5 per cent and in diesel to 15 per cent. This reduces the dependence on imports of crude while producing marked reduction in carbon monoxide and other emissions. Solar energy is now being used in automotive applications. While road running solar operated vehicles are not yet practical commercially, solar powered boats are produced for commercial use.
Mainstream renewables
Among the most popular and the oldest of renewables is wind power. Windgenerated electricity met nearly 4 per cent of global electricity demand in 2015. In India too, wind has the lion’s share of 56 per cent in the current renewable mix of about 50 GW. Rapid technological advances in the field have enabled squeeze out more power even from low wind intensity sites. Rotor diameters, for example, now exceed 100 metres and tower heights 120 metres. Another development is the offshore wind farms, where wind speeds are much higher than land and with little issues of land acquisition or opposition by local communities. Wind power is however hampered by low yields, usually 20 to 50 per cent.
Solar photovoltaic (PV) is the process of converting light energy from the sun into electrical energy using solar panels made up of solar cells. The solar panels may be either small standalone individual ones mounted on buildings including homes or in the form of large arrays at a solar farm feeding into a grid. Then we have solar thermal which directly uses the heat of the sun as in solar cookers or roof top water heaters.
Large Hydro electric power has played an important part in India’s energy landscape. As of September 2015 share of large hydro in India’s energy basket was 43 GW, about the same as renewables 44 GW. Hydro power projects while having good potential in India given the number of perennial rivers and the Himalayan system, face significant delays due to environment concerns. In addition they have large gestation periods.
Not yet mainstream: Concentrated solar power
It is among the technologies which are yet not prevalent for large scale commercial application. CSP involves the use of solar energy (heat) by concentrating the beam of sunlight from a large area into a smaller area thereby creating intense heat. CSP uses various devices to achieve the concentration of the light, most commonly a parabolic trough. The heat is then used to boil water in pipes, generate steam and run steam turbines to generate electricity.
Spain is a front runner in CSP technology with a total installed capacity of 2300 MW in 2014. The USA which houses the world’s largest facility had about 1750 MW. The Middle East, notably Abu Dhabi is making good progress. While the share of CSP is low at just 2% of solar power, some studies state that it has potential to meet 25% of the world energy needs by 2050. Cost is an obstacle. While the CSP cost was similar to solar PV some years ago, rapid reduction in PV costs in recent years have made CSP seem unattractive. In some quarters there are environmental concerns too. Findings suggest that birds could be singed (burned) due to the intense heat if they were to fly close to the line of heat.
Geothermal energy
This method uses the immense heat trapped in the core of the earth beneath the surface. This is done by drilling into the surface of the earth’s surface and extracting the hot water in aquifers. Once the pressure is released this hot water comes above the surface in the form of steam akin to a hot spring geyser, which is then used to drive turbines of a power generator. The steam then condenses to water which could be injected back into the earth to charge the aquifers. In cases where such hot water does not exist, two bore wells are drilled. Through one, water is injected into the earth. There due to the high temperature, it turns into steam and emerges through the other bore to drive the turbine. The steam later condenses to water and is injected back.
In 2015, the global geothermal capacity was 12.8 GW with the USA having the largest share at 28%. In terms of economics, while the fuel cost is zero, the technology involves substantial capital expenditure, mainly in the form of drilling costs. Most drilling is within the range of 3 to 4 kms but some larger depths have also been attained at much higher cost. Therefore exploitation of geothermal energy could be feasible in locations with favourable geological characteristics, where high temperatures exist closer to the earth’s surface. On the environment front Geothermal energy is considered friendly since it generates just about 45 Kg of CO2 equivalent per MW hr as against 1000 Kg for a coal fired plant. In addition to some Greenhouse gas emissions which escape from the earth, there could be some harmful chemicals. In addition, these have been instances of seismic imbalance and even earthquakes resulting from the drilling activity.
Marine energy
Given that 70 per cent of the earth’s surface is comprised of oceans and there is enormous amount of energy contained in the sea waters, these present great opportunities for development of clean, renewable energy. Significant amount of work is happening in sectors such as wave energy and tidal power. However, many of these technologies are yet to move beyond the demonstration devices stage towards commercial application. There are environment concerns here too. The noise from equipment and presence of physical structures, wires and cables underwater could pose dangers for marine organisms and the ecosystem.
As is apparent there are a number of presently viable technologies which are in commercial use and many emerging ones which hold great promise. Rapid depletion of finite fossil fuel reserves and growing concerns for the environment will enable quick commercialization of all these technologies and development of new ones. We have no choice but to move towards 100 percent renewable energy if mankind and this
planet are to survive beyond a few centuries more.