Thank heavens for the sun!
We all have a lucky star. The amount of energy produced by this massive stellar performer is almost unimaginable. If the Earth were any closer? … Game over.
The sun radiates more energy than we could possible use– but that energy is spread across the surface of the planet. Capturing that solar energy directly is simple for devices that heat up water (like a solar water heater), or that focus the solar energy to produce a much higher temperature. More modern technologies, like arrays of solar photovoltaic panels, can now capture very large amounts of solar energy and directly convert it into electricity.
As the Earth spins around the sun, the regional differences in atmospheric temperatures produce pressure gradients that cause winds. The winds never stop. In one place or another they are always blowing.
Since the beginning of recorded history, man has figured out how to use the wind to propel a simple boat. And it wasn’t long before the first wind-driven mills were constructed on the Mediterranean islands.
The sun not only generates the wind; it drives the hydrological cycle–evaporating water from the land and the oceans, that is moved by the wind until it is eventually precipitates as rain. Without rain, nothing grows.
The sun’s radiation, the wind, rivers and waterfalls, are the most important sources of renewable energy–because they can be directly harnessed to produce the one form of energy that is indispensable for modern economies–electricity. A source of energy which is renewable is also inexhaustible–unlike fossil fuels which in many regions will eventually run out.
But first there was fire.
Wood was the first fuel to be used by early man. And it is still an important source of energy. As long as the sun shines and rain falls, trees will grow–and men and women will cut them down, and collect the wood for fuel. Over a billion people in the less developed countries have no access to electricity. They have no other fuel except wood–or the charcoal which is made from wood. So trees and other forms of biomass are also a source of renewable energy.
But there’s a catch.
Trees grow slowly, and if you cut them all down at once, you quickly run out of fuel. So biomass is only really renewable, meaning always available as a fuel, if forests are carefully managed so that the supply of wood is extracted and consumed at the same rate at which the trees grow.
There are other sources of energy that are also classified as renewable energy. Geothermal energy draws heat from the high temperatures that exist underground in many regions. Iceland is renowned for the way that geothermal energy is used for generating electricity and for district heating.
New technologies that capture the energy of the tides and waves are also renewable energy technologies. OTEC is another. Ocean Thermal Energy Conversion uses the temperature difference between warm water on the surface of a lake or coastal zone, and cooler water at depth to drive a thermodynamic engine that can produce electricity. But temperatures differences are small and the conversion is inefficient and therefore expensive.
Is renewable energy clean?
Solar energy, wind, and hydropower do not produce any air or water pollution. Some people object to the noise of large wind turbines–and call it noise pollution. But most people don’t have a problem with wind turbines (as long as they’re not too close) and understand the huge advantages of clean renewable electricity.
Renewable energy is generally referred to as clean energy because it is contrasted with the fossil fuels: coal, oil, and natural gas. These sources of energy–which have powered the economies of countries since the industrial revolution– are far from clean. They are the cause of widespread and noxious air and water pollution that has a severe impact on human health. Moreover, one component of that air pollution–carbon dioxide–is the principal cause of global warming. Compared to fossil fuels, renewable sources of energy are totally clean.
But once again there’s a catch. Wood contains carbon–just like the fossil fuels. When it is burned, wood produces carbon dioxide–a greenhouse gas. It is also releases other toxic substances that occur naturally in wood, such as sulfur and mercury.
So biomass is not a clean fuel. It may be renewable but it is not clean–although compared to coal and oil it is generally a better alternative.
Biogas is a special case. A combustible fuel gas generated from the anaerobic digestion of biomass waste, it is a mixture of methane and air. So when burned it produces carbon dioxide. But little else. So it is a relatively clean fuel compared to the fossil fuels. But not as clean as the other sources of renewable energy.
The global transition
A number of countries have moved forcefully to expedite a transition to a low-carbon and even a zero-carbon economy.
A first and absolutely essential step is to phase out coal. The Netherlands, United Kingdom, Finland, France, Italy, and Portugal have committed to closing their coal plants in the coming decade. The movement called Europe Beyond Coal is working hard to facilitate this transition—in association with the Sierra Club’s Beyond Coal campaign .
In 2016, more countries committed to moving away from or phasing out coal from electricity generation. Including Canada and the US State of Oregon .
100 percent clean
Across the USA, over 50 cities, five counties and one state have adopted 100% clean energy goals. Five cites have already met this target: Aspen, Burlington, Greensburg KS, Rock Port MO, and Kodiak Island AK. These five cities generate 100% of their energy from clean, non-polluting, and renewable energy sources.
Universities and schools are powering up on solar energy. By 2019, the University of Hawaii Maui College will be one of the first campuses in the US to generate all of its energy from on-site photovoltaic electricity coupled with battery storage. The entire university network will be 100 % renewable by 2035 and the State has committed to be 100% on renewables by 2045.
The Ready for 100 association, initiated by the US Sierra Club, has issued guidelines for this transition : climate action plans and energy action plans etc.  Another initiative being promoted by the Sierra Club is Mayors for 100% clean energy–190 mayors have signed up to a vision of 100% clean and renewable energy .
Then there is RE 100–a collaborative, global initiative uniting more than 120 influential business committed to consuming 100% renewable electricity, and working to increase the demand and delivery of renewable energy.
At the COP22 meeting in Marrakesh in 2016, representatives from 47 of the world’s most disadvantaged nations pledged to generate all their future energy needs from renewable energy. Members of the Climate Vulnerable Forum (CVF) issued their statement on the last day of the Marrakesh meeting. Dubbed the Marrakesh Vision, the nations pledged that they will “strive to meet 100% domestic renewable energy production as rapidly as possible, while working to end energy poverty and protect water and food security..”
In 2018, the Balearic Islands’ government launched a plan to eliminate greenhouse gas emissions by 2050. New diesel cars are to be taken off the road in Ibiza, Majorca, Menorca and Formenta from 2025, a year in which all street lights are to be replaced by LEDs. Solar panels are to be installed on all buildings with roofs larger than 1000 m2—which includes car parks, hospitals, supermarkets and sports stadiums. Coal is to be totally eliminated and all car hire fleets on the islands will be electric.
Over the course of 2016, 117 countries submitted their first NDCs under the Paris Agreement, and 55 of these countries featured renewable energy targets .
During the same year, the Australian Capital Territory added a new commitment and several other large cities—such as Calgary, Tokyo, Cape Town and New York set significant targets for the transition to renewable energy.  Copenhagen went one step further. As part of the city’s aim to become carbon-neutral by 2025, Copenhagen requires that all flat roofs to be planted with vegetation . Many cities plan to simply ban gasoline and diesel vehicles from the city center.
Fossil fuel subsidies?
Building on international agreement to phase out fossil fuel subsidies—such as the 2009 commitments by the Group of Twenty (G20) and by Asia-Pacific Economic Cooperation (APEC)—by the end of 2016 more than 50 countries had committed to phasing out fossil fuel subsidies. Subsidy reforms were instituted in Angola, Brazil, Dominican Republic, Egypt, Gabon, India, Iran, Kuwait, Nigeria, Qatar, Saudi Arabia, Sierra Leone, Sudan, Thailand, Trinidad & Tobago, Tunisian, Ukraine, Venezuela, and Zambia. However, fossil fuel subsidies are still substantially higher than the subsidies for renewable sources of energy.
There is now a strong and unstoppable groundswell of initiatives aimed at reducing countries’ dependence on fossil fuels and transitioning towards a low carbon economy.
But if the temperatures targets set under the Paris Agreement are to be met, the pace of the great transition to renewable sources of energy has to pick up substantially.
For more more information , check these out these sources:
 Sierra club press release: //www.sierraclub.org/press-release/2017/11/new-coalition-aims-take-europe-beyond-coal
 Global Status Report published by REN21
 See : 100% Commitments in cites, counties & States. Sierra Club: //www.sierrraclub.org/ready-for-100/commitments
 See: Mayors for clean energy. //sierraclub.org/ready-for-100/mayors-for-clean-energy
 See: World’s poorest countries to aim for 100% green energy, at: www.bbc.com/news/science-environment-38028130
 See: Baleriacs launch pioneering plan to phase out emissions, at : //www.theguardian.com/environment/2018/feb/15/baleriacs-launch-pioneering-plan-to-phase-out-emissions.
8] Renewables 2017 Global Status Report. REN21
 Ibid page 26
 See: How do you build a healthy city? Copenhagen reveals its secrets. Accessed at: //www.theguardian.com/environment/2018/feb/11/how-build-healthy-city-copenhagen-reveals-its-secrets-happiness
 Renewables 2017 Global Status Report. REN21 page 29