Often seen or touted as idealistic, zero-carbon cities are now seen as an obtainable goal by most local elected officials and becoming a goal of many cities across the world. Reaching net-zero emissions is considered a necessity for the future of the environment with many cities across the country currently working towards the goal of zero-carbon emissions, including Boston, Denver and Portland, Oregon, which all have committed to reducing Energy use by 80% or more by 2050. While each city has a very different story featuring examples of success and failure on their journey to net-zero, it’s important to consider all the perspectives when analyzing the case studies of these cities — including cultural and economic influences as well as all the energies and materials involved.

Are “100% Renewable” and “Zero-Carbon” the Same Thing?

Dozens of cities are responding to climate change threats and the pollution problems associated with burning fossil fuels by setting ambitious goals to become either 100% Renewable or zero-carbon.

Both goals are essential if we’re going to avert the environmental crises caused by burning coal, oil and natural gas. However, they are the exact the same thing.

Renewable energy is all about inputs — the types of energy a city uses to power its buildings, neighborhoods, institutions and infrastructure.

This type of energy is infinitely available because its source is unlimited. Cities that have set a goal of being powered 100% by renewables want to switch from coal, oil and natural gas to solar, wind and, in some cases, hydropower and geothermal.

While the primary driver behind using renewable energy may be to stop climate change, using renewables offers many other benefits as well. For example, solar and wind create none of the air and water pollution that burning coal and oil do, nor do they create radioactive waste like nuclear power plants. Renewable energy provides independence from foreign oil suppliers. Rather than sending energy dollars overseas to multinational corporations, renewable energy keeps money in the local community. The renewable energy industry is also the fastest generator of jobs in the energy sector, providing far and away more local employment than any other energy supply.

Unlike renewable energy, zero-carbon focuses on outputs — specifically the CO2 that is released as a result of burning coal, oil or natural gas. Zero-carbon centers around the goal of eliminating these emissions.

A city can’t get to zero-carbon without switching to 100% renewable energy. Switching to 100% renewable energy has many benefits, including but not limited to, creating a zero-carbon economy. 

What Are Some Sources of Renewable Energy?

The two primary sources of renewable energy are solar power and wind.

Photovoltaic cells convert sunlight into electricity. They can be mounted on rooftops, on the ground in solar arrays, and on top of charging stations, light posts, and other devices. They can also charge storage batteries that can be tapped at night or on cloudy days to provide an uninterrupted energy supply. Solar hot water heaters do exactly that: capture sunlight to heat hot water. “Passive” solar designs enable residences and buildings to use the sun’s heat to warm a space during the day and store radiant energy to release in the evening.

Wind power is generated by wind turbines that have propeller-like blades that spin around a rotor connected to a shaft. When the wind blows, the blades spin the rotor and the attached shaft spins a generator to create electricity. Wind power is currently the fastest-growing source of energy in the world.

Hydropower generated when water flows through dams also creates renewable electricity, but because dams can have such a significant negative environmental impact on fisheries and the surrounding ecosystem, the federal government along with many state governments don’t include hydropower in their calculations on how to expand renewable energy resources.

Geothermal energy taps into the heat emitted by the Earth’s core. Almost everywhere across the U.S., the upper 10 feet of the Earth’s surface maintains a nearly constant temperature of between 50 and 60 degrees Fahrenheit. Geothermal or “ground source” heat pumps tap into this resource to heat and cool buildings.

The process of harnessing ocean tides is just starting to be developed and could become another important source of renewable energy in the future.

What Are Some Methods Cities Are Using to Get to 100% Renewable?

Cities are increasing their supply of renewable energy primarily by replacing coal and oil with wind and solar. In addition to powering city-owned facilities, buildings, and street and traffic lights with renewables, cities are replacing gasoline-powered fleet vehicles with those that run on clean electricity and installing fast charging stations to encourage residents and businesses to buy electric vehicles along with offering tax incentives, buying programs and educational workshops to make it easier and more affordable to convert to solar. Three American cities already use 100% renewable energy with an additional seven planning to join them by 2040.

What Are Some Methods Cities Are Using to Get to Zero-Carbon?

There are three ways to get to zero carbon:

Waste less energy. The Lawrence Livermore National Laboratory estimates that the U.S. economy is just 39-percent energy efficient. In other words, the U.S. is wasting 61 percent of all energy put into its economy. That’s why getting to zero-carbon must start with energy efficiency. Using highly efficient LED lights, ENERGY STAR-certified appliances and readily available “smart” technologies like programmable thermostats and HVAC systems all have a critical role to play. Insulating and weatherizing existing homes and buildings along with building highly energy efficient new construction is also essential.

Meet energy demands with clean, renewable, non-fossil fuel energy sources. Newbuildings.org has compiled this very helpful description of efforts cities are making to “get to zero,” along with a list of 400 net-zero energy buildings that “have a target or outcome of ultra-low energy use that can be supplied through onsite renewable generation.”

Absorb CO2 already in the atmosphere. Even if we stop generating carbon dioxide today, damaging CO2 will remain in the atmosphere for decades to come. Cities are tackling this problem locally by reforesting city streets since foliage helps absorb CO2 while purifying the air and also helping to create shade that reduces energy intensive air conditioning needs. 

The Role of LED Lighting

One of the cheapest and easiest ways to limit carbon emissions and the waste of energy is the reduction of the demand for energy and carbon. When looking at a singular building in a city, for instance, making it carbon-free and energy efficient would mean planning it as such in the preliminary stages. From large windows with sun louvers to thick walls with good insulation to sinks with taps that have a reduced flow, there are so many solutions to reduce energy expenses and carbon emissions.

One of the most effective and successful ways is the use of LED lighting. LED, which stands for “light emitting diode,” uses almost 85% less energy than regular halogen lighting. The way they produce light is through the use of a semi-conductor that releases energy when electricity goes through it.

Using exclusively LED lighting in cities that plan to reach the zero-carbon footprint is essential as it solves one of the main issues related to the citizens’ everyday use of energy. It’s interesting to note that LED lights are a central element in all cities that have attempted to reach the carbon-free goal, as it’s the cheapest and most efficient way to produce light, whether for private homes, advertising, screens or public use.

Carbon-Free Cities 

After having considered what potential carbon-free cities have in common, it is important to understand why some of these are considered successful and others considered failures. Masdar in the United Arab Emirates was planned in 2006 and aimed to be a home for about 50,000 people. Designed by the multinational Foster and Partners, the city was supposed to have no cars with its means of transportation being driverless electric shuttles between buildings created with technologies that would’ve allowed them to resist the heat of the desert. While it may have failed its initial objective, it’s still functioning as a modern city with plan for a renewable future.

Dongtan, which is located on the island of Chongming in Shanghai, China, on the whole has been considered a failure of a potentially carbon-free city. Planned to open in 2010 for the Shanghai World Expo with accommodation for 10,000 people, Dongtan’s planners were thinking big. The metropolis was supposed to reach a population of 500,000 by 2050. The project, unfortunately, is still a project, and there has been no construction work so far. The city is still planning to be built, with promises of 66% less energy consumed by every building, which will be ventilated naturally and feature green roofs. Whether the city will be built or not in the next few years is not yet confirmed.

Here in the U.S., several cities have transitioned to 100% renewable energy:

• Burlington, Vermont, in 2014, population 42,260, uses a combination of hydroelectric power and four wind turbines.
• Aspen, Colorado, in 2015, population 6,871, is now using a city-owned utility company, which utilizes wind power, solar power and geothermal heat.
• Greensburg, Kansas, in 2016, population 771, took the opportunity to rebuild to become completely renewable after a devastating tornado leveled their town in 2007.
• Las Vegas, Nevada, in 2016, population 632,900, uses clean energy for all of their municipal buildings. No, the casinos aren’t under this current setup.

Failing the initial objective of no emissions at all can be seen as a defeat. Considering affordability and quality of life in these ecological, emission-free cities is a must, and it should not be overlooked. Eco-cities are not only an architectural work, as the concept of a city itself is something much more elaborate, which must take into consideration its inhabitants, businesses, economy, culture and resources.

The concept of building an entire city from scratch, to this end, might be the issue in the very first place. The idea that creating is superior to improving something existent is not only wrong, but dangerous for the percentage of the population that is living in non-ecological conditions that are dangerous to humans as well as the environment. The idea of building something new and luxurious that’s also ecological and has zero-carbon emissions is almost utopian sounding. Combining reduced carbon emissions with projects of new cities or neighborhoods might be the solution to the failures of zero-carbon cities.

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