What is Transit Avoided Carbon?
Every time an individual selects mass transit rather than a private vehicle, there is a significant reduction in greenhouse gas (GHG) emissions. This emission reduction can be quantified, and Transit Avoided Carbon (TAC) is the GHG emissions reduction that results from the use of mass transit.
TAC is calculated by accounting for the operational carbon produced by a transit system net of carbon that is avoided as a result of:
• Mode Shift - Avoided Car Trips
• Land Use - Increased population density due to shorter trips to destinations, trip chaining, and lower car ownership in metropolitan areas
• Congestion Relief - Reduced fossil fuel emissions as a result of reduced congestion
At a basic level, the use of mass transit represents a significantly more carbon efficient option that the use of a private vehicle: high-capacity rail is 7.6x more carbon efficient than SUVs and 5.2x more efficient than individual cars, and full buses are 6.4x more carbon efficient than SUVs and 4.4x more efficient than cars.
Regenerative breaking is an energy recovery mechanism that converts kinetic energy from a decelerating vehicle into power that can be used to help the vehicle re-accelerate or be stored for later use. Regenerative braking was first used in F1 racing; as the car braked heavily in turns a regenerative braking system would absorb the energy and later use it to accelerate the car back to speed. F1 cars using this technology were capable of racing for longer periods between refueling, giving them a significant advantage over their competitor; ultimately, it was banned.
Although completely different modes of transportation, F1 cars and mass transit trains have one thing in common; they frequently brake and reaccelerate. Fortunately, mass transit systems deserve an advantage! As a train pulls into a station, regenerative braking captures the energy of the slowing train. This energy is typically stored in batteries located at the station. Unlike F1 cars, this energy can be put to many uses; help the train that generated the power to accelerate out of the station, help power other trains, or the transit authority can sell the extra power back in the power grid for profit.
Regenerative braking within a mass transit system can produce some significant efficiency and savings statistics. Philadelphia’s Southeastern Pennsylvania Transportation Authority (SEPTA) piloting regenerative braking within their transit system. Early projections indicate the technology could electricity cost by 40 percent and $500k in revenue annually per installation. SEPTA projects that regenerative breaking will save 15.6 million kWh of energy or 6.7 million metric tons of carbon per year.
Unbeknownst to your everyday rider, there are thousand of stoplight style signals in subway tunnels precariously controlling their safe travel. They are lit with inefficient incandescent light bulbs.
Light-Emitting Diodes (LED) met their first practical use in the 1970s in computer displays and calculators. They were an ideal option for small electronics because they were bright enough to clearly display numbers and used very little energy. The available brightness of LEDs has double roughly every 36 months, bring us to today’s technology were they are used in everything from flashlights to large TVs.
Much likely their early use in small electronics, LEDs are a very practical option for subway and train light signals; they produce the required light for their application and use significantly less energy than their incandescent counterpart; 93% less. Beyond reducing energy consumption and cost, there are numerous other benefit to using LEDs:
• LEDs have 42x the normal life of an incandescent light bulb, reducing maintenance cost
• LED signals use many LEB bulbs, so if one fails there are many others that continue to work
Parking structures hold one of the greatest opportunities for energy efficiency because their only real energy cost is lighting. Aside from upgrading light fixtures to high efficiency models and LED lighting, motion detection can be added to gain additional energy saves. Parking structure lighting is typically setup to turn on once it gets dark and then turn off once the sun rises. By adding motion detection, the lighting system can modulate the amount of light needed; keeping the lights at dimmer setting when no one is around and turning them up to full capacity when a person or moving car is present. Adding this technology can making a parking structure 50% more efficient beyond just updating lighting fixtures.
The most cost-effective renewable energy program is a lighting retrofit system. Schools represent an ideal opportunity, since, in the typical school, 40% of the energy use comes from lighting. Lighting retrofits and advanced lighting controls can create substantial reduction in energy use of typically 50-75%, dramatically reducing the lighting cost in the average school.
There are over 97,000 public K-12 schools in the United States, and an additional 25-30,000 private schools. New York City alone has over 1,600 public schools. Schools are large buildings, and retrofitting lighting not only saves money, it also creates a better learning environment.
It’s getting harder to buy your everyday incandescent light bulb from your standard retailer, and most homes at least a few compact fluorescent lights. Compact fluorescent light bulbs are significantly more efficient, using less power while producing equivalent light. Just like your typical household, public buildings and infrastructure have cost effective and environmentally responsible lighting replacement options.
When looking at large infrastructure, updating lighting is one of many options to improve power efficiency and environmental friendliness. Aside from the environmental impact, it can also reduce the cost of running a facility meaning tax revenue can be used for more productive activities.
There are also a myriad of other projects - including the conversion from older heating oil to natural gas, advanced lighting controls, window films, and much more - that can dramatically reduce a building's energy use. Building retrofits accelerate this reduction, saving even more.
Anyone living in urban and suburban areas will recognize the large public transit buses that take people to and from their places of work or even to just the grocery store. As they trolley through our cities and neighborhoods, many people will also recognize their loud grumble, the unforgettable smell of diesel emission, and the black smoke left behind. These qualities are quickly becoming relics of the past.
Much like popular car choices, buses can be purchased with hybrid electric engines. Hybrid electric engines pair a strong electric motor connected to batteries and an efficient combustion engine to power a vehicle. Typically, the electric motor is used to start a vehicle moving forward – the point at which a common combustion is most inefficient. As you can imagine, this technology is best applied in urban environments were traffic is constantly stop-and-go or on vehicles that make frequent stops. The typical hybrid electric bus is 30% cleaner than their all diesel counter part, which means fewer dirty emissions are being released into our neighborhoods.
Looking to the future, technologies beyond hybrid electric are advancing that will eliminate the need for combustion engines. Many transit agencies are looking to adopt fully electric options and even buses that are powered by natural gas. Although natural gas powered engines are not as clean as electric, they produce far fewer carbon emissions.
It’s not uncommon to find lighting in subway stations that dates back to the 1970s. You will recognize the long fluorescent tubes that light the platforms and benches that greet passing subway cars through out most stations. Although fluorescent light is generally considered energy efficient, developments in the technology that lights the fluorescent has dramatically improved. There is a small device in each of those lamps called a ballast; it is used to light the lamp. Older ballasts consume up to 20% or the energy used to light the bulb. Newer ballast operate at greater than 90% efficiency.
mills were originally designed in the first century AD by Greek engineers and met their first practical application in the ninth century AD by Persians to grind grain and pump water. Windmills met their peak use in 1930s Middle America for pumping irrigation water (over 600,000 active units).
Through ingenuity, today’s windmills provide the energy needed to power technologies that grind grain and pump water. The United States and NASA pioneered the first wind-powered electric turbines for industrial use in 1975. As of 2010, 2.5% worldwide energy consumption was wind energy. Outside of the carbon emission generated to produce electric turbine windmills, they have virtually no negative environmental impact and provide some of the cleanest energy available.ble.
The sun sends 174 peatwatts (PW) of energy to the earth - the equivalent of 116 billion running electric turbine windmills! Our ability to capture and use solar energy has dramatically improved since its discovery in the 1800’s. The first solar cell was created in 1954 and only had an efficiency of 4.5-6%, compared to today’s solar cells that operate up to an efficiency of 44%.
This increase in efficiency has taken a technology that originally sat in locations like the desert to optimize sun exposure, to your neighbor’s roof. Although solar energy is a great solution for reducing an energy bill, it can’t make an energy bill go away. Most homes with a solar array take advantage of ‘net metering.’ Most energy use in a typical home takes place in the morning and evening, when individuals or families are preparing for work or come home. During the day when the sun is at it’s highest and few home electronics are in use, solar panels will push their unused electricity back into the power grid, running the houses power meter in reverse. That means when a household is at home and using power from an energy provider, their ‘net’ power consumption is near zero.
Corporate installations operate the same, but under different conditions. As you know, most companies operate during the day and the solar energy produced will offset energy consumption. Fortunately, corporations get to take advantage of larger installations that produce more power and ultimately negotiate reduced energy cost with their power providers.
Although methane recapture sounds complex, it is a relatively simple concept. From trash landfill decomposition to human digestion, methane is a gas that is released into the atmosphere (if not captured). Unfortunately, of all green houses gases it’s one of the most detrimental; it’s twenty times more effective at trapping heat in the earth’s atmosphere than carbon dioxide.
Methane recapture programs employee technologies that keep methane from being release back into the atmosphere. Many municipalities have used methane recapture facilities at their landfills and sewage treatment plants. As the organic materials in waste decompose, the methane is syphoned into storage containers. Once captured is can be used for numerous other activities; gas generators for power, heating of facilities, or just burnt away.
You may not realize it, but you use methane every day under it’s more common name: natural gas. It might strike you as odd that methane could be considered negative to the environment, considering most people know natural gas as a relatively clean energy source. It’s only after combustion (burning) that methane transforms to water and carbon dioxide. Natural gas produces half as much carbon dioxide when burned than coal, making it a more environmentally friendly energy option.
If someone asked you to boil water, you would probably fill a pan with water and place it on your stove. Unfortunately, it’s not that easy for communities in developing nations were electricity and natural gas infrastructure do not exist. Many families and individuals rely on open fires for everyday cooking. Although it is an effective way to cook, it has some unsavory side effects that impact the environment and anyone exposed to the smoke.
Burning wood can either be part of the solution or a part of the problem. The more efficiently wood burns, the less smoke it produces. Recent technology developments have produced portable stoves that can delivered to developing communities and properly mix air with burning wood to create a nearly smokeless heat. This means fewer carbon emissions are released and individual using the stove inhales less smoke.
Smokeless stoves also have a trickle down impact on the environment. If a stove burns more efficiently, it means less wood is needed to accomplish the same tasks. As result, fewer trees are cut down to sustain daily activities. Tree’s are part of the solution in reducing the amount of green house gases in our atmosphere, as they actively scrub carbon dioxide form the air.