The high power, fast recharge and long cycle life attributes of the Supercapacitor make them ideal for transportation applications. Some hybrid electric systems that rely on batteries for energy storage and power delivery can suffer from poor application performance due to the limited power capability of batteries. Short battery life, oversized battery banks and safety concerns are other problems that engineers encounter with battery hybrid electric systems. Supercapacitors can be implemented in a hybrid electric system and completely eliminate the need for batteries. Other times the supercapacitors can be combined in parallel with the batteries in a hybrid electric system to enable a downsized battery, longer battery life and improved application performance. Pure electric transportation systems can realize these same benefits.
A common implementation of supercapacitors in wide use for more than 15 years is the diesel hybrid electric bus. Typically this is a series hybrid system that uses only supercapacitors for energy storage, but parallel hybrid systems are also in use. These buses are able to downsize the diesel engine by 50%. In the series hybrid, the supercapacitors are used for high power acceleration until the bus reaches cruising speed, and can then be switched to diesel. The supercapacitors are also used to recapture energy during braking, which is highly efficient due to the high power capability. These buses achieve greater than 25% fuel savings and 10+ year life for the supercapacitors.
Electric rail is another common supercapacitor transportation application in wide use for more than 15 years. These systems are either on-board the train or trackside, which is referred to as wayside energy storage. The ultracapacitors are used to recapture and store braking energy that is normally burned off through resistors. The stored energy is then used for acceleration of the train which reduces energy consumption from the grid. Another benefit is the grid voltage stabilization effect that is a result of reduced grid demand during peak usage hours. An additional benefit of the on-board systems is the ability for the train to drive with no overhead line power for a short distance (0.5km typical). Energy savings of greater than 25% has been realized in these systems.
Supercapacitors are already widely used in stop/start systems, active suspension systems, engine starting solutions and many other systems that require a high power, maintenance free, long life energy storage solution. When these automotive systems use batteries, the designer must take into consideration battery reliability concerns, battery maintenance and life isssues, additional weight and safety. Supercapacitors are a solution that can be designed-in to last the expected life of a system (or longer). They are lighter weight than batteries, occupy a smaller space and are inherently safer. Operating from -50C to +65C gives the supercapacitor a significant advantage over batteries in automotive systems.
Motocyles, ATV's, Side-by Side's, Snow mobiles, Boats, Motorhomes and Trailers can all benefit from implementing a bank of supercapacitors in various systems. Engine starting is a primary application already in wide use today. Using supercapacitors in parallel with the lead acid battery can improve engine starting performance/reliability; especially in cold environments. Many if these vehicles suffer from lead acid battery performance problems due to infrequent use and infrequent charging. Even if the battery is too weak to start the engine alone, the ultracapacitors can still access energy in the battery to start the engine, even at -40C. When a Motohome or Trailer is parked and not connected to grid power, they can operate on battery power (with engine or generator off). If the batteries discharge too low, then the generator or engine may not start when needed. Supercapacitors can be used in parallel with the batteries to handle peak loads (water pump cycling on and off, for example) to protect the battery, extend life and ensure reliable engine/generator starting.
Heavy duty vehicles include include Semi-trailer trucks, transit buses, delivery trucks, construction equipment, agricultural equipment and other types of large vehicles that use internal combustion engines for motive power. The largest usage of ultracapacitors in these vehicles is for engine starting. Reliable engine starting is extremely important considering that any delays caused by start failure can result in extra costs from jump start services to late deliveries and delayed projects. Many of these vehicles operate in cold climates, which is problematic for lead acid, but no problem for ultracapacitors. In addition to engine starting there are other opportunities for ultracapacitors in heavy duty vehicles, including: hybrid electric drive systems, power for operating lift gates, power for data communication/tracking systems, driving hydraulic pumps with electric motors instead of the engine, and more.