Many of the hybrid power systems under development for use in vehicles offer a means for recapturing “wasted” vehicle energy. One of the best-known examples is the hybrid electric vehicle which couples the vehicle’s drive system to generators that store the electricity produced during deceleration in batteries. Another system with great potential is the hybrid hydraulic system which proposes an accumulator to store energy for later use. UW–Madison researchers have developed an accumulator that provides an exceedingly simple and elegant solution to the limitations of prior accumulators.
Hybrid electric vehicles
One approach to lowering the CO2 emission from traffic is the hybridization of vehicles. A hybrid vehicle uses two or more distinct power sources, i.e. hybrid electric vehicles (HEVs) combine an internal combustion engine and one or more electric motors. Vehicles employed in urban areas like small passenger cars, local delivery trucks and city busses benefit from hybridization and show substantially lower CO2 emissions, ranging from 23 to 43% depending on the traffic dynamics. For passenger cars there are various levels of hybridization possible all giving rise to various amount of CO2 emission reductions at different costs. Small passenger cars benefit the most from strong downsizing in combination with micro hybridization. Cars running most of their kilometers on motorways do not benefit from hybridization mostly because on motorways vehicles drive at more or less constant speeds. Hybrid vehicles are still more expensive than traditional vehicles using an internal combustion engine. They have the advantage of higher fuel efficiency and reduced CO2 emissions without additional infrastructure requirements.
At present, there is no single good solution to the problem of lowering CO2 emission in the transport sector. Currently, there are two major technical pathways to GHG emission reductions. The first pathway involves the deployment of low carbon alternative fuels like biofuels, LPG, LNG and CNG. The second technical pathway involves the improvement of the energy efficiency of the vehicles through downsizing of the engine and various levels of hybridization and electrification. These two technical pathways are complementary.
The most energy efficient vehicle available today is the electric vehicle. However, commercialization of full electric vehicles is still hampered by high purchase prices, short driving ranges and long recharging times. These facts have led to the construction of hybrid vehicles. A hybrid car combines an internal combustion engine with technologies used in full electric vehicles.
Hybrids achieve improved efficiencies by employing several techniques. An important technique is regenerative breaking. During breaking the kinetic energy of the vehicle is normally dissipated as heat in the breaking discs. However, in hybrid vehicles, electro motors attached to the wheels serve as generators during breaking converting the kinetic energy into electricity. In full hybrid vehicles the electro motors also propel the vehicle at relatively low speeds. The advantage of electro motors over combustion engines at low speeds is that even at low revolutions they can exert the maximum torque (pulling force). In contrast combustion engines need to go to much higher revolutions to exert their maximum torque. This makes electro motors much more efficient at low speeds than combustion engines.
The Office of Energy Efficiency and Renewable Energy (EERE) of the United States Department of Energy offers an animated explanation of how HEVs work and why they are more fuel efficient.
There are four different levels of hybridization available in vehicles (Larsen, 2004):
- Micro hybrids do not use electric motors to propel the vehicle. The electric motors are only used as generators for regenerative breaking to charge the car battery. These vehicles have small generators connected to the internal combustion engine lowering the friction and hence lowering the fuel consumption. Additionally, micro hybrids employ the start-stop system which switches the engine off during idling. (RDW, 2010)
- Mild hybrids have electric motors which are used to propel the vehicle. However, they cannot drive solely electrically. Mild hybrids also employ regenerative breaking and the start-stop system. (RDW, 2010)
- Full hybrid cars are parallel hybrids which can be propelled fully electric at low speeds and use the internal combustion engine at higher speeds or when the electric energy stored in the car battery is low. RDW, 2010)
- Series hybrid cars are full electric vehicles which use the internal combustion engine as a generator to produce electricity. The powertrain of a series hybrid is identical to a battery electric vehicle and a hydrogen fuel cell vehicle. The only difference between these three electric vehicles is the source of the electricity produced by the car. (RDW, 2010)
Feasibility of technology and operational necessities
Hybrid electric vehicles are most feasible for use in urban traffic, where there is a frequent need for breaking. The effect of the regenerative breaking and the use of electro motors of a hybrid car on CO2 emissions is shown in figure 1. According to this graph, hybrid vehicles have substantial tailpipe CO2 emission reductions only at relatively low speeds. The graph assumes that at speeds below 50 km/h, the vehicle is operated in an urban area with the corresponding traffic dynamics.
The improved efficiency of hybrid vehicles makes hybridization especially worthwhile for urban passenger cars, small trucks for local delivery and city busses. Hybrid vehicles do not show a significant improvement in fuel consumption when driven on highways. Vehicles which are mainly used on highways are best equipped with downsized diesel engines to obtain minimal fuel consumption. A large advantage of hybrid vehicles compared to other options for reducing GHG emissions in transport is the fact that no additional infrastructure investments are required
Status of the technology and its future market potential
The hybrid vehicle has left the large scale demonstration phase and is now in the first stage of commercialization. A variety of different HEVs are commercially available today.
- Micro hybridization is often used for relatively small cars in combination with strongly downsized internal combustion engines. Examples are the VW Polo Bluemotion and the VW Up. The VW Bluemotion motion has a type approval (the process which ensures that vehicles meet applicable safety and environmental standards) value for the tail pipe CO2 emission of 87 grams/km (RDW, 2010).
- Mild hybridization is mainly used for midsized vehicles. Examples are the Honda Insight and the Honda Civic. The Honda Insight has a type approval value for the tailpipe CO2 emission of about 105 grams/km (RDW, 2010)
- Full hybridization is mainly used for bigger cars. Examples are the Toyota Prius and variousmodels by BMW and Mercedes. The Toyota Prius has tailpipe CO2 emission of about 92 grams/km
- Series hybrids are not available yet but will become so in the near future. Examples are the Opel Flextreme, Opel Ampera and the GM volt.
How the technology could contribute to socio-economic development and environmental protection
Hybrid vehicles only have substantially lower CO2 emissions when they are operated in urban areas (see figure 1). This fact makes hybridization an especially suitable tool for lowering CO2 and NOx emission from city buses and local delivery trucks. In a 2006 study by NREL the performance of hybrid diesel buses has been evaluated (Chandler, 2006). The fuel consumption of thirty new diesel articulated buses was compared with the fuel consumption of ten hybrid diesel buses over a period of 12 months. Depending on the traffic dynamics, the hybrid buses have 23 – 43% lower CO2 emission and 18-39% lower NOx emissions compared to similar new non hybrid diesel articulated buses.
A second group of vehicles which can substantially benefit from hybridization are the trucks used for local delivery in urban areas. In a 2009 study by NREL six hybrid delivery trucks were compared to six standard diesel delivery trucks over a period of 12 months (Lammert, 2009). The fuel economy of the hybrid trucks was about 29% better than the fuel economy of the standard diesel delivery trucks. However, a 29% increase in NOx emission was found.
It is difficult to assign a CO2 emission reduction to (full) hybrid passenger vehicles. A full hybrid vehicle driven most of its kilometers in urban areas can have CO2 emission reductions up to 25% (Passier et al, 2007). However, a passenger cars driving most of its kilometers on motorways will at most have very little CO2 emission reduction. The higher weight of the vehicle, because of the additional electro motors and car batteries, may even lead to higher CO2 emissions than comparable non hybrid vehicles. Therefore, for example city taxis are a good niche market for (full) hybrid vehicles.
Financial requirements and costs
Micro hybridization is the cheapest solution for passenger cars to benefit from fuel saving technologies like the start-stop system and regenerative breaking. In contrast, full hybridization of vehicles is still a relative expensive technique. Additional costs for the full hybridization of a light passenger car range from US$3,000 to US$6,000 (UNEP, 2009). The costs of maintenance of full hybrid cars are expected to be equal to non-hybrid vehicles. It is expected however, that the overall costs over the lifetime of a vehicle are lower for a hybrid vehicle due to better fuel efficiency.
The purchase costs of a hybrid bus can be 30% higher than a comparable non hybrid bus (Chandler and Walkowics, 2006). But the total operating costs of a hybrid bus are approximately 15% lower than for a non-hybrid bus, which implies that the initial 30% higher purchase costs can be earned back by lower operating costs over the lifetime of the bus.
Clean Development Mechanism market status
This information is kindly provided by the UNEP Risoe Centre Carbon Markets Group.
Project developers of projects deploying hybrid electric vehicles can use the following CDM methodology: AMS-III.C.: Emission reductions by electric and hybrid vehicles.
- Chandler, K. and Walkowics, K. (2006). King County Metro Transit Hybrid Articulated Buses: Final Evaluation Results. NREL/TP-540-40585, available at 
- Lammert, K. (2009): Twelve-Month Evaluation of PS Diesel Hybrid Electric Delivery Vans. NREL/TP-540-44134, available at 
- Larsen, R.P. (2004). An overview of Hybrid Vehicle Technologies. Argonne National Laboratory, Center for Transportation Research, 2004.
- Passier, G., F.V. Conte, S. Smets, F. Badin, A. Brouwer, M. Alaküla, D. Santini (2007). Status Overview of Hybrid and Electrical Vehicle Technology 2007; Final report of Phase III, Annex VII, IEA. TNO, Delft, The Netherlands
- RDW (2010). Brandstofverbruiksboekje 2010. available at 
- UNEP, 2009. Hybrid electric vehicles - An overview of current technology and its application in developing and transitional countries. United Nations Environment Progamme, Nairobi, Kenya.
Hybrid electric vehicles
Vehicle to Grid (V2G) involves using excess battery power from electric vehicles such as Battery Electric Vehicles and Plug-in Hybrid Electric Vehicles to help balance the load of localized power grid segments during peak hours. The storage in electric vehicles has not been used previously by the electric grid. There has never been any business that negotiates between grid operator power need and automobiles.
Scientists at North Dakota State University (NDSU) have developed a unique process for high-volume production of silicon nanowires based on electrospinning. The technology can be used for the development of lithium ion batteries with significantly improved energy densities and long life consistent with performance targets established by the US Department of Energy for plug-in hybrid electric vehicles.
A recent GBI Research report on the Discrete Power Semiconductor device market (forecasting up to 2020) shows an increased demand from the Hybrid Electric Vehicles Solar and Wind Energy markets. Although the majority of the market is dominated by Silicon MOSFETs and Insulated Gate Bipolar Transistors (IGBT) Silicon Carbide (SiC) has emerged as a viable replacement due to its advantages over conventional Silicon devices.
Background: Although a battery can store significant amounts of energy it cannot deliver it quickly. But a battery can be used to charge a capacitor which then can provide much power all at once. Supercapacitors consist of electrodes collectors a separator that keeps the electrodes out of electrical contact and an electrolyte which allows ions to move freely through the separator. Typically supercapacitors use aqueous electrolytes which can be unstable at high voltages or organic liquid electrolytes like acetonitrile which are highly toxic and flammable.
Developing electric thrust systems for displacement boats. Electric thrust systems for displacement boats will increasingly become the standard for both commercial and recreation boats due to environment-friendliness and functionality perspectives. Such implementations are greener and all-electric systems enable simpler more sophisticated and more reliable control of a boat’s thrust navigation environmental and human support systems.
Framework substituted clathrates for lithium-ion battery anodes (Alternate title: Alloys of clathrate allotropes for rechargeable batteries)Type:Product
The lithium battery industry is undergoing rapid expansion now representing the largest segment of the portable battery industry and dominating the computer cell phone and camera power source industry. Beyond consumer electronics LIBs are also growing in popularity for military electric vehicle and aerospace applications. Lithium-ion batteries are a family of rechargeable battery types in which lithium ions move from a negative electrode to the positive electrode during discharge and back when charging. Compared to graphite anodes much higher capacities are expected in silicon materials.
Background: In recent years there has been a greater interest in making more energy efficient automobiles. A number of plug-in vehicles (PEVs) or hybrid electric vehicles (HEVs) are offered by nearly every automaker today. Although these vehicles offer a cleaner and more energy efficient alternative to traditional petroleum-fueled vehicles mainstream consumer acceptance of these technologies is stymied by considerations of their premium price limited travel range and extended charging times all consequences of current battery technologies.
Novelty: This invention provides both a combined battery/ultracapacitor energy storage system and battery chargers associated with these systems. First it combines an ultracapacitor with a battery to optimally power both high current surges and more constant demands. The ultracapacitor provides the high current power thereby insulating the battery from such uses. Second the technology introduces a circuit with a switch and control device to monitor the current load on the system and regulate the battery charging cycle accordingly.