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In addition, in both electric and hybrid vehicles, regenerative braking is a very effective way to recover energy by charging the battery, but sometimes it recovers more energy than the battery can handle. This is particularly true for large vehicles such as trucks, buses and off-road machinery,These vehicles begin their long downhill descent almost immediately when the batteries are fully charged. Instead of sending excess current to the battery, the solution is to send it to a brake resistor or a set of brake resistors that use resistance to convert electrical energy into heat, and expel heat into the surrounding air.The main aim of the system is to preserve the braking effect while protecting the battery from overcharging during regenerative braking, and energy recovery is a useful incentive.“Once the system is activated, there are two ways to use heat,” the EAK says. “One is to preheat the battery. In winter, the battery may get cold enough to damage it, but the system can prevent that from happening. You can also use it to warm the cabin.”.
In 15-20 years, where possible, braking will be regenerative, not mechanical: this creates the possibility of storing and reusing regenerative braking energy, rather than just dissipating it as waste heat. The energy can be stored in a vehicle's battery or in an auxiliary medium, such as a flywheel or supercapacitor.
In electric vehicles, the DBR's ability to absorb and redirect energy helps with regenerative braking. Regenerative braking uses excess kinetic energy to charge the battery of an electric car.
It does this because the motors in an electric car can run in two directions: one uses electricity to drive the wheels and move the car, and the other uses excess kinetic energy to charge the battery. As the driver lifts his foot off the gas pedal and presses the brake, the motor resists the vehicle's motion, “Switches directions,” and begins to re-inject energy into the battery.Therefore, regenerative braking uses electric vehicle motors as generators, converting lost kinetic energy into energy stored in the battery.
On average, regenerative braking is between 60% and 70% efficient, meaning that about two-thirds of the kinetic energy lost during braking can be retained and stored in EV batteries for later acceleration, this greatly improves the vehicle's energy efficiency and extends battery life.
However, regenerative braking can not work alone. DBR is required to make this process safe and effective. If the car's battery is already full or the system fails, the excess energy has no place to dissipate, which may cause the entire braking system to fail. Therefore, DBR is installed to dissipate this excess energy, which is not suitable for regenerative braking, and safely dissipate it as heat.
In water-cooled resistors, this heat heats water, which can then be used elsewhere in the vehicle to heat the cab of the vehicle or to preheat the battery itself, since the efficiency of the battery is directly related to its operating temperature.
Heavy Load
DBR is not only important in the general EV braking system. When it comes to braking systems for electric heavy-duty trucks (HGV) , their use adds another layer.
Heavy-duty trucks brake differently from cars because they don't rely entirely on running brakes to slow them down. Instead, they use auxiliary or endurance braking systems that slow the vehicle down along with the road brakes.
They do not overheat quickly during prolonged downturns and reduce the risk of brake decay or road brake failure.
In electric heavy trucks, the brakes are regenerative, minimizing wear on the road brakes and increasing battery life and range.
However, this can become dangerous if the system fails or the battery pack is not fully charged. Use DBR to dissipate excess energy in the form of heat to improve the safety of the braking system.
The future of hydrogen
However, DBR does not only play a role in braking. We must also consider how they can have a positive impact on the growing market for hydrogen fuel cell electric vehicles (FCEV) .While FCEV may not be feasible for widespread deployment, the technology is there, and certainly has longer-term prospects.
The FCEV is powered by Proton exchange membrane fuel cell. FCEV combines hydrogen fuel with air and pumps it into a fuel cell to convert hydrogen into electricity.Once inside a fuel cell, it triggers a chemical reaction that leads to the extraction of electrons from hydrogen. These electrons then generate electricity, which is stored in small batteries used to power vehicles.
If the hydrogen used to power them is produced from electricity from renewable sources, the result is a completely carbon-free transport system.
The only end products of fuel cell reactions are electricity, water and heat, and the only emissions are water vapor and air, making them more compatible with the launch of electric cars. However, they do have some operational drawbacks.
Fuel cells can not operate under heavy loads for long periods of time, which can cause problems when accelerating or decelerating rapidly.
The research on the function of fuel cell shows that when the fuel cell starts to accelerate, the power output of fuel cell gradually increases to a certain extent, but then it begins to oscillate and decline, although the speed remains the same. This unreliable power output poses a challenge for carmakers.
The solution is to install fuel cells to meet higher power requirements than necessary. For example, if FCEV requires 100 kilowatts (kW) of power, installing a 120 kW fuel cell will ensure that at least 100 kW of the required power is always available, even if the fuel cell's power output declines.
Choosing this solution requires DBR to eliminate excess energy by performing“Load group” functions when it is not needed.
By absorbing the excess energy, DBR can protect FCEV's electrical systems and enable them to respond very well to high power demands and accelerate and decelerate quickly without storing the excess energy in the battery.
Automakers must consider several key design factors when selecting DBR for electric vehicle applications. For all electric-powered vehicles (whether battery or fuel cell) , making the components as light and compact as possible is a primary design requirement.
It is a modular solution, meaning that up to five units can be combined in one component to meet up to 125kW of power requirements.
Using water-cooled methods, the heat can be safely dissipated without the need for additional components, such as fans, like air-cooled resistors.
Post time: Mar-08-2024
