Furthermore, the rating for ripple current for this capacitor will be much lower than required in flyback converter. Due to high inductance of primary winding of the transformer, the power transistor has a lower peak current. The output ripple voltage is lower. More energy efficient compared to other isolated converter. DISADVANTAGES: Higher cost because of the extra output inductor and freewheeling diode.
THERMOELECTRIC COOLING In thermoelectric cooling Peltier’s effect is used to cause heat flux between the junctions of different types of materials. A Peltier heater/cooler transfers heat from one side of the device to the other by consuming electrical energy. This device is also known as a Peltier device, Peltier heat pump, solid state refrigerator, or thermoelectric cooler (TEC). Since there are more economical and easy ways of achieving cooling, Peltier’s devices are mostly used for cooling purposes. However, since a single device can be used for both heating and cooling, the desirability of Peltier’s device is more.
Thermoelectric generators or TEGs are generators that have the outstanding ability to convert heat into electricity that can be used to power items such as cell phones or tablets up to cars and buildings. They are classified as any device that can convert heat energy to usable electric energy or vice versa. To be able to produce electricity or power, a thermoelectric generator uses what is called the “Seebeck effect.” Thermoelectric generators have a low efficiency rate between five and eight percent, but because they run off of waste heat it helps to optimize the amount of energy a power plant can put out. Many people believe that their efficiency will one day pass up the efficiency of mechanical powered generators. These generators first came into history in 1821 when Thomas Seebeck discovered that when a circuit was formed from two metals each at a different temperature (one hot, one cold) an electrical current could flow through.
In each step (conversion of energy) there is loss of energy (friction or heat for instance) so a fuel cell does the desired conversion in one step and that leads to less energy loss. Fuel cell consists of the electrolyte which keeps the reactants from mixing together (a membrane), two electrodes (cathode and anode) which are usually catalyst. Some cells have in addition to that pi polar plates. They collect the current and cr... ... middle of paper ... ... chromite due to its high thermal expansion compatibility. In addition, for operating temperature less than 700 oC, stainless steels could be used as a constructed material for interconnects, which is cheap and readily available.
It is reliable (the source of heat, the Earth itself, is relatively constant), and hazard, in terms of unwanted waste products or catastrophic accidents, is nonexistent. There are atmospheric emissions from geothermal power plants which are predominantly CO2 and H2S. However, in the context of global climate change, geothermal has significantly lower CO2 emissions than fossil fuels. Atmospheric emissions from geothermal plants average only about 5% of the emissions from equivalent generation sized fossil fuel power plants. The actual land use for geothermal energy production is relatively small for both the fuel acquisition and the energy production.
A fuel cell is mainly used to provide electricity from chemical reactions. It harnesses the chemical energy of hydrogen and oxygen to generate electricity without combustion one of the basic types of fuel cells is the Polymer Electrolyte Membrane Fuel Cell (PEMFC). This section will give a general description of its parts, how do they function and the material they are consisted of. 3.2 Background Polymer electrolyte membrane fuel cells operate at relatively low temperatures, around 80°C (176°F). Low-temperature operation allows them to start fast (less warm-up time) and results in less wear on system components, which result in better durability.
An additional benefit is that the fuel is readily accessible. This means that if more energy needs to be produced, then more fuel can be used immediately. Furthermore, nuclear power doesn’t give out substances to the atmosphere like carbon dioxide, carbon monoxide, mercury, nitrogen oxides or sulphur dioxide. Another advantage is that nuclear power doesn’t contribute to global warming or acid rain. Also the quantity of waste produced by nuclear power plants is rather small which makes the chance of diseases for humans less.
Not having to rely on the climate and weather to operate, they can produce large amounts of energy 24/7 while in operation. Power plants take up much less land compared to other green energy sources such as wind and solar power. (NEI, 2013) Some people worry about the waste that nuclear power leaves behind. In relation to the amount of energy that it produces, the toxic waste is minimal. The waste is very small in comparison to waste produced by fossil fuels.
There are sources of energy that are renewable and do not cause so many pollutants, however they only contribute a smaller amount to the energy pyramid. These sources include hydro-electric power, wind power, solar energy and biomass energy. Most of these fuel sources do not produce as much energy as efficiently as the majority of fuel sources used today. Solar power is a clean source of practically inexhaustible energy. Solar plants are easy to construct and solar power is safe.
Typical densities are in the range of 2300 – 2700 kg.m-3 compared with 3200 kg.m-3 for hot pressed and sintered silicon nitride. Higher densities can be achieved by HPSN and SSN methods. However, the higher density gives the materials with better physical properties and so they are used in more demanding applications. The nitridation produces only a small volume change, which means that RBSN components do not need to be machined after fabrication and complex near net shapes can be produced in a single process