Lecture 1_energy Environment And Development

QUESTION 1

In these modern days, electrical systems are very crucial to make sure the it is flexible and affordable for the people around the globe. The electricity has increased its demand from year to year as the population and more things powered by electricity are build up for easier life. As the non-renewable energies are depleting its resources, a renewable energy somehow must be used as power substitution starting from todays. In order to maximize potential of renewable energy, their flexibility must be achieved to increase the efficiency of electricity supply. . Flexibility is the ability of a system to respond to variability and uncertainty of demand and supply .Electricity demand is different from to time and sometimes unexpected events like natural disaster will requires a more flexible electricity supply to make sure it can be used anytime.

The form of converted energy widely determines the classification of energy storage systems .Electrical energy storage may be divided into 5 main categories such as chemical, electrochemical, electrical, mechanical, and thermal energy storage .

1. Chemical energy storage systems

Chemical energy is stored in the chemical bonds of atoms and molecules, which can only be seen when it is released in a chemical reaction. After the release of chemical energy, the substance is often changed into entirely different substance .Chemical fuels are the dominant form of energy storage both in electrical generation and energy transportation. Most commonly used chemical fuels which are processed are coal, gasoline, diesel fuel, natural gas, liquefied petroleum gas (LPG), propane, butane, ethanol, biodiesel and hydrogen. All of these mentioned chemicals are freely converted to thermal and mechanical energy and then to electrical energy by using heat engines as prime mover . On the other hand, the stored chemical energy can be released through electron transfer reactions for the direct production of electricity . Chemical energy storage is rather suitable for storage of large amounts of energy and for greater durations .

1.1

Hydrogen

Advantages: renewable energy source and bountiful in supply , clean energy source , non-toxic Limitation: Very expensive due to the electrolysis and steam reforming process , low density thus need to stored in liquid form only and transfer in a high pressure Present applications: Transportation Future prospect: 1. Filling station infrastructure for fuel cell cars 2. Electrification of shipping and air transport to reduce pollution and increase its efficiency

1.2

Synthetic natural gas (SNG)

Natural gas, is most popular gas fuel, mainly consist of CH4. Biogas, Landfill gas, SNG, and bio-SNG are the other gas fuels. Biogas is produced by decayed organic matters and contains CH4 and CO2. Composition of landfill is similar to biogas . Synthetic natural

gas (SNG) means the partly conversion of solid feedstock with gasification followed by gas conditioning, SNG synthesis and gas upgrading or similar processes to natural gas .

Advantages: 1. The SNG can be used to heat homes or as a fuel in cars, just like conventional natural gas. 2. Balancing energy grid by stored extra electricity as SNG. 3. Fuel power plant 4. Can be stored in enormous amount

Limitation 1. Vast amount of CO2 needed and the cost is expensive to extract it from air 2. Low efficiency as only 60% is converted from electricity to SNG

Application : 1.Power up vehicles 2.Heat homes

2.

Electrical energy storage systems

2.1

Superconducting magnetic energy storage Superconducting Magnetic Energy Storage (SMES) systems work based on electrodynamics’ principle .The energy is stored in the magnetic field created by the flow of direct current in a superconducting coil, which is kept below its superconducting critical temperature. Superconducting material has been cryogenically cooled and the stored energy can be released back to the network by discharging the coil .

Advantages: 1.Capable of storing and discharging large amount of power. 2. High efficiency (greater than 90%). 3. Quick response time (less than 100ms). 4.Completely static and robust construction. 5. Very low maintenance. 6. All types of load can operate.

Limitations : 1. Need a huge power to keep the coil at low temperature 2. Unstable mechanical system

Application: 1. 2. 3. 4.

diurnal demand leveling frequency control automatic generation control uninterruptible power supplies

3. Mechanical energy storage systems

Mechanical energy storage is classified by working principal as follows: pressurized gas, forced springs, kinetic energy, and potential energy. The most useful advantage of mechanical energy storage is that they can readily deliver the energy whenever required for mechanical works

3.1 Flywheel system

A massive rotating cylinder (a rim attached to a shaft) that is supported on a stator by magnetically levitated bearings is the main part of most modern high-speed flywheel energy storage systems

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Advantage : 1. High power and energy density. 2. No periodic maintenance is required, easily and inexpensively maintained 3. Flywheels are highly reliable, safe, long life, energy efficient and nonpolluting

Limitation: 1. Mechanical stress and fatigue limits 2. Material limits at around 700 M/Sec tip speed 3. Current Flywheels have low specific energy

Application: 1. Transportation 2. Aircraft launching system 3. Grid energy storage

Question 2

Nuclear reactor is one of the largest energy supplies after hydropower that offer a lowcarbon emission to the environment. There are about 30 countries build for a total of 443 nuclear reactors around the world to supply electricity as the demand increased from year to year. In addition, as nuclear reactor give a low impact to the environment, many industrialized countries are interested to build more nuclear reactor to minimize the emission of carbon and save the environment. However, there are some barriers that impede the development of the nuclear reactors as its risk are very high. One of the risk is risk of proliferation of nuclear weapons. Nuclear reactors themselves are not the primary proliferation risk; the principal concern is that countries with the intent to proliferate can covertly use the associated enrichment or reprocessing plants to produce the essential material for a nuclear explosive (Nuclear Energy Study Group, 2005, p. i). The nuclear reactor itself is not a bomb or processing nuclear weapons but the most worried is the usage of radioactive material , uranium and platinum. The next challenges is to think what to do with the highly reactive used fuel. A billion of money invested to do the research to find a solution where should this used fuel can be thrown away without affecting the environment. However, the only solution come out is to disposed the waste in a container and put then deep underground. After four decades of study, geological disposal remains the only scientifically and technically credible long-term solution available to meet the need for safety without reliance on active management” (Committee on Disposition of High-Level Radioactive Waste Through Geological Isolation, 2001, p. 3).

As the building a nuclear reactor and operating are a difficult tasks , it need a lot of skilled and qualified workers. In these current days, not many workforce are qualified to handle this operation and designing a nuclear reactor is a big challenge as a lot of policies need to be satisfied. A 2008 review of what is needed to revive nuclear power in the United States found that “potential bottlenecks in constructing a nuclear plant include…shortages of skilled trades people for plant construction and skilled personnel to design and operate plants safely and efficiently” (MacFarlane et al., 2008). For the prospects, the world is developing the fourth generation of nuclear plant and still under study in the framework of the “Generation IV International Forum” (GIF) and the “International Project on Innovative Nuclear Reactors and Fuel Cycles” (INPRO) . This study is focusing to increase the efficiency of the nuclear reactor and reduces the volume of the waste. The generation of nuclear energy from uranium produces not only electricity but also spent fuel and high-level radioactive waste (HLW) as a by-product. For this HLW, a technical and socially acceptable solution is necessary. The time scale needed for the radiotoxicity of the spent fuel to drop to the level of natural uranium is very long (i.e. of the order of 200 000–300 000 years). The preferred solution for disposing of spent fuel or the HLW resulting from classical reprocessing is deep geological storage. Whilst there are no such geological repositories operating yet in the world, Sweden, Finland and France are on track to have such facilities ready by 2025 (Kautsky et al. 2013). In this context it should also be mentioned that it is only for a minor fraction of the HLW that recycling and transmutation is required since adequate separation techniques of the fuel can be recycled and again fed through the LWR system.

Permanent disposal of nuclear waste

To permanently dispose the highly radioactive waste is a big challenge and it become the world concern because in the future the volumes waste will be overflow and causing problems. In current solution , the only way to dispose the waste is to store them in a container and put them deep underground. In my thought, one possible way to permanently to dispose this waste is by recycle and reuse them. Maybe it is not the time to fully reuse them because we still lack of technologies. Science is a complex subjects. Instead of investing money to dispose them to somewhere or reducing its lifetime, why not build advance technologies and some discoveries to reuse the waste. The materials in the waste can somehow be splitted and can be used as a fuel.

QUESTION 3

Biofuels can be used efficiently in any of the advanced propulsion systems now reaching the market. These include mainly hybrids and fuel cells. Hybrid vehicle technology that currently relies on fossil fuels (i.e. gasoline, diesel, natural gas and liquefied petroleum gas) may well take advantage of biofuels’ growing availability. For instance, a plug-in hybrid vehicle with a high-efficiency dedicated ethanol engine could present superior performance compared with current commercial versions. Depending upon technology characteristics, fossil fuel substitution could reach 100 per cent on a volume basis. Fuel cell technology could also benefit. The availability of multi-fuel on-board reformers that could continuously generate hydrogen out of methanol, ethanol, DME or TB would enable vehicles to use a combination of conventional and lower-cost fuelling systems. Alternatively, commercial-size multi-fuel reformers could generate hydrogen from biofuels on-site at retail stations, avoiding costly hydrogen distribution infrastructure.