UNERSITY OF MALAWI THE POLYTECHNIC FACULTY OF ENGINEERING DEPARTMENT OF MECHANICAL ENGINEERING BACHELOR OF ENERGY ENGINEERING YEAR 5 SUBMITTED TO : DR. S. KAUNDA SUBMITTED BY : WINFRED JOHN PEMBA (BEE/15/PE/009 COURSE NAME : ENERGY MANAGEMENT COURSE CODE : MEC-EMA-511 DUE DATE : FEBRUARY 19, 2021 DUE TIME : 18:00 Assignment 1 1. Energy conservation equation and units Schematic diagram Qin BOILER TURBINE CONDENS ER FEED PUMP Win Solution Given: Work done by the turbine (WT) = 1 MW = 1000 kW Work done on the feed pump (WP) = 5kW Heat supplied to the boiler (Qb) = 3000 kJ/kg Heat rejected in the condenser (Qc) = 2600 kJ/kg From first law of thermodynamics: ΣQ + ΣW = 0 ΣdQ + ΣdW = 0 ΣdQ = Qb – Qc = 3000 kJ/kg – 2600 kJ/kg = 400 kJ/kg Wout Qout Let αΉ be the mass flowrate in kg/s ππ½ βΈ« ΣdQ = 400αΉ [ ππ x ππ π ] = 400αΉ kJ/kg = 400αΉ kW ΣdW = Wp - WT = 5kW- 1000kW = -995kW ΣdQ + ΣdW = 0 400αΉ kW – 995 kW = 0 400αΉ kW = 995 kW 995 ππ αΉ = 400 ππ αΉ = 2.4875 kg/s αΉ = 2.4875 x 3600 kg/hour αΉ =8955kg/hour Energy resources 1. Fossil fuel is any of a class of hydrocarbon-containing materials of biological origin occurring within Earth’s crust that can be used as a source of energy. Fossil fuels include coal, petroleum, natural gas, oil shales, bitumen, tar sands, and heavy oils. All contain carbon and were formed as a result of geologic processes acting on the remains of organic matter produced by photosynthesis, a process that began in the Archean Eon (4.0 billion to 2.5 billion years ago). Most carbonaceous material occurring before the Devonian Period (419.2 million to 358.9 million years ago) was derived from algae and bacteria, whereas most carbonaceous material occurring during and after that interval was derived from plants. 2. There are nine major areas of energy resources. They fall into two categories: nonrenewable and renewable. Nonrenewable energy resources, like coal, nuclear, oil, and natural gas, are available in limited supplies. This is usually due to the long time it takes for them to be replenished. Renewable resources are replenished naturally and over relatively short periods of time. The five major renewable energy resources are solar, wind, water (hydro), biomass, and geothermal. Renewable Resources Non-renewable Resources Depletion Renewable resources cannot be depleted over time Non-renewable resources deplete over time Sources Renewable resources include sunlight, water, wind and also Non-renewable energy includes fossil geothermal sources such as hot springs and fumaroles fuels such as coal and petroleum. Environmental Impact Most renewable resources have low carbon emissions and low carbon footprint Non-renewable energy has a comparatively higher carbon footprint and carbon emissions. Cost The upfront cost of renewable energy is high. – For instance, generating electricity using technologies running Non-renewable energy has a on renewable energy is costlier than generating it with fossil comparatively lower upfront cost. fuels Infrastructure Requirements Infrastructure for harvesting renewable energy is Cost-effective and accessible prohibitively expensive and not easily accessible in most infrastructure is available for non- countries. renewable energy across most countries Area Requirements Requires a large land/ offshore area, especially for wind farms and solar farms Comparatively lower area requirements 3. Petroleum is a liquid mixture of hydrocarbons that we can harvest from rock strata. Once we extract this fluid, refiners can use it to produce several different fuels, including diesel oil, kerosene, and gasoline. There are some places where this oil does not get trapped underground, so it will start seeping to the surface. List of the Advantages of Petroleum • Petroleum provides us with a stable resource for multiple industries. We have learned how to refine hydrocarbons in recent years, but humanity has embraced the use of this product for over 6,000 years. Some of the earliest shipwrecks that we have discovered have petroleum products that worked to caulk the natural materials to create a water-resistant seal. We’ve also used the liquid for medicinal purposes. The Chinese even built primitive indoor plumbing more than 1,000 years ago to pipe the substance in to provide light and heat. • The usefulness of petroleum keeps growing. We continue to find new ways to use petroleum. How we’ve used hydrocarbons over the years might change occasionally, but the energy it provides us is as consistent today as it was when early humans first started to use it. The fuel is stable, even in storage, and that advantage allows us to create predictable outcomes once we can harvest petroleum from the rock strata, tar sands, or seeps where it occurs naturally. • We use petroleum to make renewable energy products. Critics might point out that the consumption of hydrocarbons is a leading indicator of global warming changes, but we also need petroleum to create the collectors for renewable energies as well. We wouldn’t have solar panels or wind turbines without the presence of this natural product. Over 100 liters of petroleum are necessary to create a single photovoltaic panel that collects sunlight for energy. That consumption level means it takes over two years of service for each panel to create a neutral carbon emissions experience. We must create more emissions to build a world where fewer of them are created over time. • Petroleum contains a high-density energy rating. Petroleum has one of the highest density ratings of any fossil fuel that we use for energy today. We receive a 1-to-10,000 ratio with this liquid without release particulates into the atmosphere like coal would in the same situation. Critics would point out that nuclear energy far exceeds this ratio, but no other fossil fuel comes close to what we receive from hydrocarbons. You won’t find issues with radiation when you consume this fuel either. The advantage here is that the high-density levels of the hydrocarbons make it possible for a refinery to turn the liquid into several different consumables or fuels. It is a valuable commodity because most of us consume products that come from this industry every day. That’s why there are millions of barrels of crude oil that the world uses each day. This fuel is how we manage the modern lifestyle. • It is cheap to obtain. The technologies that we use right now to harvest hydrocarbons from the ground make it an affordable commodity for the average person to use. If a barrel of oil trades for at least $30 on the open market, then manufacturers and producers have a chance to turn a profit. Because oil is widely available to most markets, we can always access the full potential of this fuel whenever we need it. • Millions of people around the world have a job because of petroleum. Petroleum supports millions of direct and indirect employment opportunities around the world every day. Every position is related to hydrocarbon consumption in some way. If you use plastic products in anything, from computers to an automobile, then you are taking part in this economy. Using electricity at work connects you to the people who harvest this liquid to fuel our everyday life. Soap, heating fuel, and even lithium-ion batteries all are part of this economy as well. List of the Disadvantages of Petroleum • The infrastructure of the petroleum industry requires continuous maintenance. Although petroleum does not lose its energy potential when we move it, our systems are flawed. When a spill does happen, the amount that spills is typically more than what a local environment can manage. That means the quality of the habitats, soil, and even our livelihoods receive adverse impacts when something goes wrong. • Petroleum is a significant contributor to greenhouse gas emissions. When there are excessive carbon deposits in our atmosphere, then the energy of the sun that reflects off of the ground does not go back into space. It reflects again, coming back to ground level to increase temperatures. Whether you believe that global warming is a natural cycle or a human-made issue, the acidity that occurs when nitrous oxide mixes with the other emissions impacts our oceans, seasons, and our overall way of life. • Exposure to petroleum is toxic for most life on our planet. The levels of toxicity for some forms of life on our planet is just 0.4% when there is petroleum exposure occurring. Humans are not immune to this issue either because the benzene that is found with hydrocarbons is a known carcinogen. When people work around this liquid on a daily basis, their white blood cell counts gradually diminish. That means they become sicker more quickly and stay ill longer than the average person. • Petroleum is a resource that nations go to war over. Petroleum is a resource that can make individuals, families, and nations wealthy overnight. Some may see this issue as an advantage because it has the power to improve one’s way of life, but it is a product that also inspires conflict. When one group has access to hydrocarbons and another does not, then that relationship can create trade wars, skirmishes, or outright battles. The number of governments that have risen and fallen because of their desire to obtain this refuel is countless. • Hydrocarbons change the composition of ocean water. If petroleum comes into contact with sea life, then death almost always occurs. The same reasons why the atmosphere becomes more acidic happens in the water. It only takes a small change to the natural pH levels to make a massive and adverse on local habitats. Over the past 200 years, there has been a 25% increase in the acidity levels of this water. When you add in the thousands of tons of plastic debris in the ocean that is present because of petroleum as well, then we increase the risk of consuming it ourselves. • Fossil fuels are a finite resource. Baby Boomers can remember multiple releases from the government that stated we had about 30 years of petroleum left to use. We continue to find new resources that allow us to tap into new reserves that let us keep using hydrocarbons, but our society continues to operate on a 50-year deadline. We could potentially run out by 2075 if there are no more new production areas that we can develop to harvest petroleum. That’s why we must think about creating products that let us use the power from renewables now instead of when it is too late. Even if we don’t run out of this product, a growing population means higher levels of demand will be present. That means there will be more scarcity in the marketplace, so products and fuel will continue to cost more. 4. Minerals are also nonrenewable natural resources. This so because they take longer than a person's lifespan to be replaced. In fact, they can take millions of years to form. Many minerals, however, can be reused and recycled many times over without losing their intrinsic properties. Many products that are made of metals also stay in use for long periods of time. 5. Natural gas is a fossil energy source that formed deep beneath the earth's surface. Natural gas contains many different compounds. The largest component of natural gas is methane, a compound with one carbon atom and four hydrogen atoms (CH4). Natural gas also contains smaller amounts of natural gas liquids (NGL, which are also hydrocarbon gas liquids), and nonhydrocarbon gases, such as carbon dioxide and water vapor. We use natural gas as a fuel and to make materials and chemicals. Biogas on the other hand, is a type of biofuel naturally produced from the decomposition of organic matter. When this organic matter is exposed to an environment without oxygen, they free a blend of gases. Although what’s mostly released is methane (between 50-75%, depending on the number of carbohydrates present in the mix) and carbon dioxide, other gases are released too in smaller quantities. The gaseous fuel formed from the conversion of organic waste such as dead plant, animal material, animal dung and kitchen wastes are called biogas. Biogas is a mixture of methane and carbon dioxide and produces a huge amount of organic manure each year. Whereas, natural gas is extracted with petroleum deposits when crude oil is brought to the surface. Difference between Biogas and Natural gas The Differences between Biogas and Natural gas are tabulated below Biogas Natural gas Obtained from shrubs, farm wastes, animal and Obtained in natural form. human wastes. Available in limited quantities Available in large quantities. Used mostly in rural areas. Used as a source of power. It is not used as raw material. Used as raw materials in petrochemical industries Decomposition of organic matter yields gas, It’s supplied for household use as LPG which has higher thermal efficiency in (Liquefied Petroleum Gas) and also used for comparison to kerosene, dung cake and charcoal. running vehicles as CNG (Compressed It gives no smoke. Natural Gas). Biogas has a caloric value that ranges from 20 to 26 MJ/m3 while natural gas has a calorific value of 39MJ/m3. 6. Role of renewable energy in future economies Regional investment and use of local services. The development, construction and operation of wind farms and solar power plants usually occurs in regional areas, and provides a significant economic stimulus in these areas. Economic benefits are widely spread in these communities and include: • use of local services (food, accommodation, fuel, general stores etc) during the development, construction, and operation period • use of local contractors in construction of the wind farm • ongoing local jobs in operating and maintaining the wind farm • lease payments to local landholders (with this income often spent in the local community. • funding of community and environmental activities and local sponsorships Provision of local jobs. Local staff are required for the ongoing operation and maintenance of renewable energy projects. While the number of jobs is related to the size of the project, all additional jobs in rural areas provide income for additional families, which increasing use of local facilities and therefore providing further benefits. Supporting local infrastructure. Infrastructure required for development of the wind farm also benefits the local community. In addition to the possibility of improved power supplies, the construction and operation of renewable energy projects often requires the improvement of other community facilities (such as roads) which are funded by the project proponent. 7. Non renewable energy sources • Fossil fuels. These come from the organic matter of plants, algae, and cyanobacteria that was buried, heated, and compressed under high pressure over millions of years. The process transformed the biomass of those organisms into the three types of fossil fuels: oil, coal, and natural gas. • Nuclear power. This is energy released from the radioactive decay of elements, such as uranium, which releases large amounts of energy. Nuclear power plants produce no carbon dioxide and, therefore, are often considered an alternative fuel (fuels other than fossil fuels). Currently, world production of electricity from nuclear power is about 19.1 trillion KWh. 8. The initial sources of energy used to operate machines • Wood. In the 1700s wood was burned as a fuel in almost every American home and business. It was used for space heating and power generation. Wood was the dominant energy source because it was easy to obtain, portable, and could be consumed on demand. • Water and Wind Power. Wind power was adopted and used to drive boats and ships which simplified their travel. Water power was used to grind grain, saw wood and pump water. 9. The most dominant non-renewable energy sources are fossil fuels and nuclear energy. Fossil fuels include; petroleum, natural gas and coal. Fossil fuels are a valuable source of energy. They are relatively inexpensive to extract. They can also be stored, piped, or shipped anywhere in the world. However, burning fossil fuels is harmful for the environment. When coal and oil are burned, they release particles that can pollute the air, water, and land. Some of these particles are caught and set aside, but many of them are released into the air. Burning fossil fuels also upsets Earth’s “carbon budget,” which balances the carbon in the ocean, earth, and air. When fossil fuels are combusted (heated), they release carbon dioxide into the atmosphere. Carbon dioxide is a gas that keeps heat in Earth’s atmosphere, a process called the “greenhouse effect.” The greenhouse effect is necessary to life on Earth, but relies on a balanced carbon budget. The carbon in fossil fuels has been sequestered, or stored, underground for millions of years. By removing this sequestered carbon from the earth and releasing it into the atmosphere, Earth’s carbon budget is out of balance. This contributes to temperatures rising faster than organisms can adapt. Nuclear energy is usually considered another non-renewable energy source. Although nuclear energy itself is a renewable energy source, the material used in nuclear power plants is not. However, nuclear energy is difficult to harvest. Nuclear power plants are very complicated to build and run. Many communities do not have the scientists and engineers to develop a safe and reliable nuclear energy program. Nuclear energy also produces radioactive material. Radioactive waste can be extremely toxic, causing burns and increasing the risk for cancers, blood diseases, and bone decay among people who are exposed to it.
