ENSC 2
Limitations of geothermal energy
-short life of geothermal fields -stationary nature of resource -small number of suitable sites
What proportion of U.S energy now comes from renewable resources?
13.6% of U.S. energy comes from a renewable source
How does wind speed affect the process?
20 to 60 rotations per minute (rpm) To generate electricity, most generators require the rotational speed to be faster than 1500 rpm. Gearbox connects the low-speed shaft to the high-speed shaft and increases the rotational speeds from about 20-60 rpm to about 1,000-1,800 rpm. The gear box is a costly (and heavy) part of the wind turbine and engineers are exploring "direct-drive" generators that operate at lower rotational speeds and don't need gear boxes.
What is Feed-in tariffs
A feed-in tariff is an economic policy created to promote active investment in and production of renewable energy sources
Biomass
A measure of the total dry mass of organisms within a particular region Biomass can be combusted directly to generate electricity, or mixed with coal in a process called co-firing. Biomass energy accounts for 20 to 50 % of total primary energy demand in the developing countries. Renewable if not overharvested
co-firing
A process in which biomass is combined with coal in coal-fired power plants; can be a relatively easy and inexpensive way for fossil-fuel-based utilities to expand their use of renewable energy
List two advantages and two disadvantages of solar power energy generation
Advantages: Reduces electricity bill and low maintenance cost Disadvantage: Weather dependent and expensive storage
List at least two specific advantages and two specific concerns relating to the use of biomass energy
Advantages: Renewable and carbon neutral Disadvantages: Expensive and requires space
List two potential benefits and two potential drawbacks of bioenergy.
Advantages: can be stored with minimal energy loss and emits little or no net greenhouse gas emissions Disadvantages: More expensive than fossil fuels and deforestation
Benefits and problems of wind power generation
Benefits:Wind turbines produce 20 times more energy than they consume, an EROI value better than most other energy sources. Wind power can also be easily scaled up by adding more turbines to an area of land. Problem:An intermittent resource that we cannot directly control. The geography of the landscape determines how much wind power is available. In the United States, mountainous areas and the Great Plains have the greatest potential.
Uses of bioenergy
Biomass can be used to produce renewable electricity, thermal energy, or transportation fuels (biofuels). Biomass is defined as living or recently dead organisms and any byproducts of those organisms, plant or animal. The term is generally understood to exclude coal, oil, and other fossilized remnants of organisms, as well as soils.
Nuclear power plants vs. Fossil fuel power plants
Both nuclear and fossil fuel power plants produce electricity the same way. The heat generated in these plants is used to generate steam. This steam drives a turbine, which powers a generator that converts mechanical energy to electrical energy. Nuclear energy is cleaner while generating electricity. Nuclear fission provides energy without releasing greenhouse gases such as carbon dioxide. However, nuclear power plants generate significant amounts of radioactive waste. combustion of fossil fuels releases carbon dioxide into the atmosphere. According to the Massachusetts Institute of Technology, 90 percent of the carbon emissions from electricity generation in the United States come from coal-fired power plants. They emit pollutants such as sulfur dioxide, toxic metals, arsenic, cadmium and mercury.
Difference between biomass and fossil fuels
Both of them are produced from living organisms. Biomass takes carbon out of the atmosphere while it is growing, and returns it as it is burned. If it is managed on a sustainable basis, biomass is harvested as part of a constantly replenished crop. Fossil fuels such as coal, oil, and gas are also derived from biological material. As fuels they offer high energy density, but making use of that energy involves burning the fuel, with the oxidation of the carbon to carbon dioxide and the hydrogen to water
The most severe nuclear power plant accident in the world
Chernobyl and Fukushima
Can we use tidal energy (i.e., high and low tide) to generate electricity?
Coastal areas with large differences in height between high and low tide can be used to harness tidal energy.
enhanced geothermal systems (EGS)
Enhanced geothermal systems (EGS) pump cold water into dry underground rock, allow it to be heated, then draw it back up to generate power. This can be done repeatedly, making it renewable. It has been found to trigger minor earthquakes.
Difference between bioethanol vs. biodiesel
Ethanol is produced by fermenting biomass, generally from carbohydrate-rich crops, in a process similar to brewing beer Biodiesel is a fuel produced from vegetable oil, used cooking grease, or animal fat
Briefly explain the difference between nuclear fission and nuclear fusion reaction
Fission is the splitting of a heavy, unstable nucleus into two lighter nuclei, and fusion is the process where two light nuclei combine together releasing vast amounts of energy.
Describe one sense in which geothermal energy is renewable and one sense in which it is not renewable.
Geothermal reservoirs are naturally replenished and therefore renewable (it is not possible to exhaust the resources). Geothermal power is only sustainable (renewable) if the reservoirs are properly managed.
Can we harness geothermal energy for heating or cooling house? How?
Ground-source heat pumps take advantage of this by transferring heat from the ground into buildings during the winter, and back into the ground during the summer.
What form of renewable energy is mostly used to generate electricity?
Hydropower is the most used to generate electricity
How hydropower plants generate electricity?
Hydropower plants capture the energy of falling water to generate electricity. A turbine converts the kinetic energy of falling water into mechanical energy. Then a generator converts the mechanical energy from the turbine into electrical energy.
Explain how Germany accelerated its development of PV solar power by the FIT. Do you think the US should adopt a similar system of FIT to promote renewable energy across the nation?
It created people to be actively invested in renewable resources.
Type of gasses produced in the anaerobic digester
It is made up of mainly methane (CH4) and carbon dioxide (CO2), with small amounts of water vapor, particulates, and other gasses, such as hydrogen sulfide (H2S).
biofuel
Liquid fuel created from processed or refined biomass
A photobioreactor is used to generate electricity using what?
Many species of algae are now being cultivated to produce biodiesel, ethanol, or even jet fuel. Algae can be grown at a large scale in outdoor ponds, closed tanks, or in closed transparent tubes called photobioreactors.
Environmental impacts of hydropower
Natural riparian habitat is flooded upstream of the dam, and deprived of water downstream of the dam. Suppression of flooding prevents river floodplains from receiving nutrient-rich sediment from the river. Dams cause thermal pollution if the river downstream is kept artificially shallow and it warms rapidly in the sun. Thermal shocks can occur if cold water is suddenly released from the dam's reservoir. The passage of fish and other organisms through the river is blocked.
carbon nuetral
No net CO2 into the atmosphere New Carbon
Nuclear power generation in the U.S.
Nuclear and hydropower, for example, provide about 27.5% of our electricity generation in 2017. The United States has the greatest nuclear electricity production, but France is the most dependent on it.
OTEC relies on _________to generate energy.
Ocean thermal energy conversion (OTEC) is an experimental approach that uses this temperature gradient to generate power
Difference between solar collectors and PV cells
Photovoltaic (PV) systems convert sunlight directly to electricity by means of PV cells made of semiconductor materials. Concentrating solar power (CSP) systems concentrate the sun's energy using reflective devices such as troughs or mirror panels to produce heat that is then used to generate electricity.
Describe in your own words what a PV cell is, how it functions, and how it is used.
Photovoltaics is the direct conversion of light into electricity at the atomic level. Multiple modules can be wired together to form an array. I
Consequences resulted from nuclear power plant accidents
Radioactivity was released during and after these events at levels about one-tenth of those from Chernobyl. Much of the radiation spread by air or water into the Pacific Ocean, and trace amounts were detected around the world. Japan's government temporarily shut down all 50 of the nation's nuclear reactors. Nine reactors have been restarted
A possible repository for radioactive waste in the United States
Spent fuel rods and low-level waste is currently stored in more than 120 sites across 39 states in the United States Yucca Mountain
What is the most prevalent form of renewable energy used in the US?
The most prevalent sources are bioenergy and hydropower in the U.S.
How is hydrogen fuel produced?
The process of electrolysis uses electricity to split water molecules into molecules of hydrogen and oxygen gas.
Snake-like energy converter uses ________to generate electricity.
This bending action forces hydraulic pistons to move in the device and push fluid around generating a linear flow, which produces energy.
One of the major issues facing commercial wind energy is the transmission. Briefly explain why?
Transmission lines must be built to bring the electricity from the wind farm to the city.
Difference between uranium and plutonium
Uranium is mined from naturally occurring ore The enriched uranium is formed into pellets of uranium oxide, which are placed into metallic tubes called fuel rods. Plutonium is a radioactive metallic man-made element. Over one-third of the energy produced in most nuclear power plants comes from plutonium. It is created in the reactor as a by-product. Plutonium has occurred naturally, but except for trace quantities it is not now found in the Earth's crust. Plutonium-238 is a vital power source for deep space missions.
List several concerns about the disposal of radioactive waste.
Vulnerable to weather No safe place to store it
Challenges associated with radioactive waste storage
Vulnerable to weather conditions
How can we harness geothermal energy for electricity?
Wells can be drilled toward heated groundwater, which can then be used to provide direct heating of buildings. Geothermal power plants use heated underground water and steam to generate electricity.
What forms of renewable sources are used to generate electricity in Texas?
Wind #1 Solar Natural Gas Coal Nuclear Hydro
Which two renewable sources are experiencing the most rapid growth?
Wind power and solar power are experiencing the most rapid growth
E85 flex fuel
a blend of 85% ethanol & 15% gas
carbon negative
absorbing more carbon than the community generates in order to shrink its carbon footprint Carbon capture and storage
Carbon positive
carbon output is greater than carbon intake Old carbon from 100s of millions of years
What factors determine the amount of pollutants hydrogen production will emit?
depends on the power source used to generate it: fossil fuel combustion, or a new renewable energy source.
cellulosic ethanol
ethanol produced from the cellulose in plant tissues by treating it with enzymes
How do nuclear plant engineers control fission and prevent a runaway chain reaction?
fission is controlled so that only one of two/three neutrons emitted with each fission event goes on to induce another fission event --> constant output of energy but at a controlled rate The steam is used to spin large turbines that generate electricity. Nuclear power plants use heat produced during nuclear fission to heat water. In nuclear fission, atoms are split apart to form smaller atoms, releasing energy. ... As the turbine blades turn, they drive generators that make electricity.
Biogas
from the anaerobic bacterial breakdown of waste in landfills, which produces methane that can be captured and sold as fuel.
What is geothermal energy?
thermal energy that arises from beneath Earth's surface.
How do wind turbines generate electricity?
wind causes the blades to turn which turns a turbine which turns a generator to generate electricity