Unit 6 Review book Pt. 3 Flashcards
(17 cards)
Geothermal energy
a form of energy that’s obtained from within the Earth; it’s energy that’s produced by harnessing the Earth’s internal heat.
The interior of the Earth is still warm due to radioactive decay.
Therefore, geothermal energy indirectly gains its energy from nuclear power.
The greatly elevated temperatures within the Earth result in a buildup of pressure; some of this heat escapes through fissures and cracks to the surface.
Some common examples of these fissures and cracks that you may have heard of are geysers, hydrothermal vents, and hot springs.
Process of geothermal energy production
More specifically, in the process of geothermal energy production, the naturally heated water and steam from the Earth’s interior turn turbines, and this creates electricity.
The process involved in creating electricity from geothermal energy is not unlike that of hydroelectric power; instead of water from a dam’s reservoirs spinning the turbines and generating electricity, it’s water pumped from beneath the Earth that does so.
Although surface water from geysers could be used, wells are typically drilled down into the Earth as far as thousands of meters to water that is 300–700 degrees Fahrenheit and then brought to the surface and converted to steam, which powers a turbine.
Pros of geothermal energy
Geothermal energy can also be used directly; in this process, the heated water is piped directly though buildings to heat them—this is a common method for heating homes in Iceland.
In a sense, geothermal energy is renewable; however, if the groundwater is used at a faster rate than it is replaced, then this energy source is limited.
Cogeneration
Cogeneration
Geothermal energy also provides a perfect opportunity for cogeneration— using a fuel source to generate both useful heat and electricity. Cogeneration can involve any renewable or nonrenewable energy source, and increases the efficiency of the use of a fuel—all that’s required is a system to capture “waste” heat from the energy generation process and put that heat to some useful purpose. In locations such as Iceland where geothermal energy is abundant, using this waste heat is almost always a useful plan.
Cons of geothermal energy
Unfortunately, geothermal energy hasn’t gained popularity, is expensive to install, and can potentially release toxic gas during the drilling process.
The use of geothermal energy is also limited because only a few areas have geothermal sources to tap.
Another problem with this renewable energy source is that the salts that are dissolved in the water corrode machinery parts.
Additionally, some gases (such as methane, carbon dioxide, hydrogen sulfide, and ammonia) that are trapped in the water may be released as the water is utilized.
Ocean Tides (tidal power)
The tidal movements of ocean water can be tapped and used as a source of energy.
To harvest tidal energy, dams are erected across outlets of tidal basins. Incoming tides are sluiced through the dam, and the outgoing tides pass through the dam, turning turbines and generating electricity.
Recently, ocean dams have been developed that allow energy to be harnessed from both the outgoing and incoming tides.
At this time, there is a tidal power plant installed in the East River in New York, NY, it harnesses enough power to power 10,000 homes.
There are many different designs of ocean tide power plants in the idea stages.
One of these involves having waves push into a chamber of air; the compressed air is then forced through a small hole at the turbine, and turns the turbine as it is released.
An experimental prototype of this design has been installed off the coast of Scotland and is nicknamed the LIMPET (Land-Installed-Marine- Powered Energy Transformer).
Hydrogen Cells
Hydrogen is obtained from fossil fuels by a process called reforming.
Hydrogen is very difficult to store and not very energy dense, but hydrogen fuel cells are considered by many to be the best, cleanest, and safest fuel source.
Free hydrogen is not found on Earth, but it can be released through the process of electrolysis, in which hydrogen atoms are stripped from water, leaving the oxygen atom.
Hydrogen can also be obtained from organic molecules, but the use of organic sources can release pollutants—as can the process of electrolysis if a fossil fuel, such as natural gas or coal, is used to drive the process.
However, once the free hydrogen is released, it can be stored and then used to generate electricity through the reverse reaction of electrolysis.
One of the major benefits of the use of hydrogen fuel cells is that the only waste from the fuel cell is steam—water vapor.
This technology has been used for decades in spacecrafts, but the high cost of the fuel cell and lack of hydrogen fuel stations has limited the technology to just a few test programs.
In order for hydrogen to become a truly viable option as a renewable energy source, an inexpensive and efficient way to produce hydrogen from nonfossil fuel sources must be developed.
One of the most promising techniques for this involves the use of photovoltaic cells to harvest sunlight and then power the splitting of the water molecule.
energy conservation
the practice of reducing our use of fossil fuels and reducing the impact we have on the environment as we produce and use energy.
One important form of energy conservation is the use of alternative fuel cars.
They are gaining in popularity and acceptance.
Battery electric vehicles (BEVs) slowly becoming more commonplace.
A more popular alternative is the hybrid-electric vehicle.
Several car makers also make models that use propane or natural gas as fuels, although these are not as common as hybrids.
These generate only CO2 and water as emissions, and they get good gas mileage.
A problem is the lack of refueling stations, although devices are available that allow refueling from home.
Cars can also be retrofitted with natural gas fuel tanks, so the driver can choose between gasoline or methane fuel.
Another type of alternative fuel is used cooking oils.
Battery electric vehicles (BEVs) slowly becoming more commonplace.
These vehicles run on battery power alone and can be charged with electric power.
Their downsides include the pollution from the production and disposal of the batteries, expense, and the relative dearth of charging stations.
A more popular alternative is the hybrid-electric vehicle.
Hybrid vehicles are built with two motors: one electric and one gasoline-powered.
The electric motor powers the car from 0 to about 35 miles per hour.
Above 35 mph, the gasoline engine starts and helps to power the car.
At highway speeds, both the electric and gas motors operate.
The cars are designed so that when the brakes are applied, some of the energy is transferred from the brakes to recharge the electric motor’s battery.
Not only do these cars have good gas mileage, but they also produce far less CO2 pollution than traditional gas-powered vehicles.
Another type of alternative fuel is used cooking oils.
The oils used in deep- fat fryers can be filtered and then burned in diesel-fueled cars, trucks, and buses.
After starting the engine on pure diesel fuel, the driver switches to the biofuel to drive.
At the end of the trip, the driver runs on pure diesel fuel again for a few minutes before shutting off the engine.
Another front on which steps are being taken to increase energy conservation is building design.
Designers are rediscovering and modernizing techniques like passive solar heating, using thermal mass to regulate temperatures, and incorporating photovoltaic cells and smart regulation technology to reduce the amount of energy used from the grid in heating, cooling, lighting, and other energy use.
While offices, factories, and other commercial buildings are a prime target of conservation efforts, these ideas can be implemented on a smaller scale in individual homes as well.
Residential energy consumers can adjust thermostats to reduce the use of heat and air conditioning, conserve water, use energy-efficient appliances, and use conservation in their landscaping.
Need to use renewable energy sources
It has been argued that finding new fossil fuel sources would serve the same purpose as would reducing our current use of fossil fuels.
However, this is not true—this statement does not take into consideration the fact that our use of fossil fuels has numerous negative effects on the environment.
Additionally, in the long term it will not help us much to conserve fossil fuel resources—simply because these are not renewable energy sources—so they will eventually be depleted.
Therefore, if we are to have dependable, long- term, renewable sources of energy, we must continue to develop, implement, and improve upon current renewable technology and methods.
On the legislative front, CAFE (Corporate Average Fuel Economy)
the United States has adapted the CAFE, or Corporate Average Fuel Economy, standards.
These standards set mile- per-gallon standards for a fleet of cars.
The goal of these standards is to reduce energy consumption by increasing the fuel economy of cars and light trucks.
Finally, do not forget the role of mass transit in reducing pollution.
Buses and trains can move many more people than cars.
When the amount of pollution made by the vehicle is divided by all the passengers it is carrying, the bus or train generates far less pollution per person than a car.
