ET 120 Final
A face cord of wood is:
43 cubic feet
If the static pressure in a microhydro penstock is 100 psi, the optimum net pressure for maximum flow will be closest to:
70 psi
You want to install a Southwest Windpower Air X turbine on your 1-acre lot. Your house is 30 feet tall and there are no trees on the lot. You want to order the shortest tower that will still get your turbine into the unobstructed winds. Which of the following towers should you order?
75 feet
What is the most important reason why a geothermal ground loop needs to be sized correctly?
Because a geothermal loop cannot be easily changed
The largest hydro capacity in the U.S. is found in which region?
Pacific Northwest
Which of the following is not a characteristic of a self-supporting wind turbine tower?
It is less expensive than a guyed tower
Which is the largest hydroelectric dam in the world?
Three Gorges Dam
A hydroelectric dam can be easily turned off and on quickly to provide spot electricity.
True
A microhydro site with high head would most likely use an impulse turbine.
True
An effective wind turbine uses more lift than drag to turn its rotor.
True
Biomass is the largest renewable energy source in the United States.
True
CHP is not utilized at most large-scale U.S. power plants because the power plants are remotely located.
True
Compared with Iowa, North Carolina has a more varied mix of biomass resources.
True
Fuel cells are one of the most scalable renewable energy technologies.
True
In general, the temperature of rocks within the earth increases with depth.
True
Which country in the world has the most installed geothermal energy electricity capacity?
United States
Which country in the world produces the most electricity from geothermal energy?
United States
When do the electric heat strips on a heat pump turn on?
Whenever the heat pump cannot extract enough heat from the ambient environment to meet the heating load
Which of the following renewable technologies is a viable large-scale alternative to hydroelectric power?
Wind turbines
Which of the following buildings is the best candidate for a micro-CHP generator?
a hotel with a natural gas supply
Which of the following is the best location for a ground source heat pump?
a site with equal heating and cooling needs
In the evaporator of a heat pump the refrigerant is transformed into:
all gas
Which of the following types of geothermal energy plant has the least issues with air emissions?
binary cycle
Which of the following are an advantage of biodiesel? Select all that apply.
can be made at home availability of source material biodegradable
Use the image below to match the hydroelectric dam components to their name.
reservoir - A, tailrace - I, head gate or intake - B, penstock - E, transformer - F, power transmission lines - D, turbine - H, generator - G, dam - C
What is a primary advantage of an AC microhydro system over a DC system?
smaller wire sizes
Which of the following geoexchange systems is considered an open loop?
standing column well
In terms of conversion to ethanol, select the answer that is in order from easiest to hardest to convert.
sugarcane, grains, cellulosic material
What is the approximate swept area of a horizontal-axis turbine with a rotor diameter of 16 feet?
swept area = πr^2, so 3.14159 * (8)2 = 201.06
Which of the following heat pump systems would likely give the best performance at the lowest operating cost?
system sized for 100% of the heating load and 125% of the cooling load
Which of the following countries is NOT among the world leaders in large wind turbine manufacturing?
the United Kingdom (UK) (Countries that are: Germany India China)
What is the purpose of a tail vane on a wind turbine?
to passively yaw the turbine into the wind
What is the primary purpose of a desuperheater?
to provide hot water
Which of the following could be considered an energy crop?
trees
Which of the following would be considered an advantage of geothermal energy? Select all that apply.
universal availability low cost of fuel
Substituting 10% of gasoline with ethanol (making E10) will result in:
up to 20% worse fuel economy
Which of the following is not a potential source of biogas?
used motor oil
A site with severe groundwater quality issues should use which of the following types of geothermal loops?
vertical closed loop
When does the dump load kick in on a stand-alone DC microhydro system?
whenever the battery bank is fully charged
Which of the following would need to be increased in order to create the most significant increase in the power of a wind turbine? Select all that apply.
wind speed rotor area
Which of the following are likely to be found on a large wind turbine but not on a small wind turbine? Select all that apply.
yaw motor transmission
Heat always moves from:
hot to cold
North Carolina currently has the resources to easily meet which percentage of its energy needs with biomass?
10%
What is the capacity factor of a hydroelectric dam with an installed capacity of 1,000 MW producing 180,000 MWh in a 30-day month?
180,000 MWh / (30 days * 24h per day * 1,000 MW) = .25 or 25%
Which of the following would be the approximate length of a horizontal closed loop for a 4-ton geothermal heat pump?
2,000 feet
Four fuel cells stacked together would produce a voltage closest to:
3 volts
A 40-pound bag of wood pellets has a heat content of approximately:
340,000 BTU
What is the most important consideration when selecting a small wind turbine?
Annual energy output
The United States produces more ethanol annually than:
Canada, China, and India ALL OF THE ABOVE
The maintenance on a micro-CHP unit is most similar to the maintenance on a:
Car engine
Based on wind speed, on a site of which Wind Power Class would be the best to build a wind turbine?
Class 5
What is the COP of a heat pump with a 34,000 BTU/hour capacity and 2kW input power? Round your answer to the nearest whole number.
Coefficiency Of Performance (COP) = hh / hw where hh = heat produced (BTU/hour) where hw = equivalent electric energy input (BTU/hour) = 3413 * Pw where Pw = electrical input energy in kW COP = 34,000 / (3413 * 2) = 4.98 answer: 5
From what source is the majority of the United States' ethanol made?
Corn
What is the most effective way to stop a small wind turbine from spinning out of control?
During a break in the wind, apply dynamic braking.
Name one of the two main types of biofuel.
Ethanol
A pumped hydro storage plant pumps uphill when grid demand is high and produces power when grid demand is low.
False
All areas off the cost of North Carolina are available for offshore wind turbine development.
False
Hydrogen has no smell, but odorants are added to help detect leaks.
False
Hydrogen is the most powerful power source on Earth.
False
Most dams are built to create electricity.
False
Most large utility-scale wind turbines have a tail vane.
False
Most large-scale U.S. power plants utilize CHP
False
Which of the following site would be the best candidate for significant power production using microhydro?
Head: 180 feet, Flow: 60 GPM
When designed a microhydro system, which of the following will likely result from an increase in the flow of intake water?
Increased intake maintenance
Which of the following are an advantage of wind turbines over other forms of energy generation from renewable sources? Select all that apply.
Power production scales exponentially. AND Systems can be configured and installed in a DIY fashion.
Which of the following are an advantage of microhydro over other forms of energy generation from renewable sources? Select all that apply.
Power production scales exponentially. Systems generate electricity using one of the most abundant chemicals on earth. Systems can be configured and installed in a DIY fashion.
Which of the following is not an advantage of offshore wind?
Proven reliability
What is the most common means of rotor control for small wind turbines?
horizontal furling
Which of the following is an advantage of combined heat and power (CHP)?
Systems burns fossil fuels more efficiently.
Which of the following is an advantage of tidal generators over other forms of energy generation from renewable sources?
Systems harness natural cycles that occur twice per day.
Which of the following are an advantage of hydroelectric dams over other forms of energy generation from renewable sources? Select all that apply.
Systems have an ability to provide both baseload power and peak power. Power production scales exponentially. Systems generate electricity using one of the most abundant chemicals on earth.
Which of the following are an advantage of fuel cells over other forms of renewable energy generation? Select all that apply.
Systems have an ability to provide both baseload power and peak power. Systems generate electricity using one of the most abundant chemicals on earth.
Which of the following is an advantage of geothermal heat pumps over other forms of energy generation from renewable sources?
Systems might be cost-effective on almost every home in the United States.
What is the static pressure in a microhydro penstock with a head of 300 feet?
The static pressure is the highest pressure achieved at the bottom of the penstock when it is full of water and not moving. 2.31 vertical feet of head is equal to 1 PSI of pressure. Therefore: 300 / 2.31 = 130 PSI 130 PSI
The wind turbine pictured is a:
Upwind vertical-axis turbine
In terms of energy content, lignin is most similar to:
coal
What component keeps the refrigerant moving in a heat pump?
compressor
The component of a heat pump where heat is released to the ambient environment is called the:
condenser
Which of the following is a form of heat loss in a building?
conduction
A primary advantage of wood pellets over bulk dry wood for heating is:
consistency
Of the following, the primary problem preventing the widespread use of residential fuel cell units is:
cost
In terms of wind power, the U.S. is the world leader in:
electricity produced
The diagram depicts which type of geothermal energy plant?
flash steam
Currently, most distributed generation units in the U.S. are:
fossil fuel generators
Which of the following is a byproduct of biodiesel?
glycerol
Advantages of fuel cells include which of the following? Select all that apply.
high reliability due to no moving parts AND scalable AND pollution-free
A barrage tidal generation plant is closest in terms of technology to a:
hydroelectric dam
Which of the following technologies will likely have the highest capacity factor?
hydroelectric dam
The largest source of renewable electricity in the world is:
hydroelectricity
Which renewable energy source creates the most electricity in the United States?
hydroelectricity
Which of the following are the primary goals of Advanced Hydropower? Select all that apply.
increase power capacity increase environmental performance
Binary cycle geothermal energy plants can be considered:
less polluting than steam-based plants
Compared to oil and natural gas, uncompressed hydrogen has an energy density that is:
lower
Which of the following is the most common sources of hydrogen for use in fuel cells?
natural gas
Fuel cells can utilize which of the following inputs? Select all that apply.
natural gas, hydrogen gas MAYBE ALSO biogas, propane
Biomass as a fuel source can be considered to be carbon neutral under which of the following conditions?
new planting replaces the harvested material
Which of the following power plant types is always built as a baseload plant?
nuclear plant
On which of the following sites could a vertical-axis wind turbine be considered over a horizontal-axis turbine?
on a tight urban lot with severe noise restrictions
Which one of the following is not found in a geothermal heat pump system?
outdoor unit
All other things being equal, which of the following wind turbines will likely produce the largest annual energy output?
rated output of 1 kW at a rated wind speed of 20 MPH
