Photosynthesis converts less than 0.5% of incoming solar radiation into new phytomass. The best annual fuelwood productivity of traditional fast-growing species (poplars, eucalyptus, pines) are no more than 10 t/ha. With the energy density of the dry wood averaging 18 GJ/t. (ha = 104 m²). Now, think about a large eighteenth-century city, which is located near a very large forest, would have required at least 20-30 W/m² of its built-up area for heating, cooking, and artisanal manufacturers. This city was totally dependent on the phytomass fuels. With the annual harvest of 20 t/ha: What is the approximate power density of the harvested phytomass fuel? (t = ton; ha = hectare) 600 (W)/(m²) 1.2 (W)/(m²) 1200 (W)/(m²) 1800 (W)/(m²) 0.6 (W)/(m²)

Photosynthesis converts less than 0.5% of incoming solar radiation into new phytomass. The best annual fuelwood productivity of traditional fast-growing species (poplars, eucalyptus, pines) are no more than 10 t/ha. With the energy density of the dry wood averaging 18 GJ/t. (ha = 104 m²). Now, think about a large eighteenth-century city, which is located near a very large forest, would have required at least 20-30 W/m² of its built-up area for heating, cooking, and artisanal manufacturers. This city was totally dependent on the phytomass fuels. With the annual harvest of 20 t/ha: What is the approximate power density of the harvested phytomass fuel? (t = ton; ha = hectare) 600 (W)/(m²) 1.2 (W)/(m²) 1200 (W)/(m²) 1800 (W)/(m²) 0.6 (W)/(m²)

University Physics Volume 2

18th Edition

ISBN:9781938168161

Author:OpenStax

Publisher:OpenStax

Chapter1: Temperature And Heat

Section: Chapter Questions

Problem 101P: Many decisions are made on the basis of the payback period: the time it will take through savings to...

See similar textbooks

Similar questions

There are two important isotopes of uranium, U235 and U238 ; these isotopes are nearly identical chemically but have different atomic masses. Only U235 is very useful in nuclear reactors. Separating the isotopes is called uranium enrichment (and is often in the news as of this writing, because of concerns that some countries are enriching uranium with the goal of making nuclear weapons.) One of the techniques for enrichment, gas diffusion, is based on the different molecular speeds of uranium hexafluoride gas, UF6 . (a) The molar masses of U235 and U238F6 are 349.0 g/mol and 352.0 g/mol, respectively. What is the ratio of their typical speeds vrms ? (b) At what temperature would their typical speeds differ by 1.00 m/s? (c) Do your answers in this problem imply that this technique may be difficult?
A woman expends 95 kJ of energy in walking a kilometer. The energy is supplied by the metabolic breakdown of food intake and has a 35 percent efficiency. If the woman drives a car over the same distance, how much energy is used if the car gets 8.8 km per liter of gasoline (approximately 20 mi/gal)? The density of gasoline is 0.71 g/mL, and its enthalpy of combustion is 49 kJ/g. Enter your answer in scientific notation. Compare the efficiencies of the two processes. kJ (driving)/ kJ (walking)
Many decisions are made on the basis of the payback period: the time it will take through savings to equal the capital cost of an investment. Acceptable payback times depend upon the business or philosophy one has. (For some industries, a payback period is as small as two years.) Suppose you wish to install the extra insulation in Exercise. If energy cost $1.00 per million joules and the insulation was $4.00 per square meter, then calculate the simple payback time. Take the average ΔT for the 120 day heating season to be 15.0ºC.
A 4-ton air conditioner removes 5.06×107 J (48,000 British thermal units) from a cold environment in 1.00 h. (a) What energy input in joules is necessary to do this if the air conditioner has an energy efficiency rating ( EER ) of 12.0? (b) What is the cost of doing this if the work costs 10.0 cents per 3.60×106J (one kilowatt-hour)? (c) Discuss whether this cost seems realistic. Note that the energy efficiency rating ( EER ) of an air conditioner or refrigerator is defined to be the number of British thermal units of heat transfer from a cold environment per hour divided by the watts of power input.
At a certain location, the solar power per unit area reaching Earth’s surface is 200 W/m2, averaged over a 24-hour day. If the average power requirement in your home is 3 kW and you can convert solar power to electric power with 10% efficiency, how large a collector area will you need to meet all your household energy requirements from solar energy? (Will a collector fit in your yard or on your roof?)
The Sun delivers radiant energy to Earth at a rate that averages approximately 1.3kW per square metre of the cross-sectional area of Earth. If we assume that all ofthis energy is absorbed by Earth (i.e., that Earth has an emissivity of one), at whatrate must Earth radiate energy if Earth’s temperature is to remain constant? Whatwould that constant temperature be? (Note: The actual temperature of Earth issomewhat higher due to the greenhouse effect of the atmosphere.)
he metabolic power for typing is 150 W for Lili, not a lot as you know probably. How long does it take to burn off the energy in a slice of apple pie, which energy content is 1680 kJ (400 food calorie), in minutes? (Try to stay active, working/studying in front of a computer is not the best exercise you can do for your body.) Your answer needs to have 3 significant figures, including the negative sign in your answer if needed. Do not include the positive sign if the answer is positive. No unit is needed in your answer, it is already given in the question statement. NOT 187
In a refrigeration system, the refrigerant gas absorbs 21.39 kJ of energy while expanding against a0.278 atmosphere pressure from a volume of 0.0423 liters to a volume of 1.876 liters. What is the change in the internal energy of the gas? Note that 1 literxatmosphere is equal to .101.325 joule
Amy 68 kg in mass eat a Sausage 'N Egg McMuffin and drink a medium size orange juice for breakfast. After breakfast, she decides to "work off" all the consumed energies by running up a 5-degree slope trail at 15 km/h. [Answer in 2 significant figures] Use 1 cal = 4.184 J. %3D Food Energy content in Cal Sausage 'N Egg McMuffin 480 Medium size orange juice 190 Activity on level ground Metabolic power (W) Running at 15 km/h 1150 [Answer in 2 significant figures] What is the necessary metabolic power for Amy? [Hint: You can model her power needs as the sum of the power to walk on level ground plus the power needed to raise her body by the appropriate amount. Assume that the efficiency of the body in using energy is 25%] How far did Amy run to work off all the energies she consumed?
In a home, 8 lamps, 3 fans and 2 Air conditioners are used. The ratings of each lamp is 40 Watts. The ratings of each fan is 75 Watts. The ratings of each Air conditioners is 1300 Watts. Calculate the total electrical energy consumed by these loads for last month (February 2021).
Radioactive decay of granite and other rocks in Earths interior provides sufficient energy to keep the inrerior molten, to heat lava, and to provide warmth to natural hot springs.This is due to the average release of about 0.03 J per kilogram each year. Find an increase in temperature for a thermally insulated chunk of granite that takes about 13.2 million years to change temperature. (Assume that the specific heat capacity c of granite is 800 J/kg. C. Use the equation Q=cmdeltaT.
Air conditioners sold in the United States are given a seasonal energy-efficiency ratio (SEER) rating that consumers can use to compare different models. A SEER rating is the ratio of heat pumped to energy input, similar to a COP but using English units, so a higher SEER rating means a more efficient model. You can determine the COP of an air conditioner bydividing the SEER rating by 3.4. For typical inside and outsidetemperatures when you’d be using air conditioning, estimate the theoretical maximum SEER rating of an air conditioner. (New air conditioners must have a SEER rating that exceeds 13, quite a bit less than the theoretical maximum, but there are practical issues that reduce efficiency.)