PLEASE ANSWER STEP BY STEP EVERY QUESTIONS! a) A car wash needs 1200 gallons of

Question

PLEASE ANSWER STEP BY STEP EVERY QUESTIONS!

a) A car wash needs 1200 gallons of warm water a day heated from 50F to 100F.How large a solar collector would be needed to do this?  Assume an incident solar energy of 1100Btu/ft^2, and assume the collector operates at 50% efficiency. Write only the numeric part of the answer i.e., if your answer is 10 ft^2, write only 10.

(Hint: 1 gallon = 8.3 lbs)

(Hint: take into account that efficiency is only 50%)

(b) Using the same efficiency as question 1 a, calculate the amount of coal in pounds need to heat the water. Your answer should be rounded off to whole numbers and donot write the unit, just the numeric part of the answer (e.g., write 10 not 10lbs)

c) Your house foundation and basement floor are made up of 1000 ft^3 of concrete. About how many Btu are required to raise the temperature of this mass from 0 C to 40 C? GIven: thermal mass: = 22 Btu/ft^3.F for concrete. Write only the numeric part of the answer without any commas e.g., 25000 not 25,000)

(Hint: calculate the rise in temp needed in F)

d) What collector area is needed for the system shown below to provide the necessary space heating for a home having 2000 ft2 of floor area? Assume average daily insolation of 1000 Btu/ft2 and an efficiency of 50%. Also assume that the house requires 50 million Btu per thousand square feet of floor area for the 180 day heating season. Round-off your answer to the nearest round number and write only the numeric part of the answer e.g., if your answer is 10.3 ft2, write 10)

[Active solar]

e) You build a passive solar home and want to store the solar energy in a concrete floor of 1000 square feet area.  How thick should you make this floor to store 220,000 Btu with a temperature difference of 20 degrees F. Assume thermal mass of concrete = 22 Btu/ft3. Round off your answer to whole inches and write only the numeric part  e.g., if your answer is 1.5ft write 18, if your answer is 2.3 inches write 2)

f) Sun Electronics has mounted vertical solar panels on the south facing walls of their office-cum warehouse which is off the Palmetto Expressway.

Go to: http://rredc.nrel.gov/solar/old_data/nsrdb/1961-1990/redbook/atlas/Table.html

and calculate annually what percentage of energy they are losing compared to fixing the solar panels facing south at an angle of latitude + or - 15 degrees. Use the mid-point of range of insolation shown in the map for your calculations. Round off your number to the nearest integer e.g., if your answer is 25.5% write 26

Explanation / Answer

a)

First we can calculate how much energy is needed for the water heating each day. Recall that the definition of 1 BTU is the energy to heat one pound of water by 1 degree Fahrenheit.

E (needed ) = 1200 gallons × 8.3 pounds × (100 500 F )= 498000 BTU

If the solar collector is only 50% efficient, it means we need incident solar energy of E(needed) / 0.50 = 996000 BTU to do the job. Since incident solar energy is 1100 BTU / ft2, the total size of the collector needs to be:

Area=EnergyInput/(Energy/ ft2)= 996000 BTU/(1100BTU/ ft2)=905.45 square feet

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