FREE Certified Energy Manager: Steam, Industrial and Thermal Storage Questions and Answers

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A manager of energy is comparing the running expenses of two boilers. One uses natural gas and has a 75% efficiency, while the other uses electricity and has a 97% efficiency. Electricity is $0.095/kWh and natural gas is $0.92/therm. Calculate the price per MMBtu for each system's water heating.

Correct! Wrong!

An ESCO finds chances for energy savings in the new building's design (which has not been built yet). Which of the following M&V Approaches would be the best fit to take into account the "avoided cost" (resulting from the energy savings) inside the new structure?

Correct! Wrong!

Because there are no energy performance statistics for the new portion of the building, IPMVP Option D is helpful in this situation. Option D enables simulation in order to determine baseline and "avoided expenses" associated with making energy improvements.

What does enthalpy equal at 400 degrees Fahrenheit for saturated steam?

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Enthalpy in the gaseous state (hg), which is equal to 1201 Btu/lb, may be calculated using the Saturated Steam tables.

Storing Thermal Energy Latent heat storage is the main method for employing ice as a storage medium.

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More Btu can be stored (or released) in energy storage systems thanks to the "phase change" energy.

In general, if cooler air enters a compressor, the compressor's efficiency is:

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Because colder air is denser and dryer, it requires the compressor to operate less and is therefore more efficient.

Consider a process that consumes 10,000 MMBtu per year and is powered by a 50 percent efficient, old oil-fired boiler that burns leftover fuel oil #6. What energy savings might you expect if you upgrade to an 80% efficient natural gas-fired boiler?

Correct! Wrong!

To determine the savings, we need to compare the fuel consumed before and after the retrofit.
Before the retrofit, if the boiler is only 50% efficient, then the fuel supplied to the boiler will be more than the 10,000 MMBtu needed for the process. Thus, the fuel input will be 10,000/.5
= 20,000 MMBtu per year.
After the retrofit, the new boiler is 80% efficient and the fuel input will be 10,000/.8
= 12,500 MMBtu per year.
The Savings would be:
= 20,000 MMBtu – 12,500 MMBtu
= 7,500 MMBtu per year.

Heat recovery systems (also known as heat exchangers) are unable to lower temperatures below the hot gas's dew point.

Correct! Wrong!

Flue gas temperatures that fall below the dew point will cause condensation. (Let's hope your boiler is a condensing one.

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