Question

As an energy engineer at your company, you find 16 large exhaust fans always running to exhaust general plant air (no localized heavy pollution). They are each powered by 24 kW electric motors with loads of 28 kW each. You find they can be turned off periodically with no adverse effects. You place them on a central timer so that four of them are turned off for 15 minutes each hour. At any time, four of the fans are off, and the other 12 fans are running. The fans operate 12 h/day, 345 days/year. By using the following costs, answer each question.

* Demand charge: 11 USD/kW/month

* Energy charge: 0.09 USD/kWh

a) What is the annual demand saving in USD?

b) What is the annual energy saving in USD?

c) What is the total saving in USD?

Answer 1