Energy Efficient System’s Savings

Objective

To estimate the energy and GHG emission savings from an energy efficient air conditioner.

Outcome

Students will realize that energy efficiency is a great way to save energy and GHG emissions and make the design choices accordingly.

Requirements

None

Prerequisites

Conceptual knowledge of

1. Electrical energy consumption
2. Carbon Footprinting
3. Tonnage of Operational ACs in the college

Given Data

1. Increase in efficiency of the Air conditioning system = 10%
2. Average daily operation = 8 hrs
3. Average monthly operation = 22 days 
4. Monthly energy consumption of a typical ceiling fan ~12 kWh
5. Carbon Emission Factor for Electricity = 1.19 $$\frac{\:\text{kg CO2e}}{\:\text{kWh}}$$
6. 1 tree absorbs approximately 250 kg of CO₂ in its lifetime.

Procedure

Step 1: Students find out the total air conditioning load (TR – Ton of Refrigeration) of the campus.

Step 2: Convert TR to kW.

Step 3: Estimate the air conditioning energy consumption for a month.

Step 4: Select and determine energy savings for an energy efficient air conditioning system.

Step 5: Estimate the equivalent number of fans that can be operated due to these monthly savings.

Step 6: Estimate the GHG emissions saved (kg CO₂e).

Step 7: Estimate the equivalent number of trees planted through electricity savings.

Sample Calculations

Step 1: Air conditioning load in college campus (TR) = 40 TR

Step 2: Air conditioning load in college campus (kW) = TR x 3.517

= 40 x 3.517

= 140.7 kW

Step 3: Air Conditioner’s monthly energy consumption (kWh)= Air Conditioning Load (kW) x avg. daily operation (hrs) x no. of operation days in a month

= 140.7 x 8 x 22 

= 24,763 kWh

Step 4: Energy savings due to increase in efficiency (kWh) = % increase in energy efficiency x monthly energy consumption (kWh)

= 0.1 x 24,763

= 2,476 kWh

Step 5: Equivalent no. of fans that can be operated due to increased efficiency= $$\frac{\:\text{Energy savings due to increase in efficiency (kWh)}}{\:\text{Monthly energy consumption of a ceiling fan (kWh)}}$$

= $$\frac{\:\text{2476}}{\:\text{12}}$$

~206 fans

Step 6: GHG Emissions saved (kgCO₂e) = Emission Factor for Electricity (kg CO₂e/kWh) x Energy Savings (kWh)

= 1.19 x 2,476

= 2,947 kg CO₂e

Step 7: Equivalent no. of trees planted =$$\frac{\:\text{GHG Emissions saved (kg CO2e)}}{\:\text{Carbon Absorption Capacity of one tree (kg CO2e)}}$$

= $$\frac{\:\text{2946.3}}{\:\text{250}}$$

~12 trees

References

Supplementary Notes Section: Carbon Footprint