Commercial Office Space - Energy Savings

Let's consider a 10 story office building of 200,000 sq. ft. which will be lit with 2000, T-8 (32W) 3 lamp fixtures. Hours of operation are 5 days a week for 18 hrs/day (6 AM - 12 Midnight) including cleaning crews working after hours 5 days/wk from 8PM - Midnight.

In an environment like this, the Easylite ILS can address several key control applications to save energy:

• Daylight Harvesters to utilize the natural light near the perimeter sections (typically save 40-60% energy)
• Easy-Talk software to schedule lighting including shut off after hours and on/off for cleaning crews (prevents lights being left on over weekends, holidays)
• Easy-Talk software for Peak Demand shedding

Let's base our calculations on the following estimates:

• Daylight Harvesting can dim the perimeter fixtures (1/4 of fixtures) 40%, 9 hours per day
• Time of Day scheduling and zone control:
  • Dim computer work areas (1/3 of interior fixtures) (data entry, CAD, etc…) 50% from 6 AM to 6 PM.
  • Turn off all zones at 6 PM. Cleaning crews and employees will have local override capability. Estimate override of lights 25% of time between 6 PM & Midnight.
• Peak Demand Management - Will shed 50% of lighting load
  

Operating Hour Savings:

• Daylight Harvesting - 500 fixtures (1/4 of total) will run at 60% light output (& 60% power) from 8 AM to 6 PM.
  • kW Savings: 25.2 kW ((500 Fixtures x 84W x 60%))/1000
  • kWh Savings: 56,700 kWh (25.2 kW x 9 hrs/day x 5 days/wk x 50 wks/yr)
• Time of Day scheduling:
  • Dim computer work areas (667 fixtures) 50% from 6 AM to 6 PM
    • kW Savings: 28 kW ((667 Fixtures x 84W x 50%))/1000
    • kWh Savings: 84,000 kWh (28 kW x 12 hrs/day x 5 days/wk x 50 wks/yr)
  • Turn off all zones at 6 PM. Employees & Cleaning Crews will override 25% of time (note: analysis based on 75% of fixtures off (100% dimmed)
    • kW Savings: 126 kW ((1500 Fixtures x 84W x 100%))/1000
    • kWh Savings: 189,000 kWh (126 kW x 12 hrs/day x 5 days/wk x 50 wks/yr)
• Peak Demand Management - Dim facility to 50%
  • kW Savings: 84 kW ((2000 Fixtures x 84W x 50%))/1000
  • kWh Savings: Will vary based on length of peak demand window

Easylite ILS kW rating: 84kW - 50% reduction based on Peak Demand Management.
Will be 114.8 (168kW - (25.2 kW + 28 kW) to 42 kW throughout the day otherwise.

Easylite ILS Annual kWh: 426,300 - 43% savings (756,000 kWh - (56,700 + 84,000 + 189,000) kWh)

But this doesn't take into account the additional savings of reducing the A/C load by reducing light levels. General estimates predict that for every 3 W of lighting that are reduced, you will also save 1 W of AC energy.

Based on this, the Easylite ILS will save an additional:

28 kW of peak demand (84 kW x 1/3) and 45,791 kWh in consumption (329,700 kWh x 1/3 x 5/12) (based on 5 mo. of AC use).

Total Easylite ILS Savings are:
kW Savings: 112 kW (84 kW + 28 kW) - 67% Savings
kWh Savings: 375,491 kWh (329,700 kWh + 45,791 kWh) - 49% Savings