For example, it was quickly evident the installation of a variable frequency drive (VFD) for the cooling tower fan would not be cost-effective. Although this is a very common energy-conservation measure, the collected data on run hours compared to outdoor air temperature and other factors revealed the operation of the fan would be relatively infrequent throughout the year. Because the fan rarely needs to turn on, the benefits of controlling the speed at an optimal level are low.
In addition, at the time Carbon Lighthouse started work, no centralized building-management system (BMS) existed, which meant the Flood Building’s management team lacked significant control over the system. As a result, management was forced to run enough water through its building to cool and heat the building as if each day were the hottest or coldest day of the year.
Selected Measures
The following measures were selected for implementation based on Phase One analysis:
Improved Visibility: The engineering team installed a computerized BMS and sensor network that gives property management increased visibility and remote control of building operations.
Optimized HVAC: The engineering team improved the building’s HVAC system by programming the BMS with algorithms to continuously optimize the balance between the speed of the building’s water pumps and the temperature of the water flowing through them. This reduces the work input required by the entire system by providing the precise amount of cooling energy to the space. The controls incorporated real-time information about outside air temperature, building equipment conditions and building schedules.
- Cooling Tower Pumps : Pumps were maintaining excessively high flow through the cooling tower loop. Flow was reduced most of the year via algorithmic control, based on building, cooling tower and outdoor-air conditions.
- Condenser Pumps : Pumps were pumping an excessively high flow through the condenser loop with a very low approach temperature, or temperature differential between cold and hot streams, in the heat exchanger. Flow was reduced most of the year via algorithmic control based on building and outdoor-air conditions.
Upgraded Lighting: The engineering team completed a number of small lighting improvements, replacing and updating lighting throughout the building and loading dock. Remaining T12 lamps on magnetic ballasts were changed to T8 lamps with new ballasts. LED equivalents were used in place of MR16 incandescent lamps for lobby accent lighting. Inefficient high-intensity discharge lamps in loading docks were replaced with linear fluorescents, achieving greater energy savings than an LED equivalent for a fraction of the cost.
Building-wide energy and environmental benefits will tally up to 870 tons of annual carbon-dioxide savings and completely neutralize the Flood Building’s carbon footprint with respect to utility energy. The building’s carbon footprint was calculated using utility consumption data and the carbon intensity associated with the local utility power mix. Every utility service territory has a particular ratio of fuels (natural gas, hydro, nuclear, renewables and coal). The cleaner the power mix, the lower the carbon intensity of the average unit of electricity. By combining the carbon emissions associated with steam and electricity consumption, a baseline of 870 tons of CO2 was set. (For further reference, the Washington, D.C.-based U.S. Environmental Protection Agency provides the Emissions & Generation Resource Integrated Database as a comprehensive source of data on the environmental characteristics of electric power generation in the U.S.)
Implementation: Phase Two
An ongoing challenge in building energy projects is bridging the gap between upfront engineering and the actual, expected kilowatt-hours and Btu reductions from a variety of measures. If finding the savings is challenging, ensuring a project is implemented so the predicted savings are achieved can prove downright bewildering.
Time and again, wires are literally and figuratively crossed. Redundant or unnecessary hardware is installed because of a misalignment of incentives or a misunderstanding of objectives between the energy users and vendors. In the end, projects are rarely adequately commissioned through a complete measurement and verification process to ensure the system is performing as modeled.