Longer-term solutions are energy-saving measures that require more investment of capital or longer payback periods, but often result in larger energy and cost savings. Some general ideas include:
- Set a reduction goal. Setting a goal can raise the topic of energy efficiency in the minds of your staff. In one example, the local initiative Sustainable Chicago 2015 called for a 10 percent reduction in energy use in municipal buildings.
- Hire a shared energy manager. Having dedicated staff with specialized knowledge and responsibilities focused on improving facility energy use can take the load off busy facility managers. Sharing an energy manager’s services can be a convenient way for municipalities with resource constraints to improve services and reduce costs.
Commissioning is the process of ensuring that systems are designed, installed, functionally tested, and capable of being operated and maintained according to the owner’s operational needs. Doing so can cut energy bills by 10 to 15 percent or more, and often provides a simple payback period of less than one year. When this process is applied to an existing building that hasn’t been commissioned before, it’s called retrocommissioning. When it’s applied to a building that has been commissioned before, it is called recommissioning. Recommissioning is recommended every three to five years to maintain top levels of building performance. In another type of commissioning—ongoing commissioning—monitoring equipment is left in place to allow for continuous diagnostics.
Building Automation Systems
Sometimes called energy management systems, BASs save between 5 and 15 percent of overall building energy consumption and can also improve occupant comfort. However, due to their complexity and high cost, BASs typically only become cost-effective in buildings larger than 50,000 square feet (ft2). Older or poorly maintained buildings can also benefit greatly from a BAS retrofit, sometimes yielding savings of over 30 percent. For existing barebones BAS systems, submeters and wireless controls can be added to provide more-robust information for setting baselines, benchmarking, troubleshooting, identifying areas for improvement, and evaluating performance. Recently, prices of submeters and wireless controls have dropped markedly, making them even more attractive data-acquisition tools to improve building performance.
“Cloud” (Internet-enabled) thermostats can offer much of the functionality, analytic abilities, and energy-saving opportunities of a BAS at a much lower cost, making them a great choice for buildings that are less than 50,000 ft2. Even better, cloud thermostats are rapidly increasing in sophistication and may also soon provide a central control point for supplementary loads such as lighting, water heating, and plug loads.
Energy Analytics Software
A growing number of companies offer both single-building and multiple-unit portfolio analysis, allowing customers to pinpoint poorly performing systems or buildings. Identifiable problems may include malfunctioning or poorly tuned HVAC systems or whole buildings that are performing at subpar levels compared to their neighbors or other buildings in a portfolio.
Indoor Lighting Measures
LED lighting. LEDs offer several advantages over conventional light sources, including high efficiency, long life, and superior control. These characteristics and falling prices have made LEDs a viable solution for a growing number of office building applications, including exit signs, task lighting, recessed downlighting, and ambient lighting.
LED troffers offer promising benefits in the right applications. Fluorescent troffers are the most common type of lighting fixture found in US commercial facilities, accounting for 50 percent of existing luminaires. The best LED troffer products outperform their fluorescent cousins, but at a first-cost premium. You can replace fluorescent troffers with new LED troffers, via LED retrofit kits, or by replacing the fluorescent tubes with tubular LED products.
When buying LED-based products, ask for performance data based on standard tests performed by accredited laboratories. When comparing LEDs to other options, be sure to include cost savings from reduced maintenance due to LEDs’ long lifetimes in the total calculation. Make sure that the LED solution will provide the quantity and quality of light you need by starting with a small test case.
Fluorescent lamps. If your facility uses T12 fluorescent lamps or commodity-grade T8 lamps, relamping with high-performance T8 lamps and electronic ballasts can reduce your lighting energy consumption by 35 percent or more. Adding specular reflectors, new lenses, and occupancy sensors or timers can double the savings. Payback periods of one to three years are common.
Lighting controls. Using energy-efficiency light sources is only one part of the process of reducing the energy used by a lighting system. A well-designed control system will provide the right amount of light where and when it’s needed, and it will cut lighting energy use by 5 to 60 percent, depending on the baseline conditions and the control strategies used. In addition, using lighting controls may qualify you for participation in utility demand-response programs. Advanced control systems can also help lighting maintenance by signaling lamp outages and monitoring usage and output levels to indicate when they fall below required levels.
Daylighting. Daylight can improve the ambience of an office and reduce the need for electric lighting. Dimming ballasts, or dimmable LED drivers, and daylighting controls can be used to reduce the amount of electric light used when daylight is present.
Outdoor Lighting Optimization
Lighting roadways and other public spaces (recreational areas, parking lots, and public transportation depots) can consume a significant portion of a municipality’s energy footprint. While it’s essential to focus on security requirements, pedestrian and traffic safety, economic development and aesthetics, many energy-efficiency opportunities are available. The options presented are generally designed to reduce energy use, costs, light pollution, and waste light while maintaining or improving light quality; however, it’s important to get detailed specifications for your facility to ensure that the technologies you’re evaluating will meet your building’s unique needs.
Reducing light levels. Parking lots are often overlit—an average of 1 foot-candle of light or less is usually sufficient. Dimming and occupancy-sensing controls can add to energy savings in parking lots.
Installing more-efficient light sources. The most common lamps used for outdoor lighting are high-intensity discharge (HID) sources—metal halide and high-pressure sodium (HPS). Fluorescent and induction lamps are also used in parking lots, but LEDs have become the most efficient alternative as their performance has improved and prices continue to decline.
LEDs can be a good choice for parking and streetlighting applications because LED fixtures perform well in the cooler conditions that are typically found outside at night, and because LEDs work better with controls than the incumbent HID products (HPS and metal halide). In field testing of bi-level LED lighting combined with occupancy sensing at a parking garage on the California State University, Sacramento campus, energy savings of 78 percent were reported between the hours of midnight and 6 a.m. due to the majority of fixtures operating in low-capacity mode. The project report, Bi-Level LED Parking Garage Luminaires (PDF), prepared by the California Lighting Technology Center, also noted 24-hour energy savings of 68 percent compared to the incumbent HPS lighting system.
The ability of LEDs to work well with controls has encouraged several companies to develop streetlight networking capabilities. For more information, check out the Northwest Energy Efficiency Alliance’s Technology and Market Assessment of Networked Outdoor Lighting Controls (PDF) report. Taking the concept a step further, some companies are partnering with municipalities or other government entities to develop systems that use networks of LED streetlights as a backbone on which to later support functions such as traffic control and public safety. Read Greentech Media’s article Will Street Lights Become the Nodes of the Networked City? to learn more.
LEDs also offer long life, which reduces the maintenance costs associated with lamp replacement, especially for streetlights that require bucket trucks or lifts to change the lamps. Plus, LEDs provide a more even light distribution and produce less light pollution and light trespass—properties that improve aesthetics and contribute to energy savings.
The US Department of Energy (DOE) Municipal Solid-State Street Lighting Consortium provides specifications, financing guidance and tools, and demonstration results. The DOE Better Buildings Alliance, on its Adopt High-Efficiency Lighting for Your Parking Lot page, provides more information, including a sample specification, some case studies, and information on the Lighting Energy Efficiency in Parking Campaign. The Alliance estimates that using LEDs can cut energy use by 40 percent or more, depending on the application.
High-efficiency HVAC units. A highly efficient packaged air-conditioning/heating unit can reduce cooling energy consumption by 10 percent or more compared to a standard-efficiency, commercial packaged unit. Single-zone variable speed rooftop units (RTUs) can also reduce cooling energy. Select equipment that has multiple levels of capacity—that is, compressor stages—with good part-load efficiency.
Advanced RTU controllers. Retrofitting existing RTUs with advanced packaged controllers improves functionality and offers potential for significant energy savings. Estimates and preliminary field-test results indicate energy savings of 20 percent to over 50 percent with a typical payback period of one to four years. Energy-saving features can include variable- or multispeed supply fan control, demand-controlled ventilation, and improved economizer control. Additional features can include demand response, remote monitoring, and fault detection and diagnostics.
Demand-controlled ventilation. For office spaces that have large swings in occupancy levels, energy can be saved by decreasing the amount of ventilation supplied by the HVAC system during low-occupancy hours. A demand-controlled ventilation (DCV) system senses the level of carbon dioxide in the return airstream, uses it as an indicator of occupancy, and decreases supply air when carbon dioxide levels are low. DCV systems are particularly applicable to variable-occupancy spaces like auditoriums, meeting rooms, and cafeterias.
Boiler retrofits. Savings from boiler retrofit projects can be significant. Newer boilers feature a variety of efficiency improvements that can justify replacing older boilers before they fail. Improvements include condensing heat exchangers, sealed combustion, electric ignition, and fan-assisted combustion. Smaller boilers are more efficient than larger ones, and grouping multiple smaller boilers not only allows staged operation of each unit at its highest efficiency point, but also provides redundancy. If a larger boiler isn’t ready to be retired, a smaller boiler can be added to serve the base heating load, reserving the larger boiler for additional heating as needed.
Reflective building roof coating. If the roof needs recoating or painting, consider white or some other highly reflective color to minimize the amount of heat the building absorbs. Cool roofs can often reduce peak cooling demand by 10 to 15 percent. For a list of suitable reflective roof coating products, visit the Energy Star Roof Products website.