DER Applications
DER systems can provide a host of benefits to federal facilities, including the following:
- Improved power quality
- Standby power
- Peak shaving
- Low-cost energy
- Stand-alone systems
- Combined heat and power
DER for Improved Power Quality
Most federal facilities need to address power quality if they haven't already—particularly laboratories, R&D facilities, hospitals and clinics, and data, communications, and control centers. Where existing power quality equipment is old, inefficient, or outdated, new DER technologies may offer improved efficiencies and more environmentally benign operation.
Electronic equipment such as computers, adjustable-speed drives, and motors can be highly susceptible to changes in power quality. Although the power generated by an electric utility starts out as a clean 60 Hz sine wave, load and generation changes, equipment switching, and electronically controlled loads on the customer and utility sides can all cause disturbances to the electrical waveform, as shown in the illustrations at right.
Some symptoms of poor power quality include:
- Voltage sags and swells, when the voltage is too high or too low for a period of several cycles to several minutes
- Voltage spikes, which are sharp, randomly occurring pulses in the voltage
- Momentary outages, which cause complete interruption of electricity service for up to 5 minutes
- Harmonic distortions, in which harmonic frequencies produce a variation in the pure sine wave.
Some DER technologies, such as uninterruptible power supplies (UPS) and other distributed storage devices, are designed specifically to address such power quality issues. And most DER technologies can improve power quality, even if they were installed for a different purpose.
DER for Standby Power
If you have numerous electrical power outages at your facility, or if it takes a relatively long time to restore service, your power supply has low reliability. A standby power DER system may provide a solution.
According to the U.S. Department of Energy's Strategic Plan for Distributed Energy Resources (PDF 672 KB, 34 pp), published in September 2000, cellular communications companies, airline reservations, and credit card and brokerage operations indicate that power outages can cost tens of thousands to millions of dollars per hour. Download Adobe Reader.
At your federal facility, what losses do you incur because of power outages? Lost research time, lost data or specimens, damaged equipment? Can you place a cost on the downtime at your facility due to a power outage? If so, DER systems that are designed to provide backup or standby power on an as-needed basis may be cost-effective. You could also install a DER system for dedicated power to mission-critical loads. In this scenario, the power generation equipment would run in a baseload mode, providing prime power for critical programs, facilities, or equipment, with the grid acting as your source of backup energy.
Federal facilities that could benefit the most from standby power DER systems include:
- R&D facilities
- Laboratories
- Hospitals and clinics
- Schools.
Data, communications, and control centers should also consider standby power to avoid costly data loss or hazardous communications outages. And in defense installations, DER systems can power mission-critical loads to enhance energy security at their facilities.
DER for Peak Shaving
The PV system installed at the U.S. Postal Service Marina facility is linked to the building's energy management system in an experimental peak shaving application.
Most commercial facilities are charged a higher rate during hours of peak energy use, based on their local utility's time-of-use rates or capacity constraints. This peak demand charge is incurred monthly, based on the highest peak usage rate of the facility, even if it's only for a few hours. In certain areas and for certain facilities, peak demand charges can make up most of the electric bill. Strategically controlling these peak demand charges by using DER can generate significant cost savings.
The DER technology you select will be used anywhere from 200 to 2000 hours per year, so it will be necessary to evaluate the trade-offs between capital cost and system efficiency. You will also want to consider long-term fuel supply and costs when selecting an appropriate peak-shaving DER technology.
Federal facilities paying high peak demand charges should consider using DER technologies to offset those energy costs. So should facilities located in areas suffering from severe capacity constraints. Peak shaving can benefit the customer by saving money; the utility, by offsetting the need for costly generation or distribution upgrades; and the community, by reducing or eliminating the potential for rolling blackouts or brownouts at times of peak energy use.
DER for Low-Cost Energy
The U.S. Navy installed this PV carport to shade vehicles, while producing clean, reliable energy to the facility.
In today's rapidly changing utility industry, DER systems can provide a hedge against electricity cost fluctuations. At the same time, they provide power quality, reliability, and enhanced energy security. Utilizing renewable energy DER technologies and combined heat and power systems can bring about further fuel supply and cost benefits.
Federal facilities located in areas with high fuel or electric costs should consider using DER systems to reduce energy costs at their site. Federal agencies can target facilities in states that offer incentives for using DER. State and local programs, utility rebates, and other financial incentives (PDF 226 KB, 4 pp) can lower the first cost of some DER technologies in certain areas. California, for example, offers substantial rebates for certain DER systems to offset the growth in electricity consumption in the state. Net metering programs, now offered in 30 states, allow a facility's electric meter to spin backwards. So a facility pays only for the net electricity used. Particularly when financial incentives such as these are considered, DER can provide a low-cost energy alternative to central-generation electricity. Download Adobe Reader.
For more information on state, local, utility, and selected federal incentives for renewable and distributed energy systems, see the Database of State Incentives for Renewable Energy (DSIRE).
DER for Stand-Alone Systems
DER systems can be most cost-effective in areas where grid-supplied electricity is not available or is too costly to access. The cost of extending grid lines can be significant, ranging anywhere from $10,000 to $40,000 per mile depending on the location. For this reason alone, DER technologies can be comparatively inexpensive for stand-alone systems in comparison to other applications. However, DER can also provide other benefits when facility managers are considering stand-alone (off-grid) vs. grid-connected systems:
- DER systems provide fuel flexibility, to match the fuel availability of the location.
- Renewable energy systems can lessen or avoid reliance on fossil fuels; this reduces or eliminates the adverse effects of fuel spills that can occur during fuel transportation and storage.
- At sites where the cost of maintaining grid lines or distribution equipment is high, DER systems can provide significant savings through reduced operation and maintenance.
- Grid lines may be unaesthetic or detract from an otherwise pristine view shed. In those cases, DER systems can be an on-site generation solution, improving aesthetics and reducing noise.
- Some DER systems generate electricity without producing harmful emissions. Other DER systems provide energy with substantially reduced emissions in comparison to traditional central generating stations.
Often, hybrid systems are the best approach for stand-alone applications. They can provide increased reliability and redundancy to protect against outages. When renewable energy technologies are used, for instance, batteries are required to provide power on cloudy days, or when the wind doesn't blow. A backup engine generator set may also be required, depending on the needs of the site. For these reasons, stand-alone DER systems may be more costly than grid-connected systems on a per-kW basis. However, compared to the cost of grid extensions, DER can often be the most economical choice.
The National Park Service, Fish and Wildlife Service, Forest Service, and Federal Aviation Administration are just of a few of the agencies that have the best opportunities for off-grid DER systems. Off-grid facilities that need electric and thermal energy can include comfort stations; visitor centers and kiosks; data, radar, and communications systems; signage; field stations; and guard shacks.
See the case studies, which are available as PDFs, on Pinnacles National Monument (PDF 183 KB, 4 pp), Joshua Tree National Park (PDF 151 KB, 2 pp), and Channel Islands National Park (PDF 212 KB, 2 pp) for more information on successful stand-alone DER systems. Download Adobe Reader
The National Renewable Energy Laboratory has developed a software tool designed specifically to optimize renewable hybrid energy systems. HOMER, the Hybrid Optimization Model for Electric Renewables, is downloadable from the NREL web site.
DER for Combined Heat and Power
Combined heat and power (CHP, also known as cogeneration) can provide thermal energy for buildings or processes while simultaneously generating part of the electricity needed at the site. More on CHP.
Additional Resources
For more information, see applications on the DOE DER Web site.