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Copy and Paste This Permanent Link:http://www.distributedenergy.com/july-august-2009/greening-school-district.aspx

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Photo: © iStock/ lvinst

The San Diego Unified School District (SDUSD) lays claim to having one of the lowest utility costs per student in the country. It first initiated an energy efficiency program in 1994, and to date, the district has saved nearly $131.8 million in avoided energy costs. Today, its 220 educational facilities make up the second largest school district in California with over 132,000 students.

The policy of the district’s Board of Education now is to build all of its new buildings on a net-zero energy use basis. Building schools “green” with a low-carbon footprint and air conditioning is a real challenge. But the school district has a track record of success.

Over the past 10 years, SDUSD has reduced energy usage by 25% through installation of solar photovoltaic systems, efficient lighting, occupancy sensors, cool curtains, a dark campus policy, and an energy management control system (EMCS) to centrally monitor and control HVAC systems. A separate irrigation management control system was designed and installed to centrally control irrigation at 163 schools through 24-hour monitoring. 

Since 2003, the district has installed integrated rooftop photovoltaic arrays at 28 district sites and has plans for more installations. It continues to evaluate innovative ideas. The district’s energy management staff has gone on to establish environmental clubs at schools, and they work with teachers to integrate energy awareness into the curriculum.

As a result, the SDUSD has won half a dozen awards recognizing its achievements in energy efficiency and resource conservation. Since 1998, it has participated in the EPA’s Energy Star Label for Buildings Program, and in 2007 received the Energy Star Partner of the Year award. Over 150 buildings in the district have received plaques as Energy Star Label Buildings.

The district’s first work began in 1994, after it sold $42 million in bonds, according to J. William Naish, Energy/Utility Management Supervisor. Its Energy Efficiency Program included replacing old fluorescent lighting fixtures and exchanging 400,000 T-12 lamps with T-8s in 150 schools and installing 7,500 occupancy sensors. It also replaced 1,000 toilets with low-flush models with pressurized bladders. The projects paid for themselves in 18 months.

The energy savings leveraged bigger projects in the next phase of SDUSD’s energy efficiency program. A consultant was hired “and big things happened then,” says Naish. The projects included upgrading rooftop air conditioning units and tying them into a new EMCS. At the same time, the district created a permanent energy/utility management section, and in 1997, Naish was hired to run it.

By 2000, the major retrofit projects were completed and the bonds were paid off in eight years instead of 12. That year, the school district partnered with San Diego Gas & Electric (SDG&E), and its engineers identified additional projects. The utility provided incentives to help pay for retrofits as well. At a cost of $1 million, gym lighting was upgraded and occupancy sensors were installed in all teachers’ lounges. Occupancy sensors with both infrared and air movement sensors were chosen to avoid teachers being stranded in a darkened room if there was no air movement. With this dual technology, both infrared and air movement sensors need to detect an empty room to turn lights off, but only one type is needed to turn the lights on.

Solar PV Is Introduced
Once the initial large projects were up-and-running in 2000, Naish’s office initiated its pilot solar photovoltaic program and installed arrays at five elementary schools. Southern California Edison provided the funding through the California Public Utilities Commission rebate program. One array of 36 to 48 modules of PV paneling was mounted on the roof of a portable classroom at each school. An “Envirometer” was also installed to display current energy production and pollution savings. 

Photo: San Diego City Schools Bob Martin, planned projects program coordinator for San Diego Unified School District, shows students and teachers from Birney Elementary School a component of the solar roofing system atop the district’s Education Center.

The solar program was expanded in 2003 and began with a solicitation for proposals from private companies. Naish says the district was the first in the nation to seek a power purchase agreement and third party financing. Between 2003 and 2007, solar systems totaling 4 MW were integrated into new roofs on 28 schools. The district chose roof-integrated thin film technology, because of the concern over vandals breaking glass paneling. Integrating the system into the roof also saved future roofing costs.

Solar Integrated Technologies was selected to install and maintain the systems at 24 schools with funding provided by GE Energy Financial Services. UPC Solar funded installation at four additional schools and will provide funding for up to an additional 12 PV systems. The California Energy Commission provided incentives.

Naish says the district is paying a discount to SIT and UPC Solar of either 2.5% or 2.0% off the blended utility rate. Currently, it is 18 cents per kilowatt-hour for 20 years, for the electricity generated by the 28 systems.

“We can budget and predict utility rates” for this electricity, he says. “The risk that we took was that electricity will not go down,” says Naish. “The beauty where we sit ... If they don’t produce, we don’t pay.”

Naish says before the systems were installed, electricity use by the schools was costing the district $50,000 a year. Now Naish is predicting the systems will save $250,000 annually.

The biggest challenge with the PV systems, says Naish, came in 2007, when SDG&E doubled its demand charges for off-peak electrical usage over its on-peak demand charges. “This made solar so bad, it cost money to run the systems,” he says. The City of San Diego intervened in SDG&E’s rate case and in July 2008, the CPUC approved eliminating demand charges for solar installations. 

Naish says the district is eager to install another 4 MW of solar PV and already another 19 sites have been identified. But the district is finding it difficult due to problems with financing, given the current economic climate.

The district is looking for partners for additional distributed generation projects, such as microturbines and urban wind systems, and has an active rolling request for proposals. Naish says he received a lot of interest, and is now looking at all options that came through.

“I’d love to get solar and wind at every school,” he says. “It’s very teachable. My goals are always driven by cost. We have to spend the tax payers’ money right ... and we have the responsibility to teach students right.”

To Cool or Not to Cool?
When schools were built near the coast in San Diego, there was no need for air conditioning, but as the district expanded eastward into hotter territory heating, ventilating, and air conditioning became necessary. The EMCS installed in the late 1990s reduced costs in the 50 schools that had air conditioning and were the biggest users of electricity. The addition of solar systems on these buildings has cut costs even further.

Photo: San Diego City Schools Aerial view of Jackson Elementary School, in San Diego, CA

At the time the EMCS was installed, an energy manager was hired to operate it. Now 165 schools are connected to the EMCS through the district’s wide area network. The computer-based system controls and monitors air conditioning, heating, and ventilation systems; gym lighting; and walk-in refrigerator/freezer alarms. Naish estimates the system is saving the district $1.5 million annually in electricity and natural gas costs.

The EMCS provides a real-time view of the HVAC systems in each school, including temperature, occupancy, and lighting conditions for most rooms. Through its troubleshooting capabilities, the EMCS can identify problems before the site is affected and generate an alarm indicating a malfunction. The energy manager can diagnose and correct the problem from the EMS keyboard before it is even noticed at the school.

Naish says the department now has two full-time EMCS operators. They work with the mechanics in the field to make sure unoccupied schoolrooms are not being air conditioned, for example. It is difficult to shed loads now, because the set point for air conditioning is 78 degrees, although there is some flux with equipment, up from 75.5 degrees where temperatures had been kept for some years. Classrooms never get hotter than 78, Naish says. When he arrived in 1997, set points were kept at 68 degrees with no oversight.

Heating and cooling is programmed to function only during school hours, or office hours. Override buttons can be used to turn units on in specific rooms if it is being used after hours. Scheduling can generate 80% of the $1.5 million that the district estimates the EMCS saves annually in energy costs. The remaining savings are derived through control of airflow to rooms, the amount of outside air delivered, and temperature adjustment based on outdoor conditions. “We’ve been managing the cooling loads long that enough teachers no longer complain,” says Naish.

When he started the job in 1997, he worked with the district board and a dedicated staff to develop principles. There were many sick building complaints but the staff addressed them right away and was able to change the nature of the issues. Naish describes it as “growing and learning.” Right now, everyone is cooperating, he says.

In 1999, the district hired Healthy Buildings International Inc. to review indoor air quality (IAQ) as part of its energy retrofit program. It developed and updated IAQ information for use in existing air-conditioning, building construction, and operation, and wrote guidelines for use of thermal displacement ventilation in new air-conditioned projects. Since then, it has monitored IAQ programs in 40 air-conditioned schools.

As of 2008, the district’s Board of Education set a policy that school sites will not be air-conditioned unless they meet certain exceptions: The buildings have no operable windows, and if noise problems, require windows to be kept closed (like being under the airport flight path).

The board will allow school-funded air conditioning as long as overall utility consumption is reduced and the site pays all upfront costs, plus ongoing costs, including utility charges, regularly scheduled maintenance, repair and replacement costs, and custodial time, to ensure regular and proper cleaning of interior surfaces. Most school sites have found these requirements cost-prohibitive.

What’s Left to Do? 
Naish’s view is that there is always more to do. For example, his staff studied adding insulation to the walls and in ceilings of buildings. Under certain circumstances, they found it would increase costs. By making buildings tighter, heat starts permeating structures later in the afternoon, and the latent heating load would shift to later in the evening. Buildings would still be warm in the morning, increasing air conditioning work.

Tons of windows are not yet dual-glazed, says Naish. He is hoping there might be dollars coming from the federal stimulus package to replace those windows.

The district continues to look for ways to cool schoolrooms with zero gain—in other words, to not add to existing energy costs. Naish and his staff are looking at displacement ventilation that uses 20% to 30% less energy. The system would be appropriate for rooms with very high ceilings well over 9 feet, such as auditoriums and multipurpose rooms. It is used widely in Europe—in particular, the Scandinavian countries—since the 1970s, where it is now considered to be a proven technology.

Low-volume air is interjected at floor level from specialized package rooftop air-conditioning systems with digital scroll compressors. Cool air coming in at the floor level replaces rising warm air with the bodies in the room acting as chimneys. The air is then exhausted at ceiling level.

Naish says this system has been successfully installed in casinos where the chimney effect removes the smoke. He predicted electrical bills would be decreased 60% to 80%. For more information, visit www.xetexinc.com or other sites on the Internet.

The district has also checked out the Solatube Daylighting System. A rooftop optical dome redirects low-angle sunlight through a tube built into the roof ending at the ceiling where the daylight is diffused into the room. The appearance on the ceiling is that of a fixture set into the ceiling.  More information is available at Solatube’s Web site, www.solatube.com.

The Solatube reduces lighting costs by 85%, “but they are expensive, and we’re so efficient now,” says Naish. Lighting levels in rooms are at 50-foot candles, down from 120, so there is much less tradeoff, he explains.

While the staff has studied thermal energy storage, there is not too much interest in it. What they are going ahead with, at least with an initial installation, is the variable refrigerant volume (VRV) system that would cut air conditioning costs by 30%.

Evan Leslie, project management supervisor in the Facilities Management Unit at SDUSD, explains it this way: The VRV system uses one outdoor condenser that supplies refrigerant to five or more classrooms, each with an indoor fan coil unit and a thermostat. The VRV system decides how much load is required for each room and allows several spaces served by the same condensing unit to be in either heating or cooling mode at the same time. The package units can be moved to where the load is, explains Leslie. He notes they are too heavy for schoolroom roofs.

The condensers use inverter-driven compressor technology to supply refrigerant to a routing box that communicates with the fan coils to supply the refrigerant via electronic expansion valves for both heating and cooling modes. If the system is calling for both heating and cooling in separate rooms, the heat produced in the cooling zones is recovered and used to heat the refrigerant for the zones calling for cooling. The heat generated from cooling is used to warm the air in the spaces calling for heating.

Leslie explains that energy savings have ranged from 15% to 35% when compared to packaged rooftop units and central plants. They exceed California Energy Commission Title 24 energy standards by 15% to 20%. The noise from the indoor fan coil units average about 35 db(A), while a typical conversation creates around 60 db(A), he says. VRV systems can be integrated into EMCS controls and require less maintenance than packaged rooftop units and central plants. They’ve been installed in schools, hospitals, office buildings, and banks for over 20 years across Asia, Europe, and South America, he says.

He says the first VRV installation will be at the Ellen Browning Scripps Elementary School, now being designed. Construction is expected to start during the fourth quarter this year. The VRV system will be installed by mid-2010. He says a VRV system costs $30 to $40 per square foot, while displacement ventilation will cost between $60 and $80 per square foot. He says Solatubes cost about $3 per square foot.

Educational Mission
Mindful of the district’s educational mission, Naish says energy is being incorporated into the curriculum. “It’s unfortunate that schools do green things and kids don’t know it. We’re trying to bridge that.”

Naish’s office created a solar activity kit with extra solar panels that part-time teachers are using to teach students the rudiments of solar installations. “A teacher in the School of Science and Technology at San Diego High has his class make biodiesel in chemical labs from grease generated in our cafeterias,” he explains. 

The biodiesel is being burned in 30 school buses, and they would like more to run all 100-plus buses. Furthermore, the school district avoids paying to have the grease disposed of, so it’s saving more money. One of the staff people in the asphalt shop, where diesel fuel was being used to clean tools, picked up on the idea and introduced biodiesel to clean the tools instead. It has eliminated issues raised by the EPA and Cal OSHA over the use of diesel fuel in the work area.

Building Green
Lee Dulgeroff is director of project management for Prop S, the $2-billion proposition approved by San Diego voters in November 2008 to upgrade schools in the district. Prop MM was approved five years ago, raising $1 billion that has already been spent. Dulgeroff manages all capital projects. There are now 200 in various stages of design and construction.

Dulgeroff explains that the district’s Board of Education, in 2003, adopted the construction and demolition standards created for schools, called Collaborative for High Performance Schools, and they now incorporate the latest green building standards. All retrofits and new construction adhere to these standards. “We are using sustainable design, materials and products,” he says.

And life cycle costs are emphasized in design. Two new schools are under construction, and another eight buildings are being designed. Three are two-story, well-insulated buildings replacing portable classrooms. Dulgeroff says every project will be looking at incorporating solar photovoltaic systems into its design. When third parties are involved in constructing a project, such as a solar installation, Dulgeroff’s office facilitates the work.

The eight buildings in design are intended for career technical education. The Sustainable Technologies Program Building at Scripps Ranch High School will prepare students in environmental technology careers—green collar jobs, says Dulgeroff. The Green Construction Building being designed at Hoover High School will teach students sustainable construction, including reuse of materials. 

Most of the retrofitting involves modernizing about 180 schools. New dual pane windows with low E values, new cabinetry and doors and LED lighting are being installed. The designs maximize daylighting. Dulgeroff says Naish’s Energy/Utility Management unit checks out each project looking for ways to reduce energy. Once they identify something, Dulgeroff’s group does the work.

VRV systems, described by Leslie above, will be integrated into the construction of all major retrofits, as well as new buildings if air conditioning is needed, Dulgeroff says.

It is hard to identify the energy cost-savings with retrofits, Dulgeroff says, because retrofitting is not an exact science. “Cost savings are important, but it’s the right thing to do for the environment and to improve the world those students live in.”