A commitment to sustainability and energy efficiency has produced a unique combination of distributed generation systems at California State University Northridge.

By Lyn Corum

California State University Northridge (CSUN) has a 12-year-old thermal-energy storage system used for load shedding, six microturbines that for five years have been providing power during peak periods, and two operating solar photovoltaic (PV) systems four and two years old, respectively. Earlier this year, the campus dedicated its 1-MW fuel-cell cogeneration system, identifying it as the single largest fuel-cell plant at any university campus in the world. Combined, the four systems supply 23% of the campus’s electricity needs, and they provide heating and cooling.

Located in the San Fernando Valley on 356 acres with approximately 35,000 students, CSUN is one of the largest and fastest-growing schools in the 23-campus state university system. A growing population is requiring that California’s state colleges confront increased enrollment demands.A

s a result, CSUN is in the midst of an aggressive capital-construction campaign. In 2003, facing the possibility its nine-year-old central plant was already reaching peak cooling capacity, physical plant management commissioned a study to evaluate its growth capacity. The study verified management’s conclusions about the central plant’s limitations. A follow-up study looked at these results in the context of the campus’s 2035 master plan and concluded that all new buildings would need their own remote cooling—and in some cases remote heating—capacity.

Installing heating and cooling in individual buildings during construction would result in higher capital-construction costs for equipment and infrastructure and increased energy costs per square foot due to a poorer energy-efficiency performance.

Maintenance and operating costs would also increase disproportionately.
After considering alternatives, a third study looked at the feasibility of operating a combined heat and power plant utilizing fuel cells to serve immediate and planned heating needs. Cooling needs would be met by a new chiller plant powered by the fuel cells.

The study estimated a fuel-cell plant would cost $5.62 million per megawatt and have an annual operating cost of $337,200. The actual cost of the 1-MW system was $5.26 million, including construction and the first year’s warranty and maintenance costs. It is still too soon to know what actual operating costs will be.

Project savings, when compared with costs to support individual building systems and when combined with the new chiller plant now under construction, are estimated to be $65,000 in annual campus maintenance and $235,000 in annual energy costs. Furthermore, there will be a $7 million reduction in future capital-construction costs and total estimated life-cycle savings of $14.5 million.

CSUN had some help with the fuel-cell plant’s costs, reducing them to $2.51 million. Southern California Gas Co. awarded CSUN $2.25 million in state-sponsored self-generation incentive funding, and Los Angeles Department of Water and Power (LADWP) provided a $500,000 rebate. Once a new high-efficiency chiller system is installed, which will be partnered with the fuel-cell plant, LADWP will provide another $336,000 rebate check.

First, Thermal-Energy Storage
Tom Brown, executive director of physical plant management at CSUN, began his innovative energy-efficiency program in 1994 with the thermal-energy storage system. It was designed along with a new central plant. The need for both had already been identified before the 1994 Northridge earthquake, which produced a great deal of damage to the campus.

CSUN’s onsite power venture began with photovoltaics.

Solar panels cover parking spaces on the campus at Northridge.

Following the earthquake, the central plant was built. In addition, three electric centrifugal chillers totaling 3,600 tons and the thermal-energy storage were installed. The three chillers generate chilled water at 39°F during the off-peak night hours when electrical rates are at their cheapest. The water is immediately stored in the 2.3-million-gallon storage tank. The stored chilled water is then used for cooling, particularly during peak summer hours from 1 p.m. to 5 p.m. This allows the chillers to be shut down to shed electrical load. The tank is completely depleted in the four peak hours given the current load, Brown explains.

As an indication of how fast the campus has grown, Brown says when the thermal-energy storage system was first commissioned one filling of the tank could serve the campus for days.

The two high-efficiency chillers are being added to accommodate the two newest buildings already in design. The Biology Science building will start construction soon, while the Performance Arts building is being designed and will start construction within the next few years.

Capstone microturbines

Next, Microcogen
CSUN was the recipient in 2001 of six 30-kW Capstone microturbines that the National Fuel Cell Research Center (NFCRC) at the University of California–Irvine received in a grant from the South Coast Air Quality Management District (AQMD). NFCRC was to arrange for the installation and subsequently test their performance. CSUN volunteered to be a host site, and in return it agreed to pay for the fuel and maintain the equipment. According to NFCRC, the total installation cost was $108,000.

The six natural gas–fired Capstones at CSUN began operating in December 2001, and NFCRC monitored their performance from May 2002 to December 2004. The microturbines are operated between 10 a.m. and 8 p.m. for peak shaving. The waste heat recovered is being used in the campus hot-water system. The Capstones supply 3% of the campus’s electricity needs.

AQMD provided the monitoring data collected from 2002 through 2004 for this story. Capacity factors and load factors varied considerably in 2002, but performance began to be more consistent as 2003 progressed. All six microturbines were operating at capacity factors and load factors between 74% and 85%, with few exceptions, throughout 2004. These numbers were consistent with those of the other microturbines monitored by NFCRC during the same period. By July 2004, the microturbines were each consistently producing between 10,000 and 19,300 kWh per month.

In 2003, the campus installed its first solar photovoltaic system in one of its parking lots; the system also provides shade for cars. The 75-watt solar panels were purchased from Shell Solar, and a team of student engineers helped install the prewired panels. The $2 million 225-kW project saves $50,000 annually according to Brown. LADWP and Southern California Gas Co. provided $1.7 million in incentives.

In doing its own research, engineering, and installation, Brown says, the staff learned that the convention of PV installers is to derate the inverters on the theory that the full nameplate-rated capacity of the panels will never be achieved.

Brown recalls that many installers claimed the inverters would be less efficient if oversized, while the inverter manufacturer disputed that. In his opinion, it is unlikely that solid-state inverters like those installed on the CSUN system will be less efficient if sized at the full rated capacity of the PV system. Instead, if they are undersized they will incur more failures due to overheating, etc. “We sized our inverters properly and have had no problems,” he says.

The second solar PV project was commissioned in 2005, also on a parking lot and providing shade for cars. Rated at 467 kW, the system has nearly the same footprint as the first project. But the 165-watt panels, purchased from Sharp, are more densely configured. The second project cost $3.4 million and received $2.3 million in incentives from the same utilities.

Together, the two systems supply 2% of the electricity used on the campus. The inverters for the second system are installed in a small structure with a glass window facing a walkway next to the parking lot so passersby can watch them at work and monitor the electricity produced.

As for cleaning the panels, Brown relies on rainfall. After monitoring the power production, he concluded there is little degradation from dust and dirt falling on the panels.

New Power Arrives
The 1-MW, natural gas-fed Direct FuelCell 300MA plant, manufactured by FuelCell Energy Inc. and dedicated on February 23, supplies 18% of the campus electricity needs. Furthermore, it allows the campus to build its infrastructure more quickly to serve new buildings as they are built.

Alliance Power Inc., FuelCell Energy’s partner, supplied the four 250-kW cells. FuelCell Energy is providing operations and maintenance and trained CSUN personnel onsite during commissioning. Physical plant staff, aided by campus engineering students, not only wrote specifications and the request for bids but also constructed the plant. CSUN physical plant management provided overall project management.

Alliance Power also provided technical-consulting services during the design and construction phase. P2S was the engineer of record and developed the civil, mechanical, and electrical design for the facility. Digital Energy produced initial studies and technical evaluations before the contract for the project was awarded. It also coordinated startup and commissioning activities. All work was completed within a one-year time frame.

The fuel-cell plant will be married to a 2,000-ton satellite chiller plant to be built in the reconditioned 1957 steam plant located immediately adjacent to the four fuel cells. The power generated by the fuel cells will drive the two 1,000-ton chillers once they are installed. Currently, the power is fed into the campus’s distribution system. The fuel-cell plant is connected to and operates in parallel with the campus’s high voltage infrastructure and the local utility grid.

The fuel-cell plant has a rated electrical efficiency of 47%. The thermal energy recovered from the plant’s exhaust stream supplements the system that heats the campus buildings, thereby boosting the estimated overall plant efficiency to about 83%.

Brown takes particular pride in the barometric thermal trap he designed to recover waste heat. Built by the physical plant staff—who nicknamed it “The Birdhouse” because of its appearance—it gathers the multiple waste-heat streams from each of the four fuel cells, where the waste heat exits at 650°F to 750°F.

After the wastestreams mix and are drawn through the barometric thermal trap, the waste heat travels across the first-stage heat-recovery coil, where it gives up most of its heat, dropping to 170°F. That heat warms the water looping through the campus to heat buildings. A separate loop will soon be built to take the exhaust heat that passes over the latent heat-recovery coil, leaving at a condensing temperature of 140°F, to the nearby student union to heat domestic hot water and swimming pool water.

Recycling Carbon Dioxide
One of the innovative side projects Brown also talks up is the plan to recycle the carbon dioxide contained in the fuel cells’ waste heat. It adds a sustainable element to the fuel-cell plant. The carbon dioxide is a byproduct of the natural-gas reformer that extracts hydrogen in the fuel-cell cycle. While most carbon-dioxide savings are credited to the fuel cells’ non-combustion fuel-reformation process and the plant’s high efficiency, the exhaust nevertheless is still relatively rich in carbon dioxide.

Some trace amounts of carbon dioxide are entrained in the condensing steam forming a 5.0-pH condensate that then can be used for cooling-tower makeup. Currently, after it passes through the final latent heat-recovery stage, the relatively dry exhaust heat, still rich in carbon dioxide, is directed into a recovery chamber and exits to the atmosphere.

But that will change. Soon, a distribution system will be built in which sidestream flows of condensate at selected volumes will be pulled from the recovery chamber and directed over the roof of the satellite chiller facility to a greenhouse sitting directly behind it. Rich in carbon dioxide, the condensate will be used to enrich plant growth through photosynthesis as part of the university’s future carbon-dioxide-enrichment research.

Eventually, the university will create a subtropical rain forest in a corner of the campus a few hundred feet from the fuel-cell plant and satellite chiller facility. A second side stream of condensate will be directed through a diffusion distribution system throughout the subtropical rain forest microclimate to enhance photosynthesis there. The fuel-cell water effluent will eventually be put to use to irrigate the rain forest.

Four or five plastic cooling towers, piped to remove exhaust heat from the new chillers, will be built within the rain forest to provide moisture to the plants. The chillers will also have an additional conventional cooling tower built directly adjacent to the satellite plant.

Robert Ryan, a faculty member in CSUN’s College of Engineering & Computer Science, recently reflected on a system that normally is consigned to plant engineers to rhapsodize over: “Having a state-of-the-art fuel-cell plant right here on campus is a unique research opportunity for mechanical and electrical engineering faculty, and an extraordinary opportunity for us to mentor our student engineers.”

Ryan is now studying the performance of the system used to recover thermal energy in the fuel-cell exhaust streams. His calculations indicate the efficiency of the combined heat and power plant will indeed exceed 80%.

California-based writer Lyn Corum specializes in energy topics.

DE - July/August 2007