Water is the key constraint to economic development, not electricity, and will strongly affect the overall demand for electricity, EPRI concluded.

Water and wastewater treatment facilities are among the largest and most energy-intensive systems owned and operated by local governments, accounting for as much as 56% of municipal energy usage in California, according to the California Energy Commission. In a 2002 study of water and sustainability, EPRI calculated that pumping treated water to a distribution system accounts for 80% of electricity consumption in treatment facilities.

Minimizing energy use in municipal water and wastewater services can potentially yield substantial energy savings benefiting agencies and ratepayers as well as reducing the consumption of energy resources. The CEC believes the potential is large. Out of the 242 sewage wastewater treatment plants that serve California cities, just 10 generate about 38 MW using biogas. Another 12 utilize biogas to produce hot water to heat digesters. The CEC would like to see another 36 MW developed at the remaining 220 treatment plants.

A few municipal water and wastewater agencies have already successfully installed microturbines and fuel cells to generate electricity onsite and comply with air quality regulations. Some also have heat recovery systems to heat anaerobic digesters. Going one step further, several water agencies in California and Nevada have installed solar photovoltaic systems either to run pumps or to feed the power into their electrical systems.

Previewed here are several of the higher profile installations in each of three categories: solar, fuel cells, and microturbines. These new technologies are being installed primarily on the West Coast and in New York state. In most other states, low-cost energy and fewer regulations do not peak enough interest in new technologies. Where there are financial incentives, there is
interest.

For example, the city of Albert Lea’s wastewater treatment plant in Minnesota agreed to install four 30-kW Capstone MicroTurbines when the utility, Alliant Energy-Interstate Power and Light, agreed to pay for two. The utility sought the project because it was asked by the Minnesota Department of Commerce to fulfill requirements for a state conservation improvement program. Alliant Energy will receive energy credits from the treatment plant for the installation.

This is not an atypical arrangement. West Coast municipal utilities, in particular, are relying on federal grants and state incentives in most cases to pay for the very high capital costs of the new technologies.

Fuel Cell Plants
The wastewater treatment division of King County, WA,  has been one of the leaders in the wastewater industry with its innovative energy projects. In 1985 it installed four reciprocating engines at its West Point Treatment Plant to operate on digester gas. The engines continue to produce 1 MW and run four effluent pumps. Waste heat is exported to the digesters to facilitate the anaerobic process and to heat office spaces. Plans are to replace the engines with more efficient models in the near future.

The Wastewater Treatment Division began its partnership with the Danbury, CT-based FuelCell Energy in 2000 when the company was selected to design and install a molten carbonate 1-MW fuel cell plant as a two-year demonstration project at the southern wastewater treatment plant in Renton, WA. Fabrication of the fuel cell stack began in late 2001. FuelCell Energy began constructing the plant in early 2003; operations commenced in 2004. The goal was to determine if the fuel cell plant would operate on digester gas and produce power at the efficiencies the manufacturer claimed.

FuelCell Energy calls the 1-MW plant the world’s largest demonstration of a single-unit fuel cell power plant. It has successfully operated for two years on digester gas. The electricity it produces goes into the wastewater plant’s electrical substation. Its heat recovery unit is attached to a system that produces steam for the digester heating system. The plant may be upgraded to a 1.5-MW system if King County decides to keep the fuel cell at the end of the evaluation period later this year.

Performance data as of the spring of 2006 show the fuel cell plant’s efficiency varying between 43% and 47%. With heat recovery efficiency increases to 65%. Expectations were that efficiency would be at 49% and 72% with heat recovery. It is producing 1 MW, with 90% availability when expectations were that its availability would be 80%. NOx emissions were expected to be less than 2 ppm, and actually have been less than or equal to 0.2 ppm. Carbon monoxide emissions exceeded the predicted level of 10 ppm or less: they have been equal to or less than 13 ppm.

The $23.9 million project was paid for with a combination of federal, King County, and private funding. The US Environmental Protection Agency and Congress contributed $9.5 million. FuelCell Energy put up $11.4 million, and King County paid $3 million.

Early conclusions are that the efficiency of fuel cell technology continues to improve, that the quality and quantity of digester gas are the key parameters for consistent power generation capability, and that fuel cell technology is a viable, clean, sustainable power generation alternative.

The southern plant also has two gas-fired solar turbines, each 3.5 MW, and one 1-MW steam turbine, manufactured by TGM Turbinas, a Brazilian company, configured as a combined-cycle unit that could generate as much as 8 MW under emergencies when utility power fails to keep the wastewater treatment plant operating. Under normal conditions this system operates during peak periods to reduce demand charges.

The Fuel Cell Pioneer
IN 1999, the Los Angeles Department of Water and Power first installed a 200-kW phosphoric-acid fuel cell, manufactured by United Technologies Corp., of Hartford, CT, at a switching station in downtown Los Angeles. Since then it has purchased two precommercial 250-kW molten carbonate fuel cell plants manufactured by FuelCell Energy. The first, costing $ 3 million with $250,000 coming from the US Department of Energy, was installed at its headquarters in 2003, and sends the electricity it generates into the city’s grid. FuelCell Energy completed 18 months of field trials on that unit.

Later in 2003, LADWP installed its second 250-kW fuel cell at the Terminal Island Waste Treatment Center operated by the city’s department of sanitation. Costing $2.3 million, it received $250,000 in grant funding from DOE.

Kjell Ostensen, LADWP’s fuel cell program manager, says the department originally intended that the fuel cell plant would run on digester gas, but there were technical challenges to the biogas cleanup system. FuelCell Energy was already working on the problem at the King County, Washington installation and at the installation of a 250-kW unit in Fukuoka, Japan. Ostensen said the county decided to wait, operating the system at Terminal Island on natural gas.

Once FuelCell Energy perfected its biogas cleanup system, LADWP’s fuel cell plant was outdated, and retrofitting the system would be difficult. The decision was then made to not retrofit the gas cleanup system, and it was shut down after operating for one year. More important, if a gas cleanup system were installed, the fuel cell stack, which has an operating life of three years, would be ready for replacement.

Instead, Ostensen says the department will buy four new fuel cells with the gas cleanup system to replace the old plant, which will be used for replacement parts. The new 1-MW plant will also have heat recovery capability which the current fuel cell plant does not have.

Robert Castro, LADWP’s manager of distributed generation, says that, based on the department’s experience, the phosphoric acid fuel cells have proven to be more durable but not as efficient as the molten carbonate direct fuel cells. The latter have more potential because of their higher efficiencies, he says.

FuelCell Energy has also sold its fuel cells to the Los Angeles County Sanitation Districts for its Palmdale wastewater plant, and the El Estero Wastewater Treatment Plant in Santa Barbara, CA.

Fuel Cells Clean the Air
The Santa Barbara installation is unique in that the city signed a long-term power purchase agreement with a joint venture formed by FuelCell Energy and Alliance Power. The power generated by the two 250-kW fuel cell power plants installed at the wastewater treatment plant and fueled by digester gas, will be sold to the city. It is the first such deal for FuelCell Energy. The power plant will supply heat as well to the boilers supplying hot water to the digesters.

Rebecca Bjork, wastewater system manager said the fuel cell plant took one year to construct, largely due to getting permit approvals. It has been operating since January 2005. Power is fed directly to the treatment plant. Bjork says the fuel cell plant was sized around the amount of digester gas produced by the plant. She says the gas cleanup system is working fine.

Electrical bills were reduced by $12,000 the first year, Bjork says. She expects annual savings to reach $20,000 in the future. These savings are very small, given that annual electrical bills are $500,000. The real benefit, she says, is that it reduces NOx and SOx emissions and particulate matter. Another advantage is that FuelCell Energy is operating and maintaining the system as part of the agreement with the joint venture. Alliance Power provided the turnkey construction services.

The project received $2.25 million in incentive funding from the CPUC’s self-generation incentive program. Furthermore, because the technology has been designated as ultra-clean, the treatment plant is exempt from SCE’s standby charges.

Fuel Cell Plants in New York
The New York Power Authority has nine 200-kW phosphoric acid fuel cell plants at five water and wastewater treatment plants in New York, all supplied by UTC Power, a subsidiary of United Technologies Corp. The first was installed at the Westchester joint wastewater treatment facility in Yonkers in 1997. The remaining fuel cell plants were installed between 2003 and 2005 at the Flushing Avenue and Flatlands Ave. Wastewater Treatment Plants in Brooklyn (each have two fuel cells), Oakwood Beach wastewater treatment plant, Staten Island (one fuel cell) and at Hunts Point wastewater treatment plant in the Bronx (3 fuel cells).

The fuel cell plants operate 24 hours per day, seven days per week, and run parallel to the grid. They contribute less than 5% of each facility’s electrical load, according to Guy Sliker, a staffer at NYPA. All are fueled by digester gas, and the waste heat generated by the fuel cells is used to support the anaerobic digester process.

The cost of the fuel cells was approximately $13 million. DOE provided $1.5 million in the form of a grant, and the New York State Energy Research and Development Authority provided $1 million. The remaining amount was financed by NYPA.

Sliker said the fuel cells are operating well. The primary operational challenge is getting a consistent supply of digester gas. When it is not available, the fuel cells automatically switch to natural gas until the digester gas supply returns, he explained.

NYPA also has four additional 200-kW fuel cell plants operating at the Central Park police precinct, where the plant is grid independent, the North Central Box Hospital, the New York City Aquarium, and at the State University of New York-Syracuse campus. This last 250-kW fuel cell plant is molten carbonate manufactured by FuelCell Energy.

NYPA has also invested in other technologies. In 1996 it installed a 100-kW photovoltaic solar system on the roof of the Yonkers plant. It operates in parallel with the grid. NYPA has also installed two 30-kW Capstone MicroTurbines at the Town of Lewiston Water Pollution Control Center in 2001. They operate on digester gas, providing about one-third of the electricity needed to run the plant and saving Lewiston about $40,000 on its electric bills annually.

The MicroTurbines cost $225,000. NYPA provided $125,000 for purchase, delivery, and installation of the units, plus design and engineering services related to demolition of the old diesel generator the fuel cells replaced. An additional $100,000 came from the state’s Petroleum Overcharge Restitution fund.

Solar Systems Offer Security
The CEC has stated that solar power development at water sector facilities appears to have significant potential in the next 10 years. Furthermore, these facilities will be able to take advantage of incentives under the state’s renewable portfolio standard and its major solar initiative.

In April 2005, the Association of California Water Agencies, PowerLight Corp., and WorldWater & Power Corp. signed a five year agreement to establish a partnership program that will encourage water agencies to install solar systems to reduce their energy costs.

Since then, the Elsinore Valley Municipal Water District in Southern California installed a 765-kW solar system, and the Sonoma County Water Agency in Northern California installed a 523-kW system. The city of San Francisco installed a 255-kW solar system built by PowerLight that began operating in November 2005 at its southeastern wastewater treatment plant.

Later in 2006, the West Basin Water Recycling Plant in El Segundo just south of Los Angeles International Airport will install three solar arrays totaling 590 kW. In June, the city council of Thousand Oaks approved a power purchase agreement with a subsidiary of PowerLight which will install, own and maintain a solar system. The city has agreed to buy more than one million kWh annually at a cost of $170,157. This translates into a rate of 16.5 cents/kWh.

Other districts did not need ACWA’s encouragement. Earlier, in 2005, the Semitropic Water Storage District in Kern County installed a 1-MW system.

The Idyllwild Water District installed a 42-kW solar PV system in early 2006 and dedicated it in May. It serves a system with a 50-HP load that pumps water from six wells to an aeration plant to remove iron and manganese, then moves it to a filtration plant. From there water moves to storage.

General manager Terry Lyons says the district wanted to operate independently of Southern California Edison to avoid power outages. Nearby forest land owned by SCE contains about 6,000 pine trees killed by the bark beetle and if winds reach 40 miles per hour, SCE shuts off power in the area in the event that any trees are blown over. Once all the trees are removed, power outages will be rare, Lyons says. “But we decided to be proactive.”

The district’s traditional backup power system—diesel generators—is expected to eventually have its permit limited to operating three hours per day by the local air quality district, said Lyons. However, the solar system operates between sunrise and sunset daily. If demand requires that the system operate beyond its solar window and water must be drawn from the other wells not connected to the solar system, utility power will be used, Lyon explains.

Pennington, NJ-based WorldWater & Power Corp., which designed and installed the system, had created a patented variable frequency drive for its solar systems and installed it, along with an anti-islander inverter, on Idyllwild’s solar system, which is net metered. The inverter allows the solar system to continue operating after utility power is lost while the drive brings pumps slowly back on line. Without both, the solar system would be dependent on grid power to restart the pumps.

Lyon won over the district’s board of directors because a majority of its members had technical backgrounds, including an aerospace engineer and an ammunition specialist who spent six months asking questions. “They had enough expertise to ask the right questions,” Lyon says. And WorldWater flew in engineers to provide the answers. To top it off, a key vote was provided by a director who already has a solar system at his home.

The real advantage of the system is it reduces the district’s peak demand charges. “We’ve cut electricity bills 85%,” Lyons said. The solar system cost $309,000 but a $155,000 California rebate, awarded by SCE, cut the price in half, giving the district a 10.8-year payback. “In 11 years, we won’t be paying much; it’s like free energy,” Lyon says. Revenues are increased as WorldWater buys renewable energy credits from the district at 10 cents per kWh for the next seven years.

Economizing At The Reservoirs
The Las Vegas Valley Water District has grander plans to install a 3.1-MW solar photovoltaic system at several of its reservoirs. The water district serves Las Vegas and portions of Clark County. In order to supply its one million customers every day it has to move water uphill, making it one of the largest power users in southern Nevada.

The project was proposed and competitively selected by Nevada Power as part of its 2003 request for renewable energy proposals. The district’s board of directors approved the $22.6 million contract with PowerLight Corp. in October 2004, and the Public Utilities Commission of Nevada approved the project in February 2005.

As part of the agreement with Nevada Power, the water district will sell its renewable energy credits to the utility for 0.795 cents per kWh times a 2.4 multiplier. This is an element of the Nevada Legislature’s 2001 renewable energy legislation, designed to make photovoltaic systems more cost effective.

Each of the water district’s six reservoir pumping stations will have a photovoltaic system that tracks the sun. The generated electricity will run the stations’ pumps. The first installation completed by PowerLight was an 821-kW ground-mounted system christened in early June at the Ronzone reservoir and pumping station. The water district expects to have the remaining five systems installed by the end of 2006, according to Bronson Mack, a spokesman for the water district.

A 330 kW system is currently being roof-mounted on the Grand Canyon reservoir. Construction has also been slated for the 353-kW system at the Fort Apache Reservoir, the 537-kW system at Spring Mountain-Durango Reservoir and the 555-kW system at the Luce Reservoir. These will also be roof-mounted.

Also, a 409-kW system will be installed at the Springs Preserve reservoir and pumping station. The site is also the historical home of Las Vegas’s founding springs and it is being developed into a cultural resource center featuring trails, exhibits, and gardens focused on sustainable living in a desert community.

The solar system’s structure will provide shaded parking for up to 200 cars. The power it generates will also serve air conditioning and security equipment for the buildings being constructed to house the cultural resource center and a Nevada state historical exhibit.

Mack says power costs are currently managed by running the pumps at night when utility rates are at their lowest. Once all the solar systems are operational, plant operators plan to run the reservoir pumps during the day.

When the system is generating excess power, it will be fed into the grid. Nevertheless, the systems will help to stabilize the grid in their immediate areas, providing benefits to the surrounding residential communities.

Mack said the entire $22.6 million is being funded through water district rates, without increasing their rates. Deferred energy costs, energy credits and net metering will assure that the system will pay for itself during its 30-year life expectancy, he says.

Microturbines Are Natural Fit
The Inland Empire Utilities Agency owns and operates water recycling facilities in southern California and serves about 700,000 people in a 242-square-mile area that includes the cities of Fontana, Rancho Cucamonga, Ontario, and Chino. It has become extremely energy conscious to the point of building its new office complex to a Leadership in Energy and Environmental Design (LEED) “Platinum” standard. A solar photovoltaic system was built on one of those office buildings.

IEUA generates 10 MW with microturbines and reciprocating engines mostly burning biogas at five treatment plants. It is also trying out experimental technologies—a 60-kW Stirling engine and a 3-MW bottoming cycle organic pentone generator.

Nineteen Capstone MicroTurbines, 30 kW each, were installed within the last five years at four of its regional plants. Six at one plant operate on natural gas for peaking power. The remaining MicroTurbines at the other plants provide heat to the digesters, as well as generate electricity.

The two experimental generators have been installed at regional plant No. 5, where there are also four Capstones. The goal is to increase digester gas generation to 4 MW there. A new organic Rankine cycle (ORC) 3-MW generating station is under construction and will run on digester or manure gas. The ORC generator uses a bottoming cycle organic pentane process. Pentane is traditionally used as the internal liquid in refrigeration. In this case, exhaust heat from generators is used in a reverse absorption process to generate electricity.

A 60-kW Stirling engine has just been installed by STM Power Inc., of Ann Arbor, MI. An external combustion engine, it will run on manure and digester gas once the company works out the bugs for operating on biogas. STM Power believes the Stirling engine, operating in a combined heat and power mode, can produce electricity and heat more economically than other distributed generation technologies. IEUA will invite California Polytechnic State University, located nearby, and other researchers to test the engine’s performance. The engine costs about $65,000.

Not intending to ignore any technology, IEUA has submitted applications to SCE and Southern California Gas Co. for incentives to fund two fuel cells, one each from FuelCell Energy and UTC Power to be installed at Regional Plant No. 1.

Chief engineer Neil Clifton says the agency has been following the installations at Kings County, Washington and at Santa Barbara.

The current generation provides about one-third of IEUA’s electrical needs. Its bills would be $6 million to $7 million annually if it had no onsite generation, according to Clifton. He says the goal is to produce all of IEUA’s power needs with digester gas.

To reach this goal, the agency has started up a new 300-ton-per-day digester, and another is being built nearby. It is expanding the feedstock for the digesters to increase production of biogas that will power future microturbines and engines. The new digester is handling manure transported from cattle feed lots and IEUA wants to increase the amount of food waste it collects. Manufacturers will pay the agency to take waste such as cheese whey, lactose, salad dressing, ice cream, and renderings from slaughter houses. Clifton says food waste currently makes up 5% of digester content. He wants to see it increased to 20%.

The final word on microturbines goes to the plant superintendent of the city of Albert Lea Wastewater Treatment Plant. Rick Ashling says microturbine applications in wastewater treatment plants are good because of the similarities in maintaining both. Operators adapt easily to maintaining microturbines, he says.

California-based writer LYN CORUM specializes in energy topics.

DE - November/December 2006