Portland’s plan for DE payback offers a clear vision for carbon-dioxide reduction.
By David Engle
Seven years ago or so, the world was waking up to the challenge of global warming. At about the same time, the City of Portland, OR, was asking itself, “What do we do with all this sewage methane?”
Though not equally portentous or headline-stirring, both issues basically pertain to carbon dioxide. Thus, Portland—“acting locally while thinking globally”—set forth “broader sustainability goals” for itself, “using energy efficiency and renewable energy as two foundational planks for improving the area’s livability,” says Portland’s senior energy specialist David Tooze.
The two planks he’s talking about, effectively managed, can slash carbon dioxide and particulate emissions. More specifically they can help communities attain the goals set by the Kyoto Protocols, calling for curtailment of carbon-dioxide production by 7% of 1990 levels by 2012.
With this as a backdrop, Portland proceeded to explore its sewage-treatment biogas options, eventually deciding upon several, which are now in progress.
But perhaps more significantly, the city also came up with a formal “Local Action Plan for Global Warming,” a broader, integrated strategy for balancing greenhouse gases (GHGs) and air quality against long- and short-term energy needs. Produced in 2001, it could well serve as a template for other communities. Here’s a report on how one environmentally progressive city of 530,000 approached the energy-and-air tradeoffs, and how the resulting energy projects have fared.
Sustainable Development
Functional integration began by consolidating several of Portland’s city waste departments into one Office of Sustainable Development (OSD), with a mandate to propose and design projects “for waste reduction, recycling, energy efficiency, high-performance green buildings, and renewable energy,” says Tooze. Other areas under the OSD’s bailiwick cover transportation, restoring community vegetation, related policy research, and education.
Folding these into one “shop” arguably makes good sense: Cities often do solid waste and/or wastewater management; they operate landfills and treatment plants yielding biogas; they spend millions on electricity and heating when there’s opportunity to save; they worry about air quality; and they must approve or reject local power generation permits. So, there’s a synergy that calls for coordination.
In fact, a number of factors are prompting cities to shift from historic passivity to taking a proactive role on energy issues—a role reserved, until quite recently, for utilities and power commissions alone. Among the agents of change was the advent of “community aggregate power” policies (CAPs). This budding regulatory movement aims explicitly at giving communities greater choice over power generation. So far, California, Massachusetts, New Jersey, Ohio, and Rhode Island are setting the pace in allowing cities and towns to aggregate the electricity loads of homes, businesses, and the public sector—then to shop for power deals in energy markets.
Even in places where CAPs haven’t been enacted yet, there’s good logic in formalizing energy planning at the local level—for several reasons.
One is that energy and transmission shortfalls are looming or already occurring. Cities’ power needs, especially in rapidly growing areas, are steadily expanding but smacking into serious constraints. Primarily, urban land needed for new power plants and/or siting transmission lines is lacking. As John Kelly, who formerly handled distributed energy (DE) for the Gas Technology Institute, explains, a number of booming urban areas “are facing incredible challenges in terms of providing electricity on-peak.” The problem arises, he says, in that, although cities are more active and power-hungry during daytime, there’s no equivalent growth in baseload at night. Hence, a big, expensive plant will need to run only part time, making its electricity cost far more.
The best solution is DE, strategically sited downtown for peaking power. Cities and power customers need no longer defer the siting and resource selection matter entirely to utilities—which, not infrequently, have conflicting interests of their own.
Next as an impinging factor, there’s heightened community need for energy diversification, security, and reliability. During these uncertain times, city governments are expressing an increased desire to provide backup onsite power as a hedge against transmission interruptions, blackouts, brownouts, or natural disasters. As Ronda Mosley of the Public Technology Institute in Washington, DC, notes, “There’s is a definite trend among urban energy and environmental directors” to make energy security (preferred buzzterm: surety) a priority. “Distributed energy,” she adds, is viewed as “a huge component in the solution.”
Tooze notes as well that, within downtown areas, “A lot of the interest in distributed generation is coming from ... data centers, banks, hospitals, [and] public safety agencies that need very high levels of reliability of electric service.”
Another factor drawing planners into energy decision–making is that of DE’s value in spurring business development. A proactive, DE-friendly city can readily attract and support industry, helping to finesse hurdles by assisting with zoning ordinances, land-use permits, siting, and net-metering issues. Tooze recounts one example in which a downtown Portland office building installed a turbine cogenerator for backup power and waste heat for domestic hot water. The OSD helped the project obtain valuable tax credits, which made it economically viable, and provided other consultation.
Likewise, a city can partner with the gas company in promoting rather than obstructing DE (as is often the case when projects compete against electric utilities). Portland’s OSD collaborates with local gas utility NW Natural, fostering turbine generators through an organization called the Northwest Energy Efficiency Alliance.
One fruit of this work was the installation of a combined-heat-and-power (CHP) microturbine at Portland’s 1000 Market Street Building; this particular equipment sits beside a street-level viewing window, allowing passersby to see the quiet little generator at work, day or night. “They can literally get window access,” Tooze notes, and this has become a kind of real-time CHP showcase.
Portland’s OSD realized early on that as a public-sector adopter it could spur a broader interest in clean, renewable energy by investing in projects of its own, especially using cutting-edge technologies that need a head start. In so doing, the city also serves citizens’ expressed wishes to lower greenhouse gas emissions.
E=10 Years Until “Squared”
In addition to serving as renewable-energy role models, cities typically may be more inclined to wait patiently and for somewhat longer periods—in comparison with the private sector—to recoup investments on, say, solar DE resources. Also, city budgets can combine power-generation projects with energy conservation or green-building retrofits. The “packaging” and synergy make for a more justifiable and more dramatic return on capital invested (ROI).
In scrounging for funding, cities are also able to tap grant money and other funding sources not as readily available to for-profit businesses or requiring fewer strings. More projects are thereby enabled.
Finally, as projects eventually pay off, the city can reinvest in even more projects, almost without limit. The “energy conservation department” (by whatever name) effectively becomes self-funding and self-perpetuating.
In Portland’s case, a simple and very straightforward criterion was established for funding all energy efficiency and/or power generation, as Tooze explains. If a given proposal promises a payback in 10 years or less, “it’s considered a smart business decision,” and the energy policy mandates further consideration of it. Ten years for simple payback, he adds, “is a handy rule of thumb that everyone can easily understand,” and has become “our underlying goal ... by which a lot of our actions are directed.”
Besides ROI, project results are also measured in carbon-dioxide reduction; publicly accessible progress is reported online at www.sustainableportland.org
Using this 10-year-payback rule also means that proposed projects aren’t forced to compete for limited budget funds: If a project meets the criterion, it is really “paying for itself” in savings and thus is readily approved. The more projects that the OSD can identify and justify this way, the better. It’s simply a matter of going out and finding qualified prospects.
In this, Tooze says, “We’re opportunistic. ... We see an opportunity and the resources lining up. ... Then we charge on.”
Paybacks can come more quickly, of course, as utility rates have tended to rise faster than expected.
On the other hand, it’s not uncommon that a proposal falls below the threshold and is turned down: “We don’t move forward unless it makes financial sense,” Tooze says, adding that most projects also require subsidy funding to meet the payback goal.
Biogas-Powered Fuel Cell
This brings us back to the original topic, that of Portland’s biogas challenge. It’s an almost universal problem for municipal wastewater treatment plants of any size that methane occurs as a natural treatment byproduct. The “standard” solution is to use some as fuel to warm facility boilers and buildings, flaring the surplus. Portland followed suit, burning one-third for warmth, flaring a third, and also piping one-third on a contractual basis to a nearby roofing company, which used the raw methane for heating tar. This arrangement had gone on since the 1980s.
Of course, another common use for methane is to fuel an electricity generator, which Portland decided it wanted to do. “We were looking,” Tooze recalls, “for a responsible use of the gas,” which was coming forth in prodigious amounts, “and impacting the local airshed.” Hot flaring “does a pretty good job of burning impurities,” he adds, “but regulatory agencies are keenly aware of the discharge.”
Moreover, the real virtue of electric generation from biogas is that “in the regional grid picture, you’re displacing gas generation somewhere else. So there’s a net savings to the region” when the gas is converted to power instead of being flared. Tooze calculates that about 3,000 metric tons of carbon dioxide are avoided yearly this way.
Typically, the genset of choice is a reciprocating engine, but the desire to reduce regional carbon dioxide made the city amenable to experimenting with a much cleaner alternative. This laudable goal presented another hurdle, in that biogas is notoriously dirty and low in Btus. Portland’s consisted of about 60% methane, 38% carbon dioxide, and 2% nitrogen, along with nasty siloxane and sulfur. These pose a challenge to cutting-edge clean technologies.
After weighing various options, Portland opted to experiment with a 200-kW, methane-powered fuel cell. The ONSI Corp.’s 25C phosphoric-acid type (PAFC) already had been proving itself since 1997 at the Yonkers (NY) Waste Treatment Plant, where it was being powered by sewage methane. And one standout virtue for this new role was its negligible emissions.
Because PAFCs were quite cutting-edge at the time, Portland’s pilot demo received major help from the US Department of Defense ($200,000); from Portland General Electric and the Oregon Department of Energy ($200,000); and from an energy tax credit, for a total subsidy of $470,000.
Commissioning came around 2000, making it, Tooze notes, the first fuel cell actually owned by a US city.
Rated for an average life of about seven years or more (according to ONSI product literature), Portland’s PAFC actually lasted just short of this. In 2005—after the PAFC had yielded about 6 million kWh of power—a steam line broke, damaging interior electronics. Repair was not deemed cost-effective, so the cell was retired.
All things considered, though, the city thought it a success for having produced “a lot of electricity for us, all of it from renewable fuel, using waste biogas,” says Tooze. “And we learned a lot about the operation of the fuel cell. It wasn’t down that much of the time, and it produced a good chunk of power.”
Microturbines Get a Go
The OSD’s next power project came shortly after the PAFC’s launch, when the waste treatment plant operators realized that even more biogas was available and usable. After weighing whether to buy a second PAFC or go to another technology altogether, Portland opted for another newcomer, buying four 30-kW Capstone microturbines, which were commissioned in 2003.
As noted earlier, biogas is notoriously dirty, and the low Btus caused some difficulty. “Dealing with the siloxanes and sulfur dioxide and taking the moisture out are expensive steps needed in order to utilize low-quality gas” in microturbines, Tooze explains. “Treating the gas properly and delivering it at the correct pressures were critical for the turbines’ operation.”
Eventually, problems were solved by upgrading to four dedicated fuel compressors.
Despite the difficulties, the quasi-experimental challenge with what were then relatively new technology solutions seemed justified, Tooze says, because microturbines, when working properly, “can use a renewable waste fuel in a high-efficiency, clean-burning” power train.
After four years’ operation with them, “We’ve learned a whale of a lot,” he adds.
Thus, for the next upgrade—due in January 2008—the plant will be running with a much larger unit, a $1.4 million, 1.7-MW Jenbacher reciprocating engine, which is able to use more of the waste methane.
Project design and construction (by Brea, CA–based Western Energy Systems) will cost an estimated $5 million or so, with approximately $2 million additionally appropriated for contingencies.
In making the decision to revert to the more conventional solution, Tooze concedes that there is indeed a certain irony in that reciprocating engines were initially rejected as too polluting. These engines, however, have made dramatic strides, and the technology, he says, “has caught up with clean-burn features that meet the city’s goal for utilizing the resource but have a low impact on the local airshed.” So, he continues, “this engine in effect leapfrogged and has now become preferred for the next upgrade,” as well as being probably superior in a biogas recovery plant for straight-up reliability, cost per kilowatt-hour, power density, and overall emissions.
When commissioned in 2008, the Jenbacher will yield an estimated $500,000 of electricity a year, he says, “and pretty close to one average megawatt—which would be 8,760,000 kilowatt-hours per year.”
Summing up the decade’s three wastewater projects, Tooze observes that, although using three successive solutions is a bit unusual, “it’s all been sequential and all part of a larger plan to decide what was the best way to utilize the digester gas that we produce.” The shifting solutions reflected changes in capabilities of rapidly evolving technologies.
Solar PV, Wind Turbines, and Heat Pumps
Meanwhile, elsewhere in Portland, several other plants have been approved and commissioned.
Dating from the early 1990s, Portland’s first onsite power project, a 150-kW micro-hydro in-line generator, is still in operation, powered by water descending from an underground hilltop reservoir.
In December 2004, under the 10-year-payback benchmark, two 6-kW solar photovoltaic (PV) systems were activated at Portland fire stations. Although PV carries a high initial price tag, the city was able to secure outside funding to make it qualify, intending it as “a workhorse as far as reliability,” says Tooze.
In June 2005, a 10-kW wind-turbine demonstration project was commissioned at a rare in-town location (the city equipment yard) that gets only marginal winds; nevertheless, the project presented, says Tooze, “an opportunity to showcase wind-turbine technology in an industrial zone.” It’s literally a high-profile statement about commitment to clean renewables. The siting gives city residents an easy way to observe a novel technology, which otherwise they would find only in the boondocks. The turbine’s resulting power runs a leaf-recycling composter—“a nice synergy” that should draw appreciative visitors, Tooze explains.
A one-year pilot program called Solar Now! will soon be under way, “promoting domestic water heating for businesses and residences, using both solar hot water and electric power,” Tooze continues. The demo should spur homeowner participation and will assist would-be adopters in various ways: directing them to technical information resources and federal and state tax credit opportunities; facilitating qualifying for cash financing from the Energy Trust of Oregon (a nonprofit custodian of monies for energy conservation and renewables); and referring them to qualified solar installers.
And planned for 2008, a 48-kW rooftop PV system will power the East Community Center Pool and Recreation Center year-round. Facility cost is estimated at $8 million. To warm the swimming pool, high-efficiency dehumidifying heat pumps will extract moist room heat, condense it, and recycle it back into the pool, neatly solving the room humidity problem as well. Sporting these and other advanced green features, the center is expected to receive a Leadership in Energy and Environmental Design gold or platinum designation. To help pay the rooftop solar PV portion, Portland is arranging a multiparty collaboration between a leasing company, the electric utility, and the Energy Trust of Oregon to devise a grant-and-leasing package maximizing solar tax credits.
Just over the horizon, possibly in 2009, Portland is contemplating the large-scale purchase of wind power from market-leader PPM Energy, operating a turbine farm in eastern Oregon.
Tooze sums up by noting that all of these projects are showcases to some degree and “are integrated in an economic development strategy to attract clean energy and energy-efficient businesses to the Portland metro area ... sustainable businesses that we target for development and growth. It all fits together.”
Urban distributed generation in the mix is often especially desirable, Tooze adds, because “it’s using local energy resources and providing reliability to the electric system, to the grid, and in some cases it’s producing additional measures of power reliability for end users. Those are community needs, and the better the planner can accommodate those, the stronger the community is going to be.”
La Mesa, CA-based writer David Engle specializes in construction-related topics.
DE - May/June 2007
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