Daily Camera (Boulder CO)
Modelers: Boulder municipal utility feasible
Volunteers will present findings
By Laura Snider Camera Staff Writer Posted: 06/27/2011
A team of 30 skilled volunteers working over six months has developed an independent model of whether it's feasible for the city of Boulder to form a municipal utility and reduce its carbon emissions for a cost that's similar to what customers now pay Xcel Energy.
The answer is yes, say the volunteers, who will present their findings at a public meeting Wednesday night.
"We can cut our current emissions by 50 percent and be comparable to Xcel and be more stable (in terms of rates) over time," said Sam Weaver, co-founder of a power conversion equipment company and one of the volunteer modelers.
The city of Boulder has also hired its own consultants to create a feasibility model that is separate from the volunteer effort.
The group used a modeling tool known as HOMER, developed at the National Renewable Energy Laboratory, as the backbone of the technical model. HOMER was designed to help users figure out how much alternative energy -- including wind and solar -- can be reliably integrated into an energy system.
The group also created a financial model under the leadership of Frank Selto, a professor at the University of Colorado's Leeds School of Business.
As a base case, the modelers assumed that the only renewable energy used in a future Boulder municipal utility would be the renewable energy generation that already exists locally, which includes mostly rooftop solar arrays and a little hydropower. The modelers also assumed that the rest of Boulder's energy demand would be met by burning natural gas.
The result was that Boulder could reduce its emissions by 50 percent -- since burning natural gas releases less carbon than burning coal -- for a slightly lower rate than Xcel’s. For example, a residential customer who uses 520 kilowatt-hours a month would pay $61.07 under Xcel’s rates but $58.27 to a Boulder municipal utility. The model assumes that Boulder would spend $300 million in startup costs.
The modelers also ran a worst-case scenario that assumed startup costs would double to $600 million. The result was that the same residential customer would pay $68.80 a month.
The city of Boulder’s own models assume that startup costs would be slightly less than $300 million. But Xcel says the city is leaving out as much as $336 million in "stranded costs" from its analysis.
The volunteer modelers also ran a scenario with a mix of renewable energy that -- coupled with the natural gas -- would decrease carbon emissions by 68 percent. In that scenario, a residential customer who uses 520 kilowatt-hours in a month would pay a bill of $65.29, or about $4 a month more than what that person would owe Xcel.
In general, the volunteers say that their model is built on a series of conservative assumptions, which include having more reserve capacity -- the amount of power that can be immediately tapped in an emergency -- than is required by federal regulation.
The model's assumptions have also been endlessly challenged and vetted by the members of the group over the months, said volunteer Alison Burchell.
"The man-hours that have gone into this is phenomenal," she said.
Tom Asprey, who led the technical modeling, said as a resident of Boulder and as an advocate of renewable energy, he wants to feel as confident as possible that the model he helped create is robust.
"Putting something out there that is going to flop does not help anyone," said Asprey, an engineer who has been spending 40 hours a week or more refining the model.
Still, at least one person is concerned about the applicability of HOMER to model a system as large and intricate as Boulder's. Rebecca Johnson, who recently earned a Ph.D. in energy policy from CU, said that HOMER, which only measures supply and demand on an hourly basis, does not have the resolution necessary to really evaluate renewable energy, which can fluctuate in intervals of minutes if a cloud passes over or if the wind stops blowing.
"Models that evaluate renewables are at a minimum of 15-minute increments," she said.
Johnson also has concerns that Boulder is too small of an area to effectively integrate large portions of renewables. On large systems, the fluctuations are easier to absorb since the sun is usually shining somewhere in the service area, for example.
But Weaver said his group’s HOMER model is adequate for its intended use, which is to see whether creation of a municipal utility can be done with rate parity.
"This is not a design tool," he said. "This is a feasibility study tool. Hourly is just fine for estimating costs."
Clarification: Peter Lilienthal, the original developer of the HOMER model and now the chief executive officer of HOMER Energy, says that HOMER's primary purpose is to evaluate renewable energy. The HOMER model can model demand and supply on a minute-by-minute basis if such data is available.
Contact Camera Staff Writer at 303-473-1327 or email@example.com.
If you go
What: A volunteer group of Boulder residents who have worked for six months to model the possible ways the city could reduce its carbon emissions -- and the associated costs -- if it forms a municipal utility will present their findings. The meeting is sponsored by Renewables Yes and Citizens for Boulder's Energy Future.
When: The presentation will run from 7 to 8:45 p.m. Wednesday. Refreshments will be served beginning at 6:30 p.m.
Where: Meadows Branch Library, 4800 Baseline Road in Boulder, behind Safeway
More information: renewablesyes.org