Wind Power in Bowling Green

Wind Power in Bowling Green

Bowling Green Municipal Electric Windpower Tour

November 9, 2007

J. Russell

On November 9, 2007, Members of the Southeast Michigan Association of Energy Engineers (AEE) visited the City of Bowling Green, Ohio, for a tour of the city’s 7.2-MW wind turbine installations. Overall, the city has had a very positive experience with the turbines, and is considering plans for additional wind capacity.

Background

Bowling Green’s Public Utilities Department manages city-owned electric generation, electric distribution, water treatment, water distribution, wastewater collection, and wastewater treatment systems. Kevin Maynard, Utilities Director, oversees these operations. In addition to a site visit, Maynard was able to give us some background on the installation, operation, and financial aspects of the wind project.

The Electric Division of the department has budget of almost $40 million dollars/year, for a total usage of about 550 million kWh/year. This division provides electricity to a community of about 30,000 residents (including about 18,000 University students at Bowling GreenStateUniversity). The average electrical system load is about 60-65MW, and peak demand in the summer is over 100MW.

The City of Bowling Green is a member of American Municipal Power-Ohio (AMP-Ohio), a consortium of 86 municipal utilities in Ohio. AMP-Ohio coordinates, negotiates, and develops power-supply options and interconnection agreements on behalf of member communities. AMP-Ohio is also involved in design and maintenance projects for member electric systems.

Project Planning

This wind power project was pushed by the former Utilities Director for Bowling Green, Daryl Stockburger (now retired). Stockburger oversaw much of the wind testing, site selection, and project planning that was required to move the project to completion.

One of the key motivating factors for pursuing a wind project was the need for risk management in Bowling Green’s utility system, especially with regards to prices of fuel and purchased power.

“We have tried to, as an organization, diversify our power supply portfolio, to try to manage our risk, primarily,” said Maynard. “We have some long-term contracts, we have some short-term contracts, we have some investments in different facilities, including a run-of-the-river hydroelectric plant on the Ohio River, the wind turbines, some peaking generation—diesel and combustion turbines—and also a long-term contract for landfill gas-to-energy.”

In the late 1990’s wind power maps did not indicate Bowling Green as a feasible site for wind turbines. Local residents, however, knew that wind gusts in the open fields outside the city could be both frequent and intense. “It seemed that [Bowling Green’s typical wind conditions] ought to be able to support a wind project, but we didn’t have any data to back it up,” Maynard said.

In 1999, the city put up a 50-meter-high meteorological test tower to record one year of wind speed and direction data. This test indicated positive results for a potential wind project, with average wind speeds around 13 mph, and the project proceeded as a joint venture between the City of Bowling Green, and other AMP-Ohio members.

“We all have an ownership interest [in the joint venture],” Maynard said. “Bowling Green owns 4,100 kW of the 7,200 kW [total capacity], which equates to just under 57% ownership interest. So we get 57% of the kWh, whatever is being generated every hour, it just displaces other energy sources.”

Site Selection

The city chose the local Wood County Landfill property to build the turbines, and the joint venture pays an annual lease payment to the County. The sites were not in active use for the landfill’s waste disposal, but were (and are still) being leased for farming. Each tower has a base diameter of about 14 feet, so the footprint is minimal. The project also reserves a gravel area about 50 feet in diameter around the base of each turbine, as well as a two-track access road, to provide access/parking for maintenance.

Installation-First Phase

The first project was installed in 2003, and consisted of two 1.8-MW Vestas V80 turbines (see Appendix A). The towers are 78 meters (257 feet) high at the rotor hub. Each blade is about 130 feet long, for a total tip height at top-dead-center of about 387 feet. According to Maynard, the wind turbine farm was the first—and is still the only—utility-scale wind power project in the state of Ohio. A smaller, 225-kW refurbished wind turbine was recently installed at the Great LakesScienceCenter in Cleveland.

The turbines were installed under a turn-key contract by Vestas, the manufacturer.

Maynard also commented how quickly the wind turbines were field erected. “As long as you can get these things, you can install them in a couple of months,” Maynard said.

Installation-Second Phase

In 2004, two more 1.8-MW Vestas V80 Turbines were installed, bringing the total capacity of the city’s wind generators to 7.2 MW.

Project Financing

Since Bowling Green is a municipal utility, they were able to get tax-exempt financing for just under $10 million for the four units. The financing term is 15 years. The joint venture pays about $400K/year in variable O&M costs, including about $200K/year in depreciation expense. Excluding depreciation, the project spends about $200K/year of actual O&M costs, which includes a service contract with Vestas, AMP-Ohio maintenance and monitoring services, and lease payments to the Wood County Commissioners (for using land fill property--$1,000/unit/year).

Bowling Green sells green tags to Green Mountain Energy for producing renewable power. Green Mountain Energy serves as a broker for electrical customers that wish to help fund renewable energy programs.

“For everything we can generate, we’re selling those tags, and helping keep our costs lower,” said Maynard. “If you were to sell them today, you’d get about 1.6 cents/kWh, we’re selling them for 3.3 cents/kWh under a five-year contract”

According to Maynard, selling Green Tags to GreenMountain energy more than offsets all of the variable O&M costs, which leaves just the debt service costs to be paid for by the utility. This year, they happen to have money left over from the construction fund that they used to pay for the debt service costs.

“All of our energy this year was ‘free’,” joked Maynard.

Current Performance

The project currently generates about 7.5 to 8 million kWh every year, equivalent to roughly 1.5% of the system’s total energy needs for a year. Output in 2006 so far has been about 16% greater than last year.

“Part of that may be just the variance in the wind resource, but I think part of it is, whenever you put in a new generation source or a new line in industry, you learn how it operates, and you get more efficient in running it over time, and I think that’s the case here,” Maynard observed. “As our staff, and the AMP-Ohio staff, have learned more about the nuances of the turbines, they are able to get more production out of them,” and have reduced maintenance downtime and false trips, according to Maynard.

The turbine operators have found that, on a day-to-day basis, production is usually highest around dusk. The turbines’ peak production months are November, December, and January, while July and August are typically the lowest production months.

The turbines turn on and off automatically according to wind speed. Variable-pitch blades and an internal gear box maintain stable generating conditions. The rotors start spinning at wind speeds of about 6 mph. The units start generating at about 9 mph, reach maximum output at around 31 mph, and they trip on high wind speed at about 56 mph. During a trip or maintenance outage, the variable-pitch blades rotate parallel with the wind, and an internal brake anchors the rotor. Each tower is built to withstand a 130-mph wind.

Electrical Grid Interconnection

The interconnection between Bowling Green’s power system and the First Energy Transmission systems is monitored by AMP-Ohio. AMP-Ohio makes the arrangements, through MISO, to deliver power to Bowling Green. AMP-Ohio’s 24-hr energy control center in Columbus, Ohio can monitor the output of the turbines, as well as the equipment performance and status indicators, over the internet by means of virtual private network (VPN)

“I think being able to diagnose what the issue is more quickly, and then determining whether they can simply restart the units, or if they have to send someone out to take a look at them, has resulted in increased production as well,” Maynard said of the advantages of 24-hr VPN monitoring by AMP-Ohio.

Maynard explains AMP-Ohio’s system operations as follows: “You can’t predict how much the wind is going to be blowing at any particular time, so [the wind turbines are] not dispatchable in the way that a diesel or a combustion turbine are, or going out and buying [power] would be… We want to take all of [the windpower] that we can, because every kWh that it’s generating is something that were not buying from another resource…Whatever the output is, it’s really just backing down the Bowling Green load to the MISO system. Amp-Ohio has to take a look at that, see what kWh are delivered hour-by-hour, and reconcile that with the power supply that’s being brought to Bowling Green, as well as distributing those kWh to the other nine communities based on their ownership interest.”

Upon startup, the generators automatically synchronize with an existing sine wave on the Bowling Green grid. Therefore, the wind turbines could not be blackstarted by themselves. During a system outage, local dispatchable power sources would have to be brought on-line before the turbines could be re-started.

The turbine nacelles have built-in breakers and step-up transformers that bring the output power up to 12,470 Volts to match the transmission in the area. A single cable carries the output of each generator down the tower, underground, and up to a connection on a nearby transmission pole (see Appendix B, Fig. B.5). According to Maynard, no other major interconnection equipment is necessary.

Maintenance

Maynard says that maintenance has been very minor, due to the relative simplicity of the turbine-generator. Minor maintenance and troubleshooting is performed by AMP-Ohio service representatives that are based nearby. The city has also purchased a 5-year service agreement through Vestas, which covers periodic preventative maintenance, major overhauls, etc. for $17,500/year/turbine. Maynard is pleased with Vestas’ response to unforeseen maintenance issues, and estimates that they are typically onsite within 1 to 2 days at most.

Overcoming Challenges

As stated above, public response has been extremely positive. Regardless, the following are a few of the typical installation/operation challenges for wind power projects, and Bowling Green’s relevant experience:

1. Noise. The sites were selected in an open, rural, area, to minimize potential noise impact. According to Maynard, the city has received no noise complaints from local residents. While standing at the base of the turbines during operation, the author found the noise from the blades was not much greater than normal white background noise on a windy day. Normal conversations are easily audible at the base of, and inside of, the towers during operation.
2. Impact on Bird/Bat Populations. A biotic assessment was required for project approval. This assessment determined that there were no major bird/bat migratory paths in the vicinity of the towers. To date, the city has found no evidence of significant bird or bat kills. Maynard has not seen evidence of any bird kills, and estimates that less than 10 dead common brown bats have been found near the towers in the last year.
3. Impact on Air Traffic. The project was required to receive FAA approval prior to construction. The FAA’s study indicated no interference with local air traffic.
4. Shadow Flicker. No complaints have been registered involving shadow flicker, mainly because of the isolated location of the towers.
5. Icing/ice-throwing. Icing has not been a problem, and the open-field site would minimize any chances of ice-throwing problems. No heat trace has been installed on the blades.
6. Lightning Strikes. One of the towers received minor lightning damage last year, butVestas repaired the damage under their service contract.

Managing Costs and Environmental Risk

As mentioned above, Bowling Green is looking to renewable power as way to manage financial risk from buying fuel and/or wheeled power from other generators. However, there is another aspect of their risk management strategy.

“From an environmental risk standpoint, I think [windpower] makes a lot of sense, because we don’t know what we’re going to see with greenhouse gas controls, carbon dioxide sequestration, and…frankly, it scares us,” Maynard said.

“The question is, what’s [GHG management] going to cost, and nobody knows at this point. So when you take a look at [wind power], I know what it’s going to cost, and I don’t think it’s going to change much. [The cost] is higher than I’d like to see it right now, but at least I know what it is, and when it’s paid off, I’ve got a pretty good idea of what the cost is going to be, and it’s probably going to be in the penny-and-a-half per kWh range. And I’m not going to find that anywhere else.”

“By staging these things, and not taking too big a bite out of any one particular project, we can keep our rates low and stable,” Maynard said. Bowling Green’s residential rates average around 7-1/2 cents/kWh.

“It doesn’t have to be that it ends up costing you a lot more money to look at renewable resources. I think it’s trying to come up with a balanced approach over time, and sticking with it, buying a little every year—because we always have load growth,” and Bowling Green wants to deal with load growth in a sustainable way, said Maynard.

Public Image and PR Value

Maynard states that public response to the wind turbine project has been overwhelmingly positive. “I’ve never heard a negative comment about [the turbines],” he says. “I’ve been in this business for…30 years, and I’ve never seen a project so positively received—unanimously positive.”

“They’ve been very positive for PR,” Maynard explained of the turbines. “We get contacted almost daily by somebody regarding a tour, a reporter wanting a presentation, the community—their economic development people push it, the visitor’s bureau pushes it, it’s truly been a very positive experience”

“If [the turbines] didn’t generate a kWh, they would have been worth it,” strictly for the positive publicity, quips Maynard.

Outlook for the Future

Regarding the possibility of future wind power projects in Bowling Green, Maynard is keeping his options open.

“We’re working with a couple of developers, one of them is pretty hot on maybe putting a couple of 20-MW projects in here,” Maynard said. “The advantage that they have with us, compared with tying in to an investor-owned utility system is, first of all, we own the system so they negotiate with us.”

In addition, a potential developer would not have to convince the Bowling Green community that a wind power project would be feasible and would have low environmental impact—that part has already been done.

“They’re not having to put it on the transmission system and negotiate a transmission contract with First Energy or MISO, they work with us and it just peels off load from our system working under an existing agreement,” Maynard added.

Such private developers would not be eligible for the tax-exempt municipal financing, as is Bowling Green. However, the developers would likely qualify for the production tax credit for wind power systems. Wind power developers could potentially sell or transfer ownership of their projects after their production tax credit expires, to tax-exempt entities such as universities or municipalities.

Maynard said that wind turbines are an important part of their generating portfolio. “I believe we will continue adding them as we go forward. Our community is very interested in renewable and sustainable sources of power,” he said.

Maynard said that Bowling Green’s portfolio includes around 20% renewable power from hydro, wind, and solar sources.

“We don’t need a renewable portfolio standard—we’re already doing it,” he added.

References

1. Bowling Green Utilities-Electric Division Turbine Homepage (

2. BG Wind power joint venture (OMEGA JV6) annual report.

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3. AMP-Ohio General Website (

4. Green Mountain Energy website (

APPENDIX A—TURBINE DIAGRAM