Keith Yzquierdo MCEN 5228 Sustainable Energy Distributed Wind on the CU- Boulder Campus

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1 Distributed Wind on the CU- Boulder Campus The campus 1. There are a lot of roofs- - could we put turbines on them? Introduction CU- Boulder considers itself a national environmental leader 2. The main campus is home to several PV installations, a cogeneration plant, and a variety of energy saving plans. What else could the campus do to reinforce its commitment to the environment? Quinnipiac University in Connecticut recently installed an array of small wind turbines on its campus 3. At Logan International Airport in Boston, 20 small turbines were installed on the roof of an office building 4. David Cameron, prime minister of the UK, installed a small turbine on his roof (it was later removed for zoning reasons). 5 Could small- scale, distributed wind turbines work for CU- Boulder s main Rooftop turbines at Logan Airport. campus? 4 Scope This investigation considers a single vision, viz., a number of small wind turbines distributed throughout the main campus of UCB, preferably on top of existing structures. Small- scale turbines are defined by the American Wind Energy Association as turbines rated at 100kW or less 6. This is a technical feasibility study. The economics are not examined. Local zoning restrictions are also largely neglected, but are briefly mentioned where they might prove to be a significant barrier.

2 Why On- Campus Wind Power? If we accept the axiom that clean energy is good, then it would benefit CU to have clean energy technology in the public eye. The PV panels on campus are largely invisible to the general public, and so do not convey CU s commitment to being an environmental leader. Wind turbines, however, would be much more visible. They would clearly communicate that CU is committed to clean energy. (Of course, a visible wind turbine that is not spinning could communicate something quite different!) An on- campus installation could actually complement existing aesthetics, and add value to the campus. Quinnipiac University s turbines serve as a sort of kinetic sculpture garden. Located on towers, the area around their bases serves as a gathering place much like a plaza outside a building 7. Of course there is the potential to save money. Depending on the levelized cost of electricity, wind turbines could be financially beneficial for UCB. This would depend on, among other things, the financing and performance of the Winspire turbines at Quinnipiac University 7 machines. That the turbines would save money should not be assumed. The turbines on campus would need to be small. Large turbines require a significant amount of space, would be plagued by NIMBY concerns, and generate noticeable noise levels. As mentioned above, the visibility of turbines could be a good thing, but there is certainly a point at which the visibility is bad. A 400ft tall turbine would be very visible on the main campus, but it is unlikely to be well received by the public. The Wind Resource Every wind project should start with an assessment of the wind resource. Fortunately, one of the data sources available to SAM was collected on the UCB East Campus, approximately one mile from the main campus. Unfortunately, the wind resource is exceedingly poor. Boulder does experience some very high winds, and it might seem counterintuitive to some that the wind resource in Boulder is very poor. But for all those windstorms, there are many more calm days, and the average annual wind speed on the UCB East Campus is a mellow 3.90 m/s at 50m 8. When there is wind in Boulder, it is very turbulent. Boulder is Closest SAM wind data file

3 Keith Yzquierdo MCEN 5228 Sustainable Energy located on the lee side of the Rocky Mountains. The Rockies disrupt the prevailing west to east winds like rocks in a streambed 9, inducing very turbulent flows. The wind does not settle down again until quite a ways out in the plains (see the Colorado 50m wind map10). What s more, Boulder, and especially the UCB main campus, is an urban environment, characterized by buildings, trees, and hills. These obstacles further increase the turbulence of the wind resource. Turbulence is bad for wind turbines. Horizontal axis wind turbines (HAWTs) must be aligned with the wind in There is more wind in eastern Colorado where the turbulence settles.10 order to extract power, and high turbulence leads to turbines chasing the wind as it changes direction. The rapid accelerations due to changing wind speed/direction also cause more wear and tear on the turbine, increasing O&M costs and decreasing availability. The wind resource improves at higher altitudes, but in the case of Boulder the turbines would need to be prohibitively tall. As mentioned above, the resource at 50m is poor, so the towers would need to be taller than that. For comparison, the Stearns Towers in Williams Village those big buildings that stick out like Boulder s sore thumb are just shy of 50m tall11. An effective turbine would need to be so high that it would dwarf the Stearns Towers. It would block views of the flatirons and become the most prominent feature in Boulder. Such a proposal is unlikely to succeed. The Pearl River Tower12. Wind is funneled through the slots on the façade and into VAWTs. On Roofs The wind resource pretty much kills the idea of wind power on campus, but even if the resource were sufficient, the vision of rooftop turbines would probably not be realized. Structural Problems Wind turbines transmit significant dynamic loads through their structures into whatever they are mounted to. Roofs are not designed with these dynamic loads in mind, so only very small turbines can be safely mounted on rooftops. There are buildings that are built with integrated wind in mind, such as the Pearl River Tower12 in China, but none of the buildings on the UCB campus were designed with this in mind. Turbulence (still) Buildings create turbulence, so unless the tower on the roof is very

4 high, turbulence is still an issue. A taller tower means larger moments about its base, so the structural issues pop up again, along with the other height concerns mentioned above (views). Immature Technology There is no good data publicly available to evaluate rooftop systems, but the anecdotal evidence is largely negative 13,14. A noteworthy finding is that small- scale spatial variation in urban environments is significant. In a UK study, The best performing turbine on top of a ten story building provided enough energy to power a house for the day but another turbine on a low rise a few miles away did not even generate enough electricity to run the turbine s electronics. 15 Siting studies must be extensive. A Note On Vertical Axis Wind Turbines (VAWTs) In the world of small- scale rooftop wind, the VAWT is often touted as a panacea. Since they do not need to adjust for yaw, it seems that turbulence would be less of an issue. Despite such promising claims, these turbines have not seen large- scale commercial success, and the technology remains immature. One of the better publicized VAWTs, the Windspire, was tested at NREL and failed before the tests were complete 16. Lack of commercial success, and subsequent immature technology, does not necessarily mean an inferior technology, but VAWTs are also inherently less efficient than HAWTs 17. Unless the turbulence conquering features of VAWTs prove to be real and significant, it is unlikely that these less efficient machines will surpass HAWTs in the market. VAWTs 13,17. There are many different designs, but none have enjoyed large- scale commercial success. SAM To demonstrate the performance one might expect from a small turbine on the UCB campus, SAM was used to estimate the annual output and capacity factor (Cf) for several turbines. The simulations were run for the 8303 and the zip codes is the UCB East Campus, and is a location in NE Colorado, near the Nebraska border. The location was chosen for comparison because it has a good wind resource, and is close to a wind farm from which CU has purchased energy in the past. The three turbines were chosen because they are small enough to be located on rooftops and their information was available in SAM. The data in the table below are for individual turbines with a 50m hub height. The rotor diameter is listed just to give an idea of the size of the devices. Turbine Rotor Diameter m (ft) UCB East Campus (80303) NE Colorado (80747) Annual Annual Output Capacity Capacity Output (MWh) Factor Factor (MWh) Bergey 1kW 2.5 (8.25) % % Skystream 2.4kW 3.7 (12.21) % % Bergey 10kW 6.0 (19.8) % % The turbines in NE Colorado will produce around three times as much energy as those on the UCB campus. The poor on- campus performance translates to an enormous number of turbines if they are to make any significant contribution to campus energy production.

5 The location of the comparison site, zip Conclusions The wind resource on the UCB campus is poor, so investing in on- campus wind power is not advisable. Even if it the resource were good, rooftop wind turbines are an immature technology, and suffer from a variety of problems. The SAM simulations clearly indicate that CU would be better served to place a turbine elsewhere in Colorado, or to contract to buy the power output from an existing turbine. (This has been done in the past CU agreed to buy all the power output from a single turbine on Xcel s Ponnequin wind farm 18, which is near the NE CO location used in the SAM simulations.) Investing in on- campus wind would not help CU reinforce its commitment to clean energy. Images of the Ponnequin wind farm. In 2000, CU purchased all the power from a turbine near here.

6 Images Keith Yzquierdo Bergey 1kW turbines 19 Skystream 2.4kW turbine 20 Bergey 10kW turbine 19

7 References: Keith Yzquierdo 1 Photo from Boulder 2 The University of Colorado: 3 Quinnipiac University: an- impact/on- our- campuses/green- initiatives 4 NY Times: 5 The Telegraph: Cameron- forced- to- remove- turbine.html 6 American Wind Energy Association: 7 Quinnipiac University s Picassa Photo Gallery: 8 Data from SAM. 9 UCAR, 10 DOE: Colorado 50m Wind Map, 11 Emporis. boulder- co- usa 12 Wikipedia, Pearl River Tower: 13 Wind- Works.org. works.org/articles/rooftopmounting.html 14 The Telegraph. turbines- like- David- Camerons- dont- provide- much- electricity.html 15 Ibid. 16 NREL Windspire testing: 17 University of Illinois: rbines.pdf 18 CU Boulder. colorado- students- make- campus- no- 1- wind- power 19Bergey: 20Southwest Windpower: 3.7#upclose