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Posts Tagged ‘Wind’

For those interested in wind, we are pleased to announce the public release of the Distributed Wind Site Analysis Tool (DSAT).  Built with funding from US DOE’s Wind Powering America Program and other sources, DSAT is a powerful new online tool for making accurate performance predictions for distributed wind energy projects.  Combining proven calculation techniques, computer modeling, and real-world performance data, DSAT is a valuable resource for landowners and communities considering wind power projects.

Please visit http://dsat.cadmusgroup.com to see DSAT for yourself.

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Community wind projects often face opposition on a range of issues. Concerns about potential noise and visual impact, avian (bird) mortality, and impact on residential property values are the most common. While the permitting process includes components that provide stakeholders with more information and prompts mitigation measure development, community wind project teams do best by proactively hearing and responding to their community’s concerns.

Impact on residential property values is one of the most polarizing issues facing community wind projects. While introducing community members to research on property value impacts and other issues is just one aspect of easing their concerns, it can be important to building project support.

One potentially valuable resource is “Wind Energy Facilities and Residential Properties: The Effect of Proximity and View on Sales Prices” –a Lawrence Berkeley National Laboratory-authored study on the relationship between wind projects and property values (Journal of Real Estate Research, 2011). This article is based on one of the most comprehensive studies to date on this issue, and it is one of only three peer-reviewed studies on the topic. The study looked at 7,459 homes within 10 miles of 24 wind projects across the country, and field visits were made to each home.

This article may be particularly helpful, as it examines three different (and common) perceived impacts of wind projects, all of which were found to have no statistically significant impact on the sale of homes in the study sample:

  • Scenic vista: A perception that a home may be devalued because of the view of a wind energy facility, and the potential impact of that view on an otherwise scenic vista.
  • Area stigma: A perception that the area surrounding a wind energy facility will appear more developed, which may adversely affect home values in the local community regardless of whether any individual home has a view of the wind turbines.
  • Nuisance Stigma: A perception that factors that may occur in close proximity to wind turbines, such as sound and shadow flicker, will have an adverse influence on home values.

By engaging community members in conversations about their concerns early and often, project teams can better understand prevailing attitudes about the issues and design an appropriate outreach effort tailored to the residents and other stakeholders.  Outreach efforts might include sponsored “fieldtrips” to other wind turbines in the region or inviting representatives from regions with completed wind projects to present. Alternatively, neighborhoods can host coffee nights at a local library or other community gathering point for open discussions. Ideally, such events would be hosted by a neutral third-party wind expert, such as an academic, representative from the state’s energy department, or consultant or developer not attached to the project.

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Wind projects can offer positive economic and environmental benefits for communities and project owners but need to be sited carefully and with sensitivity to the surrounding landscape.  One of the concerns frequently voiced over wind power projects is shadow flicker.

What is Shadow Flicker?

Shadow flicker is a term used to describe the shadows cast by moving wind turbine blades in direct sunlight.  Depending on the sun’s position, the weather, the turbine rotor orientation, and other factors, this flickering shadow can sometimes fall upon an occupied structure or other sensitive area.  Shadow flicker is usually of concern only for larger wind turbines, such as the multi-megawatt turbines used in community and commercial scale projects.  Smaller wind turbines, such as those used for residential applications, generally do not create noticeable shadow flicker impacts.

Is Shadow Flicker Dangerous?

There is no evidence that shadow flicker causes any harmful health effects.  In everyday life, such as driving a car, most people experience flickering shadows.  Shadow flicker is problematic because it may be considered an annoyance by the occupants or users of an area where it occurs.

How is Shadow Flicker Assessed?

Shadow flicker is typically expressed in terms of duration, usually in terms of hours of impact per year.  Calculating this impact involves a number of factors:

  • Sun position
  • Wind direction/rotor orientation
  • Cloudiness and weather
  • Location of sensitive receptors
  • Elevation
  • Terrain/obstructions
  • Turbine/tower specifications

Industry software packages such as WindPro, when used properly, are able to make these calculations and generate predictions of the shadow flicker impacts for the area surrounding the proposed turbine.  An example graphic generated by this kind of analysis is shown in the figure below.

This shadow flicker analysis reveals the anticipated impact on the area surrounding a proposed turbine.

The butterfly-like shape is made up by lines of shadow flicker impact, similar to the lines on a topographic map.  For example, a house with windows facing the proposed turbine located along the blue line could expect about 30 hours of shadow flicker in a typical year.

Are There Standards for Shadow Flicker Impacts?

Unfortunately, most zoning and other regulations related to wind power only refer to shadow flicker in a general sense, using language such as “shall generate no significant impact.”  Some statewide and international standards define “significant impact” as 30 hours or more of shadow flicker per year.

Can Shadow Flicker be Mitigated?

There are several ways to address potential shadow flicker impacts.  The best method is to have a shadow buffer zone between the proposed turbine and any residences or other sensitive receptors.  If that is not possible, shadow flicker can be mitigated by planting trees or other visual screens between the affected receptor and the turbine.  Finally, the project owner can program the turbine to shut down during certain times of day, or under certain conditions, to reduce shadow flicker impacts.

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Power Purchase Agreements (PPAs) are appealing to cities and towns for several reasons, and frequently because they require no upfront investment by the community. Rather, cost to the community (in addition to non-price factors) is the per kilowatt-hour (kWh) rate for electricity generated by the renewable energy system –the PPA rate. Different developers may propose significantly different PPA rates when responding to the same solicitation. However, PPA rates proposed that are noticeably lower than other bids received may be too good to be true. Inappropriate pricing can compromise the economic viability of these projects and increase risk to the community.

This diagram shows the relationship between parties in a typical, community-scale solar PPA in Massachusetts. Not all PPAs are structured in this manner.

When considering PPA price proposals, it is important to consider both the cost in cents per kilowatt-hour and how financeable the project is at the given PPA rate. PPA projects with PPA rate that is too low may suffer from significant delays as the developer seeks financing from financing parties looking for some return on their investment. Such delays and false starts waste the significant time investments that proponents make to introduce renewable generation in their communities.  In addition to lost momentum, incentives and other benefits (e.g., 30% U.S. Treasury Grant) that may be critical to a project’s economics may expire while the developer seeks financing.  Ultimately, if the developer is unable to secure financing, the project will likely fall apart.

 When examining PPA rates in cents per kilowatt-hour, bid evaluation teams should weigh the benefits of low PPA rates with potential risks:

  • Extremely low PPA rates and subsequent narrow margins can prevent conservative lenders from investing in the project.
  • In contract years 11 and beyond, the PPA rate should be high enough to fund operations and maintenance costs. That is, the PPA provider should have a financial incentive to continue to operate and maintain your system. PPA rates less than $0.02/kWh in years 11-20 should be considered cautiously.  If your community entered into such a contract, and the PPA provider abandoned the system, would your community be able to fund maintenance or decommissioning costs?

Low PPA rates may be workable in the context of large projects that will generate significant revenue for the developer, for example, through solar electricity sales to the community and SRECs. However, small and moderately sized projects –especially those with relatively high installed costs (e.g., lengthy interconnection runs, tree stumping required), may not be financeable at a low PPA rate.

Finally, many PPAs contain language that allows for developers to exit the contract prior to commercial operation if they are unable to find financing. Therefore, selecting a PPA rate that makes financial sense to your community, the developer, and their financing partners is important to helping all parties efficiently realize the benefits of renewable energy.

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 DOER filed a report with the Massachusetts Department of Public Utilities outlining recommendations for utilities to improve the process of connecting new renewable energy generation installations to the electric grid. In its filing, DOER attached the Massachusetts Distributed Generation Interconnection Report which surveyed customers seeking interconnection in the state, researched policies in other states, interviewed utilities, and made specific recommendations about improving interconnection processes and policies.

The status of progress on these issues and scheduling for distributed generation (DG) workshops is available at the Massachusetts DG and Interconnection Website (http://bit.ly/MADGIC).

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One of the main determinants of whether an RFP for a Power Purchase Agreement (PPA) will attract qualified developers and advantageous bids is estimated total potential capacity. If this information is not available, site area or rooftop square footage can serve as a proxy.

More Space. More Attention.

When conceiving of a renewable energy project, cities and towns should look to aggregate potential sites. Whether or not a PPA makes sense for the community will depend on the total amount of capacity that is feasible. For example, some PV developers require 500 kW of PV potential before proposing a solar PPA. Others will not pursue landfill solar projects that are smaller than two (2) MW. By aggregating as many rooftops and open spaces as possible in your project RFP, you will attract more vendors and capture economies of scale.

Whether conducting your own due diligence or investing in site assessments, your RFP should ultimately focus on quality sites. Buildings with aging roofs, for example, should be set aside for future phases. Those with many rooftop penetrations and little usable space should similarly be deferred.

 If publicly-owned buildings and open spaces are very limited, look elsewhere. Consider partnering with a neighboring municipality or other public entity in the region (e.g., schools, hospitals). This may be especially helpful where the potential partner has experience with renewable energy projects. Together, you may receive bids that neither could have attracted alone.

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 Many communities interested in renewable energy have questions and concerns about net metering and interconnection. This is particularly true among communities exploring landfill solar or community wind projects, which are largely dependent on the Massachusetts net metering incentive.

DOER has succeeded in getting a commitment from the Massachusetts utilities to host monthly distributed (on-site) generation workshops. These workshops will cover the basics of interconnecting distributed generation technologies in investor-owned utility territories in Massachusetts as well as other pertinent distributed generation topics, including net metering. The DOER’s Massachusetts Distributed Generation and Interconnection Main Page has more information about upcoming workshops, as well as links to presentation materials from past events. In addition, the DOER DG site provides additional resources on these topics, including the “Basics of Interconnection and Net Metering.”

See http://bit.ly/MADGIC.

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