Giving Control to the User

Interactive Wind Park Planning in a Visualization Center Giving Control to the User Björn ZEHNER

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Introduction

The German government aims to increase by about twofold the contribution that renewable energy makes to overall electricity generation by 2020 and has amended the German renewable energies law (Erneuerbare Energien Gesetz, EEG) towards achieving this aim (BMU, 2008). The contributions required to achieve this goal will need to be broken down on a spatial level (e.g. different counties) and between different forms of renewable energies (e.g. wind-power, solar power), as described in MONSEES (2009). However, energy generated by wind turbines will have to make a contribution towards fulfilling this goal. The current regulatory practice regarding land use means that suitable locations for new wind parks and those that are suitable for repowering are becoming scarce (OHL & EICHHORN, 2008, OHL & EICHHORN, 2009). The aim to increase wind energy production is beginning to conflict with issues related to environmental, nature and landscape protection. The UFZ-Helmholtz Center for Environmental Research is participating in a project that should contribute to minimising these conflicts. A mathematical model, incorporating economy and ecology, helps to evaluate and weigh up the costs to society for different scenarios. One input that this model will need is the importance people attach to different attributes, e.g. if they find the size of a wind park more or less important than its distance to the next village or other natural protection issues. In order to evaluate the user’s preferences, two public opinion polls have been done: one via the internet (MEYERHOFF ET AL., 2008) and one with the help of a commercial company (MEYERHOFF ET AL., 2009). People questioned where given a set of choice cards that showed different wind park scenarios, and asked for their preferences. Attributes under question were, for example, the size of the wind park (number of turbines), the height of the turbines, the minimum distance expected to be required to the next villages and the number of wind parks. Further, the polls tried to evaluate how sensitive people are to the impact of the wind parks on other environmental issues, such as the protection of species. Simply using opinion polls with choice cards might be debatable. It is clear that public opinion should be taken into consideration. Even if this only generates additional parameters in the overall planning process, this will often lead to more widely accepted decisions. However, many of the questions asked in interviews or on choice cards, such as the size of the turbine or the distance required to the next village, are often questions that members of the general public decide on the basis of aesthetics (besides the question of noise emission). The person asked is required to imagine the visual impact this scenario will have on the landscape. A professional planner who has to think about these questions every day can imagine this based on work experience, but other people will not be able to answer correctly without 3D visualization. With visualizations on printed paper or on the

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monitor, users still might get a wrong impression because the size of the different objects depends on the size of the screen or paper used for the presentation. They can only compare the height of the turbines to trees or houses alongside to gain an idea of size. Head-tracked projection-based virtual reality systems can show the wind power engines and the landscape on large screens and with the size as it would be perceived by users within a real landscape. So it can be anticipated that virtual environments are very valuable in helping members of the general public to formulate their opinion before or during participation in polls and interviews. With this in mind, the UFZ is looking at the different opportunities that the use of its large scale projection-based visualization and virtual reality system might offer for tasks, such as interviewing members of the public about their opinions on the location and different designs for potential new wind parks. The idea is to provide a demonstrator that shows how this technology might be used for these tasks and to present it to involved decision makers and the public, collecting feedback from them and evaluating the system. From the point of view of visualization and virtual reality, the focus of this article is on two questions. The first one is if it is feasible to leave the control over the design process completely to the participants in such an interview, rather than asking them to explain their views while an operator changes the visualizations accordingly to meet the participants’ requirements, as is currently often the case. To do this evaluation, we have implemented a system that allows the users to perform simple visually driven planning tasks themselves and presented it at a public event for user evaluation and subsequently to a panel of people who are involved in wind park planning. The second question is which of the different technologies, supported by our visualization center, can be seen as most suitable and necessary for the evaluation process. To answer this question we have presented our system to the aforementioned second group using different technologies for the same visualization.

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System design

The UFZ runs a large projection-based visualization center which is shown in Figure 1. The image is generated by 13 SXGA+ projectors which are at the rear side of the system and the rendering is done using a cluster of 13 workstations. The display system provides stereoscopic visualization, giving the users a real 3D impression of the shown scenery. A tracking system can follow the user’s movements and adjust the perspective in real time. The eye separation for the stereoscopic rendering can be done using two different technologies. With active stereo, the images for the left and right eye are shown alternating and shutter glasses are used to separate them. Infitec (JORKE & FRITZ, 2003) separates the image for the left and right eye by using slightly different wavelengths of the light spectrum to represent a colour, using suitable filters. Both technologies have their pros and cons. In the UFZ’s display, the visualization with shutter glasses provides a brighter image with a higher contrast, but the glasses need an infrared signal for synchronization with the display and do depend on batteries. So, for use with novices, they are slightly unreliable and people who do not know stereoscopic visualization might not realize that the technology has failed but instead assume the visualization to be wrong or of low quality. Infitec glasses in comparison, as a passive stereo technology, are very reliable but the

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B. Zehner

image quality is slightly worse (e.g. darker and less contrast). A third option for rendering is to switch off stereo, generating a mono image. Using a visualization system, such as the one at the UFZ, for landscape visualization has an impact on the software that can be used and implemented and constrains the way the digital landscape has to be generated. The overall workflow for scene generation and software/hardware implications are described in a more detailed fashion in ZEHNER (2008). The scenario focuses on the visual impact seen from a short distance (up to 2 km), and many of the effects that have been shown to be important from further away, such as atmospheric scattering (BISHOP, 2002), are not included. The focus is not on the question of where the wind park should be located regionally but more on how it should look when the location is already clear. However, the system could be easily extended to meet other requirements too.

Fig. 1: The UFZ's visualization center, providing high resolution images, stereoscopic visualization and head tracking. On the right the two monitors from the operator desk can be seen. The digital landscape used for the investigation is a small region near Leipzig that has been earmarked in regional development plans to be suitable for a small wind park. The digital landscape has been generated on the basis of GIS data and areal images obtained from Google Earth. The overall extent that has been modelled is an area of 4 by 4 km with the potential wind park situated somehow in the center. All objects (e.g. trees, turbines) are modelled in real world size. More than 30,000 trees, taken from the Greenworks Plant Libraries and represented with a high level of detail, are placed in forest regions and along avenues. Due to limited manpower, the houses in the small villages are represented by simple shapes without textures that have been digitized from the areal images. For system control, we extended the commercial software VRED from PI-VR GmbH which is used for the visualization of static scenes in our visualization center. We added two separate windows that can be shown on two linked monitors, one for navigation and one for interactive wind park planning, so that these two interaction tasks can be done on a different scale. In the navigation window the areal image is shown and two markers with

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different colours that indicate where the user is and where he is looking. By placing the “look at” marker within the wind park, users can move with the other one everywhere in the region. The choice cards mentioned in the introduction, for example, use scenarios with distances of 750m and 1500m to the next villages. So users can look from these distances and different directions towards the windpark (the distance to the wind park is indicated in the user interface) or they can choose another place in a village. The 3D view in the visualization center is adapted accordingly, showing the landscape with the wind park as it would look from this spot. This way of navigating also ensures that the viewer always focuses on the item under investigation (the wind park) and that users can not fall off the “fringe” of the landscape as might be the case where using direct 3D navigation. The user can also scale up and down the areal image, adjust viewing height and see the distance between the two markers. The window for the interactive wind park planning is shown in Figure 2. Users have a twodimensional map view of the area that is earmarked for wind park use. They can choose from a predefined set of different turbines that are, in terms of height, rotor radius and rated power, similar to existing ones (Table 1). The attributes for the selected turbine are shown in the user interface. The users can choose a turbine and place it in the map view. They can select and move turbines, change their type and remove them. In the real world a minimum spacing between the different turbines is required. This is indicated by a circle on the map. The main wind direction can be given and thus the orientation of all the turbines. The rotation of the turbines can be switched on and off. As most people feel even more disturbed by the wind turbines due to their rotations, this has always been left switched on. Further, the rated power of all the placed turbines is added up and shown in the user interface.

Fig. 2: Window for wind park planning. See text for details. On the 3D display we show the resulting digital landscape including the wind turbines, so that users can evaluate visually if the resulting scenery is what they expected or if they would like, for example, to change the type of the turbine. Tab. 1: Data for the different wind turbine types (taken from OHL & EICHHORN, 2008). Type Hub-height Rotor diameter Height Rated power

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Enercon E82 Vestas V90 Enercon E126

3

80m 105m 139m

82m 90m 126m

121m 150m 202m

2 MW 3 MW 6 MW

Evaluations

3.1 Presentation of the system at Leipzig’s Regional Science Day One idea behind the visualization system as presented here was to enable users to control the visualization and so give them the opportunity to try out different wind park scenarios under the constraint that the resulting wind park should generate a certain amount of rated power. It is clear that people can gain better insight into the visual effect of different planning decisions if they can quickly and efficiently generate and change different scenarios. In this way people can play around and become aware of the constraints the planners are exposed to. Incorporating an operator who takes care of entering the chosen changes is usually one factor that slows this process down. Another effect of giving control to the layman is that their preference in terms of size and number of engines becomes visible without the need to really explain to them which parameters are of interest for the investigation (the parameters are hidden in the different predefined turbines). Thus people might be less subject to preconceptions. To test if people can easily work with the system, we presented it at a public event, a regional science day,, where all the research institutions in Leipzig presented their ongoing research. Groups of about five people at a time visited the visualization center. One of these people sat at the operator desk and was given the task of planning a wind park that generates a prescribed minimum amount of rated power. Afterwards, only these people were asked to complete a questionnaire on the usability of the system regarding the interaction, orientation, visualization and if it helped to complete the given task. Further we asked them if they found the stereoscopic visualization important and if they felt disturbed by the special glasses they had to wear. Answers could be given in 5 steps ranging from 1 for yes up to 5 for no. They also were asked to enter further suggestions as text. Overall 13 individuals, who each took on the role as an “operator”, were interviewed and the results are shown in Figure 3. None of the users felt that they had difficulties with the given interaction tasks and with orientation in the virtual landscape. Nearly all of them found the system helpful in completing the given task and considered the stereoscopic visualization important, despite more than half of the individuals feeling at least somewhat disturbed by the goggles they had to wear. The detail of the visualization was one of the points with which people were less content. The feature that for most of these critical people was missing was sound, in order to make those questioned aware of the noise emission generated by wind turbines. Further, people asked for more detailed representations of the houses and green areas, such as meadows.

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Fig. 3: Results from the questionnaire in the public event. Horizontal axis: agreement of people. Vertical axis: number of votes. See text for more details.

3.2 Presentation to a panel of people involved in planning processes We used the first steering meeting of the related project to present the system to a panel of people who are involved in the planning processes, such as specialized lawyers, members of ministries and environmental associations. In contrast to the presentation at the public event this was done, due to time restrictions, by an operator who explained to them which different parameters could be adjusted and how a wind park can be assembled. Their overall reaction was very positive. We then took the opportunity of presenting our system to these people, while using the same visualization scenario but the two different stereo separation technologies and mono, in order to get feedback on what they think is the best method for the given visualization task. As passive stereo (Infitec) is more reliable and thus preferable for presentations to the public, it is important to know if the use of the different technologies will be perceived by non visualization experts. We then gave them a questionnaire about how suitable they found the given technologies for the given task, ranking them between one for very good and 10 for unsuitable. The results are shown in Figure 4.

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Fig. 4: Results from the questionnaire for the group of people involved in planning processes. Horizontal axis: number of individuals. On average there is hardly any difference between the ranks of the two stereoscopic technologies. In contrast to people who often work with the UFZ’s display, others from outside who see it only for a short time period seem not to perceive a real difference. Not using stereoscopic visualization was seen as less suitable for the experiment. However, when we asked the people which technology they would choose, 4 out of 16 voted for using mono. Their reasons were that they found it uncomfortable to wear special goggles and that in their opinion there were only few advantages provided by stereoscopic visualization. One stated that the use of mono visualization would allow for low cost transportable systems.

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Conclusions

The system presented could be easily used and has been well received both by novices at the public event and more knowledgeable people in our project meeting. Stereoscopic visualization appears to be seen as the better solution, even if not as a must, by those who are involved in planning processes. Using the more reliable Infitec technology for larger audiences seems to be no problem. The number of interviewees questioned so far is too low to provide reliable statistics and system evaluation, but the trend is clear. Further, while the public event was suitable for assessing if users can instantly work with the system, it was less suitable for seriously discussing the inherent content of our visualization. Many people felt unaffected by wind parks and were more interested in the technology shown to them. A much better test scenario would be to apply the system as presented here to a real planning case so that the test users are really affected by the discussion. Unfortunately (or fortunately ?) most potential areas for new wind parks or repowering are outside Leipzig and our visualisation system is, in contrast to the virtual landscape theatre from the Macaulay Institute in Aberdeen (MILLER ET AL., 2009), not transportable. So, we would require people to travel to the UFZ just to take part in the discussion, which might be resented by many of them. Another problem is that most planning institutions and companies are too small to support the use of this technology. As a result, the research done at the UFZ has so far been mainly method-oriented and focused on technologies.

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Acknowledgements

I would like to thank Markus Eichhorn, Cornelia Ohl, and especially Jan Monsees for their help during the public event and for fruitful discussions. Further I thank Alison E. Martin for proofreading and improving the manuscript.

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References

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