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Urban planning and solar access

Many aspects of the urban planning and development process, from the layout of the roads to the building massing and shape of the roofs, will crucially affect the feasibility and performance of any PV systems installed. However in a new development planners may define the site layout before solar access is raised as an issue, and infrastructure such as roads and electricity supply may even be installed before developers are appointed.

If solar access is taken into account at the earliest planning stages, in the same way as car and pedestrian routes or the need for parking, it is usually possible to ensure that the majority of buildings on a site are orientated between South East and South West to have good solar access. If it is not taken into account there is a risk that many of the buildings will have poor solar access. Not only will this lower the feasibility of installing photovoltaic systems, it will also restrict the use of passive solar design techniques, daylighting and solar water heating. The resulting urban layout will be in place for hundreds of years, restricting the feasibility of using any of the solar technologies now and in the foreseeable future. The presentation by Kees Duijvestein on PV in the urban planning process at the European seminar on PV and Urban Planning, March 2008 gives more details on PV as part of sustainable urban planning.

The sizing and layout of the electricity supply network may also be fixed fairly early on. However with moves towards sustainable construction there is an increasing trend towards micro-generation of electricity in buildings. These micro-generators can range from micro-CHP systems to micro-wind to PV. The Distribution Network Operator (DNO) may need to take such embedded generation into account when designing the local electricity network. See the section on grid connection for further details.

At many of the developments where PV has been installed the decision to include PV was made at a late stage, long after the site layout had been fixed. In many cases developers or builders who had become interested in PV had looked at the projects that were already underway and selected areas where PV could be installed on the basis that the development site concerned happened to have a good solar layout. Other sites available were not suitable for PV due to factors that could easily have been changed if they had been considered at an earlier stage. If we do not start taking solar access into account earlier in site planning the proportion of buildings that can make use of solar energy will be a fraction of what it could have been.

The approach towards urban planning, who undertakes it, when and at what level of detail varied quite dramatically between different countries, even the term ‘town planning’ means different things in different places. In some countries it appears to be easier than in other countries to include PV early on in the urban planning process.

In the Netherlands top down planning of major new developments is normal. As part of this there is a long consultative process during which PV may be added and urban designs modified. The Nieuwland case study reviews the first large urban PV project, realized in 1999, here solar optimization was taken into account in the urban planning phase with the land being parcelled out to provide as many roof surfaces as possible suitable for the installation of solar panels. The Stad van der Zon (City of the Sun) case study, again in the Netherlands also took the sun as one of the starting points in the urban planning, although there have been some comments that this was more as a philosophical approach than a practical, technical approach.

The approach is slightly different in Germany where the case studies demonstrate a willingness on the part of some municipalities to commission detailed analysis and shading simulations of urban renewal or development areas and use the results to inform developers and building designers. At Gelsenkirchen-Bismark, for example, an overall urban plan was developed which included a simulation of shading and solar irradiation on building surfaces. The initial draft of the area plan, with building massing and layout was evaluated and some modifications suggested regarding the height and distance between the buildings in order to provide each building with an ideal sun exposure. To avoid major shading of the building surfaces an advisory committee was formed to assist individual investors.

Shading visualization and urban plan Gelsenkirchen-Bismark

Also in Germany, a solar urban master plan was prepared for Berlin in order to determine the solar potentials of the different city quarters. The results were brought together with an urban renewal programme aimed at stimulating investment.

In both France and the UK the case studies available mainly reflect PV being added into an urban plan at a later stage in the urban planning process. This may relate to responsibility for detailed urban planning being more split between municipal planning departments, who tend to set guidelines rather than prepare detailed plans, and commercial developers who are then responsible for a greater part of the detailed urban planning. These breaks in the chain can make it much harder to carry a plan through to completion.

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