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Wind turbines for a residential building


Our client was the owner of a portfolio of high-rise residential buildings. It planned to install wind turbines on several of its buildings. The aim was to enhance its reputation for sustainability by reducing greenhouse gas emissions, offsetting energy use from other sources and striving for a ‘zero carbon’ outcome. The financial benefits were to be shared with the tenants of the buildings.

The risk assessment we facilitated provided a comprehensive understanding of the challenges the project would face and how they were related to one another.

Background and purpose

We were asked to facilitate a risk assessment for the pilot study, an initial installation on one building. It was hoped the risk assessment outcomes would be a useful template for other similar installations on the remainder of the buildings in the portfolio.

The owner planned to use multiple vertical-axis wind turbines. These have advantages over horizontal-axis wind turbines when located on a building:

  • They can be grouped more closely, so they maximise the use of limited rooftop space
  • The main generator and gearbox mechanisms are at the base of the turbine, so they are much easier to install and to access for maintenance
  • They operate in a wide range of wind conditions, including in turbulent winds associated with the top of a building
  • They do not need to move if the wind direction changes, so they are simpler to design, build and maintain.

Risk assessment


Only a short period was available for the risk assessment, so only a small set of key elements was used for structuring the workshop (Table 1). Nevertheless, it proved sufficient for the owner to gain an understanding of the main risks and develop an effective approach to the installation.

Table 1: Structuring the workshop


Topics included


Approvals, size, appearance, plant and services, structural load, electrical interconnection


Access, work areas, plant and equipment, schedule, safety, residents


Electrical output, impact on the building, Community and the environment, environmentally sustainable development (ESD) certification, safety, maintenance


Policy, ESD, business significance

The key elements were elaborated in the mind map shown in Figure 1, to stimulate the exploration of risks and ensure the subject was covered comprehensively.

Figure 1: Structuring the workshop

The consequences of risks were analysed in terms of criteria used to rate risks on related projects being undertaken by the owners:

  • Schedule performance
  • Capital cost
  • Maintenance cost
  • Stakeholder satisfaction
  • Image
  • Safety.

The key elements were addressed one at a time, capturing risks in terms of a high level descriptive title with multiple causes, multiple impacts and a list of existing controls.


Twenty-one risks were identified.

  • Two risks were rated extreme: an adverse reaction to the visual impression of the turbines, and interference with tenants on the top floor arising from the structural fixing of the turbines on the roof. These were allocated to individuals for priority attention.
  • Ten risks were rated high. Risk owners were allocated to these.
  • Seven risks were assessed as being almost certain to affect the project. Their high likelihood meant that these were effectively planning assumptions that had been overlooked up to that point.
  • Two risks were identified with potentially catastrophic consequences although both were considered to have a very low likelihood of affecting the project.

Many of the risks interacted with one another. A pictorial representation of the connections was prepared to aid in understanding options for risk treatment (Figure 2). It is notable that all risks lead ultimately to the consequence of failing to sell the idea to the tenants, an outcome that is fundamental to the success of this project.

Figure 2: Relationships between risks

The output of the workshop was used to refine the initial plans for the turbine installation and prepare a submission for funding and approval to proceed.


At a relatively early stage in the development of the project proposal, Broadleaf was able to add significant value with a modest level of effort. We did so with a process that not only exposed risks that could affect the work but also identified important consequences the project was almost certain to encounter that had not been allowed for to that point.

The nature of the risks and options for treating them were clarified by examining the relationships between risks, focusing on the potential for one risk to stimulate or exacerbate another.

As well as identifying specific actions and areas for attention, the understanding generated by the risk assessment gave the planning team added confidence in the value of the work they were doing, the way they were approaching it and the outcomes that could be achieved.

Property portfolio manager
Climate change
Services included:
Risk assessment and risk treatment
Project risk management