A Tanzanian woman shows the instalment of solar lighting and electricity in her home, thanks to a scheme backed by UK aid. Investments in solar cells and other types of photovoltaics in Tanzania can positively affect progress in achieving several of the Sustainable Development Goals (SGDs). Photo: DFID UK/Flickr

Bildtext får vara max två rader text. Hela texten ska högerjusteras om den bara ska innehålla fotobyline! Photo: B. Christensen/Azote

Global goals

Shedding light on the SDGs

How investments in solar energy go beyond access to electricity to positively affect people’s life expectancy and years of schooling

Story highlights

• Using a new integrated system dynamics model the study analyses impacts of substantial investments in photovoltaic capacity in Tanzania

• The three Sustainable Development Goals on health, education and energy were included in the model

• Such integrated models can highlight links and facilitate a shift to a development discourse grounded in systems thinking

Keith Richards once said "You've got the sun, you've got the moon and you've got the Rolling Stones." Albeit disproportionate, that might be true. But for even more people you've got the Sustainable Development Goals, the 17 global goals aimed at transforming our world into a more sustainable one. This includes ending poverty, hunger and improving health and education.

Imagine if we could reach several of these goals at the same time.

Well, consider this: investments in solar cells and other types of photovoltaics in Tanzania can positively affect people’s life expectancy, years of schooling as well as access to electricity. That adds up to progress in achieving three of the goals: SDG 3 on healthy lives and well-being, SDG 4 on education, and SDG 7 on energy. This is the finding of a recent study published in the journal Sustainability Science by centre researchers David Collste and Sarah Cornell, together with Matteo Pedercini from the Millennium Institute, USA.

Guiding policy

The paper describes how a new national system dynamics model (see methods below) was developed and used for an integrated cross-sector analysis of the impacts of substantial investments in photovoltaic capacity in Tanzania.

These kinds of broad system analyses, the authors argue, are crucial for addressing the 17 SDGs and creating planning tools that guide policy makers.

The goals, and the effectiveness of the policies addressed to achieve them, depend on each other. Implementation efforts that isolate goals one by one and overlook these systemic interdependencies may hardly be fit for purpose.

David Collste, lead author

Integrative models and synergies

It may not come as a surprise that the study’s model simulations showed that investments in photovoltaics are directly relevant to SDG 7 on affordable and clean energy. But access to electricity affects many other factors that can contribute to sustainable development – or that may present bottlenecks for achieving sustainability goals. With the aid of photovoltaics students can spend more time studying with better light quality (SDG 4). Likewise, gaining access to solar electric power can substantially reduce negative health effects from indoor air pollution caused by the use of solid fuels and kerosene for cooking and lighting (SDG 5).

In addition, model simulations showed that progress on these three goals can synergize and lead to broader system-wide impacts. While this particular study only looked into one national example it clearly illustrated how an intervention in one specific area can positively influence several SDGs at once. The new work contributes to a family of iSDG models that can be used to support similar analyses for policies related to all the 17 SDGs, both individually and concurrently.

"We believe that integrated models such as the iSDG model can bring interlinks to the forefront and facilitate a shift to a discussion on development grounded in systems thinking," they explain.

Avoiding the silo approach

In spite of the many benefits of using integrated models for assessing SDG attainment, the researchers also caution against an over-reliance on them and highlight several limitations. Reality will always be more complex than the model, meaning for example that there may be unanticipated effects of policies that are not included in the scope of the model.

“Models can assist us in structuring our thoughts and put light on unintended consequences of different policies, but they do not immunize us against uncertainties and unpredictable real-world behaviours,” the authors write.

Nonetheless, models can play a crucial role in bringing systems thinking into the attainment of multiple SDGs. Without this kind of research and dialogue with the decision-makers responsible for implementing the SDGs, there is a risk of repeating the silo approach that was so prevalent in the implementation of the UN Millennium Development Goals that preceded the SDGs.

Overview of the iSDG subsectors. The outer green field includes the environment subsectors, the middle red field the society subsectors and the inner green field the economy and governance subsectors. Source: Millennium Institute


The new integrative “iSDG model” used in the study is based on the Millennium Institute’s earlier “Threshold 21” model, and stems from the discipline of System Dynamics. Such models are constructed as simplified representations of real-world systems and are used to explore different what-if questions and to find potential system-level leverage points. The links between the three SDGs were mapped and included in the model as additional variables and new causal loops. This allows the model user to investigate the resulting behaviour of different policy options. As the first national customization of the iSDG model, the study applied the model to Tanzania. The causal relationships included in the new model were obtained from previously published papers and publicly available data. The main numerical data sources used were the World Bank and International Energy Agency.

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Published: 2017-10-16


Collste, D., Pedercini, M. and Cornell, S.E. 2017. Policy coherence to achieve the SDGs: using integrated simulation models to assess effective policies. Sustainability Science

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David Collste is a Marie Curie PhD Fellow studying integrated assessment tools and modeling for global sustainability within the "Adaptation to a New Economic Reality" project.

Sarah Cornell works on global sustainability issues, coordinating the centre’s research and international collaborations on the planetary boundaries framework.