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Energy in pictures

05 April 2016

Science nowadays isn’t just about producing data: making sense of publicly available ‘Big Data’ can be equally important. Chris Davis from the Energy and Sustainability Research Institute Groningen used some 1.5 million data points describing electricity generation in all US states to assess the likely impact of the new Clean Power Plan, a policy aimed at reducing carbon dioxide emissions in the US.

The Clean Power Plan (CPP) sets a limit on greenhouse gas carbon dioxide emissions by the US power sector. ‘Unlike Europe, the US had no national policy for capping emissions in this sector’, explains Chris Davis. Different states have different policies, but this will change with the introduction of the CPP.

Chris Davis
Chris Davis

As Assistant Professor of Energy Informatics and Modelling, Davis creates tools to make sense of large and often public datasets from the energy sector. For this research he mined public records on energy production in all US states between 2001 and 2014. ‘I wanted to create a sort of map, to show people what is going on.’

The resultant paper is already available online and will be published by the journal Renewable and Sustainable Energy Reviews in July. It shows that carbon dioxide emissions are already falling. ‘President Obama initiated the CPP, and he can take the credit for setting things in motion’, he smiles.


Davis’s analysis reveals other interesting details. For instance, one of the main drivers of the ‘de-carbonization’ of energy production is the increased use of natural gas, generally shale gas produced by the controversial fracking method. ‘There is a shift from coal to gas, and burning gas produces half the carbon dioxide that coal does.’

In his paper, Davis shows how much energy each state produces from different sources such as nuclear, coal, gas, wind, hydro and solar. The resulting set of pictures is complicated. ‘Interestingly, wind is on the rise in some conservative states. That’s because farmers have discovered they can make extra money by installing wind turbines.’ The shift to wind is increasingly driven by economics, rather than environmental concerns.

Coal export from Wyoming | Illustration Chris Davis
Coal export from Wyoming | Illustration Chris Davis

Davis also noted that a state like Iowa, where wind energy is rising steeply, hasn’t shut down its coal plants. ‘These now export energy to other states. This is because it is more economically efficient to run a coal plant continuously than to vary its generation in response to wind conditions.’ Likewise, green energy is on the rise in Wyoming, but this state remains the largest producer of coal, providing 38 percent of coal used in the US electricity sector.

On the whole, clean energy from wind, solar and hydro is on the rise, and has been for over a decade. Even without the CPP, carbon emissions are dropping. ‘But not everywhere’, says Davis. As the CPP aims to reduce carbon dioxide emissions by 32 percent from 2005 levels by the year 2030 in all states, it will have an impact.

Davis shows another figure from his paper: the drop in emissions that the CPP requires by state. Many states could reach their target by switching from coal to shale gas. The big question, however, is how much gas is left. ‘If shale gas production goes down, we have a problem.’ But sustainable sources are on the rise, and there is plenty room for improvement. ‘The entire offshore wind capacity in the US is currently one turbine, with a generating capacity of 20 kilowatts’, says Davis. A typical large wind turbine in the Netherlands is about 75 to 100 times larger.

Many more interesting observations can be made from Davis’s pictures of the US energy market. ‘I wanted to map the complexity, so you can stare at it for a while and see the personality of the different states.’ The graphs also show variation during the year. Some states produce almost 100 percent renewable energy at times. ‘But wind, solar and meltwater for hydroelectric plants are often seasonal, so achieving 100 percent renewable production all year round is impossible without storage or imports from other states.’ Energy demand can be seasonal too: the pictures show a clear spike in electricity consumption during the summer in states like Texas. ‘That’s largely due to air-conditioning.’

Davis’s analysis is unique. Although all the data is public, no one has ever transformed it into such a visual overview. ‘This sort of work presents the big picture, and many such data sources are underused.’ He shows a short video clip of his in which yellow lights appear all over Germany. ‘Photovoltaic units are registered by postcode when installed’, he explains. ‘So it’s very easy to visualize the increase in solar power, in this case between 2009 and 2015.’

This is exemplary of Davis’s work. ‘One of my Master’s students extracted power stations and power cables from OpenStreetMap and captured the data in such a way that it fills in gaps in official data sources and can be used for simulations of the power grid. This can show how the power grid operates, and what is needed to stabilize it, given increased amounts of generation from renewables.’ There is a goldmine of information out there for energy researchers.

Last modified:03 November 2017 2.30 p.m.
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