Wind turbines on a hillside in California; Wind turbines on a hillside in California;

Energy and scale

What is the right scale for designing our future energy systems?

The present global energy mix is dominated by fossil fuels. In 2008 they met about 81% of the global primary supply, according to a 2010 International Energy Agency estimate. We are all aware that the burning of fossil fuels pollutes. Scientific consensus is clear that this pollution causes climate change. It is therefore imperative for our future that we find cost effective ways to meet our global energy requirements, without polluting the environment.

Reducing energy demand is cost effective, however, big change will require replacing polluting energy supply with clean energy alternatives. There are many technologies vying for market share, from solar panels to giant hydroelectric dams and – depending on your definition of clean – you might include nuclear.

In my experience, the engineering design process has limited scope for investigating the cost benefit of national scale energy systems. Project analysis tends to answer questions such as: what is the most cost effective, reliable route to run pipes from the platform to the refinery? Or, how can we supply the school’s energy demand with onsite renewables?

On a national scale the parameters are very different. In Norway, for example, there is huge national hydroelectric capacity. In the Middle East and North Africa (MENA) there is a lot of sun and flat land, so solar is much more cost effective there than in cloudy climates. In the UK, hilly and coastal areas have a great wind resource. But that doesn’t mean that there is necessarily enough to meet our energy requirements.

We need to know how much is needed to meet 100% of energy demand. How much land is required and what are the costs? In the UK, David Mackay has done a lot of the work for us. In his book Sustainable Energy Without the Hot Air, he presents the constraints in easy to understand diagrams. He concludes with Five Energy Plans for Britain, for 2050. In these possible plans, wind power could, in theory, provide up to 45% of annual energy demand.

But what about the remaining 55%? According to Mackay’s analysis of the limitations, other renewable contributions are likely to be much lower: 1% solar hot water, 5% tidal power, 4% local solar PV, 4% wave power ,7% biomass, 3% biofuels, 2% waste to energy and 0.3% for hydroelectricity. The UK’s remaining clean energy options, identified by Mackay, are: “clean coal”, nuclear and solar energy from deserts.

The energy from deserts concept, promoted by the DESERTEC Industrial Initiative (Dii), aims to solve Europe’s energy problems, at a multinational scale, by purchasing electricity from MENA nations thousands of kilometres away.

In my experience, energy systems design generally focuses on cost effective local solutions. Energy purchasing from distant deserts is not (yet) a possibility. Considering the scale of global pollution and the reality of limited local renewable resources, I think we should design at a scale that includes desert sunshine in our future energy mix.