Wetenschap - 12 mei 2011

Designing with energy in mind

What would a landscape in which energy was used as efficiently as possible look like? The person to ask is Sven Stremke, who designs 'sustainable energy landscapes'.

Landscape architect Sven Stremke is a pioneer in the new field of energy-oriented design in landscape architecture and spatial planning. Not many people are familiar with the term 'energy landscape'. 'And yet there is nothing new under the sun', explains Stremke. 'Just look at the kinderdijk. That is actually a sustainable energy landscape. It is even a Unesco monument. Energy generation has always been a feature of the landscape.'
In Stremke's approach to design, everything revolves around energy. To put it more precisely: exergy, a thermodynamics term for available energy. In other words, energy you can harness and do something with. During work processes, exergy gets lost and turns into entropy. 'So you go from a situation in which you have high-value energy to one with low-value energy. That is not a problem in itself. Everything is entropic. The problem is the scale of it and the speed at which it happens.'

Matching supply and demand
And here we get to the heart of exergy-conscious thinking. We throw away too much available energy. We use energy in the wrong way and it could be managed much
more sustainably. Not just by using renewable energy sources such as wind, water, geothermal heat and biomass. But also by making more efficient use of the available energy so as to lose as little exergy as possible.
Just look at nature, says Stremke. 'The flow of energy in nature is always optimized. A highly developed ecosystem destroys much less exergy than does a less developed one. An ecosystem always seeks to hold on to as much energy as it can. And that is something measurable.'
Conventional thinking about energy focuses too much on quantity, says Stremke. A mistake. 'You should not look only at the total amount of energy needed for a year, but also at when, where and how it is needed. This means thinking in terms of energy quality, time and place.' For example? Stremke: 'In Germany, I see that they are generating biogas using a fermenter. This is then connected to a thermal power plant to generate electricity and heat. It works all year round. But in the summer nobody buys the heat, so that is suboptimal. It would be much better to store the biogas and use it when it is really needed. By doing that you would double the efficiency of the system.' 

Optimizing the flow of energy
On a smaller scale, in architecture and industry, this switch towards linking supply and demand is already being made in some places. And Stremke is upscaling these efforts to landscape level, to create the energy landscapes mentioned above. An example is the the peat colonies in Drenthe, a district which has set itself the goal of being energy-neutral within a few decades. This means a sustainable balance between energy consumption and local supply. Stremke and his colleagues were invited on board to show whether and how this could be done.      
The working method is simple. Stremke first maps out all the possible sources of energy. 'I look at what is technically possible in the area in terms of sustainable energy using wind, water, geothermal heat, solar power, seasonal thermal storage, biomass and residual heat from industrial processes. Then we get a picture of the demand: who uses what, where and at what times, and what are the existing networks (for gas, electricity etc.).' The third stage is to link up demand and supply as smartly as possible within the inevitable limitations. Because you cannot just install a wind turbine in the middle of a conservation area for birds or of a forest.

Residual heat for housing estates
Making smart linkages is the crux of the matter, according to Stremke. For example, he developed a system for supplying large areas of the town of Emmen with heat from a single residue source. 'Older neighbourhoods take more heating than the newer ones, because the houses are not as well insulated. To heat up an old farmhouse in the winter you need water heated to between 70 and 80 degrees. But for a new Vinex housing estate, water heated to 30 degrees will suffice. By having the water flow from the older to the newer neighbourhoods, you get more use out of one residue flow.'
The peat colonies are not an isolated case. Stremke designed an energy landscape along similar lines for South Limburg and is now working on an assignment for four municipalities in the north of Overijssel. There is no shortage of work, he says. His students are now working on drawings of an energy-neutral future for the islands of South Holland (see box: energy island). There is no question about this being possible, says Stremke. 'In the countryside you could make the whole of the Netherlands energy-neutral. I am convinced of that. It only gets more difficult in places with more industry. But it is always possible.'

Energy islands
The South Holland islands of Goeree-Overflakkee and Schouwen Duiveland want to be totally energy-neutral within one generation from now. Wageningen Master's students are giving them a hand. A total of 65 students at the Landscape Architecture and Planning Studio have been working since February on their ideas for the islands. They presented their work two weeks ago in the Forum. Windmills, solar panels and biomass will have to produce the goods in future, according to the students. Besides electric vehicles and a light rail system linking the islands to the cities of the Randstad. One striking idea was to fill the natural sand banks along the islands' coasts with solar panels. The students would situate wind turbines offshore, where they would be out of sight for tourists and would not occupy any land. They are also good from the point of view of thermodynamics. According to the authority on this matter, Stremke, electricity is the most valuable source of energy, as very little of it gets lost during transportation. It is very different for biofuels. Stremke: 'Transporting bio-ethanol, for example, by road takes a lot of energy. So you should use this kind of energy as close as possible to the source. As a general rule, the lower value your energy form, the shorter the distance to the user should be. For instance, geothermal heat should be used on the spot; otherwise there is no point having it.' 
Over the coming weeks the students will be translating their vision into concrete projects. The project should be finished at the end of this month.