With wind as the standard bearer

RESEARCH | RENEWABLE ENERGY

By Morten Andersen

According to legend, Denmark got its red and white national flag when it fell from the sky during a battle in Estonia in 1219. It aerial arrival was seen as a sign of divine support, and the Danes duly triumphed. If something similar happened today, Danes would probably regard the fluttering flag as an indicator of unusual wind conditions, and send a team of technicians to calculate the economics of building a wind farm there!

At Risø DTU, the National Laboratory for Sustainable Energy, researchers can calculate wind resources at most localities in the world 20 years ahead in time with an accuracy of ±5 per cent. These calculations are crucial in persuading investors to breeze down to the bank and borrow the money to build a wind farm. Danish research organisations have over half of the world market for wind software and have set the de facto standard that everyone in the industry uses. At the same time they continuously improve their methods to further increase accuracy and cover more geographical areas.

The example shows that although Denmark leads the world in the wind industry, there are certainly no signs of easing up on the intensity of research. On the contrary, more research is being conducted than ever before – but the areas of research have changed.

“Since power production from wind fluctuates, and since we do not have an efficient way of storing the energy, imbalances between production and consumption will inevitably occur. You can get around this through agreements with foreign countries, but it would be a lot more expedient also to activate the resources that are integrated in the electricity grid,” says Professor Jacob Østergaard of the Centre for Electric Technology at the Technical University of Denmark.

Electric cars help wind power

Jacob Østergaard heads a major research project on the Danish island of Bornholm. The island, which is home to about 1 per cent of Denmark’s 5.5 million population, has been chosen both for its manageable size and the fact that a third of its electricity already comes from wind power. Bornholm today resembles how Denmark as a whole could be in a few years, following the political decision that wind power will account for 50 per cent of Danish electricity consumption.

This year and in 2010, an intelligent electricity system – professionals use the expression “Smart Grid” – will be designed for Bornholm. In 2011, the system will be implemented on the island, which will at the same time be supplied with electric cars sourced from abroad. The interesting thing about the test is not the cars, but how they will affect the electricity system.

Why does the combination of wind power and electric cars require that the electricity system becomes intelligent? Consumers will typically charge their cars when they come home from work, thus adding further to the peak consumption that occurs when families switch on lights, the TV and electric cookers. So the system must be designed in such a way that the charging station at the consumer’s home is able to draw electricity in the middle of the night at times when there is plenty of inexpensive wind-generated electricity available.

The test will also be valid for other energy sources than wind – for example solar cells, where energy production varies depending on natural conditions.

“Denmark will probably be the first country in the world to solve this type of problem on such a large scale. As more countries expand their wind power, solar cell systems and similar energy sources, the experience gained in Denmark will become increasingly more interesting to the world,” foresees Jacob Østergaard.

Illustration: Lars Chrois

Turning wind into synthetic fuel

The Danish researchers do not think however that an intelligent electricity system can solve all the problems by itself. At Risø DTU, they are working on a new concept which can exploit surplus electricity from wind turbines. Using electrolysis it is possible to split the water molecule, which consists of two hydrogen atoms and one oxygen atom. Both hydrogen and oxygen are useful, but in an energy context hydrogen is particularly interesting. It can for example be exploited in a fuel cell, which can be used to run a car or function as a mini power plant for a house. And there are no emissions of CO2 or other greenhouse gases when hydrogen is used as fuel.

What is new is that hydrogen can be produced a lot more efficiently by carrying out the electrolysis at high temperatures. This is only possible using electrolysis cells of predominantly ceramic materials – a technology very much inspired by the development of Solid Oxide Fuel Cells (SOFC), on which Risø DTU has long collaborated with Danish company Topsoe Fuel Cell. Simply stated, an electrolysis cell is a fuel cell running in reverse. Whereas a fuel cell produces electricity and water from a chemical reaction between oxygen and hydrogen, the opposite happens with electrolysis. The type of electrolysis which Risø DTU is studying involves a mixture of hydrogen and carbon monoxide called synthesis gas, which can be used to produce methanol as a synthetic fuel for internal combustion engines.

“So it is a way to produce synthetic fuel for example for the transport sector where it can replace fossil fuels,” says the head of the programme, Professor Søren Linderoth. “It is very attractive to be able to exploit electricity from renewable energy sources as fuel for cars. Everything suggests that electrolysis will gain ground. At the same time we know that high temperature electrolysis is more efficient than electrolysis at ambient temperature.”

Sugar beet makes a comeback

An extra benefit of producing hydrogen from the electrolysis of water is that oxygen is formed as a by-product. The oxygen can for example be used in an integrated energy system, where gasification of bio-mass also forms part. Gasification requires oxygen, which is normally obtained from the air. But along with the oxygen in the air comes 80 per cent nitrogen. That is dead weight when air is pumped round in the system. Higher energy efficiency is achieved using pure oxygen instead.

Biogas is also a Danish speciality. At research centre Foulum in mid-Jutland, the Faculty of Agricultural Sciences under the University of Aarhus is running one of the world’s largest experimental biogas facilities. Along with other partners in a project, they are experimenting with sugar beet, where energy and agricultural production are studied from a completely new angle. The basic idea is that the beet is initiall pressed by a simple mechanical process to extract a sugary juice which can be converted into bioethanol by fermentation. Bioethanol is in demand on the world market as a climate-friendly and renewable energy source. Remaining after the pressing is a mush – a pulp – which can be used as cattle feed.

Globe Ale is Denmark’s first CO2 neutral beer, brewed to celebrate Nørrebro Bryghus in Copenhagen becoming the country’s first CO2 neutral brewery.

“In our experiments we have achieved outputs of up to 26 tons of dry matter per hectare. In comparison, you get at best 15-18 tons of dry matter per hectare when you grow maize. Sugar beet is therefore a more effective crop, that is when you focus on combined production of feed and biomass for energy purposes,” says project manager Karl Martin Schelde of CBMI in Agro Business Park, which is located next to the Faculty of Agricultural Sciences under the University of Aarhus. In addition to forming part of the solution to climate problems, this production will also be attractive to many Danish farmers, opines Karl Martin Schelde:

“Until a few years ago, sugar beet represented a large proportion of Danish agricultural production. Now beet is largely outperformed by especially maize, but Danish farmers still have major know-how in growing beet. So for them it just a matter of pressing the “play” button, when our experiments show that you can achieve good economics by growing beet for combined use as a feed and energy crop.”