Truls Norby i laboratoriet

Thermoelectric materials can generate electric current completely without the use of moving parts. This reduces the need for maintenance, explains Professor Truls Norby. Photo: Ola Sæther, UiO

Magical materials creating electrical power from waste heat

Thermoelectric materials have scary names like cobalt phosphide, zinkantimonide and lead telluride, signaling that they are quite toxic. However, they also contain an almost magic ability: They can exploit differences in temperature to create electric power.

The coming four years, the University of Oslo is spending NOK 100 millions on a big innovation project. The project will be organized in two innovation clusters.

Professor Truls Norby at the Department of Chemistry is in charge of one of the clusters. They are going to use thermoelectric materials to exploit the waste heat from smelters and other processes that involve a lot of heat in industry or for example exhaust systems in cars.

Flytende metall i et smelteverk

Thermoelectric materials are almost magical: If a panel or module containing a couple of these kind of materials are placed in a temperature gradient, where the opposite parts of the panel have different temperatures, the panel will start producing electrical power.

The opposite is also possible: If an electrical current is sent in to a thermoelectric panel, it will cool down at one end and heat ut at the other end.

Long lasting and minimal maintenance

– Thermoelectric materials can be used to produce electric power in a temperature gradient completely without the use of turbines or pumps. Consequently, panels made by these materials can be used for a number of years, and the cost of maintenance will be minimal, explains Truls Norby.

However, in spite of these clear advantages, thermoelectric materials are not much used today.

If you have a modern car with a cooling system in the glove comdepartment, there might be a little Peltier element inside based on thermoelectric cooling. Nevertheless, the extensive usage is not yet happening because the materials have a few disadvantages:

– Thermoelectric materials have a tendency to be toxic. Additionally, they are not very effective, meaning that they at best can transform 10 percent of the supplied heat energy to electric power. We are in all practicality talking about a mere 1-2 percent.

– However, in large scale industrial processes a few percent’s effectiveness can mean a lot of money, explains Nordby.

Small footprints gives competitive advantage

The Innovation Cluster called “Thermoelectric materials for use in industrial applications” consists of Truls Nordby and other professors at UiO, four PhD’s and several industrial partners of varying size.

Among the really large partners we find industrial giants such as Norsk Hydro and Elkem. They are interested in using thermoelectric materials in several of their factory plants, in order to create electric power from their waste heat.

– The big companies are good at using waste heat for direct heating and heat recycling, but there is still a lot of waste heat that just disappear.  However, a lot of companies have realized the competitive advantage of being able to offer products with a lower CO2 or energy footprint than their competitors.

– Consequently, being able to put some of the waste heat back in to the industrial process is considered a very interesting possibility. This is also a technology that can be suited for cement factories, according to Norby.

He thinks the Innovation Cluster will go far in developing panels that can be placed outside oven smelters and heated gas pipes. Here the panels can produce electricity created by the differences in heat between the smelters and the surrounding environment.

Professor Truls Norby

Professor Truls Norby is in charge of a so called innovation Cluster.

– It is important to find solutions that don’t complicate the production plant or creates downtime during the industrial process, Norby points out.

Metalloids and skutterudites

There exists a lot of different thermoelectric materials. The most efficient ones can’t handle very high temperatures and don’t last very long, in addition to being very toxic.

– The less effective materials, however, are more resistant to high temperatures and lasts longer, they are even less toxic. This is an interesting dilemma for a scientist, thinks Norby.

Many thermoelectric materials consists of so called metalloids – like phosphorus, antimony and tellurium – in combination with cobalt and other transition metals.

– We have some favorites among these materials like cobalt phosphide, zinkantimonid and lead telluride. You can almost just by hearing their names conclude that these materials are not something you want in your daily tea cup. As a consequence we take the HSE-work when working with these materials very seriously, explains Norby.

A special class of these materials is called skutterudites and has been named after the Norwegian farm Skuterud, a farm close to the industrial museum Blaafarverket at Modum, about one hour's drive from Oslo.

The skutterudites contain a lot of cobalt, which was also the basis for the production of glass at Blaafarveverket – and the Skuterud farm have developed into a pilgrimage site for international scientists interested in skutterudites.

– At Skuterud they are so fed up with Japanese scientists taking selfies in the driveway that they have put up a “Keep out”-sign, tells Norby.

The other class of thermoelectric materials consists of oxides, that are more stable and can withstand higher temperatures in an oxygen rich atmosphere. Norby admits that the development of the oxide materials hasn’t yet reached as far as the phosphides, antimonides and tellurides.

Not from scratch

– This is an innovation cluster and that means that we’re not starting from scratch. We will instead work with the materials that already exist and try building modules that make them effective for the industry, Norby explains.

One of the smaller industrial partners in the cluster is Cerpotech based at Heimdal outside Trondheim. They produce and deliver thermoelectric materials in powder form.

The scientist at UiO will also cooperate with the Kristiansand based firm Tegma. They have estimated that 60 percent of the worlds primary production of energy is lost as waste heat. Tegma is a startup company that is concentrating on development and production of thermoelectric modules. One of their founders is the chemist and innovationist Alf Bjørseth, who previously have been successful with the production of solar panels in Norway.

Norby has co-founded two companies and in 2012 he received the University of Oslo’s award for innovation. However, he is still suitably modest on his own behalf.

– After winning the innovation award I learned that I didn’t know enough about what innovation really is. But I certainly know that there is a long way from invention to practical use.

– An innovator does not have to be an inventor. It is just as important to be a facilitator, one that can hold all the threads, or one that knows what the market didn’t know that it needed. And it’s obvious that innovation is a lot about hard work. It is also about never giving up and – I’m sorry to say – not being naive, says Norby.

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Professor Truls Norby, Department of Chemistry at University of Oslo