GREEN WALLS

They are smaller than a strand of hair, yet they hold much promise for the future of energy generation. Scientists from Hamburg are researching how microalgae can be used to provide households with heat and electricity.

By Sarah Schultes

They may look like indistinct green goo, but to Dieter Hanelt they are endlessly fascinating: algae.

A windowless room with glossy white walls and bright clinical lights houses a collection of 500 glass flasks. Densely packed together across four levels of metal shelving, they are arranged chronologically. The contents’ dates of origin are written clearly on the sides. Order is of paramount importance here, and no one is allowed to rearrange these flasks. The three centimetres of liquid they contain may well constitute the energy supply of the future.

This precious algae collection is housed at Biozentrum Klein Flottbek, part of the University of Hamburg. This is where Dieter Hanelt, Professor of Cell Biology and Phycology, is investigating the aquatic plants. The biologist is fascinated by algae. When he peers into the microscope, he looks past the disgusting pond slime that most of us would see – his vision is one of crystalline flakes and feathery shapes. Hanelt’s aim is to cultivate algae in order to turn them into biomass. One of the uses for this biomass will be power generation. This would make algae a viable “green” energy source, joining the ranks of wind and solar power.

Hanelt has identified the tiny organisms’ unique talent: With the help of sunlight, they can generate much more energy than other plants. Trees, for example, have trunks and branches, and photosynthesis is restricted to the leaves they carry. Algae, on the other hand, are single-cell organisms, and each and every one of those cells uses photosynthesis to convert sunlight into energy. What the algae do with this energy, among other things, is multiply. Algal cells divide up to twice per day. This is exactly what Hanelt wants – his aim is to grow as many algae as possible. Once harvested, the algal biomass can be used as a raw material in biogas plants. This makes it interesting for researchers and energy providers alike.

Is this the energy of the future?

As a result, the City of Hamburg and E.ON Hanse AG are currently funding research into open-air algae cultivation. A field in Reitbrook, just outside Hamburg, has been home to a pilot plant for algal bioreactors since 2008. Here, green panels line up, facing the sun. The flat plastic containers may look a lot like solar panels, but instead of silicon, they contain microalgae, sourced directly from Hanelt’s lab. The algal solution is suspended in ordinary tap water, enriched with CO2 and other nutrients. A jet of air bubbles is injected at regular intervals to whirl the mixture around. The pilot plant is owned by Martin Kerner, a biologist and business consultant. Kerner is aiming to grow algae on a large scale and turn them into a profitable venture. To speed up the process, he has enlisted the help of researchers at universities across northern Germany, including Professor Hanelt, and launched the TERM project (Technologien zur Erschließung der Ressource Mikroalgen / Technologies for Exploring Microalgae as a Natural Resource). Kerner tries out the results of this collected expertise at his pilot plant in Reitbrook. “We strive to harvest the greatest amount of algae using as little energy as possible,” says Kerner, watching as the viscous liquid drips from a pipe labelled “Harvested Biomass”.

There are inherent problems to growing algae in direct sunlight. In the sun, the thick green fluid reacts much like a black car – it gets too hot. This is very dangerous for the micro-organisms, as they perish in temperatures above 60 °C. To prevent this, Kerner needs to cool the algal biomass. As he explains, however, this consumes energy: “And, at the same time, we are wasting heat that could be redirected for human use.” Kerner’s idea is to deploy the heated-up microalgae in a meaningful way, by supplying an entire building with heat.

Kerner will present his innovations on a grand scale as part of the IBA building exhibition in Hamburg. In March 2013, Kerner’s algae will be used here to provide heating for a pilot apartment block. The structural work has already been completed, and now Kerner is working on the site, overseeing the installation of the bioreactor. Glass panels a storey high, housing 200 m² of circulating algae, are to be attached to the façade, forming a kind of living skin for the building. Much like a solar thermal system, the warm algal mass is used to heat up the cold water inside the building. This is done using a heat exchanger – the water gets warmer while the algae are cooled down. “It’s a symbiotic relationship between the algae and the house,” enthuses Kerner. The green mass warms the water up to 40 °C so it can be used for central heating or hot water. In winter, the heat is thermally stored underground, and any excess heat can be diverted into the district heating grid.

The building, which is valued at around €5 million, is one of the most spectacular construction projects at the IBA. The bubbling façade serves to protect against light, cold weather and noise – and it looks pretty impressive, too! The algae come in a range of luminous green hues, and the bubbles travel at different speeds, creating shifting patterns across the façade. The 15 apartments contained within are already highly sought-after. According to building contractor Otto Wulf, 35 parties have registered an interest in moving in once the exhibition has finished.

Business-savvy biologist: Martin Kerner at his pilot plant for algal bioreactors

For Kerner, the heat generated by the algae may be useful, but it is still just a side effect. His overriding goal is to generate biomass. Kerner wants to harvest the micro-organisms from the panels on the building exterior and then process the resulting biomass in the basement. The algae can accumulate enough energy to fuel a biogas digester. This creates methane gas with an energy efficiency of 70 to 80 percent. Mineral coal, by comparison, only has around half that energy efficiency. What Kerner foresees for the future is independently operated bio-power plants in residential basements. The machine he envisions will convert algal biomass, household waste and faecal matter into hydrogen and methane. An accompanying fuel cell in the basement would then generate electricity directly in-house.

Not only are algae a very clean energy resource, in the future they could also contribute to cleansing the air. After all, the main substance that microalgae feed on is climate-damaging CO2, large volumes of which are being emitted into the air by coal-fired power stations, among many other things. Kerner is already feeding the algae in his Reitbrook pilot plant with waste gas from a gas-fired combined heat and power station. But if this makes you think that the best idea might be to connect algal bioreactors to coal-fired power plants to absorb all their CO2 emissions, think again. Researcher Dieter Hanelt knows better: “Taking on all the CO2 coming from a medium-size 500-megawatt power plant would require algal reactors with a surface area of around 350 km²,” he warns – that’s roughly half the size of Hamburg.

 

Algae: The energy supply of the future? (English subtitles)

Sarah Schultes takes a closer look at the great green hope of the switch to renewables.