All things environmental

Musings about the environment and all it touches, from education to city planning

Thermal solar in Hamburg

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Some of the rowhouses of SolarSiedlung

Solar thermal is kinda old-fashioned, isn’t it? Making electricity with photovoltaics, now that’s something. But just getting hot air or water to accumulate in a black-painted collector, isn’t that a bit, uh, you know…too simple?

I was taking a walk in the Bramfeld area of Hamburg, looking for a development called SolarSiedlung. Some pictures I’d seen showed large arrays of solar collectors. Once I got there I thought: hmm, these are funny looking PVs…wait, don’t tell me! These are just flat thermals!

Okay, so you have to be a nerd to understand my disappointment. Unless you’re making electricity with concentrating mirrors, solar thermal, especially with flat panels, seems kinda obsolete – or so I thought.

The complex, which houses 124 families, is located in a gorgeous area in the outer Hamburg, full of trees. It consists of a group of rowhouses with a few appartment blocks, decked in large south-facing panels. There is a nice creek nearby and more than a few healthy-looking green roofs, but the whole thing has otherwise a suburban, ordinary look; it’s a far cry from the hippy colony the name Solar Sieldung (Solar Settlement) conjures.

The main problem with solar thermal, of course, is availability. In summer, when the sun shines during these long days, you don’t really need the heat; and where’s the sun in winter? For the system to be practical, some way of storing the summer heat is needed.

The storage tank

The storage tank

This is what is special about SolarSiedlung. Across the path is a strange circular structure, low and squat, capped with (what else) a green roof. It’s the key to the whole complex: a 4500 m3 tank, mostly buried, filled with warm water to provide thermal storage for the whole complex. The complex was completed in 1998, the first of its kind in Germany. The solar heat collection and storage was priced at 125 Euros per square meter (of floor area), accounting for 7% of the construction cost. The system was meant to pay for itself within 15 years.

The design called for half of the heating needs of the complex to be provided by solar energy, the rest from natural gas. But half is enough to avoid producing 170 tonnes of CO2 per year.

So how did it do? From what I could gather, the system didn’t completely meet the objectives, providing only 40% of the heating needs. And the 30-year design life may have been a bit over-estimated, too; one of the townhouses was getting its roof insulation replaced, meaning the collectors had to be removed temporarily.

But still, that shouldn’t be construed as a failure, far from it. When it was built, it was a pioneering system, and valuable lessons can be drawn from its performance. (That’s the nice thing about looking at German energy systems: many that would be considered newfangled in Canada have been operating for years here.) And, at least for this one, performance has been monitored over time.IMG_6178

In fact, the Fraunhofer Institute recently published its findings about solar active houses, the category under which the Hamburg complex falls. The research institute found that these systems, across the country, perform rather well in general – possibly because they are simple to design, install and operate. The general findings of the study that looked at individual houses showed that 40 m2 of collector, and a 5000 liter storage tank, are enough to provide 60% of the heat required for a single family home under German conditions.

The report deplored the fact that such systems are poorly appreciated, compared to their sexy solar cousins, the photovoltaics, precisely because there had been until now little research on them. So this is a positive step – especially considering that these systems would work just fine in BC, too.


Some info about Hamburg’s SolarSiedlung:
14,770 m2 of floor space, built between 1996 and 1998, on Carstens Reimers Ring in the Bramfeld neighbourhood.
3000 m2 of solar panels, design capacity of 267 kWh/m2-yr, at a peak thermal power of 2 megawatts, and 60C maximum water temperature for storage.
Heating requirements 70 kWh/m2-yr, 1600 MWhr/yr total; half provided by solar energy, the rest by natural gas.

Complex overview.  Dark blue: solar collectors; pink: buildings.

Complex overview. Dark blue: solar collectors; pink: buildings.


Written by enviropaul

September 15, 2015 at 8:11 am

2 Responses

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  1. […] above elevated, despite their name (U-bahn stands for “underground railway”). On my way to the Solar Siedlung I saw from the train window a cool house at Hoheneichen station. I stopped on the way back to check […]

  2. […] summer, uses it during the cold season.  This provides 40% of the heating needs of 104 apartments, similar to another development in Hamburg that I described earlier; the key difference is that Hamburg’s uses hot air instead of hot water, but the performance is […]

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