All things environmental

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

Bremen’s Café Ambiente

with one comment

Bremen and its musicians

Bremen and its musicians

A donkey, a dog, a cat and a rooster decide to go to Bremen to make a living as musicians. They chance upon a robbers’ house, deep in the forest, and make such a racket with their “music” that they scare the robbers away. They stay in the house happily ever after. They never make it to Bremen.

That’s pretty much all I knew about Bremen before going there on a day trip from Hamburg.

Bremen is a very pretty city with a core of intact medieval buildings. My guidebook mentioned Café Ambiente as something to visit if interested in renewable energy. They serve beer; we went.

Even in Germany, there used to be women’s groups advocating for the prohibition of alcohol. The building that now houses Café Ambiente was built in 1929 as a home for the movement. A terrasse was added in 1957 (so guests could enjoy their coffee outdoors in summer). But the place fell on hard times as abstinence didn’t fit with post-war Germany and the city bought the place in 1984. In its gorgeous setting on the river shore, the renamed Café Ambiente is known locally as a “literature café” because of its readings by famous authors.


Starting in 1997, the Ministry of the Environment of Bremen chose this café for an energy concept project – a showcase for energy management in the hospitality sector. The change most obvious to customers are the solar cells on the terrasse’s glass roof (also called winter-garden). These produce a nice dappled shade effect, and, of course, a fair bit of power: nine kilowatts during sunny periods. But retrofitting a building that has historical significance isn’t easy: according to the website PV Database,

The PV-System is nicely integrated into the double glazed roof construction of the winter-garden. In total 159 semitransparent PV-Modules are used with a light transmission rate of 45% each. Due to the round shape of the winter-garden it was necessary to produce 20 different size and shapes of PV-modules. The custom made glass-glass PV-modules encapsulate 7270 polycrystalline cells with a total power output of 9,5kWp. The estimated energy output is 5000 kWh per year.

But the €930,000 renos weren’t just about the solar deck; the structure was also fully insulated to modern (German) standards, and that includes all the glass in the covered terrasse.

The kitchen underwent a complete overhaul. Restaurant kitchens have huge energy demands for cooking and refrigeration, which can account to half of a restaurant’s energy bill. The first and obvious step was to fully separate the cold (coolers and freezers) and hot areas (ovens, grills, etc) of the kitchen without impeding the chefs’ movements. In the hot area Café Ambiente is equipped with a pizza oven, a steamer, two ovens, a hot plate and a grill, all using natural gas. These new appliances are state-of-the-art energy efficient, of course; but what makes the real difference is the induction fume hood, which is coupled with a heat exchanger for heat recovery.

The solar cells integrated into the glass roof

The solar cells integrated into the glass roof

In the seating area of a restaurant fresh air must be constantly brought in, so that there are no stagnant odors, to a rate of at least 15 air changes per hour. (To picture what that means in terms of energy needs, imagine completely replacing all the warm air in a room with cold air from outside – and doing that fifteen times every hour.) The kitchen itself produces smells, smoke and heat and requires a lot of fresh air, 30 to 50 air changes per hour.

This is where the heat exchanger comes in: the incoming cold air from outdoors is heated by the exhaust, so as to recover as much heat as possible. This is now a common feature of energy-efficient PassivHaus but is far less common in restaurants, given the size of the heat exchanger required. To ensure that the ventilation rate reflects how busy the restaurant is, an indoor air CO2 meter is used, so that only as much fresh air as needed is brought in (the more people inside, the higher the CO2). As a result the heating energy required to keep the restaurant warm is reduced by between 50 and 80%; think of it as recycling the heat from the ovens to keep the rooms warm.

Heat exchangers are also used to reduce the energy needed to heat the water for washing and dishwashing, which is stored in two separate tanks, again for saving energy. Add to that energy efficient lighting, and the overall yearly savings in avoided CO2 emissions are about 30 tonnes per year.

Every chef's dream...

Every chef’s dream…

Which may not seem like a lot, overall; the EPA uses a figure of 4.7 tonnes of CO2 per year for one average car. Still, here is one single restaurant that has managed to reduce its emissions to the equivalent of six fewer cars.

More details and many photos can be found in the brochure entitled “Environmentally-friendly gastronomy” (Umweltfreundliche Gastronomie, in German only), which also describe the energy upgrades of Café Sand across the Weser River; or on the site of the State of Bremen’s electricity company, Energie-Konsens (also in German only, alas).


Written by enviropaul

August 29, 2015 at 12:42 am

One Response

Subscribe to comments with RSS.

  1. […] from Café Ambiente, there’s another little renewable energy marvel in Bremen: a football stadium covered in PV […]

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: