Flat-Plate Collectors and Heat Buffer Tanks in Brewing Processes

The Hütt-Brauerei Bettenhäuser GmbH & Co KG is a mid-sized private brewery in the Kassel region. The brewery is family-owned in 9th generation and has been brewing beer since 1752. The production site is the so-called Knallhütte in Baunatal. Currently Hütt employs about 45 people who brew around 60,000 hl of beer each year. Additionally, little less than 10,000 hl of non-alcoholic beverages are produced yearly. That makes for a total sales volume of roughly 8 million € per year. Part of their heat-demand od the brewing process is delivered by flat-plate collectors combined with a heat storage.

The production process requires about 4 GWh/a of heat, which is supplied by a gas-heated steam boiler. In order to reduce the use of fossil fuels as well as the energy costs, the Hütt brewery chose to build a solar process heat plant as part of a project funded by the German Federal Ministry for the Environment and realised by the University of Kassel.

The energy concept for the brew-house included a renewal of the production machinery. The formerly atmospheric wort boiling has been replaced by a vacuum-boiling process, which can be operated at lower temperatures. Furthermore, the brew-house’s heat recovery has been improved.

Twenty-two rooftop-integrated flat-plate collectors with an area of 7.69 m2 each have been installed as the collector field of the newly built solar process heat plant. The collector field with a total area of 170 m2 (155 m2ap) has been integrated into the rooftop of the administrations building. For this purpose, the building’s rooftop had to be stripped down in order to exchange the beams to increase load capacity. Since the plant has been taken into operation in 2010, each year it produces up to 70 MWh heat that is stored in the buffer tank with a temperature of max. 95 °C.

The solar buffer has been connected to the draining tank of the brewing water reserve. An external heat exchanger heats up the cold brewing water up to 80 °C using the solar heat stored in the buffer tank. Afterwards the water is fed into the 50 m³ draining tank that has a variable filling level. This draining tank is part of the brewing water reserve, consisting of two 50-m3-tanks. The brewing water reserve’s second tank, the displacing tank, is constantly filled completely and kept at 80…98 °C in the upper part. This tank mainly supplies mashing and lautering with hot water. The picture above shows the hydraulic of the solar process heat plant at the Hütt brewery.

The controlling for the draining tank’s feed is set to refill it as soon as the tank’s level is below 35 m3. The brewing water is then fed through the discharging heat-exchanger with a volume flow of 1 m3/h and heated up to a maximum temperature of 80 °C by the solar thermal system.

© Hütt-Brauerei
The rooftop-integrated flat-plate collectors heat up the 10 m3 buffer tank via an external heat exchanger. The buffer tank again preheats the cold water for the draining tank by the flow heating method.

The company FSAVE Solartechnik conducted the detailed planning, tendering, and construction supervision; the company ThüSolar GmbH installed the plant. The University of Kassel was substantially involved in the development of the new energy concept for the Hütt brewery’s brew-house, assisted the detailed planning of the solar process heat plant and conducted a monitoring of the system.

The solar process heat plant’s overall costs including the integration were 96,000 €, 50 % of which were given by the German Federal Ministry for the Environment as part of the project “Solarthermie-2000plus”. In total that makes for a solar heat price of 50 €/MWh, drawing upon the yield calculated by simulation studies.