Flat-Plate Collectors, Adsorption and Wood Chips in Fruit Processing

Kögerlhof Krispel is a family business founded in 1903 settled in Markt Hartmannsdorf Austria and is being managed in third generation by the family Krispel. The energy used, mainly for the production of fruit-juices and musts but also for cooling of fresh fruit, is produced sustainably with flat-plate collectors and wood chip boilers. The fruits predominantly come from the company’s own fruit crops with more than 50,000 trees. Due to the growing and processing of the fruit the production’s heat demand is very seasonal. The small family business has a yearly sales volume of ca. 700,000 €.

While the work from winter to the early summer consists mainly of cutting, fertilising, and thinning of the fruit trees, from August to November it is harvesting and production time, which demands ca. 15 m3 of water each day mainly for cleaning purposes. Besides that, up until spring fresh fruit is stored in a refrigeration room so it can be sold up until the end of March depending on the kind of fruit. For the production there are two processes with relevant heat demand, which are supported by the solar plant. In order to hygienically prepare the bottles for the filling process, they are machine washed with 75 °C hot water. Also, to preserve the fruit juices they are pasteurised at 80 °C so they can be stored and sold all year long.

Before the conversion to a sustainable energy concept, the pasteurisation of fruit juices was done electrically and later with a gas boiler. The bottle washing machine has been heated directly by an oil boiler. Now a wood chip boiler with a thermal performance of 240 kW in combination with a solar thermal plant of 118 m2 produce all the heat required for these processes. Together with a new pipe pasteuriser it is now possible to cover the company’s complete heat demand without fossil fuels. Additionally, the former compression cooling system has been replaced by an adsorption cooling machine to make the storing of fresh fruit and juices at constantly 5 °C sustainable as well. By installing a 5 kWp PV-plant, which covers the electrical base load but is also able to feed the public power grid, also the power demand has been reduced. The company uses the self-produced power entirely; additionally demanded power is supplied by the power grid.  The innovative and predominantly sustainable energy supply system has been taken into operation in 2012. The photograph depicts the solar collectors (rooftop in the front) for heat and cold supply and the PV-modules (rooftop in the back).

Nine large-scale collectors with 13 m2 each are used for the solar thermal collector field. They heat up a 20 m3 buffer tank with 30 cm isolation and stratifying lances for optimum temperature stratification. The collectors are inclined by 45° to better spread solar yields over the year, since on sunny summer days the heat is almost entirely used for cold-production in combination with the adsorption cooling machine. Target temperatures of 80..98 °C are necessary in order to operate the bottle washing machine, the pasteuriser, and the adsorption cooling system. Therefore, double covered collectors, which also work efficiently at higher temperatures, were chosen. Should the solar radiation be insufficient, the wood chip boiler is used to reheat the buffer. Despite the high process temperatures and the seasonal heat demand, the collectors achieve a specific yield of 380 kWh/m2grossa and a solar fraction of about 20 % concerning heat and cold demand, which equals an overall yield of 45 MWh/a. The image below depicts the hydraulic of the described system.

© Krispel, 120 m² Flachkollektoren bei Kögerlhof Krispel (AT)
The heat produced by the flat-plate collectors is fed into the buffer tank. Besides the pasteurisation and the bottle washing, also the adsorption cooling system is connected to the storage.

The costs of the newly installed solar system together with the 20 m3 buffer tank heated by the wood chip boiler, the process integration, and the adsorption cooling system were at ca. 145,000 €. Roughly a third of that was for the cooling system alone. Therefore, the specific costs for the solar plant including the buffer and integration to the processes were at 855 €/m2. Since the solar plant not only substituted fuel oil and gas with low-price wood chips as an energy source, but also requires less electricity because the compression cooling system was substituted with the solar adsorption cooling system, the energetic makeover of Kögerlhof Krispel is not only an ecological but also an economical win.