In producing their popular frozen baked goods, the traditional company Back & Frost uses only the finest ingredients – and enormous amounts of cold. Up until now, they have relied exclusively on conventional compressor cooling systems to satisfy this demand. With the recent purchase of a combined heat and power plant (CHP) and to decrease the demand placed on their compressor systems, the company has decided to use eco-friendly adsorption cooling systems from InvenSor.
ADsorption chillers generate cold by using the waste heat produced by combined heat and power plants (CHPs) and other machines as source of energy to drive the cooling process, operating according to the principle of adsorption. Two sub processes alternate with one another in the chiller, thereby achieving a virtually continuous cooling capacity.
The customer had never had a CHP system before, so during the first phase of construction they had the company Kraftland install a CHP system with a thermal output of 293 kW and an electrical output of 199 kW, which featured a 10,000-liter hot water thermal storage tank. The CHP system supplies all the heat used in the entire company; i.e., it heats the production facility, the showers, and the administration building, too. The CHP system also produces electricity, which is used in the company’s operations and to run the compressor chillers. “By making this improvement, Back & Frost is already saving over 27 percent annually in energy costs,” according to Oliver Timm, managing director of Kraftland GmbH.
From Combined Heat and Power to Trigeneration
The next phase was dedicated to the expansion of cooling capacity. The company already operates two cooling circuits with four compressor systems each, keeping the 8,000 m³ cold storage unit at an ultra-low temperature of -20° C and supplying cold air to the blast chiller between production and cold storage. The total nominal power rating of the compressor systems used is 292 kW. However, these cooling units require a massive amount of electricity to provide the cold temperatures required. It’s for this reason, and also because they wanted to make full use of the CHP system during the summer months, that the company decided to expand their cooling capacity. In making this acquisition, Back & Frost managing director Torsten Knoll sought above all to increase the company’s security of supply and permanently decrease its energy costs. Because the company already had a CHP system, after intensive planning and research it was decided that they would purchase two InvenSor LTC 30 e plus ADsorption chillers with free-cooling function, as these cooling systems can be easily combined with the CHP system for a trigeneration system (combined heat, power, and cooling). “It was easy to connect the chillers to the hot water storage tank they already had, and since then they’ve been supplying the company with 60 kW of cooling capacity,” says Oliver Tamm, product manager at InvenSor. CHP systems and adsorption cooling systems work together to provide heat, cold, and electricity at the same time all year round. The built-in free cooling feature allows the chillers to offer even more energy cost savings by having the outdoor unit pump in cold air directly from outside when temperatures reach below 15° C, while the CHP system is used to heat the building. In addition to that, the adsorption chillers will be fully paid off in just four years.
In May of 2017 the ADsorption cooling systems were put into operation. Since then, they’ve been used to cool the condenser for the compressor systems, which has allowed an increase in the deep freeze unit’s efficiency and recooler capacity, since an additional recooler provides waste heat from the adsorption chillers to the environment.
Decentralized Energy Supply
The energy system is located right inside the facility where the food products are made, so when deciding where to place the adsorption chillers it was very important that they not interfere with the production process or take up space on the production floor. At the same time, it was also necessary to keep the connection lines as short as possible. In short order it was decided to put them on the second level of the mechanical room, where four of the eight compressor chillers were already located. The planning work was done using a precise and detailed 3D computer model to guarantee the customer a tailor-made installation process. The plan was a success, and ever since the cooling systems and the CHP system have been working together to produce electricity, heat, and cold.
Technical details of the system
||2 InvenSor aDsorption chillers with a nominal cooling capacity of 60 kW
||CHP „vitobloc 200“ Viessmann with outputs of 293 kW th. / 199 kW el.