EnergARA – Energy from exhaust air treatment systems

During 2020 and 2021 Inno+ worked in collaboration with the Institute of Agricultural Engineering, University of Bonn, on a case study to determine the benefits of using regenerative energy from “exhaust air treatment systems” (Air scrubbers) for cooling and heating of animal houses.

Background

Pig husbandry leads to emissions of ammonia, dust and odour, which can affect both local residents and nearby ecosystems. The use of Air scrubbers serves to separate and reduce these emissions. In some German federal states, the use of these systems is required in the approval procedures for individual facilities. The keeping of pigs in closed houses requires energy, for example to allow proper operation of the ventilation system to maintain the room temperature according to the requirements of the animals. It is the task of the ventilation system to remove polluted air inside the barn compartments and replace it with fresh air. The use of heat recovery systems makes it possible to transfer energy from the warm exhaust air stream to the incoming cold fresh air stream and thus reduce the need for other more costly heating in the barn.

In the “EnergARA” research project, three specific housing systems, which use an exhaust air treatment system in combination with heat recovery, were investigated over long periods. Recording of the power consumption of the individual systems, as well as the air and water temperatures at different positions within the barn were used to determine the efficiency and capacity of the heat transfer. The analysis of the collected data was used to show economic, ecological and animal welfare-based evaluation of the individual plants as well as their combined benefit. The aim, to identify possible synergy effects in order to answer the question; to what extent exhaust air treatment systems can be used as regenerative energy sources for the heating and cooling of pig houses. The research project intended to show contribution to the improvement of energy and resource efficiency in modern pig farming.

Research methodology

Long term measurements in pig husbandry buildings using exhaust air treatment and heat recovery systems from various manufacturers, under practical conditions. The measurement periods were planned for at least 1 year for each technology.

Measured Parameters included:

• Air and water temperatures
• Fresh air
• Supply air
• Compartment air
• Exhaust air
• Wash water
• Water within the Triple EEE system [°C]
• Supply air flow [m³ h¹]
• Power consumption [kWh]

Results

The available measurement period was for 7 months between 24.11.2020 – 30.06.2021. It was noted the measurements during this cold period could overestimate the performance because of ‘many cold days or months’, respectively.

Workload of the Triple EEE system during this period was on average 87.0% (max. 100% in December 2020, min. 22.2% June 2021). This means the system was running 87% of the time, contrary to what many farmers believe, that it only runs during the extremely cold periods.

Average temperature amplitude damping between outdoor- and supply air: -33.1% (max. -48.7% in April 2021, min. -13.6% June 2021). Amplitude damping is the ability of the system to reduce the difference between minimum and maximum air temperature. This is particularly important in the transitional seasons of spring and fall, when temperatures are already cold at night but still very warm during the day. An example is given in the figure by the temperature profile of the 14^th February 2021. The lower the amplitude, the more uniform the ventilation, and thus the air quality and temperatures in the barn. A constant barn climate has a positive effect on animal welfare and health and can thus contribute to good performance. This also leads to economic benefits for the farmer.

Preliminary results show that the total thermal energy recovered was 259,425.63 kWh. The energy efficiency could be improved; In the first six months of measurements, per kWh of consumed electrical energy 33.11 times more thermal...