Durable and efficient ventilation units exceed ErP requirements

In terms of the economic efficiency of ventilation units, an investment in sustainable and efficient technology pays off several times over. "The low energy consumption and small carbon footprint are particularly striking here," according to Tom Melching, Technical Advisor at WOLF Energy Systems. "The operating costs of a unit designed according to the WOLF standard are significantly lower than the minimum requirements of the ErP directive."

To supply buildings with fresh air, one must take into account the applicable standards and guidelines. But also with the environmental aspects. "For example, the lowest possible energy consumption for ventilation and air conditioning helps reduce CO2 emissions as well as costs," Melching said. "After all, about 90% of the total CO2 emissions of a ventilation unit are emitted during operation." 

Large savings potential

ErP Regulation 1253/2014/EC applies to the environmentally friendly design of ventilation systems. "The WOLF ventilation unit exceeds these requirements," says Melching, who supports his claim with an example. Here he compares a WOLF unit in an existing office building in Munich with a fictitious unit, which just complies with the current ErP directive. "The savings potential of the WOLF unit compared to a base unit according to ErP requirements is 41% for power consumption and 7.9% for heat recovery. This not only has a positive effect on CO2 emissions; the additional investment in economical technology also pays for itself very quickly."

In the Munich project, the existing rental space on the 1st floor had to be expanded into an office and event space for up to 800 participants. An additional air handling unit and a new pipe distribution network for the existing unit on the roof were necessary for this. "A total air volume of 22,000 m³/h (external pressure: 500 Pa) was required. Due to the limited space, the unit had to be placed on the 3rd floor of the building in a technical room and the piping and associated installation had to be relocated within the building."

Low air speed

To keep the power consumption of the fans as low as possible, the air speed in the unit is low. For example, because of the larger cabinet cross-section. "A more compact unit would have generated higher air velocities. While this would certainly meet ErP specifications, it has a detrimental effect on all other components in the unit. The pressure losses of the individual air handling functions such as the heat exchanger, filter and HRU system increase at higher air velocities and lead to higher power consumption of the fans."

Rotary heat exchanger

A highly efficient rotary heat exchanger with low leakage was selected for heat recovery. "The sealing system is not placed on the side of the rotor, but rotates with the rotor. Several sealing fins on the wall ensure a high degree of tightness with the rotating part. In combination with central seals according to the WOLF SuperSeal labyrinth seal, a tightness of 98% becomes possible, in contrast to classic models with a leakage rate of about 10%. In this case, additional air volumes must be taken into account in the design of the supply and return air fan according to VDI 3803/5. This in fact increases the energy consumption of the fans."

High heat recovery

The heat recovery of the unit described above is 116 kW (ErP: 108.6 kW) and the heat recovery index is 78% (ErP: 73%). "This results in a savings of 7.9% or 8.2 kW compared to the ErP," Melching said. "With 5,000 operating hours per year, the WOLF unit saves 41,000 kWh of thermal energy through heat recovery alone. In terms of fuel oil consumption, this corresponds to a saving of about 4,180 liters for heating or about 11 tons of CO2 equivalent. Assuming a purchase price of €0.80 per liter of heating oil, this results in annual savings of €3,344. Without rising CO2 prices and other price increases, this corresponds to a total savings of at least 66,880 euros within 20 years."

High savings potential

Power consumption also looks good, according to Melching. "Instead of the 950 W/(m³/s) required by the ErP, only 561 W/(m³/s) per year is needed here. That's only 59% from the reference value. The savings are 389 W/(m³/s) or 2.38 kW. Extrapolated to one year, this is a total of 11,900 kWh for 5,000 

operating hours. Assuming an electricity price of 0.40 euros, the savings amount to 4,760 euros or 5.18 tons of CO2 equivalent. This corresponds to the average electricity consumption of 3 families of 4 people. Within 20 years, without inflation compensation and CO2 pricing, this amounts to at least 95,200 euros."

If the operating costs per year are added up, the technically optimized WOLF unit results in the remarkably high savings potential totaling 162,000 euros or 323.60 tons of CO2 equivalent. The break-even point for the additional investment in the more efficient unit is thus already reached after about one year, or much sooner if the number of operating hours per year is higher or if energy prices increase. The above calculation was performed without the positive effect of intelligent control. In practice, consumption values can therefore be reduced even further, by demand-driven control based on room occupancy.