ERV is a breath of fresh air

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Even though a proper ventilation strategy offers substantial savings, its role is less clearly defined than chillers, cooling towers and pumps. International Mechanical Engineering Corporation (IMEC) executive director Aslan Al-Barazi takes a closer look at the issue.

Global warming and the greenhouse effect may seem removed from our everyday lives. Being in the MEP HVAC business, however, we play a major part in this chain. About 60% to 70% of the total energy produced is attributed to HVAC. The actual carbon footprint (in kilograms) of this can be measured; the corollary is that the attendant savings when using environment-friendly ventilation products can also be calculated.

IMEC, in collaboration with Vent-Axia, conducted a year-long (January to December) study in this regard, based on a commercial air-conditioned office with a balanced central ventilation system. The air flow was 0.555 m³/s and the mean room temperature was 23°C. The following figures were derived at:

Annual losses with no energy recovery
Monthly kW/h: 16 300
Energy costs: AED5 379
Carbon dioxide generated: 16 952 kg

The fixed-volume ventilation system also suffers from over-ventilation when offices are partially occupied, with higher running costs and shorter filtration life cycles, which equates to increased maintenance costs. With the adoption of the Sentinel Totus demand energy recovery ventilation system from Vent-Axia (90% energy recovered from used cooled indoor air being extracted to lower hot incoming air), there are significant reductions in the annual air-conditioning load and carbon dioxide generation:

Annual Savings with energy recovery
Recovered energy kW/h: 14 670
Energy cost saved: AED4 841
Carbon dioxide saving (kg): 15 257

Payback analysis
Product costs
Supply and extract fan: AED8 175
Energy recovery ventilation unit: AED24 347
Variance: AED16 172

Savings
Reduction in air-conditioning cost: AED8 125
Recovered energy cost: AED4 841
Total reduction: AED12 966

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FEATURED COMMENT Excellent, encouraging, information presented by Mr.Aslan Al-Barazi. Is it possible for you to generalize your estimatio   1 Comments Read more comments »

These putative savings allow significant reductions to the installed air-conditioning plant capacity; reduced installation costs (six units as opposed to seven); and reduced operating costs.

The demand ventilation strategy opted for optimises fresh-air ventilation for occupants (carbon dioxide control), ensuring excellent indoor air quality.

In addition, there is added potential for further significant running cost reductions when the offices are only partially occupied. Another interesting result of the above study was from the lifecycle cost analysis perspective. The study showed that payback would accordingly be in less than two years. Thus the system advantage applies to both environment as well as returns on investment.

It also has built-in carbon dioxide sensors, allowing the carbon dioxide level to be specified at the correct and healthy standard of no more than 1 500 parts per million. The carbon dioxide sensory system would then pace the levels of carbon dioxide in the air, regulating the fresh air as and when needed. This naturally increases the levels of alertness and consequential performance from both a workforce perspective as well as an academic/schools perspective, which is ultimately the most important investment any country can have.

The system’s environmental settings also features acoustic linings for noise control, and can be operated via a building management system if need be. The Sentinel Totus system from Vent-Axia is the UK’s first D-ERV (demand energy recovery ventilation) system to be rated independently and tested to EN308. Vent-Axia’s low-carbon ventilation range includes EC/DC motors, which not only reduce power consumption by up to 90%, but which can actually reduce their carbon footprint by 7 kg to 47 kg a year. The Sentinel D-ERV solution goes one step further by featuring in-built sensors for carbon dioxide, pressure (passive infrared occupancy detection), temperature and humidity. This system can sense when occupants enter a room, and adjust the air-flow accordingly to the number of occupants. The fans stop operating as soon as the occupants leave the room.

The Totus range incorporates both EC/DC motor, on-demand ventilation and heat recovery, and is able to extract up to 90% of the cooling load being wasted via discharge back to the outside atmosphere.

It achieves this by means of a counter-flow heat exchanger that furthermore does not contaminate the intake flow with the flow being exhausted outside the building, as they are in separate flow circuits. Thus it is ideal for schools, hotels, theatres, offices and other environments with changing occupancy rates.

For further detailed information on the IMEC/Vent-Axia cost-effectiveness study, contact Aslan Al-Barazi at imec@emirates.net.ae.