The Efficiency Of FAHRenergy HRV Solar In A Kitchen
One ‘FAHRenergy HRV-Solar’ unit is
in the kitchen.
Next to the kitchen is a small utility room with a door which leads to the garden.
A door connects the kitchen and a medium sized lounge. The total space is 70m3
The ‘FAHRenergy Solar’ unit
of heat recovered fresh air every
Governments generally specifies an exchange of the air every 2 hours as minimum.
The Value Of The Installation
The kitchen FAHRenergy system
discussed to the left
gives optimal value on several levels:
The old kitchen has been
transformed from a cold, smelly
place with draft and potential
poisonous carbon monoxide to a pleasant and healthy work
The adjacent lounge has become a fresh healthy room at
reduced energy need and no other cost than a 2m
This has all been achieved without extra energy!
The chart below shows the energy
collected over 24 hours on two different days
and under two conditions:
1: The cooker is off and thus the
cooker hood. The result, in kilowatt hours (Kwh),
is shown in yellow colours.
2: The cooker is on and thus the cooker hood. The result is shown in red colours.
The 5.3Kwh and 5.6Kwh are actually recovered as the FAHRenergy system was
active all 24 hours.
The result with the Cooker On
would have recovered the shown energy if the cooker
was on 24 hours. This is obviously not the case. How much energy that is actually
recovered depends on how many hours the cooker is on.
November 2006 was a normal day with no excessive cooking.
Outdoor temperature = 3.2°C.
December 2006 was a party day with extra cooking.
Outdoor temperature = 2.5°C.
Depending on the cooking habits it
is likely that the recovery of cooking energy
improves the actually collected energy by more than 20% . A valuable addition over
the years as the added installation effort and price normally is minimal.
The calculated efficiency from the two days is shown below:
The efficiency of the
installed FAHRenergy system with the cooker off is 78%
84% respectively on the days the measurements were collected. This is expected for
a sensibly installed system. The efficiency will vary from day to day due to variables
as open/closed doors and windows, moisture in the air, in/out temperature
differences, duct insulation quality and general measurement errors.
The efficiency with the cooker on
shows the added value the recovery of the cooker
energy gives. The actual efficiency of the system does not change whether the cooker
is on or off. If the cooker energy were added to the calculation on the ‘old air’ side the
result would be the same as with the cooker off.
Medium’ unit consumes 10w which becomes
240wh per day or 5%
of the recovered energy.
The energy recovered is 20 times larger than the energy consumed.
The room unit is fitted with rectangular connections and is small enough to hide behind a standard curtain. This allows for having the entire system in the room in which it must exchange the old air with fresh heat recovered air.The installation uses an existing draft window for expelling old air and drawing in fresh air. In this way holes for ducts are avoided.
The Value Of The Installation
The lounge FAHRenergy system discussed above gives optimal value on several levels:
The chart shown below shows the energy collected on 4 specific days:
The energy collected on any
given day depends
on several factors. The most pronounced factor is the temperature
difference between the indoor temperature
and the outdoor temperature. The larger the difference between these two temperatures, the larger the collected energy will be.
From collected data the system efficiency has been calculated and is shown in the chart below:
The general energy efficiency for this system is over 80%.
As this installation is
balanced, that is the volume of old heated
air entering the FAHRenergy unit is the same as the volume of cold
fresh air entering the system, energy efficiency and
returned in % are the same.
The temperature returned is over 80% of the temperature of the old air. This means that the incoming fresh air is pleasantly heated and no extra heating of the incoming fresh air is needed.
Efficiency Difference From Day To Day
The measured efficiency depends on many factors such as: