ASHRAE Journal - August 2014 - 82

2014 ASHRAE TEcHnology AwARd cASE STudiES

In this way, the refrigeration heat is recycled and
the heat is air dissipated by a fluid cooler (Figure
2) only if the tank temperature is more than 100°F
(38°C). The 883 ft3 (25 m3) buffer tank is enough to
preheat the milk to 84°F (29°C), without dropping
more than 13°F (7°C) even for the biggest summer
cheese production. Using this configuration, chiller
heat is partially dumped outside only in summer.
The 23°F (-5°C) glycol loop supplies all cold rooms,
brines, a cheese aging room, food display cabinets in the
plant store and, in the summer, the 100% fresh air, HEPA
filtered production ventilation unit.

Energy Efficiency
Milk pasteurization, the main energy consumption process used in cheese production, was modified
(Figure 3) to use low temperature "free" energy from
the chiller condenser and minimize high temperature
energy use. In this way, ~85% high temperature heating
reduction was obtained.
For 800,000 gallon (3 million L) of milk production annually, the energy savings represents about
87,000 kWh, meaning 2,600 gallons (10 000 L) fewer
gallons of heating oil are used, for 85% hot water production efficiency. All the hot washing water (~149°F
[~65°C]) is preheated to 86°F (30°C) to 95°F (35°C) with
"free" temperate water, reducing high temperature
energy needs by 40%.
The new 2,500 cfm (118 L/s) makeup air unit for the
production area was designed to be able to heat the air
in the worst winter conditions with only the 86°F (30°C)
glycol loop at low flow rate. This way the unit uses the
"free" temperate water tank as a priority, resulting in
energy reduction. The digester feed (~68°F [~20°C]) is
preheated with the "free" temperate water. To minimize
heat losses all the tanks are insulated with 6 in. (152 mm)
polyurethane foam, and buried liquid loops are factory
preinsulated pipes.
In addition to the 2,500 cfm (118 L/s) makeup air unit,
five buildings totalling 8,100 ft2 (753 m2), including the
owner's 3,000 ft2 house, were added to the heating load.
Table 1 shows heating oil consumption in 2011-2012 (prior
to the project's completion) and in 2012-2013. In both
cases the milk production was the same.
Considering a mean heating load of 0.7 Btu/h·ft3
(7 W/m3), 23 heating weeks and an 85% efficiency
for the boiler that uses heating oil, 2,600 gallon
82

ASHRAE JouRnAl

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Au g ust 2014

Project Goals
*	Construct a digester to produce biogas from cheese
production effluent (whey and white water) and use the
biogas for cheese production and to heat the building;
*	Concentrate the sources of heat and cold in one place,
using reliable equipment with enough capacity to increase production;
*	Create three different temperature level liquid loops
able to supply heat and cold to all clients;
*	Take into account the time delay between source generation and the factory's demands by using water buffer
tanks for energy accumulation;
*	Minimize energy use and maximize heat recycling;
*	Change the pasteurization process so milk could be
preheated using rejected refrigeration heat;
*	Add ventilation (100% fresh air) in the cheese production area to ensure a positive pressure and correspond
to Canadian Food Inspection Agency regulations; and
*	Implement a control system to survey the mechanical system, and automated control of main production
processes, alarms handling and optimization of energy
consumption.

(10 000 L) more heating oil would have been used to
heat all new building loads had the project's improvements not been implemented. Taking into account
the monthly mean temperature and the 24 hour/day
production schedule, the additional heating load
for the 2,500 cfm (118 L/s) fresh air unit would have
required an additional 3,700 gallons (14 000 L) of
heating oil. The actual reduction in heating oil is
approximately 64%.

Indoor Air Quality
The volume of fresh air in the production area is more
than two air changes per hour, exceeding provincial
health and security regulations for cheese production
spaces. During production, 10 to 15 people occupy a less
than 4,000 ft2 (372 m2) floor. In these conditions, 2,500
cfm (118 L/s) fresh air ensures more than 0.5 cfm/ft2 (2.5
L/s·m2), which exceeds the most restrictive requirements of ASHRAE Standard 62.1-2009.
The absence of air recirculation and the use of 100%,
HEPA-filtered fresh air and building positive pressure in
ASHRAE Journal - August 2014

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