Sustainable Energy in Buildings: UOW Library HVAC Design Project

This project focuses on the design of an air conditioning system for the University of Wollongong Library, addressing the heating load requirements for its three floors. The assignment utilizes the Carrier method to estimate the heating load, considering factors such as occupancy, building materials' thermal conductivity, and equipment heat generation. Detailed calculations are performed to determine U-values and heat loss through various components like windows, walls, and ceilings. The analysis reveals the significant impact of design parameters on the heating load. Based on the findings, the project recommends the implementation of renewable energy sources, such as solar PV cells or wind turbines, to supplement the mains electricity supply and reduce energy consumption. Furthermore, it suggests the use of hydrogen-based refrigerants like R-410A over chlorine-based refrigerants to mitigate environmental impact. The project also highlights the importance of providing AC terraces for outdoor units and incorporating mechanical services ducts for fresh air supply and AC pipework to maintain the building's aesthetics and functionality. The attached excel sheet contains detailed calculations for heating load.

Sustainable Energy in Building 1
SUSTAINABLE ENERGY IN BUILDING
Student’s Name
Course
Professor’s Name
Institutional Affiliation
City
Date

Sustainable Energy in Building 2
General Assumptions
Library occupancy is based on the net floor area and each person occupies 10 square metres
(MacKenzie, Nichols, Royle, Pollock, Bailey, and Hines 2017). Air conditioning design for the
Proposed University of Wollongong Library is based on the heating load requirements which is
dependent of several factors such as the interior and exterior temperatures, Building materials,
the area of walls, floors, windows, etc. Different areas in the library require different design
considerations. For instance, the air changes per hour for the study area, lounge, and offices are
taken as 4, while that for toilets is taken as 10 (Brochard, Slutsky, and Pesenti 2017).
a) Heating Load Calculations
Library occupancy
This is based on the total floor area.
Floor Total Occupiable area
(Sq.m)
Ground floor 3000
First floor 3482
Second floor 2800
Total 9282
Number of people= 9282 Sq . m
10 Sq . m
¿ 928.2( Approximately 929 people)
175 Watts of heating load per person in the library is assumed (Gang, Wang, Shan, and
Gao 2015).
Hence, the total heating load due to people;
¿ 92 9 ×175 Watts
¿ 162,575 Watts(163 kW )

Sustainable Energy in Building 3
Table 1: Values for thermal conductivity for different materials (Al-Homoud, 2005)
Material Thermal conductivity (W/mK)
Windows/Glass
6mm Double clear glass 0.96
5mm air gap 0.68
Roof
Roof metal deck 0.98
50mm Insulation 0.35
Ceiling
Fiberglass suspended ceiling 0.49
Exterior Wall
15 mm Gypsum plaster 0.71
110mm Double brick 0.8
50mm air gap 0.68
Determination of U-Values (Siviour, 2018);
U Value= 1
R1 + 1
R 2 +… 1
R 0
Where R0=Air resistivity.
Sample Calculation
Total area for glass=3,000 sq. m
Resistivity= Glass Tickness
Thermal Conductance
Resistivity=0.006
0.96
Resistivity=0.00625
U Value= 1
0.00625 + 1
0.68
U Value=161 W
Sq . m K

Sustainable Energy in Building 4
For the air gap;
Resistivity= Airgap Tickness
Thermal Conductance
Resistivity =0.00 5
0. 68
Resistivity=0.00 7
U Value= 1
0.007 + 1
0.68
U Value=137.47 W
Sq . m K
Total U-value =161+137.47=¿298.47 W
Sq . m K
Total heat loss through the glass is given by the following relation (Ding, Wang, Feng,
Marnay, and Zhou 2016);
Q=Uvalue × Area × ∆T (Watts)
The design temperature difference between the outside and the inside for this area is
estimated to be 5 degrees, Kelvin. Therefore;
Q=298/ 47 ×3,000 ×5
Q=4,481,117.6 Watts(4484 kW )
The above procedure is repeated for the rest of the materials and the results tabulated in
Table 2 below.
Table 2: Summary calculations
Initial Parameters
Material Area (Sq. m)
Windows/Glass 3000
6mm Double clear glass 0.96 0.006 0.006 0.680 161.47 298.94 4484117.6 4484.118
5mm air gap 0.68 0.005 0.007 0.680 137.47
Roof 3200
Roof metal deck 0.98 0.025 0.026 0.680 40.67 49.14 786258.8 786.259
50mm Insulation 0.35 0.05 0.143 0.680 8.47
Ceiling 2000
Fibre glass suspended ceiling 0.49 0.025 0.051 0.680 21.07 21.07
210705.9 210.706
Exterior Wall 5000
15 mm Gypsum plaster 0.71 0.015 0.021 0.680 48.80
72.62 210705.8824 210.706
Thermal
conductivity
(W/mK)
Thickness
(m)
Material
Resistivity
(W/mK)
Air
Resistivity
(W/mK)
U-Value
(W/Sq. mK)
Total U-
Value
(W/Sq. mK)
Total Heat
Loss (Watts)
Total Heat
Loss (kW)

Sustainable Energy in Building 5
Total heat generated from equipment in a school library is assumed to be 50kW (Cur,
Kee, Kuehl, and Wu, Whirlpool Corp 2019).
Total heating load: Heat loss through the glass + Heat loss through walls + Heat loss through
Ceiling - Heat generated by people - Heat generated by the equipment.
Total heating load: ¿ 4484.118 kW +786.258 kW +210.706 kW +210.706 kW −50 kW −163 kW
Total Heating Load=5479.213 kW
b) The solution is in the excel sheet attached.
It is observed that when the design parameters of materials, thickness, etc. are altered, the
heating load is affected significantly.
c) Summary of Sustainability Recommendation
The heating load from the calculation above proves that the size of the air conditioning plant
has high capacity. In this effect, power consumptions will be high and thus the electricity bills. It
is recommended that the management of the university invest in renewable energy sources for
the air conditioning plant such as solar PV cells that taps energy from the sun of wind turbines.
These energy sources could be used as a supplement to the mains electricity (Twidell and Weir
2015).
There is a dozen of refrigerants available in the market today (Davis and Gertler 2015). Some
of these refrigerants are associated with the greenhouse gas emitting that depletes the ozone
layer. The University project management team should, therefore, consider purchasing air
conditioning equipment that uses hydrogen-based refrigerants such as R-410A rather than
chlorine-based refrigerants such as R-12 (McLinden, Brown, Brignoli, Kazakov, and Domanski
2017).

Sustainable Energy in Building 6
The proposed library design is good as far as air conditioning is concerned. The only bit that
would need improvement is the provision for AC terraces to accommodate some of the outdoor
units such as those that would serve the management and server rooms.
Fresh air supply for a library is paramount (Connell and Bergstrom 2017). The plans do not
include the Mechanical Services ducts where the ductwork for fresh air supply and AC pipework
can be passed. This is very crucial as part of the initial design as it saves on space and
maintaining the aesthetics of the building.

Sustainable Energy in Building 7
Reference List
Al-Homoud, M.S., 2005. Performance characteristics and practical applications of common
building thermal insulation materials. Building and Environment, 40(3), pp.353-366.
Brochard, L., Slutsky, A., and Pesenti, A., 2017. Mechanical ventilation to minimize progression
of lung injury in acute respiratory failure. American journal of respiratory and critical care
medicine, 195(4), pp.438-442.
Connell, B.S., Bergstrom Inc, 2017. Air conditioning system utilizing heat recovery ventilation
for fresh air supply and climate control. U.S. Patent 9,796,239.
Cur, N.O., Kee, T.A., Kuehl, S.J. and Wu, G., Whirlpool Corp, 2019. Air conditioning systems
for at least two rooms using a single outdoor unit. U.S. Patent Application 10/180,257.
Davis, L.W. and Gertler, P.J., 2015. Contribution of air conditioning adoption to future energy
use under global warming. Proceedings of the National Academy of Sciences, 112(19), pp.5962-
5967.
Ding, Y., Wang, Z., Feng, W., Marnay, C. and Zhou, N., 2016. Influence of occupancy-oriented
interior cooling load on building cooling load design. Applied Thermal Engineering, 96, pp.411-
420.
Gang, W., Wang, S., Shan, K. and Gao, D., 2015. Impacts of cooling load calculation
uncertainties on the design optimization of building cooling systems. Energy and Buildings, 94,
pp.1-9.

Sustainable Energy in Building 8
MacKenzie, D.I., Nichols, J.D., Royle, J.A., Pollock, K.H., Bailey, L., and Hines, J.E.,
2017. Occupancy estimation and modeling: inferring patterns and dynamics of species
occurrence. Elsevier.
McLinden, M.O., Brown, J.S., Brignoli, R., Kazakov, A.F., and Domanski, P.A., 2017. Limited
options for low-global-warming-potential refrigerants. Nature Communications, 8, p.14476.
Siviour, J.B., 2018. Experimental U-values of some house walls. Building Services Engineering
Research and Technology, 15(1), pp.35-36.
Twidell, J. and Weir, T., 2015. Renewable energy resources. Routledge.