Enhancing Green Building Rating of a School under the Hot Climate of UAE; Renewable Energy Application and System Integration

energies Article
Enhancing Green Building Rating of a School under
the Hot Climate of UAE; Renewable Energy
Application and System Integration
Joud Al Dakheel, Kheira Tabet Aoul * ID and Ahmed Hassan ID
Architectural Engineering Department, United Arab Emirates University, P.O. Box, 15551 Al Ain, UAE;
[e-mail] (J.A.D.); [e-mail] (A.H.)
* Correspondence: [e-mail]; Tel.: [phone]
Received: 2 March 2018; Accepted: 5 July 2018; Published: 17 September 2018





Abstract: Similar to many fast growing countries, the United Arab Emirates (UAE) witnessed fast
population and urbanization growth. The building sector accounts for a major share of its electricity
consumption, reaching up to 70%. To encourage sustainable development and reduce energy
consumption and emissions, the government introduced a sustainability initiative called “Estidama”,
which employs the use of the Pearl Building Rating System (PBRS). Government buildings, which
constitute 20% of the built environment, aim to lead the way, and are therefore required to attain
a high level of achievement, based on their PBRS ranking (minimum of two out of five pearls).
Schools, led by Abu Dhabi Educational Council (ADEC), are governmental buildings and aim to
attain a higher level of achievement (three out of five pearls). The ADEC plans to build one hundred
schools to be built by 2020, through its Future Schools Program. Over half of the schools have been
completed, but only 20% reached the targeted rating (of three out of five pearls). The Renewable
Energy (RE) application in the UAE is minimal, although it represents 25% of the local rating code.
The objective of this paper is to explore the sustainable performance of one representative school that
did not reach the desired green rating level, with the objective to assess opportunities for an enhanced
performance. This is done through testing the performance and the application of three RE systems
comprising of photovoltaics (PV) array, an absorption cooling system and a geothermal cooling
system through Transient Systems Simulation (TRNSYS) software. Cumulatively, implementation of
these options results in RE potentially contributing to 19% of the school’s annual energy consumption,
enhancing the school’s performance by up to 14 additional credit points, and reaching the target level
of achievement (a three pearl rating). Furthermore, system integration of RE into the existing school
were also considered. Results indicate the significant potential of integrating RE systems in future
schools in hot climatic contexts, for an improved energy performance.
Keywords: building energy performance; green building rating system; photovoltaic; solar absorption
chiller; geothermal; schools; UAE; TRNSYS
1. Introduction
Fast growing economies often share common traits in terms of population growth and rapid
urbanization, resulting in high energy demand and significant carbon emissions. Abu Dhabi, the capital
of the United Arab Emirates (UAE), has similarly experienced a sharp increase in energy demand,
leaping from 25,423 GWh in 2005 to 62,248 GWh in 2015. This drove similar increases in generation
capacity, as indicated in Figure 1 [ 1]. The surge in energy consumption, positions the UAE as one
of the world’s largest energy consumers per capita, with the building sector accounting for almost
70% of its total electrical energy consumption [2]. The primary electricity loads in the UAE are, by far,
Energies 2018, 11, 2465; doi:10.3390/en11092465 www.mdpi.com/journal/energies

Energies 2018, 11, 2465 2 of 14
cooling demand, then lighting, refrigeration and other appliance loads. In Abu Dhabi, the residential
electricity load distribution is 47% for cooling (but can exceed 60% during the summer peak), 7% for
lighting, 3% for refrigeration and 35% for other appliance loads [3]. The UAE’s extreme hot climate,
and subsequently high cooling demand, generated a challenging environment for energy conservation
and environmental sustainability of buildings [4].Energies 2018, 11, x FOR PEER REVIEW 2 of 15
for almost 70% of its total electrical energy consumption [2]. The primary electricity loads in the
UAE are, by far, cooling demand, then lighting, refrigeration and other appliance loads. In Abu
Dhabi, the residential electricity load distribution is 47% for cooling (but can exceed 60% during the
summer peak), 7% for lighting, 3% for refrigeration and 35% for other appliance loads [3]. The
UAE’s extreme hot climate, and subsequently high cooling demand, generated a challenging
environment for energy conservation and environmental sustainability of buildings [4].
Figure 1. Total electricity power production in the Abu Dhabi emirate [1].
In line with worldwide initiatives to implement energy efficiency strategies in buildings, the
UAE government introduced in 2008 a stringent sustainability code, named “Estidama” [5].
Followed in 2010 by the development of a green building rating system, named the Pearl Building
Rating System (PBRS). The latter aligns with the principles of international green building rating
systems, aiming to promote the development of sustainable buildings. The code compliance is
governed by the PBRS, ranging from one to five pearls, ranking the level of achievements across
seven categories. Similarly to most green rating system, PBRS is comparable with Leadership in
Energy and Environmental Design (LEED) and Building Research Establishment Environmental
Assessment Method (BREEAM) rating systems. It rates buildings based on six categories: (1)
Integrated Development Process (10 credit points), (2) Natural Systems (14 credit points), (3) Livable
Communities (35 credit points), (4) Precious Water (37 credit points), (5) Resourceful Energy (42
credit points), and (6) Stewarding Materials (19 credit points)]. The first level of a building
attainment requires meeting all mandatory credits and would gain one pearl, while if it achieves 60
additional credits it will reach the second level of attainment (or two pearls). Reaching 85 credits will
achieve the third level or three pearls, while 115 credits translates to four pearls, and 140 credits
qualifies for five pearls, which is the maximum number of pearls. The PBRS has a manual with
specific guidelines on the methodology and calculation equations that are used to validate each
system in order to achieve the credits [6].
The Precious Water and Renewable Energy categories are the dominant categories, comprising
of the highest number of credit points. Twenty five percent of each of these categories represents a
response to the context: characterized by scarcity of water and the extreme harsh climate that
requires a substantial amount of cooling. The UAE has one of the highest sun exposure rates in the
world, giving it a high potential for renewable energy development [7]. The application of RE in the
UAE has been minimal and needs to be reinforced more in buildings in order to overcome the
current energy challenges. Renewable energy makes up less than 0.1% of the UAE’s total final
energy consumption, which is unsustainable due to global current energy consumption challenges
[8]. The UAE’s RE energy base was non‐existent in 2008. Since then, approximately 150 megawatt
(MW) of solar panels have been installed, and over 300 additional MW have been announced. A
further 100 MW of solar photovoltaic (PV) in Dubai, and 53 MW of waste‐to‐energy in Sharjah, was
constructed. Nevertheless, in the context of other Gulf Cooperation Countries (GCC), the UAE has
30000
40000
50000
60000
70000
2011 2012 2013 2014 2015
GWH
Energy Available Electric Consumption
Figure 1. Total electricity power production in the Abu Dhabi emirate [1].
In line with worldwide initiatives to implement energy efficiency strategies in buildings, the UAE
government introduced in 2008 a stringent sustainability code, named “Estidama” [ 5]. Followed in
2010 by the development of a green building rating system, named the Pearl Building Rating System
(PBRS). The latter aligns with the principles of international green building rating systems, aiming to
promote the development of sustainable buildings. The code compliance is governed by the PBRS,
ranging from one to five pearls, ranking the level of achievements across seven categories. Similarly to
most green rating system, PBRS is comparable with Leadership in Energy and Environmental Design
(LEED) and Building Research Establishment Environmental Assessment Method (BREEAM) rating
systems. It rates buildings based on six categories: (1) Integrated Development Process (10 credit
points), (2) Natural Systems (14 credit points), (3) Livable Communities (35 credit points), (4) Precious
Water (37 credit points), (5) Resourceful Energy (42 credit points), and (6) Stewarding Materials
(19 credit points)]. The first level of a building attainment requires meeting all mandatory credits
and would gain one pearl, while if it achieves 60 additional credits it will reach the second level of
attainment (or two pearls). Reaching 85 credits will achieve the third level or three pearls, while
115 credits translates to four pearls, and 140 credits qualifies for five pearls, which is the maximum
number of pearls. The PBRS has a manual with specific guidelines on the methodology and calculation
equations that are used to validate each system in order to achieve the credits [6].
The Precious Water and Renewable Energy categories are the dominant categories, comprising
of the highest number of credit points. Twenty five percent of each of these categories represents
a response to the context: characterized by scarcity of water and the extreme harsh climate that requires
a substantial amount of cooling. The UAE has one of the highest sun exposure rates in the world,
giving it a high potential for renewable energy development [ 7]. The application of RE in the UAE has
been minimal and needs to be reinforced more in buildings in order to overcome the current energy
challenges. Renewable energy makes up less than 0.1% of the UAE’s total final energy consumption,
which is unsustainable due to global current energy consumption challenges [8 ]. The UAE’s RE energy
base was non-existent in 2008. Since then, approximately 150 megawatt (MW) of solar panels have been
installed, and over 300 additional MW have been announced. A further 100 MW of solar photovoltaic
(PV) in Dubai, and 53 MW of waste-to-energy in Sharjah, was constructed. Nevertheless, in the context
of other Gulf Cooperation Countries (GCC), the UAE has maintained the lead in total contracted
capacity and project scale [ 9]. Early RE feasibility studies for Gulf countries directed their attention
to greenhouse gas emissions as a driver [10 ,11]. Sustainability and the use of RE is prominent in the

Energies 2018, 11, 2465 3 of 14
strategic plans of the country, in terms of targets that will need to be achieved though RE contribution
to the overall energy sector. Despite the overall intents, there is still a significant gap in the integration
of RE which creates an opportunity for its integration within buildings in the UAE.
The government-sector buildings account for 20% of the building stock. Therefore, there is focus
to adopt energy efficient practices in order to curb energy consumption, as well as establishing better
building practices [12 ]. Governmental buildings aim to lead the way, and are therefore required to
achieve at least two pearls [ 6] by adopting energy efficiency measures and integrating RE systems.
Among all public buildings, school buildings have a major social and energy responsibility on account
of their educational purpose. Educational facilities are a vital field to implement the sustainability
practices and energy efficiency programs. Many countries are developing sustainable regulations
and policies for schools building. In order to achieve several national energy efficiency targets,
the local governments support all possible and effective initiatives to augment the benefits and the
sustainable practices [13, 14 ]. Therefore, the Abu Dhabi Educational Council (ADEC), a governmental
entity, envisaged a promising 10-year strategic plan (2010–2020) named the “Future Schools Program”.
This program seeks to construct 100 new schools with a minimum rating of two pearls (60 out of
140 points), and a strongly targeted higher goal of three peals (85 out of 140 points) [15 , 16]. To date,
53 schools have been completed that meet the mandatory two pearl requirement. However, only 20%
of these schools have reached the desired target of three pearls. This research aims to uncover the
viability of enhancing the green rating performance of school buildings, through renewable energy
integration. This research explores the performance of one recently built school under the hot climate
of the UAE, which did not reach the desired rating (3 pearls), to serve as a model for the 100 planned
schools that are built, or due to be completed by 2020. The aim of this paper is to explore the sustainable
performance of one representative school in the context of the UAE’s hot climate, with the objective to
assess opportunities for an enhanced performance.
2. Analysis of the School Green Rating System Performance
A review of green rating achievements of a newly built school prototype was carried out based
on the design files and data from the educational council (Figure 2). The school was selected based
on its green rating level of achievement (two pearls). The data included architectural drawings,
design strategy, and technical specifications. The simulated data of the school performance including
building loads, electricity consumption, operational schedules, and used systems. The documentation
review revealed that the school already achieved most credits related to passive building envelope
components, such as insulation, roof, and glazing systems; and active systems such as LED lighting,
sensors, controls, and water efficiency.Energies 2018, 11, x FOR PEER REVIEW 3 of 15
maintained the lead in total contracted capacity and project scale [9]. Early RE feasibility studies for
Gulf countries directed their attention to greenhouse gas emissions as a driver [10,11]. Sustainability
and the use of RE is prominent in the strategic plans of the country, in terms of targets that will need
to be achieved though RE contribution to the overall energy sector. Despite the overall intents, there
is still a significant gap in the integration of RE which creates an opportunity for its integration
within buildings in the UAE.
The government‐sector buildings account for 20% of the building stock. Therefore, there is
focus to adopt energy efficient practices in order to curb energy consumption, as well as establishing
better building practices [12]. Governmental buildings aim to lead the way, and are therefore
required to achieve at least two pearls [6] by adopting energy efficiency measures and integrating
RE systems. Among all public buildings, school buildings have a major social and energy
responsibility on account of their educational purpose. Educational facilities are a vital field to
implement the sustainability practices and energy efficiency programs. Many countries are
developing sustainable regulations and policies for schools building. In order to achieve several
national energy efficiency targets, the local governments support all possible and effective initiatives
to augment the benefits and the sustainable practices [13,14]. Therefore, the Abu Dhabi Educational
Council (ADEC), a governmental entity, envisaged a promising 10‐year strategic plan (2010–2020)
named the “Future Schools Program”. This program seeks to construct 100 new schools with a
minimum rating of two pearls (60 out of 140 points), and a strongly targeted higher goal of three
peals (85 out of 140 points) [15,16]. To date, 53 schools have been completed that meet the mandatory
two pearl requirement. However, only 20% of these schools have reached the desired target of three
pearls. This research aims to uncover the viability of enhancing the green rating performance of
school buildings, through renewable energy integration. This research explores the performance of one
recently built school under the hot climate of the UAE, which did not reach the desired rating (3 pearls),
to serve as a model for the 100 planned schools that are built, or due to be completed by 2020. The aim of
this paper is to explore the sustainable performance of one representative school in the context of the
UAE’s hot climate, with the objective to assess opportunities for an enhanced performance.
2. Analysis of the School Green Rating System Performance
A review of green rating achievements of a newly built school prototype was carried out based
on the design files and data from the educational council (Figure 2). The school was selected based
on its green rating level of achievement (two pearls). The data included architectural drawings,
design strategy, and technical specifications. The simulated data of the school performance
including building loads, electricity consumption, operational schedules, and used systems. The
documentation review revealed that the school already achieved most credits related to passive
building envelope components, such as insulation, roof, and glazing systems; and active systems
such as LED lighting, sensors, controls, and water efficiency.
Figure 2. External view of the school [17].
Figure 2. External view of the school [17].

Energies 2018, 11, 2465 4 of 14
The design strategies implemented in the school were based on the local PBRS green rating
requirements. A detailed review of the school’s two pearl rating revealed that it achieved 81 credit—only
4 points short of achieving the desired level of attainment (three pearls). The analysis revealed that the
highest number of unachieved credits (up to 70%) were within the Resourceful Energy category, despite
this being the most weighted PBRS category. The RE credit distribution comprises of 6 sub-categories,
by which 25 credit points were not achieved. The main reasons for this, as indicated in the submission
files, were due to the in the lack of expertise offered in the field, therefore this school provides a good
opportunity for the investigation of the energy performance enhancement of the building.
This scenario provides a promising potential to explore the use of renewable energy generation.
A review of Abu Dhabi’s climatic data revealed that the weather remains predominantly hot and
humid, with peak summer temperatures reaching 48 ◦C and a relative humidity of 90% [ 18]. Extreme
weather such as this requires extensive air conditioning, which may contribute up to 75% of a building’s
energy use [19].
This research explores alternative cooling systems that require less energy input, with the goal
of substantially decreasing energy consumption. Solar radiation is plentiful in the UAE, and free to
use. Additionally, preliminary assessments have shown a substantial temperature difference of up to
20 ◦C between the ground temperature (23 ◦C) and ambient temperature (48 ◦C) in the peak summer
months, favoring geothermal cooling system [20 ]. Weather data revealed a yearly solar radiation is
2370 kWh/m2, i.e., 6.5 kWh/m2 per day [ 21 ], which favored the choice of an absorption cooling system,
and photovoltaic energy generation. Geothermal cooling system have also been found promising to
deliver the effective cooling required [21].
The contextual characteristics of the promising renewable energy systems for integration into the
selected school building are summarized in Table 1 [22].
The energy produced by the aforementioned systems is compared to the school’s baseline energy
demand (Table 2), to determine the energy savings and perform the calculation. The predicted energy
savings are then converted into credits earned, based on the PBRS guidelines. The cooling system
performance is compared with the demand in peak months (May–August) in order to determine the
reductions achieved in peak-period cooling capacity and energy use.
Table 1. Renewable energy systems selection in harsh climate.
System/Criteria Advantages Limitations Performance Payback Period versus Life Span
Photovoltaic
system [23]
Annual solar
radiation of
2285 kWh/m2,
expected energy of
850 kW year/m2).
Dust results in radiation
reduction on panel.
High temperature
results in power losses.
Electrical energy
production of
322 kWh/m2-year [24,25].
Pay-back period: 3–5 years [26]
based on unsubsidized tariffs.
Lifespan: 25–30 years.
Solar absorption
cooling system [27,28]
Annual solar
radiation of
182,800 kWh/m2.
High initial cost.
Dust on collectors
results in
radiation reduction.
High temperature
results in power losses.
A cooling energy
production of
1059 kWh/m2-year.
Average payback period:
4–10 years.
Lifespan: 25–35 years.
Geothermal
cooling
system [20,29]
Ground temperature
is used to modulate
interior temperature
(difference up to 20 ◦C
during summer)
High initial cost.
Land required to install
the loop.
Lower temperature
gradient in
moderate seasons.
Cooling energy
delivered by
46 kWh/year-m length
of borehole [30].
Average payback period:
7–10 years according to the
system size.
Life span: up to 50 years.