Elsevier

Energy and Buildings

Volume 158, 1 January 2018, Pages 431-452
Energy and Buildings

The energy and indoor environmental performance of Egyptian offices: Parameter analysis and future policy

https://doi.org/10.1016/j.enbuild.2017.10.035Get rights and content

Highlights

  • General energy survey of Egyptian offices categorised by building service type.

  • Energy and indoor environment performance for a case study office building.

  • Generalisation of the model to represent typical performance.

  • Modelling framework used to demonstrate relative and combinatorial effects of various input parameters.

  • To propose possible future measures for Egyptian office buildings to be encouraged by policy.

Abstract

Buildings are a significant contributor to the rapidly increasing electricity demand in Egypt which is straining the existing supply network causing economic and social impacts. There are current initiatives aimed at improved building performance including adoption of international standards. The performance of existing Egyptian buildings is not well understood making the impact of these international standards uncertain. This paper provides insight into performance of current Egyptian office buildings through a multi-building energy survey and a detailed case study. The most common office type in the survey has natural ventilation and local cooling. A process to capture observed performance in a representative model and input parameter set is presented. The model is used to investigate performance impacts of parameters including: location, weather, building envelope, intensity of occupancy, behaviour, and installed systems including the HVAC strategy. HVAC strategy was identified as the most significant factor. Typical Egyptian offices with natural ventilation and local cooling systems under personal control have electricity demand less than 50% of centrally serviced buildings. System efficiencies (HVAC, lights, equipment) and occupant behaviour (e.g. use of systems, temperatures) were also identified as significant factors, each with potential of around 30% saving compared to current typical offices. Possible policy measures to promote energy efficient systems and energy conscious behaviour are proposed which together can reduce the energy demand of typical offices by 50%. Trade-offs between energy use and indoor environmental quality (IEQ) are discussed.

Introduction

The rapidly growing world energy use raises concerns over supply difficulties, exhaustion of energy resources, and heavy environmental and societal impacts. The global contribution from buildings towards energy consumption, both residential and commercial, has steadily increased reaching figures between 20% and 40% in developed countries. In common with many other nations, Egyptian peak and base load electricity demands have increased greatly, contributing to increasing occurrence of power cuts and blackouts. One key driver for demand growth has been increased urban development concentrated in the Nile Delta [1]. Urban development resulted in particular problems with cooling demands in summer months, associated also with a shift from traditional vernacular designs [2]. New buildings were not required to meet any energy performance standards until 2005 with the introduction of the new code, Egyptian Commercial Buildings Energy Code ECP 306-2005 [3], part of the Egyptian Government integrated energy strategy, aiming to reduce energy demand, and to provide the secure, reliable and affordable energy services in support of economic stability and development [4]. The new codes are largely based on international standards (ASHRAE, ECP) [5], [6]. In parallel there is increasing adoption of voluntary sustainability rating systems such as LEED [7], and a new Egyptian sustainability rating system called Green Pyramid [8].

Potential concerns with the adoption of these new standards are: (i) that the current energy performance of Egyptian buildings is not well known so the change in performance from adoption of these new design standards is therefore uncertain; (ii) that the appropriateness of these new build design standards to the Egyptian context (weather, customs) has not been fully explored; and (iii) that the new standards are not generally being applied to existing buildings which is an essential part of reducing overall demand. To be able to address these concerns, and appropriately inform future strategy, it would appear to be essential to first characterise the energy and indoor environmental performance of the existing building stock and then to encapsulate this performance in a representative model, then to use that model to inform an appropriate future strategy. Many building types make up the stock, in this work, the main focus is on typical Egyptian offices however the methods developed are intended to be equally applicable to other building sectors and contexts.

Various methods have historically been used to represent energy and environmental performance of buildings ranging from statistical black box to detailed physical models Clarke [9], Reedy & Andersen [10], Zhao & Magoules [11], Attia [12]. Modelling of building stocks has variously been approached through bottom up statistical and/or engineering methods, and also top down statistical methods [13], [14]. Statistical methods rely on data being available preferably for multiple individual buildings and disaggregated by energy use and IEQ parameter, and energy use at the stock level. Availability of such data is an issue for the Egyptian office stock. Mauro et al. [15] and Ascione et al. [16] have formulated a bottom up simulation based approach where building categories are established based on geometrical, thermo-physical and ‘other’ parameter sets where ‘other’ covers such parameters as setpoints, people loads, and temperatures which has been used to assess cost optimum building upgrades to inform policy in the context of Italy, uncertainty in model input parameters has been imposed and considered in the outputs.

Dynamic simulation models are increasingly frequently used, these models represent physical behaviour at various levels of detail [17], [18]. Dynamic simulation is used to underpin performance standards such as the EU Energy Performance of Buildings Directive (EPBD) [19] and the UK Building regulations [20] etc. and has been widely used to inform future building strategies [17]. There are many dynamic simulation tools available many meeting internationally agreed standards [21], [22]. In this work the IES-VE 2014 was selected, it has worldwide accreditation and supports numerous regulatory and voluntary standards [23].

For any model calibration is a key requirement for results to be reliable [24]. Calibration processes for building performance models have been a research focus in recent years [18], [20], [25]. ASHRAE Guideline 14-2002 [26], provides standard methods and uses Mean Bias Error (MBE) (%), and Coefficient of Variation of Root Mean Square Error CV(RMSE) (%). In this work a calibration approach based on the ASHRAE Guideline, the work of Coakely [27] and Reftrey [28] is used where a best guess model is constructed based on available data, uncertain parameters are screened for relative influence, then values adjusted sequentially to minimise errors [29].

Measured building performance data is required to inform modelling and calibration processes. There are many building performance datasets available worldwide e.g. UK Probe and Energy Consumption studies [30], [31], US Building Performance Studies [32], These are used to inform model calibration and regulatory compliance tools (e.g. EN15252, UK NCM [33]). It is common practice to categorise office buildings by type e.g. the UK Energy Conservation Guide 19 (ECG 19) [31] categorises offices into 4 types based on form, function, and service strategy, and gives typical and best practice values for different energy use categories. Crawley gives the electricity usage for US offices as ranging between 226 and 317 kWh/m2 p.a [17]. There is limited data for the Egyptian context. Abdelhafez [34] has gathered monthly electric bill data for a single head office in Cairo over 2 years and gives 202 kWh/m2 p.a. as the total annual energy use (all electric) and 162 kWh/m2 p.a. for the office equipment, lighting and HVAC. Ezzeldin [35] modelled cooling strategies for a single prototypical office building in Cairo, Egypt, and gives mixed mode energy use ranging from 70 to 100 kWh/m2 p.a. and central HVAC averaging 170 kWh/m2 p.a. depending on internal gains scenario. The model was based however on many variables like the lighting density, equipment density estimated using standards and codes rather than measured. In general, there is a shortage of measured data for the Egyptian office context.

Measured building performance data is also of key importance in addressing the potential ‘performance gap’ between intended and actual building performance which has been internationally recognised [36], [37], [38], [39]. It would appear to be important in the Egyptian context that performance feedback is integrated in future policy to avoid the performance gaps seen elsewhere.

The use of building simulation tools in Egypt was historically low [40]. The situation is starting to change. There are several recent examples of such tools being used for residential buildings [41], [42], [43], [44]. In the Egyptian office sector ElDabosy and AbdElrahman [45] investigated façade designs for a single office. ElMohimen et al. [46] applied building simulation to study daylighting in a specific Egyptian office building. Ezzeldin [35] examined mixed-mode cooling strategies for an existing modern typical office in Cairo. Saleem et al. [47] examined indoor comfort conditions and energy consumption. Sheta & Sharples [48] used measured data to apply a calibration process for inside room temperature. Hanna [49] used simulation to investigate facades. While these studies provide insights there remain gaps to be able to characterise the performance of existing office buildings in models to support more general policy development.

Non-adaptive and alternative adaptive criteria for thermal comfort are both encapsulated in international standards [50], [26]. The extent to which these apply in the existing Egyptian Office context remains to be explored. Givoni [51] investigated the boundaries of the thermal comfort zone in relation to clothing levels and air movement, noting large shifts in summer comfort temperature. In Japan in 2005, the successful Cool Biz campaign [52] was launched to exploit this effect to reduce energy demand for air-conditioning during summer.

In Egypt, recently multimedia initiatives were launched in the residential sector to raise awareness of users of energy use in buildings. These focused on lighting systems, urging the use of natural light during the day, turning off lighting in unoccupied spaces, and promoted energy-saving bulbs, efficient air conditioners, and setting cooling temperatures to 25 °C. Similar public initiatives have not yet been launched in the non-residential sector.

To develop well founded policy for the office sector in Egypt is necessary: (i) to understand the current energy and IEQ performance of existing Egyptian offices, then (ii) to embed this knowledge within a valid modelling framework, and (iii) to make use of this framework to investigate future scenarios, and (iv) provide outputs that can usefully inform future strategy and policy for the sector. Currently there are gaps in each of these areas with a lack of understanding of current performance, no well-established modelling framework that captures existing performance, and limited parametric studies to usefully inform future policy scenarios.

The specific aims of the research presented here were:

  • To identify the energy and IEQ performance associated with current Egyptian office buildings.

  • To show how this can be embedded in a valid modelling framework.

  • To use this modelling framework to investigate the relative and combinatorial impact of apposite parameters, and to present this information in a useful form.

  • To propose possible future measures for Egyptian office buildings that will minimise energy use.

  • To illustrate a process can be usefully extended to other sectors and contexts.

To achieve this aims the following methodology was used:

  • Evidence was gathered for current Egyptian office energy and IEQ performance from: literature, a building energy survey, and a detailed investigation for a case study office. Thermal comfort standard appropriate to the Egyptian context was investigated.

  • The gathered data was used to create a modelling framework consisting of a typical model, and worst case parameter sets describing likely variations in input parameters.

  • The modelling framework was then used to demonstrate relative and combinatorial effects of various input parameters grouped into appropriate categories and modulated in realistic ranges.

  • The modelling framework was used to investigate the impacts of various parameters and identify those that can be useful to mitigate the growth of energy demand in the office sector and be encouraged by policy.

Section snippets

Existing Egyptian offices: energy performance, IEQ, and behaviors

Evidence was first gathered to establish energy performance of Egyptian offices through a 59 building energy survey and supplementary data from literature. Offices were categorised by their services strategy. A more detailed investigation into energy, IEQ comfort and occupant behaviour was then carried out for a case study office with the most commonly observed service strategy (natural ventilation with local cooling systems).

The building survey, building model, and model calibration are

Modelling framework to represent existing Egyptian offices

In order to inform policy and building upgrades using modelling of future scenarios it was necessary to capture the current energy performance of existing Egyptian offices in a modelling framework. This framework should capture the performance of ‘typical’ offices including the likely range in behaviours and operations associated with the users of the buildings to allow these factors as well as changes in building construction and systems, and variation in weather to be included in assessing

Input parameters for energy and IEQ parametric sensitivity study

The preceding sections described the underpinning modelling framework representing existing type 2 office performance and showed the influence of some key variables identified in the model calibration. A more comprehensive parametric study was then designed to capture variables which had been fixed in the calibration process and also to investigate occupant behaviour in more detail.

To allow the many individual input parameters to be analysed and results displayed in a readily comprehensible

Combinatorial parametric performance analysis

A full factorial of the 729 parameter level combinations was then run using the typical model as base. Fig. 22, Fig. 23, Fig. 24, Fig. 25, Fig. 26, Fig. 27 show various snapshots for Alexandria location. The Y axis represents outputs: total energy use (Fig. 22, Fig. 23); average thermal comfort (summer and winter, Fig. 24, Fig. 25); average CO2 concentrations during occupied hours (Fig. 26, Fig. 27). The vertical range within box-plot represents intensity of occupation. Other input variables

Policy directions for existing type 2 offices?

The most prevalent type 2 office type was used as the base for the parametric analysis represented in Fig. 29 and Table 9. The feasible changes that could most effectively reduce energy use are system efficiencies and behaviour changes.

By referring to Table 9 it is apparent that the typical type 2 office in Alexandria has annual electrical demand of 40.4 kWh/m2, this demand could be reduced to 29.3 kWh/m2 (27% reduction) if the energy conscious behaviour were adopted, alternatively the demand

Discussion

The overall aim of the work presented here was to explore the energy and indoor environmental performance of Egyptian offices and provide insights that can begin to usefully inform future strategy for this sector.

This paper elaborates the steps taken in this exploration: the 59 office energy survey, the single building energy and environmental monitoring, the creation of a representative modelling framework, and the use of that framework to provide further insights beyond the survey and

Conclusion

Insights into the current performance of Egyptian office buildings is provided through a 59 building energy survey plus investigation of a case study of the most commonly found type which has natural ventilation and local cooling systems.

Office buildings were categorized into 4 types by servicing strategy: natural ventilation with no cooling, natural ventilation with local cooling, mechanical ventilation with local cooling, centrally serviced mechanical ventilation and cooling and energy use

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