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Energy in Sweden
Final energy use in Sweden can be divided into three sector users’ which are industrial, transport and residential and service sectors. Industrial sector uses biofuels and electricity while transport sector mainly uses oil products such as diesel, petrol and aviation fuel. The residential and service sector use of energy based on district heating, electricity and biofuels or oil [3]. In 2013, the final energy use in total for all sectors accounted for 375 TWh. Residential and service sector and industrial amounted for 174 TWh and 144 TWh respectively, while energy usage in transport sector accounted for 85 TWh, as represent in Figure 1-1. Energy use in residential and service sector is affected in short-term basically by outdoor temperature which implies large proportion of energy usage for heating purpose.
Energy use in buildings
In 2004, Buildings accounted for 37% of final energy use in Europe, higher than industry (28%) and transport (32%). In UK, 39% was the portion of energy use in buildings, slightly higher than European figure. This is due to move away from heavy industry towards activities in service sector. The figure in Spain was 23% of the final energy use in buildings, but it’s expected to rise as result of economic growth. Service sector in USA energy usage has extended from 11% to 18% from the 1950s [1].
In Sweden, Service and residential sector amounted for almost 40% of Sweden entire energy use. Non-residential buildings and households accounted for around 90% of the energy use in this sector and energy use for hot water and heating for them equalled to 80 TWh, which is 55% of the whole energy use within the sector; the most common form of energy to fulfil these purposes is district heating with consumption of 18 TWh [3]. Building and transport sector are responsible for the highest energy consumption and greenhouse gas emissions within EU and they are not cover by emission trading scheme (ETS). This show important need for effective measurement in these two sectors to mitigate the environmental climate change challenge. The building sector, because of both its energy demand and the long useful life of buildings make it the most critical between these sectors. [4].
Buildings sector has good opportunities to minimize energy usage by improvements in operation, design and renovation technology. 73% of energy consumption for north European household is related to heating system which represent the biggest part of the total energy usage. Therefore, energy efficiency measures in heating system has a high potential for energy usage reduction [5]. To find out energy efficient measures to be implemented in a specific building requires the analysis of energy flow of a building which is the main aim of the energy audit [6]. In Europe, educational buildings represent 20% of the whole non-residential floor space. The school sector uses high portion of energy for heating and electricity, therefore improving energy efficiency is essential. Schools final energy use in USA, UK and Spain amount for 13%, 4% and 10% of the total energy use respectively. Moreover, electricity energy usage patterns in schools have changes considerably in the last decades due to increasing of using computers for educational purposes, 71% increase of computers number per square meter. Good indoor comfort and air quality are important for right educational development bearing in mind the long periods that students spend in schools, so achieving suitable comfort levels is considered necessary. This mean acting on the existing educational buildings is vital, not only to accomplish the EU 2020 targets but also to enhance the educational performance of future generations [7]. As this thesis is performed on commercial building (school buildings), the study [8] demonstrate the key possible retrofit technology that can be applied in such buildings. These technologies can be grouped in three categories which are supply management, demand management and change of energy usage patterns, i.e. human factors. For the demand side management, it includes retrofit technologies and strategies to decrease building heating and cooling demand, usage of energy efficient equipment and low energy application. Retrofitting of building envelope and use of advanced technologies such as windows shading, air tightness, etc are used to reduce building heating and cooling demand. low energy technologies might include heat recovery, natural ventilation, advanced control schemes, etc. The supply side include retrofit technologies such as photovoltaic system, solar collectors for hot water, wind energy, etc.
Literature Review
This literature review will demonstrate the main goal of this research, which is decreasing the energy usage of Fridhemsskolan buildings located in Gävle through energy audit. Both the important of the energy audit and how it can be done will be determine in this literature review also. Furthermore, this study within this literature review will focus also in the aim and objectives of this research which is illustrated in more details in the next section (1.5) of this study. key words such as energy audit, energy efficiency, retrofit, commercial building energy and energy trends were used for searching for peer reviewed articles and journals to conduct this literature review. The previous presented statistics in the background section show the importance of the building energy usage reduction which is considered as priority indicated in European Directive 2010/31/EU (EU Parliament 2010) and according to the Energy Efficiency Plan of the European Commission (2011). Although energy use figure for buildings is high; building sector have the greatest energy – saving potential [9]. Between public buildings types, a wide stock classified by a continuous use is the ones built for learning activates and they are affected by high energy usage due to internal environmental quality required for young people. However, to reach an accurate retrofit at any level; first it is important to perform an energy audit to identify the feasible interventions for the energy use reduction possibilities and their costs [10], this was also mentioned in the study [11] which states: “An energy audit is a key feature of successful management of the energy issue in any building, as it represents a starting point for implementing energy issues in management procedures. An energy audit aims at assessing the present energy situation in a building.” The previous literature show the value of this research and why it’s worth performing energy audit for buildings to achieve overall EU target for 2020 which aim for 20% reduction in greenhouse gas emissions, 20% increase in renewable energy sources’ share of final energy consumption and 20% increase in energy efficiency over 1990 levels. When energy audit is performed for buildings, the heat balance components of buildings should be studied and measured [11]; these components are: • Transmission through wall, roofs and floors. • Ventilation. • Infiltration. • Internal Gains from equipment, people, lights, etc. Study [12] illustrated results obtained by performing energy audit on the faculty of engineering department building in Jordan. The study proposed energy efficiency measures regarding the lighting which are replacement of used lights by energy efficient lights, using occupancy sensor and dimmers which are devices used to control the brightness of the light. Applying these measures will lead to 20% to 40% energy saving in the electricity for each measurement of them. Furthermore, by replacing of single pane glass windows with double glass windows will reduce heat loss through building envelope by 10% to 12%, and the fact that around 60% of heat losses occurs through the standard single pane windows. The last measurement will lead to significant saving in the heating bills. Other studies showed great results from energy auditing of buildings e.g. study [9] which performed on teaching building of the Faculty of Economics of the University of Coimbra concluded that by applying the proposed energy measures after the energy audit a reduction of 26 MWh/ year in the electricity could be achieve, equalled to (€2663/year) and at the same time an amount of 3,704 kg CO2/year will be prevented. Another case study [6] of energy audit for a Portuguese school building based on the information collected during the audit, some energy efficiency measures were identified that can be applied in the school building. Those founded measures were related to electricity and involve control equipment, efficient lights, power factor improvement and optimization of electricity contract with the supplier. Implementation of the identified measures will result in decreasing the electricity usage in the building around 31, 100 kWh/year which is equals to annual drop of 14, 620 kg CO2e and saving of 28% of the yearly electricity bill which is around 4, 000 €. Furthermore, suggestion about evaluation and analyse of other efficiency measures like integration of solar collectors for hot water and changing of existing taps by efficient ones with a regulator to decrease water usage.
Study of [13] simulated educational building using dynamic software (TRNSYS 17) to model the whole building components such as building envelope, school students occupancy profile and HVAC system. The study reported that the dynamic model of the school is the best tool to achieve a comprehensive analysis of an energy saving measure. For this reason, an approach to improve energy performance of the building was evaluated by way of the developed dynamic model. Finally, the proposed retrofit focused on the heating system renovation instead of building envelope improvement because of high price of the external insulation and replacement of widows, due to large external area and windows number in the school. Results showed that using air-source heat pump instead of boiler decrease the primary energy need for heating by 46%. The same pervious dynamic model was also used in study of [14]to enhance the energy performance of secondary school building in Italy. By analysing the actual condition in terms of energy use, measures were addressed to enhance both air tightness and building envelope insulation. The measures applied to the model were installation of new windows with lower U-value (1.2 W/m2 K), installation of heat recovery for the ventilation system (0.7 sensible effectiveness) and internal insulation of the roof and attic floor. Combination of building envelope measures alone (new windows and insulation) entails 44% reduction of heating consumption. Many studies were performed on educational buildings for both energy and indoor environment quality (IEQ). Study published by ref [15] in Luxemburg presents the result of an energy use analysis and savings potential on 68 school buildings. The study exposed that simple retrofits as insulation and air tightness can decrease the energy demand. The author estimates saving of 1% of the national fuel oil and gas consumption annually. Study of [16] showed an energy audit results performed on 135 Hellenic school’s buildings and analysis of several energy conservation refurbishments while maintaining acceptable IEQ. The analysis showed that 63% of the buildings were not well insulated while just 23% had 2 pane glazing windows. The study also revealed that 24% and 22% were concerned by enhancement of the heating and lighting systems respectively. Furthermore, retrofit of existing school building in Italy was implemented by study of [17] within framework of “the School of the Future project, funded by 7th Framework Programme”. The main objective is to demonstrate the technical and economic feasibility of major energy renovation to improve the energy performance of the existing building stock. The founded measures involve façades and roof external insulation, insulation of part of the ground floor, windows replacement with external shading device (moveable), renovation of the whole heating system, remote energy management system design and installation for the municipality schools, PV plant installation on the roof and mechanical ventilation system for classrooms. The last measure was implemented to satisfy the IEQ requirement. Implementation of the insulation and windows replacement on the west and north oriented façades resulted in decreasing actual energy use required for heating purposes by 42%.
Investment on energy efficiency measures involve large number of factors. The choice of retrofit measures is balance between benefits that can be gained due to implementation of the retrofit measures and capital investment. Economic analysis can facilitate the comparison among different retrofit measures, it can identify also which alternatives are energy efficient and cost-effective. A diversity of economic analysis methods can be used to for the purposes mentioned previously. Some of them are net present value (NPV), Benefit-cost ratio (BCR), Overall rate of return (ORR), Internal rate of return (IRR) and Simple payback period (SPP) which can be used to assess the economic feasibility of one retrofit measures. The most used one to make a decision is the pay-back period which was used in this research to evaluate the proposed energy efficiency measurements and prioritise them accordingly [8].
Building retrofit effectiveness depend on building- specific information like building type, age, size, geographical location, energy sources, building envelope, occupancy schedule etc. for a specific project. Another important element that affect building retrofit success is human factors; some studies showed that 10 -20% of domestic use of energy in Nordic countries can be reduced from occupant behaviour changes only [8].
All the studies presented in this literature review illustrates that there are great opportunities to reduce energyuse in school buildings through energy audit. Energy audit allows identification of possible measures and retrofit technologies to achieve the goals of this research.
Aims and Objectives
The overall aim of this thesis is to perform an energy audit using IDA-ICE software to simulate energy performance of Fridhemsskolan buildings to find the reason behind the high-energy consumption, then to propose energy efficiency measures to achieve the goal of reducing the energy usage in the school buildings. The study was proposed by Gavlefigheter company which manages and owns real state for trade, industry and municipal activates in Gävle.
Table of contents :
1 Introduction
1.1 Background
1.2 Energy in Sweden
1.3 Energy use in buildings
1.4 Literature Review
1.5 Aims and Objectives
1.6 Case study building – Fidehmskolan
1.7 Approach
2 Theory
2.1 Energy Audit
2.2 IDA-ICE
2.3 Building Energy Balance
2.4 Heat Transfer
2.4.1 Conduction
2.4.2 Convection
2.4.3 Radiation
2.4.4 U-value
2.5 Ventilation System
2.6 Energy condition of Fridhemskolan
2.6.1 Energy Prices
3 Method
3.1 Materials
3.2 Procedures
3.2.1 Data collection and on-site measurements
3.2.2 IDA-ICE baseline models building
3.3 Assumptions and limitation
3.4 Validation of the baseline models
3.5 Energy Balance and energy saving measures
4 Results
4.1 Validation Baseline models’
4.2 Energy Balance
4.3 Baseline models Thermal comfort
4.4 Energy Saving-measures
4.4.1 Scenario 1
4.4.2 Scenario 2
4.4.3 Scenario 3
4.4.4 Scenario 4
4.5 Extra Saving
4.5.1 Air Curtains
4.6 Energy saving measures impact on thermal comfort
4.7 Economic assessment
5 Discussion
5.1 Method and IDA-ICE models
5.2 Results
5.2.1 Energy saving-measures and profitability
5.2.2 Thermal Comfort and CO2 level
6 Conclusion
6.1 Outlook
7 References
8 Appendix
