استفاده از انرژی و پتانسیل فنی برای اقدامات صرفه جویی انرژی در انبار ساختمان های مسکونی سوئدی

This paper provides an analysis of the current energy usage (net energy and final energy by fuels) and associated carbon dioxide (CO2) emissions of the Swedish residential building stock, which includes single-family dwellings and multi-family dwellings. Twelve energy saving measures (ESMs) are assessed using a bottom–up modeling methodology, in which the Swedish residential stock is represented by a sample of 1400 buildings (based on data from the year 2005). Application of the ESMs studied gives a maximum technical reduction potential in energy demand of 53%, corresponding to a 63% reduction in CO2 emissions. Although application of the investigated ESMs would reduce CO2 emissions, the measures that reduce electricity consumption for lighting and appliances (LA) will increase CO2 emissions, since the saved electricity production is less CO2-intensive than the fuel mix used for the increased space heating required to make up for the loss in indirect heating obtained from LA.

In addition to its obligations under the Kyoto Protocol agreement1, the European Union (EU) is committed to reducing its overall greenhouse gas (GHG) emissions by at least 20% by 2020, as compared with the levels in 1990. Based on bottom–up studies, the IPCC (2007) has calculated and shown that the building sector, among all the sectors examined, currently has the greatest potential for low-cost carbon dioxide (CO2)2 mitigation in the short- to medium-term through the application of technological options. Despite the large potential, the energy usage and associated CO2 emissions of the building stock in the EU continue to grow. Since turnover of the building stock is low in developed countries, the main opportunities for energy efficiency and GHG emission reduction arise from retrofitting the existing stock (Dineen and Ó Gallachóir, 2011). Thus, there has been a shift in focus from optimizing the efficiency of new buildings to efficiency measures that are applicable during the refurbishment process (Bradley and Kohler, 2007 and Balaras et al., 2007). Nonetheless, much work remains to be done to assess systematically the potential and costs associated with applying energy saving measures (ESMs) for entire building stocks, e.g., the stock of an entire country (Ürge-Vorsatz et al., 2009 and Kavgic et al., 2010). Such type of work requires both a description of the building stock and the development of modeling tools to assess the effects of ESMs. The work presented in this paper is part of a larger study (Pathways to Sustainable European Energy Systems; see Johnsson, 2011) and is developing a methodology for assessing ESMs for the European building stock. The aim of the present study is to assess the effects of applying a set of ESMs to all residential buildings in Sweden. In the 1990s, the investment costs and opportunities for energy efficiency in the Swedish building stock were calculated by the Swedish National Council for Building Research, BFR (Byggforskningsrådet in Swedish) (1996). They used the MSA model (BFR, 1984 and BFR, 1987) for residential buildings and the ERÅD model (Göransson et al., 1992) for commercial buildings. BFR (1996) also considered how the potential for ESMs could be achieved up to the year 2020, including new buildings that had yet to be built. However, these two models (MSA and ERÅD) are not readily available. Current goals for the reduction of energy use in buildings in Sweden, as stated in the program of the Swedish Environmental Objectives Council (Miljömålsrådet in Swedish), are given as 20% less net energy usage per heated floor area by the year 2020, and 50% less consumption by the year 2050, both relative to the reference year of 1995. To begin to address these targets, the Swedish National Board of Housing, Building and Planning (Boverket, in Swedish) carried out in 2005 a field study (Boverket, 2009) that focused on the building stock in terms of energy usage, technology status, indoor air quality, and maintenance.3 This study was facilitated by data from a high number of sample buildings, chosen as representative of the Swedish residential building stock. Some of the work presented in this paper was initially performed as part of a study commissioned by Boverket, which had the aim of evaluating net energy potential savings in the existing Swedish residential buildings, and those results have been published in part (Boverket, 2009 and Boverket, 2010). The work presented in the present paper advances the initial work and has the following aims: (a) to describe in detail the current energy usage of Swedish residential buildings, and (b) to assess ESM with respect the technical energy savings associated with implementing the measures in the Swedish residential stock. In addition, the paper provides a brief comparison of the cost-effectiveness of the ESMs investigated. The assessment includes all end-uses, i.e., space heating, hot water, and electricity (for lighting, appliances, and cooking). The present paper starts with a brief description of the Swedish energy system and of energy usage in the residential stock, based on energy data from statistical databases. Thereafter, the information on the present Swedish stock (from statistical sources) is complemented with the results of the modeling, in which the building stock is characterized in detail (using the parameters of net energy, final energy, and CO2 emissions), together with the data disaggregated into Single-Family Dwellings (SFDs) and Multi-Family Dwellings (MFDs). Finally, the paper presents technical potentials for energy savings and reduction of CO2 emissions as identified from the modeling.

The current energy use of the Swedish residential building stock (represented by 1400 sample buildings) is presented with respect to size (number of buildings and areas), energy use (net energy and final energy by fuels), and associated CO2 emissions to which a number of energy saving measures (ESMs) is applied. The results are disaggregated for SFDs and MFDs. It is shown that application of the selected ESMs has the potential to reduce the final energy demand of the Swedish residential sector by 53%. The measures that provide the greatest savings are those that involve heat recovery systems and those that involve a reduction of the indoor temperature, giving energy savings of 22% and 14%, respectively. Upgrading the U-values of the building envelope and windows would each provide annual energy savings of 7%. These results are average values for Sweden, which means that before policy or investment decisions are taken at any other organizational level other than the national one, the results should be examined in greater detail. The modeling outcomes could also be scrutinized for each climatic region and for different types of buildings. In addition, the above-listed potentials are to be seen as technical maximums, and further work is needed to clarify how these potentials could be achieved and to identify a robust approach to implementing these measures. The level of CO2 emissions from the Swedish building sector could be reduced by 63% by applying all the ESMs studied. However, the levels of emissions from the Swedish building sector are already low (10% of the total emissions for the country), and allocating the costs of the ESMs to reduce CO2 emissions gives high abatement costs (per ton CO2 avoided). Therefore, emission reduction is not likely to provide the main impetus for imposing energy efficiency measures. Rather, the profits gained from energy efficiency measures and indirect effects, such as reduced dependency on electricity (which may give indirect reductions in terms of CO2 emissions), are strong motivations for implementing the ESMs. Although the application of the ESM would generally reduce CO2 emissions, the measures that would reduce electricity use for lighting and appliances would increase CO2 emissions because the saved electricity production is less-CO2-intensive than the fuel mix used for space heating. Therefore, it is not recommended to take decisions based solely on energy or CO2 assessments. At the same time, one should look at the implications of the ESMs in terms of final energy for the entire energy system.