Climate change is considered an important global threat, with a significant impact on the energy performance, since buildings will be subjected to higher average outdoor temperatures. This paper explores the relative impact of global warming across the different regional climates of Europe comparing present and estimated future energy needs of a hypothetical residential house located in 19 cities characterized by different latitude and Köppen-Geiger class. Building performance simulations with EnergyPlus are performed in order to simulate the heating and cooling needs of the building and the associated CO2 emissions in the present and in the future. The progressive increase in average temperatures in 2050 and 2080 leads to a general decrease of thermal energy request for heating and to an increase in the demand for electricity for cooling especially in the southern Europe, where high carbon intensity coefficients cause large CO2 emissions. The resulting vicious circle can be interrupted by increasing the energy efficiency of buildings and properly converting thermoelectric power plants.
The Earth is experiencing a rapid climate change whose effects are occurring with an average
warming of the atmosphere happening in a relatively short period of time
Currently, around 30% of global energy production is earmarked for end-use in the civil sector
Energy needs are strongly linked to local weather conditions
The international scientific community dealing with energy demand of buildings is analysing
the close relationship between climate change, energy demand and greenhouse gas emissions
On the first point, Moazami et al. worked to create a robust dataset of climatic information
representing the future climatic conditions, in particular for the city of Geneve (Switzerland),
according to the peculiarities of the analyzed area and to different scenarios of global warming
Regarding the second point, Invidiata and Ghisi showed significant percentage increases (even
180%) of the annual energy needs of the buildings considered in three Brazilian cities
With reference to the third point, Wan et al. studied 5 Chinese climatic areas in order to identify
technological solutions able to counter balance the increase in the buildings energy needs and
the consequent emission of CO2
Among the potentialities of computing techniques, the predictive simulation of the heat exchange phenomena between the environment and buildings allows engineers to predict future energy needs in the building sector in ever greater detail and precision. In the last few years, software simulating the energy performance of more and more detailed and complex buildings in a dynamic regime, have allowed to face the technological challenge to design increasingly more efficient buildings. Now the attention of the scientific community is shifting towards the prediction of the buildings energy resilience to changes in local climatic conditions due to global warming. In order to create weather files representative of future climate scenarios, suitable climate models must be implemented. Then, starting from historical meteorological data, annual database files can be created that can be used with dynamic simulation software for the analysis of energy performances of buildings. This is possible thanks to the computerization of knowledge provided by climatology and energy engineering. This work aims at assessing the impact of climate change of annual energy consumption for heating and cooling across Europe of a model building, located in 19 European cities characterized by different Köppen-Geiger classification. To this end, dynamic hourly simulations were performed for each location with the EnergyPlus software, using alternatively the weather files provided with EnergyPlus for the current climate, and those relative to two future years (2050 and 2080) under a predetermined emission scenario, created for each location. In this way, it is possible to study the relative change attributable to climate change on the future energy needs of a building and on the relative carbon dioxide emissions of a building for residential use in Europe. In particular, the choice of using one and the same building allows to highlight the impact of the climate change on the energy needs across different Köppen-Geiger climate zones. A future development of this work could take into account the variation of construction types across the continent.
In this work, the dynamic predictive software EnergyPlus was used to evaluate the energy
consumption of a building alternatively located in 19 European cities, selected according to the
(different) latitude and the climatic Köppen-Geiger classification
The analyzed type building was specifically designed to provide useful information during the energy analysis phase. The 3D geometry was created in SketchUp and through the OpenStudio tool it was provided as input to Energyplus.
The EnergyPlus software was developed by the US Department of Energy
The EnergyPlus software needs to load a weather file (.epw format) containing hourly weather
information of a typical year for the selected location
In this work the weather files available in the EnergyPlus database were used for the “current
climate” simulations, while the “future climate” simulations are based on climate change
weather files produced using the Climate Change tool World Weather file Generator
(CCWorldWeatherGen). The generation of this future file weather required computational
techniques based on climate models able to provide detailed meteorological information
decades apart, specific to the geographic location, for the 8,760 hours of the typical year. The
National Renewable Energy Laboratory (NREL) of the US Department of Energy (DOE)
provides online ("Weather Data | EnergyPlus") EnergyPlus users with a comprehensive climate
database that includes more than 2,100 geographic locations on all continents. The EnergyPlus
database weather files were also used to create climate change weather files for 2050 and 2080
and all the 19 selected locations through the CCWorldWeatherGen tool. This tool creates a
weather file starting from the current climate weather file by means of a "morphing" procedure
and using the HadCM3 model output corresponding to the A2 emissions scenario (more
properly, the A2 scenario family) of the IPCC Third Assessment Report. According to the IPCC
definitions, such scenario family is characterized by “a very heterogeneous world with
continuously increasing global population and regionally oriented economic growth” more
fragmented and slower than in other scenarios
This study took into consideration 19 different cities of Europe. The geographical sites have
been chosen according to: i) the latitude, on which the solar radiation depends; ii) the climatic
classification according to Köppen-Geiger
Climatic Classification
ET Dfb Dfb Cfb Dfc Cfb Dfb Cfa Csa Cfa Csa Csb Dfb BSk Bsk Dfb Cfb
Carbon intensity
[kg(CO2) kWh-1]
0.3701
0.3758
0.1666
0.0348
0.0348
0.0348
0.4249
0.2292
0.2292
0.2292
0.2292
0.3595
0.2085
0.3044
0.3044
0.0105
0.3888
56.4
54.5
It is hypothesized that the amount of carbon dioxide produced for the generation of electricity
is constant over time and refers to current values
A residential building consisting of three floors and three apartments for each floor was taken as a case study. The first floor is raised on pillars with respect to the ground; the intermediate level exchanges heat towards the outside only through its vertical infill panels; the upper floor is characterized by a flat roof. The air-conditioned interior floor area is 765.6 m2. The height of each floor is 3 m. Two apartments have a common border area, while the third apartment totally adjoins the exterior or the landing and the stairwell that are unheated. Fig. 1 shows the plan of a plane, a 3D and the geographic orientation of the building.
Properties of materials of building envelope surfaces are summarized in Tab. 2. The building is heated by radiators connected to a condensation boiler powered by natural gas and characterized by efficiency of 104.8% and 107.2% when the nominal power is equal to 100% and 30% respectively. Cooling takes place through split-type steam compression refrigeration systems characterized by C.O.P. equal to 3.1. To simulate the activation of the plants and calculate their energy requirements, an internal temperature has been assumed: i) greater than 18 °C, in heating; ii) less than 26 °C, in cooling. The ventilation of the rooms is natural, with a turnover equal to 0.5 hourly volumes. Internal thermal loads are assumed to be equal to 38 W m-2.
The few geographical locations that in 2020 present the coldest winters (such as Cluj-Napoca and Gothenburg, with average temperatures below 0°C) have milder seasons in 2050 and 2080. Some Mediterranean locations, such as Granada and Palermo, have extremely high average temperatures in the summer months (which in 2050 go well beyond 30 °C). Some cities in northern Europe (e.g. Aberdeen or Belfast) do not have large needs for summer cooling of the building as they have relatively cool summers. And since heating needs are there cut due to climate change, the annual energy needs are reduced. All this leads, in general, to a lower consumption of thermal energy for winter heating and to an increase in the demand for electricity for summer cooling through the steam compression refrigeration machines.
Annual CO2 emissions respectively for cooling and heating the studied building are computed multiplying the annual energy consumption (in Fig. 3) for the carbon dioxide emission coefficients due to the production of electricity (fifth column of Table 1, corresponding to the national energy mix of each State) or to the stoichiometric combustion of natural gas (Fig. 4). Figure 4 shows that there are three opposite trends in terms of annual carbon dioxide production in the future and the 19 cities can be divided into three groups according to their trend. The first large group consists of cities with a cold climate (Aberdeen, Belfast, Bordeaux, Clermont, Copenhagen, Gothenburg and Paris), where emissions tend to decrease globally; the second large group is made up of cities (Berlin, Granada, Milan, Palermo, Pescara, Plovdiv, Porto, Rome and Salamanca) where CO2 emissions tend to increase. The behavior of these two groups can be explained as follows: i) the decrease in energy demand for heating favors the reduction of CO2 emissions; ii) reduced cooling needs for the northern Europe locations, associated with their low carbon intensity coefficients, correspond to little carbon dioxide emissions for cooling; ii) large quantities of electricity for cooling in the cities of southern Europe, associated with their high coefficients of carbon intensity, give rise to the production of CO2. The third, small, group of cities is formed by Cluj-Napoca, London and Prague and shows a decrease in annual CO2 production from 2020 to 2050 and a trend reversal from 2050 to 2080. This is because in the medium temporal term there is an important decrease in energy needs for heating in the winter months, but these savings are counterbalanced by a large increase in electricity for summer cooling. It can be deduced that the decrease of natural gas demand for winter heating at many sites is neutralized by the increased demand for electricity (for summer cooling). Since to date only France, Sweden and Denmark have a value of the carbon intensity related to electricity generation lower than CO2 emissions related to natural gas combustion, the trend observed above involves the increase in the emission of greenhouse gases into the atmosphere. Therefore, it is necessary, for the purpose of climate change mitigation, to find more environmentally friendly solutions such as the conversion of large thermal power plants for electricity generation.
In the last 20 years major efforts haves been made to reduce energy consumption in the building sector, especially for private homes for residential use. The owners energetically redevelop the apartments little and very slowly and the old buildings are not replaced by more modern and efficient buildings. Long awareness campaigns have been conducted, but it is not enough. In the meantime, in fact, the global climate is undergoing major changes and the expected future warming of the Earth surface will lead to new scenarios.
Focusing on the European scene, in the next 60 years the homes will change their energy demands according to climate changes and the geographical position will play an important role in this evolution of energy needs. In fact, the energy needs linked to winter heating tend to decrease, while consumption related to summer cooling are expected to increase, especially in southern Europe. This will result in a reduction in the quantity of fossil fuels (such as natural gas) combusted for heating and, at the same time, in the increase in electricity demand used to power compression refrigeration machines. Specifically, this study highlighted how the future climate change, compared to current conditions, could lead to a decrease in the winter heating requirement of northern European cities such as Aberdeen (-31% in 2050 and -45% in 2080), Gothenburg (-24% in 2050 and -36% in 2080) and Copenhagen (-28% in 2050 and -41% in 2080) and an increase in the summer cooling requirement of southern European cities such as Rome (+143% in 2050 and +272% in 2080), Palermo (+70% in 2050 and +142% in 2080) or Granada (+129% in 2050 and +238% in 2080). Comparing the energy demands of 2080 with the present one and taking into account all the examined European cities at the same time, the increase in energy needs for cooling will be higher than the decrease in energy needs for heating. Therefore, this would increase global energy consumption.
Assuming that the current carbon intensity coefficients are conserved in the future, European
countries producing electricity mainly from fossil fuels will contribute to increasing the levels
of greenhouse gases in the atmosphere, responsible for the increase in the average temperature
of the earth. This vicious circle can be interrupted mainly thanks to two different strategies to
be implemented on a large scale and thanks to appropriate investments: i) increasing as much
as possible the energy efficiency of the existing building stock; ii) converting large thermal
power plants to supply sources with reduced emissions of climate-altering species into the
atmosphere
These results are the first step in a research work aiming at using optimization computational techniques such as genetic algorithms. The goals of the next steps will be the identification of the best energy efficiency upgrading of buildings in order to mitigate the effects of global warming and reduce energy demand and emissions of greenhouse gases to the atmosphere. With the definition of future scenarios on a large scale (and not only at European scale as in this study), taking into account the new energy needs of the building sector, the costs of energy sources and the modification of the energy mix for the electricity production in each nation due to climate change, the energy production sector and therefore the energy market can be reorganized.
Ferdinando Salata, Virgilio Ciancio and Iacopo Golasi have received for this research a grant on the "Progetti di Ricerca - Progetti Medi 2018” from Sapienza University of Rome. Energy Statistics. (2017).