Konstadinos Abeliotis,Konstantia Founta

School of Environment,Geography and Applied Economics,Harokopio University,El. Venizelou 70,17671,Kallithea,Greece

Keywords

Abstract

1 Introduction

A heat pump is a mechanical device used for heating and cooling,which operates on the principle that heat can be moved from a warmer to a cooler temperature(Huang and Mauerhofer,2016). Heat pumps utilise sustainable heat sources such as air and ground heat. They are utilised for domestic and commercial heating and cooling(Chua et al., 2010); moreover they are utilised for water heating (Eicher et al., 2012; Hepbasli and Kalinci,2009). Heat pumps are also utilised in many industrial processes (Chua et al.,2010). A subdivision of the heat pumps, are the geothermal heat pumps. A geothermal heat pump or ground source heat pump (GSHP) is a central heating and/or cooling system that pumps heat to or from the ground to provide heating,air conditioning and,in most cases,hot water(Self et al.,2013).

Several studies have demonstrated that heat pumps may drastically reduce GHG emissions,especially those of CO2,during space heating and heat generation(Chua et al.,2010;Rivoire et al.,2018). For instance,Chua et al. (2010)report that a heat pump generates 2,038 kg CO2/y,an amount which is less than half compared to the typical boiler systems(Chua et al.,2010).

In the following lines, the assessment of the environmental impacts of the life cycle of heat pumps will be reviewed based on recent literature. Blom et al. (2010)compare the use of heat pumps with gas-fired boilers for the heating of dwellings in Netherlands via means of LCA.The authors came up with the conclusion that a heat pump is actually not more environmentally friendly than a gas-fired boiler. Rey Mart´ınez et al. (2011)compare a ceramic evaporative cooler with a heat pump in two climate areas of Spain. The authors conclude that electricity is the main environmental burden for the heat pump,together with its infrastructure. Eicher et al. (2014)utilise LCA in order to compare the use of a solar heat pump to produce domestic hot water and space heating for single family dwellings in Switzerland against two other residential heating technologies. The authors conclude that the environmental impact due to the materials of the heat pump is not negligible when compared to the impacts of the operational electricity use,especially when the electricity results from renewable energy sources,such as photovoltaics. Huang and Mauerhofer(2016)utilise a life cycle approach in order to assess the sustainability of a GSHP in Shanghai,China.

Koroneos and Nanaki (2017) examine via means of LCA a closed loop GSHP system, which covers the heating and cooling demands of a building in the city of Thessaloniki, Greece. The authors conclude that the environmental impacts are mainly attributed to the production of raw materials and to the operation of the system.Therefore, the aforementioned studies have identified that the upstream to the heat pump operation stages are environmentally burdensome(Eicher et al.,2014;Huang and Mauerhofer,2016;Koroneos and Nanaki,2017).

Chang et al. (2017)examined the life-cycle energy consumption and environmental performance of geothermal heat pump deployment in China using a university building as an example. The authors concluded that the application of heat pumps provide 84% and 83% reductions for heating and cooling respectively, compared to similar buildings that use municipal heating and air conditioner cooling.

Moore et al. (2017)examined the environmental performance of heat pump water heating systems in Australia. Utilising streamlined LCA, the authors found that due to their higher efficiency heat pump hot water systems can result in significantly lower GWP than electric storage hot water systems.

Rivoire et al. (2018)present a modeling study for groundwater heat pumps in different building typologies and climates across Europe. The authors concluded that geothermal heat pumps reduce the primary energy consumption by 33–75% and the CO2emissions by 27–56% with respect to conventional heating and cooling technologies.

In order to identify the hotspots of the manufacturing of an air/water heat pump,the aim of this manuscript is the presentation of the environmental impact assessment resulting from the assembly, transportation from Italy and installation of the heat pump in Athens, Greece. Operation of the heat pump is not included in the assessment.

This type of air/water heat pump is utilised in central ventilation systems of large buildings but also in industrial settings for the generation of hot and cold water. Heat pumping or rejection is performed by air via the utilisation of an air-cooled evaporator/condenser. Then, the refrigerating fluid is exchanging heat with a secondary water circuit via the utilisation of a water-cooled condenser/evaporator.

2 Methodology

The LCA methodology is applied according to the requirements provided by the ISO14040(2006)and ISO14044(2006)standards. LCA is composed of four major stages: goal and scope definition,inventory analysis,impact assessment,and interpretation(ISO14040,2006).

Goal and scope definition

The goal of the study is to estimate the environmental impacts caused by the construction and assembly of the parts,packaging and installation of a typical 7.5 KW air/water heat pump constructed in Italy and transported to Greece where it is installed. The scope of the study includes the construction of the heat pump,its packaging,its transport from Italy to Greece and its installation. The key components of the heat pump are: (i)the electrical resistance,(ii)the case,(iii)the rotary DC inverter technology compressor,(iv)the control system and(v)other parts of the pumps,such piping, expansion valves, and refrigerating fluid. Moreover, for the installation of the air/water heat pump,66 m of pipes were used.

The life cycle stages included in the scope of the study are presented in Figure 1.

Functional unit

Fig.1 Life cycle stages of a heat pump.

The functional unit is defined as 1 piece of heat pump installed. The total weight of the heat pump is 120 kg(packaging included).

System boundary

The life cycle of the heat pump under investigation starts in Italy,where it is constructed and assembled and ends up in Athens,Greece where it is installed. The life span of the heat pump is assumed to be 20 years.

The aim of the current manuscript is the presentation of the life cycle assessment of a 7.5 KW air/water heat pump fabricated and assembled in central Italy and installed in the greater Athens area in Greece. The fabrication,assembly,packaging,transportation,and installation life cycle stages of the heat pump are examined.

3 Life cycle inventory

For the technical specifications and the material and energy inputs for the heat pump assembly and fabrication,technical manuals and brochures are utilised. For the transportation data,the logistics company was contacted.Finally,for the installation phase,the technician who made the installation was contacted.

Heat pump assembly

Various key components are assembled together to compose the heat pump. These components are produced and assembled in the same factory, located in central Italy. More specifically, the heat pump consists of the following five components: (i) case, (ii) compressor, (iii) control system, (iv) electric resistance, and (v)miscellaneous other parts. Overall, the interior unit of the heat pump weighs 71.4 kg while the exterior unit weighs 28.6 kg. The material input for each one of the heat pump components is presented in Table 1.

Heat pump fabrication

During the fabrication of one heat pump,39.5 KWh of electricity are required. Moreover,0.058 m3of water are used and therefore are converted to wastewater.

Heat pump packaging

Packaging follows the assembly of the heat pump. Packaging materials are presented in the last column of Table 1. The total packaging weight of the heat pump is 20 kg.

Heat pump transportation

Assembly of the heat pump takes place in central Italy. Then, the heat pump is transported by road to the Italian port of Bari, for a distance of 538.5 km. Then, the heat pump is transported by sea to the port of Igoumenitsa in Greece for a distance of 361 Km. Then the heat pump is transported by road to Kalochori,Thessaloniki where the warehouse is located for a distance of 319.6 Km,followed by road transport for another 506.7 Km to its final destination,i.e. Athens. During the whole transportation route from central Italy to Athens,the total weight transported is 120 kg(i.e.,heat pump plus packaging). Therefore, the total transportation load is estimated at 163.8 tkm while the sea load transport is estimated at 43.2 tkm.

Heat pump installation

For the installation phase of the heat pump,copper pipelines were used. More specifically,3.9 Kg of copper pipes are required for the connection of the outside unit to the internal one;moreover 56 m of copper pipes(38.4 Kg)are required for the connection of the heat pumps to the fancoils.

Limitations of the study

In the present study the life cycle stages of(i)heat pump use and(ii)the end-of-life management will not be accounted for. Moreover, in the installation phase the material inputs for the fancoils required for the delivery of heating or cooling to the consumer are not taken into account.

Moreover, the heat pump under investigation utilises the R410A refrigerant, which is a hydro-fluorocarbon(HFC).Since R410A is not included in the Simapro 7.1 database,R134A,which is also a HFC,was selected to be the replacement for the process modeling. Note that the use of R410A results in electricity savings during the use of the heat pump, because it is a very efficient refrigerant. In addition to the electricity savings during its use, the utilisation of R410A reduces the sizes of the heat exchanger, the compressor and of the condenser,since it captures and releases heat more efficiently(Chen et al.,2008).

Impact assessment

Table 2 LCIA characterisation results of the life cycle stages of the heat pump.

Table 3 LCIA characterisation results of the heat pump assembly.

The LCA study is conducted using the LCA software SimaPro 7.1. Life Cycle Impact Assessment (LCIA)is the step where the data of the inventory analysis are further interpreted in environmental impacts. The inventory results can be classified into different impacts categories. The impact assessment method used was CML 2 baseline 2000 developed by the Centre of Environmental Science of Leiden University(Pre Consultants,2008),which includes the following ten midpoint categories: eutrophication potential (EP),global warming potential for time horizon 100 years (GWP100), stratospheric ozone depletion potential (ODP), photo- chemical ozone creation potential (POCP),acidification potential (AP),abiotic depletion factor (ADF),marine aquatic ecotoxicity potential (MAETP), fresh water aquatic ecotoxicity potential (FAETP), terrestrial ecotoxicity potential(TAEP)and human toxicity potential(HTP).

4 Results

The characterisation results of the various life cycle stages of the heat pump are presented in Table 2. Based on the overall characterisation results, Figure 2 presents the relative contribution of each one of the examined life cycle stages of the heat pump. It is evident that the heat pump components are responsible for the greatest part of the impacts compared to the other life cycle stages of the heat pump under investigation. On the opposite,the life cycle stage of the transportation of the pump presents the lowest impacts among those examined.

Fig.2 %contribution to the characterisation results of the life cycle stages of the heat pump.

Fig.3 Characterisation of the heat pump assembly impact assessment results.

In order to assess the most important impact categories, normalization was performed via the CML2 baseline 2000 method using 1995 Western Europe values. Normalisation reveals that the most important impact categories were, in order of significance, the following: human toxicity, abiotic depletion, ozone layer depletion, terrestrial ecotoxicity and global warming. The components of the heat pump assembly is the dominant contributor to all of the normalised impact categories.

The obvious conclusion is the heat pump assembly is the dominant stage of the examined life cycle of the pump. Its contribution is the highest in all impact categories compared to the other life cycle stages. In order to further analyse the environmental impacts of the heat pump assembly, we focus our attention on the specific components of the assembly.

Characterisation results for the heat pump assembly

The life cycle impact assessment characterisation results, based on the CML 2 baseline 2000 ready-made method, of the specific heat pump components are presented numerically in Table 3 and graphically in Figure 3, which demonstrates the fact that the heat pump case is the dominant component in terms of the impact assessment results. This is attributed to the fact that the case is made of steel. Following the case,other parts of the heat pump cause more impacts compared to the control system,the compressor and the electrical resistance.More specifically, the heat pump case is contributing 62.8%to the depletion of the abiotic resources, 60.4%to the oxidation impact category, 49.8%to the eutrophication, 48.5%to the global warming,69.9%to the human oxidation, 66.8% to the freshwater aquatic ecotoxicity, 59.8% to the marine aquatic ecotoxicity and 69.5% to the terrestrial ecotoxicity.

More specifically, in the abiotic depletion impact category the case is mainly responsible for the impact(62.76%),followed by the other parts(16.57%)and the control system(14.63%).

In the acidification impact category the heat pump case contributes 60.4%,followed by the other parts with 19.1% while the control system contributes 14%. The stainless steel case contributes also half (49.8%) of the eutrophication impact category,followed by the control system which contributes 18.2%.

In the global warming impact category, the case generates 48.5%of the impact followed by the other parts which contribute 35.6%.

In terms of the ozone depletion impact category, note that 99.89% of the impact is attributed to the other parts. This is due to the fact that the refrigerant is included in the other parts of the heat pump.

The following four impact categories, namely human toxicity, freshwater ecotoxicity, marine aquatic ecotoxicity and terrestrial ecotoxicity, follow an identical profile in terms of the respective impact contributions.The case’s contribution is 69.9%,66.8%,59.8%και 69.5%respectively. The contribution of the control system ranks second,contributing 16.3%,16.8%,17.7%and 15.9%to the four impact categories respectively(see Table 3).

The final impact category to be discussed is the photochemical oxidation. The case of the heat pump is again the major contributor to this impact category(69.5%)followed by the other parts(16.0%)and the control system(14.6%).

Normalisation of the LCIA results

Based on the normalisation performed via the CML2 baseline 2000 method using 1995 Western Europe values it is evident that the human toxicity is the dominant normalised impact category. The case of the heat pump contributes to the normalised results of the human toxicity by 69.7%,due to the material of the case which is stainless steel. The control system is the heat pump component that causes 16.3%of the normalised human toxicity impact;other components contribute 6.8%to the normalised human toxicity impact.

In the depletion of abiotic resources impact category,the heat pump case contributes 62%,the other components of the heat pump contribute by 16.6%while the control system contributes 14%.

Regarding the stratospheric ozone depletion impact category,the other components contribute to it by 99.9%.It is evident that the refrigerant is the single contributor to this impact category. In the terrestrial toxicity impact category,the stainless steel case contributes by 69.5%while the control system contributes 16%. Moreover,the stainless steel case contributes 48.5% and 60.4% respectively to the global warming and acidification impact categories, while the other heat pump components contribute by 35%and 19.1%to the aforementioned impact categories,respectively.

5 Conclusions

An environmental impact assessment, via means of LCA, of a ground heat pump manufactured in Italy and installed in Greece has been performed. Our analysis reveals that the life cycle stage that contributes mostly to the environmental burdens is that of the components that make up the heat pump. Focusing on the components,the case of the heat pump, that is made of stainless steel, in the single component which causes most of the environmental impacts. Normalisation of the results reveals that the human toxicity impact category is the one that manufacturers should focus on, in order to alleviate the adverse environmental impacts caused by the heat pump.