Elsevier

Solar Energy

Volume 83, Issue 9, September 2009, Pages 1434-1445
Solar Energy

Life cycle assessment study of a 4.2 kWp stand-alone photovoltaic system

https://doi.org/10.1016/j.solener.2009.03.012Get rights and content

Abstract

The energetic and environmental life cycle assessment of a 4.2 kWp stand-alone photovoltaic system (SAPV) at the University of Murcia (south-east of Spain) is presented. PV modules and batteries are the energetically and environmentally most expensive elements. The energy pay-back time was found to be 9.08 years and the specific CO2 emissions was calculated as 131 g/kWh. The SAPV system has been environmentally compared with other supply options (diesel generator and Spanish grid) showing lower impacts in both cases. The results show the CO2-emission reduction potential of SAPV systems in southern European countries and point out the critical environmental issues in these systems.

Introduction

Power generation from photovoltaic (PV) systems is free from fossil fuel use and greenhouse gas (GHG) emissions. However a considerable amount of energy is consumed in the manufacturing and transport of the elements of the system, also the amount of energy and emissions from a decommissioning phase of the system must be taken into account.

Life cycle assessment (LCA) studies aim at comparing and analysing the environmental impacts of products and services. In solar PV systems these studies present the energy use in terms of energy pay-back time (EPBT), which is the time required for the solar PV system to generate the equivalent amount of energy consumed in the construction and decommissioning phases. In PV grid-connected systems the EPBT must be compared with the competing energy sources in order to justify its use as primary energy source. Numerous LCA studies have been carried out over PV grid-connected systems (Alsema, 2000a, Jungbluth, 2005, Kato et al., 1997, Kannan et al., 2006, Muneer et al., 2006, Knapp and Jester, 2001). A wide variation in the EPBT is found in these studies. Energy consumption during manufacturing solar PV modules does not vary significantly with geographical location. Nevertheless, the amount of electricity generated from a solar PV system depends on its geographical location, e.g. solar irradiation and temperature. Transport of components during construction and decommissioning phases depends on the site as well.

Stand-alone photovoltaic (SAPV) systems will hold an important share in the deployment of new photovoltaic systems, specially in developing countries, where there are still large rural areas without electrification of any kind, much less with an available electrical grid. Much of the future electrification projects will be funded by public investment, public–private partnership or non-governmental organizations, which have great concern about sustainable development and therefore the environmental impact of any project has to be carefully assessed. Nevertheless, few LCA studies can be found in the literature and they are usually restricted to Solar Home Systems (Alsema, 2000b) or hybrid systems (Watt et al., 1998). SAPV systems hardly have to justify its primary energy use since they are usually located in places where there is not competing energy source (e.g. remote areas, rural homes in developing countries, etc.). However a LCA study can be very useful to keep track of the different system components and to identify the energetically and environmentally most expensive steps and elements.

SAPV system design is very dependent on the geographical location of the system since the amount of electricity generated varies with the irradiance and temperature but also with the consumed energy. In general SAPV systems are designed according to a specific load pattern and they have an energy storage system to feed the load during the low or no solar irradiance periods. Therefore it is possible to find sunny periods where the energy source is available but there is no load, the energy storage is full and part of the available PV energy is not used.

In this article a LCA study has been carried out for a 4.2 kWp stand-alone solar PV system, which has been operating in Murcia (south-east of Spain) since March 2003. A description of the facility and the monitoring system is presented in Section 2. The LCA study is developed in Section 3, including the material inventory and the summary of the energy use and GHG emissions during the life cycle of the facility. Then the EPBT, the CO2 emission factor and the CO2 pay-back time (CO2PBT) are worked out using data from the facility. Finally, in Section 4 the conclusions from the study are presented.

Section snippets

Description of the SAPV system

The SAPV system at the University of Murcia Espinardo Campus (38° north, 1° west), sited 5 km from Murcia’s city centre was set up in March, 2003. It feeds part of the lighting system of the Animal Service Laboratory and was built as a contribution to the Spanish Plan for the Promotion of Renewable Energies. The size and design of the facility are similar to a typical SAPV system for rural electrification (isolated dwellings in developed countries or schools, health centres and small farms in

Life cycle assessment

A LCA was performed to quantify the energy use and GHG emissions from electricity generation from a solar SAPV system. We assumed a life time of 20 years for the PV facility. However, PV modules are expected to have longer life-times according to the manufacturer guarantee. A life cycle assessment usually includes a life cycle cost analysis. Since this study is focused on environmental aspects, we only present the life cycle energy and GHG emission analysis. Spain does not have yet extensive

Conclusions

A 4.2 kWp SAPV installation at the University of Murcia (Spain) has been described. The daily constant load pattern allows us to work out the annual energy consumption as 5028.24 kWhel/year. On the basis of the LCA, it was found that the facility has about 45.692 MWhel of embodied energy and 13.166 metric tons of embodied CO2. As it was expected, the biggest energy requirements and emissions are in the construction phase.

PV modules and batteries are the energetically and environmentally most

Acknowledgement

This work has been possible thanks to the project HOPE CSD2007-00007 (Consolider-Ingenio 2010).

References (28)

  • Bombach, E., Müller, A., Wambach, K., Röverl, I., 2005. Recycling of solar cells and modules – recent improvements. In:...
  • A. Celik et al.

    Optimal sizing and life cycle assessment of residential photovoltaic energy systems with battery storage

    Progress in Photovoltaics: Research and Applications

    (2008)
  • ECI, 2006. Recycling of copper a solution to meet the growing demand for raw materials. Press Kit for the European...
  • EEA, 2003. Overall energy efficiency and specific CO2 emissions for passenger and freight transport. Indicator Fact...
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    Supported by the Spanish Ministry for Science and Education through the fellowship AP2005-2271.

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