**Part 4**

**Energy Efficiency on Supply Side** 

224 Energy Efficiency – A Bridge to Low Carbon Economy

Wang Fulin, Yoshida Harunori, Yamashita Michiko, Improving Air-conditioners' Energy

Wang Fulin, Yoshida Harunori, Yamashita Michiko, Prediction of the Energy Savings of a

Conference in 2008, pp. 131-136, 2008.10

2009.11

Efficiency Using Hydroponic Roof Plants, Proceedings of the 29th AIVC

System Combining Air-conditioner's Outdoor Unit with Hydroponic-cultivated Roof Plant, Proceedings of the 6th International Symposium on Heating, Ventilating and Air Conditioning - ISHVAC09, Nanjing, China, pp. 419-427,

**11** 

*Portugal* 

**Criteria Assessment** 

**of Energy Carrier Systems Sustainability** 

Pedro Dinis Gaspar, Rui Pedro Mendes and Luís Carrilho Gonçalves *University of Beira Interior - Faculty of Engineering - Electromechanical Eng. Dept.* 

Energy carrier systems of renewable sources have become widely used due to world's need to reduce the fossil fuel consumption and consequently greenhouse effect. However, the energy density of these systems is much lower than fossil fuels or nuclear fission. Besides, energy outlooks (IEA, 2011) show that energy demand around the world will continue its increasing trend. In turn, the wide scale construction of power plants based in fossil fuel cannot continue due to negative environmental effects. Also, the latest accident in reactor n.er 3 of the Fukushima Daiichi Nuclear Power Station in Japan in consequence of the March 11 earthquake and tsunami increased the fear of radiation effects and the discussion about nuclear safety. Thus, it is relevant to provide an up-to-date assessment of the global sustainability of current and future energy carrier systems for electricity supply based on fossil fuel and renewable energy sources. It includes the analysis of energy carrier systems based on fossil fuels: coal, natural gas and oil and on renewable ones: wind, solar photovoltaic, geothermal, hydro, hydrogen, ocean (wave and tidal power), and nuclear.

The sustainability assessment of an energy conversion process into electrical energy is carried out in technological, economical, environmental and social dimensions. A solid basis for a state-of-the-art interdisciplinary assessment using data obtained from the literature supports the sustainability comparison. Thus, indicators that best describe the technologies and that are related to each of the abovementioned dimensions are defined to quantify the sustainability of energy carrier systems. These indicators are: efficiency of electricity generation, lifetime, energy payback time, capital cost, electricity generation cost, greenhouse gases emissions during full life cycle of the technology, land requirements, job creation and social acceptance. A criteria based on membership functions is exposed in order to determine a global sustainability index that quantifies how sustainable each energy carrier system is. The multi criteria analysis is performed considering different weighting functions applied to sustainability indexes in order to assess, today and in the near future, energy carrier systems that should be used in the mix of energy conversion systems to electricity. This work extends the research developed by Mendes et al. (2011a) and Mendes

This section is devoted to describe the different types of energy carrier systems for conversion into electricity. The world energy source share of electricity generation in 2009 is

**1. Introduction** 

et al. (2011b).

**2. Energy carrier systems** 
