“…Hence, in order to counteract these drawbacks, recent trends encouraged the research on renewable energy. The possibility of using ambient sources has thus become an important research field (Roundy and Wright, 2004;Krikke, 2005;Ng and Liao, 2005;Paradiso and Starner, 2005;Guyomar et al, 2007a;Lallart et al, 2008a). Such alternative solutions for providing electrical energy to systems may include solar energy (Hamakawa, 2003), thermal energy (Sodano et al, 2006) or mechanical energy.…”