A variation on the hybrid vehicle is the ‘plug-in hybrid’, which can be connected to the electric grid. The savings in energy costs over the whole cycle of charging an onboard battery and then discharging it to run an electric motor in an electric-hybrid (e-hybrid) car is 80%. This figure is approximately 4 times higher than the savings from fuel-cell cars running on hydrogen made using electrolysis and 30% higher than savings from cars running on gasoline (Romm, 2006). These vehicles allow the replacement of a substantial portion of the fuel consumption and tailpipe emissions. If the electricity is produced from CO2-free sources, then e-hybrids can also have dramatically reduced net greenhouse gas emissions.

The electrical storage system is the key element of the e-hybrid car because its power capacity and lifetime decisively define the costs of the overall system (Bitsche & Gutmann,

2004) .

Bio-based energy-management processes are emerging and could make a significant contribution in the medium term. The production of electricity is also possible with whole — microorganism fermentation. Fe(III)-reducing microorganisms in the family Geobacteraceae can directly transfer electrons onto electrodes (Bond et al., 2002; Bond & Lovley, 2003). However, the range of electron donors that these organisms can use is limited to simple organic acids. By contrast, Rhodoferax ferrireducens is capable of oxidizing glucose and other sugars (such as fructose and xylose) with similar efficiency and of quantitatively transferring electrons to graphite electrodes. The sugar is consumed in the anode chamber. The oxidation of one molecule of glucose produces CO2, H+ and 24 electrons with a ~83% efficiency. The reaction produces a long-term steady current that is sustained after glucose — medium refreshing in the anode chamber. This microbial fuel cell can be recharged by changing the anode medium. It does not show severe capacity fading in the charge/discharge cycling and only presents low-capacity losses under open circuits and prolonged idle conditions (Chaudhuri & Lovley, 2003).

Another bacterium that is able to transfer electrons to solid metal oxides is Shewanella oneidensis MR-1. In addition, to their remarkable anaerobic versatility, analyses of the genome sequences of Shewanellae species suggest that they can use a broad range of carbon substrates; this creates possibilities for their application in biofuel production (Fredrickson, 2008). Production and storage of electricity are expected to evolve quickly within the new paradigm of emerging bioelectronics (Willner, 2002).

Sol-gels have been demonstrated to be usable for the entrapment of membrane-bound proteins in a physiologically active form and have been proven to be capable of maintaining protein activity over periods of months or more (Luo et al., 2005). Using a membrane — associated F0F1-ATP synthase, Luo et al. (2005) showed that the photo-induced proton gradient can be used to ‘store’ light energy as ATP. This has the advantage of eliminating passive leakage of ions across the membrane. In addition, ATP can be used for direct powering of motor proteins for the conversion of chemical energy to mechanical energy (Browne & Feringa, 2006). Nano power plants based on the rotation of magnetic bead propellers mounted on Fcft-ATP synthase rotors that are fed by ATP to induce electric current in microarrays of nanostators are now being designed and are in the research and development stage of construction (Soong et al., 2000; Yasuda et al., 2001).