The History Of Renewable Energy

Published Date: 02 Nov 2017

CHAPTER 1

The current scenario of petroleum price is keep increased even though the ministries are trying to help the people in their country in order to reduce an uprising problem with household cost as well as monthly cost for electricity and transportations. However, this effort does not seem beneficial since the oil price is depending on the world wide price. The reason for nonstop of fossil fuels price increases is mainly due to the rapid depletion and difficult to retain. This problem will increase and increase the energy price and maybe eventually it would not be available for many countries or individuals. In order to avoid this to happen, the alternative choice should be made. Luckily, until this moment, the research and development of renewable energy are keeping increased within the year.

In addition, the need of renewable energy is becoming more crucial due to the problem arising via fossil fuels usage which contributes to the environmental issues.

The problem actually already been faced today since the earth is keep warming up and the climates are changing which at certain parts in the world were to be heavily rain and sunshine whereas the other parts is more dryer. The depletion of ozone layer which contributes to the earth warming up was mainly due to the increase of pollutant emission levels. In the era of globalization, the trend in possessing a very own vehicles have shown a protrusion in every individual. Thus, the contribution to the air pollution will be increase every year and every minute. However, environmental awareness has been foresight since last two decades, especially by the automotive industry in order to develop innovative solutions for improving or maintain the quality of environment (Jaafar, 2006).

The renewable energy can be divided into seven types which are solar energy, wind energy, geothermal energy, bioenergy, hydropower, ocean energy as well as hydrogen and fuel cells. Among these types, fuel cells is the most promising renewable energy sources since the electrical current or energy can be directly converted from combustible of fuel. The contribution of fuel cells has burgeoned in other countries such as United Kingdom, United State, Japan and China where they accelerated the research and development of fuel cells technology especially in transportation, stationary power and microelectronic devices (Jaafar, 2006).

The proton exchange membrane (PEM) is the heart of the fuel cells system. PEM consists of many proton-conductive functional groups which only allows proton to transfer within from one side to another (Zhang et al., 2012). But, however, the research and development on proton electrolyte membrane is keep burgeon in order to develop a sophisticated electrolyte membrane in order to cater the fuel crossover as well as conductivity enhancement of fuel cell which can give benefit on environmental as well as reducing cost.

1.1.2 Nanotechnology

With the rapid growth of nanoscience and nanotechnology over the last 20 years, eventually give an insight the use of impregnation nanotechnology on proton electrolyte membrane. Targeted development of new one-dimensional (1D) nanostructures, such as continuous nanofibers (NFs), large aspect ratio nanowires (NWs) and nanorods (NRs), is attract much attention due to the reliance of their physical properties on directionality. As essential one-dimensional nanomaterials, nanofibers have a very large specific surface area because of their small diameters, and nanofiber membranes are highly porous with excellent pore interconnectivity (Cavaliere et al., 2011). These unique characteristics plus the functionalities from the polymers themselves convey nanofibers with many desirable properties for sophisticated application.

Nanocomposites are usually referred to composite structures less than 100 nm in scale. Layered silicates-polymer nanocomposite is a new polymer electrolyte membrane (PEM) that lately concerned a great deal of interest due to the improvement in the mechanical, thermal and barrier properties of the pure polymer (Tien and Wei, 2001). Compared to the corresponding pure polymer membranes as well as commercial Nafion® membranes, many polymer-inorganic nanocomposite membranes shown much lower fuel permeability along with similar or improved proton conductivities. These improvements were due to nano-dispersion of layered silicates throughout polymer matrix (Wang and Dong, 2007).

The combination of the advantages from the base materials: i.e., the flexibility and process ability of polymer, as well as the selectivity and thermal stability of the inorganic fillers are contributed to the aforementioned properties. By adding the inorganic nanofillers, it may affect the membrane cell in two ways: 1) the uniform nanosized distribution of inorganic filler particles produces a winding diffusion pathway for fuel to transfer through the nanocomposite membrane, and 2) the complete exfoliation morphology allows more cations to mobile and available for conduction (Wang and Dong, 2007).

In general, the smaller the particle sizes of the inorganic fillers, the larger the conductivity enhancement as well as lowering the methanol permeation. Jaafar et al. (2009) has conducted an experiment on SPEEK with the addition of Cloisite 15A® nanofiller with a good compatibility has shown a slightly improvement in the barrier properties of SPEEK. Thus, it is proved that the well-dispersed of Cloisite 15A® nanofillers with smaller particle size can increase the tortoise part for methanol and eventually decrease the permeability of the methanol. On the other hand, due to the absence of exact structure-property correlations in the polymer electrolyte systems, a complete understanding of the ion conduction phenomenon is still lacking.

Even so, to explain the mechanistic aspects of ion transport in nanocomposite polymer electrolyte systems, a working hypothesis has been recommended accordingly to which, the dispersion of submicron or nano-size filler particles having large surface area, into the polymer host lowers the degree of crystalline, which may also be thought to be because of the interaction between ceramic surface states and polymer segments (Croce et al, 1998; Golodnitsky et al., 2002). Hence, in addition to the usual space charge effects of the dispersed particles, the increased amorphosity would also support the improvement for conductivity in terms of increased ionic mobility through the amorphous phase.

Basically because of this idea, nanocomposite polymer electrolytes wherein nanosized inert solid particles are added to the polymer electrolytes are presently the focus of this studies, both practical as well as theoretical. From the morphological point of view, exfoliated polymer-inorganic nanocomposite rather than intercalated or ordinary nanocomposites was considered as the promising structures with a great potential to exhibit high performance nanocomposites (Hasani-Sadrabadi et al., 2010a). With the exfoliated polymer-inorganic nanocomposite structure, good dispersion of Cloisite15A® particles in the SPEEK matrices, which has successfully activated the function of passive filler such as Cloisite15A® particles as methanol barrier by providing the winding diffusion effects towards methanol molecules and thus, lowering the methanol permeability (Jaafar et al., 2011).

Problem Statement

Several methods have been studied and developed to fabricate nanofibers, such as template, self-assembly, melt-blowing, phase separation and electrospinning (Doshi and Reneker, 1995;Fang et al., 2010). Electrospinning is competent in producing conductive fibrous membranes with high specific area, high porosity and tunable fiber diameters, which further broadened conductive polymers applicability in energy applications. The utilization of electrospinning in these applications is mainly due to the desirable properties of electrospun fibrous films such as, large specific surface areas for electrochemical reactions, and high durability. Experimental parameters such as molecular weight, solubility, viscosity, surface tension, electrical conductivity, solvent vapor pressure, relative humidity, electric field and feed rate of the solution must be precisely controlled in getting desirable properties of the fibers and by tuning these conditions, a wide range of polymers can be processed.

Electrospinning has gained significant interest in the past two decades as a method for fabricating long continuous fibers with nanoscale diameters. Elsewhere had extensively discussed on the basic experimental electrospinning process, but the combination of nanocomposite membrane material and the synthesis by electrospinning is rarely studied (Kumar and Deka, 2010). Li et al. (2006) reported that the electrospinning and electrosprying of sulfonated poly (ether ether ketone ketone) (SPEEKK), and found that the electrospun/sprayed membrane shows a more distinct SAXS ionomer peak, shifted to lower angles compared to a cast membrane, indicating better phase separation and larger proton transport channels. In their study, the highest conductivity was obtained with a spherical rather than fibrous morphology, suggesting that proton transport occurs on the interface between particles rather than within the polymer itself. Similarly, a study by Tamura et al. (2010) on sulfonated polyimide nanofibers reported a much higher apparent conductivity of single nanofibers compared to cast films, with greater conductivity along the fibers than in the perpendicular direction of their membrane.

Nafion, a commercially available fluoropolymer developed by DuPont, is the most commonly used proton exchange membrane in PEM fuel cells. Unfortunately, Nafion is challenging to process via electrospinning, as it is not soluble in most common solvents. This insolubility results in formation of micelles that cause a decrease in chain entanglement and an inability to electrospin fibers without the addition of a high molecular weight carrier (Thomsett, 2010). Although the studies in electrolyte membrane for fuel cell application is quite various but only a few or maybe almost zero studies focused on the effect of electrospun Cloisite 15A® on the performance of the proton electrolyte membrane. Therefore, in this study, sulfonated poly (ether ether ketone) (SPEEK) (considerably high molecular weight of 39200 kgmol-1) will be used as the base polymer matrix, while the Cloisite nanoclay will be electrospun onto the polymer. It is strongly believed that a novel polymer-nanocomposite electrolyte membrane in complete exfoliated structure will be developed.

Thus, this study will be providing a high performance polymer electrolyte membrane which can be potentially utilized in the fuel cell applications. The resultant nanofibers polymer nanocomposite electrolyte membranes containing SPEEK (base polymer matrix) and Cloisite clay (inorganic filler) will be characterized for their electrochemical properties prior to the performance properties of PEM. All characterizations will be studied as a function of inorganic filler’s dispersion state.

Objective of the Study

The aim of this proposed project is to develop the exfoliated SPEEK/Cloisite 15A® nanocomposite membrane which synthesis by electrospinning to be used as an electrolyte for direct methanol fuel cell system. The specific objectives of the project are:

To investigate the correlation between the dispersion state of the electrospun inorganic fillers in conductive polymer matrix of the polymer nanocomposite membrane.

To optimize the electrospinning parameters for the fabrication of Cloisite 15A® nanofibers.

To characterize and testing the performance prior to DMFC application.

Scope of the Study

In order to achieve the aforementioned objective of the research, the following scopes are outlined:

Fabricating the sulfonated poly (ether ether ketone) (SPEEK) by sulfonation reactions.

Preparing SPEEK and Cloisite 15A® dope solution.

Preparing Cloisite nanofibers via electrospinning process

Optimizing the parameters in electrospinning process

Observing the dispersion of the Cloisite in polymer matrix via XRD/FESEM

Characterize its physical and electrochemical properties in term of water uptake, proton conductivity, methanol permeability, thermal stability.

Designing the MEA for DMFC performance test