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Providing up-to-date numerical data across a range of topics related to renewable energy technologies, Renewable Energies and CO2 offers a one-stop source of key information to engineers, economists and all other professionals working in the energy and climate change sectors. The most relevant up-to-date numerical data are exposed in 201 tables and graphs, integrated in terms of units and methodology, and covering topics such as energy system capacities and lifetimes, production costs, energy payback ratios, carbon emissions, external costs, patents and literature statistics.

The data are first presented and then analyzed to project potential future grid, heat and fuel parity scenarios, as well as future technology tendencies in different energy technological areas. Innovative highlights and descriptions of preproduction energy systems and components from the past four years have been gathered from selected journals and international energy departments from G20 countries.

As the field develops, readers are invited and encouraged to contact the authors for feedback and comments. The ongoing data collection and analysis will be used – after proper acknowledgment of contributors - to develop new editions. In this way, it is ensured that Renewable Energies and CO2 will remain an up-to-date resource for all those working with or involved in renewable energy, climate change, energy storage, carbon capture and smart grids.





Chapter 1. Executive Summary

The Energy Technology Perspectives 2012 survey of the International Energy Agency (IEA) highlights that limiting global temperature rise to 2 °C above pre-industrial levels is technically feasible, if timely and significant government policy action is taken and a range of clean energy technologies are developed and deployed globally to reduce CO2 emissions [1]. However, CO2 emissions are steadily growing, reaching 395 ppm in March 2012 (Fig. 1.1) [2].
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart

Chapter 2. Renewable Energy and CO2: Current Status and Costs

In this chapter, it is exposed a brief description of the current use and theoretical potential of renewable and conventional energies, the evolution of the CO2 emissions and atmospheric concentration and their influence in the climate change, fuel and electricity generation costs of renewable energy technologies, the technological development status and the environmental impacts of the renewable energy technologies. Significant figures and how they have evolved in recent decades are included, and also estimation of conventional fuel reserves and leading countries in terms of renewable energy penetration.
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart

Renewable Fuels and Carriers


Chapter 3. Biomass

The energy stored in the biomass existing on the Earth can be transformed by chemical or biological processes into heat or electricity. From a certain point of view, biomass can be considered as solar energy stored in carbohydrate chemical bonds by means of the photosynthesis process. Therefore, the emitted CO2 to the atmosphere, when biomass is burned or transformed, can be considered to be equal to the CO2 absorbed during its previous growth, i.e., energy from biomass could in principle be considered as carbon neutral. It is important to remark that bioenergy provides about 12 % of the global energy consumption, and therefore is, together with hydropower, one of the main renewable energy resources in the world. In this chapter, we describe some of the most common energy processes for using biomass as a fuel: direct combustion, pyrolysis for the production of charcoal, gasification for obtaining synthesis or producer gas, co-firing with coal, etc. On the other hand, the production of liquid or gaseous biofuels will be treated in Chap. 4.
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart

Chapter 4. Biofuels

The production of liquid biofuels from biomass stocks for the substitution of crude oil products (gasoline, diesel, etc.) in the transportation sector is one of the main objectives of bioenergy research. One of the main advantages of using biofuels is that, if one considers their complete life cycle, their carbon emissions can be substantially lower than in the case of fossil fuels. In this chapter, we describe all biofuel technologies and prospects. Thus, bioethanol and biodiesel that are usually produced from agricultural crops may have reached economic viability, but they also compete against food production elevating their prices. For this reason, second-generation biofuels are currently being developed which use lignocellulosic biomass (straw, grass, forestry sawdust, etc.) and therefore do not compete for agricultural land and water. In addition, we also treat in this chapter the so-called third-generation biofuels, like those obtained from microalgae, which offer excellent prospects for the production of biodiesel due to their high concentration in lipids. Besides, microalgae do not compete for large freshwater resources and can act as CO2 sinks during their growth. Hydrogen obtained from biomass can be considered another third-generation biofuel, but it is described in Chap. 5.
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart

Chapter 5. Hydrogen Production

It is well known that hydrogen can become an important carrier and storage medium of energy in the near future and a serious medium-term alternative to fossil fuels. By means of fuel cells, hydrogen can serve as a clean fuel, i.e. without the emission of pollutant gases, for the production of electricity in which it is known as the hydrogen economy. Another main advantage of hydrogen is that is the fuel, which provides the highest amount of energy per unit weight. However, the large-scale implementation of hydrogen requires significant advances in further lowering its production costs and finding efficient techniques for its storage and transportation. At present, there is also a strong interest to couple the inherent intermittent renewable energy systems with the production of hydrogen so that the hydrogen can return the energy stored by means of a fuel cell when the primary source (solar radiation, wind, etc.) is not available. In this chapter, we make a review of the most usual techniques for hydrogen production: steam methane reforming, gasification, electrolysis, renewable energies, etc., and costs. One important result from our findings is that hydrogen produced by biomass gasification can practically compete in costs with that produced from fossil fuels.
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart

Power From Renewable Sources


Chapter 6. Photovoltaics (PV)

During the last 20 years, both the photovoltaic (PV) cumulative installed power and the annual electricity production have increased at an annual rate of about 40 %, resulting in an estimated 67 GW cumulative capacity in 2011. This tremendous growth has been mainly a consequence of the continuous decrease of the cost of solar systems, 75 % in the last 3 years. Therefore, depending on the intensity of the solar resource, the PV electricity is reaching grid parity in many regions of the world. In this chapter, we make a grid parity study of PV and the efficiency of the different types of solar cells. We describe their evolution from the first-generation ones, produced from crystalline silicon, to the thin film or second-generation cells, which make use of much smaller quantities of semiconductor materials: CdTe, CIGS, amorphous-Si, etc. The evolution to the less mature third-generation solar cells, based in novel physical concepts, is also described. In summary, solar PV can be considered today as a mature technology for electricity production both at the large utility production plant level, or in domestic small-scale applications either isolated or grid connected.
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart

Chapter 7. Concentrated Solar Power

After photovoltaics (PV), concentrating solar power (CSP) is at present the major technology for producing solar electricity. Generally, CSP uses concentrating high-reflective mirrors to generate high-temperature thermal energy that is fed into conventional steam or gas turbines for the production of utility-scale power. Within CSP systems, the most mature are the parabolic trough systems, which concentrate the energy from the sun by means of long cylindrical mirrors of parabolic cross section. Next in popularity are the tower systems, which use a large field of numerous flat mirrors (heliostats) to concentrate the solar direct radiation into a receiver located at the top of the tower. Also, parabolic dishes and linear Fresnel reflectors must be considered. These technologies are described in this chapter and grid parity is analysed and expected to be reached soon for locations with strong solar direct irradiation. Finally, in relation to CSP, it is important to emphasise how thermal storage as well as natural gas hybridisation can be easily added, thus practically eliminating the power intermittencies of other important renewable technologies.
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart

Chapter 8. Wind Power

Wind energy power generation has experienced an impressive annual growth during the last decade and represents today the highest amount of the electricity produced by all renewable resources if hydroelectric power is excluded. Wind energy can be considered at present a mature technology with production costs, which reach grid parity, under favourable conditions and high capacity factors. In this chapter, we make a review of the future technology trends, as for example the construction of very large wind turbines (5–10 MW) with hub heights around 150 m, and therefore being able to access to much faster winds than those close to ground. However, the main development in wind energy technologies is related to the deployment of off-shore wind farms, since offshore wind speeds are usually higher than those on land, and especially more continuous in time. Other interesting future trends are related to the development of miniturbines to be placed in urban areas, as for example parks, and also in buildings. Finally, we would like to remark that significant efforts are being dedicated to wind resource assessment in order to increase forecasting precision.
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart

Chapter 9. Hydropower

Hydropower is by large the main contributor to electricity production of all renewable resources. Hydropower is a very mature technology for the production of electricity at very competitive prices; furthermore, it can be considered for base-load generation, it responds extremely fast to energy peak demands and it can be stored by means of pumped hydro systems. However, the construction of large hydropower plants (>1 GW) often cause the displacement of large populations from their homes and significant environmental problems in river flora and fauna ecosystems. For these reasons, as we will see in this chapter, hydropower research is at present also focused on small-scale mini-power plants and run-of-river systems. We will also describe the different types of power turbines, which are most often employed depending on the height of the effective head of the reservoir, water flow and velocity, etc.
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart

Chapter 10. Geothermal Energy

Geothermal energy can be used either to generate base-load electricity with very high capacity factors and independent of seasonal conditions or to provide space heating and cooling in buildings. Globally, the annual production of geothermal electricity is somewhat smaller than solar PV production. In addition, it has already reached grid parity in locations with adequate resources. For power generation, geothermal energy can be used in conventional steam plants (flash technology) or in a closed-loop configuration (enhanced geothermal systems). Furthermore, the recently developed binary plants can produce electricity from low temperature (<100 °C) geothermal sources, which are used to boil a secondary fluid of very low boiling point (butane or pentane). A very interesting development in geothermal energy is the ground source heat pump technology. In these devices, a loop of pipes is inserted at depths about 100 m below ground, and the circulating fluid (often water) extracts thermal energy and transfers it to a heat pump.
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart

Chapter 11. Ocean Energy

There is a large variety of ocean energy technologies, which can be classified in various categories: tidal range and tidal currents, waves, ocean currents, thermal gradients and salinity gradients. The most mature of them, with great difference, is the one based in the rise and fall of tides (tidal range), followed by wave technologies. Of all the ocean technologies considered for the generation of electricity, it is only the tidal barrage the one that is close to grid parity, although barrage plants are faced with considerable environmental challenges. In addition, the technology is quite similar to hydropower plants, since the electricity is generated by the water released out of the barrage. In the case of tidal and marine currents, the technology is in principle not too complicated since the flow of water is used to move various types of turbines. Finally, the chapter also reviews the large variety of techniques, which can be employed to extract energy from the waves: oscillating water columns, oscillating body systems (floating or submerged), which generate electricity from their movements, overtopping converters, etc.
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart

Chapter 12. Nuclear Fusion

Although not yet developed at the commercial stage, nuclear fusion technology is still being considered as a very promising solution for the coverage of the future global energy needs. This is mainly due to its environmental acceptability, and to the fact that, contrary to nuclear fission, its by-products cannot be used in nuclear warfare. Since research in nuclear fusion for the production of energy started about 60 years ago, the most studied reaction has been the fusion of tritium with deuterium, which produces very energetic neutrons (17.5 MeV). For this reaction to occur, the reactants have to be at extremely high temperatures (several hundred million degrees), constituting a plasma that has to be simultaneously maintained and confined. In this chapter, we study the steps that are needed for the construction of nuclear fusion reactors able to maintain these self-sustained plasmas. The most developed reactors are the magnetically confined Tokamak at the ITER (Cadarache, France) and the inertially confined system located at the Lawrence Livermore Laboratory in the USA. It is important to remark that in spite of all the research efforts devoted to nuclear fusion, it is estimated that it will still take a few decades for this technology to be available at the utility scale.
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart

Storage and Management


Chapter 13. Solar Heating and Cooling

Solar heating and cooling (SHC) technologies exploit solar irradiation to either produce heat or, alternatively, provide air conditioning. The basic principle behind cooling is the sorption process by which coldness is generated by the evaporation of a solvent that is later adsorbed into another medium. Solar collectors for heating can be divided into flat-plate or air collectors, evacuated tube collectors and unglazed panels. In the case of air conditioning, the dominant technologies being used today are: closed chillers, which use either liquid or solid sorption materials, and open cooling cycles. In this chapter, different analyses about technology trends and how cost can be close to conventional heating and cooling systems are exposed. Moreover, it is appreciated how solar cooling systems operate more efficiently than for heating since the peak energy demand closely coincides with the highest solar irradiation. Within the field of SHC long-term energy storage is also considered to hold the heat (warm or cold) over time.
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart

Chapter 14. Fuel Cells

The main advantages of fuel cells are their high efficiency for electricity production of about 60 %, and practically zero emissions if hydrogen is introduced as fuel, in contrast to combustion fuel engines whose efficiency is approximately of 20 % at most and are very polluting. Their principle of operation in hydrogen-based fuel cells is the reverse to the electrolysis process: hydrogen and oxygen (or air) react in the cell producing an electron DC current. In this chapter, we describe the most often employed fuel cell devices, their name being derived from the kind of electrolyte used. The market is dominated by the proton exchange membrane fuel cell (PEMFC), which is probably the best candidate for vehicles and portable applications. They are followed by the phosphoric acid fuel cells (PAFC), which have the advantage of using either hydrogen or natural gas that can be reformed in the cell itself. Other cells studied are the solid-state fuel cells (SOFC), which use a solid oxide electrolyte, the molten carbonate fuel cells (MCFC) that can use CO2 from natural gas as fuel, etc.
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart

Chapter 15. Electricity Storage

Electricity storage technologies emerge as a response to synchronise electricity supply and demand, thus enabling the electrical grid to be managed in a consistent manner. Electricity storage is especially needed in distribution for load-levelling and for integrating the frequently intermittent renewable resources. In the case of considerable hourly variations of the demand, the levelling of the load would substantially reduce the projected total generating capacity making it more efficient and less costly. In this chapter, we review the main electrical storage technologies. The most common storage devices are batteries, which are highly efficient. Batteries have evolved during the last decades from the lead–acid ones to the lithium ion, which are at present receiving the most attention. If high power, instead of energy management is needed, then the use of ultracapacitors is more appropriate. Evidently, if very large amounts of energy and power are needed, pumped hydro systems constitute the best choice. Other energy storage technologies reviewed in this chapter are compressed air energy storage (CAES), flywheel devices and superconducting systems.
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart

Chapter 16. Smart Grids and Supergrids

Smart grids are necessary to take full advantage of most intermitent renewable resources such as wind and solar, since they are able to monitor and manage the delivery of power in real time. One important goal of smart grid deployment is also to reduce the peak demands, thus increasing the options for new loads such as, for example, electric vehicles. The deployment of the smart power grid will be accompanied by the development of other advanced technological areas, such as real-time monitoring of the whole power system by means of a communication meters for automatic reconfiguration of renewable resources. In addition, advanced metering enables bidirectional flow of information and, therefore, provides consumers with valuable data on electricity consumed and price. In this chapter, we also review the state of the art in supergrids, which will serve as large transmission networks between wide geographical areas. Many of the supergrids are starting to make use of high-voltage direct current (HVDC) technology, due to their very low losses specially across oceans. One interesting example of supergrid is the one projected under the Desertec program linking renewable resources from North Africa and Europe, but other supergrid projects are also in advance in other regions of the world.
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart

Chapter 17. Carbon Capture and Storage

The main object of the carbon capture and storage (CCS) technologies is the reduction of CO2 emissions produced in the combustion of fossil fuels such as coal, oil, or natural gas. CCS involves first the capture of the emitted CO2, mainly from power and industrial plants, its transportation and, finally, its injection in underground reservoirs for storage. In this chapter, we describe the four main technologies for CO2 capture: post-combustion capture, pre-combustion capture, oxy-fuelling and chemical looping. Evidently, any of these capture techniques result in a significant energy penalty to the base plant. However, it is expected that in the future CCS will contribute to reduce global CO2 emissions. After the CO2 is captured, it should be compressed for transportation through high-pressure pipelines or ships, and finally stored into geological formations such as depleted gas reservoirs, saline formations and deep unmineable coal seams. Depending on the capture technology, the additional costs for generating electricity from a coal plant with CCS have been evaluated.
Ricardo Guerrero-Lemus, José Manuel Martínez-Duart


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