The atmosphere

The major constituents of the present atmosphere are nitrogen, oxygen and water. For dry air at sea-level the nitrogen constitutes 78 by volume, oxygen 21 and minor constituents 1 , the major part of which is argon (0.93 ) and carbon dioxide (0.03 ). The water content by volume ranges from close to zero at the poles to about 4 in tropical climates. Typical variations of density, pressure and temperature, as functions of height, are shown in Fig. 2.27. Common names for the different layers are...

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I05 -I04 -I03 -I02 -50 -10 Figure 1.16. Trends in average rate (solid line) of energy conversion per capita, not including fluxes associated with the local thermal environment (same as Fig. 1.1, but on a logarithmic time scale). Dashed lines indicate the corresponding trends for the societies, which at a given time have the highest and the lowest average energy usage. For the more recent period, data from Darmstadter et al. (1971) and European Commission (1997) have been used, in a smoothed...

River flows hydropower and elevated water storage

The kinetic energy of water flowing in rivers or other streams constitutes an energy source very similar to that of ocean currents. However, rather than being primarily wind driven or caused by differences in the state of the water masses themselves, the river flows are part of the hydrological cycle depicted in Fig. 2.61. Water vapour evaporated into the atmosphere is transported and eventually condensed. It reaches the ground as water or ice, at the elevation of the particular location. Thus,...

Energy Supply Systems

6.2 Simulation of system performance 592 6.2.1 Treatment of the time variable 594 6.2.2 Load structure 596 Biologically acceptable surroundings Food and water Security Health Relations Activities Summary of end- 6.2.4 Photovoltaic power production 621 6.2.5 Wind power production 625 6.2.7 Biofuel production 639 6.3 Examples of local system simulations 645 6.3.1 Solar heat or heat-and-electricity producing 646 systems Model description Solar radiation data Heat load of an individual house Heat...

N X p r A Mp

The central part of the reaction rate, < av> , is shown in Fig. 2.99 for the branch 1 reactions of the pp-cycle, as well as for the 3He+4He reaction opening the alternative branches. The basic cross sections S(0) used in the calculations are quoted in the work of Barnes (1971). The barrier penetration effects are calculated in a modified form, taking account of the partial screening of the nuclear Coulomb field by the presence of electrons. Such penetration factors are included for the weak...

Basic principles of energy conversion

A large number of energy conversion processes take place in nature, some of which were described in Chapters 2 and 3. Man is capable of performing a number of additional energy conversion processes by means of various devices invented during the history of man. Such devices may be classified according to the type of construction used, according to the underlying physical or chemical principle, or according to the forms of energy appearing before and after the action of the device. In this...

Radiation at the Earths surface

The radiation received at the Earth's surface consists of direct and scattered (plus reflected) short-wavelength radiation plus long-wavelength radiation from sky and clouds, originating as thermal emission or by reflection of thermal radiation from the ground. Figure 2.12. Net radiation flux E0 at the top of the atmosphere (NCEP-NCAR, 1998). Direct and scattered radiation Direct radiation is defined as radiation which has not experienced scattering in the atmosphere, so that it is...

Variability in wind power

An example of short-term variations in wind speed at low height is given in Fig. 3.35. These fluctuations correspond to the region of frequencies above the spectral gap of Fig. 2.110. The occurrences of wind gusts, during which the wind speed may double or drop to half the original value over a fraction of a second, are clearly of importance for the design of wind energy converters. On the other hand, the comparison made in Fig. 3.35 between two simultaneous measurements at distances separated...

The undisturbed energy cycle

Based on the material presented in sections 2.2 and 2.3, and in particular on the net radiation summary, Fig. 2.16, it is now possible to construct a schematic flow chart for the energy conversion and transport taking place in the Earth-atmosphere system (averaged over the year and geographical position). The result of such an attempt is shown in Fig. 2.86. Different energy forms have been placed in different vertical columns, whereas the horizontal rows represent the different components of...

Productivity in different environments

The gross primary production of a plant or, in general, of an ecological system is the rate at which solar energy is assimilated, i.e. the total amount of energy produced by photosynthesis. The net primary production, on the other hand, is the difference between gross primary production and respiration. The respiration processes involve an increase in redox potential (oxidation), either by consumption of oxygen aerobic respiration, the net result being equivalent to (3.43) or by the action of...

Mans interference with the energy cycle

Figure 2.87 attempts to summarise the modifications of the energy cycle caused by human society today and to identify a number of points on the flow diagram of Fig. 2.86 which could contribute to serving man's purpose. Some of these conversion methods are well known but only in modest use today. The compartments and main layout of Fig. 2.86 are repeated without text in Fig. 2.87, as a background for the lines connecting certain points, along the energy flows or at the energy stores, with the...

Mans interference with climate

The first significant anthropogenic influence on climate is probably the one associated with extensive destruction of natural vegetation, primarily aimed at transforming it into arable land or pastures. Presently, about 10 of the continental area is cultivated and about 30 is occupied by grassland or pastures (Odum, 1972). The transformation of steppe or forest into arable land has a number of consequences. The components of the net energy flux (2.10) are altered. The net radiation flux is...

The oceans and continents The water cycle

The processes by which water is transferred between different regions of the ocean-soil-atmosphere system may be described in much the same way as that used for the transfer of energy. Considering first a vertical column extending from the ocean-continent surface down to a level where no exchange of water takes place, the change in the amount of water present within the column, Awd, can be written similarly to 2.11 , where the total water flux across the atmosphere-to-ocean continent boundary...

Atmospheric electricity

The Earth is surrounded by a magnetic field, and from a height of about 80 km a substantial fraction of atmospheric gases is in an ionised state cf. section 2.3.1 . It is thus clear that electromagnetic forces play an important role in the upper atmosphere. Manifestations of electromagnetic energy in the lower parts of the atmosphere are well known in the form of lightning. Speculations on the possibility of extracting some of the electrical energy contained in a thunderstorm have appeared. An...

The Origin Of Renewable Energy Flows

Giving the pressure levels at the actual surface for comparison and Fig. 2.78 giving those for precipitation, while solar radiation on a horizontal plane is shown in Fig. 2.20 and seasonally in Fig. 3.1. Figure 2.81 shows observed surface temperatures and Figs. 2.79 and 2.80 show wind speeds w and directions d at the surface 10 m . These two quantities are derived from the zonal u and meridional v components of the wind velocity, w u2 v2 1 2, d Atan v u or 90 if u 0 and v gt 0 or v lt 0 ....

The nitrogen cycle

Another biologically important element is nitrogen, the tentative cycle of which is depicted in Fig. 2.89. Nitrogen gas N2 is a major constituent of the atmosphere, but in order for it to become available for building biological material, the nitrogen must first be fixed. By fixation is meant a process by which gaseous nitrogen N2 is transformed into a constituent of a compound, such as ammonia NH3 N2 energy 0.67 x 106 J mol-1 2N, The fixation may be accomplished by plants, but not all plants...

Power in the waves

The power of a harmonic wave, i.e. the energy flux per unit length of wave crest, passing through a plane perpendicular to the direction of propagation, is from 2.84 P pw g Uw a2 4 Pw g2 T a2 8n pa g2 a2 4a . 3.28 For the spectral distribution of energy given by the function F1 section 3.3.1 , each component must be multiplied by the group velocity d a k d k. Taking a gk 1 2 for ocean gravity waves, the group velocity becomes g 2a , and the power becomes P f F1 a da y2 g f da. 3.29 Based on...

Bga

Poleward Energy Transfer

Here S is the solar constant and c 5.7 x 108 W m2 K4 is Stefan's constant cf. section 2.A . The factor 1 4 comes because the incoming radiation on the side of the Earth facing the Sun is the integral of S cosO over the hemisphere, while the outgoing radiation is uniform over the entire sphere by definition when it is used to define an average effective temperature . The net flux of radiation at the top of the atmosphere can be written where E00 Eq on average equals -oT0 recall that fluxes away...

Renewable energy technologies in the marketplace

The penetration of renewable energy into the energy system of human settlements on Earth is from one point of view nearly 100 . The energy system seen by the inhabitants of the Earth is dominated by the environmental heat associated with the greenhouse effect, which captures solar energy and stores it within a surface-near sheet of topsoil and atmosphere around the Earth. Only 0.02 of this energy system is currently managed by human society, as illustrated in Fig. 1.1. Within this economically...

Disposition of the radiation at the Earths surface

Direct Beam Irradiance Measured

On average, roughly half of the short-wavelength radiation which reaches the Earth's surface has been scattered. Denoting the direct and scattered radiation at the Earth's surface D and d, respectively, and using the subscript s to distinguish the surface level as the subscript 0 was used for the top of the atmosphere , the total incoming short-wavelength radiation at the Earth's surface may be written for a horizontal plane. The amount of radiation reflected at the surface is where the surface...

Nuclear energy

Nuclear Binding Energy Per Nucleon

The atomic nuclei consisting of protons and neutrons carry the bulk of the mass of matter on Earth as well as in the known part of the present universe cf. section 2.A . By a nucleus is usually understood a bound system of Z protons and N neutrons unbound systems, resonances, may be formed under laboratory conditions and they are observed in cosmic ray showers for short periods of time . Such a nucleus contains an amount of nuclear binding energy, given by with the difference between the actual...