Particular

Coffari, E. (1977) 'The sun and the celestial vault' in Sayigh, A.A.M. (ed.) Solar Energy Engineering, Academic Press, London. Derives the geometric formulae. Davies, J.A. and Mackay, D.C. (1989) 'Evaluation of selected models for estimating solar radiation on a horizontal surface', Solar Energy, 43, 153-168. Dickinson, W.C. and Cheremisinoff, P.N. (eds) (1982) Solar Energy Technology Handbook, Butterworths, London. Clear diagrams of geometry. Fleagle, R.C. and Businger, J.A. (1980, 2nd edn) An...

Info

Renewable energy supply systems divide into three broad divisions 1 Mechanical supplies, such as hydro, wind, wave and tidal power. The mechanical source of power is usually transformed into electricity at high efficiency. The proportion of power in the environment extracted by the devices is determined by the mechanics of the process, linked to the variability of the source, as explained in later chapters. The proportions are, commonly, wind 35 , hydro 70-90 , wave 50 and tidal 75 . 2 Heat...

Social and environmental aspects

Present civilisation ('the age of fossil fuels') depends on distribution of energy on a very large scale. International trade in fossil fuels (coal, oil and gas) from the relatively few countries that export in large quantities represented about 4 of world trade in 2003. The concentrated lines of supply are vulnerable to disruption. Several wars can be attributed to the desire of oil-consuming counties to secure their supplies, see Yergin's notable 1992 study. The fact that oil and coal are...

Idl

Air density p depends weakly on height and meteorological condition. Wind speed generally increases with height, is affected by local topography, and varies greatly with time. These effects are considered fully in Section 9.6, and for the present we consider u0 and p constant with time and over the area of the air column. Such incompressible flow has been treated in Chapter 2 on fluid mechanics. A typical value for p is 1.2kgm-3 at sea level (Table B.1 in appendix), and useful power can be...

Energy and sustainable development Principles and major issues

Sustainable development can be broadly defined as living, producing and consuming in a manner that meets the needs of the present without compromising the ability of future generations to meet their own needs. It has become a key guiding principle for policy in the 21st century. Worldwide, politicians, industrialists, environmentalists, economists and theologians affirm that the principle must be applied at international, national and local level. Actually applying it in practice and in detail...

Superconducting electromagnetic energy storage SMES

A superconducting electromagnetic energy storage (SMES) system is a device for storing and very quickly discharging large quantities of electric power, e.g. 10 MW for < 1 s. It stores energy in the magnetic field created by the flow of DC in a coil of superconducting material that has been cryogenically cooled to 4K). At these very low temperatures, certain materials have essentially zero resistance to electric current and can maintain a DC current for years without appreciable loss. SMES...

Working digesters

Figure 11.7 shows a progression of biogas digesters, from the elementary to the sophisticated, allowing principles to be explained. a Household batch unit for the tropics. This is the simplest method, comprising an upturned metal cylinder in another larger tank, e.g. a 200-litre oil drum with the top removed. The biogas is trapped in the top cylinder to be piped to the household for cooking and lighting. The tank has to be filled for each batch with fresh animal manure, seeded if possible with...

Social and environmental considerations

Some of the potentially best locations for wind-power are in areas of natural beauty, such as coastlines, high ground and mountain passes. Proposals to use such locations usually attract opposition with arguments of loss of visual amenity, irritating acoustic noise and bird strikes. Similar objections have been raised to wind farms on farmland. Manufacturers of modern wind turbines responded by having architects influence the shape of towers and nacelles, by making the machines (especially the...

Specialised references

Born, M. and Wolf, W. (1999, 7th edn) Principles of Optics, Cambridge UP. Electromagnetic theory of absorption etc. Heavy going Brinkworth, B.J. (2001) 'Solar DHW system performance correlation revisited', Solar Energy, 71 (6), pp. 377-387. A thorough review of 'black box' comparative analysis and standards for domestic hot water (DHW) systems, including storage based on the search for comprehensive non-dimension groups of parameters which provide generalised reference methods of performance....

Sunshine hours as a measure of insolation

All major meteorological stations measure daily the hours of bright sunshine, n. Records of this quantity are available for several decades. It is traditionally measured by a Campbell-Stokes recorder (Table 4.1), which comprises a specially marked card placed behind a magnifying glass. When the sun is 'bright' a hole is burnt in the card. The observer measures n from the total burnt length on each day's card. Sunshine hours are also measured by electronic devices (see Table 4.1), but it is...

Thermodynamic considerations

In this section we shall first consider photosynthesis as an aspect of thermodynamics. The implications are important to guide strategy for renewable energy research and to give basic understanding. Consider an ideal Carnot heat engine operated from solar energy (see Section 6.9) and producing work at efficiency with a heat sink at ambient temperature, say 27 C(300K). The heat supply is solar radiation. With a flat plate absorbing collector, the maximum source temperature is about 200 C(473K)...

Trophic level photosynthesis

Animals exist by obtaining energy and materials directly or indirectly from plants. This is called the trophic (feeding) system. Figure 10.1 is an extremely simplified diagram to emphasise the essential processes of natural ecology. We should remember, however, that the box labelled 'animals' might also include the human fossil fuel-based activities of industry, transport, heating, etc. Figure 10.3 Molecular level photosynthesis. Vertical scale indicates the excitation energy of the electron....

Water desalination

To support a community in arid or desert conditions, potable, i.e. fit to drink, water must be supplied for domestic use, and other water for crops and general purposes. Many desert regions (e.g. central Australia) have regions of salt or brackish water underground, and it is usually much cheaper to purify this water than to transport fresh water from afar. Since deserts usually have large insolation, it is reasonable to use solar energy to perform this purification by distillation. The most...

Water pumping

Pumped water can be stored in tanks and reservoirs or absorbed in the ground. This capacitor-like property gives smoothing to the intermittent wind source, and makes wind-powered pumping economic. Farm scale pumps to about 10 kW maximum power are common in many countries including Argentina, Australia and the United States. The water is used mostly for cattle, irrigation or drainage. Continuity of supply is important, so large solidity multi-blade turbines are suitable, having large initial...

Electricity generation for utility grids wind farms

Commercial wind turbines are a 'mainstream' form of power generation into grid distribution and transmission networks. Machines of megawatt capacity have operated successfully for many years. Multiple numbers of machines arrayed on 'wind farms' (typically with 10-100 turbines) make convenient and manageable units. Grouping machines in this way allows savings (10-20 ) in the construction costs (e.g. getting specialised cranes etc. on site), grid connection (fewer step-up transformers required),...

Basic meteorological data and wind speed time series

All countries have national meteorological services that record and publish weather related data, including wind speeds and directions. The methods are well established and co-ordinated within the World Meteorological Organisation in Geneva, with a main aim of providing continuous runs of data for many years. Consequently only the most basic data tend to be recorded at a few permanently staffed stations using robust and trusted equipment. Unfortunately for wind power prediction, measurements of...

Classification of electricity systems using wind power

There are three classes of wind turbine electricity system, depending on the relative size of the wind-turbine generator, PT, and other electricity generators connected in parallel with it, PG (Table 9.4). Class A wind turbine capacity dominant, PT > 5PG Usually this will be a single autonomous stand-alone machine without any form of grid linking. Other generators are not expected. For electricity supply, a battery is necessary to stabilize the voltage and store the electricity. For remote...

Wind speed and direction variation with time

From Figure 9.15, note the importance of fluctuations 10 s. These not only contain significant energy, but lead to damaging stresses on wind machines. A measure of all such time variations is the turbulence intensity, equal to the standard deviation of the instantaneous wind speed divided by the mean value of the wind speed. Turbulence intensity is a useful measure over time intervals of a few minutes values of around 0.1 imply a 'smooth' wind, as over the sea, and values of around 0.25 imply a...

Wind speed analysis probability and prediction

Implementation of wind power requires knowledge of future wind speed at the turbine sites. Such information is essential for the design of the machines and the energy systems, and for the economics. The seemingly random nature of wind and the site-specific characteristics makes such information challenging, yet much can be done from statistical analysis, from correlation of measurement time-series and from meteorology. The development of wind power has led to great sophistication in the...

Electrical storage batteries and accumulators

Electricity is a high quality form of energy, and therefore great effort is made to find cheap and efficient means for storing it. A device that has electricity both as input and output is called an (electrical) accumulator or (electrical) storage battery. Batteries are an essential component of most autonomous power systems (especially with photovoltaic and small wind turbine generation), of standby and emergency power systems, and of electric vehicles. There is also a research expectation...

Diagram Of Control Between Renewable And Finite Energy Supplics

Spaghetti Diagram Renewable Energy

Here R is the total yearly energy requirement for a population of N people. E is the per capita energy-use averaged over one year, related closely to provision of food and manufactured goods. The unit of E is energy per unit time, i.e. power. On a world scale, the dominant supply of energy is from commercial sources, especially fossil fuels however, significant use of non-commercial energy may occur (e.g. fuel wood, passive solar heating), which is often absent from most official and company...

Economics Essential questions

Economics as a discipline aims to develop tools that will help people and governments make rational decisions about the allocation of scarce resources. It does this by reducing all options to monetary terms. From an economist's perspective, all actions have both costs and benefits the question to be answered is which of several alternative choices, including the status quo, has the most favourable balance. We acknowledge that economics includes more than finance (the root meaning of the word...

Ram Pump Calculations

Hydraulic Ram Pump Calculator

Further losses occur in the distribution and use of the electricity. This mechanical hydro-power device is well established for domestic and farm water pumping at remote sites, where there is a steady flow of water at a low level. The momentum of the stream flow is used to pump some of the water to a considerably higher level. For example, a stream falling 2 m below can be made to pump 10 of its flow to a height 12 m above. This is clearly a useful way of filling a header tank for piped water,...

Blade element theory

More advanced theory allows the calculation from basic principles of, for instance, the rotor power coefficient CP and hence the power production P as a function of wind speed u. We give here only an outline of this theory, called 'blade element theory' or 'stream tube theory'. As the names suggest, the theory considers blade sections (elements) and the cylinders of the airstream (streamtubes) moving onto the rotor. Each blade element is associated with a standard aerofoil cross section. The...

The lead acid battery

Lead Acid Battery Chemical Reaction

Although many electrochemical reactions are reversible in theory, few are suitable for a practical storage battery, which will be required to cycle hundreds of times between charging and discharging currents of 1-100 A or more. The most widely used storage battery is the lead acid battery, invented by Plant in 1860 and continuously developed since. Such a battery is built up from cells, one of which is shown schematically in Figure 16.3. As in all electrochemical cells, there are two electrode...

Applications and systems Standalone applications

Renewable Energy Railway

Photovoltaic modules are very reliable, have no moving parts and require no maintenance or external inputs such as fuel but only a flux of solar energy. Their first significant uses were therefore in applications where a small quantity of electric power was essential but where it was difficult or expensive to bring in fuel for conventional generators. Such applications include space satellites and autonomous, stand-alone systems in remote areas such as meteorological measurement, marine warning...

Bibliography Of Renewable Energy

Refer to the bibliographies at the end of each chapter for particular subjects and technologies. Surveys of renewable energy technology and resources Boyle, G. (ed.) (2004, 2nd edn) Renewable Energy, Oxford University Press. Excellent introduction for both scientific and non-scientific readers. Jackson, T. (ed.) (1993) Renewable Energy Prospects for implementation, Butterworth-Heinemann, Oxford. Collection of a series of articles from the journal Energy Policy, with focus on implementation...

Improved solar water heaters Sheltered black container

The container of Figure 5.1 d can be sheltered from the wind and so has convective loss reduced by encapsulating it in a covered box with a transparent lid Figure 5.1 e . Glass is often the chosen cover material, having small absorptance for the solar short wave irradiation. Clear, i.e. new, polythene sheet also has small short wave absorptance and is cheaper initially, but has to be cleaned and replaced more frequently since it degrades in the open environment. Moreover, glass has a...

Extraction techniques hot dry rock

Los Alamos Hot Dry Rock

Sources of 'hot dry rock' HDR are much more abundant than are hydrothermal regions temperatures of 200 cC are accessible under a significant proportion of the world's landmass. This has motivated considerable research in the USA and Europe on techniques to harness this heat for electricity power generation. One result has been the recognition that few basement rocks are completely dry, but there are many regions where utilisation of their geothermal heat requires 'enhanced geothermal systems',...

Batch transport

Biomass can be transported in suitable vehicles by road, rail, river or sea. However, the small density and bulky nature of most biomass as harvested means that it is rarely economic to distribute it over long distances gt 500km . Even over medium distances 100-500km , it is unlikely to be economic to distribute such biomass for its energy value alone. The guiding principle for the economic and ecological use of biomass is to interact with a 'flow' of harvested biomass which is already...

Alcoholic fermentation Alcohol production methods

Azeotropic Removal Water Chemical

Ethanol, C2H5OH, is produced naturally by certain micro-organisms from sugars under acidic conditions, i.e. pH 4 to 5. This alcoholic fermentation process is used worldwide to produce alcoholic drinks. The most common micro-organism, the yeast Saccharomyces cerevisiae, is poisoned by C2H5OH concentration greater than 10 , and so stronger concentrations up to 95 are produced by distilling and fractionating Figure 11.6 . When distilled, the remaining constant boiling point mixture is 95 ethanol...

Social implications

The Industrial Revolution in Europe and North America and industrial development in all countries have profoundly affected social structures and patterns of living. The influence of changing and new energy sources has been the driving function for much of this change. Thus there is a historic relationship between coal mining and the development of industrialised countries, which will continue for several hundred years. In the non-industrialised countries, relatively cheap oil supplies became...

Lift and drag forces fluid and turbine machinery

Here we introduce the forces of lift and drag which are as fundamental to turbine motion as they are to sailing yachts and airplanes, for they apply to any solid object immersed in a fluid flow. Obtaining rotary motion on a shaft from a flow of water or air is the basis of every turbine, relating, in this book, to hydro turbines Section 8.4 onwards for conventional hydropower, Sections 13.4 and 13.5 for tidal power , wind turbines Section 9.2 onwards , and wave power turbines, included in...

Variation with height

Wind speed varies considerably with height above ground this is referred to as wind shear. A machine with a hub height of say 30 m above other obstacles will experience far stronger winds than a person at ground level. Figure 9.17 shows the form of wind speed variation with height z in the near-to-ground boundary layer up to about 100 m. At z 0 the air speed is always zero. Within the height of local obstructions wind speed increases erratically, and violent directional fluctuations can occur...

Scientific principles of renewable energy

The definitions of renewable green and finite brown energy supplies Section 1.3.1 indicate the fundamental differences between the two forms of supply. As a consequence the efficient use of renewable energy requires the correct application of certain principles. It is essential that a sufficient renewable current is already present in the local environment. It is not good practice to try to create this energy current especially for a particular system. Renewable energy was once ridiculed by...

Anaerobic digestion for biogas Introduction

Biogas Cow

Decaying biomass and animal wastes are broken down naturally to elementary nutrients and soil humus by decomposer organisms, fungi and bacteria. The processes are favoured by wet, warm and dark conditions. The final stages are accomplished by many different species of bacteria classified as either aerobic or anaerobic. Aerobic bacteria are favoured in the presence of oxygen with the biomass carbon being fully oxidised to CO2. This composting process releases some heat slowly and locally, but is...

Diagram For Tapchan

Nearshore Wave Energy

7.0 8.0 9,0 10.0 1 1.0 12.0 13.0 14.0 15.G Figure 12.10 Scatter diagram of significant wave height Hs against zero crossing period Tz. The numbers on the graph denote the average number of occurrences of each Hs,Tz in each 1000 measurements made over one year. The most frequent occurrences are at Hs 3 m, Tz 9 s, but note that maximum likely power occurs at longer periods. these waves have equal maximum gradient or slope the maximum gradient of such waves, e.g. 1 in 20 _lines of constant wave...

Types and adaptations of photovoltaics

Band Gap And Littace Constant Solar Cell

Although the flat plate Si solar cell has been the dominant commercial product, there is a great variety of alternative types and constructions. These seek to improve efficiency and or to decrease the cost of the power produced by reducing capital cost. This section is a brief summary of a complex and continually changing scene Table 7.3 . 1 Single crystal. The cells described so far assume single-crystal base material. This can be produced by most of the methods of Section 7.6.2. In...

T

Figure 12.18 Wells turbine. a Sketch. b Motion of a turbine blade as seen by a fixed observer . Figure 12.19 Oscillating water column device with parabolic focussing, seen from above after Energetech lt www.energetech.com.au gt . What amplification might expected from a 50 m parabola for wavelengths of 25 m, 50 m, 250 m Discuss the merits of using a bigger parabola say 200m span . Are there any natural geometries which might have a similar effect Barber, N.F. 1969 Water Waves, Wykecham, London....

Wind speed probability distributions Weibull and Rayleigh

Weibull Shape Factor Increase

The analysis of Example 9.1 depended solely on field data and repetitive numerical calculation. It would be extremely useful if the important function the probability distribution of wind speed, could be given an algebraic form that accurately fitted the data. Two advantages follow 1 fewer data need be measured, and 2 analytic calculation of wind machine performance could be attempted. Using the symbols of the previous section, Therefore, by the principles of calculus For sites without long...

Biological storage

The growth of plants by photosynthesis, and the consequent storage of the solar energy, is fully discussed in Chapter 10. This energy is released in the combustion of biological and, from prehistory, of fossil fuel material. The heats of combustion of many of these materials are listed in Appendix B, Table B.6. The many chemical paths for producing biofuels are described in Chapter 11, see Figure 11.2. Some of the biofuels are liquids and gases that may be used in internal combustion engines,...

Pyrolysis destructive distillation

Destructive Distillation Models

Pyrolysis is a general term for all processes whereby organic material is heated or partially combusted to produce secondary fuels and chemical products. The input may be wood, biomass residues, municipal waste or indeed coal. The products are gases, condensed vapours as liquids, tars and oils, and solid residue as char charcoal and ash. Traditional charcoal making is pyrolysis with the vapours and gases not collected. Gasification is pyrolysis adapted to produce a maximum amount of secondary...