12 May 2011

Energy Physics

1. What are the various forms of energy sources?

    The energy sources available can be divided into three types.
        1. Primary Energy Sources
        2. Secondary Energy Sources
        3. Supplementary Sources

2. What are primary and secondary energy sources?

I. Primary Energy Sources:

          It can be defined as sources which provide a net supply of energy. Coal, natural gas, oil and nuclear energy using breeder reactor are examples of this type. The energy required to obtain these fuels is much less than what they can produce by combustion or nuclear reaction. Their energy yield ratio is very high. The yield ratio is defined as the energy fed back by the material to the energy received from the environment. The primary fuels only can accelerate growth but their supply is limited. It becomes very essential to use these fuels sparingly. Primary fuels contributes considerably to the energy supply.

II. Secondary Sources:

          Secondary fuels produce no net energy. Though it may be necessary for the economy, these may not yield net energy. Intensive agricultural is an example wherein terms of energy the yield is less than the input. Secondary sources are like solar energy, wind energy, water energy etc.

sources are like solar energy, wind energy, water energy etc.

3. Write any two obstackles to implementation of renewable energy systems.

1. Inadequate documentation and evaluation of past experience, a paucity of validated field performance data and a lack of clear priorities for future work.


2. Weak or non-existent institutions and policies to finance and commercialize renewable energy systems. With regard to energy planning, separate and completely uncoordinated organizations are often responsible for petroleum, electricity, coal, forestry, fuelwood, renewable resources and conservation.

4. Write any two advantages of renewable energy system.

1. Renewable energy is an indigeneous resource available in considerable quantities to all developing nations and capable, in principle, of having a significant local, regional or national economic impact. The use of renewable energy could help to conserve foreign exchange and generate local employment if conservation technologies are designed, manufactured, assembled and installed locally.


2. Several renewable options are financially and economically competitive for certain applications, such as in remote locations, where the costs of transmitting electrical power or transporting conventional fuels are high, or in those well endowed with biomass, hydro or geothermal resources.

5. Mention various forms of renewable energy?

Various forms of renewable energy are i) Solar energy, ii) Wind energy, iii) Bio energy, iv) Hydro energy, v) Geothermal energy and vi) Wave and tidal energy.

6. What are the advantages of solar energy?

   1. Saves you money                           2. Environmentally friendly
   3. Independent/ semi-independent    4. Low/ no maintenance

7. Write any four disadvantages of solar energy?
  • The initial cost is the main disadvantage of installing a solar energy system, largely because of the high cost of the semi-conducting materials used in building one. 
  • The cost of solar energy is also high compared to non-renewable utility-supplied electricity. As energy shortages are becoming more common, solar energy is becoming more price-competitive.
  • Solar panels require quite a large area for installation to achieve a good level of efficiency.
  • The efficiency of the system also relies on the location of the sun, although this problem can be overcome with the installation of certain components.
8. Write a short note on water desalination?

          The low cost thermal energy can used to desalt or otherwise purify water for drinking or irrigation.
          Multi-flash desalination units along with a solar pond is an attractive proposition for getting distilled water because the multi-flash desalination plant below 100ºC which can well be achieved by a solar pond. This system will be suitable at places where portable water is in short supply and brackish water is available. It has been estimated that about 4700 m3/day distilled water can be obtained from a pond of 0.31km2 area with a multi-effort distillation unit. The cost of distilled water appears to be high for industrialized countries but can be used in developing countries where there is a shortage of potable water. Moreover this type of desalination plant produces five times more distilled water than the conventional basin type solar still.

9. What is Solar Pond?

A solar pond is an integral collection and storage device of solar energy.

10. Do solar ponds work in winter?

          Yes! Even when covered with a sheet of ice and surrounded by drifts of snow, the El Paso Solar Pond's lower zones produced temperatures of 154°F -- hot enough to generate electricity.

11. Why consider a solar pond?

          Solar ponds have several advantages. They have a low cost per unit area of collection and an inherent storage capacity. Also, they can be easily constructed over large areas, enabling the diffuse solar resource to be concentrated on a grand scale.

12. What are the environmental advantages of a solar pond?

          Solar ponds address three environmental issues arising from the use of conventional fuels. First, heat energy is provided without burning fuel, thus reducing pollution. Second, conventional energy resources are conserved. Third, solar ponds coupled with desalting units can be used to purify contaminated or minerally-impaired water, and the pond itself can become the receptacle for the waste products.

13. What are the main applications of solar ponds?

   1. Heating and Cooling of Buildings
   2. Production of Power
   3. Industrial Process Heat
   4. Desalination
   5. Heating animal housing and drying crops on farms
   6. Heat for biomass conversion

14. Write a short note on “Space Cooling”.

          The major current interest is in mechanical cooling systems that depend on solar heat for their operation and are unaffected by atmospheric humidity. The two most common refrigeration techniques are vapor compression and absorption and, in principle, both could be adopted for use with solar energy, although the temperatures required are higher than those adequate for space heating. In the former procedure, solar heated water could vaporize propane or ammonia at a moderate pressure. The vapour could then drive a turbine which would in turn, operate a vapour-compression cooling unit. Such a low pressure vapor turbine, however, would inevitably have a very low efficiency. Futher-more, propane is highly flammable whereas ammonia forms a noxious gas.
          Absorption cooling with solar energy, which is regarded as more practical, is possible with current technology although improvements in design would be desirable.

15. Define energy storage?

          Energy is useful only if available when and where it is wanted. keeping it available until when it is wanted is called storage.

16. What is energy distribution?

          Energy is useful only if available when and where it is wanted. Carrying energy to where it is wanted is called distribution.

17. Write any four important methods of energy storage?

      1. Mechanical energy storage      2. Electrical storage : the lead acid battery
      3. Chemical energy storage         4. Biological storage

18. What are the patterns of energy consumption?

     1. Domestic 2. Industrial 3. Transportation 4. Agricultural 

19. What are the sources of biomass energy?
      Biomass can come from a large variety of sources. Often, agricultural and forest industry by-products can be used, which include paper mill residue and lumber mill scrap. Municipal wastes and surplus crops can also be utilized. Dedicated energy crops, such as fast growing trees and grasses can be used as sustainable long-term sources of biomass.

20. Write any four advantages of biomass energy.
  • Reduces need for fossil fuels for the production of heat, steam, and electricity for residential, industrial & agricultural use
  • Available almost everywhere
  • Biomass fuel from agriculture wastes may be a secondary product that adds value to agricultural crop
  • May reduce municipal, agricultural and industrial waste
21. Write any four disadvantages of biomass energy.
  • Agricultural wastes will not be available if the basic crop is no longer grown
  • Additional work is needed in areas such as harvesting methods
  • More expensive than conventional fossil fuels
  • A less concentrated form of energy, making it less efficient
22. Write a short note on OTEC.

     In this indirect form of solar energy at sea, collection and storage are free. The surface of the water acts as the collector for solar heat while the upper laver of the sea constitutes infinite heat storage reservoir. Thus heat contained in the oceans, which is solar in origin, could be converted into electricity by utilizing the fact that the temperature difference between the warm surface water of the tropical oceans and the colder waters in the depths is about 20 – 25 degree Kelvin. Warm surface water could be used to heat some low boiling organic fluid, the vapour of which would run a heat engine. The exit vapour would condensed by pumping cold water from the deeper regions. The amount of energy available for ocean thermal power generation is enormous, and is replenished continuously.

23. Using biomass as fuel, how much carbon dioxide will be released?

          Biomass does not add carbon-dioxide to the atmosphere as it absorbs the same amount of carbon is growing as it releases when consumed as fuel.

24. Write short note on biogas?

Biogas is a clean and efficient fuel, generated from cow-dung, human waste or any kind of biological materials derived through anaerobic fermentation process. The biogas consists of 60% methane with rest mainly carbon-di-oxide. Biogas is a safe fuel for cooking and lighting. By-product is usable as high grade manure.

25. What is the average wind speed (km/h) considered as Good for operation of wind mill?

          Wind speed of 25 Kmh or 15.5 Mph is considered to be Good for power generation.

 26. Mention various types of biomass or bio power?

          Biopower, or biomass power, is the use of biomass to generate electricity. There are six major types of biopower systems: direct-fired, cofiring, gasification, anaerobic digestion, pyrolysis, and small - modular.

27. What is the energy crisis?

          A energy crisis is defined as any great shortfall in the supply of energy to an economy.

28. What are the alternative sources of energy?

          The alternative sources of energy are the ones we hope to develop the future. They are solar, geothermal, tidal, wind and synthetic fuel.

29. Write short note on “Hydrogen Energy”.

          Hydrogen as an energy can play an important role as an alternative to conventional fuels provided its technical problems of production, storage and transportation can be resolved satisfactorily and the cost could be brought down to acceptable limits. One of the most attractive features of hydrogen as an energy carrier is that it can be produced from water which is abundantly available in nature. Hydrogen has the highest energy content per unit of mass any chemical fuel and can be substituted for hydrocarbons in a broad range of applications, often with increased combustion efficiency. Its burning process is non-polluting and it can be used in fuel cells to produce both electricity and useful heat.