31 ALTERNATIVE SOURCES OF ENERGY USED IN HOUSEHOLDS-TECHNIQUES AND DEVICES

P.G. Padma Gowri

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Introduction:

 

Alternative energy is a term used for an energy source that is an alternative to using fossil fuels. Alternative sources energy is a term used for energy source that is an alternative to using fossil fuels. The fossil fuels are coal, oil, gas, uranium etc. Alternative energies are non-traditional and have low environmental impact.The alternative energy also called as renewable energy. Renewable energy is energy that is generated from natural processes that are continuously replenished. It includes sunlight, geothermal heat, wind, tides, water, and various forms of biomass. This energy cannot be exhausted and constantly renewed.The main source of alternative energy is the sun.

 

Objectives:

  • Impart knowledge on alternate sources of energy used in households
  • Explanation about of each alternative source.
  • Working of devices with solar energy, wind energy and biogas.

Renewable energy: Some of the renewable energy used as alternative energy in houses are

  •  Solar energy
  • Wind energy
  • Biomass energy
  1. Solar Energy:

Solar energy has the greatest potential of all the sources of energy and if only a small amount of this form of energy could be used, it will be the one of the most important supplies of energy in India. Its potential is 178 billion MW which is about 20,000 times the world power demand. In home we can use this solar energy in many forms. Solar water heating, solar cooling, electricity generation, solar pumping, solar furnace Most of the renewable energy comes either directly or indirectly from the sun. Sunlight, or solar energy, can be used directly for heating and lighting homes and other buildings, for generating electricity, hot water heating, and for solar cooling etc.

  1. Wind Energy:

Wind results from air in motion. Air in motion arises from a pressure gradient. The Earth’s rotation contributes the wind. The sun’s heat also drives the winds. The wind energy is captured with the wind turbine converts kinetic energy of the wind to mechanical energy that can be utilized to perform useful work or to generate electricity.

  1. Biomass Energy:

Bio mass is organic matter produced by plants, both terrestrial and aquatic and the derivatives. It includes forest crops and residues, crops grown especially for their energy content on “energy farms “and animal manure. It is considered as Sunlight and water is the main ingredients to grow plants. The organic matter that makes up those plants is known as biomass. Biomass also used to produce electricity.

  1. Solar Energy:

Technologies based on capture of heat from sun light:

4.1 Solar water heating system

 

A typical solar water heating system consists of,

  1. Solar flat collectors or set of collectors(panel)
  2. Overhead tank to provide cold water
  3. Pipelines and circulaing syatems
  4. Storage tank
  5. Control of the system

A simple solar heating system used for home utility purpose shon in fig.1

The collector is commonly a blanked metal plate with attached metal tubing and is usually provided with glass cover and a layer of insulation beneath the plate. Sun light hit fron flat collectors ,it absobrs solar energy inbetween the collectors water is circulated via tubes.

 

Solar energy captured by the collectors is used to heat the water.as the water is heated in its passage through collector ,its dencity decreases and hence it rices and flows into the top of the storage tank, colder water from the bottom of the tank has a higher dencity and so tends to sink and enter the lower heater of the collector for further heating.

 

As long as the sun shines the water will quickly circulate and getting warmer.so no need the mechanical pump to circulate water.

 

Then the hot water is collected and sitoed in storage tank which is placed above the panel.The hot water is obtain from solar water heater is used for bathing,washing,cleaning and other purposes in home.

 

Advantages:

  1. The fluid used in solar water heating systems for heat transfer and storage is water.
  2. Hot water is available 24 hours a day depending on the use and system capacity
  3. A solar water heater pays back its cost 3-4 years
  4. Solar water heaters last a long time 15 -20 years and require only simple maintenance.

4.2. Solar cookers:

 

Energy from sun used for cooking purpose. Varity of solar cookers are available in India.A box type solar cooker is shown in fig.

The cooker box consists of a top open black painted inner box kept inside of another box and the space between the two boxes is filled with glass wool insulation.

 

The upside of this cooker box is covered by two layers of transparent glass keeping a gap in between and the supporting frame of the cover is hinged with cooker box for keeping glass cover in inclined position to handle the cooking pots.

 

The cooker is to be placed facing sun, keeping longer side vertically inclined position and the inclination of the cooker box can easily be changed from 15 degree to 45 degrees with respect to the ground by the adjustable stand, attached at the back side of the box. Four number of black painted aluminum cooking pots are used and are placed side by side at the longer side of the cooker on cooking trays.

 

The cooker, presently fabricated can able to cook 2 Kg rice or equivalent food item at a time within two hours cooking is possible in between 9am to 3 pm.

 

Advantages of solar cookers:

  1. Use of solar cooker no requiring on fuel.
  2. Usage of solar cooker regularly can save 3 or 4 LPG cylinder per year
  3. They need no supervision
  4. There is no fear of scorching the food
  5. Solar cooking being a slow process ensures better and more nutritiously cooked food.
  6. Solar cookers are durable and simple to use

4.2. Solar Furnace:

 

A solar furnace is an instrument to get high temperatures by connecting solar radiations onto a specimen. The principle of working of a solar furnace is a number of tunable heliostats mirrors are arranged in terraces on a slopping surface so that, regardless of the sun’s position, they always reflect solar radiation in the same direction onto a large parabolic reflecting collector made up of many fixed mirrors attached to the face of a structure.

 

The collector then brings the radiation to a focus within small volumes. The estimated flame heat is 3800oC; the maximum heat flux is 16,000 kilo watts/ Sq.m.

 

Advantages of solar furnace:

 

1.  In a solar furnace heating is carried out without any contamination and temperature is easily controlled by changing the position of the material in focus.

2.  It gives an extremely high temperature.

3. It provides very rapid heating and cooling.

 

4.3 Solar PV panel for Electric Energy Generation:

 

Solar energy is either used directly as a source of heat and to generate electric power.

 

An energy efficient buildings balances all aspects of energy use in building-lighting, space conditioning and ventilation by providing optimizing mix of passive solar design strategies ,energy efficient equipment and renewable sources of energy.

 

Components used for solar electric energy production:

 

1.      Solar cell modules or Solar PV array

2.      Battery

3.      Power conditioning &Converter circuit

4.      Inverter circuit

The direct solar based electrical power generation systems can be developed to obtain electricity at low cost compared to conventional energy sources.

 

During the daytime the dc power generated by PV array may cater to the daytime sunlight and it convert solar energy in to electrical energy by using photo diodes.

 

The small electrical energy is added with many arrays connected in series and parallel connection to increase current and voltage capacity of solar power generation unit. Then the energy stored in batteries or directly used as electric current. The battery bank which is used to store charge for use after sunset.

 

Solar cell modules:

 

They may be tracking arrays or modules or fixed arrays. A tracking array is defined as one which is always kept mechanically perpendicular to the sun –array line so that all the times it intercepts the maximum insulation. A fixed array is usually oriented east west and tilted up at an angle approximately equal to latitude of the site.

 

Types of fixed arrays are

 

1.      Flat plate arrays

2.      Concentrating arrays.

 

Solar PV panel sub system components:

 

Inverter circuit for converting Direct current voltages to alterative current voltages with desired frequency sensors circuit breakers or timers for automatically disconnecting the battery – bank electrical load or backup generator or grid line from PV array

 

MPPT maximum power point tracker for maintaining the operation of the entire PV array at the maximum power point, irrespective of day time for this microprocessor and its allied control may also be an integral part of the power conditioner.

 

Power conditioning (PC) is the most important component it act as intelligent switch for sequentially controlling the flow of D.C charge from PV array.

 

Applications of solar PV panel:

 

1.      Water pumping ,lighting

2.      Stand along system

3.      A standalone system works entirely on its own.

4.      It is supposed to meet all the load requirements without help from any other backup energy source.

5.      These systems may or may not have electrical energy storage sub system like battery bank.

4.4  Solar Power space Cooling System for buildings:

 

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 or ammonia at a moderate pressure. The vapor could then drive a turbine which would in turn, operate a vapor –compression cooling Unit., such a low pressure vapor turbine.

 

5.  WIND ENERGY:

 

5.1 Wind mill and Wind turbine:

 

The wind mill is used for pumping water in home. A wind mill is a type of electric engine which is used to convert wind energy to mechanical energy.

 

Wind turbine is used to produce electricity.The basic device in the wind energy conversion system is the wind turbine which transfers the kinetic energy into a mechanical energy. The wind turbine is connected to the electrical generator through a coupling device gear train.

 

The output of the generator is given to the electrical grid by employing a proper controller to avoid the disturbances and to protect the system or network. The combination of wind turbine and generator is referred to as an aero generator. Both of them used to produce clean energy.

 

A small wind turbine can be used in range of power generation 50 Watts to 300 killo watts. It can be operated at the minimum wind speed of 4 meters per second. The factors that determine output from a wind energy converter the wind speed, cross section of wind swept by rotor, the overall conversion efficiency of the rotor and transmission system and generator or pump.

 

Components of wind turbine:

 

Blades –it is used to convert wind energy to rotational energy

Gear box- gear box is used to change the speed of the generator input

Electric generator

The types of electric generators are

1)      Single phase A.C Generator

2)      Three phase A.C induction generator

 

Converter /inverter unit: In this electronic switches are used to get required electric power either A.C or D.C.

Types of wind turbine are:

 

Based on the position of placement of blades and its rotational direction it’s classified

1.      Horizontal axis turbine

2.      Vertical axis turbine

Fig2 shows small domestic wind turbine installed in home.

 

Application of wind energy:

 

The energy made by windmills can be used in many ways.

Biomass Energy:

 

Biogas is a product from biomass. Biogas typically refers to a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen. Biogas can be produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste or food waste. Biogas is a renewable energy source. It is an alternative source production by using home waste products.

 

Biogas Production:

 

Biogas can be produced by anaerobic digestion with anaerobic organisms, which digest material inside a closed system, or fermentation of biodegradable materials

Anaerobic digestion

 

Anaerobic digestion is a series of biological processes in which microorganisms break down biodegradable material in the absence of oxygen. One of the end products is biogas.

 

Anaerobic organism

 

An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. Example: Protozoan’s and bacteria.

 

Fermentation process in Bio gas:

 

It is a metabolic process that converts sugar to acids and gases, or alcohol. It is used to produce specific chemical product (methane).

 

This energy release allows biogas to be used as a fuel. it can be used for any heating purpose, such as cooking. It can also be used in a gas engine to convert the energy in the gas into electricity and heat.

 

Biogas is considered to be a renewable resource because its production-and-use cycle is continuous, and it generates no net carbon dioxide. Organic material grows, is converted and used and then re grows in a continually repeating cycle.

 

From a carbon perspective, as much carbon dioxide is absorbed from the atmosphere in the growth of the primary bio-resource as is released when the material is ultimately converted to energy. The byproduct of bio gas also used as manure .It is used for agriculture purpose.

Typical composition of biogas is listed in the table:

 

Applications of Bio gas:

 

Bio gas is used for cheap and sustainable energy production. The produced bio gas is used directly or transformed in to electricity.

 

1.      Cooking

2.      Bio gas lamps

3.      Water heating

4.      Space heating

5.      It can replace compressed natural gas for use in vehicles

 

Conclusion:

 

Solar energy wind energy and bio mass are the three main alternative energy sources which can be used in households. The various methods to convert the above renewable resources in to useful energy were elaborated. The solar devices, wind turbine and biogas plants are useful for conservation of energy and reduce carbon reduction.

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