Tuesday, February 27, 2007

Biogas Technology in India; Now gaining momentum

“The biogas saves so much time! When I was using wood, I used to feel as though I was cooking for 24 hours! Now it’s just 10 minutes to boil the water - I’m a liberated woman!” Yuan Congren, 66,

“Our kitchens are a lot cleaner now – they used to be so smoky and sooty when we used wood. And it’s good to be able to come in from a day in the fields and get a good meal nice and quickly.” Yang Chunlian, 51 (Ref: Ashden Award Nominations from China)

These are the words of the beneficiaries who is utilizing Biogas Plants for their cooking needs in the Shaanxi province of China. Led by their determined founder, Wang Mingying, the Shaanxi Mothers have overseen the installation of almost 1,300 biogas systems in farming households across the province. The main source of the gas is waste from humans and household pigs. By replacing wood as a cooking fuel, it is saving families time and money, as well as contributing to China’s reforestation efforts and China has moved a lot with this effort when compared to any nation. This gives a very good message to India that if we have the dedication and right policies India is one of the best countries for Biogas Technology penetration. It is good to hear that with a total potential for 12 million home based Biogas Plants, India has achieved more than 3.8 million and has installed capacities of 11.50 MW (Off-Grid) and 34.95 MW (Grid) from Waste to Energy Projects. (Ref: MNRE -Akshaya Urja September Issue-Achievements up to 30th September 2006)

Biogas Plants; the need for changing the mind set.

As a Renewable Energy Technologist I would like to say that we should change our mind set to achieve this kind of momentum in India for Biogas Technology and its applications. So far Biogas sector has been considered as an untouchable sector by most of the industrial people related to Renewable Energy. All are giving more importance to PV technologies which is considered to be one of the costlier technologies. We should understand the Indian reality where more than 70% of its people are living in rural areas.

Biogas Technology: Importance

Biogas technology provides an alternative source of energy mainly from organic wastes. It is produced when bacteria degrade organic matter in the absence of air. Biogas contains around 55-65% of methane, 30-40% of carbon dioxide and small quantities of hydrogen, nitrogen, carbon monoxide, oxygen and hydrogen sulphide. The calorific value of biogas is appreciably high (around 4700 Kcal or 20 MJ: at around 55% methane content). The gas can effectively be utilized for generation of power through a biogas based power generation system after dewatering and cleaning of the gas. In addition, the slurry produced in the process provides valuable organic manure for farming.

Biogas Technology in India

The bio-gas technology is not new to India. Its experimentation started in 1940 when Dr. S.V. Desai after visiting Dadar sewage puri­fication station at Bombay took up an experimental gas plant at Indian Agricultural Research Institute (IARI). The cattle dung fermentation followed next which was patented by Shri Jasbhai J Patel in 1951. However, the model had undergone several modifications and in 1954 the plant was named Gramlaxmi III. The same model has been propagated by KVIC in a nation wide programme since 1962. This KVIC model has stood the test of time although many institutions and indi­viduals kept experimenting for better models and introduced several mod­els but not good enough to completely replace the KVIC model. How­ever, the late seventies saw the new Janata model where the difference in cost was about 20%. Even this model has not affected the popularity of KVIC model. It's designs etc. has been discussed later in this paper.

Support from Indian Government

All along since 1962, KVIC was the sole agency for promotion of bio-gas plants independent of government programme. The threat of oil embargo during the last Arab-Israel war in 1973 made the Government to include Bio-gas plants as alternative sources of energy to reduce the dependence on fossil oil.

Major initiative started from 1981-82 with the Programme covered under “National Project on Biogas Development” and “Community, Institutional & Night Soil based Biogas Plants Programme”(CBP / IBP/ NBP)

National Project on Biogas Development (NPBD)

· For family type biogas plants.

· Started in 1981-82 with the following objectives :

(i) To provide fuel for cooking purposes and organic manure to rural households through biogas plants;

(ii) To mitigate drudgery of rural women, reduce pressure on forest and accentuate social benefits;

(iii) To improve sanitation in villages by linking toilets with biogas plants.

· Indigenously developed models of biogas plants are promoted.

· States have designated nodal departments and nodal agencies for implementation. Besides, Khadi and Village Industries Commission, Mumbai; National Dairy Development Board, Anand (Gujarat), and national and regional level non-governmental organisations are involved in implementation.

· NPBD provides for different types of financial incentives including central subsidy to users, turn key job fee to entrepreneurs, service charges to State Nodal Departments / Agencies and support for training and publicity.

· Cumulative achievement is 35.23 lakh biogas plants up to 31st March 2003 against an estimated potential of 120 lakh biogas plants.

· An evaluation survey study conducted in 18 States involving a sample of 5,165 biogas plants by National Council of Applied Economic Research, New Delhi in 1995 indicated that on an average 87.5 per cent of biogas plants were in working order.

Community, Institutional & Night Soil based Biogas Plants Programme

Started in 1982-83 and later on in 1993-94, a scheme of setting up of large sized biogas plants linked with community toilet blocks was added.

The objectives of the Programme were :

· To recycle organic wastes for harnessing fuel-gas at community and institutional levels for various usages, including generation of motive power and electricity.

· To provide benefits of biogas technology to weaker sections of the society; and

· To recycle human waste through linking of community and institutional toilets with biogas plants for improving sanitation.

The programme of bio-gas plants are then covered under the National Biogas and Manure Management Programme (NBMMP) of Govt. of India. (2004-2005).

National Biogas and Manure Management Programme

Objectives of the Programme were:

(i) To provide fuel for cooking purposes and organic manure to rural households through family type biogas plants;
(ii) To mitigate drudgery of rural women, reduce pressure on forests and accentuate social benefits;
(iii) To improve sanitation in villages by linking sanitary toilets with biogas plants.

Current Programme of Govt. of India is a Biogas based Power Generation Programme.

Biogas based Power Generation Programme (BPGP)

Biogas based power units can be a reliable decentralized power generation option in the country. In order to promote this route of power generation, specially in the small capacity range, based on the availability of large quantity of animal wastes and wastes from forestry, rural based industries (agro / food processing), kitchen wastes, etc., a number of projects of different capacities and applications will be taken up for refining the technical know-how, developing manpower and necessary infrastructure, establishing a proper arrangement of operation & maintenance and large scale dissemination. The projects to be taken up by any village level organization, institution, private entrepreneurs etc in rural areas as well as areas covered under the Remote Village Electrification (RVE) programme of MNRE other than the industries and commercial establishments covered under Urban, Industrial & Commercial Applications (UICA) programmes for sale of electricity to individual / community / grid etc. on mutually agreeable terms. The implementing organizations must ensure that sufficient feed materials for biogas plants are available on sustainable basis and the beneficiary organization gives an undertaking that the plant would be maintained and operated for a minimum period of ten years. The central financial assistance for such projects will be limited to a maximum of Rs.30000 to 40000 per kW depending upon capacity of the power generating projects in the range of 3 kW to 250 kW of different rating limited to 40% of the plant cost.

The programme provides support for a variety of workshops, seminars, meetings, training programmes to the implementing agencies / specialized organizations / Biogas Development & Training Centres (BDTCs) for developing the required specifications and standards, discussions / deliberations on the performance of systems, setting up operation and maintenance mechanism, training of required manpower, capacity building, business meets for the prospective industries, etc. with the ultimate objective of promotion of power generation based on biogas in the country.

The quantum of financial assistance to be provided by MNRE for conducting these programmes will be decided on the basis of nature & duration of the programme, number of participants, etc. The maximum assistance, however, is limited to RS.1 00,000 per event.
Bigger Biogas Projects connected with Waste to Energy Programme

Waste-to-energy projects

MNRE (Ministry of New and Renewable Energy Sources) is implementing a programme on ‘Energy Recovery from Urban Wastes’ under which three projects for energy recovery from MSW with an aggregate capacity of 17.6 MW (megawatt) have been set up at Hyderabad, Vijayawada, and Lucknow. Other urban waste projects include a 1-MW project based on cattle manure at Haebowal, Ludhiana; a 0.5-MW project for generation of power from biogas at a sewage treatment plant at Surat; and a 0.15 MW plant for vegetable market and slaughter house wastes at Vijayawada. Another 300-kW project based on vegetable market waste is under commissioning at Chennai. All the projects are based on Biomethanation technology.


The government is now convinced that bio-gas plant technology is not a failure. However, social environment has to be more favorable for the speedier progress. For example, China has taken a rapid stride in the same field where the social environment is favorable to bio-gas technology. Fist we should think that “waste is wealth” and formulate programme for the converting waste to useful energy. More thrust should be given to the Research & Development activities in this area. Universities should encourage students to take up real time projects to solve the field problems of Biogas based technologies for cooking and electricity generation. Also entrepreneurs and private players may be encouraged to take up all issues connected with the dissemination of Biogas Plants according to the needs of the customers. For that a new mind set has to be evolved where the technocrats should sit with the rural people for providing appropriate technologies. Look at the Biogas activities going on in Nepal!.Biogas Sector Partnership (BSP) is planning to install 83,500 more biogas units in Nepal by 2009. Use of biogas in Nepal is saving the country 400,000 tons of firewood and 4.75 million liters of kerosene every year. Use of biogas means that Nepal is having less CO2 emissions…and if a very poor country like Nepal can use biogas so successfully there is every reason that India can do it too”.

Wednesday, February 21, 2007

Municipal Solid Waste Processing Technologies

Rising quality of life and high rates of resource consumption patterns have had a unintended and negative impact on the urban environment - generation of wastes far beyond the handling capacities of urban governments and agencies. Cities are now grappling with the problems of high volumes of waste, the costs involved, the disposal technologies and methodologies, and the impact of wastes on the local and global environment.

But these problems have also provided a window of opportunity for cities to find solutions - involving the community and the private sector; involving innovative technologies and disposal methods; and involving behaviour changes and awareness raising. These issues have been amply demonstrated by good practices from many cities around the world.

There is a clear need for the current approach of waste disposal that is focussed on municipalities and uses high energy/high technology, to move more towards waste processing and waste recycling (that involves public-private partnerships, aiming for eventual waste minimization - driven at the community level, and using low energy/low technology resources. Some of the defining criteria for future waste minimization programmes will include deeper community participation, understanding economic benefits/recovery of waste, focusing on life cycles (rather than end-of-pipe solutions), decentralized administration of waste, minimizing environmental impacts, reconciling investment costs with long-term goals.

Technological Options:

Initially there was a tendency to use well proven technology such as steam turbines, using conventional boilers with MSW as feed. Subsequently, many other technologies were developed and field-tested. Many other technologies are ready for field trial following successful laboratory tests. It is worth noting here that all demonstration and full-scale plants are available in the West (Parker and Roberts 1985) and they are yet to be launched commercially under Indian onditions. Although many different types of R&D projects have been taken up in India and abroad, only commercially successful projects have been described here since description of R&D projects is beyond the scope of this paper. There are mainly the following types of technologies available on commercial scale. The following technological options are available for setting up of waste-to-energy projects:

1. Sanitary Landfill
2. Incineration
3. Gasification

4. Pyrolisis
5. Anaerobic Digestion
6. Plasma Arc Gasification
7. Pellatisation

1. Sanitary Landfill:

‘Sanitary landfill’ is the scientific dumping of MSW using an engineering facility that requires detailed planning and specifications, careful construction, and efficient operation (O’Leary and Walsh 1991a). There are mainly three types of sanitary landfills namely (1) area method, (2) ramp method, and (3) trench method. In all the methods the site is first selected considering the following factors.

1. It should be at least 10 000 ft (3048 metres) away from the airport.
2. It should not be located in wetlands.
3. It should not be in flood- or earthquake-prone areas.
4. It should have a stable soil structure.

During the landfill procedure, at least 40% moisture must be maintained to achieve maximum microbial degradation. Periodically the leach ate collection in the bottom needs to be pumped out to drying beds specially prepared for this purpose. Due to scientific land filling, the maturity is achieved faster and hence gas collection starts even during the landfill procedure. The gas generation and complete extraction are achieved even after closure (say up to 10 years). This is faster than the ordinary landfill where gas extraction continues even up to 50 years. Compost retrieval is an optional choice depending on site condition and commercial feasibility. In addition to the above technologies, there are other emerging technologies such as Plasma Arc Technology is being attempted for energy recovery from waste.

2. Incineration:

The scientific sanitary landfills also have many problems. The main problem is the availability of land located where transportation is economically viable, and with minimum public objection. Accumulation of such a large volume of waste for long time is dangerous for the environment. Hence the best way to solve the problem is to reduce the volume by burning. Even 90% volume reduction can be achieved by burning. But uncontrolled burning causes air pollution and the heat thus generated is wasted and incineration is a practical solution. Incineration technology is the controlled combustion of waste with the recovery of heat to produce steam that in turn produces power through steam turbines (Bhide and Sunderesan 1983). Figure 3 shows that MSW after pretreatment is fed to the boiler of suitable choice wherein high pressure steam is used to produce power through a steam turbine. Proper air pollution control measures are taken and ash from the boiler is dumped in the nearby landfill.


Depending upon the pretreatment methodology, there are mainly two types of MSW combustion technologies available.

1. Unprocessed solid waste combustion technology (also known as mass burning)
2. Processed solid waste combustion technology (also known as RDF burning)

3. Gasification:

The extraction of maximum heat from a given fuel depends upon the efficiency of mixing the fuel with oxygen or air. This is perfectly achieved in the case of gaseous fuels. That is why conversion of solid waste into gaseous fuel is considered one of the best options. As described in Figure 4, MSW after pre-treatment is fed into the main gasification chamber wherein biomass is converted into gas, which, in turn, produces power after cooling and cleaning through gas engine connected to electric generator. A gasifier essentially carry out pyrolysis under limited air in the first stage followed by higher temperature reactions of the pyrolysis products to generate low molecular weight gases such as CO (carbon monoxide), CH4, hydrogen, nitrogen, etc. The gas known as producer gas has the calorific value of 1000–1200 kcal/nm3, which could be used in IC engines for direct power generation or in boilers for steam generation to produce power.

4. Pyrolisis:

Pyrolysis is a thermal decomposition process that occurs at moderate temperatures with a high heat transfer rate to the biomass particles and a short hot vapor residence time in the reaction zone. Several reactor configurations have been shown to assure this condition and to achieve yields of liquid product as high as 75% based on the starting dry biomass weight . They include bubbling fluid beds, circulating and transported beds, cyclonic reactors, and ablative reactors.
Fast pyrolysis of biomass produces a liquid product, pyrolysis oil or bio-oil that can be readily stored and transported. Pyrolysis oil is a renewable liquid fuel and can also be used for production of chemicals. Fast pyrolysis has now achieved a commercial success for production of chemicals and is being actively developed for producing liquid fuels. Pyrolysis oil has been successfully tested in engines, turbines and boilers, and been upgraded to high quality hydrocarbon fuels although at a presently unacceptable energetic and financial cost.

In the 1990s several fast pyrolysis technologies reached near-commercial status. Six circulating fluidized bed plants have been constructed by Ensyn Technologies, with the largest having a nominal capacity of 50 t/day operated for Red Arrow Products Co., Inc. in Wisconsin. DynaMotive (Vancouver, Canada) demonstrated the bubbling fluidized bed process at 10 t/day of biomass and is scaling up the plant to 100 t/day. BTG (The Netherlands) operates a rotary cone reactor system at 5 t/day and is proposing to scale the plant up to 50 t/d. Fortum has a 12 t/day pilot plant in Finland. The yields and properties of the generated liquid product, bio-oil, depend on the feedstock, the process type and conditions, and the product collection efficiency.
Biomass Program researchers use both vortex (cyclonic) and fluidized bed reactors for pyrolyzing biomass. The fluidized bed reactor of the Thermochemical Users Facility at the National Renewable Energy Laboratory is a 1.8 m high cylindrical vessel of 20 cm diameter in the lower (fluidization) zone, expanded to 36 cm diameter in the freeboard section. It is equipped in a perforated gas distribution plate and an internal cyclone to retain entrained bed media (typically sand). The reactor is heated electrically and can operate at temperatures up to 700°C at a throughput of 15-20 kg/h of biomass.
Recently, a catalytic steam reformer was coupled to the pyrolysis/gasification system. Like the pyrolyzer, the reformer is an externally heated fluidized bed reactor that will be used to produce hydrogen from pyrolysis gas and vapors generated in the first stage of the process and to clean the gas from tars.

5. Anaerobic Digestion:

Municipal solid waste is a heterogeneous waste and contains the following fractions:

a. Putrescible fraction: This is also called digestible fraction and contains biodegradable organic matter such as kitchen waste, vegetable market waste, paper, grass cutting, and yard trimmings. Putrescible fraction represents 40% of MSW in India.

b. Combustible fraction: Also known as refractory organics, these are either slowly digestible or indigestible organic matter such as wood, plastics, rubber, or other synthetics. They represent around 20% of MSW in India.

c. Inert fraction: They are typically non-digestible and non-combustibles such as stones, sand, glass, and metals. They represent 15% of the MSW in India.

d. Remaining 25% is the moisture content

The putrescible fraction is ideally suited to produce biogas and the remaining slurry is a good fertilizer. There are different types of biogas technologies available. The digestible organic fraction thus obtained is kept as pulp in hydrolysis tanks for breaking them into smaller molecules. The hydrolysed pulp is then fed into anaerobic digestion tanks. Here it is digested anaerobically (in absence of air), in the specially designed digesters. Under this active bacterial activity, the digested pulp produces the combustible gas CH4, and inert gas, CO2. The CH4 gas is then used to produce power through a biogas engine connected to electric generator. The remaining digestate (slurry) is a soil conditioner of good quality and free from pathogens. With the help of a solid/liquid separator, organic fertilizer is obtained and the treated water can be safely used for irrigation.


Depending upon the MSW quality and quantity, local environmental and climatic condition, there are various commercially viable technologies available globally. In all the technologies the following steps are involved.

1. Sorting. The putrescible fraction is separated either manually or mechanically.

2. Particle size reduction. To provide maximum surface area to the bacteria, the particle size reduction is carried out by using screw cutting, milling, and drumming, pulping, or shredding machines.

3. Digestion. The material is then fed into anaerobic digesters for gas generation.

4. Post treatment. The slurry or digestate is matured for two to four weeks to make an agriculture or horticulture quality fertilizer or soil conditioner.

The core of the whole technology is the anaerobic digestion. There are many technologies for effective digestion which differ from each other depending upon their digestion parameters.

6. Plasma Arc Gasification:

This system uses a heat source called a plasma arc flame. Two electrodes are precisely shaped and distanced. A highly ionized gas is passed between them and high voltage discharge occurs between the electrodes causing a hot plasma zone to be created. The plasma gas around the electrodes is of extremely high temperature ranging from 5600–30 000 °F (3093–16 649 °C). At such a high temperature the molecules within that zone dissociates into their individual atoms. Thereafter, ‘quenching’ allows for the controlled cooling of the hot plasma gas. The reintegration process produces synthesis gas. Since the process occurs in the vacuum the intermediary products (pollution causing) NOx and SOx (oxides of sulphur) are not formed. It takes care of all organic matters whether biodegradable or not. The cost is expected to be Rs 40–50 million rupees.

7. Pelletization:

Pelletization is a process of producing fuel pellets from solid waste. The complete process involves drying, removal of non-combustibles, grinding, mixing, and production of pellets under high pressure. Usually, the conversion time is 25 minutes. The calorific value of raw garbage is around 1000 kcal/kg while the pellets also known as RDF have the calorific value around 4000 Kcal/kg. About 15–20 tonnes of fuel pellets can be produced after treatment of 100 tonnes of raw garbage. These pellets could be used for heating in the boilers and the steam thus generated, in turn, is used to produce power. A power plant of 5 MW based on RDF will need 12 acres (4.85 hectares) of land and 600 TPD of raw garbage.

The major advantages of setting up of waste-to-energy projects are:

1. The quantity of waste gets reduced by nearly 60% to 90%, depending upon the waste composition and the technology adopted .

2. Demand for land, which is already scarce in cities, for land filling is reduced;

3. The cost of transportation of waste to far-away landfill sites gets reduced; and

There is net reduction in environmental pollution.

Apart from generating power from the waste, the slurry produced from biomethanation technology acts as a good fertilizer.

The growth of this sector has been affected on account of the following limitations/ constraints:

1. Most of the proven and commercial technologies in respect of urban wastes are required to be imported;

2. The costs of the projects especially based on biomethanation technology are high as critical equipment for a project is required to be imported.

3. Lack of financial resources with Municipal Corporations/Urban Local Bodies.

4. Lack of conducive Policy Guidelines from State Govts. in respect of allotment of land, supply of garbage and power purchase / evacuation facilities.

Tuesday, February 13, 2007

Hybrid Systems in Developing Countries

A common hybrid system for the application in developing countries generally consists of the following main components:

1. A primary source of energy, i.e. a renewable energy resource;
2. A secondary source of energy for supply in case of shortages, i.e. a diesel genset;
3. A storage system to guarantee a stable output during short times of shortages
4. A charge controller;
5. Installation material (safety boxes, cables, plugs, etc.);
6. The appliances (lighting, TV/radio, etc.).

Usually, a DC/AC inverter needs to be installed additionally. All these components and the problems related to their applications. Hybrid systems are applied in areas where permanent and reliable availability of electricity supply is an important issue. Maintaining high availability with renewable energies alone usually requires big renewable energy generators, which can be avoided with hybrid systems. At favourable weather conditions, the renewable part of the system satisfies the energy demand, using the energy surplus to load the battery. The batteries act as “buffers”, maintaining a stable energy supply during short periods of time, i.e. in cases of low sunlight or low wind. Moreover, the battery serves to meet peak demands, which might not be satisfied by the renewable system alone. A charge controller regulates the state of load of the battery, controlling the battery not to be overloaded. The complementary resource produces the required energy at times of imminent deep discharge of the battery, at the same time loading the battery. Storage systems in hybrid systems in developing countries are usually battery aggregates maintaining a stable output over a time frame of one or more days. Rotating masses can be used for shorter time frames (seconds), combustion aggregates need to be used for medium- or long-term storage. A future option might be the hydrogen fuel cell.

Technologies for Hybrid Systems in Developing Countries

1. PV/Diesel

Combining Photovoltaic arrays and a diesel genset provides a rather simple solution and is feasible for regions with good solar resources. PV/Diesel hybrid systems require a DC/AC-inverter if appliances need alternating current, since PV modules provide direct current. Compared to the common solution for rural off-grid electrification using diesel gensets alone, the hybrid solution using photovoltaic offers great potential in saving fuel. Experiences show annual fuel savings of more than 80% compared to stand-alone mini-grids on diesel genset basis, depending on the regional conditions and the design of the system The CO2 emissions decrease correspondingly. Naturally, the observed fuel saving varies over the year. The solar generator can provide about 100% of the electricity during summertime, while in winter this figure is less. Typically, in climatic regions like Germany a PV/Diesel hybrid system is designed to provide around 50% of the electricity from photovoltaic during winter, the rest being supplied with the diesel genset.

2. Wind/Diesel

Wind/Diesel combinations are, in principal, built up in the same way as are PV/Diesel systems. From a perspective of financial competitiveness, they can be applied in regions where average wind speed is around 3.5 m/s already. If wind speed is sufficient, the wind turbine is in charge of the provision of energy. During short periods of time with low winds, the battery maintains a stable system, being replaced by the diesel generating set when low winds occur over longer periods of time.

3. PV/Wind and PV/Wind/Diesel

In some regions the exploitation of both wind and solar resources can become favourable, i.e. at coastal or mountain areas with high degree of solar radiation. Of utmost importance is here that wind and solar energy supply complement each other so that energy provision is possible over the whole year. While for the other hybrid systems applying diesel gensets, the objective in designing the system is to maximise the exploitation of the renewable energy resource, the situation is different
for PV/Wind systems. Here, accurate assessment of the resources is essential for the decision on the appropriate system design. A PV/Wind hybrid system is able to provide energy all time of the day, if weather conditions are favourable. However, breakdowns in energy supply are possible, which is not suitable for some non-household applications, i.e. hospital electrification. Thus, a PV/Wind hybrid system might ideally be supported by an additional diesel generating set for times of extremely unfavourable weather conditions. The PV/Wind/Diesel hybrid system has proven successful in Germany, being highly reliable and resulting in a further reduction of diesel compared to other hybrid systems. This is obviously due to the fact that PV/Wind/Diesel hybrid systems involve a higher share of renewable energy resources. For the application in developing countries, however, it must be doubted whether this effect of further reduction of diesel use can trade off the higher investment and operation costs.

4. Wind/Large Hydropower

On a seasonal basis, the two resources wind and hydropower tend to complement each other to some extent. Especially in winter, when river flows are low, wind has the potential to take over electricity supply. However, during late summer, both resources might become low, and the combination of both is then disadvantageous. Moreover, while hydro generators on rivers are usually at lower levels, wind resources are better at high elevations. For constant electricity generation, another energy resource would therefore be necessary. Since the combination of wind and hydropower offers just limited advantages, it is unlikely that these resources are combined in a project in developing countries, since this opportunity does not seem economically attractive. However, for some locations the situation might be different, so that the feasibility of Wind/Large Hydropower systems needs to be assessed for each case individually.

5. Wind/Micro-Hydro and PV/Micro-Hydro

While hybrid systems with large-scale hydropower generators seem unattractive, microhydropower is more feasible. Micro-hydroelectric generators are turbines that are able to operate under low elevation head or low volumetric flow rate conditions, being suitable for small rivers. Where rivers have inconsistent flow characteristics (dry in summer, frozen in winter), a hybrid system applying wind or PV support can be attractive. A careful assessment of water resources is therefore essential.

6. PV-Wind-Bio Energy

Hybrid Systems with PV-Wind or PV-Diesel or PV-Wind- Diesel are common now in developing countries for decentralized power solutions. But Renewable Hybrid Systems with Bio Energy mix is not so common, but now gaining importance in countries where there is good possibility of utilizing biomass resources. The installation of hybrid renewable energy supply systems based upon PV, wind and bio-energy becomes an optimal energy solution, especially in rural areas where for various reasons the potential for development of various renewable energy systems exist. Also renewable energies such as solar, wind and biomass are becoming popular in countries which emphasize clean energy development in national energy policy. Photovoltaic technology, wind technology and bio energy can be combined together to form a renewable energy hybrid energy system. Such combinations can make use of the best of each, while offsetting weaknesses. This idea basically attempts to establish an optimal energy system as a whole, synthesizing these renewable energy sources, and simultaneously improving the quality and availability of power.

The need for Hybridisation of Renewable Energy Sources

The major issues hindering the large deployment of renewable energy technologies have been high up-front capital costs, intermittent in supplying energy, etc. Recent trend of the costs of renewable energy technologies shows a declination because of innovation and improvement in manufacturing technology. In remote areas supply of fossil fuels is very costly due to poor transport infrastructure. Almost all fossil fuels need to be imported. Most of the energy is supplied through diesel generators and or through independent renewable power plants (wind, PV, or micro-hydro plants). In most of the cases, these supply systems are not cost effective because they function with a very low load factor. In many cases, these stand-alone plants have poor reliability and operational flexibility in electricity supply. However, it is necessary to increase the reliability or the power supply from these technologies. By hybridization different renewable energy technologies, it has been shown that the supply of energy can be guaranteed at minimum lifecycle cost. It is obvious that proper management of available natural resources and the energy technology is vital issue for satisfying the energy demand in a sustainable manner locally and globally. The direct integration of these different sources into a hybrid system has been made practically possible by the newly-developed PV-Wind-Bio hybrid system from SunTechnics. This lecture explains the different electrification possibilities as well as their advantages and special features.

The need for hybridization of resources

There are three main attributes of renewable energy resources: free availability, allowance for modular technology and emission free. One of the greatest problems in utilizing renewable energy sources is their low density of power and intermittent nature depending largely upon local site and unpredictable weather conditions. The solution to this problem may be the utilization of these sources in random. Renewable sources are available with different intensity at different period of the year. This characteristic of renewable resources can be used through a system in such a way that they are able to supply energy on demand. Such a system is called hybrid power system. A hybrid power plant with an intelligent power management system can increase reliability of power supply with minimum impact on ecology.
In the remote and isolated areas far from the grid, it is impossible to meet the small power load either through long-distance distribution network or by the conventional generation. This is due to the high cost of transmission lines and higher transmission losses that accompany distribution of centrally generated power to remote areas. The power-supply for these areas mainly depends on "stand alone" diesel or hybrid generation systems, which are now a possible economical alternative to running the grid all the way to remote area. An important drawback associated with monovalent diesel, wind or PV systems, is their inability to guarantee reliable, uninterrupted output at a cost that can be comparable with the conventionally produced power. Therefore, a number of off-grid hybrid systems, which received more and more attentions from the whole world, have been installed and tested in the past decades. These systems are all designed to yield a high reliability of power supply. The results obviously show that, renewable energy-based off-grid hybrid generation systems can compete with power from the gird in remote locations, where the grid is either not feasible or nonexistent. For example, hybrid systems such as wind/ photovoltaics (PV), wind/diesel are now proven technologies and an option for the supply of small electrical loads at remote locations. Because of the existence of large remote and isolated areas with abundant renewable energy resources in the developing world, the renewable energy-based hybrid generation systems, especially wind/PV, wind/diesel hybrid systems are an effective option for solving the power-supply and poverty-removal problem.

Monday, February 05, 2007

Solar Village Electrification Project in Kerala - Lights to the Tribal Community

Kerala is one of the most beautiful States in southern India, known as " The God's Own Country". Agency for Non-conventional Energy and Rural Technology (ANERT) is an autonomous institution under the Power Department of Government of Kerala. ANERT is also functioning as the State Nodal Agency (S.N.A) of the Ministry of New and Renewable Energy (MNRE), Government of India. All these years, ANERT has also made a substantial contribution in the field of Renewable Energy Sources, with special emphasis on Solar Energy. ANERT's objective was to extend our help to the tribal people who are away from the main stream of life and living in the forest where basic amenities is not available. These people are away from the conventional utility lines. The existing Central Government rules about forests will not permit the State utility authorities to extend the electricity lines through the forest area.

Giving light to the people will pave the way for further development to the society in all respects. It is a known fact that solar electricity is a right option for the decentralised electricity generation. This Green Energy generation will not affect the environment and hence protect the existing bio-diversity of our evergreen forests. It is non-hazardous, non-polluting and perennial. It is available abundantly at free of cost.

A preliminary study was conducted in the remote colonies to provide at least two home lighting systems in every house. The colonies were categorized into two groups; colonies with clustered houses and colonies with scattered houses. Colonies with clustered houses were prefered for centralised PV Power Plants and colonies with scattered houses are selected for the distribution of Slar Home Systems.
I was fortunate to head the Solar Photovolatic Group in ANERT during the first and second phase of the Solar Village Electrification Project. Engineers of ANERT in different districts conducted a detailed study in each districts regarding the remote hamlets, about the inhabitants, geographic location and the distance of the hamlets from the convetional utility lines. Solar Radiation Data of the particular location is studied and analysed. The data consisting of the number of people in a family, the location of each colony, the Grama Panchayat concerned, the Block Panchayat and the District , the category of families , the distance from the conventional electricity lines etc. are collected and formulated. Solar Home Lighting Systems were proposed for the colonies where the houses are scattered in nature and Solar Stand-alone PV Power Plants were proposed for the colonies where the houses are centrally situated. Stand-alone PV Power Plants were sized, designed suiting to the local requirements of the Tribal Hamlets.


74th and 75th amendment of the Indian Constitution permit Grama Panchayaths for micro power generation using renewable energy sources. Also as per the Kerala Panchayathraj Act, Renewable Energy and its dissemination is the subject of interest of the Local Self Governments and they are empowered to do so. ANERT had conducted District level awareness workshops participating the people's representatives of the Local Self Governments, representatives of NGOs, officials from the District Planning Office, experts from the renewable energy field, officials from the scheduled cast and scheduled tribe departments as a preliminary step before the installation work.


The project includes 11 numbers of Stand-alone Photovoltaic Power Plants with a total installed capacity of 40.02 kWp, about 20,000 numbers of Solar Home Lighting Systems and a total of 896 Solar Street Lighting Systems. All these systems were installed with the involvement of local communities. Some of the sites are very remote in such a way that it required two to three days of trecking to reach there. In such places, mostly tribal hamlets, the materials were transported to the site through head load. Even we used elephants to transport PV materials to a remote Tribal Settlement in Idukki called Mavalikkudi. The cost of the project has been shared by MNRE ( Ministry of New and Renewble Energy), Govt. of India and ANERT. Also the concerned Local Self Governments came with some contribution from their budget allocations.

Sustainabilty was an important consideration for the success of this project. With this concept in mind Beneficiary Societies were constituted under the Charitable Societies Act for the upkeep of the PV systems. Each member of the houses in each colony is a member of the Society. These members should contribute Rs.25 per month to the society for the maintenance work including the replacement cost of batteries after 5 years of Warantee. Two representatives from these colonies were trained for the maintenance of the systems from the day of installation itself. The maintenance committee entrusted these trained people for the day-to-day maintenance of the system. However, in the event of some major maintenance, the contractors were entrusted to do the necessary repair work. For this purpose, Guarantee and an Annual Maintenance Contracts were also provided in the contract.
As a whole it was a wonderful project from ANERT's side for the tribal people. It created more enthusiasm to their children for their studies. Even some families extended their working hours for their home based industries because of the availabilty of lights. It was a right project for the right people.

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