A

National Level Paper

Presentation on

SOLAR – WIND HYBRID SYSTEM

Submitted By

Atul M. Zope Rameshwar V. Wagh

Zope.atul@gmail.com rameshwarwagh111@gmail.com

Department of Mechanical Engineering

Godavari College of Engineering, Jalgaon

Year 2010 - 2011

SOLAR – WIND HYBRID SYSTEM

Atul M. Zope1, Rameshwar Wagh2 1, 2, GF’s Godavari College of Engineering, North Maharashtra University, Jalgaon, India

ABSTRACT

Energy is vital for sustaining life on earth. Energy was, is and will remain the basic foundation which

determines the stability of economic development any nation. It is needed to increase the quality of life at

present the power shortage is a major hurdle in progress of the nation. Hence there is a need optimally and

economically design and develop all the possible non-conventional energy resources to reduce the void

between supply and demand of electrical power. The detailed study of electrical power systems is a key

element of many curricula in Industrial Technology. The set-up consists of a photo-voltaic solar-cell array, a

mast mounted wind generator, lead-acid storage batteries, etc. This hybrid solar-wind power generating

system is extensively used to illustrate electrical concepts in hands-on laboratories and demonstrations in the

Industrial Technology curriculum. These systems give better reliability, reduce pollution and are a good tool

for the utility for demand side management. In coming years, man will have to increasingly depend on

renewable energy sources. Because of the disadvantages involved in using solar or wind energy individually,

a hybrid system which avoids the individual advantages will become more famous in coming years. Also the

renewable energy equipments will become cheaper and efficient with modern technology.

INDEX

Sr. No. Title Page No.

1 Introduction 1

2 Design Approaches 2

3 Working of Wind – Solar Hybrid System 2

4 Methodology 3

5 Establishment of A Solar Wind Hybrid Unit 4

6 Existence of Solar Wind Hybrid System 5

7 Overall View of The Plant 7

8 Conclusion 8

9 References 8

I. INTRODUCTION

Around 2 billion people world-wide do not have access to electricity services, of which the main

share in rural areas in developing countries. The fact that rural electricity supply has been regarded as

essential for economic development. It is nowadays a main focus in international development cooperation.

A renewable energy resource is a favorable alternative for rural energy supply. In order to handle their

fluctuating nature, however, hybrid systems can be applied. These systems use different energy generators in

combination, by this maintaining a stable energy supply in times of shortages of one the energy resources.

Main hope attributed to these systems is their good potential for economic development.

Hybrid systems are another approach towards decentralized electrification, basically by combining

the technologies presented above. They can be designed as stand-alone mini-grids or in smaller scale as

household systems. One of the main problems of solar as well as wind energy is the fluctuation of energy

supply, resulting in intermittent delivery of power and causing problems if supply continuity is required.

This can be avoided by the use of hybrid systems which can be defined as “a combination of different, but

complementary energy supply systems at the same place, i.e. .solar cells and wind power plants”

A hybrid energy system consists of two or more energy systems, an energy storage system, power

conditioning equipment and a controller. A hybrid energy system may or may not be connected to the grid.

Examples of energy systems commonly used in hybrid configurations are small wind turbines, photovoltaic

systems, micro hydro, diesel generator, fuel cells, micro turbines, and Stirling engines. Typically batteries

are used for energy storage but other options are flywheels and hydrogen energy storage systems. Power

conditioning equipment consists of one or more of the following: controlled rectifiers, inverters/grid-tie

inverters, charge controllers, and DC-DC converters. The task for the hybrid energy system controller is to

control the interaction of various system components and control power flow within the system to provide a

stable and reliable source of energy. With the wide spread introduction net-metering, the use of small

isolated or grid connected hybrid energy systems is expected to grow tremendously in the near future. A

number of hybrid energy systems in use/ under going testing in various parts of the world. Design of a

hybrid energy system is site specific and it depends upon the resources available and the load demand.

Solar energy and wind energy are two renewable energy sources that can be effectively combined to

produce electrical power by photovoltaics (PV) and wind turbines (WT) respectively. Hybrid PV/WT

systems of several sizes have been developed and interesting results have been extracted from installations

of these compound systems. Considering the application of PV and WT systems on buildings, the use of

small size wind turbines is necessary. These WTs can be of horizontal or vertical axis, must be of low cut -

in wind speed and also aesthetically compatible with the building architecture. PV panels are more flexible

than WTs regarding size and installation requirements and have been already applied successfully in several

buildings.

In this paper we present the concept of the hybrid PVT / WT systems, which combine photovoltaic,

thermal and wind turbine subsystems, aiming to cover effectively electrical and thermal needs of buildings.

The output from the solar part depends on the incoming solar radiation and is obtained during sunshine. On

the other hand the output of the wind turbine part depends on the wind speed at the location of the

installation and is obtained any time of the day or night that the wind speed is over a lower limit. Therefore

the PVT and WT subsystems can supplement each other, being primarily used to cover building electrical

load and secondary to increase the temperature of the existing thermal storage tank of PVT system by their

surplus electrical energy.

II.DESIGN APPROACHES

Various models based on different approaches have been designed to get the optimum configuration.

These can be classified as follows:

Logistical

Dynamic

A) Logistical Approach:

Logistical models are used primarily for long term performance predictions, component sizing and for

providing input to economic analyses. Generally they can be divided in following three categories:

Time series (or quasi –steady state)

Probabilistic:

Time series + probabilistic:

As the name suggests models in this category are based on the use of a combined time series and statistical

approach.

B) Dynamic Approach :

Dynamic models are used primarily for component design, assessment of system stability and

determination of power quality. They are generally used for hybrid power systems with no storage

capability, or systems with minimal storage such as flywheel. Depending on time step size and number of

modeled components they can be divided into following three categories:

Dynamic Mechanical:

Dynamic Mechanical, steady state electrical model:

Dynamic mechanical and electrical model:

A combined approach of time series probabilistic + dynamic mechanical and electrical model gives the best

performance of a wind solar hybrid system.

III.WORKING OF WIND-SOLAR HYBRID SYSTEM

Fig. No.1. Schematic of Wind- Solar Hybrid System

During daytime, solar photovoltaic array converts sunlight into electricity and stores this DC power

in battery bank.

Wind generator starts generating power when wind speed exceeds the cut-in speed of the wind

turbine. The wind turbine is of self regulated type with protection for over speed.

The hybrid controller has inbuilt solar charge controller and wind charge regulator. It maximizes

charging current and prevents excess discharge/overcharge of the batteries.

Inverter converts DC power into AC power to operate all standard electrical appliances. Inverter has

inbuilt protection for short circuit and overload. During windy period, excess energy generated by

wind battery charger is dissipated through a dump load.

Usually, a DC/AC inverter needs to be installed additionally. 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 favorable 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. In some regions the exploitation of both wind and solar resources can

become favorable, 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.

Main applications for rural electrification in developing countries include independent electric power

supply for Villages, Farmhouses, Residential Buildings, Missions, Hotels, Radio Relay Transmitters,

Irrigation systems, Desalination Systems.

IV. METHODOLOGY

In order to address the shortcomings of existing instructional techniques for electrical power systems,

a hybrid wind-turbine and solar cell system has been implemented. The system was designed and

implemented with the following goals:

• To be completely different from traditional electricity labs and to be fresh and interesting.

• To be intimately related to real-world industrial power issues such as power quality.

• To show a complex, interrelated system that is closer to the “real world” than the usual simple systems

covered in educational labs.

• To motivate learning by introducing such elements as environmental and economic concerns of practical

interest to the students.

V. ESTABLISHMENT OF A SOLAR WIND HYBRID UNIT

The hybrid unit contains two complete generating plants, a PV solar-cell plant and a wind-turbine

system. These sources are connected in parallel to a 12V DC line. The power is next connected to a DC to

AC inverter and is then supplied from the inverter’s output to a single-phase 60 HZ, 120 VAC load. The

overall project structure is presented in Figure 1. The wind turbine is installed at the top of a steel tower that

has a height of 18.3 meters and a diameter of 8.9 cm. The wind turbine depicted is a 0.7 kW unit and the

solar panels depicted number four in all with a capacity of 50 Watts each. The instrumentation panel

depicted monitors the outputs of the generator using digital panel meters. A small wind turbine was chosen

for its low maintenance and many safety features. One of the low maintenance features is the turbine’s

brushless alternator and an internal governor. The turbine generates 0.4 kW when turning at its rated speed

of 47 km/hr and it is capable of generating up to 0.7 kW at its peak wind speed of 72 km/hr. The actual

system’s pictures are shown in Figure 2.

Fig. No.2. Actual Picture of Wind/PV Hybrid Power Station

The turbine’s blades are made of a carbon fiber reinforced composite that will intentionally deform

as the turbine reaches its rated output. This deformation effect changes the shape of the blade, causing it to

go into a stall mode, thus limiting the rotation speed of the alternator and preventing damage in high winds.

Another feature of the wind turbine is a sophisticated internal regulator that periodically checks the line

voltage and corrects for low voltage conditions. The solar panels are 12 VDC units and were chosen for their

ultra clear tempered glass that is manufactured for long term durability. Figure 3 shows the DC voltage

measured across the 12 volt DC bus where the wind turbine and PV arrays outputs are connected. A slight

ripple in power regulation can clearly be seen. This ripple is a function of the unpredictable nature of wind

and sunshine along with the dynamic effects of the electrical load. As mentioned earlier, one of the largest

problems in systems containing power inverters is power quality. This problem becomes serious if the

inverter used in the system does not have a good sinusoidal waveform output and causes problems such as

harmonic contamination and poor voltage regulation. According to the IEEE (a professional society which

codifies such issues) standards, a maximum of 3 to 4% total harmonic distortion (this is a quantitative

measure of how bad the harmonic contamination is) may be allowed from inverter outputs. However, many

inverter outputs have much more harmonic distortion than is allowed. The inverter used in this system has a

power rating of a 1.5 KVA and was manufactured by Trace Technologies ®. The battery banks contain 4

deep-cycle lead-acid batteries connected in parallel. High power capacity heating resistors, energy efficient

light bulbs, incandescent light bulbs, and two small AC motors constitute electrical loads that can be applied

to the system. To monitor and store the voltage, current, power, and harmonic contamination data, two Fluke

® power quality analyzers (types 39 and 41) are used in the system. In addition, permanently mounted

AC/DC digital panel meters form part of the system’s instrumentation.

Fig. No. 3. Established Wind/PV Hybrid Power Generation Unit

VI. EXISTENCE OF SOLAR WIND HYBRID SYSTEM

A) Solar Energy:

Advantages

1. The main advantage of solar energy is that this energy is free and available in plenty.

2. The equipments used for solar energy are simple in construction, also they require minimum

maintenance.

3. It is pollution free.

4. The solar thermal power plants are feasible in deserts, dry sunny areas where other sources

of energy is not available.

5. Solar p v systems are economical and feasible for remote, stand alone power plants

Disadvantages

1. Solar energy is not in the concentrated form.

2. The capital investment for equipment is more than conventional ones.

3. Efficiency of the plant is less.

4. Low energy density, 0.1 to 1 kW / sq. m

5. Large area covered by solar collectors.

6. Direction of rays changes continuously, also varies during the day, season and with

weather conditions.

7. Energy is not available at night and during cloudy periods.

B) Wind Energy:

Advantages

1. Wind energy is readily available, nonpolluting power system so it has no adverse influence on

environment.

2. Wind energy systems avoid fuel provision and transport.

3. On a small scale, up to a few KW system is less costly. On a large scale costs can be competitive with

conventional electricity and lower costs could be achieved by mass production.

4. It has low operating cost and also can be useful in supplying electric power to remote areas where other

energy sources are scarcely available.

Disadvantages

1. Wind energy available is dilute and fluctuating in nature.

2. Unlike water energy, wind energy needs storage capacity because of its irregularity.

3. Wind energy systems are noisy in operation, a large unit can be heard many kms away.

4. Due to the involvement of the construction of high towers with gear box, generator, couplings, etc., the

wind power system has a relatively high overall weight.

5. Large areas are needed, typically, propellers one to three meters in diameters.

6. Present systems are neither maintenance free nor practically reliable

7. Wind power plants can be located only in the vast open areas in locations of favorable wind.Such

locations are generally away from load canters.

8. Presently, it is only in one to a few MW range, does not meet the energy needs of large cities and

industries.

C) Existence of Solar Wind Hybrid Power Plants:

As seen above, there are problems in utilizing the solar as well as wind energy efficiently. In order to

overcome these problems, concept of ‘hybrid power plant’ is introduced. In this both solar and wind power

plants are used so that their disadvantages are reduced to a considerable amount.

As we know that sun is available in the day only, energy is not available during night from sun

whereas wind energy is available throughout the day and its capacity increases in the nights. Here when sun

is not available wind energy comes to play and vice-versa. Thus hybrid power plants are more useful than

individual ones and therefore they are extensively used nowadays.

VII. OVERALL VIEW OF THE PLANT10 KWp Wind-Solar Hybrid System at St. Martins Island( Bay of Bengal), Cox's Bazar

St. Martin’s Island - a remote coral offshore Island in the Bay of Bengal. This island is famous for

marine and coastal bio-diversity and eco tourism.  Ministry of Environment & Forest  already taken up

program for Conservation of Biodiversity, Marine Park Establishment & Eco-tourism Development  in St.

Martins Island. Sustainable Rural Energy under Local Government Engineering Department (LGED)

with the finance from UNDP installed 10Kw Solar-Wind Hybrid System  in St. Martins Island at Bay of

Bengal, which is largest in Bangladesh. The hybrid system producing power combined  with solar and

wind  resources to a centralized  AC output system. The entire power supplying to Motel, Barrack, Central

Plaza, Laboratory & Dormitory.

Centralized Wind-Solar Hybrid System Solar Array of Centralized Wind-Solar Hybrid System  at St. Martins Island of Bay of Bengal

IX.CONCLUSION

Obviously, a complete hybrid power system of this nature may be expensive and too labor intensive

for many Industrial Technology Departments. However, many of the same benefits could be gleaned from

having some subset of the system, for example a PV panel, batteries, and an inverter, or even just a PV panel

and a DC motor. The enhancements to instruction, especially in making electrical power measurements

more physical, intuitive, and real-world are substantial and the costs and labor involved in some adaptation

of the ideas in this paper to a smaller scale setup are reasonable. The use of solar and wind hybrid power

generation is an especially vivid and relevant choice for students of Industrial Technology as these are

power sources of technological, political, and economic importance in their state. The key elements of this

test bed concept presented in this paper are two or more renewable power sources connected to a power grid

with complex electrical interactions.

In coming years, man will have to increasingly depend on renewable energy sources. Because of the

disadvantages involved in using solar or wind energy individually, a hybrid system which avoids the

individual advantages will become more famous in coming years. Also the renewable energy equipments

will become cheaper and efficient with modern technology.

REFERENCES

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