1. International Journal of Advanced JOURNAL OF ADVANCED RESEARCH ISSN 0976 –
INTERNATIONAL Research in Engineering and Technology (IJARET), IN
6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 7, November – December (2013), © IAEME
ENGINEERING AND TECHNOLOGY (IJARET)
ISSN 0976 - 6480 (Print)
ISSN 0976 - 6499 (Online)
Volume 4, Issue 7, November - December 2013, pp. 101-108
© IAEME: www.iaeme.com/ijaret.asp
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IJARET
©IAEME
OFF-GRID HYBRID RENEWABLE ENERGY SYSTEM SIZING FOR HIGH
ALTITUDE COLD DESERTS
Neeraj Sharma,
Jimmy Kansal*,
Ashwagosha Ganju
Snow & Avalanche Study Establishment (sase), Chandigarh
ABSTRACT
Renewable energy has become an important area of Research and Development for both
environmental as well as economic reasons. This paper puts forward an approach to develop an
economically feasible, self sufficient, wind diesel hybrid energy system for anoff-grid field location
in Ladakh Cold deserts, Nubra Valley. The location under study is a remote place which has no
source of grid power. The electricity demand is met with diesel generators that consume 1.42 Lakh
Litres of fuel every year. Electricity generation by this method is very expensive due to ever
increasing cost of diesel and transportation of fuel. In this research we look into the available
renewable energy resources and conduct a pre-feasibility study of a hybrid power system at this
location.The design of the system is sought to use wind energy in addition to the existing diesel
generators to supply energy to the location. We present one-year power consumption data and wind
energy resource and explore the potential of tapping the renewable resource available to bring down
the diesel consumption at the site. From this data, the average daily, weekly and annual power
requirements for the location under study are determined. Since the heating loads contribute a major
part of the power requirements the monthly power requirements vary for the winter and summer
months. The sizing of the hybrid power system for the location is also presented.Hybrid energy
systems (using wind power only) were then researched and priced to determine feasibility in such
harsh off-grid locations. The final system model proposed was simulated in HOMER. Successes and
challenges of developing a completely self-sufficient, off-grid hybrid renewable energy system have
been discussed.The pre-feasibility indicates that the location has significant wind and solar energy
resource and using a wind-diesel hybrid system can reduce the diesel consumption by 23.5 % of its
present annual consumption.
Keywords: Renewable Energy, Fuel Costs, Weibull Distribution, Wind Power, Hybrid Energy
System.
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2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 7, November – December (2013), © IAEME
INTRODUCTION
The purpose of this project is to consider the feasibility of developing a hybrid renewable
energy system that is capable of providing enough electrical power to sustain a field location in
NubraValley. The site under study is SASE's field Observatory located in the Nubra Valley in the
Ladakh region near the Saichen Glacier area. The total strength of the location is about 20-25 people.
Access to the community is through air or by a metalled road only during the summer months. The
observatory generates its electricity using diesel generators operated and maintained by persons
staying in the location itself. It has three diesel generators with a total installedcapacity of 326kW
that consume more than 1.42 lakhliters of fuel every year and produceabout 3,89,000 kWh of
electricity. Electricity generation by this method is expensive due to ever-increasing cost of the fuel
and transportation to this remote location. Transportof fuel in winter is also a major issue and pre
stocking of fuel is required in the summer for running the gensets in winter season. The observatory
location has renewable energy resources like wind and solar energy. But renewable energy resource
assessmenthas not been done till date. Accurate renewable energy resource assessment involves onsite datacollection over a period of a year and primary site survey. In addition, the electrical load
dataalso need to be recorded for a period of one year. In this research we have recorded sitedata,
collected available information from all possible sources, visited the site and haveconducted a prefeasibility study of hybrid power generation at the site. The followingsections of this paper present
detail of our research.
EXISTING POWER SYSTEM OF THE FIELD OBSERVATORY
Presently the electricity is generated in the observatory using three diesel generators. The
higher rating generator is a 200kW capacity and the two lower rating generators are 66kW and
60kW. At one time typically only two generators of lower rating or one generator of higher rating are
running. One of the major loads on the diesel plant is the motors and blowers of the central heating
plant.Dieselgenerators require a major overhaul after 15000hrs of operation. Diesel generated
electricityis mainly used for heating, lighting, water pumping and communication in the location.
The electricity used for heating is for running of the heat plant motors and blowers. For the purpose
of analysis we have considered two loads for the location. Primary Loadcaters for entertainment,
lighting and communications demands of the location while the second load caters for the heating
motors, blowers, water heating and submersible pumps of the location. The second part of the load
varies for summer and winter months while the primary load is same for summer and winter months.
Figure 1 shows plant power productiondata. Daily profile indicates that load varies from 3.4kW to
109.35kW for summers and 41.65kW to 109.35kW for winter’s everyday.Monthly profile indicates
higher electrical load during winter months than summer months. Itis the heating plant and blowers
operate for more time in winters than in summer months. Load profile also indicates that for a few
hours in winters load may be as high as 140kW. Ever rising fuelcost is a major issue for such remote
locations. Community survival depends upon low cost energy.
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3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 7, November – December (2013), © IAEME
Fig 1(a) : Daily Load Profile for Winter Day & Monthly Load Profile
Fig 1(b) : Daily Load Profile for Summer Day
AVAILABLE RENEWABLE ENERGY RESOURCES
The field site under consideration has a met observatory in which the requisite parameters of
wind speed, wind direction and temperature are recorded on daily basis. A semi
automaticmeteorological instrument is also installed in the observatory which automatically records
these values from different sensors and logs it into the datalogger memory. Table 1 below presents a
summary of the collected data.
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4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 7, November – December (2013), © IAEME
Annual average wind speed at a height 10m = 10.12 m/s
Highest wind speed in July and lowest is in January
Maximum wind speed at a height of 10m= 13.22m/s
Diesel generators are 200kW, 66kW and 60kW
Annual average electrical load = 1000 kWhr/day
Peak load 164kW
Minimum load 3.4kW
Annual average load is 41.7kW
Diesel consumption in 2012 was 142560 litres
Plant generation efficiency 2.76 kWhr/litre
Total production in 2012 was 393361kWhr
Electrical load is highest from October to April and lowest May to Sep
Annual Average Solar Insolation = 4.15kWh/ m2/day
Diesel price in 2012 about $1.0 per litre
Table 1: Summary of Renewable Sources and Power Plant at Site
Collected data at the field site under observation isshown in Figure 2,3 and 4. One year wind
speed data is presented in figure 2. It shows windspeed is quite high at the field site under
observation. Annual average wind speed is only 10.12m/s at a height of 10m from the ground level.
Wind speedhistogram and best Weibull distribution fit is shown in figure 3. Wind resource is much
higherthan our initial expectation. Solar insolation data is presented in figure 4. Clearness index
ismoderate at the site. Average annual solar insolation is 4.15kWh/ m2/day.
Fig 2: Daily Wind Speed Data of the Field Location for the Year 2012
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5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 7, November – December (2013), © IAEME
Fig 3: Histogram for Wind Speed data
Fig4: Monthly Solar Insolation at Site
PROPOSED HYBRID POWER SYSTEM FOR CARTWRIGHT
The above section indicates that the useable renewable resources at SASE's field location are
wind and solar. Therefore, a hybrid energy system for the sitecould consist of wind turbine/s,
photovoltaics, batteries, power converter and diesel generators. A number of hybrid system sizing
examples may be found in the literature [1,2,3,4]. These examples provide very good guidelines for
the design of a hybrid power system. Each hybrid power system is unique and it should be designed
for the site based on the available resources and load profile. A proposed hybrid energy system for
SASE's field location is shown in figure 5. Sizing of a hybrid system can be done using Homer [5].
Other options are Hybrid2 and Retscreen [6,7]. We assumed that the load would remain the same in
the near future. Different types of wind turbines were selected with batteries, diesel generators and
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6. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 7, November – December (2013), © IAEME
converter were tried in Homer. In general wind turbine price per kW reduces with the wind turbines
size. But there are installation issues of large wind turbine in remote locations. There would be no
big cranes available in such remote area and bringing in a larger crane during the installation of wind
turbines will cost a fortune. Therefore, we decided to include only up to 10 kW wind turbine during
homer optimization.
Fig5: Proposed Hybrid Energy System for SASE's Observatory
Other inputs to the homer were already existing diesel generators, PV panels, batteries, and
converter. We assumed that there will one 220V AC bus and one 12V DC bus as shown in Figure 5.
Two 6V batteries will form one string. Prices of all parts of the proposed hybrid power system were
obtained from manufacturers websites. The operating reserve of batteries was assumed to be 10% of
the hourly load. Batteries will be recharged in cyclic mode and diesel generators will run as needed.
Each homer simulation took about 1.5 hours to complete. Basically, homer calculated available
energy and equated that to the load and selected a system configuration that can meet the site
requirements. With a condition of a minimum 20% renewable fraction and diesel price of $1.0 per
liter (2013price) homer suggested that we will need 10, Generic 10kW wind turbines. Figure 6 shows
homer optimization results. Homer optimization results indicate that the hybrid systemcapable of
producing lowest cost electricity should consist of 10, Generic 10kW wind turbines, oneof the
existing 82.5KVA generator (250KVA and 75KVA generator will not be needed), 120 Trojan LP16
batteries,37.5kW rectifier and a50kW bidirectional converter to link ac and dc bus. Initial cost of
such a system would beabout $89,000 including the generator cost and it will produce electricity at a
cost of $0.16 per kWh. Such a systemwould result in a renewable energy fraction of 24% using only
about 38,498liters of diesel. More homer optimization results are shown in figure 6. The expected
electrical performance of the best system is shown in figure 7. In such ahybrid system the wind
turbine energy contribution would be 27%, one 82.5KVA diesel generator willsupply 73%. The
existing250KVA generator and existing 75KVA generators will not be required. Excess
electricitywould be about 3.79%, whichcan be supplied for heating the places close to the
existingdiesel plant. The cost of the energy would be $0.16 per kWh, which is lower than thepresent
cost. Expected monthly electrical performance of the designed hybrid power system is also shown in
figure 7. It shows that most of the electricity in winter months would comefrom wind turbines.
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7. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 7, November – December (2013), © IAEME
Fig 6: Homer Optimisation Results
Fig 7: Expected Electrical Performance of Proposed Hybrid Power System
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8. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 7, November – December (2013), © IAEME
CONCLUSION
The renewable wind energy resource at SASE's field Observatory is of prime importance
since the wind energy can contribute significantly during the winter months. The wind energy and
diesel power generation are estimated for a possible hybridpower generation. Diesel plant load data
and renewable resources data of site wascollected during a site visit in 2013. Statistical analysis of
the collected data was done and theone-year site renewable energy resource data and load data is
presented in this paper. Thepublic domain software Homer was used to size a hybrid power system
for SASE's field observatory. Hybridpower system sizing is done assuming no energy conservation
efforts and no future increasein the electrical load. This research indicates that the available wind
energyresource is high and wind energy can be exploited for providing cheaper and emission free
power for the location. A hybrid systemconsisting of ten 10kW wind turbines, one existing 82.5KVA
diesel generator, 120 lead acidbatteries, a 50 kW converter, 37.5kW rectifier and a new plant control
system is proposed. This studyindicates that the proposed hybrid power system will reduce diesel
consumption to about 76.5% of the present consumption. Cost of electricity generation fromsuch a
system will be about $0.16 per kWh, which is less than the present cost of electricitygeneration i.e.
$0.249 per kWh in the observatory.
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