Homer Report

8/13/2019 Homer Report

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1. Introduction:

Nowadays, the mankind is living an energy crisis. The most optimist forecasts reveal the fact

that the main classic energy resources (oil and natural gas) will be exhausted until 2050. Also,

the combustion causes the greenhouse effect which will determine an apocalyptical scenario in

the next (80-100) years. In this scenario, the only solution is finding and using new energy

resources, inexhaustible and clean, which will substitute in the next 50 years the current

resources based on fossil fuels.

The growing share of renewable energy production is predictable but depends both on

reducing the production costs and on finding new electrical energy storage solutions. This will

ensure the injection into the power system of large quantities of renewable energy. Even more,

the legislation regarding environment protection imposes the usage of this kind of energy. In

March 2007, a European agreement was signed, which impose the reduction of CO2emission

with 20% until 2020 and 50% until 2050, but also using the bio-fuels with a share of 10%.

2. Renewable energy used for residential consumers

Wind energy is used by the wind turbines, which nowadays have rated powers up to 3 MW. The

investments in this area are growing day by day, wind energy being used by consumers in rural

and extra-urban areas with important wind potential.

3. Description of HOMER softwarean optimal analysis tool

Homer (Hybrid Optimization Model for Electric Renewals) was developed by NREL (NationalRenewable Energy Laboratory, Colorado USA), as a work platform for optimal selection of

independent, interconnected or distributed power sources for consumers, connected or not

connected to the public grid.

The processed information by HOMER refers to:

power sources: photovoltaic panels, wind turbines, small hydropower plants, diesel

generators, biomass, biogas, fuel cells, public grid;

energy storage: hydrogen, batteries;consumers: daily and annual load curves, water

Pumping, heating, ventilation and air conditioning.


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Using HOMER involves the following steps:

- In the initial phase, all the technical possible combinations for supplying the consumers using

the specified power sources are determined. Next, the energy balance for 8760 h/year and all

the possible alternatives to provide the energy are determined;

- In the second phase, for every alternative a full economical estimation (considering all theexpensed regarding the initial investments, maintenance, repairing, modernization, interests

and benefits) is computed.

- The third phase optimizes economically the proposed solutions and presents them in

ascending order of costs per life cycle;

- In the fourth phase, sensitivity indexes of the results considering the variations of the input

data are computed.

Finally, from the presented results, the user can decide which the best solution to supply the

consumers is.

4. Case study using HOMER

For the case study, a medium size extra-urban residential area in Coimbatore, Peelamedu (11.0183

N, 76.9725 Coimbatore)is considered. Each house accommodates 3-4 persons and has an installed

electrical power of 5 kW. For all the considered area, the primary load is scaled to an annual

average of 1250kWh/d and a peak of 150kW and the deferrable load scaled to an annual

average of 2.83kWh/d and a peak of 100kW.

Load Consumption(kWh/yr) Fraction

AC primary load 450,080 74%

Deferrable load 1,035 0%

Electrolyzer load 159,604 26%

Total 610,719 100%

Fig 1.Load details for a day


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Fig 2.Seasonal profile of the primary

load.

Fig 3.Monthly profile of deferrable load.

5. Resources.

The HOMER software can generate the clearness index from the solar radiation

data according to the latitude of the place has been chosen. If the solar radiation

data is not available, clearness index can also be used to generate the solar

radiation data. Therefore, either the clearness index or the solar radiation data can

be used to represent the solar resource input, as long as the data of latitude is

available to the HOMER software.

Month Daily solar radiation (kWh/m2/day) Wind speed (m/s) at 10m

Jan 5.459 3.650

Feb 6.375 3.190

Mar 6.746 3.290

Apr 6.502 3.230

May 5.720 3.810

Jun 4.673 5.520

Jul 4.503 5.530

Aug 4.592 5.020

Sep 5.123 3.090

Oct 4.809 3.000

Nov 4.811 3.210

Dec 5.054 4.060


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Fig: solar resource of peelamedu.

Fig: wind resource of peelamedu.

6. System Components.

1.Photovoltaic Array In order to optimize the PV array ,PV of sizes

250kW,500kW and 750kW are considered

2.Wind turbines To optimize the wind requirements, NEPC wind turbines (6

numbers)are included in the power system

3.Fuel Cell Fuel cells with 50 kg capacity are considered to meet the

requirements. The fuel input to the system is liquid

hydrogen

4.Battery Batteries with string numbers 10,15,20,25 and each string

having 19 batteries are connected to supply the bus

requirement of 228v

5.Converter Converters with capacity 150 kW are used for dc/ac

conversions

6.Electrolyser The electrolyzer unit of sizes 100 and 150kW are included

to store the fuel and supply when needed

7.Hydrogen Tank A hydrogen tank with 50 kg capacity is used for the supply

needs

The above number of units and the system components are connected and simulated to obtain the best cost analysis

and power analysis.


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NEPC:

Since in India NEPC is one of the commonly used windmill generator we had simulated and modeled our power system

using NEPC. To add the windmill to the HOMER library we had referred the power curve of NEPC 250kW wind generator.

Fig: Power curve of NEPC at 10m.

The lifetime of the same windmill is about 25 years and it includes a capital cost of 20830$.From the power curve

initially we had included 4 quantity of NEPC. But when the HOMER simulated the system it suggested including more

number of Windmills. By this way we had arrived with different architecture each having different configurations.

PHOTOVOLTAIC ARRAY

We all know that a country like India is having enough solar radiation throughout the year. So we had considered

Photovoltaic array of different power capacities. But the cost of these PV array is very high .It poses constrain for us to

have only limited number of PVs.If we look at any system from the simulation results the cost of PV is 50% of the initial

cost if the system includes PV array. The Lifetime of PVs is also 25 years. The De-rating Factor, Slope, Azimuthal angle

differs from place to place and it is given as per the latitude and longitude.

Fig: Cost flow graph for a system with PV.

FUEL CELL:

Being a Hybrid Power System using only renewable resources instead of using fossil fuel generators we had considered

Fuel Cells. The source or the fuel for these Fuel Cells is from Hydrogen Tank which stores the required Hydrogen (fuel).

This Hydrogen is generated from the electrolyzer. So we had to go in for connecting Electrolyzer also as a part of system

component.


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CONVERTERS AND BATERRIES:

As in the system we considered DC components which serve the AC load converters

must also be considered. The value of the required converter and batteries varies

as per the total amount of AC/DC power generated. But those values can be easily

found as every time HOMER simulates it suggests the value of the eachcomponents that makes the system feasible.

ANALYSIS OF RESULTS:

Three power systems configurations using different energy storage technologies,

namely

PV/Wind/Battery system,

PV/Fuel cell/Battery system.

PV/Wind/Fuel cell/Battery system

All the above systems are simulated in HOMER environment for optimal sizing

which minimizes the system cost. The simulation results provide comparison

among these configurations. Simulation studies are classified as: Case A

(PV/Wind/Battery system), Case B (PV/Wind/Fuel cell/Battery system), Case C

(PV/Wind/Fuel cell/Battery system).

Case A (PV/Wind/Battery system)

System Architecture:

PV Array 500 kW

Wind turbine 6 NEPC

Battery 380 Vision 6FM200DInverter 150 kW

Rectifier 150 kW


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Electrical:

Cost summary

Total net present cost $ 2,344,849

Levelized cost of energy $ 0.405/kWh

Operating cost $ 70,003/yr

Case B (PV/Fuel cell/Battery system)

System architecture:

PV Array 750 kW

Fuel Cell 50 kW

Battery 475 Vision 6FM200D

Inverter 150 kWRectifier 150 kW

Electrolyzer 150 kW

Hydrogen Tank 50 kg

Dispatch strategy Cycle Charging

Component Production(kWh/yr) Fraction

PV array 1,268,987 91%

Fuel Cell 130,583 9%

Total 1,399,570 100%


PV array 845,992 42%Wind

turbines

1,178,469 58%

Total 2,024,461 100%


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Cost:




Case C (PV/Wind/Fuel cell/Battery system).

System architecture

PV Array 250 kW

Wind turbine 6 NEPC

Fuel Cell 50 kW

Battery 285 Vision 6FM200D

Inverter 150 kW

Rectifier 150 kW

Electrolyzer 100 kW

Hydrogen Tank 50 kg

Dispatch strategy Cycle Charging

Cost summary:

The operating cost here is the minimum of all the three configurations. So HOMER

shows this system architecture as the optimal system out of all possible

combinations.





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ELECTRICAL:

The total amount of load needed is shared by three sources and also compared to

the previous technologies 70% of load is met by Windmills and thus reducing the

initial capital cost actually incurred.


PV array 422,996 25%

Wind turbines 1,178,469 70%

Fuel Cell 81,156 5%

Total 1,682,621 100%

Component Wise Analysis of the Optimal System:

PV:

Quantity Value Units

Rated capacity 250 kW

Mean output 48.3 kWMean output 1,159 kWh/d

Capacity factor 19.3 %

Total production 422,996 kWh/yr


Minimum output 0.00 kW

Maximum output 295 kW

PV penetration 92.7 %

Hours of operation 4,413 hr/yr

Levelized cost 0.105 $/kWh


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AC Wind Turbine: NEPC

Variable Value Units

Total rated capacity 1,500 kW

Mean output 135 kW


Total production 1,178,469 kWh/yr


Minimum output 0.00 kW

Maximum output 1,449 kW

Wind penetration 258 %


Levelized cost 0.00881 $/kWh


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Fuel Cell



Number of starts 699 starts/yr

Operational life 18.6 Yr


Fixed generation cost 8.75 $/hr

Marginal generation cost 0.00 $/kWh/yr


Electrical production 81,156 kWh/yr

Mean electrical output 37.8 kW

Min. electrical output 0.00000000000000100 kW

Max. electrical output 50.0 kW


Hydrogen consumption 4,869 kg/yr

Specific fuel consumption 0.060 kg/kWh

Fuel energy input 162,313 kWh/yr

Mean electrical efficiency 50.0 %


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Battery

Quantity Value

String size 19

Strings in parallel 15

Batteries 285

Bus voltage (V) 228


Nominal capacity 684 kWh

Usable nominal capacity 410 kWh

Autonomy 7.86 Hr

Lifetime throughput 261,345 kWh

Battery wear cost 0.610 $/kWh

Average energy cost 0.000 $/kWh


Energy in 52,103 kWh/yr


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Energy out 41,689 kWh/yr

Storage depletion 7.88 kWh/yr

Losses 10,406 kWh/yr

Annual throughput 46,610 kWh/yr

Expected life 5.61 Yr

Converter

Quantity Inverter Rectifier Units

Capacity 150 150 kW

Mean output 24 10 kW

Minimum output 0 0 kW

Maximum output 150 150 kW

Capacity factor 15.9 7.0 %

Quantity Inverter Rectifier Units

Hours of operation 4,788 1,957 hrs/yr

Energy in 232,823 108,129 kWh/yr


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Energy out 209,541 91,910 kWh/yr

Losses 23,282 16,219 kWh/yr

HydrogenTank


Hydrogen production 4,909 kg/yr

Hydrogen consumption 4,869 kg/yr

Hydrogen tank autonomy 31.9 Hours


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Emissions

Pollutant Emissions (kg/yr)

Carbon dioxide -49.7

Carbon monoxide 31.7

Unburned hydocarbons 3.51

Particulate matter 2.39

Sulfur dioxide 0

Nitrogen oxides 282

Sensitivity Analysis

A challenge that often confronts the system designer is uncertainty in key

variables. Sensitivity analysis can help the designer to understand the effects of

uncertainty and make good design decisions despite the uncertainty. A sensitivity

analysis can be performed by entering multiple values for a particular input


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variable. HOMER repeats its optimization process for each value of that variable.

An input variable for which you have specified multiple values is called a sensitive

variable, and many sensitive variables can be defined. A sensitivity analysis can be

referred to as one-dimensional if there is a single sensitive variable. If there are

two sensitive variables, it is a two-dimensional sensitivity analysis, and so on.

HOMER's has the most powerful graphical capabilities which is developed to help

and examine the results of sensitivity analyses of two or more dimensions.

Since Avg.Wind Speed of Coimbatore is too low if the same system is to be

implemented in nearby area where there is large amount of wind available we had

included the Sensitivity analysis of Avg.Wind Speed Vs Global Solar Energy.

Challenges Faced:

When performing a sensitivity analysis on the load, many sizes of each equipment type must

be considered to meet the range of loads evaluated. To reduce the computation times HOMER

runs were performed in an iterative process. Initially, the optimization search space

considered only a few component sizes over a large range. Similarly, the sensitivity analyses

covered a large range with few points. This helped to decrease the initial run-time. With each

successive run, more options and variables were added to increase the resolution and fill in

the search and sensitivity spaces.

Obtaining data for analyses such as these is always challenging. This is especially

true for the wide variety of windmills that are commercially available. It is often

hard to know a priori which inputs deserve a lot of effort getting precise data.

Rough estimates of variables, such as O&M cost, lifetime, and part-load efficiency,

can be entered into the program. A HOMER sensitivity analysis on these variables

can then inform the user of the value of improving the accuracy of that input

variable.

Glossary:

1.Salvage present value or the recovery value: The net value of the equipmentused at the end of the system's service life. The salvage or the residual value


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of components is based on the possibilities of alternative uses at the end of

the project lifetime.

2.Feasible system: A system that satisfies the specified constraints.3.Levelized cost of energy: The average cost of producing one kilowatt-hour of

electricity, including capital, replacement, fuel, operating and maintenance

costs.

4.Maximum annual capacity shortage: The percentage of the yearly total loadthat is allowed to go unserved by the system.

5.Net present cost: The present value of the cost of installing and operating thesystem over the lifetime of the project (also referred to as lifecycle cost).

6.Optimal system type: The combination of power-generation technologieswith the lowest net present cost.

7.Renewable energy fraction: The portion of a systems total electricalproduction that originates from renewable power sources.

8.Search space: The set of all system configurations that HOMER evaluates.9.Sensitivity analysis: An investigation into the extent to which changes in

certain inputs affect a models outputs.

10.System type: A combination of power-generation technologies.

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