The document discusses a hybrid controller for renewable energy power plants in stand-alone sites. It describes a prototype hybrid solar PV-fuel cell-battery-diesel generator system of up to 5 kW that was developed. Experimental testing showed the controller effectively switches between the different power sources based on availability and load demand. A cost-benefit analysis found the hybrid system has a payback period of 5-10 years compared to a traditional diesel-battery system due to lower operating costs and carbon tax savings over the 30-year lifetime. The technology has commercial potential for powering telecom towers, hospitals and other remote facilities independently of the grid or continuous renewable energy availability.

1. 1
Hybrid Controller for
Renewable Energy Power Plant
in Stand-alone sites
Dr. Prabodh Bajpai
Assistant Professor
Electrical Engineering Department, IIT Kharagpur
1

2. Outline
 Introduction
 Technology aspects
 Benefit to the Industry
 Commercialization prospective
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites
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3. Introduction
 Uncontrolled Renewable energy sources essentially
have random behaviors. eg: Solar, Wind, etc.
 Power production from Uncontrolled sources is
independent of human intervention
 Hybrid power systems may contain controlled and
uncontrolled energy sources and energy storage
elements with appropriate control systems
 Stand-alone hybrid power systems take advantage of
the complementary nature in profile of the renewable
energy sources
 Hybrid power systems ensure continuous and reliable
power production
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites
3

4. Possible Renewable Hybrid Energy
Systems
1) Wind/PV/FC/electrolyzer/
battery system
2) Micro-turbine/FC system
3) Microturbine/wind system
4) Gas-turbine/FC
system
5) Diesel/FC system
6) PV/battery
7) PV/FC/electrolyzer
8) PV/FC/electrolyzer/battery
system
9) FC/battery, or super-
capacitor system
10) Wind/FC system
11) Wind/diesel system
12) Wind/PV/battery
system
13) PV/diesel system
14) Diesel/wind/PV system
15) PV/FC/ SMES system
4
Wind and solar power generation are two of the most
promising renewable power generation technologies.
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Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites

5. DG/Battery Hybrid Solution: Merits
 Easy to install and low cost on site construction
 Highly integrated intelligent hybrid power system
for control and protection
 Inclusion of battery back up reduces the DG size
Saving in diesel and reduction in maintenance of diesel
generator
Reduced operating time and enhanced DG life
 Specially designed deep cycle battery available in
market
Rechargeable in a short time,
Long cycle life under STC,
High DoD (Depth of Discharge)
5
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Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites

6. DG based Hybrid Solution : Demerits
 DG as energy source has problems of :
 Pollution
 air, noise, heat
 Dependence of fuel
 world-wide increase of oil prices; limited resources in future
 Transport to the sites
 long distances and cost intensive transports
 Storage of the fuel at site
 safety problems - explosions, vandalism
 No unattended operation is possible
 high personnel cost
 High maintenance cost and limited life-time of DG
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites 6

7. Hybrid Renewable Energy Systems
 On the other hand, the proposed renewable energy
based system helps in:
 Decrease environmental pollution
Reduction of air emission
 Energy saving
Reduces production and purchase of fossil fuels
 Abatement of global warming
CO2 and other green house gases are not produced
 Socioeconomic development
Develops employment opportunities in rural areas
 Fuel supply diversity
Diversity of energy carriers and suppliers
 Distributed power generation
Reduces requirement for transmission lines within the electricity grid
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites 7

8. Challenges
 Site dependence of renewable sources
Site survey with long term data acquisition & forecasting
 Hybrid renewable energy system design
Configuration and sizing of the hybrid system
components with the objectives:
Supplying the power reliably under varying atmospheric
conditions
Minimizing the total cost of the system
Maximizing the system efficiency by efficient energy flow
management strategies
Optimization through simulation studies under real
operating conditions for a reasonable tradeoff among
conflicting design objectives
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Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites

9. Challenges
 Economic viability
Cost-benefit analysis of hybrid system for
reasonable payback period
 Real world application
 Design of power conditioning devices with
maximum power point operation of energy sources
 Optimal energy management strategies and their
testing with laboratory prototype hybrid controller
 Development of hardware and associated software
for field-implementation
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites
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9

10. Technology aspects
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites
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11. Introduction
 Solar PV based renewable power plant with FC,
Battery and DG as backup sources
 Hybrid controller to implement the energy
sources changeover logic based on optimal
energy management strategy.
 Automatic mode of operation in the hybrid
controller for FC and DG changeover operations.
 Laboratory prototype of hybrid Solar PV-Fuel
Cell-Battery-DG system for upto 5 kW load
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites
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12. A typical stand-alone PV-Fuel cell-
Battery hybrid energy system:
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Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites

13. System Development
 Robustness of the controller to fluctuating weather
conditions and load demand is being rigorously
tested, monitored and documented.
 Hybrid controller comprises of:
◦ Solar DSCAM (master controller) and two slave controllers,
the Fuel Cell DSCAM and DG DSCAM
◦ Individual power conditioning units for SPV, Fuel Cell and
DG system to provide regulated DC output on the DC bus.
• The master and slave controllers interact to
provide switching and control signals for the
converter units.
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites
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14. SPV-FC-BATTERY-DG HYBRID ENERGY POWER PLANT
Discharging
Charging
Supply to
Load
PV Power
FC Power
DG Power
SOLAR PV ARRAY (Primary Source)
BATTERY BANK ( Back Up Source)
FUEL CELL SYSTEM (Back Up Source)
CONTROLLER
DIESEL GENERATOR (Back
Up Source)
LOAD
H2 storage
H2
Supply

15. Experimental Test Results
0
10
20
30
40
50
60
Voltage
(V)
Time of the day (hr)
SPV Module-1
Voltage (V)
FC Module-1
Voltage (V)
DG Module-1
Voltage (V)
System Voltage
(V)
Battery-3 Voltage
(V)
Load Voltage (V)
FC
Operation
Battery
Operation
DG
Operation
Battery
Operation
SPV
Operation
SPV
Operation
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites
15
Load 0.75
kW
Load 1 kW

16. -40
-30
-20
-10
0
10
20
30
40
50
60
Current
(A)
Time of the day (hr)
SPV Input Current (A)
SPV Module-1 Current (A)
FC Input Current (A)
FC Module-1 Current (A)
FC Module-2 Current (A)
DG Module-1 Current (A)
DG Module-2 Current (A)
System Current (A)
Battery Current (A)
Load Current (A)
SPV Operation
Battery
Operation
FC
Operation
DG
Operation
SPV
Operation
Battery
Operation
Experimental Test Results
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites
16
Load 0.75 kW Load 1 kW
Excess Current
Battery Charging
Battery Charging

17. Merits of Topology
 Merits of solar PV charge controller and
Fuel Cell charge controller
◦ Optimal charging of the batteries and maximum power
extraction from solar PV and FC
◦ Supervisory functions to prevent damage to the battery
◦ Effective interface to inter connect Solar PV modules, Fuel
Cell, Battery Bank and the load
◦ Battery reaches a high state of charge under all operating
conditions
◦ Work in tandem with the SMPS based power plant to
optimize the charging capability of the FC/SPV and
protect the batteries from overcharge
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites
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18. Important Features of Topology
◦ Use of solid-state devices to control the charging current to
the battery and supply power to the load simultaneously
◦ Blocking devices to prevent reverse current flow from the
battery to the FC/SPV during cloudy days or other charging
modes
◦ Lightning / transient protection to protect the control circuitry
from damage due to excessive voltage
◦ Programmable charging capacity, change over settings and
peak power point
◦ Programmable maximum power point tracking (MPPT) logic
with the built in embedded logic controller
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites
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19. Solar resource assessment (SRA) system
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites
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•Measures weather parameters like
• solar insolation (W/m2),
• ambient temperature (0C) and
• relative humidity(%)
•Weather data at defined intervals
is measured using sensors
•Data is sent continuously to a
central server through GPRS and is
monitored online
Necessity of weather
monitoring
•Inspecting the feasibility of a site for
a solar energy project
•Site comparison and selection based
on weather data
•Long term energy assessment helps
in effective system sizing and cost
minimization
•Helps to predict the performance of
SPV

20. Remote Monitoring System
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites 20
Sensors
Hybrid Controller
cRIO-9073, Data acquiring,
Generating and logging
Monitoring Station
Remote PC

21. Benefit to Industry
Hybrid Controller for Renewable
Energy Power Plant in Stand-
alone sites 21

22. Market potential
 Extendable to a generalized solution for any kind of
stand-alone site.
 Independent of continuous availability of the
renewable source as well as grid power availability.
 Power converters are modular in nature
 For any kind of critical load in stand-alone site
◦ Telecom towers,
◦ Cold storage plants,
◦ Hospitals,
◦ Military establishments
◦ Fuel stations
◦ ATMs
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites 22

23. Commercialization prospective
Hybrid Controller for Renewable
Energy Power Plant in Stand-
alone sites 23

24. Cost-benefit analysis
 Net present value = Total lifetime savings –
Total lifetime investment
 Savings include revenue generated from the
hybrid PV system by replacing the DG-battery
system, the carbon tax benefit and savings in
the operational cost of the system.
 Investment includes the extra first cost which is
the difference between the Capex of the hybrid
PV system and the Capex of the DG-Battery
system
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites 24

25. Cost-benefit analysis
 CAPEX for hybrid PV system to meet 4kW
peak load will around 50Lakh INR
 The lifetime of both the systems considered
to be 30 years.
 Economic analysis for different scenarios
gives payback period between 5-10 years
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites 25

26. Real world application
 Proof of concept verified with a laboratory
prototype
 Field site testing with stand-alone load
application needs to be done
 The Technology Transfer may take place as per
One Time License Payment or Revenue Sharing
Model or any other criteria mutually agreed
Hybrid Controller for Renewable Energy Power Plant in Stand-alone sites 26

27. Hybrid Controller for Renewable
Energy Power Plant in Stand-
alone sites 27

28. Component size and price
Component Pricing
PV (per Wp) 70
Battery (per kwh) 7,000
H2 tanks(per m3) 400
Fuel cell(per kW) 2,00,000
Diesel Generator (per
kW)
33,000
Diesel (per litre) 40
Component Size
PV (Wp) 16500
Battery in hybrid PV system(kwh) 57.6
DG in hybrid PV system (kW) 5
H2 tanks (m3) 120
Fuel cell (kW) 4.56
DG in DG-Battery system (kW) 25
Battery in DG-Battery system(
kWh)
105

29. Financial Assumptions
 Hybrid PV system:
• CAPEX is the total initial cost of the system.
 OPEX in case1 =1% of CAPEX+ 100% of Battery cost in every 5
years+100% of FC cost every 10,000 hours of operation+
operating cost of FC @Rs 417/hr +operating cost of DG @Rs
50/hr.
 OPEX in case2 =1% of CAPEX+ 100% of Battery cost in every 5
years+100% of DG cost in every 15 years + operating cost of FC
@Rs 417/hr+ operating cost of DG @Rs 50/hr.
 DG/Battery system:
• CAPEX is the total initial cost of the system.
 OPEX =2% of CAPEX+100% of Battery cost in every 5
years+100% of DG cost in every 8 years + operating cost of DG
@Rs 50/hr.
 The lifetime of both the systems was considered to be 30 years.
 The present diesel cost was assumed to be Rs 40/litre.
 The annual escalation in diesel cost was assumed to be @ 10 %

30. Capex and Opex comparisons
3,060,
000
8,973,
982
Longer DG operation
Capex
Opex
3,683,2
00
23,600,
932
Longer FC operation
Capex
Opex
1,810,0
00
26,436,
200
DG-Battery
Capex
Opex
Hybrid PV/FC/DG/Battery
system
DG/Battery system

31. Comparison of savings & investments for
hybrid PV/FC/DG/Battery system
25,217,
247
27,284,
132
Longer FC operation
Savings
Investmen
ts 37,400,
995
12,657,
182
Longer DG operation
Savings
Investmen
ts

32. NPV and Payback Period
Longer FC operation Longer DG
operation
With carbon
tax benefit 23,344,047 35,527,795
Net present
value
Without
carbon tax
benefit
16,463,765 29,068,754
With carbon
tax benefit
5 4
Payback period
Without
carbon tax
benefit
7 6