4. Plant Operation – Hybrid
Solar Thermal Biomass Plant
Superheated steam required to generate useful power
o Requires almost 80% of the energy from the boiler to reach saturated
vapor phase.
o Use solar energy for this purpose.
x 3306 kJ/kg
400
20%
300 1097 kJ/kg 60%
x x
2800 kJ/kg
200
20%
x 600 psia isobar
100
498 kJ/kg
4
5. Why Hybrid Solar + Biomass Plant
Solar & biomass are the only renewable resources that
make sense in most of the parts of India
Solar only approach can utilize either PV or solar
thermal
o Both suffer from low capacity factor in India due to tropical
conditions (high humidity and rain showers)
Biomass only approach works but supply can be an
issue, especially in drought conditions.
o Results in variable O&M costs
5
6. Major System Components
Parabolic trough concentrator
Biomass Gasifier
Boiler (producer gas burner)
Super heated steam turbine
6
7. Parabolic Trough Concentrator
Medium Temperature Parabolic Trough (MTPT)
High efficiency and durable mirror
film technology
Temperatures up to 300o C.
Less thermal losses.
Modular & scalable.
Space frame light weight technology
Ease in construction and tracking.
Fig: MTPT pilot plant at Florida
( Source: SET Florida)
7
8. MTPT - Technical Specifications
TECHNICAL DETAILS
Construction Materials Aluminum and Steel
Reflective Surface Reflective Film
Reflectivity 0.94
Absorber Material Steel
Selective Surface Cermet
Absorber Envelope Borosilicate Glass
Max Wind Speed tolerance 110 mph
Life Expectancy 20 years
TROUGH GEOMETRY
Module Aperture Width 2.74 m 9 ft
Module Aperture Length 12 m 39.4 ft
Module Aperture Area 32.9 sq. m 354 sq. ft
Focal Length 1.49 m 4.9 ft
Number of modules per Solar Collector Assembly (SCA) 8
Total SCA length 100 m 328 ft
Net Aperture Area 263 sq. m 2830 sq. ft
8
9. Gasifier
Gasification
o Thermo-chemical process converts biomass into a gas.
o The resulting gaseous compound is called Syngas
Syngas consists of hydrogen and carbon monoxide (and
lesser amounts of carbon dioxide and other trace gases)
under oxygen depleted, high pressure, high-heat and/or
steam conditions.
The gasifier is essentially a chemical reactor where various
complex physical and chemical processes take place.
9
10. Other System Components
Boiler
o Customized to provide superheated steam
o Designed to burn syngas from gasifier
o NOx emissions up to 30 ppm
o Temperatures up to 450 C are achievable
o Efficiency 88 to92%
Turbine
o Multistage impulse, extraction cum condensing
o Designed to produce 5 MW electricity
o Working at 450C and 40atm
10
11. Proposed Plant Details
SOLAR FIELD
Total number of modules 960
Arrangement 3 loops in series & 20 strings in parallel
Mass flow rate 5 kg/s
Working Fluid Therminol VP-1
Energy contribution from solar field annually at 1000W/m2 18%
TURBINE
Inlet temperature 450 C
Total thermal energy input for the steam turbine 16.67MW
Net electric output of the steam turbine 5MW
BIOMASS GASIFIER
Arrangement 3 numbers in parallel
Model Ankur Scientific gasifiers ( WBG-2200)
Rated gas flow 4,950 Nm3/hr
Average gas calorific value 1100 Kcal/Nm3
Rated thermal output 54,45,000 Kcal/hr
Maximum biomass consumption Maximum 1980 Kg/hr
Moisture content < 20% (Wet Basis)
11
12. Proposed Plant Operation
• When Solar Radiation is available
– Solar field heats the working fluid (Therminol) from an input temperature
of 1200C to 250oC at 40atm saturated vapour.
– The working fluid passes through the biomass boiler to reach the steam
turbine at input temperature of 4500C 40atm super heated.
– One gasifier only runs at 50-70% capacity and the others get turned off.
• When Solar Radiation is not available
– Therminol bypasses the solar field and is completely heated in the
boiler.
– All gasifiers run at full capacity to provide required thermal input of
16.67MW/H.
12
13. Expected Plant Performance
Expected energy output
o Solar - 67,01,400 kWh (18%)
o Biomass - 3,05,28,600 kWh (82%)
o Total - 3,72,30,000 kWh
Annual Energy contribution from solar - 18% @ DNI: 5.4
Daily Biomass consumption - 116 tonnes
Annual Biomass consumption - 36,000 tonnes
Total biomass savings (approx) - 7500 tonnes a year
• Assumptions:-
• Plant uptime : 85%
• Boiler efficiency : 90%
13
15. Important Assumptions
ASSUMPTIONS
Plant Capacity 5 MW
Plant Load Factor 85%
Energy Generation in Units 37.23 million units
Auxiliary Consumption 8%
Tariff INR 7.50
Biomass Consumption 36,000 tonnes per annum
Biomass Cost including transportation INR 2,500 per tonne
Total Project Cost including IDC INR 933.6 million
Debt Equity Ratio 70:30
Term Loan interest rate 13%
Working Capital interest rate 13%
Repayment of debt 1 year moratorium + 9 years
O&M cost INR 2 million / MW
Escalation of Biomass rate 5% per annum
Escalation of O&M cost 5% per annum
Power Tariff Increase 2% per year
15
16. Plant and Machinery Break Up
PLANT COST BREAK UP
LAND AND SITE DEVELOPMENT 49.50
PLANT AND MACHINERY 699.1
Boiler & Auxiliary 10.0
Turbine & Auxiliary 55.0
Solar Field 510.0
Gasifier 41.4
Civil Works For Boiler, Turbine & Other Equipment 30.0
Power Evacuation & Distribution System 20.0
Fuel Handling System 10.0
Others 22.7
EPC CHARGES 45.0
PREOPERATIVE EXPENSES INCLUDING IDC AND
CONTINGENCIES 117.22
TOTAL PLANT COST INCLUDING WC MARGIN 933.6
All figures in INR million
16
17. Important Ratios
IMPORTANT RATIOS
DSCR
- Average 1.50
- Minimum 1.01
- Maximum 21.39
IRR 14.67%
Equity IRR 17.43%
Payback Period 7th year from COD
LEVELIZED COST OF ELECTRICITY
Assumed Return on Equity 15%
Levelized Variable Cost INR 3.49
Levelized Fixed Cost INR 4.41
LEVELIZED COST OF ELECTRICITY INR 7.90 PER UNIT
17
19. Conclusions
• Proposed solar biomass hybrid solution -
– Reduces the usage of biomass.
– Increases the capacity utilization factor of the plant.
– Lowers the carbon footprint by not burning the
biomass.
– Suitable for distributed power generation in any
location.
– Efficient in solar thermal energy conversion.
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