1. MAGEEP 2016 – Research Paper
Introduction
The potential for biomass boilers in India is vast with over 350 million tons of biomass
being produced every year. Biomass is available from agricultural wastes, direct
harvesting and as a by-product from industries such as rice mills, sugar mills and saw
mills. However, due to problems with infrastructure and the seasonal variability of
biomass in India, consumers are struggling to obtain a consistent fuel supply. Seasonal
variation in the availability of biomass is one of the barriers faced by biomass power
generation projects.
On the other hand non uniformity and high initial investment are the problems
associated in solar energy technologies. A feed control in biomass fuel with variable
solar radiation avoids the need of solar energy storage and saves the storage cost.
This paper primarily focus on the suitable biomass hybrid models with solar thermal in
order to explore the possibility of optimizing fuel usage and making plants more
efficient and sustainable.
Biomass solar hybrid model may provide the solution to overcome these barriers as two
renewable energy resources complementing each other with regard to availability,
thereby enhancing the chance of improved PLF and so viability.
Solar & Biomass Technology
Solar energy can be considered as uncontrolled source because their availability is
totally dependent on the climate condition. Controlled sources are the sources, whose
power production can be controlled like Biomass, biogas etc. Combination of both is
perfect for electrification with improved thermal efficiency and plant availability.
Different technologies have been developed to concentrate the solar radiation,
depending on the required fluid temperature, plant size and capacity. The most widely
used are power towers and parabolic troughs. A major drawback in Solar plants relates
to the intermittence of its power generation, due to the day/night cycles and also the
periods of reduced irradiation (winter, cloudy periods). To overcome this problem,
research is being conducted to develop efficient heat storage systems and other energy
storage alternatives (e.g. Pumped hydroelectricity, chemical storage etc). However,
these technologies have been very expensive and beyond that, not sufficiently proven.
In contrast, biomass combustion is a mature technology with a large number of power
plants in operation worldwide. Biomass power plants have been designed to different
fuels (agriculture and industrial by-products), with various plant capacities.

2. Biomass - Solar Hybrid Technology
Hybridization of solar thermal with biomass combustion complements each other to
overcome their individual drawbacks and results continuous and uniform power supply.
The sun‫׳‬s rays can be harnessed by solar collectors and biomass feedstock can be burnt
as a supplementary fuel in the boilers to achieve constant base load operation. It is
operated on a simple regenerative steam Rankine cycle. The steam is generated from
two sources in day time. In night time, steam can be generated only from biomass
energy source without stopping.
Operational Detail (Fig1): Steam generated from solar thermal process will be collected
into a common steam header which will be further control through attemperator before
drum header. Steam generated from the boiler after combustion of biomass will be
collected into the same header from where it is taken into the turbine inlet through
super heater. Turbine shaft coupled with generator rotates to produces electricity as per
typical thermal power plant process.
Solar-Biomass Hybrid Steam Cycle
Turbine
Fig1
Solar Collectors
Boiler
Furnace
Super
heater
Biomass Feeding
SH Steam I/L
Steam Header
Condenser
Exhaust
Steam
CE Pump
Deaerator
HP
Heater
Drum
Makeup Water
G
Extraction to
HP Heater
Makeup
Water
BF Pump
Process Steam in
case of Co-Gen

3. Exhaust steam from the turbine enters into the condenser for condensation and after
condensation it further pumped into Deaerator through HP heater by Condensate
extraction pump (CEP). After mechanical deaeration of the condensate into deaerator,
Boiler Feed Pump (BFP) pumps the condensate back into boiler drum through
Economizer and solar collector feed control inlet to complete the entire Rankine cycle.
The design gives us a flexibility to produce steam from two sources during day time.
Any variation in solar radiation will be compensated by the steam produced from the
boiler. During day time the solar collectors helps in producing steam whose pressure
and temperature will controlled as per the turbine inlet parameters. This will also
improves the overall efficiency of boiler by reducing the specific fuel consumption
during low solar radiation by increasing the Drum inlet feed water temperature.
Hybridization can be designed / modified in various ways depending on the existing
plant thermal cycle and process steam requirement in case of Co-gen. The biomass
power plant is designed to operate from half load to full load condition. The condition of
equal sharing occurs in day time at maximum available solar radiation in solar noon
time. The full load condition for biomass plant will be reached in the night, sunrise and
sunset timings. Specific fuel consumption will vary depending on the solar irradiance
and present climatic condition. As the Boiler & Collectors efficiency varies with an
increase/decrease in working fluid temperature, the steam temperature at the inlet of
collector and steam header is to be controlled accordingly to avoid heat losses. The
solar energy share in plant increases the plant fuel efficiency but it drops the hybrid
plant thermal efficiency. It is because of low efficiency of solar collecting system
compared to combustion efficiency. Hence the boiler pressure is optimized at each solar
energy share. The steam generation rate is different with a change in solar contribution
in the hybrid plant.
A case study has been carried out at a 3.5 MW biomass power plant located at Andhra
Pradesh, India to validate the current thermodynamics works. In the plant, rice husk is
used as a fuel for power generation. The only difference here is, steam from the
collectors enters directly into the super heater tubes instead of going into boiler drum.
The steam generation rate is different with a change in solar contribution in the hybrid
plant. The hybrid plant thermal efficiency varies with changes in boiler pressure and
change in solar energy sharing during the day time.
Past Work Done
I am having almost 11 years of experience in thermal power plant upto 600 MW size. At
IL&FS, I am working with biomass and Co-gen projects since 2013. In past we have
taken several initiatives to improve the boiler efficiency among which feed water

4. temperature control is one of the major area which plays an important role in improving
the plant overall efficiency. I have also gone through various abstracts on solar energy
storage systems and its future. However researches are still on a very initial stage to
prove the reliability of all these storage system. Such Hybrid plants are one of the great
alternatives where drawbacks of both the technologies can be easily overcome and
existing markets of solar and biomass can be re-defined with new efficiencies and PLF.
Proposed Activities
1. To study the technical feasibility of this hybrid plant under various conditions
2. Understanding the economics of the entire model
3. To study Implementation techniques and processes involved
4. Analysis of efficiencies, overall improvement and impact on existing operations.
5. Study of other successful hybrid models around the world.
6. Study of latest developments in the biomass-solar hybrid systems
7. To understand the associated risk and to mitigate those challenges during design /
implementation to reduce cost and time.
Deliverables
IL&FS Renewable Energy Ltd has 2 Co-gen Power plants located in Kolhapur district and
one Biomass based plant in Aurangabad district of Maharashtra. All these plants are
based on the typical Rankine cycle and have sufficient space to undertake any one of
them as a pilot project. Based on the experience and understanding in Biomass & solar
plant, following will be my major deliverables:
1. To prepare a business model based on the technical understanding and
economics of hybrid model.
2. To implement a pilot project with minimum investment at one of our operational
biomass plant after feasibility and risk assessment.
3. To provides inputs for enhancing efficiencies and PLF in upcoming / existing
projects across group companies.
4. To explore new investors / companies with whom we can work on this area /
technology jointly and explore new opportunities
5. To demonstrate this technology benefits within group companies and SPV’s.
Deepak Prasad