Biofuel vs PV literature review: Difference between revisions

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Net energy from cellulose ethanol from switchgrass

• Evaluation of switchgrass as a biofuel.

• Concerns –

1)energy efficiency and economic feasibility
2)Investigated agricultural input cost
3)biomass yield
4)estimated ethanol output
5)greenhouse gas emission
6)net energy results

• Findings

1)Switchgrass produces 540% more renewable energy than nonrenewable energy consumed.
2)94% lower greenhouse emission than gasoline.

• They considered fields on 10 farms for net energy economic evaluation so that they can eradicated the discrepancies that occur when small with similar agricultural inputs are under consideration.

• Study considers various agronomic practices

• States that biofuel from switchgrass produces 13.1MJ of energy for every MJ of petroleum input.

TAKE AWAYS

1)This paper will not only build the case for switchgrass to be used as a biofuel but will also help us what kind of location and what suitable agronomic practices must be followed to get the maximum yield. 
2)Location of the farm was found out to be one of the deciding factor for the amount of ethanol yield ye can extract.

Energy cost of rapeseed based biodiesel as alternative energy in china

• Evaluating energy cost of rapeseed as biofuel.

• Cost can be divided into 4 categories

1)Crop production
2)Transportation
3)Industrial conversion
4)Wastewater management.

• This paper stated that 1ha of land produces 1.5 ton of biofuel. This comes to around 20 GJ of energy left after taking into factor the energy used in the production.

• It focuses on an in-depth analysis of rapeseed as a biofuel.

• It gives insights on how biofuel is processed from the crop harvest.

• Detailed classification of energy cost of each and every element that goes into making the final usable biofuel.

• Findings

1)Agricultural produce contributes to the lion share of total energy cost.
2)Rapeseed biofuel has a negative energy return owing to the low production of crop.

TAKE AWAYS

1)Considering the areas where the average yield of crop is more.
2)Less nitrogen based fertilizers as they account for the highest share of cost for the agricultural production.
3)We should consider locations where the crop is abundantly available or there is some scope for increasing production and the energy input for agricultural produce is minimum.

Energy balances for biogas and solid biofuel production from industrial hemp

• Paper states that hemp has higher energy yield than any other crop to obtain biofuel.

• It is less susceptible to pest infection which in turn reduces the overall input cost.

• 4 cases were considered

1)Combined heat and power from spring harvested baled hemp: Combustion heat is used for generating electricity and residential heating.
2)Heat from spring harvested briquetted hemp: Combustion heat is used for small scale residential heating.
3)CHP

Vehicle fuel autumn harvested chopped and ensiled hemp: Depicts biofuel used in vehicles. • The first case was found out to be most efficient. • The study found out that the maximum chunk of input energy that goes into producing the final hemp biofuel is for processing the biofuel. • Advantages are less pesticide requirement, weed resistant, crop rotation is possible.

TAKE AWAYS

1)Areas where probability of pest infection is more, hemp cultivation is desirable and economic than other crops.
2)Net energy yield of hemp is also more than most of the crops.
3)Less maintenance.

Improvements in Life Cycle Energy Efficiency and Greenhouse Gas Emissions of Corn-Ethanol

• This paper focuses on the greenhouse gas emission from the corn based biofuel.

• It also discusses how in recent times the net corn production has increased and new ways have been found out to produce more energy efficient biofuel.

• They performed energy life cycle simulation and greenhouse gases assessments.

• The net energy ratio was found out to be ranging from a minimum of 1.29 to a maximum of 2.23

TAKE AWAYS

1)In the pursuit of finding the best crop for biofuel, an improved life cycle energy efficiency is essential.
2)New technological advancements help us to reduce the energy we put into “seed-to-fuel” cycle hence improving the net energy ratio.
3)Improved version of biofuel indicates towards less greenhouse gas emission.

Camelina Derived jet fuel and diesel: Sustainable advanced biofuels

• Builds the case for camelina.

• The paper discusses the biofuel alternatives to jet fuel and diesel.

• It also evaluates the life cycle greenhouse gas emission and compares it with conventional jet fuel and diesel.

• It’s grown without giving much attention as it can sustain extreme temperature and doesn’t require much inputs unlike other plants.

• Biofuel proved to be very cost effective when greenhouse gases are considered as a net minimum saving of about 67% was noted when using camelina based fuel.

• It was concluded that even though camelina based fuel was cost effective and reduced emission to a great extent, its performance and energy efficiency was almost the same when compared to conventional fuels.

TAKE AWAYS

Camelina poses a strong competition to other biofuel crops as the energy requirement for its life cycle is considerably less keeping its energy output the same as the conventional fuel.

A life cycle assessment of biodiesel production from winter rape grown in southern Europe

• The paper states the benefit of biodiesel over diesel in terms of

1)Abiotic Depletion
2)Photochemical oxidation
3)Global warming potential

• This is a life cycle assessment of rapeseed in terms of different climate and net crop yield.

• The highest energy consumed during the life cycle is in transesterification and oil extraction which was found to be 25.22% and 21.30% respectively.

• The study found out that biofuel has a less impact on abiotic depletion and global warming potential.

• Putting the coproducts (glycerin) to use again reduces stress on the environment.

TAKE AWAYS

The reusability of the byproducts.

Exergetic evaluation of biomass gasification

• This paper focuses on biofuel which is in gaseous form.

• It states that most of the energy is lost during the process of gasification and hence wants to make this process more efficient.

• It suggests that by drying the gas may increase the exergetic value of the gaseous biofuel.

• It states in order to reach the maximum efficiency of gas biofuel the right amount of oxygen must be added to the gasifier.

• The data suggests that the exergic value of vegetable oil is greater than other biofuel sources like straw, wood, grass, sludge, manure.

TAKE AWAYS

1)Gasification of biofuel releases some energy into thin air while the process of gasification is in process.
2)This is not at all desirable when dealing with biofuels.

Annual exergy evaluation on photovoltaic-thermal hybrid collector

• Makes a more complete use of solar energy.

• It extracts electric as well as thermal power from solar energy.

• Exergy based comparison and evaluation was done as electric and thermal energy has different units associated with them.

• The paper discusses the problem associated with thermal energy as it requires a certain temperature difference so that we can extract that energy to do some work.

• 3 cases were considered-

1)A simple PV module
2)A PV/T module (Hybrid Cover Less)
3)A PV/T module (Hybrid Single Cover)

• Monthly and annual data were obtained for daily and seasonal variations in solar radiations.

• Findings :

1)It was found out that the exergy gain for electrical energy was high although the exergy gain for thermal energy was much smaller.
2)Electrical exergy was in the order of 
   1)Coverless PV/T
   2)Simple PV
   3)Single Cover PV/T
3)Thermal exergy was in the order of 
   1)Single Cover PV/T
   2)Coverless PV/t

TAKE AWAYS

1)Formulation to find the total exergy.
2)Heat and power generation characteristics.
3)Single covered PV/T should be used as they have high exergy.

Case Studies of large-scale PV systems distributed around desert area of the world

• The author challenges the present conventional energy sources which have a lion share in the energy market with large scale PV establishments.

• Major factors governing a PV power plant design were considered.

TAKE AWAYS

1)PV power plant design
2)Size optimizations 
3)Cost estimations

Cost reduction in PV manufacturing and Impact on grid-connected and building-integrated markets

• This paper suggests different ways to limit the pricing of PV systems to a lower level.

• Increased size of the plant reduces the cost per watt of energy.

• It advocates the use of thin film modules and manufacturing of amorphous silicon for a better cost to efficiency ratio.

• Some of the worlds’ governments have cash subsidies of about 50% in practice.

TAKE AWAYS

1)Roll-to-roll continuous process plants should be adopted rather than batch process plants.
2)Government subsidies makes PV plant cheap.
3)Making use of thin film amorphous silicon.
4)Establishing PV plant in more than one Biofuel growing crop field.

Low cost solar module manufacturing

• The burgeoning solar industry has been expanding many folds which has made the manufacturers to adopt numerous ways to make PV cells affordable.

• PV cells manufacturers have developed several cost cutting ways which will help them against the growing competition.

• This paper gives stress on high automation and a higher throughput capacity of module manufacturing and fabrication plants.

TAKE AWAYS

1)Similar output cells clubbed together to form a module with higher efficiency.
2)An assembler developed by Spire can make series cell soldering a much faster process hence saving time and money.
3)Larger area cells helps in cost reduction.

Photovoltaic systems: A cost competitive option to supply energy to off-grid agricultural communities in arid regions

• In order to connect rural and remote inhabited locations to the power grid, the generating public utility needs to build a network of electrification which seems impractical as far as the cost parameters are concerned.

• The author compares

1)A diesel generator set
2)A PV system

• Procedure conducted

1)Identifying the solar energy potential and the demand. 2)Optimizing the PV cell size to accommodate the demand of entire locality. 3)Comparing the life cycle cost of both systems.

TAKE AWAYS

1)Decentralized power generation.
2)Electrification of such locations are feasible only when the generation is cheap.
3)Although the energy cost of PV electricity is lower, PV was found out to be more capital centric which puts us in a position where we need to find out ways to make the manufacturing and set up cost a couple of notches lower.
4)When set up in locations of high solar irradiations its profitability increases manifolds.

Energy and Exergy analysis of photovoltaic-thermal collector with and without glass cover

• This paper gives a thermodynamics viewpoint on the PV/T collector module.

• PV/T cell with glass cover has a greater total energy absorption while it lowers the photovoltaic efficiency owing to the reduced absorption and increased reflection of irradiation.

• If the thermal energy extraction is secondary with less or little importance then the PV/T should be without cover.

TAKE AWAYS

1)The factors working in favor of  PV/T without cover are
    1)PV cell efficiency
    2)Packing factor
    3)Water mass to collector area
    4)Wind velocity
2)The factors working in favor of PV/T with cover
    1)Ambient Temperature

Low cost processing of CIGS thin film solar cells

• This paper discusses the use of thin layer CIGS (Copper Indium Gallium Selenide) for low cost PV module.

• The machinery required for such kind of module manufacturing is also low as compared to conventional silicon wafer.

• The following properties of CIGS were highlighted

1)High optical absorption
2)Tunable bandgap

• The process manufacturing process of CIGS PV module is explained and it’s also stated that this process can be set up as a roll-to-roll process which in turn decreases its production cost.

TAKE AWAYS

1)CIGS PV module stacks up a very bold case for itself even though the efficiency is compromised.
2)If cost is the primary constraint then the use of CIGS would prove vital.
3)Or even a hybrid combination of silicon wafer and CIGS module would do a great job in cutting down the cost to a great extent.

Photovoltaic technology: The case for thin-film solar cells

• This paper is based on the argument that although the prices of PV cells have gone down with a substantial increase in the our reliability on PV cells, the cost associated with silicone wafer will eventually go up owing to the availability of limited silicon resources.

• Silicone thin film cells are made by depositing silicon which is in its gas phase on a low cost substrate.

• It builds up the case for use of amorphous silicon vs crystalline silicon.

• Amorphous silicon has low deposition temperatures which enables us to use glass (low cost substrate) as a substrate.

TAKE AWAYS

1)Use of polycrystalline wafers instead of conventional monocrystalline could prove beneficial in cutting down cost but the efficiency would be compromised.
2)The thickness of thin film cells being a few microns, this terminates the very problem which was the limited availability of silicon.
3)Amorphous silicon has a higher absorption coefficient than crystalline silicon.

Life cycle assessment and energy pay-back time of advanced photovoltaic modules: CdTe and CIS compared to poly-Si

• This paper stacks up the case for CdTe and CIS PV module against the conventional polycrystalline silicon.

• The efficiencies were found out to be in the order of:

1)CdTe: 9%
2)CIS: 11%
3)Poly-Si: 14%

• CdTe and CIS based PV modules are found out to be toxic in nature. Hence their use and disposable must be done in a reliable manner.

TAKE AWAYS

Thin film operate at higher efficiencies in overcast condition.
Overall performance was found out ot be competitive with poly-Si based PV module.
The choice of CdTe or CIS type PV module will decrease the capital cost but would increase the maintenance and disposal cost.

Cumulative exergy extraction from the natural environment: A comprehensive life cycle impact assessment method for resource accounting

[1] • This article talks about the total exergy derived from nature which is used to generate power in the form we can make use of.

TAKE AWAYS

The exergy data of different resources can be of very vital use in our project.

References

@@ Line 301: / Line 301: @@
 ==Cumulative exergy extraction from the natural environment: A comprehensive life cycle impact assessment method for resource accounting==
+[http://pubs.acs.org/doi/pdf/10.1021/es0711415]
 •	This article talks about the total exergy derived from nature which is used to generate power in the form we can make use of.