COURSEWORK ASSIGNMENT HELP-Comparative Techno-economic Evaluation of Four Biomass-to-Electricity Systems
COURSEWORK ASSIGNMENT
Comparative Techno-economic Evaluation of Four Biomass-to-Electricity Systems
In this assignment you are required to carry out an analysis of the performance and cost characteristics of four biomass-to-electricity systems. The analysis involves the construction of charts showing overall efficiency, specific capital cost and cost of electricity as a function of rated power over the range 2.5 MWe to 25 MWe (in 2.5 MWe steps) for each of the four systems. The systems are then to be compared in a report, and the influence of certain factors examined. The analysis to be carried out using Microsoft Excel.
The four biomass-to-electricity systems are:
| PyrEng: | Fast pyrolysis (fluidised bed) with compression-ignition engine, including intermediate liquids storage (diesel pilot to engine can be ignored) |
| GasEng: | Atmospheric gasification (fluidised bed) with spark-ignition engine, including tar cracker and gas clean-up |
| IGCC: | Pressurised gasification (fluidised bed) with gas turbine combined cycle, including hot gas clean-up |
| Combust: | Combustion (moving grate) with boiler and Rankine cycle |
Various data are provided, based on techno-economic studies carried out as part of a research project. Some data are given as fixed values, either for individual systems or all systems, and some as linear functions of biomass input rate. Various definitions are also provided, and additional information may be found in the course notes. Cost parameters for novel technologies are to be calculated for the 10th plant replication.
You are required to perform the analysis under the following scenarios:
- Feed cost £30 per oven-dry tonne (i.e. zero moisture); no learning factor (i.e. 0%).
- Feed cost £30 per oven-dry tonne; learning factor 20%.
- Feed cost £50 per oven-dry tonne; learning factor 20%.
- Feed cost £10 per oven-dry tonne; learning factor 20%.
For each scenario your report should contain three charts, one for each of the three parameters
(unless they are duplicated). Each chart should show four curves over the rated power range 2.525 MWe in 2.5 MWe steps, one for each system. There is no need to give an extensive description of methodology, but the results should be fully discussed, with particular reference to the technical reasons underlying them, and the effects of scale, feed cost and learning factor. Critically assess the results, commenting on any suspected inaccuracies (remember, the provided data are often only estimates). Try to obtain data for overall efficiency, specific capital cost and cost of electricity for other generating systems (e.g. fossil-based, nuclear, other renewables), and compare these with the results you have produced, commenting on the implications for biomassto-electricity systems.
Fixed Inputs
| Feed LHV (wet) | MJ kg─1 | 8.42 |
| Life of project | y | 20 |
| Interest rate | 10.0% | |
| Labour rate | £ man-day─1 | 80 |
| Overheads | % y─1 | 2.5% |
| PyrEng | GasEng | IGCC | Combust | |
| Capacity factor | 0.85 | 0.8 | 0.8 | 0.9 |
| Preparation Current plant no. Future plant no. |
5 10 |
Mature |
Mature |
Mature |
| Drying Current plant no. Future plant no. |
Mature |
Mature |
Mature |
Mature |
| Conversion Current plant no. Future plant no. |
1 10 |
1 10 |
1 10 |
Mature |
| Generation Current plant no. Future plant no. |
5 10 |
5 10 |
5 10 |
Mature |
Functions
All functions are of the linear form f = A + Bx, where:
x is wet feed input to the plant (50% moisture wet basis) in kilotonnes per year A, B are constants, given below
Functions are only valid in the range 2.5 – 25 MWe net electrical output.
Note functions for efficiencies will return values in the range 0-1.
All capital costs are Total Plant Costs (i.e. to point of commissioning).
| PyrEng | GasEng | ||||
| A | B | A | B | ||
| Efficiencies
Conversion efficiency |
|
0.62 |
0 |
0.74 |
0 |
| Generation efficiency | 0.387 | 2.63E-04 | 0.356 | 3.13E-04 | |
| Current capital costs Feed preparation |
£k |
-44.3 |
34.3 |
-42.8 |
26.3 |
| Drying | £k | 134.0 | 6.79 | 116.0 | 6.63 |
| Conversion | £k | 3461 | 49.1 | 5220 | 123.0 |
| Generation | £k | 286.0 | 58.7 | 176.0 | 71.1 |
| Operating costs Feed transport |
£k y─1 |
-41.2 |
2.97 |
-41.2 |
2.97 |
| Utilities | £k y─1 | 36.9 | 5.86 | 49.3 | 5.32 |
| Maintenance | £k y─1 | 22.1 | 9.66 | 53.6 | 11.4 |
| Labour requirement | man-days y─1 | 423.0 | 14.5 | 422.9 | 14.5 |
| IGCC | Combust | |||||
| A | B | A | B | |||
| Efficiencies
Conversion efficiency |
|
0.87 |
0 |
0.777 |
0.000162 |
|
| Generation efficiency | 0.383 | 0.000756 | 0.202 | 0.000324 | ||
| Current capital costs Feed preparation |
£k |
-155.0 | 22.1 |
-170.0 |
21.4 | |
| Drying | £k | 97.7 | 6.89 | 104.0 | 3.44 | |
| Conversion | £k | 7170 | 162.0 | 1930 | 48.1 | |
| Generation | £k | 859.0 | 140.0 | 1000 | 25.7 | |
| Operating costs Feed transport |
£k y─1 |
-41.2 | 2.97 |
-41.2 |
2.97 | |
| Utilities | £k y─1 | 54.7 | 1.26 | -27.2 | 2.86 | |
| Maintenance | £k y─1 | 105.0 | 13.1 | -11.1 | 3.89 | |
| Labour requirement | man-days y─1 | 651.0 | 22.3 | 423.0 | 14.5 | |
Various Definitions
| Rated power:
|
The net power exported by the power plant if it is running at full load (i.e. at its design point). | |
| Overall efficiency:
|
Annual net electricity delivered from the plant to the grid, in GJ y─1, divided by annual fuel input to the plant in GJ y─1, usually expressed as a percentage. It is equal to conversion efficiency multiplied by generation efficiency. | |
| Specific capital cost:
|
Total capital cost of the power plant (on a Total Plant Cost basis) divided by rated power from the plant (see Capacity Factor), expressed as £ kWe─1. Capital cost consists of four elements: preparation, drying, conversion and generation. | |
| Cost of electricity:
|
Total annual operating cost of the system divided by annual net electricity delivered from the plant to the grid, expressed as p kWh ─1. Total annual operating cost consists of seven elements: feed production, feed transport, labour, utilities, overheads, maintenance and annual cost of capital. | |
| Annual cost of capital:
|
An annual cost equivalent to the total capital cost spread over the lifetime of the project. Used for accounting and planning purposes. The method of calculation is given in the supporting slides for this coursework. | |
| Learning factor:
|
For a novel technology, the amount the capital cost reduces by every time the number of plants in operation doubles. This reflects the learning process (improved configuring, reduced item costs etc.). The method of calculation of the actual capital cost reduction factor given a current and future plant number is given in the supporting slides for this coursework. Where a technology is described as mature, the capital cost reduction factor is unity. | |
| Conversion (efficiency):
|
The conversion stage is defined as that at which the biomass is upgraded to an intermediary product. For pyrolysis systems it corresponds to the pyrolyser, with bio-oil as the intermediary product; for gasification systems it corresponds to the gasifier, with product gas as the intermediary product; for combustion systems it corresponds to the combustion furnace and boiler, with steam as the intermediary product. Conversion efficiency is defined as the efficiency of conversion of energy in the raw biomass to energy in the intermediary product. | |
| Generation (efficiency):
|
The generation stage is defined as that at which the intermediary product is converted to electricity, and can be either the dual fuel engine, gas turbine or steam turbine and associated electrical generator. Generation efficiency is defined as the efficiency of conversion of energy in the intermediate product to electrical energy delivered to the grid. | |
| Overheads:
|
Annual overhead charge is here expressed as a percentage of total capital cost. | |
| Feed preparation:
|
The feed preparation stage includes biomass reception, handling, screening, grinding (if necessary) and storage. Drying is considered as a separate stage. | |
| Feed production:
|
The cost associated with feed production is represented simply as a price per tonne (before transport) multiplied by annual supply. The feed in this case is wood with a moisture content of 50% (wet basis), which has been chipped before transport. Note the price is given on a dry basis. | |
| LHV:
|
Lower heating value, expressed in MJ kg─1. All efficiencies are on an LHV basis. | |
| Wet basis:
|
Moisture content on a wet basis is defined as [mass of moisture] divided by [mass of moisture plus mass of dry solid], usually expressed as a percentage. | |
| Labour:
|
The cost associated with labour is calculated as product of the labour requirement and the labour rate. | |
| Capacity factor: | The number of kilowatt-hours delivered by a plant in a year divided by the number that could be delivered if the plant ran at its rated power continuously throughout the year. | |
The structure of the report should include the below subjects:
1.0 Introduction and methodology.
1.1 Introduction to Biomass systems.
1.1.1 Fast Pyrolysis (PyrEng):.
1.1.2 Atmospheric gasification (GasEng):.
1.1.3 Pressurized gasification (IGCC):.
1.2 Methodology for the excel calculations.
3.1 Scenario 1 (No learning factor included).
3.2 Scenario 2, 3 and 4 (Learning Factor 20%).
4.1 Scenario 1 (0% Learning Factor and 30 £/t Feed cost).
4.2 Scenario 2 (20% Learning Factor and 30 £/t Feed cost).
4.3 Scenario 3 (20% Learning Factor and 50 £/t Feed cost).
4.4 Scenario 4 (20% Learning Factor and 10 £/t Feed cost).
*Note: The graphs of the scenarios for the systems and their Specific Capital Cost, Overall Efficiency and Electricity Cost, all been provided in the attached Excel sheet.
