This thesis will use the TRL system for assessing the maturity of different technologies for power production on offshore installations. The alternatives will also be rated according to CO2-emission reduction, efficiency improvement and cost. As size and weight are limited on offshore installations, compact and light equipment/systems are advantageable. It is not a part of the official rating system, but the dimensions will be remarked in this report.
As insecurities around cost and a low TRL level often are connected, cost can be left out of the rating system for some new technology options discussed in the thesis, due to high uncertainties. With too high inaccuracies, all cost estimates would be purely speculative, and is therefore better left unreviewed.
2.2.1 TRL
All new technologies go through a research and development phase before being deployed for commercial use. TRL are used to assess the maturity of a particular technology and determine the progress with nine different rating levels. TRL 1 being the lowest and TRL 9 the highest [18]. Table 2-3 gives a detailed description of each level.
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Table 2-3: TRL Level Description [18]
Phase TRL Level Description
Research
1 Basic principles observed and reported.
2 Technology concept and/or application formulated.
3 Analytical and experimental critical function and/or characteristic proof-of-concept.
Development 4 Technology basic validation in a laboratory environment.
5 Technology basic validation in a relevant environment.
6 Technology model or prototype demonstration in a relevant environment.
Deployment
7 Technology prototype demonstration in an operational environment.
8 Actual technology completed and qualified through test and demonstration.
9 Actual technology qualified through successful mission operations.
2.2.2 CO2-Emission Reduction
CO2-Emission reduction will be measured as percentage of the emission from gas turbines on GEA. From ConocoPhillips’ report, burning 1000Sm3 of natural gas in the turbines generates 3.74 MWh of energy and produces 2.21 tons of CO2. The amount of CO2 produced per MWh generated is then:
𝐶𝑂2𝐺𝑇 = 2.21 𝑡𝑜𝑛
3.74 𝑀𝑊ℎ= 0.59 𝑡𝑜𝑛 𝑀𝑊ℎ⁄ (2.1) Where 𝐶𝑂2𝐺𝑇, is the amount of CO2 produced per MWh generated in a gas turbine.
The CO2 emission reduction for alternative power production would then be calculated as:
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% 𝐶𝑂2 𝑒𝑚𝑖𝑠𝑠𝑖𝑜𝑛 𝑟𝑒𝑑𝑢𝑐𝑡𝑖𝑜𝑛 = − 𝐶𝑂2𝑥
𝐶𝑂2𝐺𝑇 ∙ 100% + 100% (2.2) Where 𝐶𝑂2𝑥, is the CO2-emission factor per generated MWh for option x.
For instance, reviewing an option with the same amount of CO2-emission per MWh generated will equal 0% emission reduction, 0.295 tons of CO2 per MWh equals 50%
emission reduction and 0 ton/MWh equals 100% emission reduction.
2.2.3 Efficiency
Efficiency of power generation can be split into electrical efficiency and total efficiency and is denoted by 𝜂. The electrical efficiency is the power output divided by the energy input via fuel flow:
𝜂𝑒𝑙= 𝑃𝑜𝑤𝑒𝑟 𝑜𝑢𝑡𝑝𝑢𝑡
𝐸𝑛𝑒𝑟𝑔𝑦 𝑖𝑛𝑝𝑢𝑡 =𝑊𝑜𝑢𝑡 𝑄𝑖𝑛
(2.3)
The total efficiency, also known as the fuel utilization factor, is the sum of power output and the utilized heat in the exhaust gas (e.g. in Combined Heat and Power plants) to the energy input via fuel flow:
𝜂𝑡𝑜𝑡 =𝑃𝑜𝑤𝑒𝑟 𝑜𝑢𝑡𝑝𝑢𝑡 + 𝑈𝑡𝑖𝑙𝑖𝑧𝑒𝑑 𝐻𝑒𝑎𝑡
𝐸𝑛𝑒𝑟𝑔𝑦 𝑖𝑛𝑝𝑢𝑡 =𝑊𝑜𝑢𝑡+ 𝑄𝑜𝑢𝑡 𝑄𝑖𝑛
(2.4)
A higher efficiency cycle will influence both the power output and the required energy input of fuel amount. Less specific CO2 (i.e. CO2-emission per unit of power output) will be
produced as more of the fuel will transform into power or other energy products such as heat through innovative or combined cycles and cogenerations, and thus less fuel will be needed for the same amount of power output. Burning less fuel will further reduce the CO2
output.
As some of the alternatives presented in this thesis is based on a cogeneration cycle, the efficiency rating will be based on the total efficiency. From this point, efficiency refers to total efficiency unless stated otherwise.
The efficiency improvement compared to the base case is calculated as:
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𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 𝑖𝑚𝑝𝑟𝑜𝑣𝑒𝑚𝑒𝑛𝑡 =𝜂𝑥− 𝜂𝐺𝑇
𝜂𝐺𝑇 ∙ 100% (2.5)
2.2.4 Cost
The cost of the emission reduction technology is an important factor when comparing and choosing between the available options. However, the main focus of this thesis is to study the effect of CO2-emission reduction technology. Cost estimations will therefore be
simplified and done without regards to discount rates and inflation. Although these factors play an important role in future investment decisions, the technical background of the author and time restrictions limits the capacity of investigating this further.
As the different alternatives have different emission reduction potential, looking at the total investment cost would be insufficient. The rating system will therefore be based on the abatement cost of reduced tons of CO2. For an option to be profitable purely from an economical point of view, the abatement cost would have to be lower than the emission cost of CO2, meaning the total cost of one emission allowance from EUs emission trading system and Norway’s CO2-fee for the petroleum industry.
In February 2020, the price for one emission allowance was 274 NOK/ton CO2 [19], adding in the Norwegian CO2-fee for 2020, which is 1.15 NOK/Sm3 gas burned, or 491 NOK/ton CO2
emitted [20], the price of releasing one ton of CO2 into the atmosphere is 765 NOK.
An abatement cost equal to or lower than 765 NOK would therefore make the investment beneficial from both an economical and environmental point of view.
12 2.2.5 Rating System Table
Every option covered in this thesis will be rated according to the factors introduced in this subchapter and are to be inserted into Table 2-4.
Table 2-4: Rating table
Alternative TRL
% CO2 -Emission Reduction
Efficiency Abatement
Cost Comments