ELEC9715 Electricity Industry Operation and Control Assignment 1
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ELEC9715
Electricity Industry Operation and Control
Assignment 1
This assignment will be distributed to you Wednesday of week 4. It is due midnight Friday of week 6. Your submission should be a pdf document. The assignment must be submitted individually on the course moodle via Turnitin, and must be your own work. The UNSW policy on student plagiarism can be found on the www.lc.unsw.edu.au website and you should note that the university uses automated software to check assignments.
The assignment will be marked out of 20 (4 marks per question plus 4 marks for presentation). The two assignments over the course are worth 25% of your final assessment. Late submission without good reason, as explained in an email to the course lecturer prior to the due submission time, will see marks reduced as per the details in the Course Guide. Late submissions must be directly emailed to the lecturer as well as uploaded into Moodle. In keeping with the recommended hours per week of study for a six unit of credit course, (around 10 hours of self-directed work per week additional to the 4 contact hours), we expect that you will spend in the order of 15 hours of so in total on this assignment. The assignments are excellent preparation for the final exam, hence worth doing well, and it is essential, and a UNSW requirement, that you do it yourself.
You should look to make your assignment like a consultancy report – ie. professional presentation with figures, tables and graphs. It is excellent practice for the technical report writing you have to do as an engineer in the electricity industry sector. You should briefly outline your methods for answering the questions in the report - engineers show their working. All tables must be pasted in as tables rather than pictures so that they are searchable via text (a requirement for Turnitin) - if you put tables in your report that can’t be ‘text’ searched then it will not be marked. Finally, when I say ‘discuss your findings’ I mean discuss them. Engineers shouldn’t just present numerical analysis but try to also help (often non-engineer) readers to understand what it means.
Electricity industry operation and control is determined by the operational capabilities of all supply, network and end-use equipment. A key question is how the operational characteristics of existing and potential new generation technologies, as well as electricity demand, will shape future industry operation.
Question 1:
The Australian Energy Market Operator (AEMO) has recently updated its technical and cost estimates for all existing and a range of possible new utility generators for its planning studies. These studies are an input into its forthcoming 2024 Integrated System Plan (ISP). This requires AEMO to model operation of the Australian National Electricity Market (NEM) under a range of possible future generation and network scenarios. This, in turn, requires that they estimate key technical characteristics and capital and operating costs of all existing generation and potential new generation technologies. The latest (2023) data for this is available on the AEMO website as an Excel spreadsheet . It’s a very interesting read and you may well wish to look at it and see how AEMO undertakes its modelling. However, to simplify the assignment we also provide a cut-down version on the course moodle. The cut down assignment AEMO modeling work book has a sheet /Existing Gen Data Summary’ with estimates (based on the AEMO data but with some additional assumptions) of the minimum operating levels and operating costs for all the coal and gas generating plants in Queensland, as well as hydro and utility wind and solar plant, pumped hydro and battery energy storage in the State.
Plot the generation supply curve (Incremental variable cost $/MWh versus MW system generation for economic dispatch) for the Queensland thermal plant mix (all coal, gas-fired and liquid fuelled generators) for two possible carbon price scenarios ($0/tCO2 and $100/tCO2 - the current price of permits under the EU Emission Trading Scheme), and two gas price scenarios (the provided gas pricing from AEMO but also a scenario where gas prices are 50% higher than these numbers). For the second carbon scenario, all the fossil fuelled plants are required to play for each tCO2 they emit, adding to their operating costs from Variable O&M and fuel purchasing. For simplicity ignore transmission losses and constraints. For the second gas price scenario, you will need to adjust all the fuel prices for the gas plant by raising them by 50% from their current levels. All the coal and gas units are committed - that is on-line and required to operate somewhere between their minimum and maximum output.
You will first need to calculate the ‘sent out’ operating cost – short run marginal cost or SRMC - ($/MWh) for each generator for each carbon price, and gas price scenario . The spreadsheet is set up to assist in this. Note that you should still explain your working in the assignment so its clear you know how the calculation works. You’ll then need to sort them from lowest to highest incremental operating costs.
i) Plot the four supply curves (one for each carbon price scenario, and gas price scenario) on a single graph . These curves represent the cost of the power system providing an additional MWh of demand - that is System Short Run Marginal Cost or SRMC as a function of demand for electrical energy over the entire range of economic dispatch . Discuss the implications of a carbon price or possible future gas price rises on economic dispatch of the Queensland thermal plant, and particularly any impacts on the merit order (that is, the order of generating plant technologies from lowest to highest operating cost)
We are now going to consider all current Queensland generation including the coal and gas plants but also hydro, wind and utility PV, and even battery storage.
ii) You now need to add existing hydro generation to the supply curve. Note that there are really three types of hydro generation to be modelled. Run of river plants effectively run whenever there is water flow - for some schemes these plants effectively look like constant output generators (more water than required at all times of the year) with only variable operating costs to cover. The problem as discussed in lectures, is that a lot of hydro plants are energy constrained - that is, their water actually has an opportunity cost/value. The third type is pumped hydro plants. Plot the Queensland supply curve for a zero carbon price now including all the non-pumped hydro units (Barron and Kareeya), assuming that they are run of river and have zero operating cost .
iii) Now add existing wind and solar to the supply curve. The main challenge here is the high variability of wind and solar. Section ii) shows the supply curve if the wind isn’t blowing and the sun isn’t shining. Now plot the supply curve for a zero carbon price for two cases – midday on a sunny day across Queensland when the utility solar is all operating at rated capacity but there is no wind, and on a windy winter evening in Queensland when the utility wind power is all operating at rated capacity but there is, of course, no solar power Discuss the implications of Queensland wind and solar on the generation supply curve and its implications for meeting State demand as it varies from a minimum of around 3000MW to its maximum of around 10000MW. In particular, do you envisage periods where coal and gas plants would ideally be turned off, or when there may be insufficient generation to meet demand?
iv) Now add the pumped hydro (wivenhoe) and battery energy storage plant to the curve. For reasons that will be explained later in the course, one way to model energy constrained and pumped hydro plants and battery energy storage systems is to consider them as having an relatively high operating cost. For this assignment we will assume they have an operating (actually opportunity operating) cost of $300/MWh (hint, this is based on the standard call option pricing in the NEM).Therefore, add the pumped hydro and battery plant to the curve with an operating cost of $300/MWh.
Please put on the same plot the curves for the zero carbon price and AEMO gas pricing scenario, as well as the curves for parts ii, iii and iv. Briefly summarise their implications for economic dispatch in the Queensland region as wind and solar deployment increases and coal plant continue to retire.
Question 2:
This question involves analysis of actual generating plant operation in the NEM. You have been given access to NEMSight - an extremely powerful commercial package for analysing NEM data. Details for accessing NEMSight are available on the course Moodle. You will want to use its ‘Time Machine’ function to analyse several Queensland generators and characterize their operation over the calendar year 2022.
Choose one plant in Queensland for each of the following technologies:
- Coal
- Gas fired unit – CCGT or OCGT
- Utility wind or solar farm
- pumped hydro generator or battery energy storage system (only one of each in Queensland)
You will want to eyeball historical data for your chosen plant to make sure there aren’t any surprises - eg. not operating for most of the year (a particular issue with some of the renewable generators that have only recently been commissioned, or may not have even been connected yet). NEMSight offers very useful charting of data, and if you wish to analyse it further you can then right click on the chart and it will allow you to copy the data as a table which you can then paste into Excel.
i) For each of your chosen plant, use 5 minute dispatch data to estimate as best able the following operating characteristics:
a. Highest ramp rate seen over the year (up or down) in %RatedCapacity/min. Don’t consider starts and stops in this calculation – ramp rate is the change in output over 5 minutes when the plant stays operating. This can be a little tricky with very fast plant like OCGTs, pumped hydro and definitely BESS where they can go from zero to rated output pretty quickly. For coal plants on the other hand, they might go from zero to minimum operating level pretty quickly in the data, but the plant was actually started some time prior to this.
b. achieved capacity factor over the year % (actual output divided by possible output if plant operated at its max output for every hour of the year)
c. % of five minute periods over the year where it was generating at least some power
d. Number of starts in the year (ie. Going from zero output to generation)
e. operating profit over the year, using the operating cost estimates from Question 1 above for the zero carbon price and AEMO gas price scenarios, and the regional spot prices over the year (available from NEMSight).
Note that some plants may have been ‘down’ for extended periods over the past year – best to select another plant. A number of these plants, particularly thermal coal and gas plants and hydro, have multiple units that can cause some complexities for the analysis. You should analyse a single unit. Finally, note that we will be checking for assignments that analyse the same generators given there is a choice available– this assignment is meant to be done individually. My advice is to first eyeball the data of a range of plants to get a feel for the general operation of different plants. Then you can write simple data analytics, using a wide range of helpful Excel functions, to characterize their operational characteristics.
Be sure to put your results in a table. Please comment on your findings, and the operational flexibility of different generation technologies, and the potential implications for Queensland electricity sector operation.
ii) Using 5 minute Queensland scheduled demand data for 2022 (available from NEMsight – be sure to use scheduled demand), determine the following:
a. Average demand (MW) over the year
b. Highest 5 minute demand (and when it occurred – date and time).
c. Lowest 5 minute demand (and when it occurred – date and time)
d. Highest up ramp rate (MW/min)
e. Highest down ramp rate (MW/min)
f. Effective capacity factor of demand (%) with respect to highest 5 minute demand seen over the year 2022.
Be sure to put your results in a table and discuss their implications, particularly with respect to the variability of Queensland demand compared with wind and utility PV.
Question 3:
An Excel spreadsheet is available on the Moodle that has 30 minute household data for approximately 100 houses in the Ausgrid network region of Sydney for a complete year. Each house has metered load (kWh over 30 minutes) for both what is termed General Consumption (GC) and Controlled Load (CL). GC measures all household electricity consumption other than controlled loads. The CLs are typically hot water systems and/or pool pumps - which are electronically controlled through either a timer, or via ripple control as instructed by the distribution network service provider. CLs are separately metered because they can be flexibly dispatched by the network operator and therefore pay a lower tariff (c/kWh) rate. Somewhere around half of NSW households have CLs although this is falling as off-peak hot water systems are replaced.
The dataset also includes Gross (total) Generation (kWh over 30 minutes) (GG) from the household PV system. While the Ausgrid data set has different capacity PV systems on each house we have standardized the PV system size to 4kW – the average PV system across Australia.
You will analyse the house number that matches the last two digits of your student number – eg. if your student number is s1234567 you will analyse house 67. Note that some houses have very questionable data suggesting metering errors or PV system failure – if that is the case for your house, please note this in your report, explaining the issue, and then use the next house number. Note that you must use the house data corresponding with your student number or explain why not.
For your particular house,
i) estimate as best able from the 30 minute data over the year:
- highest GC demand (kW) and day (date day/month) and time it occurred (24 hour eg. 17:00 = 5pm)
- average GC daily consumption (kWh/day) over the year
- highest CL demand (kW) and date (day/month) and time at which this occurred (only relevant of course if your house has CL)
- average CL daily consumption (kWh/day) over the year
- proportion of total household load which is CL over year (%)
-annual electricity bill for the house assuming no PV, GC tariff of 30c/kWh and CL tariff of 12c/kWh
ii) For the PV system, estimate as best able from the 30 minute data over the year
- average PV capacity factor (%) (with respect to provided 4kW PV system capacity) over year.
- peak net export of PV generation (kW) if any (that is, greatest PV generation exports to grid after removing GC and CL demand) and the day (date day/month) and time at which this occurred.
- annual electricity bill for the house given the consumption tariffs above, and an export tariff (when the PV generation exceeds total GC and CL load in a 30 minute period) of 5c/kWh.
Again, I suggest you first graph the output for your house to ‘eye -ball’ its load and PV behavior before then using some of the available Excel spreadsheet functions to identify the factors above. Always apply a sanity check to your answers, and be sure to use the units suggested above. In particular, note that 1kWh consumed in 30 minutes reflects a load consuming 2kW.
Be sure to put your results in a table. Please comment on your findings, and their implications for power system operation to meet residential load in NSW.
Question 4:
Consider a very simplified version of the Queensland generation fleet and State demand as a competitive electricity market as outlined in table 1 below. For convenience, you can assume that no generators have minimum operating levels hence no fixed variable costs. Their incremental variable costs apply across their entire operating range. Assume that there are no transmission constraints or losses, and ignore the existing transmission interconnections between NSW and Queensland. Note that we now consider rooftop PV in Queensland, but keep in mind that it doesn’t participate in the market but, instead, appears as reduced demand to be met by utility generation (including wind and utility PV).
We assume that there are four large market participants in Queensland, Stanwell which owns coal generation, CS Energy which also owns coal-fired generation, Origin Energy which owns gas generation and CleanCo which owns gas generation and pumped hydro as well as a Battery Energy Storage System (BESS) . Each market participant can offer one quantity/price pair into the market for each of its plant. Note that the PV and wind generation in the state is bundled into generic, multiple owner, participants for simplicity, and because they are likely to be market price takers rather than makers . The market operates at hourly intervals. The market operator AEMO bids its load forecast for each hour into the market at a Market Ceiling Price (MCP) of $15400/MWh, equivalent to its estimate of the short-run marginal benefit (SRMB) of electricity demand . Yes, you can model demand operating profit on the basis that electricity is worth $15400/MWh to all loads (quite the assumption but actually how almost all Australian NEM demand is currently offered into the market).
Assume for simplicity that the wind and solar are market participants who don’t earn income from PPAs, and that the pumped hydro and BESS is offered into the electricity market at $300/MWh. Consider three possible hourly scenarios of renewable generation and demand:
1) all wind farms and utility PV plants able to generate at their rated output and household PV generating at 3000MW (a very windy and sunny spring day in Queensland) with demand at 6500MW (underlying demand, hence not considering the impact of household PV generation) .
2) Wind farms not generating and utility PV at 1200MW and household PV at 600MW (a calm yet very hot summer evening in Qld) with demand at 10000MW (lots of air-conditioning running)
3) A cold still winter evening with no wind generation, no solar generation of course, and demand of 10,000MW (lots of electrical heating running)
unit type |
maximum output (MW) |
incremental variable cost ($/MWh) |
Stanwell Coal |
3000 |
50 |
CS Energy Coal |
4000 |
40 |
Origin CCGT |
500 |
90 |
Origin OCGT |
800 |
160 |
Clean Co CCGT |
500 |
100 |
Clean Co OCGT |
700 |
150 |
Clean Co pumped hydro and BESS |
600 |
0 (but offers at $300/MWh given opportunity cost) |
Various owners Wind Various owners Utility PV |
800
3000 |
0
0 |
Rooftop PV |
3000 (note that 5000MW installed but never operates at its maximum potential) |
Not applicable as behind- the-meter and outside market |
Solve the following cases of market dispatch for each of the three renewables/demand scenarios:
(i) None of the generation participants are engaging in strategic (gaming) bidding into the market. What is the market clearing price (MCP) ($/MWh), dispatch (MW) and surplus/profit ($'000/hr) for each participant, and surplus ($'000/hr) of the load given the assumed MCP. (please use tables to present these answers). What is the total system surplus ($'000/hr)?
(ii) Participant CS Energy has now decided to attempt to exert its market power to improve profits. Assume
that the other generators and the load will continue 'preference revealing' bidding. Assume that all participants have excellent knowledge of the true maximum power outputs and incremental variable costs of all their competitor's generating units, and the demand quantity and incremental variable benefit of the load. How might CS Energy offer into the market (quantity, price) to maximise its profits under the different renewable energy and demand scenarios? What would then be the market clearing price, dispatch and profits for each participant and surplus of the load? Is there any change in the total power system surplus?
(iii) Instead of participant CS Energy attempting to exert market power, it is now Origin Energy which is
attempting strategic bidding in order to increase its profits. Assume that all the other generation participants and the load use 'preference revealing' bidding into the market. How might Origin Energy offer into the market (quantity, price) to maximise its profits under the different renewable energy and load scenarios? What would then be the market clearing price, dispatch and profits for each generator and surplus of the load?
Be sure to put your results in tables as appropriate. Please comment on your findings, and their implications for market prices and the exercise of market power in the Queensland region of the Australian NEM.
2023-03-14