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Railbelt low carbon
ACEP study evaluates options for renewable power generation in the region
Alan Bailey for Petroleum News
The Alaska Center for Energy and Power at the University of Alaska, Fairbanks, has published the results of a study into possible strategies for decarbonizing the Alaska Railbelt electricity generation grid by 2050. Rather than developing an actual plan for decarbonization, the purpose of the study was to evaluate the technical viability and potential cost of decarbonization scenarios, to inform the Alaska public and decision makers on the cost and power supply reliability issues associated with decarbonization.
On Jan. 19 members of the project team presented the findings of the study to the Alaska Senate Resources Committee.
A two-year project Phylicia Cicilio, research assistant professor in power systems engineering, told the committee that the project took 2 years to complete and consisted of six main components: scenario development; electricity load forecasting; power generation analysis; power transmission analysis; and economic analysis. Telos Energy Inc., a company that specializes in the analysis of isolated electrical systems, participated in the study. And the project team consulted with a technical advisory group from the four Railbelt electricity cooperatives, the Alaska Energy Authority and the Railbelt Regional Coordination Group.
Cicilio said that the study evaluated four scenarios: a continuation of the current arrangements for power generation; the use of a combination of wind, solar and hydro; the use of wind, solar and tidal power; and the use of wind, solar and nuclear power. All the scenarios assumed a roughly doubling of electricity demand by 2050 as a consequence of population growth and the increased use of electric vehicles and electrically powered heat pumps for heating buildings.
To identify plausible decarbonization projects for the scenarios the team primarily used existing projects or projects that are being proposed and studied. However, for wind and solar generation, the analysts did add some other potential projects. According to the project report, wind sites, for example, would have proximity to the transmission system, at locations with viable wind resources. The East Forelands site on Cook Inlet was selected for a potential tidal energy system, and nuclear generation sites were assumed at Healy in the Interior and at Beluga in Southcentral Alaska, the report says. And for future hydro power generation the project team assumed the development of the major Susitna-Watana hydropower project on the Susitna River that was proposed a number of years ago.
The team found that some level of gas-fueled power generation would be needed to ensure adequate power supply stability and reliability in all of the scenarios other than the scenario involving nuclear power. However, gas consumption in the decarbonizing scenarios would be very much lower than in the "business as usual" scenario. In the case of the nuclear power scenario the team discounted the continued use of natural gas fueled power generation, given an assumption that nuclear power, in the form of small modular reactors, would prove more expensive than gas fueled power but would be able to underpin electricity supply stability in a similar manner to gas generation.
Assistant professor Jeremy VanderMeer told the committee that the team developed what seemed a reasonable portfolio of generation assets for each scenario. He commented that wind and solar power proved the cheapest forms of power generation all scenarios, but that there is an upper limit to the amount of these types of generation that can be used in practice, given the cost of curtailing peaks in wind and solar output if there is too much of these resources in the system. Moreover, sources of firm power involving some combination of hydro, nuclear, fossil fuel and batteries would be necessary to ensure supply reliability.
According to the study report, zero-carbon power generation in the low-carbon scenarios would range from 70% of total generation in the wind/solar/tidal scenario to 96% in the wind/solar/nuclear scenario. There would be 11.4% zero-carbon generation in the "business as usual" scenario.
Detailed simulations Derek Stenelik from Telos Energy said that the project team conducted detailed simulations of how each scenario might operate on an hour-by-hour basis across an entire year. The simulations took into account changing electrical loads; the availability of wind and solar; reliability needs; and operating constraints. The simulations assumed that a single entity controls the optimization of power dispatch across the system.
Using a cost simulation computer system that is widely used in the industry and is used by the Railbelt utilities, the researchers analyzed the potential operation of the system, the system stability, fuel consumption and operating costs.
The team found that in the three decarbonization portfolios wind and solar, currently the lowest cost renewable energy resources, formed the backbone to power generation, supplying more than 50% of the energy. And ensuring reliable electricity delivery on a typical winter day, for example, involved much more moving around between different generation sources than happens in the current electrical system.
Battery technology is a key enabler, both to ensure grid stability and to shift energy from times of high renewable energy production to times of low production. However, further analysis of the impact of very high renewal power output on the system is needed, Stenelik said.
Needs an adequate transmission system And an adequate transmission system is critical to all of the scenarios, with the decarbonization scenarios requiring much more electrical flow in both directions, north and south, across the Railbelt transmission network than in the "business as usual" situation. The transmission grid needs to be larger than at present, able to transfer more power, to be more operationally flexible and to be coordinated by a single entity, Stenelik said.
Natt Richwine from Telos Energy said that decarbonization would involve a major shift in the manner in which the transmission system operates, given that power generation would shift significantly from the use of big rotating generators such as gas turbine systems to the use of computer driven inverter technologies that connect solar, wind farms and battery systems, for example, to the grid.
System stability The project team conducted simulations of how the electrical system would work using todays conventional technologies and identified significant issues with system stability. After simulating different means of addressing this problem the team determined that some means of mitigating stability problems would be required. The team assessed the potential use of a new technology called grid forming inverter technology to address this issue and as a consequence recommends the use of this technology in conjunction with decarbonizing the grid. Essentially, computer technology at each generation or battery storage site would interconnect with each other, to help coordinate all of the plants on the high voltage electrical system.
High capital costs Research professor Steve Colt said that the capital costs of implementing any of the decarbonization scenarios would be much higher than the capital costs of maintaining "business as usual." The wind, solar and hydro scenario would be especially expensive at around $12 billion, in particular because of the high cost of building the Susitna-Watana hydro system. The estimated capital costs of the other two decarbonization scenarios range from a little under $8 billion to around $10 billion. The capital cost estimates assume that projects would be conducted in time to qualify for federal investment tax credits which expire in 10 years. The study report indicates that the capital cost estimates include the potential costs of necessary transmission grid upgrades.
Also, in any decarbonization scenario there is a significant but not overwhelming cost associated with the batteries and other technologies that would be needed to support system reliability, Colt commented.
Business as usual also expensive On the other hand, continuing with business as usual would involve billions of dollars of expenditure over the years for the purchase of natural gas fuel. That would push up the total cost to something similar to the cost of a decarbonization option. The purchase of gas would involve continuous fuel costs, while the capital costs would presumably be recovered through electricity rates over the years. Thus, although there are huge uncertainties over what the actual cost of any scenario might be, it appears that all of the scenarios, including "business as usual," fall within a broadly similar cost ballpark, Colt suggested.
Asked how legislators might influence decisions over future developments in the electrical system, Stenelik commented that it would be helpful to put some certainty into the energy transition through some form of energy standard or renewable portfolio standard.
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