The US has set an ambitious target of achieving 30 GW of offshore wind (OSW) power by 2030 to support energy transition. Given the huge task of building this capacity almost from scratch, the federal government is supporting the sector’s development through several measures. Various states, particularly on the East Coast, have also set individual OSW targets to meet their long-term renewable energy (RE) goals and have engaged in large-scale OSW procurements. As of July 2021, eight East Coast states have set a target of about 39 GW of offshore wind cumulatively by 2035 and seven have already procured or are developing 14 GW of this capacity. Four of these coastal states (New Jersey, Maryland, Virginia and North Carolina) are in the PJM Interconnection region, which comprises 13 Mid-Atlantic and Midwest states as well as the District of Columbia. Bringing this plan to fruition requires considerable transmission planning and investment both onshore and offshore.

To this end, in October 2021, PJM released a report titled ‘Offshore Wind Transmission Study: Phase 1 Results’, which presents a framework for future transmission planning studies between PJM and states. It is a PJM-wide reliability study to determine onshore grid reinforcements required to reliably deliver not only the 14,268 MW of announced OSW (by three states up to mid-2021) (refer to Table 1) in the PJM region, but also to meet the region’s state renewable portfolio standards (RPS) targets by determining the necessary renewable capacity by resource type and location. The states and PJM decided that the study would be split into two parts. In the first phase, PJM developed and analysed  five scenarios—one modelled for the short term up to 2027 and the other four for the long term up to 2035—with inputs from agencies from five coastal states including Delaware. The study estimates that only USD2.2 billion to USD3.2 billion will be needed for onshore transmission based on the assumption that the PJM states will add 81.7 GW of renewable capacity (45.6 MW of solar, 14.5 GW of onshore wind, 14.4 GW of offshore wind, and 7.2 MW of energy storage) to meet their 2035 RE goals.

So far, the transmission solutions needed to integrate renewable resources have primarily been advanced through PJM’s generation interconnection queue. However, taking a holistic and regional assessment of interconnecting multiple large-scale OSW resources could maximise the efficiencies in transmission planning. Initially, the study focuses on enhancing the existing infrastructure required to reliably integrate OSW generation. The consideration of greenfield transmission solutions and offshore transmission facilities will be incorporated in the second phase of the study. Broadly, transmission reinforcements and renewable generation would lower customer costs by reducing the use of more expensive fossil-fuelled power plants and removing transmission bottlenecks on the grid while allowing for more exports to the Midcontinent Independent System Operator (MISO).

Assumptions and scenario development for OSW injection

The Phase 1 scenario components were determined through collaborative discussions with the Offshore Transmission Study Group (OTSG), which comprises PJM and state representatives, in the fourth quarter of 2020. Initially, six scenarios were developed in Phase 1, but Scenario 3 was subsequently removed before the modelling and analysis commenced.

The components include two OSW variables—point of interconnections (POIs) to the onshore transmission system and OSW injection amounts at each location. In addition, the other variables are generator deactivations; meeting state RPS requirements through solar, onshore wind and battery storage; as well as incorporating electric vehicle and energy efficiency policy targets captured as part of the PJM load forecast. All scenarios assumed the RPS requirements were met for the considered period. While Scenario 1 considered only the announced generation deactivations as of October 1, 2020, all other scenarios included 1,739 MW of unannounced deactivations.

States could incorporate sensitivity studies to help develop their OSW plans across scenarios. To assess system impacts, states could ask PJM to model the same OSW injection totals at different POIs to compare the system impacts. The scenarios also allowed coastal states to have PJM model OSW injection totals that were greater than their current policy targets, allowing them to assess how much additional capacity the system could manage and the estimated costs of any identified upgrades. Virginia used this kind of sensitivity analysis and based on the results, decided to reduce the total injection amounts to match its current policy targets for all scenarios, except for Scenario 4, where it requested PJM to model 7,800 MW of offshore wind injecting into their state by 2035. PJM analysed offshore wind injection ranging between 6,416 MW in the short-term Scenario 1 and 17,016 MW in the long-term Scenario 4 (refer Table 2).

The study identifies 10 POIs for the Phase 1 scenarios. Of these, seven POIs—BL England, Cardiff, Deans, Larrabee, New Freedom, Oyster Creek and Smithburg—were included by New Jersey across scenarios. Delaware and Maryland used Indian River as their only POI in all scenarios. Meanwhile, North Carolina and Virginia selected Fentress and Landstown as their two POIs. Notably, Maryland and Delaware’s OSW scenario components were combined within each scenario as Maryland’s planned OSW project MarWin is seeking interconnection in Delaware. Similarly, North Carolina and Virginia were combined as the former did not have any planned OSW policies at the time of the scenario development for Phase 1.

Analysis and cost estimates

The study used a PJM-wide generator deliverability reliability analysis in Phase 1 and examined the effect of various transmission and generation contingencies on PJM transmission facilities to assess the bulk electric system’s ability to deliver renewable generation to load centres across the PJM footprint. To determine transmission line overloads and identify the most expensive onshore transmission requirements, transmission line conductor limits were used.

PJM made certain assumptions about the scope of work required to mitigate the overloads to determine order-of-magnitude cost estimates. In case of a relatively small violation on a transmission line, it was assumed that the line could be reconductored while the towers and insulators could be reused. Conversely, the transmission line and structures would need to be fully rebuilt in case of a significant overload. For the five scenarios, cost estimates were identified to be USD627.34 million in the short-term scenario and between USD2.16 billion and USD3.21 billion for the long-term scenarios. Scenario 1 comprises upgrades to be done by 7 utilities while other scenarios include upgrades to be carried out by 14 utilities in the region.

  • Scenario 1 assumes a total of 6,416 MW of OSW injection and meeting RPS targets through 2027. Several of the OSW injection locations and capacity corresponds to actual OSW projects that have been announced including the 248 MW MarWin project, and the 1,100 MW Ocean Wind I (selected in New Jersey’s first OSW solicitation). The transmission reinforcement cost estimate under this scenario is approximately USD627.34 million. The results indicate the potential need for a new 500 kV tie line between Pennsylvania and Maryland to support the delivery of generation from the mid-Atlantic coastal states to the rest of PJM. This new 500 kV tie line was required in each of the longer-term scenarios as well.
  • Scenario 2 models a total OSW injection of 14,416 MW, representing the actual anticipated OSW capacity to be operational in PJM by 2035 based on state legislation and project capacity. The transmission upgrades for Scenario 2 are expected to cost USD2.46 billion, which are mainly driven by the considerable increase in renewable penetration levels considered.
  • Scenario 4, which assumes an OSW injection of over 17 GW, requires transmission upgrades worth USD3.21 billion, exceeding the Scenario 2 cost estimate by over USD700 million. This is primarily attributed to a further increase in Virginia’s OSW assumptions, with an additional 2.6 GW added to the 5.2 MW already included in Scenario 2. This additional capacity resulted in the need for multiple new 500 kV line reinforcements across the Dominion zone that were not identified in Scenario 2.
  • Scenario 5 transmission upgrades are expected to cost USD2.59 billion. This scenario is almost identical to Scenario 2, except that in New Jersey the 500 kV Smithburg POI was moved to the 500 kV New Freedom POI. This resulted in a bottled generation scenario, which would require additional modifications in the southern part of New Jersey. 
  • Scenario 6 transmission upgrades are anticipated to cost USD2.16 billion. This scenario also had a lot in common with scenarios 2 and 5. One of the 1,200 MW New Jersey OSW 500 kV POIs was removed, while the remaining 500 kV POI was lowered by 900 MW, resulting in a 2,000 MW drop in New Jersey OSW injection. This resulted in a large reduction in transmission demand.

The way forward

The PJM study presents state policymakers with a potential set of coordinated transmission solutions as they move forward with their existing and future OSW projects. It is a crucial starting point for future possibilities of integrating RE capacity into the PJM system. It lays a framework for future collaborative transmission planning studies between PJM and its member states. Based on the Phase 1 results, states may request new scenarios for PJM to model in Phase 2. The results from both phases can help guide the coastal states in constructing their offshore wind solicitations. They can also pursue transmission solutions identified in this study further, such as through the state agreement approach, which is being used by New Jersey in conducting the country’s first OSW transmission solicitation in coordination with PJM.

The US offshore wind sector is buzzing with activity with its recent policies and plans focused on meeting ambitious carbon emission reduction and RE targets. To ensure that transmission does not become a bottleneck to the sector’s development, a holistic transmission planning approach must be adopted sooner rather than later. PJM’s recent study, which considers renewable integration comprehensively, is a step in the right direction.  

The article has been sourced from Global Transmission Research and can be accessed here