Shaping Ireland's Energy Future: EirGrid and Mott MacDonald's Use of PLEXOS® to Power Tomorrow's Energy Scenarios

EirGrid and Mott MacDonald: Preparing Ireland's power system for a net-zero future

EirGrid, the Transmission System Operator (TSO) for Ireland, plays a critical role in shaping the country’s energy future by operating and developing a secure, sustainable, and modern electricity grid. Working towards Ireland’s target of 80% renewable electricity by 2030 and net-zero emissions by 2050, EirGrid is leading the transition toward a clean energy system. 

Mott MacDonald is a global engineering, management and development consultancy. Energy is one of its core practice areas where the organization has deep technical expertise. Mott MacDonald partners with energy organizations to develop responsible solutions to support demand growth and the evolution of energy simultaneously.  

Together, EirGrid and Mott MacDonald embarked on Tomorrow’s Energy Scenarios (TES) 2023, a comprehensive modeling project designed to map potential pathways to net-zero for the Irish power system. The study used PLEXOS® to evaluate four future pathways with different tradeoffs and trajectories.

Increasing complexity: Challenges in decarbonizing Ireland’s power system

Like many European countries, Ireland has ambitious decarbonization goals and mandates. EirGrid, as Ireland's TSO, is at the forefront of the country's energy transition. It faces several critical challenges in meeting ambitious national and EU climate objectives, including: 

• Increasing Decarbonization targets: Aiming to achieve 80% renewable energy in electricity generation by 2030 and net-zero emissions by 2050. 
• Load growth: Managing the increasing demand for electricity due to population growth, electrification of transport and heating, and growing industrial needs. 
• Resource adequacy: Ensuring a reliable supply of electricity as the role in the system for variable renewables becomes larger. 
• Intermittency: Addressing the intermittency of renewable energy through energy storage, back up thermal generation, and interconnections with other countries.
• Balancing technologies: Planning for a balanced portfolio of technologies, including renewable generation, thermal generation, and emerging potential solutions like green hydrogen, battery storage, and carbon capture. 

TES 2023 was undertaken with the above in mind, and in the context of changing policies that are driving high offshore wind ambitions, increasing electrification, and significant carbon budgets. These challenges require EirGrid to use advanced solutions to model future scenarios, optimize investment decisions, and ensure a reliable and sustainable electricity supply. 

Modeling complexity with precision: Why EirGrid and Mott MacDonald chose PLEXOS®

To support the design and analysis of TES 2023, EirGrid and Mott MacDonald selected Energy Exemplar’s integrated modeling platform, PLEXOS, for its advanced capabilities in energy system modeling and optimization. The decision was driven by PLEXOS’ unique capabilities, including:  

• Scenario analysis: PLEXOS enables multi-scenario projections to assess the impact of different policy, technology, and market conditions on the energy system. 
• Capacity expansion modeling: PLEXOS enables capacity expansion modeling to determine the most effective investments in new generation, storage and network. 
• Granular modeling: The PLEXOS platform uses mixed-integer programming to realistically model technical constraints such as generator ramp rates, start-up costs, and renewable intermittency. 

TES 2023: Insights from strategic energy transition planning

Using PLEXOS, the team developed TES 2023 which consisted of four contrasting but plausible net-zero pathways for Ireland.  

1. Self-sustaining – High renewables, rapid technology development, and limited reliance on energy imports. 
2. Constrained growth – Moderate renewable expansion with a heavier and more prolonged reliance on fossil fuel backup. 
3. Offshore opportunity – Maximum levels of offshore wind deployment to achieve decarbonization and become a large energy exporter. 
4. Gas evolution – Green hydrogen plays a key role in decarbonization of the energy system. 

Lofty offshore wind opportunity requires build constraints in long-term modeling

Achieving the offshore wind deployment levels in the Offshore opportunity scenario required minimum build constraints in the long-term (capacity expansion) model. In the other scenarios, the long-term model was freer to optimize offshore wind capacity, and in these scenarios, installed offshore wind capacity came in much lower.  

Short-term modeling minimizes curtailment in two scenarios

As a small islanded system, the Republic of Ireland and Northern Ireland already has high levels of wind penetration and periods of curtailment. For this reason, in the short-term models, EirGrid was interested in looking at the level of surplus generation on the system in each scenario. In the short-term modeling, it was found that surplus generation and curtailment would occur in all scenarios but was most pronounced in the Offshore opportunity.  

Competing methods for system reliability

Variable renewable generation is present in all four scenarios and, as a result, alternatives will be required to fill gaps to maintain system reliability. The four possible methods for achieving system reliability are: renewable generation and battery storage, full conversion of gas networks to hydrogen, carbon capture and storage (CCS) on existing and new thermal plants, and unabated thermal plants balanced with bioenergy with carbon capture and storage (BECCS). Each of these four options present their own challenges, including cost and feasibility of infrastructure buildout.

Hydrogen looks to be a strategic rather than economic move 

The modeling also showed that hydrogen infrastructure use and buildout will primarily be driven by the electricity sector. The challenge is that demand for hydrogen for power generation is also extremely variable. This makes it a challenging profile for investment from a purely economic standpoint; however, hydrogen does provide value from a strategic standpoint in terms of energy security and long-term storage.  

Key results – Addressing complex challenges in Ireland’s energy transition

Using PLEXOS, EirGrid developed its "Tomorrow's Energy Scenarios 2023" (TES 2023), which outlines pathways to meet Ireland's decarbonization goals. The software guided decisions on where and when to invest in renewable capacity, storage solutions, and electricity interconnection. By running hundreds of simulations with different constraints, PLEXOS provided insights to key questions like potential future levels of surplus energy and how different technologies can come together to form a generation mix capable of supporting growing electricity demand and reducing CO2 emissions. 

EirGrid achieved significant results by partnering with Mott MacDonald and using PLEXOS for its energy transition planning, including:  

1. Comprehensive scenario development: TES 2023 identified four distinct pathways—Self-sustaining, Constrained growth, Offshore opportunity, and Gas evolution—each tailored to achieve net-zero emissions between 2040–2050. 
2. Informed policy recommendations: Insights from PLEXOS modeling informed EirGrid and its key stakeholders on planning for the development of the electricity system. 
3. Decarbonization pathways: The software supported the planning and evaluation of different decarbonization pathways, (e.g. ones based on green hydrogen or on LDES) and allowed for informed conversations on their relative pros and cons. 
4. Stakeholder collaboration: PLEXOS facilitated dialogue with stakeholders by providing transparent modeling results that demonstrated how Ireland could achieve policy targets around electrification and decarbonization. 

By using PLEXOS, EirGrid addressed complex challenges in Ireland’s energy transition. The platform provided the analytical rigor needed to plan for a rapidly changing energy system. This case study highlights the importance of advanced modeling capabilities in navigating the complexities of modern energy systems.