For the IE-NETS project we have been examining a number of user-friendly and/or open source energy system models that may be useful in informing policy in aligning climate action with the Paris Agreement and in indicating the possible need for carbon dioxide removal and a timeline for investing in negative emissions technologies to accomplish this.

One such model is EnergyPLAN, developed and maintained by Aalborg University in Denmark, with which users can start by setting up a reference model matching the energy supply and demand infrastructure and parameters of a current energy system. From this, users can then develop a plausible sequence of scenario steps for a low carbon transition. The EnergyPLAN model focuses on achieving a 100% renewables energy system so the modelling of fossil fuel, carbon capture and storage or nuclear power is relatively basic, but the modelling of technologies such as combined heat and power, district heating, energy storage and power-to-fuel is more detailed.

Though not open source, EnergyPLAN is well documented, easy to use and runs quickly in a Microsoft Windows operating system. Building the reference model from available data takes time but once completed alternative scenario options can rapidly be explored. Hourly balance of the energy system enables a reasonably fine grained look at a scenarios involving high capacity and grid penetration of variable renewables combined with modelling of synthetic liquid or gaseous fuel production to use excess energy production and store it for use in periods when there is insufficient wind or solar.

David Connolly's Green Plan Ireland

Using the EnergyPLAN energy system simulation model, while at Aalborg David Connolly (now CEO of the Irish Wind Energy Association) proposed Green Plan Ireland, a series of six steps in demand management and renewable energy development, by which Ireland could potentially transition its energy system to being based on 100% renewables energy supply  (Connolly and Mathiesen, 2014). You can see the paper, a video presentation and all data via links at the Green Plan Ireland webpage. For each of these steps the EnergyPLAN output data gives a net value for CO2 emissions. The Aalborg modelling does assume that all bioenergy is “carbon neutral” – as per current EU methodology and policy, though at odds with much science – but does aim to limit bioenergy use.

In this blogpost we very simplistically imagine fully accomplishing one of these steps every five years up to 2050, draw a straight line between of these annual emissions levels and then add up the total CO2 emissions of this imagined Green Plan Ireland emission pathway to 2050. We then compare this CO2 commitment to the possible Paris-aligned CO2 quota for Ireland as estimated in previous IE-NETS work. This is only an exploratory assessment, nonetheless it does give a blog-level exploratory view that can set some basic context for the timeline of low carbon transition planning.

In outline, Green Plan Ireland begins with Step 1, a reference model matching the projected Irish energy system as of 2020, followed by a transition of energy supply to 100% renewables by 2050 via the following six steps:

• Step 1. Reference model

• Step 2. District heating (2020)

• Step 3. Heat pumps for building heat

• Step 4. Electricity grid regulation

• Step 5. Demand side management (DSM) and electric vehicles & (EVs)

• Step 6. Synthetic methanol/DME

• Step 7. Synthetic methane production

For the purpose of this modelling energy demand is assumed to stay constant in terms of total and sectoral breakdown. The last two steps in particular require large scale expansion of wind energy, especially offshore, so that excess capacity can enable energy storage via synthesised chemical energy storage in electrofuels: synthetic liquid fuels (methanol and/or  dimethyl either) and synthetic gaseous fuel (methane). Running EnergyPLAN for each scenario step gives a value for nett annual CO2 emissions for each one. Using an import/export‐corrected fuel account, the model additionally calculates a value for “corrected CO2 emissions”. At Step 7 in the Green Plan the EnergyPlan modelling of the Irish energy system yields marginally negative CO2 emissions, at least on a corrected basis (and assessing bioenergy as CO2 neutral).

In the chart below an emission scenario imagines fully accomplishing each one of the six steps from 2020 to 2050, assuming that 2015 to 2020 emissions are flat at the Step 1 Level of just over 38 MtCO2 per year from the energy system (although in fact we know they have increased in 2016). Drawing a straight line between each of these annual emissions way points then gives us an imagined emissions pathway to 2050. We will come back to the dashed green pathway that is also shown.

As shown in the next chart below, we can then sum the CO2 emissions starting in 2015 and adding on each year of emissions (from the values in the annual chart above) to get a cumulative total pathway to 2050. This is important because cumulative CO2 emissions are the predominant driver of long-term global warming and climate change, and therefore provide a gauge of Ireland's climate action policy effectiveness. For the scenario shown the annual emissions from 2015 to 2050, add up to cumulative CO2 calculated as just over 1000 MtCO2 (or about 900 MtCO2 after correcting for import/export).

In IE-NETs we have presented previous work based on the current scientific estimates of  the remaining, nett global carbon budget range of CO2 emissions from 2015 onwards, necessary to align global action with the Paris Agreement temperature target of “well below 2ºC”. For Ireland, a population-based share of the mid-point of this global carbon budget is only 586 MtCO₂. Though representing some attempt at equity, this “equal per capita” allocation of the budget is overly generous: it cannot be said to be properly “equitable” (as the Paris Agreement demands) because it does not account for responsibility for past emissions, current high emissions or capacity to act. In any case, allowing for Ireland’s ongoing nett land use CO2 emissions reduces the quota share for energy system emissions to about 534 MtCO₂, which is shown as a dotted green line in the chart below. (Note: Glynn et al. 2018 uses a different global carbon budget basis and arrives at a somewhat higher 766 MtCO2 quota for Ireland using the same type of allocation.) The green dashed "Even Effort Path" line in both charts shows the effect of a constant fractional reduction rate pathway of -7.1% per year, starting at the 2015 level - which would (asymptotically) use exactly the estimated cumulative quota.

Cumulative CO₂ Implications for Paris-Aligned Climate Action Policy

This very simple assessment sets the Green Plan Ireland steps defined by Connolly and Mathiesen into a sequential, 5-yearly series to 2050. The charts indicate that this apparently extremely ambitious plan, which does achieve very deep emissions rate reduction by the final stage in 2050, still does not limit Ireland’s cumulative CO2 emissions to even a minimally equitable Paris-aligned carbon quota.

Cumulative emissions as shown go above the quota limit before 2030 and go on to exceed the quota by a total of 350 to 400 MtCO2. This is similar to the scale of maximum technical potential for negative CO2 emissions to 2100 estimated earlier in the IE-NETS project. Therefore, following such a pathway would commit Ireland to achieving these very high levels of negative emissions, using what are currently speculative technologies in terms of both cost and performance with large implications for land use area needed, for example to produce energy crops for bioenergy with carbon capture and storage (BECCS). Even if faster or other mitigation measures are applied it seems likely that some level of negative emissions capacity may be needed, requiring investment in at least some carbon capture and storage.  This CCS capacity might need to be prioritised for bioenergy rather than abating interim fossil fuel emissions (the so-called “fossil fuel bridge” model) so that negative emissions can be realised.

Of course, it is possible that the Green Plan steps could be planned to overlap in time and begin much earlier in terms of investment and achievement so that the decarbonisation pathway followed in Ireland’s ‘low carbon transition’ is far closer to the required target path. Critically, it is the final two steps that have the largest effect on total energy system emission reductions. This suggests that early investment in development in synthetic fuel R&D and capacity building, including offshore wind turbines might need to be a critical focus for mitigation planning in order to incorporate these key changes as early as possible in the energy system transformation, thus yielding the maximum impact on cumulative CO2 emissions.

It is evident from the charts that early and deep mitigation effort are needed to limit the large, subtractions from the carbon quota due to ongoing high emissions. The Green Plan only looks at energy supply to meet current sectoral demands, so near-term measures that achieve real cuts in absolute demand would greatly assist in mitigation. Energy efficiency may help here, but only if carbon pricing or supply regulation is sufficient to eliminate rebound effects that encourage spending of cost savings. Immediate phase-out of the most carbon intensive fossil fuels in electricity production, peat and coal, would provide an important early benefit.

To be “cost effective”, as demanded by Ireland’s Climate Act, mitigation action must add up to meeting a science-based target, in this case a Paris-aligned carbon quota, with a high degree of certainty. By definition, not meeting the target is not cost effective, so the choice is then between options that meet the target at least cost. Existing investment guidance is often based on near-term carbon prices which do not reflect the climate impacts if the science-based targets are exceeded; and this may preclude investment in what are ultimately likely to be the most important technologies – possibly including failing to invest early in synthetic fuel production as indicated above for the Green Plan. On the demand side, the option to reduce existing high emitting activities in favour of potentially economic lower emitting activities can too easily be omitted from mitigation studies that may be overly influenced by the present economic mix. Research shows that early, substantial investment is required for the those areas thought most difficult to mitigate. Likewise, the possibility of large new energy demands, such as the promotion of new data centres, may need to be considered carefully relative to decarbonisation pathways.

Ongoing work in the IE-NETS project is further examining and modelling the required scale and speed of emission reductions to align Ireland’s climate action with the Paris Agreement, including possible tacit commitment to achieving some level of negative emissions. The simple scenario sketched above echoes the overwhelming consensus of international climate mitigation research: any and all delay in actually achieving deep decarbonisation quickly risks likely failure to meet Ireland’s Paris commitment. As the Sustainable Energy Authority of Ireland state in their recent submission to the Oireachtas (Irish Parliament) Committee on Communications, Climate Action and Environment:

The longer the delay of annual total (net) emissions reductions (in the order of 10% per annum) the more challenging and costly future decarbonisations become. Modelling scenarios will need to be updated to ensure they are based on achieved levels of decarbonisation in each accounting period, and in the event of delayed mitigation will indicate a shrinking time horizon for fossil fuel use, and the need for costlier solutions such as negative emissions technologies (e.g. bioenergy CCS) in the future.