Bringing together smart electricity grids, thermal grids and gas grids to form a Smart Energy System is the key to becoming 100% renewable and creating 100,000 jobs, writes Dr David Connolly


Author: Dr David Connolly, associate professor, Aalborg University, Denmark

As we move into the dark and cold winter months, it is very likely that you are reading this article with the aid of a light bulb and in the comfort of a warm building. These services and their abundance are iconic of the luxuries we enjoy in a 21st-century Ireland, but unfortunately, our appreciation for these essential services has not evolved as fast as our dependence on them.

I studied mechanical engineering at the University of Limerick for four years. During my final year, I joined a study tour to Moneypoint power station, Ireland’s largest power plant, in the west of Co Clare. This was going to be an exciting trip, since we were also completing a course on power plants during this period, so my classmates and I were well equipped with questions for the tour guide ahead.

Although it was almost 10 years ago, I still have many clear memories from the tour that day: the shipyard, the turbine room, the control room and many more. But one memory will stay with more than any other, a very short memory, about a very simple question: where does the heat go?

The tour guide was explaining the production process that occurs in the power plant: the coal is delivered, the coal is burned and the electricity is produced. The scale of the plant was extremely impressive. Moneypoint can provide electricity for approximately 500,000 households. During the discussions, the tour guide explained that only 35-40% of the energy from the coal is converted into electricity, while the rest of the energy is produced as heat. It led to that question, where does the heat go? The simple answer was: into the river Shannon. From that moment, I knew energy would become my career.

How can we live in a society where 60% of a product is simply thrown away? More importantly, how can we live in a society where 60% of a product, the energy from coal, which is loaded with so much political and environmental concerns, is simply thrown away? Note that this 60% is enough heat to supply approximately 300,000 households. For me, answering this is no longer just a simple question; it is a personal ambition and my everyday work for the last seven years.

The structure of the energy system in Ireland is extremely simple, although its scale still makes it very challenging to operation. Figure 1 provides a graphical representation of the key components in the Irish energy system, demonstrating how electricity, heating and transport are provided today. The two key features from this diagram are:

  • All of our energy demands are linked back to fossil fuels; and
  • Our electricity, heating and transport are very separate from one another.

This second point relates to both the technologies that are used to produce our energy and to the institutions and policies that govern these different sectors. These two key features are very important, since ultimately our ability to change these will define how much we can avoid the inefficiencies of today and also move towards a renewable-energy system in Ireland in the future.

New Picture

Figure 1: Interaction between sectors and technologies in Ireland’s energy system today

Replacing fossil fuels

Looking again at Figure 1, it is very clear what will have the biggest impact on our energy system in the future: the removal of fossil fuels. If we take fossil fuels out of our current system, then the backbone of our electricity, heating and transport systems will be gone. There are now so many strong reasons about why we need to replace fossil fuels that even if one is proven incorrect, the others will more than justify the effort. For example:

  • Fossil fuels have been reported as the primary driver of global climate change by the United Nations many times, most recently again in Intergovernmental Panel on Climate Change Fifth Assessment Report, which was released in November of this year;
  • Almost all fossil fuels are imported into Ireland every year, costing us approximately €6 billion each year;
  • Fossil-fuel supplies are regularly at the centre of many sensitive geopolitical battles, something Europe has become particularly aware of this year during the Ukrainian discussions with Russia;
  • Finally, and most importantly, there are alternatives to fossil fuels. These alternatives can produce our energy demands at a cheaper price, without emissions, and at the same time create more local jobs compared to fossil fuels.

There are two principal alternatives to fossil fuels: bioenergy and intermittent renewable energy (such as wind, solar, wave and tidal resources). Bioenergy is an ideal replacement for fossil fuels since it contains many of the same characteristics. Biomass is a solid fuel so it can replace coal, biogas can replace gas, and biofuel can replace oil. By doing so, a lot of the existing fossil fuel infrastructure can be reused with bioenergy. However, the key drawback is that bioenergy is a limited resource that competes with many other essential services, primarily food production.

Although this puts a limit on bioenergy consumption, it is still good news for the bioenergy industry. The key message here is that we need to use as much bioenergy as possible in the future, but it will need to be supplemented by intermittent renewable energy.

Intermittent renewable energy has developed at a very rapid pace in the last two decades, to the point where it is now possible to produce electricity at a cheaper price from a wind turbine than it is from a power plant in Ireland [1, 2]. However, the key challenge for the energy system will be accommodating the variable production from these resources. When fossil fuel is removed from the energy system, it not only reduces the amount of fuel available, it also reduces the amount of stored energy in the energy system.

Fossil fuels are essentially very large amounts of stored energy in solid, gaseous or liquid form. For example, when you turn on a light switch in your house, you send a request for more electricity from the grid. This additional electricity can be produced by placing more fuel in a power plant, thus converting the ‘stored’ energy in the fossil fuel to electricity as soon as request it from the grid.

Unfortunately, wind energy does not possess this wonderful attribute, but instead it behaves in the opposite way. Instead of being available on demand whenever we need it, the wind varies beyond our control. This means that the flexibility provided by fossil fuels over the last 200 years will need to be replaced in the future if we are to successfully introduce intermittent renewable energy such as wind power.

Smart Energy Systems: new forms of efficiency and flexibility

One of the most common forms of flexibility presented as a solution for the energy system is electricity storage. It is very intuitive from a technical perspective to understand how electricity storage functions: where there is too much wind power production, the surplus electricity is stored, and when there is too little, the electricity storage is emptied. This ‘silver bullet’ potential was one of the main reasons that electricity storage was the central topic in my PhD thesis.

However, after three years of research, I came to the conclusion that there are cheaper forms of flexibility in the energy system than electricity storage. These are district heating grids, electric vehicles and synthetic fuels. Each of these key pieces of infrastructure allow intermittent renewable energy to access cheap forms of flexibility in the energy system, while also replacing fossil fuels in other parts of the energy system. These technologies bring together smart electricity grids, smart thermal grids and smart gas grids to form an energy system concept known as the Smart Energy System, which is displayed in Figure 2.

New Picture

Figure 2: Interaction between sectors and technologies in a future Smart Energy System. The flow diagram is incomplete since it does not represent all of components in the energy system, but the blue boxes demonstrate the key technological changes required

District heating enables wind power to access thermal storage via large-scale heat pumps, electric vehicles provide access to cheap electricity storage (since its final purpose is to replace oil in the transport sector), and synthetic fuels connect wind power to fuel storage. To put this in context, thermal storage is ~100 times cheaper than conventional electricity storage such as pumped hydroelectricity energy storage (PHES), while gas and liquid fuel storage are ~100 times cheaper than thermal storage (see Figure 3).

It is possible to access these new forms of flexibility in the Smart Energy System thanks to the integration of the electricity, heating and transport sectors with one another (see Figure 2). The Smart Energy System concept has been developed by the Sustainable Energy Planning Research Group at Aalborg University, Denmark, for over 20 years. Earlier this year, I applied this concept to the Irish energy system to quantify what we need to do and what the impact will be.

New Picture

Figure 3: Typical costs and efficiencies of electricity, thermal, gas, and liquid fuel storages [3-6]

Green Plan Ireland: quantifying the impact

Green Plan Ireland is a peer-reviewed study that was published in the International Journal of Sustainable Energy Planning and Management earlier this year [7]. In this study, I quantified the impact of implementing the Smart Energy System in Ireland in terms of energy, emissions, and economy, over seven key steps:

  1. Reference scenario (starting point representing a ‘business-as-usual’ future);
  2. Introduction of district heating;
  3. Installation of small and large-scale heat pumps;
  4. Reducing grid regulation requirements;
  5. Adding flexible electricity demands and electric vehicles;
  6. Producing synthetic methanol/DME for transport; and
  7. Using synthetic gas to replace the remaining fossil fuels.

The steps illustrate how each technology can both improve the efficiency of the Irish energy system and allow more wind power to be utilised. The analysis was carried out using a computer program called EnergyPLAN, which simulates the electricity, heating and transport sectors on an hourly basis. This ensures that the solutions analysed in the study are technically possible to implement.

There are a number of significant changes that occur during this transition from today’s energy system (Figure 1) to the Smart Energy System (Figure 2), which are beyond the scope of this article, so here I will highlight some of the most significant, which are:

  • There are no fossil fuels being consumed in the Smart Energy System;
  • Since there are no fossil fuels, there are also no carbon dioxide emissions;
  • Wind power accounts for over 80% of the electricity production and over 60% of total energy demand in the Smart Energy System, which is possible due to the new forms of flexibility that have been created;
  • The total cost of providing energy in Ireland in a 100% renewable energy system will be 30% more than the original fossil fuel reference scenario based on 2020 prices, but it will be the same price as the fossil fuel reference scenario based on 2050 prices (see Figure 4).
  • The type of costs in the energy system will change from fuels to investments, when the energy system is converted from the fossil-fuel based reference scenario to the renewable-based Smart Energy System (see Figure 4). An investment-based energy system can have the same total cost of energy as a fuel-based energy system, but the people who end up with the money in their pocket can be very different.

Investing in local infrastructure results in more domestic jobs in Ireland compared to importing fuel from another country, which is why the Smart Energy System scenario results in 100,000 additional jobs in Ireland.

New Picture

Figure 4: Annual costs of each stage in the transition based on 2050 prices

Finally, in the Smart Energy System, if someone asked where does the heat go? to a power plant operator, then the answer would not be into the river Shannon. Instead, it would be into the buildings using a district heating pipe. This technology has been around for over 100 years and the concept is used to provide over half of the heating in Denmark, so I believe that this is one place where we can begin developing the Smart Energy System in Ireland today.

As part of my research, I have co-ordinated an EU study which developed a heating strategy for Europe for the year 2050. During this study, our team created the first ever pan-European heat atlas to identify where district heating is feasible in Europe. Looking at the Irish results from this study, our results indicate that approximately one-third of the heat demand in Ireland is in areas with a heat demand sufficiently high to develop district heating.

This means that one-third of the heat in Ireland can be supplied by heat that is currently wasted in the Irish energy system. This will save us approximately €400-500 million per year on our fossil fuel import bill. Now that’s the start of a Smart Energy System!

Dr David Connolly is an associate professor in energy planning with the Sustainable Energy Planning Research Group at Aalborg University in Copenhagen, Denmark. His main areas of research are the design and assessment of 100% renewable energy systems, with a key focus on the integration of intermittent renewables, district heating, electric vehicles and the production of synthetic fuel for transport. He graduated from mechanical engineering at the University of Limerick in 2007, receiving the university’s Gold Medal for the highest results of that graduating year. He then went on to complete a PhD in energy planning, also at the University of Limerick, after being awarded an Advanced Scholars Award from the university and a PhD scholarship from the Irish Research Council for Science, Engineering and Technology. He won the Globe Forum ‘Early Career Research Award’ at the 2010 Globe Forum conference on sustainability and in 2011, he joined Aalborg University. See:

Green Plan Ireland

Green Plan Ireland is a peer-reviewed study that was published in the International Journal of Sustainable Energy Planning and Management in 2014. The study quantifies the impact of transitioning Ireland’s energy system from fossil fuels to 100% renewable energy, in terms of energy, economy, and emissions. The transition to broken down into seven key steps to illustrate the key technological changes required during the transition. These steps are based on the Smart Energy System approach developed at the Sustainable Energy Planning Research Group in Aalborg University.

See: Connolly D, Mathiesen BV. ‘A technical and economic analysis of one potential pathway to a 100% renewable energy system.’ International Journal of Sustainable Energy Planning and Management 2014;1:7-28.


[1] Connolly D, Mathiesen BV, Dubuisson X, Lund H, Ridjan I, Finn P, Hodgins J. ‘Limerick Clare Energy Plan: Climate Change Strategy.’ Aalborg University and Limerick Clare Energy Agency, 2012. Available from:
[2] Clancy M, Gaffney FM. ‘Quantifying Ireland’s Fuel and CO2 Emissions Savings from Renewable Electricity in 2012.’ Sustainable Energy Authority of Ireland, 2014. Available from:
[3] Federal Energy Regulatory Commission. ‘Current State Of and Issues Concerning Underground Natural Gas Storage.’ Federal Energy Regulatory Commission, 2004. Available from:
[4] Dahl KH, Oiltanking Copenhagen A/S, 2013: Oil Storage Tank. Personal Communication, Received 30 September 2013.
[5] PlanEnergi, Teknologisk Institut, GEO, and Grøn Energi. ‘Udredning vedrørende varmelagringsteknologier og store varmepumper til brug i fjernvarmesystemet.’ Danish Energy Agency, 2013. Available from:
[6] Connolly D. ‘The Integration of Fluctuating Renewable Energy Using Energy Storage.’ Department of Physics and Energy, University of Limerick, Limerick, Ireland, 2010. Available from:
[7] Connolly D, Mathiesen BV. ‘A technical and economic analysis of one potential pathway to a 100% renewable energy system.’ International Journal of Sustainable Energy Planning and Management 2014;1:7-28.,energy,fossil fuel,Ireland,renewables
  Author: Dr David Connolly, associate professor, Aalborg University, Denmark As we move into the dark and cold winter months, it is very likely that you are reading this article with the aid of a light bulb and in the comfort of a warm building. These services and their abundance are iconic of...