Ireland’s renewable-energy target for 2020 is based on some significant innovations in the electricity sector, particularly in relation to the integration of wind power. The 16% renewable energy target for 2020 contains a 40% renewable electricity target, with wind power providing the majority of this, placing Ireland amongst the world’s elite when it comes to the integration of variable renewable electricity production. Significant progress has been made to date, with over 25% of Ireland’s electricity supply coming from wind power in 2015 [1], so it seems likely that Ireland will be close to its renewable electricity target in 2020. Without doubt, this is the highlight of Ireland’s energy transition so far, but it does pose one obvious and difficult question: what happens after 2020? How much more wind power can Ireland implement beyond 30-40% of electricity production? Furthermore, how do we do it?

Variability of wind power

Over the last decade, the primary solutions being pursued to accommodate the variability of wind power in Ireland have come in three major forms: flexible power plants (i.e. gas), interconnection and demand-side management. Each of these can most definitely help with the expansion of more wind energy in Ireland, but these are all ‘electric’ solutions for an electricity sector problem. In my opinion, we need to think beyond this electricity sector focus in the future to expand wind power beyond a 30-40% penetration rate in an efficient and cost-effective manner. Before joining the Irish Wind Energy Association, I worked as an associate professor at Aalborg University in Denmark, where I developed low-carbon energy strategies for various EU countries. Denmark is a unique place to be in the energy sector, since there is political support at government level for a 100% renewable-energy system by 2050. Therefore, the focus during many of the discussions in Denmark is not focused on interim 2020 EU targets, but on the longer-term end goal at a national level of 100% renewable energy. With this in mind, in collaboration with many of my former colleagues at the Sustainable Energy Planning Research Group in Aalborg University, I developed a on a concept called the ‘Smart Energy System’. The name is built on the term ‘smart grid’, which is often used to describe a smarter and more flexible electricity sector that can facilitate more renewable electricity. The Smart Energy System is based on the same principles but, rather than solve the variability of renewable energy within the electricity sector alone, the Smart Energy System goes beyond the electricity sector and into the heat and transport sectors as well. I have previously applied the Smart Energy System concept to Ireland in a peer-reviewed study called ‘Green Plan Ireland’ [2], which describes how wind power in Ireland could supply over 80% of our electricity demand in the future (the study is freely available online). This also formed the basis of a previous article I published in the Engineers Journal in 2014 called ‘Green Plan Ireland: our chance to become 100% renewable’. By going beyond the electricity sector and instead applying an energy system perspective, more cost-effective opportunities for the integration of wind power become apparent such as: 1) new demands 2) cheaper energy storages and 3) more efficient production methods. Below, I briefly present an example of these new opportunities, but you are invited to read the Green Plan Ireland study if you would like some additional information [2].

Energy storage: an example of ‘energy system’ thinking

One of the most intuitive methods to accommodate the variable nature of wind power is energy storage: charge when there is too much and discharge when there is too little. With an electricity system perspective, energy storage is limited to technologies that can be charged and discharged in the form of electricity, with the most common forms including: pumped hydroelectric energy storage (PHES), compressed air energy storage (CAES), batteries and flywheels. Therefore, these technologies are not necessarily ‘energy storage’ facilities, but are in fact ‘electricity storage’ facilities. Using ‘energy systems’ thinking instead reveals many other energy storage options for wind power such as thermal, gas, hydrogen and fuel storage. The benefits of this broader energy system perspective is evident when comparing the cost of these various energy storage technologies. Here four of the most common forms of energy storage in each of these categories are compared, including:
  • Electricity storage: in the form of pumped hydroelectric energy storage like ESB’s Turlough Hill facility in Ireland;
  • Thermal storage: based on large-scale hot water storage in steel tanks that are typically found on district heating systems. For example, Denmark has approximately 280 of these facilities [3];
  • Gas storage: based on the storage of natural gas in underground caverns;
  • Fuel storage: in the form of oil storage tanks, often seen beside refineries or shipyards.
These four types of energy storage are compared in terms of their unit investment cost (€/MWh), which is the upfront investment required to build a typical facility (€) as a function of how much energy is stored in the facility (MWh).

Unit investment cost for thermal storage

[caption id="attachment_36420" align="aligncenter" width="300"]Figure 1: Unit investment cost comparison between electricity, thermal, gas, and fuel storage [4] CLICK TO ENLARGE Figure 1: Unit investment cost comparison between electricity, thermal, gas, and fuel storage [4][/caption]As displayed in Figure 1 (above), the unit investment cost for thermal storage is almost 100 times lower than the corresponding value for electricity storage, while fuel storage is over 100 times cheaper than thermal storage. Therefore, by expanding the scope beyond the electricity sector and into other parts of the energy system, such as heat and transport, it is possible to identify energy storage solutions that are ~100-10,000 cheaper in terms of their unit investment costs than electricity storage. In a world beyond 30-40% wind power, these cheaper forms of energy storage will become a vital part of the energy system. Additional changes will be required to connect wind power with these cheaper forms of energy storage, so these are described in more detail in the Green Plan Ireland study [2]. The key message in this article is that we must look beyond the conventional ‘electricity sector’ in the future and instead look at the complete ‘energy system’ to identify solutions that can decarbonise our energy system in an affordable, efficient and sustainable manner. Author: David Connolly PhD is head of policy with the Irish Wind Energy Association References [1] M. Howley and M. Holland, Energy in Ireland 1990-2015. Sustainable Energy Authority of Ireland, 2016. [2] D. Connolly and B. V. Mathiesen, 'A technical and economic analysis of one potential pathway to a 100% renewable energy system,' International Journal of Sustainable Energy Planning and Management, vol. 1, pp. 7–28, 2014. [3] P. A. Sørensen, B. L. Paaske, L. H. Jacobsen, and M. Hofmeiseter, 'Udredning vedrørende varmelagringsteknologier og store varmepumper i fjernvarmesystemet,' The Danish Energy Agency, 2013. [4] H. Lund, P. A. Østergaard, D. Connolly, I. Ridjan, B. V. Mathiesen, F. Hvelplund, J. Z. Thellufsen, and P. Sorknæs, 'Energy Storage and Smart Energy Systems,' International Journal of Sustainable Energy Planning and Management, vol. 11, pp. 3–14, 2016.