Cost-Benefit Analysis of systems using heat from nuclear plants

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Nuclear hybrid systems

Section 2.1 highlights the diversity of nuclear hybrid systems while explaining the reasons that drove us to discard some of them. Sub-section 2.1.1 briefly depicts the worldwide literature on nuclear hybrid systems. Sub-section 2.1.2 and 2.1.3 then restrict the technological scope to PWR and discuss the possibility to produce hydrogen and to desalinate seawater with these reactors. Sub-section 2.1.4 finally presents the on-going discussion on small and modular PWR.

A great diversity of nuclear technologies and market applications

Nuclear hybrid energy systems are schemes designed to provide multiple services (e.g. electricity, heating, cooling, freshwater, synthetic fuels) with centralised nuclear facilities. The literature is considering a large range of technological options for nuclear hybrid energy systems, from Light Water Reactor (LWR) based designs to Generation IV reactor concepts. As shown in Figure 1.1, the range of potential application is equally diversified, depending on the supply temperature of nuclear reactors. Techno-economic aspects regarding non-electric applications of future nuclear technologies are discussed in e.g. Fütterer et al., 2014; IAEA, 2017a; Locatelli, 2013). Given that most nuclear reactors operating today in the world (277 out of 438) and tomorrow (59 out of 69 under construction; IAEA, 2017a) are PWR (the most conventional type of LWR), the largest amount of heat generated by nuclear plants towards 2050 will be PWR sourced. This is why this Ph.D. is limited to the study of heat generation with PWR. PWR can be safely designed and operated in CHP mode (STUK, 2009), as confirmed by at least 51 commercial experiences (IAEA, 2017b, 2003). PWR can also be dedicated to the sole production of heat (IAEA, 1997; Decentralized energy, 2017).

Hydrogen production with PWR

While being of great interest for future energy systems, nuclear plant based hydrogen production is not studied here since it does not require a large amount of heat and hence cannot be associated to the underlying Ph.D. concept. That is, increased efficiency achieved by using heat for non-electric applications. Besides, hydrogen production as a way to do load-following with nuclear plants has already been subject to in-depth investigations (see e.g. Cany, 2017; Mansilla et al., 2007; Orhan and Babu, 2015; Scamman and Newborough, 2016; Sorgulu and Dincer, 2017). In the context of the French energy system, such systems could allow further penetration of intermittent renewables while maintaining favourable economic conditions for nuclear plants (Cany et al., 2016).

Seawater desalination

Some EU countries (e.g. Spain, Italia, Greece) may suffer significant water scarcity issues by 2030 (IEEP (Institute for European Environmental Policy), 2008). The Water Exploitation Index (WEI, the mean annual total demand for freshwater divided by the long term average freshwater resources) of French (Rhône, Seine and Scheldt) and UK (Anglian, Humber and Themes) river basins could be comprised between 23.2% and 55.9% towards 2030 (IEEP, 2008). A WEI above 20 % implies that a water resource is under stress and values above 40 % indicate clearly unsustainable use of the water resource (EEA (European Environment Agency), 2009; citing Raskin et al., 1997). Even though it should increase, the energy demand for desalination in the EU will likely remain lower than the energy demand for space heating and domestic hot water. Worldwide, however, sea water desalination is one of the most promising nuclear non-electric market, and this because:
(i) Water scarcity issues are gaining importance;
(ii) Nuclear technologies can provide cost-effective desalination solutions (see e.g. Karagiannis and Soldatos, 2008; Misra, 2007; Nisan and Dardour, 2007). In particular, multi-effect distillation plants can be operated below 70°C, thus allowing the use of wasted heat or, in case of a CHP, minimising the electricity losses due to heat generation;
(iii) Desalination do not require heat continuously, facilitating the coupling with those thermal plants which aim to provide flexibility services to the power grid (Locatelli et al., 2017).
While this Ph.D. does not study this option in-depth, the deployment of nuclear plant based seawater desalination plants in the EU cannot be excluded. In a context of rising water scarcity issues, such an option deserve further investigations.

Small and Modular Reactors

Those Small and Modular Reactor (SMR) concepts which target non-electric applications can also be defined as nuclear hybrid systems. Among the four SMR market studies reviewed by Berthlémy et al. (2017; referring to Chénais et al., 2014; NEA, 2011; NNL (National Nuclear Laboratory), 2014; Uxc (Ux consulting company), 2013), three do see potential for CHP applications with LWR based SMR. Compared to large nuclear reactors, SMR may be advantageous to address cogeneration markets (see in Section 2.1 of Chapter 5 for further discussion); and this because:
(i) SMR may be easier to deploy close to urban areas thanks to high safety standards, thus limiting the major cost of building a heat transport pipeline (e.g. Kessides, 2012; Locatelli et al., 2015; Rowinski et al., 2015);
(ii) The smaller size of SMR matches with a wider range of heating needs;
(iii) If SMR are largely deployed in the future, they could benefit from positive learning by doing effects, so that the deployment time may be lower than larger reactors.
Overall, it is reasonable to say that the optimal size of a NCHP should be determined on a case by case basis. Questions which may help making a choice are e.g. ‘What is the size of the heat demand?’; ‘Is the building of SMR instead of larger reactors likely to allow the siting of nuclear units closer to consumption sites?; ‘Can we expect a shorter deployment time if building several SMR?’ Martin Leurent 19 Ph.D. Thesis – 2018 SMR could represent 1% to 20% of the total new built nuclear capacity towards 2035 (see Figure 1.2), and most of SMR projects are being planned out of the EU (Berthélemy et al., 2016). Stakeholders do not seem to think that SMR will have a major impact on the realization of the EU and French energy policy objectives towards 2050. This should nonetheless be considered with caution given that prospective studies often fail to foresee radical changes, which are unpredictable by nature.
Figure 1.2: Benchmarking of recent SMR market studies (2035 time horizon). Data source: Berthélemy et al. (2016).
For the same reasons as for large reactors (see 2.1.1), only LWR based SMR are considered in this Ph.D. The results presented in this Ph.D. are, to some extent, valid whatever the size of the PWR is. The modelling approach (simulation approach considering the marginal cost attributable to heat production with the nuclear plant) adopted could indeed be applied to SMR without modifications (see Section 3 for further explanations).

Heat applications of PWR in Europe

The Ph.D. investigates the potential of PWR (often referred simply as nuclear plants) to supply space heating and domestic hot water to residential and commercial buildings through DH networks, and to supply industrial plant factories (process heating only). Nuclear plants have already been supplying heat for commercial applications, at temperatures up to 250°C (Verfondern, 2013). This can be done without jeopardizing the reactor’s safety (STUK, 2009: p. 6). DH applications are investigated for 15 urban areas located in seven European countries (see Chapter 2), while industrial applications are studied within the French boundaries only (see Chapter 4). Overall, the Ph.D. mostly investigate DH supply. There are three reasons behind this choice:
(i) In Europe (including Russia, Ukraine and the UK), DH is the most tried-and-tested nuclear non-electric application, and it certainly has the highest potential in the short run. As depicted in Figure 1.3, space heating and domestic hot water demand in residential and commercial buildings represent the largest market for nuclear heat production in France (>100 TWhth; see Chapter 2). All together, the industrial plant factories identified as relevant to be supplied with nuclear heat require approximately 30 TWhth/a of heat below 250 °C (see Chapter 4). Besides, this amount (30 TWhth/a) considers the needs of all plant factories located in a 100km radius from a French nuclear site, while in reality only the closest factories could be cost-effectively supplied with nuclear units. While the creation of industrial symbiosis complexes based on nuclear plants does hold significant potential for cost and GHG emissions savings, it require optimal relocation of plant factories closer to nuclear sites to reach the full possibility (see Chapter 4). On the contrary, the geographic location of residential and commercial heat demand should remain relatively stable and a large part of this demand will remain attractive to DH markets for many decades (see Chapter 7). Given that the number of heating degree days is lower in France than in most of European countries (see Figure 1.3), it is reasonable to say that DH holds the largest potential for heat supply with nuclear plants overall Europe.
(ii) If the aim of operating a nuclear plant in a CHP mode is to increase the flexibility of the power production while maintaining reasonable load-factors, stakeholders may prefer DH, hydrogen or desalination applications (Locatelli et al., 2017). To be flexible, a NCHP might operate at full load during the night when the request of electricity is low, and be turned off during most of the daytime. This criterion discards all the applications that have high thermal inertia and/or do not allow daily load variations (with rather fast dynamics), which is the case of many industrial processes (see Chapter 4). On the contrary, DH + NCHP systems with sufficient storage capacity can fulfill the requirements for flexible power generation (Rämä, 2018). Industrial applications, if they do not suit to a business model in which the main service offered by nuclear plants are electricity generation and flexibility, do however open opportunities for smaller units following new business rules (see Chapters 4, 7 and 8);
(iii) The evaluation of systems coupling nuclear plants with industrial plant factories requires to collect many data. Information such as the size of the plant factories and the plants location together would give information on the ease of access. In addition, the viability of the project cannot be established unless industries provide details on planned and unplanned plant shutdowns. The information on source availability appears to be crucial to the design of industrial complexes based on nuclear plants. Data collection is however be difficult due to confidentiality issues. In the frame of this Ph.D., valuable data were obtained for France (thanks to ANCRE (French National Alliance for Energy Research Coordination), 2015; see Chapter 4), but no data were obtained for other European countries.
Figure 1.3: Climatological degree-days in Europe for the time period 1981-2000 with an effective indoor temperature of 17°C and a threshold temperature of 13°C. Data source: Frederiksen and Werner (2013).
Notes:
(*) HDD are a measure of how much (in degrees), and for how long (in days), the outside air temperature was below a certain level.
(**) The map is not representative of all locations in each country since the data grid consists only of 80 locations.

Residential and commercial applications of PWR in Europe

Section 2.3 aims to provide a comprehensive overview of the stakes specific to the European DH sector, as well as of the role played by nuclear plants in the supply of DH networks. Sub-section 2.3.1 first provides a state-of-the-art of DH systems in Europe. Sub-section 2.3.2 then presents the stakes surroundings DH systems in a context of increasing energy performance of buildings. Sub-section 2.3.3 exposes the previous and planned experiences of nuclear DH production. Sub-section 2.3.4 finally discusses the expansion of the cooling demand and the possibility to use the heat of nuclear plants to supply district cooling systems (using absorption cooling chillers).

State of DH systems in Europe and France

Energy consumption in residential and commercial buildings represents approximately 40% of the total energy produced in the EU, and is associated with 36% of the total EU’ CO2 emissions (European Parliament, 2010). Space heating and domestic hot water demand correspond to approximately 80% of the total energy consumed in these buildings (European Parliament, 2010). As detailed in Table 1.1, direct burning of fossil-fuels within on-site boilers represents 68% of the final energy used to provide EU heat loads, while DH accounts for 7% (EC, 2016b). The share of buildings served by DH nonetheless varies widely among countries (see Figure 1.5), from about 60% in Denmark down to 7% and 2% in France and the UK, respectively (IEA, 2014).
According to Frederiksen and Werner (2013), the fundamental idea of DH is ‘to use local fuel or heat ressources that would otherwise be wasted, in order to satisfy local customer demands for heating, by using a heat distribution network of pipes as a local market place’. In general, the DH systems within EU have been faithful to this concept, with only 17% (against 68% when considering all heating systems) of the heat demand supplied through the direct use of fossil-fuels within heat-only boilers (Werner, 2017; using data from IEA, 2015). The major DH heat sources in EU are shown in Figure 1.4, including the direct use of renewables, the use of renewables in CHP plants, and the use of fossil fuels in CHP plants. Future DH systems should further integrate CHP, renewable or excess heat sources, as promoted by the directive 2012/27/EC (European Parliament, 2012).
Figure 1.4: Heat supplied into all DH systems in the EU according to four heat supply methods, 2014.
Data source: Werner (2017); using data from IEA (2015).
Figure 1.5: Percentage of the population served by DH systems. Data source: EC (2016c), using data from Euroheat & Power (2015a).
In ‘DH learning countries’ such as France and the UK, DH expansion is encouraged by public authorities (AMORCE (French DH association), 2015; BuroHappold Engineering, 2016). The share of renewable or excess heat sources in the total DH deliveries to French networks increased from 7.9 TWhth/a in 2009 to 13.8 TWhth/a in 2017 (SNCU (French National Union for DH), 2017). This leap can be partly attributed to the public DH support set up by the government in 2009 (SNCU, 2017). The ‘Fonds Chaleur’ offers a financial contribution of about €5/MWhth to DH projects aiming to use more than 50% renewable or excess heat sources, provided that the linear heat density exceeds 1.5 MWhth⁄m. a (ADEME, 2017). However, ADEME (2017) emphasizes that the number of subsidized DH projects will have to more than double to achieve the French policy objectives. If the development trend of 2009-2017 is prolonged, renewable and excess DH deliveries should total 23 TWhth/a in 2030 (ADEME, 2017), yet the national 2030 objective is 39 TWhth/a (Assemblée nationale (French national assembly), 2015). The underlying requirement of such an ambitious target is the replacement of current heating equipments with DH systems. Local electricity and gas boilers supply 33% and 44% of French dwellings with heating and domestic hot water, respectively (AMORCE, 2015). Previous research have shown than direct heating is not the most efficient use of electricity (see e.g. Webb, 2015). Three main reasons can be advanced:
(i) Despite low initial investment, the levelised cost of heating buildings with electric heaters is 25 to 35% higher than with an average DH system (in a French average building, including all taxes; see AMORCE, 2015);
(ii) Using direct electric heaters increases the power load variations, and hence lead to larger volatility of electricity prices (in particular during the heating season). ADEME (2016) have shown that replacing direct electric heaters with heat pumps could reduce the French power consumption, leading in turn to lower electricity prices. A similar result can be expected when replacing electric heating with DH systems, which have a relatively low electricity consumption (see Chapters 2 and 3) and can adjust their consumption profiles thanks to water tank energy storages (Rämä, 2018).
(iii) The impact of electric heating on climate change is complex to assess. It relies on the CO2 content of electricity, which vary widely depending on hours, days and seasons. The average CO2 content of electricity in France is relatively low (62 kg CO2⁄MWhth, Ministère de l’environnement, de l’énergie et de la mer (French Ministry of the environment, energy and seas), 2017). Due to the high variation of the power load profile in the heating season however, the marginal power plants used to supply peak demand largely rely on fossil-fuels. These plants are either located in France or in a neighbouring country with interconnected grids (Olkkonen and Syri, 2016). Based on empirical data for 2003, ADEME and RTE (2007) showed that the direct and lifecycle CO2 emission of marginal power production in France was 560 kg eCO2/MWhe during peak periods. Extrapolating to 2030 based on the factor reduction trend followed by ADEME and RTE (2007) for 2010-2020, electric heaters in operation in 2030 would have a CO2 content of about 180-260 kg eCO2/MWhth. This is lower than lifecycle CO2 emissions from natural gas boilers (424 kg eCO2/MWhth; IPCC, 2006) but higher than DH based on renewable, NCHP or excess heat (50-150 kg eCO2/MWhth depending on the heating mix; see Chapter 3).

DH systems facing increased energy performance of buildings

Figure 1.6 summarizes the elements that are expected to affect the future competitiveness of DH systems. Significantly increasing the rate of renovating the aging building stock in the EU and providing high energy efficiency in new buildings is key to meeting EU climate targets (EC, 2012). In 2010, the annual space heating and domestic hot water consumption of EU buildings ranges from about 40 kWhth⁄m2. a (Cyprus) to 240 kWhth⁄m2. a (Finland, Latvia), with an average of approximatively 160 kWhth⁄m2. a (EEA, 2013). Nearly 40% of EU buildings were built before the 1960s and only 18% of them fulfill the strict energy performance requirements (Economidou et al., 2011). Following the Energy Performance Building Directive 2002/91/EC (European Parliament, 2003), the annual energy consumption of new buildings should be comprised between 34 and 125 kWhth⁄m2. a depending on countries. Given that the renovation rate of the existing building stock is about 1% per year however (Chirat and Denisart, 2016), most of the buildings that will be occupied in 2050 have already been built. Therefore, the specific heat demand (kWhth⁄m2. a) observed in average in EU countries should not be drastically diminished towards 2050. As further justified in Chapter 7, a reduction of 20-30% towards 2050 compare to 2008 is a realistic projection for France.
By reducing the annual heat consumed within a specific land area (GWhth⁄km2. a), building renovation should nonetheless lead to a decrease in the linear heat density (MWhth⁄m. a) of DH networks. The linear heat density indicates the length of DH pipelines required to connect all dwellings to the network, and thus strongly affects the cost of DH systems (Persson and Werner, 2011). Hence, the penetration of energy efficient buildings could reduce the competitiveness of future DH systems. This is an idea that often serve to minimise the interest of DH systems in future energy systems. However, the reality is more complex. Some papers address the reduction of heat demands in existing buildings and conclude that such an effort involves a significant investment cost (Zvingilaite, 2013). The Heat Roadmap Europe study illustrates how a least-cost energy efficiency solution can be reached for Europe, if energy conservation is combined with an expansion of DH (and cooling; Connolly et al., 2014). In the case of Denmark, Nielsen and Möller (2013) have shown that DH could be cost-effectively expanded by 1-12% even if the specific heat demand of buildings is reduced by 75%. Similarly, Reidhav and Werner (2008) highlight the profitability of DH systems in low density areas. Chapter 7 shows that the potential for DH expansion in France remains 9 times higher than current DH deliveries in a scenario that sees the heat demand of buildings uniformly decreased by 50% (national target towards 2050; Assemblée nationale, 2015).
If DH systems want to secure their economic advantages yet, they must be improved by changing fuels and minimising grid losses. The reduction of heating demands in existing buildings can be exploited by DH systems in several ways (Dalla Rosa and Christensen, 2011). Better insulation of buildings means that comfort is achieved by lower supply temperatures. Lower temperatures requirements in radiators can allow to reduce DH grid losses and pipe diameters (Averfalk and Werner, 2017). Since the implementation of the first schemes in the 1880’s, energy efficiency of distribution systems have increased, confirming the adaptation of DH systems to building standards (see Figures 1.7 and .8). In addition, supply temperatures below 80°C allow the use of plastic piping, which can be more cost effective than conventional DH metal based pipes (Schmidt et al., 2017). Plastic piping also have a longer statistical lifetime (see Figure 1.9). This concept, referred as 4th generation DH (Lund et al., 2014), also enable further integration of renewable and excess heat sources, as well as a higher efficiency of conventional production units. The DH literature however emphasizes numerous obstacles inhibiting the implementation of the 4th DH concept, in particular in existing DH systems (Rämä and Sipilä, 2017). Averfalk and Werner (2017) identify seven specific bottlenecks, including e.g. lack of individual metering systems (requiring apartment sub-stations), lack of systemic supervision of substations by DH utilities, short thermal lengths in sub-stations heat exchangers and customer radiator systems.

Table des matières

Chapter 1: Introduction
I. Cost-Benefit Analysis of systems using heat from nuclear plants
Chapter 2: Cost-benefit analysis of district heating systems using heat from nuclear plants in seven European countries
Chapter 3: Cost-benefit analysis of plausible heat decarbonisation pathways in the French urban area of Dunkirk
Chapter 4: Feasibility assessment of the use of steam sourced from nuclear plants for French factories considering spatial configuration
II. Analysis of Multi-Stakeholder Interactions in real projects
Chapter 5: Driving forces and obstacles to nuclear cogeneration in Europe: Lessons learnt from Finland
Chapter 6: A multicriteria approach to evaluating heating options in the French urban area of Dunkirk
III. In-Depth Analysis of the potential in France
Chapter 7: Prospective analysis of nuclear plant sourced heat utilisation in France
Chapter 8: Stimulating niche nurturing process for heat production with nuclear plants in France. A multi-level perspective
Chapter 9: Conclusion

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