Paper to be presented at the 35th DRUID Celebration Conference 2013, Barcelona, Spain, June 17-19 Understanding Eco-Innovation Evolution: A Patent Analysis in the Energy Field Vito Albino Politecnico di Bari Department of Mechanics, Mathematics and Management v.albino@poliba.it Lorenzo Ardito Politecnico di Bari Department of Mechanics, Mathematics and Management l.ardito@poliba.it Rosa Maria Dangelico "Sapienza" Università di Roma Department of Computer, Control and Management Engineering rosamaria.dangelico@uniroma1.it Antonio Messeni Petruzzelli Politecnico di Bari Department of Mechanics, Mathematics and Management a.messeni.petruzzelli@poliba.it Abstract Eco-innovations are being recognized as fundamental means to foster sustainable development, as well as to create new business opportunities. Nowadays, the eco-innovation concept is gaining ground within both academic and practitioner studies, with the attempt to better understand the main dynamics underlying its nature and guide policy makers and companies in supporting their development. This paper contributes to extant literature on eco-innovation by providing a comprehensive and unique overview of the evolution of a specific type of eco-innovations that are playing a crucial role in the current socio-economic agenda, namely low-carbon energy technologies. Specifically, we focus our attention on the patenting activity of different countries and organizations over time, as well as on related policy initiatives. Accordingly, we collected 131,801 patents granted at the United States Patent and Trademark Office (U.S.PTO) from 1946 to 2010, and belonging to the ?Nuclear power generation?, ?Alternative energy production?, and ?Energy conservation? technological classes, as indicated by the International Patent Classification (IPC) Green Inventory. Our findings report patterns of distribution of low-carbon energy technologies? evolution, as well as major related environmental programs explaining the evolutionary trends, hence revealing how different events and needs have influenced these eco-innovations? development. Jelcodes:O33,- Understanding Eco-Innovation Evolution: A Patent Analysis in the Energy Field Abstract: Eco-innovations are being recognized as fundamental means to foster sustainable development, as well as to create new business opportunities. Nowadays, the eco-innovation concept is gaining ground within both academic and practitioner studies, with the attempt to better understand the main dynamics underlying their nature and guide policy makers and companies in supporting their development. This paper contributes to extant literature on eco-innovation by providing a comprehensive and unique overview of the evolution of a specific type of eco-innovations that are playing a crucial role in the current socio-economic agenda, namely low-carbon energy technologies. Specifically, we focus our attention on the patenting activity of different countries and organizations over time, as well as on related policy initiatives. Accordingly, we collected 131.801 patents granted at the United States Patent and Trademark Office (U.S.PTO) from 1946 to 2010, and belonging to the “Nuclear power generation”, “Alternative energy production”, and “Energy conservation” technological areas, as indicated by the International Patent Classification (IPC) Green Inventory. Our findings report patterns of distribution of low-carbon energy technologies’ evolution, as well as major related environmental programs explaining the evolutionary trends, hence revealing how different events and needs have influenced these eco-innovations’ development. Keywords: Eco-innovation; patents; low-carbon energy technologies; environmental sustainability; environmental programs. 1. Introduction During the last years, the concept of eco-innovation has attracted an increasing attention across many countries all over the World as a means to address both economic and environmental priorities. Since the Brundtland Report (WCED, 1987), where the concept of sustainable development was first presented, an increasingly demand for a new vision on innovation was claimed (Rennings, 2000; OECD, 2012). In addition, following the Brundtland Report, environmental protection should not be considered as a limit to the economic growth, but rather as a necessary condition for a long term development. Furthermore, technology is deemed as the basis of the economic growth, providing the means to act smarter and more sustainably (WCED, 1987; European Commission, 2009; McJeon, 2011). Thereby, technology seems to play a strategic role by influencing environmental impacts, risks, and costs (Kotha and Orne, 1989; Shrivastava, 1995; UNEP, 2003). Accordingly, international organizations, such as the Organisation for Economic Cooperation and Development (OECD) and the United Nations, have recently introduced programs to deeply study the eco-innovations’ development. For instance, in 2008 the OECD launched the “Green Growth and Eco-innovation” project, with the aim to better understand how innovation can result into new technological and systemic solutions for facing global challenges and leading the industrial system towards a sustainable growth (OECD, 2008, 2009b, 2012). In this paper, we aim at studying the evolutionary trend of a specific type of eco-innovation, which has been demonstrated to play a key role in fostering sustainable development and business innovation (Sun et al., 2008), namely low-carbon energy technologies. Nowadays, these technologies are recognized as a fundamental means to reduce the cost of stabilizing atmospheric carbon dioxide concentrations and lower the final cost of meeting environmental policy objectives (McJeon, 2011; IEA, 2012), as well as to improve energy security, emission reduction, environmental protection, and economic growth (Nuttall and Manz, 2008; Harmon and Cowan, 2009; Palma and Coletta, 2011). In this context, while several scholars have devoted their attention to define, classify, and measure eco-innovations (e.g., Demirel and Kesidou, 2011; Kesidou and Demirel, 2012; Horbach et al., 2012), to our knowledge, a complete picture of the eco-innovative efforts undertaken by both companies and countries over time is still lacking. Thereby, this paper aims at developing a comprehensive overview of the low-carbon energy technologies’ evolution. To this aim, we contribute to the extant literature by building a unique database of 131,801 patents granted at the U.S.PTO from 1946 to 2010 and belonging to the green technological areas “Nuclear power generation”, “Alternative energy production”, and “Energy conservation”, as described by the IPC Green Inventory classification. For each patent, we retrieve several data, such as assignees and inventors details, technological classes, backward citations, scientific references, and forward citations. Then, we present an overview of patents’ development trend and identify the countries and organizations mainly engaged in these innovative activities, as well as describe the most relevant actions undertaken by both private and public organizations in the eco-innovation evolution process. Finally, we provide some insights on the most valuable patented inventions in the field. The paper is structured as follows. In the next section, we discuss the use of patents data as proxy for analyzing technology development and present a brief literature review on eco-innovation. Then, the third section presents the data collection methodology and the sample. The fourth section contains descriptive analyses on the patenting activity, and possible explanations for these results. Finally, discussion, implications, and conclusion are presented. 2. Theoretical Background 2.1. Patents as measure of innovation Innovation indicators can be divided into two categories, namely input-based indicators and output-based indicators (Rogers, 1998; Hagerdoon and Cloodt, 2003; Dangelico et al. 2010). The former refers to those measures that look at the inputs of innovation processes, such as research and development (R&D) expenditures. They have been widely used as a valuable proxy to assess innovation activity efforts. Nevertheless, these data are available only for specific industries or general applications, and have not a direct relationship with the innovation outcomes (Evangelista et al., 1998). Consequently, output-based indicators, which take into account the results of innovation activities, such as patents and new product introductions, have emerged as a valuable source of information for studying innovative dynamics. Particularly, patent data have much attracted both researchers and practitioners (Griliches, 1990). Patents gained much consensus due to a close (if not perfect) link to economic relevant inventions (Dernis and Kahn 2004), as well as have been recognized as strongly correlated with other indicators of innovative activity, such as R&D expenditures and new product introductions (e.g., Comanor and Scherer, 1969; Griliches, 1990; Hagedoorn and Cloodt, 2003). Furthermore, patent data are publicly available for a long time series and provide a number of valuable information on the technological content, geographical location of assignees and inventors, and citations made and received by the patent. Thereby, academics and policymakers have made an increasing use of patent data as source of information for analyzing innovations development over time, countries’ technological capabilities, relationship between polices and technological innovation, and pace of technological development and diffusion (e.g., Griliches, 1990; Jaffe et al., 1993; Jaffe and Stavin, 1995; Archibugi and Pianta, 1996; Meyer, 2002; Popp, 2006; Abraham and Morita, 2009; Kayal, 2009; OECD, 2009b; Oltra et al., 2010). In addition, citations received by a patent have been widely adopted to account for innovation value, hence allowing scholars to recognize breakthrough or radical innovations (Trajtenberg, 1990; Harhoff et al., 1999; Hall et al., 2001; 2005; Gambardella et al., 2008), which represent the basis of new technological trajectories and paradigms, as well the main sources of nations and firms’ competitive advantage (Trajtenberg, 1990; Harhoff et al., 1999). Nevertheless, the use of patents is not straightforward. In fact, not all inventions are patented or patentable, companies in different countries or sectors may put different value in patenting activity, and patents do not account for the overall impact of the inventions (Pavitt, 1985; Archibugi and Pianta, 1996; Hall et al., 2001). However, despite these drawbacks, patents are still considered the best available source of data to study innovation dynamics (Griliches, 1990; Hirschey and Richardson, 2001; Abraham and Morita, 2009). 2.2. Defining eco-innovation The big global challenges posed by the growth rate of the human-induced climate change, as well as the sustainability goals recently set, such as Europa2020 targets (European Commission, 2010), have led to the need to redefine the concept of innovation (Rennings, 2000; OECD, 2012). In fact, the term “innovation” is generally referred to the implementation of a wide range of new products, processes, or organizational methods (OECD, 2005) without focusing on the related environmental impacts. Differently, sustainability issues aim at boosting innovative activities towards sustainability objectives (Rennings, 2000; OECD, 2011). Indeed, despite it has been widely recognized that innovation is the central issue in economic prosperity (Hargroves, 2005), nowadays innovation is considered as the key factor to pursue sustainable development targets while continuing to promote competitiveness as well (Nidumolu et al., 2009; OECD, 2010, 2011). Accordingly, the concept of eco-innovation has rapidly gained much attention across both policy makers and researchers. In the literature, different definitions of eco-innovation have been proposed and different terms have been adopted interchangeably (e.g., eco, green, environmental, or eco-friendly innovation). Nevertheless, despite a wide range of different definitions, some common features emerge, highlighting that an eco-innovation is an innovation that primarily contributes to reduce environmental impacts and opens new sustainable pathways in the market (Fussler and James, 1996; Klemmer, 1999; Andersen, 2008; Arundel and Kemp, 2009; OECD, 2009a; European Commission and EACI, 2011). In particular, several debates on eco-innovation have focused on topics that directly address environmental technologies (European Commission, 2004; Stern, 2007), recognized as the keys to guarantee the co-existence of economic growth and environmental progress (Shrivastava, 1995; OECD, 2000). Specifically, technologies aimed at reducing Greenhouse Gas (GHG) emissions and energy consumption, as well as technologies devoted to restructure the global energy system (e.g., solar cells, electric engines) have been deemed to play a crucial role in fostering sustainable development and business innovation (e.g., Sun et al., 2008; Messeni Petruzzelli et al., 2011). Accordingly, in this paper we analyze a specific type of eco-innovation, namely low-carbon energy technologies. 2.3. Patents as measure of eco-innovation In the literature, there are many examples of using patent data to study eco-innovation due to the opportunity of identifying technologies developed in a specific technological field (OECD, 2008; Oltra et al., 2010). For instance, Pilkington et al. (2002) used a sample of 268 U.S. patents in the IPC class “Electric propulsion with power supplied within the vehicle” (IPC code B60L/11) in order to analyze the development of the electric vehicle. Brunnermeier and Cohen (2003) provided evidences on the increased development of ecoinnovations by U.S. manufacturing firms, as reflected by patent count, in response to the increment in pollution abatement expenditures, especially in internationally competitive industries. Sun et al. (2008) analyzed the temporal and spatial distribution of eco-patents in China. In particular, the authors found that the development of environmental technologies is particularly relevant in the East of China, where they have shown an increasing application of new patents, although still lagging in a global perspective. In addition, Oltra and Saint Jean (2009) used patent applications in order to understand the competition among companies in the development of engine technologies for low emission vehicles. The OECD (2011) included patent data in its study to analyze environmental technologies’ diffusion and transfer. Finally, Leu et al. (2012) studied the patenting activity in the field of bio-fuel and bio-hydrogen energy from 2000 to 2011 through the use of patent bibliometric analysis. These studies, however, offer a partial scenario to policy makers and companies in explaining the dynamics underlying eco-innovation evolution. Principally, they relate to a small sample of patents, which could be not so relevant to bring out significant results. Furthermore, they refer to a bounded geographic area or a limited time period, which cannot allow to depict a complete scenario of innovative efforts in eco-innovations’ development. Finally, most studies focus their attention to a specific sector or technological class, so limiting the generalizability of their outcomes. Our paper extends previous studies through the creation of a wide and unique database that collects all patents related to eco-innovation activities in the energy field, by including all the main technological energy-related categories and their subclasses. Hence, this allows us to more deeply analyze the differences across various types of eco-innovation. In addition, our database collects patents filed from 1946 to 2010, hence giving us the possibility to trace the entire history of eco-innovation’s development in the energy field starting from its origin. Furthermore, the considered patents are granted to organizations spread all over the World, hence making us able to capture differences among countries and organizations’ eco-innovative capabilities. Finally, we also offer a nuanced picture of breakthrough eco-innovations in the energy field. 3. Data and Methodology We employ patent data to investigate the main dynamics characterizing the development of eco-innovations, as well as their breakthrough nature. Differently from previous studies, we refer to the IPC Green Inventory in order to collect patented technologies providing environmental benefits, rather than other less rigorous approaches such as those based on keywords (Oltra and Saint James, 2009; Leu et al., 2012), which suffer from the drawbacks that the main concept may be unrelated to the selected keywords or that a particularly relevant text may not contain the key words being searched, and those based on the choice of some selected technological classes (Pilkington et al., 2002) instead of a common accepted classification. The IPC Green Inventory was launched in 2008 by the World Intellectual Property Organization (WIPO) to create a concordance between the IPC classification and Environmentally Sound Technologies (ESTs), as defined in Chapter 34 of Agenda 21. Accordingly, the IPC Green Inventory takes into account seven different technological classes, in turn divided into hierarchical sets of subclasses. Each subclass is linked with the most relevant IPC code(s), as identified by a panel of experts 1. In particular, we focused on the categories related to the energy field, namely, “Nuclear power generation”, “Alternative energy production”, and “Energy conservation”. This approach allows us to rely upon consistent and rigorous criteria to identify low-carbon energy patents and provides a large sample upon which conducting our analyses. Then, we searched for patents granted at the U.S.PTO. and belonging to the selected technological classes. Thus, we identified 131,809 patents granted from 1946 to 2010. For each patent, we collected relevant data, such as title, filing date, issue date, number of claims, number of backward, forward and scientific citations, inventors and assignees’ details (name, city, state, and country), and technological fields. To identify breakthrough eco-innovations we used patent forward citations, which have been widely adopted in the literature to assess innovation value and impact (e.g., Trajtenberg, 1990; Harhoff et al., 1999; Hall and Trajenberg, 2000; Hall et al., 2005; Gambardella et al., 2008). Indeed, patent citations are largely employed to evaluate differences in patent quality, especially in large datasets where in-depth qualitative evaluations of individual patents are very hardly (NREL, 2011). Nevertheless, the literature has questioned the use of forward citations, by noticing that older patents are more likely to be cited than younger ones (e.g., Hall et al., 2001), hence calling for solutions to avoid such a bias. Accordingly, we calculated the citation rate per year in order to remove the effects of respectively patent age. Furthermore, comparing the samples sorted by citation rate and number of forward citations (top 1, 3, and 5 percent of our sample), we found at least in the 90% of cases the same patents for each category, hence increasing our confidence in the selection criteria. 1 See http://www.wipo.int/classifications/ipc/en/est/ Hence, we considered highly cited patents as breakthrough technological innovations (e.g.,Ahuja and Lampert, 2001; Phene et al., 2006; Singh and Fleming, 2010). 4. Analysis and Results In this section, we provide a comprehensive overview of eco-innovation evolution in each technological category, by focusing on the development trends of patented low-carbon energy technologies. Specifically, we used patent count as a measure of the innovative effort (Zoltan et al., 2002; Singh, 2008), the average number of scientific citations to approximate the willingness of inventors to build upon science (e.g., Narin et al., 1997; Meyer, 2000; Callaert et al., 2006; Czarnitzki et al., 2011), the number of forward citations as a proxy of the quality and subsequent impact of an invention (e.g., Trajtenberg, 1990; Harhoff et al., 1999; Hall and Trajenberg, 2000; Hall et al., 2005; Gambardella et al., 2008), the main assignee information to analyze development trends at organization level, and, finally, the main inventor state in order to proxy the geographical origin of an invention (Sharif, 1986; Deyle and Grupp, 2005). As time scale, we used the filing year, since it captures the invention development period better than the issue year (Verspagen and Loo, 1999). However, the time lag between application and issue may be even large. Hence, patents filed more recently generally have less likelihood to be granted at the time of data retrieval. Thus, the last ten year analysis is used more for comparison than for an actual trend evolution analysis. Finally, we also referred to major environmental programs and geopolitical circumstances in order to better understand evolutionary trends of low-carbon energy technologies as a result of national and international policies, as well as to highlight historical events and private sector initiatives that may have fostered such innovations. 4.1. Nuclear power generation This main class is divided into two different subclasses, namely “Nuclear engineering” and “Gas turbine power plants using heat source of nuclear origin”. However, the latter has only a negligible contribution in explaining the nuclear energy eco-innovations’ evolution, as revealed by the low share of patents (0.3% of the total amount in the field). Thereby, we will analyze “Nuclear power generation” technologies without differentiating the two subclasses. Figure 1 presents the patenting application activity since 1946, as measured by patent count per year, both globally and per different geographical regions (U.S., Europe, Japan, and BRIC - Brazil, Russia, India, and China). The global trend (indicated by “ALL”) shows a sharp growth of the number of patents in the 1970s. Furthermore, almost all the analyzed countries contribute in the “Nuclear power generation” technological development in its first coming, except for BRIC. This trend could be explained by examining geopolitical issues occurred in those years. In fact, while nuclear energy and nuclear weapons technologies were closely related to military aspirations during World War II, since mid-1950s some governments started to reorient countries’ resources towards the development of nuclear power plants for commercial purposes. Thus, such commercialization efforts pushed organizations in protecting their inventions to gain greater profits. In addition, in 1967 the Arab-Israeli War (also known as Kippur War) caused a serious petrol crisis, when the Organization of Arab Petroleum Exporting Countries (OAPEC) proclaimed an oil embargo. Thereby, Western countries increased their investments in nuclear power, in order to face such a energy crisis (Anadòn, 2012). A number of reactors, in fact, became operational all over the World. To name few examples, in 1971 diverse commercial nuclear power plants were in full operation in the U.S.. In Kazakhstan, the world’s first commercial prototype fast neutron reactor (the BN-350) started up in 1972. Also European countries, such as France, Italy, Germany, and UK saw the birth of many reactors in those years. Particularly relevant was the action took in place by the French Prime Minister Pierre Messmer in 1974, when he declared the so named “Messmer Plan”' with the aim of generating from nuclear power the whole France’s electricity need (Sovacool et al., 2012). Figure 1 Trend of “Nuclear power generation” patent applications. Furthermore, the graph depicts an alternate patenting activity trend across the countries during the period from 1976 to the mid-1990s. Particularly, it reflects that patenting activity in Europe fell down immediately after 1988, whereas it grows in the U.S. and especially in Japan, which assumed a predominant innovative role in this field. Explanations may be identified in a number of different reasons that caused some concerns in the use of nuclear power, such as the reduction of the oil price in the early 1980s and some nuclear accidents, like the Three Mile Island incident in Pennsylvania in 1979 and the well-known Cernobyl disaster in 1986. Nevertheless, at global level the effects produced were not the same. In fact, while some countries drastically reduced their attention towards nuclear power and R&D efforts in the field, others continued to invest. For instance, despite Italy accounted for several reactors, nuclear energy was totally abolished by a public referendum in 1987. Moreover, at the end of 1989 the UK government stopped the build of nuclear stations, and in August 1986 Germany approved a resolution to abandon nuclear power within ten years. Differently, other nations still promoted nuclear energy. Indeed, the project International Thermonuclear Experimental Reactor (ITER) represents an important signal in that direction. ITER was a research and engineering project signed in 1985 by Soviet Union, the U.S., Japan, and the European Union and launched in 1988 with the aim to have a full scale production of electricity from power plants. Finally, Figure 1 depicts another increase in patenting activity starting from 1996, which seems to highlight a renewed interest in the nuclear power in Europe, Japan, and some other countries (e.g., South Korea and Israel). This probably finds its roots in the rise of developing economies that started investments in that direction. Indeed, that period is recognized as “nuclear renaissance” just because of a new interest in the nuclear power industry driven by the rising of fossil fuel prices and environmental concerns (Nuttall, 2005). Thereby, despite some incidents happened around the World, a third generation of reactor was developed during these years. The first of such reactors was commissioned in Japan (World Nuclear Association, 2009). In addition, in 1999, in the U.S. the Nuclear Energy Research Initiative (NERI) was established in order to foster collaborative researches in high technological nuclear solutions. More recently, other countries started nuclear energy programs, such as China, South Korea, and India that, joined the ITER project. Finally, several states, particularly from Africa, are currently carrying on nuclear power programs in this “nuclear renaissance” scenario, mainly pushed by the abundant uranium resources IAEA (2005). In Figure 2, we examined the global patent share across countries by trying to highlight the other relevant contributors. As noted in the previous graph, the three main actors are the U.S., Japan, and European countries. Within European countries, France and Germany are the most innovative. Looking for other contributors, we checked for the BRIC innovative efforts, due to their significance in the current and future economic scenario. However, the analysis points out that they are still not so relevant in R&D activities in this specific field. Finally, we highlighted two other important actors, namely Korea and Israel. While it is reasonable that South Korea may be involved in developing nuclear technologies due to its entry in the ITER project, Israel has no nuclear power plants, hence making these technologies originating from researches conducted in the military field. Figure 2 “Nuclear power generation” eco-innovation patent share by geographical area. Figure 3 “Nuclear power generation” scientific citations analysis. By analyzing the citations’ rate of scientific documents made by all patents, it turned out an interesting aspect of the innovation activity. Specifically, by looking at the graph shown in Figure 3, where the y-axis reports the average number of scientific citations made by all patents in a specific year, it is possible to note that, before 2002, inventors tend to cite only patent documents. Differently, in recent years, references made to scientific literature have grown. Thus, it is possible to observe how from 2002 organizations have changed their approach in research activities, shifting to a closer relationship between theoretical and applied research than in the past. In turn, this may depends on the strengthening of the link occurring between science and technology. This is in according to previous studies that highlight the positive influence of basic science for economic growth (Jaffe 1989; Adams, 1990) and new technologies’ development (Narin et al., 1997). Main reasons have been recognized in the key role of science in fostering technological advances by providing new technological ideas (Brooks, 1994), and by expanding firms’ absorptive capacity (Cockburn and Henderson, 1998). In particular, looking at nuclear technologies, this linkage could be referred to the need of new materials and chemical processes that can meet safety and efficiency goals. Thus, basic research on materials science, chemistry and physics provides significant opportunities that may have broad impacts on nuclear power future (U.S. Department of Energy, 2006). Figure 4 reveals the top 10 organizations in terms of number of granted patents, operating both in public and into private sectors. Each bubble identifies an organization and its dimension represents the number of patents successfully filed by the organization. Moreover, in each bubble is inserted the flag of the country where the organization is located. In addition, other two measures were employed to enrich the analyses. In particular, the first one (x-axis) aims at indicating in which period an organization has undertaken the major efforts in developing nuclear technologies. Thus, we calculated the average year in which each company has filed its patents. The second one (y-axis), instead represents the quality of the inventive efforts as measured through the average number of forward citations in order to estimate the impact of organizations’ innovations. Results point out two main aspects. First, as we mentioned earlier in the paragraph, public sector, mainly represented by the U.S. government and the Commissariat à l'énergie atomique, has a significant role in supporting and pushing these types of power generation method. The effort devoted by public organizations is largely focused in the first period of nuclear power commercial use, whereas later in time private companies have assumed a major role. This trend confirms the importance of public research in exploring innovative technological solutions, hence opening the doors towards their subsequent exploitation by the private industrial sector (e.g., Griliches, 1979; Adams, 1990; Mansfiled, 1991; Rosenberg and Nelson, 1994; Cohen et al., 2002; OECD, 2007). Second, high valuable patents are mainly owned by actors located in the U.S. and their innovative activity is concentrated before the 1990s, whereas after this cut-off point (maybe related to the Cernobyl accident) the development of nuclear solutions is quite homogeneous across Europe, U.S., and Japan, while the innovative quality and impact seem to decrease. Figure 4 Top 10 organizations in “Nuclear power generation” class with the highest patent intensity, as represented by the bubbles, and related period of the highest patenting activity (x-axis) and outcome quality (y-axis). Then, we also showed the temporal period when breakthrough eco-innovations in the “Nuclear power generation” class were filed, and their geographical distribution. Specifically, Figures 5a shows that high valuable innovations are owned almost totally by the U.S. and European countries, being these pioneers in the adoption nuclear plants for commercial purposes. Furthermore, Figure 5b reveals that breakthrough ecoinnovations were mainly filed between 1970 and 1976, hence showing a reduction of the innovation value after this period. A possible explanation may be related on the necessity to make previous solutions safer rather than develop really new ones. Indeed, organizations tended to be more focused on the exploitation of existing technological solutions in order to extend life and reliability of current reactors, enable nuclear energy to meet climate change goals, develop sustainable nuclear fuel cycles, and manage nuclear waste (INERI, 2011). Figure 5a “Nuclear power generation” breakthrough eco-innovation patent share by geographical area. Figure 5b “Nuclear power generation” breakthrough ecoinnovation’s development trend. 4.2. Alternative energy production “Alternative energy production” class comprehends 13 subclasses. Firstly, we present the patenting activity as a whole without discerning the different categories. Then, we provide a brief analysis for each subclass. As shown in Figure 6, the global patenting activity (indicated by “ALL”) in the alternative energy field presents three clear different trends. It grew in the early 1970s. Then, it shows a slow decrease till the end of 1980s, after which a still growing trend is visible. As we noted in paragraph 4.1, the initial growing trend could be explained by considering the oil price shock triggered by OAPEC oil embargo that contributed to create awareness about the limits of global resources in respect of energy. Indeed, this concern attracted funds and concerted efforts for the development of new solutions through which untapped renewable resources may be harnessed on a large scale to partially replace the use of fossil fuels. The R&D expenditures for renewable resources were, in fact, equal to $65 million in 1974, while they reached a peak of about $2 billion in 1980 (Sellers, 2004). In addition, Figure 6 depicts a common trend for each country under analysis. Figure 6 Trend of “Alternative energy production” patent applications. Nevertheless, the enthusiasm towards renewable energy went on through the mid-1980s, but after the oil prices fall, a season of stagnation lasted for almost two decades. As a result, R&D efforts collapsed to less than a third by 1987 (Sellers, 2004). Furthermore, as we also showed in paragraph 4.1, the period from the mid-1980s to mid-1990s saw the pursuit of the investments made in nuclear power (Jacobson and Johnson, 2000). Thereby, especially in the U.S., which more than other countries suffered from the oil embargo, after the Kippur war (1973), the innovative efforts towards alternative energy solutions drastically decreases. Finally, the increasing trend characterizing the last two decades can be reasonable explained by the perceived growing economic opportunities and the rising attention on climate change, as well as the scarcity of crude oil in the West countries. Indeed, several actions were made by different countries and organizations. For example, in 1988, the United Nations established the International Panel on Climate Change in order to assess the scientific, technical, and socio-economic information for understanding the risk of human-induced climate change. Moreover, following what emerged during the United Nations Conference on the Human Environment (1972) about global environmental problems, several conferences took place in order to address the problem of sustainable development and foster new innovative efforts regarding the improvement and renewal of national energy systems as well. To name some examples, the United Nations Conference on Environment and Development (1992)addressed issues related to environmental, social and economic sustainability. Particularly, as an outcome of the conference, it was signed the Agenda 21, which highlighted the relevance of conservation and management of resources, as well as the importance of using and diffusing technologies with good environmental performances in several sectors, especially referring to energy issues. More recently, the Johannesburg Declaration on Health and Sustainable Development (2002) stressed over the concept of sustainable development and particularly aimed at triggering actions to access “[…] to reliable, affordable, economically viable, socially acceptable and environmentally sound energy services and resources, taking into account national specificities and circumstances” (UN, 2002 p. 11). Other international treaties, such as the Maastricht Treaty (signed in 1992), with the attempt to promote stable growth while protecting the environment, the Amsterdam Treaty signed (in 1997), and the ratification of the well-known Kyoto Protocol in 1997, further set the basis for a change in the energy system. Figure 7 “Alternative energy production” patent share by geographical area. Figure 8 “Alternative energy production” scientific citations analysis. Figure 7 shows the leading countries in patenting alternative energy technologies. It emerges that the U.S., Europe, and Japan represent the most innovative countries. Differently, BRIC are not among the top patenting countries, despite they strongly rely on clean energy (Lewis, 2007; Levi, 2010). This may suggest that those countries mainly adopt technology transfer systems, such as the Clean Development Mechanism defined in the Kyoto Protocol, and knowledge spillovers from developed countries to adopt alternative energy technological solutions, rather than being directly engaged in their creation (Koefoed and Buckley, 2008; Schneider et al., 2008). As made before, Figure 8 aims at showing the linkage between basic and applied research. The graph depicts that, before 1991, patent references are mostly directed to patent documents. Differently, later on a high propensity in citing also scientific publications emerges. This is in according to some actions taken place starting from that period. For instance, since the early 1990s the Department of Energy fostered basic research in the energy field in order to enhance technological development (EIA, 1998). Moreover, starting from the same years, the Framework Programme for Research and Technological Development, created by the European Union, funded projects in order to support and encourage research and technological development in the energy field. More recently, the International Science Panel on Renewable Energies and the Energy Innovation Hubs were established in order to integrate research centers that combine basic and applied research and provide analysis and strategic guidance for renewable energy R&D efforts worldwide. Figure 9 Top 10 organizations in “Alternative energy production” class with the highest patent intensity, as represented by the bubble dimension, and related period of the highest patenting activity (x-axis) and outcome quality (y-axis). Following the same criteria used in the previous paragraph, we examined the top 10 assignees by looking at the number of granted patents (see Figure 9). Firstly, the chart shows that, despite governments foster ecoinnovative actions, no national institution seems to strongly affect the patenting activity in this class. Secondly, companies have mainly produced high cited patents at the beginning of the development phase, despite later a greater amount of technological solutions has been patented. Explanations may depend on the fact that nowadays companies are exploiting established technologies instead of developing new ones. Finally, the figure also reveals that the University of California appears among the top ten organizations, hence confirming the importance of relationships between universities and companies (e.g., Saxenian, 1994; Audretsch et al., 2005; Messeni Petruzzelli, 2011). Figures 10a and 10b present where and when breakthrough eco-innovations have been developed, respectively. The former highlights that innovative efforts made in the U.S. figured out as the most relevant. The latter confirms that the most valuable patents were filed between 1973 and 1979, which is the first stage of the technology’s development. Figure 10a “Alternative energy” breakthrough ecoinnovation patent share. Figure 10b “Alternative energy” breakthrough innovation’s development trend. We extended the analysis of “Alternative energy production” technologies by considering their specific subclasses. Specifically, we divided them into two different categories by distinguishing the term “renewable” from the wider “alternative”. Accordingly, we referred to renewable energy innovations as those that rely on resources that can be totally replaced or are always naturally available, as well as are practically inexhaustible (Gicquel, 2011), as sunlight, wind, water, and geothermal heat. Differently, we considered non-renewable energy innovations as those solutions that allow the production of energy without the undesirable consequences of the burning of fossil fuels, but still require physical and chemical processes. Tables 4a and 4b show the different subclasses of renewable and non-renewable energy technologies, respectively, and the related innovative activity for each of them, both globally and within different geographic areas. Looking at Table 1a, it is worthy of note that renewable energy technologies only account for the 26,14% of all inventions and that the 18% of them is related to solar energy technologies. Furthermore, analyses depict that each country contributes in a similar way to the development of these innovations. Indeed, for each subclass, the U.S., Europe, and Japan are the leading innovative countries, while a scant contribution is provided by BRIC, Taiwan, Australia, and South Korea. Table 1b points out the relevance in the “Alternative energy production” technology portfolio of bio-fuel technologies, which represent almost the 46,73% of the overall eco-innovations. Probably, this is due to the need of replacing fossil fuels with solutions that do not suffer from the number of limitations linked to the production of energy by renewable sources, such as the variability of energy supply (Masini and Menichetti, 2012) and the high level of investments required (Painuly, 2001). In addition, innovative efforts’ distribution across countries is similar to that seen in Table 1a except for “OPoUH”, “Fuel cells”, and “Geothermal energy” classes, where Japan is more innovative than Europe. This could be explained by comparing the geological conditions of the two regions. In fact, most active geothermal resources are usually found along major plate boundaries where earthquakes and volcanoes are concentrated. Usually, this area encircles the Pacific Ocean (Glassley, 2010). Thus, Japan is actually a better candidate for this solution. Moreover, the high development of fuel cells technologies was triggered by a government funded demonstration project together with multiple manufacturers, such as Panasonic, Toshiba, and Eneos, which dedicated to supply the commercial market installing over 5000 residential fuel cell systems to provide heat and power in homes. Nowadays, in fact, thousands of residential fuel cell systems are being sold in Japan (IPHE, 2010). Table 1a Total patent share and percentage of patents owned by country for “renewable” technologies. RENEWABLE TECHNOLOGIES Patent share US JP EU BRIC TAIWAN AUS KOR OTHERS Total by geographical area Hydro energy 4,23 55,38 14,09 23,53 0,42 1,44 0,73 1,65 2,75 100 Ocean Thermal Energy Conversion (OTEC) 0,09 82,93 2,44 13,41 0 0 0 0 1,22 100 Wind energy 2,23 62,16 4,72 26,51 0,7 2,28 0,84 0,89 1,89 100 Solar energy 18,26 63,68 14,49 15,04 0,23 1,92 0,95 1,6 2,08 100 Geothermal energy 1,33 72,7 11,04 8,26 0,35 2,35 1,74 0,87 2,70 100 Total 26,14 Table 1b Total patent share and percentage of patents owned by country for “non-renewable” technologies. NONRENEWABLETECHNOLOGI ES Paten t share Bio-fuels 46,73 Integrated Gasification Combined Cycle (IGCC) 0,23 Fuel cells 9,61 Pyrolysis or gasification of biomass Harnessing energy from manmade waste Other Production or Use of Heat (OPoUH) 2,37 11,13 0,58 US 57,2 3 62,0 9 55,2 7 60,2 8 65,7 7 52,3 8 JP EU BRIC TAIWAN AU S KOR OTHERS Total by geographic al area 7,57 29,74 0,36 0,30 1,6 4 0,5 2,66 100 9,00 25,12 0,47 0 0 0 3,32 100 26,06 14,51 0,24 0,49 2,03 1,01 100 6,57 29,28 0,37 0,28 0,23 2,38 100 10,25 20,84 0,22 0,54 0,4 0,76 1,22 100 24,00 19,05 0,38 0,19 0,1 9 1,14 2,67 100 0,3 8 0,6 1 Using waste heat 3,19 Total 73,86 57,2 3 7,57 29,74 0,36 0,30 1,6 4 0,5 2,66 100 Following our distinction between renewable and non-renewable innovations, Figures 11a and 11b show how “Alternative energy production” eco-innovations evolved. To better present these trends, we took into account the time period between 1970 and 2010, excluding the previous phase during which only 20 patents were filed. Figure 11a describes the evolutionary trend of technologies for producing energy from renewable sources. In particular, it reveals that all of them present a U-shaped trend, hence highlighting that, despite their environmental advantages, these technologies have not been used for a long time, for the above mentioned reasons. In fact, their growing trend is visible during the oil shock, due to the need of new sources of energy, and, after that, environmental programs, such as the Kyoto protocol, have fostered the use of less polluting electricity production technologies. In particular, while “Hydro energy” and “Wind energy” solutions initially received only a marginal attention, in the last few years the interest towards their use seems increased. For instance, in 2005 the Global Wind Energy Council was launched to provide a credible and international representative forum for the entire wind energy sector. Differently, Figure 11b depicts a steady growing development trend for all the different technological classes (except for “pyrolysis or gasification of biomass” that probably reached its peak in the maturity phase in the early 1990s). This trend may be reasonable due to the fact that those solutions have been principally promoted by the environmental concerns came up in the late 1980s to replace oil-based energy sources. Figure 11a ”Renewable” technologies’ development trend. Figure 11b ”Non-renewable” technologies’ development trend. 4.3. Energy conservation Reducing carbon emissions, as well as bridging the energy gap between energy production and consumption, let energy conservation practices receive an increasing attention in several countries (ES, 2012). As made before, we first present the patenting activity as a whole. Then, we provide a brief analysis for each subclass. Figure 12 presents the patenting application activity since 1946, as measured by patent count per year, both globally and per different geographical regions. It shows that, before the late 1980s, the interest towards energy conservation technologies is not comparable with the innovative efforts made between 1970 and 1986 in the “Alternative energy production” and “Nuclear energy” fields (see Figure 1 and 5, respectively). In fact, only in the U.S., after the oil crisis, there is presented a slow growth of the innovative effort in energy conservation technologies, whereas a time of stagnation is depicted from 1976 till the end of 1980s. This could be explained by considering that, differently from the solutions developed in the other two technological categories, in this case innovative efforts are directed towards the reduction of energy consumption, rather than the exploitation of new energy sources. Thereby, the main exogenous shocks, as the oil crisis occurred during the Kippur War, have probably not determined, at the global level, an analogous attention towards conservation energy issues. Indeed, only in the U.S. there were some government initiatives toward energy conservation, hence fostering spending on research, new laws, incentives, as well as the introduction of novel solutions (Wulfinghoff, 2000). Figure 12 Trend of “Energy conservation” patent applications. By considering the years from 1985 to 2000, Figure 12 shows that “Energy conservation” patenting activity saw a sharp growth rate, even higher than that characterizing the “Alternative energy production”. This is especially true for the U.S. and Japan. Accordingly, the number of patents granted in the “Alternative energy production” class in that period had an increase of 150%, while the number of patents granted in the “Energy conservation” class raised of 250%, thus suggesting that the relevance of energy conservation started under the banner of environmental protection and resources scarcity problems, as highlighted during several international conferences and in related documents, such as the 1972 Stockholm Conference on the Human Environment and the Brundtland’s Report (e.g., WCED, 1987). Indeed, the growing trend could be explained by referring to several policy actions taken place starting from late 1980s in response to those concerns. For example, in the U.S. a collaboration of manufacturers and energy efficiency advocates resulted in the 1987 National Appliance Energy Conservation Act, which set specific Federal energy conservation standards for many household products (Gillingham et al., 2006). A further energy efficiency legislation was represented by the 1992 Energy Policy Act (Public Law 102-486), which extended standards for other products, like motors, lamps, commercial heating, and cooling equipments, in order to improve the overall energy efficiency. In addition, in Japan from 1993 to 2008, after the Earth Summit held in 1992, a series of amendments were enacted so as to deal with global environmental issues and set energy conservation goals2. In particular, the New National Energy Strategy in 2006 and the Basic Energy Plan in 2007 specified that a clear technology strategy was mandatory, especially to identify a roadmap regarding long term technology development. In Figure 13 another interesting finding emerges. Specifically, Europe doesn’t seem to have significantly invested in energy conservation technologies. In fact, it is possible to notice that relative few efforts have been devoted in this area compared to the other technological domains previously discussed. Differently, U.S. and Japan’s patenting activities reveal a noteworthy attention paid towards energy conservation technologies, similar to the one demonstrated for the production of renewable energy. Figure 13 also reveals that other countries like South Korea and Taiwan have worked more intensely on these solutions, differently from what occurred for alternative energy technologies. This may be explained by taking into account that energy conservation technologies, such as low energy lighting lamps or new solutions for buildings’ energy efficiency, result more marketable (Lopez-Pena et al., 2012), hence reducing R&D investments’ risks, and at the same time having good environmental performances. In addition, especially for Japan, energy conservation solutions are probably the best way to cope with an increasing energy demand relying only on the imports of fuel resources. In fact, as Energy Information Administration (2012) highlighted, despite Japan relied on oil and gas imports to meet about the 60% of its energy needs in recent years, it is shown that from 2000 to 2010 self-produced resources were less than the 1% of those consumed. As highlighted for the other two categories, even in this case inventors rely also on non-patent literature in developing “Energy conservation” technologies (see Figure 14). This could be explained by looking at the actions discussed in the previous paragraph, even though this behavior appears to be more recent in this category than in the “Alternative energy production” one. Figure 13 “Energy conservation” patent share geographical area. 2 http://www.asiaeec-col.eccj.or.jp/contents02.html Figure 14 “Energy conservation” scientific citations analysis. Figure 15 Top 10 organizations in “Energy conservation” class with the highest patent intensity, as represented by the bubble dimension, and related period of the highest patenting activity (x-axis) and outcome quality (y-axis). Figure 15, showing the leading organizations in terms of number of patents owned, provides other important insights. First, European organizations are not classified in the top ten rank. Second, Japanese firms present a significant patenting activity, especially referring to recent years. However, their invention quality, measured by citations received, is lower than those characterizing U.S. companies. Finally, Eastman Kodak Company behaves differently from the other companies. In fact, it seems the only organization undermining the Japanese leadership in terms of both quantity and quality. Probably, it is the only firm that is trying to move towards new technological trajectories, thus developing high impact and valuable solutions. Figures 16a shows the distribution of breakthrough inventions among the analyzed regions. It reveals that U.S. companies hold the majority of high quality patents, probably because of the Japan’s late entry in the patenting activity. Interestingly, despite the littler efforts showed, European countries have generated a higher number of breakthrough eco-innovations in the field than Japanese firms. In addition, Figure 16b shows that highly cited patents were filed between 1971 and 1982. Figure 16a “Energy conservation” breakthrough patent share geographical area. Figure 16b “Energy conservation” breakthrough innovation’s development trend. Table 2 presents “Energy conservation” subclasses. It shows that, differently from the other two main classes, U.S. does not always own the majority of patents in each category. Indeed, the number of patents in the “Low energy lighting” and “Measurement of electricity consumption“ subclasses owned by Japan exceeds the number of patents granted by U.S.. This may be due to the fact that in the last energy plan the Japanese government actively promotes the use of LED lighting to replace the traditional style incandescent bulbs and other related initiatives (IEA, 2010), which include technologies for measuring energy consumption, and this is likely to have stimulated innovative efforts in these two subclasses. Finally, Figure 17 shows temporal trends in patenting activity for each subclass. It shows that only “Low energy lighting” and “Storage of electrical energy” had an increasing trend. On the contrary, the other categories provide a little contribution to the overall trend. Table 2 Total patent share and percentage of patents owned by geographical area for “Energy conservation” technologies. Patent share U.S. EU JP BRIC CAN TW KOR Storage of electrical energy 30,47 49,71 9,50 27,11 0,74 3,20 4,65 3,27 Total by OTHERS geographical area 1,82 100 Power supply circuitry 2,08 61,33 11,78 16,00 0,44 1,33 6,22 1,56 1,33 100 Measurement of electricity consumption 1,74 35,88 11,61 47,49 0 1,58 0,53 1,58 1,32 100 Storage of thermal energy 4,20 62,84 21,17 10,47 0,44 1,43 1,21 0,88 1,54 100 Low energy lighting Thermal building insulation, in 40,01 30,57 10,2 44,03 0,37 1,3 6,21 5,94 1,39 100 20,45 66,65 20,15 4,76 0,34 5,39 0,71 0,39 1,62 100 Recovering mechanical energy 1,05 65,35 18,86 5,26 0,44 5,26 1,32 0,44 3,07 100 Total 100 general Figure 17 “Energy conservation” subclasses evolution. 5. Discussion, Implications, and Conclusion This paper studies the evolution of eco-innovations in the energy field, specifically focusing on low-carbon energy technologies, by investigating patenting activity trends both globally and in specific geographical areas. Furthermore, this paper tries to explain evolutionary trends as a result of country policies, as well as historical events that may have fostered such innovations. To this aim, a unique database of patented inventions filed at the U.S.PTO. between 1946 and 2010 and belonging to the “Nuclear power generation”, “Alternative energy production”, and “Energy conservation” technological areas has been created and analyzed. Several interesting findings concerning the dynamics and distribution of low-carbon energy technologies emerged. First, the global evolutionary trends of eco-innovations show the key role played by geopolitical circumstances. In fact, the eco-innovative activity increases with the highest grow rate during the petrol crisis period and in the early 1990s, as a result of the global warming awareness, except for few technological categories, as “Pyrolysis or gasification of biomass”, “OTEC”, and “Storage of thermal energy”. This shows that governments’ strategies and energy programs set important frameworks and initiatives to foster and sustain eco-innovation development (Popp, 2006). The main example is represented by the substantial contribution in developing nuclear power solutions provided by the U.S. government and the Commissariat à l'énergie atomique, which appear in the top 10 patents’ assignee classification in the nuclear energy category. A further example is given by Japan, which developed a governmental plan fostering the use of LED lighting and became the leading country for low energy lighting. Nevertheless, as shown through the analysis of the leading innovative organizations, private companies owns the majority of the developed eco-innovations. On one hand, this shows that commercial activities have an important role in the eco-innovation’s development. This is in line with previous studies, which highlight that once a firm comes up with new technological solutions embedded in a product, other companies try to experiment different solutions which are markedly different from each other. This goes on till one design emerges as the more promising to better meet users’ needs in a relatively complete manner, namely dominant design (Abernaty and Utterback, 1978). Then, convergence on a dominant design leads to period of incremental changes in the chosen technological solution (Abernaty and Utterback, 1978; Teece, 1986; Tushman and O’Reilly, 1997; Suarez, 2004). Hence, as competition evolves within the market, technological solutions shift to cope with market needs. On the other hand this is the result of the fact that climate change is playing a growing role in business competition (Porter and Reinhardt, 2007) and in turn can also impact on future national innovative programs. Second, data analyses depict a great discrepancy between subclasses in each main technological area. In fact, some of them represent less than the 1% of the total amount of patents developed within a specific class. In particular, what is worthy to note is that, although certain subclasses include hot technologies upon which current debates are focusing, this does not necessarily corresponds to a higher patent share, such as in the case of “Alternative energy production” class. In fact, patent analyses show that wind, geothermal and hydro technologies represent only the 8% of the total amount of patents granted, despite their widely recognized important role in the next future as effective and sustainable technologies. However, the current wholesale rate is certainly far from the required level. By taking into account what occurred for some low-carbon technologies, such as nuclear plants and solar cells, the eventual push to full commercialization may significantly foster their spread and boost innovation, hence again highlighting how commercial opportunities can enhance innovative efforts (Teece, 1986, Suarez, 2004). Third, our study sheds new light on which are the major inventor countries. We showed that innovation in low-carbon energy technologies is mostly generated in the U.S., which accounts for more than a half of the total inventions. The innovative performance of Japan is also particularly impressive, since in a number of subclasses, such as in solar energy and low energy lighting technologies, it ranks equal to or better than Europe. Other countries, such as South Korea, Canada, Taiwan, or Australia, present significant contributions in the patenting activity only in some particular technological fields. For instance, Canada owns the 5% of all patents in the thermal building insulation category and the 3% of breakthroughs in the energy conservation category, while it does not contribute in the development of renewable energy technologies at all. Furthermore, South Korea and Taiwan primarily focus on energy conservation solutions. Looking at BRIC, it seems that they are still far from intensive innovative activity, despite the fact that their environmental awareness is growing, as well as the use of eco-innovation solutions (Lewis, 2007; Levi, 2010). However, it should be noticed that our analysis looks at the trends of patents filed until 2010. During more recent years, BRIC investments in lowcarbon energy technologies have significantly grown (e.g., PEW, 2010; Lema et al., 2012), so suggesting that the trend of patents in this field by those countries is destined to grow. Another important result emerges from the analysis of scientific-based citations. Specifically, in recent years, the number of patents which are also based upon scientific literature is growing. This could be a signal that the goal of strengthening the role and the appliance of scientific knowledge to support sustainable development (as described in the Chapter 35 of Agenda 21) is becoming effective. Thus, inventors are probably more deeply focusing on scientific research than in the past, hence making use of scientific knowledge to increase their understanding of environmental problems and creating suitable technological solutions (e.g., Fleming and Sorenon, 2004). Finally, our analysis shows how breakthrough eco-innovations were developed in the three different technological areas. Results show that for “Alternative energy production” and “Nuclear power generation” classes breakthroughs’ development occurred in the earliest stage of eco-innovation evolution, and that it is restricted in few years. Reasonable explanation lies in the fact that knowledge about using wind, water, sun or nuclear power is older than 1970s, but it was never fully exploited due to the use of carbon and petroleum. However, since the early 1970s, resource scarcity problems and environmental concerns attracted funds and shifted global attention towards new form of energy generation. Hence, new business opportunities have emerged, pushing organizations in protecting their inventions to compete in these new markets. Similarly, “Energy conservation” breakthroughs were developed early in time, but in a longer period than the other two classes. This could be explained by considering that energy efficiency needs emerged under the banner of resource scarcity issues, hence needing more time to develop effective actions and technologies. However, these results may also be related to the choice of our measure for identifying breakthrough eco-innovations. In fact, it highlights those patents that are fully exploited, hence more cited. Thus, new significant inventions, which, as we said, probably rely on scientific knowledge and so may need of a long term to be applied, may be not fully recognized by our proxy. In terms of managerial and policy implications, our suggestions are threefold. First, it emerges that the development of eco-innovations is influenced by both private and public efforts. Thus, we encourage corporate executives and policy makers to invest in strengthening their networks, by which technical, economic, and political knowledge could be better integrated in order to follow both business and social needs, as well as integrate all the competences needed to address the complexity characterizing the ecoinnovation development (see also Messeni Petruzzelli et al., 2011). Second, it is shown that different types of low-carbon energy technological solutions have been developed in response to environmental and geopolitical concerns. Thus, it results how companies and policy makers can adopt different types of ecoinnovations, which are, however, very difficult to be fully studied, assessed, and regulated. Hence, a centralized organism that looks over the intensity and dynamics of their applications and their interaction with the society is needed. Furthermore, clear national policies on eco-innovations should be underpinned by international agreements through which all countries commit to take action to reduce their environmental impacts and can keep pace with the ever-changing technologies that are developed. Third, eco-innovation evolution is a global issue. Thus, transferring appropriate solutions by taking into account specific local needs, as well as ensuring their effective implementation, can help to address environmental and economic goals. This is especially true for developing countries where the assimilation, adaptation, and maintaining of the imported technologies assume a fundamental role (UN, 2012). To our knowledge, this study is the first attempt to depict a comprehensive scenario of eco-innovations evolution in the field of energy. Furthermore, we investigated their evolutionary trends by analyzing a wide dataset of patented inventions to address the topic in a complete and deep manner. Nevertheless, this study has some limitations that should be acknowledged. First, the innovation process is described by means of patents, which do not represent the whole innovative portfolio. Indeed, some innovations are not patentable and patents do not always represent the most suitable appropriation mechanisms (Levin et al., 1987; Bessen, 2006). Moreover, the rate at which new innovations are patented varies across industry (e.g., Levin et al., 1987; Gittelman, 2008). Second, comparisons at global scale raises some biases since the value of patents vary across countries and the characteristics of appropriation regimes significantly affect the propensity to patent (Archibugi and Pianta, 1996; OECD, 2009c). Third, despite its important role, we focused on a specific type of eco-innovation, as technological eco-innovation, although other kinds of eco-innovations, such as organizational and business eco-innovation, can be recognized and investigated (e.g., Kemp and Pearson, 2008). In addition, to address these limitations, future research should place more emphasis on eco-innovation commercialization. We highlighted the relevance of commercial activities to spread those technologies. Hence, providing insights and empirical studies on how firms’ capabilities, technological characteristics, and environmental circumstances interact in order to bring those technologies to the market are needed. 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