Solar energy mainly involves using the sun’s energy to generate electricity through solar photovoltaic cells and CSP (concentrating solar power) systems, or to heat water via thermal systems [90]. Figure 7 below shows how solar energy can be used to heat water for domestic use. Photovoltaic systems convert solar energy into electricity directly via a photovoltaic (PV) cell. PV cells are semiconductors that directly convert solar radiation into direct electric current [91,92,93].

By 2015, the installed solar power capacity in Europe was 97.14 GW, with countries such as Germany, the United Kingdom, Belgium, Spain, Italy, France, and Greece accounting for over 85.7% of this capacity [95]. With current campaigns to increase the share of renewable energy in total energy production, the installed capacity is expected to increase to even higher percentages [96]. In fact, there is a commitment by European Union nations to increase the proportion contributed by renewable energy by 27% by the year 2030 [97].

The major issue (barriers) facing the implementation of solar and photovoltaic energy is intellectual property rights [98]. While negotiations surrounding other aspects associated with global climate change have progressed, negotiations regarding intellectual property rights associated with solar and photovoltaic technologies (and other renewable sources of energy) have not made significant progress [99]. No agreement has been reached regarding the transfer of intellectual property rights associated with either green energies or technologies associated with mitigating the effects of climate change. There are those who argue that intellectual property rights are the barrier to the transfer of clean energy (climate change) technologies [100,101]. There is also another group of scientists who argue that intellectual property rights are very important incentives for research and development, and innovations. In particular, the main argument is that industrialised nations which bear the largest number of patent applications for renewable energy sources fear that the implementation of technology transfer policies may deprive innovative firms within their jurisdiction of essential intellectual assets [102]. Developing nations, on the other hand, perceive technology transfer as expensive and should, thus, be facilitated by developed counterparts [103].

As a result of this, there have been debates about who should fund (support) technology transfer, the role of intellectual property rights, and capacity buildings associated with renewable sources of energy, of which solar energy is part of. Therefore, some nations view intellectual property rights transfer as a barrier to the diffusion (transfer) of technology.

This stalemate has resulted in the intermittent implementation of renewable energy technologies among European Union member states. Additionally, the aforementioned stalemate has resulted in fewer renewable energy investments in developing nations. A good example of this ramification is the huge disparity between investment in renewable energy and the number of intellectual property rights. From a statistical analysis of EU intellectual property rights and renewable energy panel data, it was found that nations with larger GDPs tended to have higher number of patent applications and investment in renewable energy when compared to smaller nations. This is evidence of a lack of technology transfer amongst the EU member states.

As a result of these difficulties, technology transfer has been one of the major functions of UNFCCC since it was formed. To enhance technology transfer, the convention (via article 4.5) requires developed nations, to all practicable steps, to facilitate, finance, and promote the transfer of clean energy technologies and intellectual property rights to other nations, especially to developing nations.

Biomass includes all organic matter, such as trees, crops, and plants, that collect and store solar radiation via photosynthesis [104]. Bioenergy or biomass energy essentially comes from the conversion of biomass into energy such as heat, liquid fuel, and electricity [105,106]. Biomass can be burnt directly to produce heat energy, or it can also be converted into biofuels which can be transported and stored [107,108]. Since this type of energy can be transported and stored, its energy supply is highly dependable. This is unlike solar and wind energy, which are often intermittent. Bioenergy can be ategorized into three generations, namely the first, second, and third generation [109]. First generation biofuels are made from food crops that are often grown in arable (cultivatable) land [110]. Consequently, they compete with food and thus are a food security threat. Second generation bioenergy comes from non-food biomass, but this biomass is also often grown in arable land. This means that they compete with food crops for space [111,112]. Figure 8 below shows a comparison between petroleum fuel sources and the first two generations of bioenergy. Third generation bioenergy does not compete with food and is produced from non-food biomass. Additionally, this biomass is not cultivated in arable land. They are often cultured [113].

One of the challenges affecting the transfer of bioenergy amongst European Union member states is the disagreement about how the various resources associated with biomass and bioenergy should be used. Some member states feel that the EU was never transparent on several issues. For instance, it is argued that the EU was never specific about the land use, change of land use, and forestry agreement (also known as LULUCF agreement), which specifically affected the transfer of biomass and bioenergy technology [115,116]. This agreement covers the use of forestry in developed nations that had pledged to reduce greenhouse gas emissions in accordance with the Kyoto protocol [117]. Since a few European Union nations, such as Sweden, Finland, and Austria, have large timber industries and wanted to protect them, the Environment Council of Ministers was not able to agree on the rules and policies associated with forestry in developed nations [69].

As is the case with solar energy technology, the transfer of biomass technology as a renewable source of energy is hindered by intellectual property rights [118]. It is argued that the issue of intellectual property rights cannot be resolved, so long as the sharing of renewable energy technologies amongst EU member states cannot be agreed upon. Member states holding advanced bioenergy technologies are not willing to share their know-how, nor bear the cost of sharing their know-how [119]. Other developed member states are also unwilling to increase costs associated with sharing such technologies [120]. On the other hand, EU member states that spend a lot less money on the research and development of renewable energy sources argue that the cost associated with intellectual property rights should be shared amongst all member states [121].

The use of biomass to produce energy has negative implications. For instance, first generation biomass can also be used as source of food and is cultivated in arable land [122]. This means that embracing this type of energy may result in food insecurity, as crops that should be used as source of food would now be used to produce energy [123]. Second generation biomass is cultivated in arable land (land used to grow food crops). This means that embracing this type of technology would result in food insecurity, as land that should be used in cultivation of food crops would now be used to produce second generation biomass [124]. As a result, it is recommended that when implementing biomass as a source of energy, only third generation biomass should be considered, as that type of biomass does not compete with food crops in any way, and it is cultured instead of being cultivated [125].

Additionally, the regulated use of trees and other biomass as a source of fuel as a way of reducing carbon emissions (as trees act as carbon sinks), as suggested by the LULUCF agreement, would mean that amount of biomass that would be available for processing bioenergy would be limited [126].

Wind energy mainly involves the conversion of wind energy into a useful form of energy, such as electricity by wind turbines, mechanical energy by wind wills, pumping water by wind pumps, and propelling ships by sails [127,128,129]. Figure 9 below shows an example of a wind farm with wind turbines for the production of electric energy.

As of 2016, the installed capacity of wind energy in the European Union was 209.6 GW, of which 165.9 GW were from onshore installations and 43.9 GW were from offshore installations [130]. The current installed capacity of onshore wind energy in the European Union is approximately 169 GW [131]. It is estimated that by 2050, the installed capacity of wind energy and other renewable sources of energy will contribute to the highest proportion of energy mix amongst European Union member states [132,133].

For many decades, developed nations among the European Union member states have been the custodians of wind energy technologies [135]. On the other hand, developing nations inside and outside the EU, such as China, India, and Brazil, have been the recipients of these technologies [136,137,138]. Nevertheless, their participation in the research and development of such technologies has been minimal [139]. After the Kyoto protocol, there has been successful wind energy technology co-operation amongst EU member states, and among EU and Asian countries (such as the co-operation between Germany and China). A good example is the co-operation between the EU and India [140]. However, not all technology co-operations have been successful [141].

From the discussion above, the main issue hindering wind energy technology transfer amongst EU member states, and from EU members to other nations outside the EU, is intellectual property transfer with a focus on who should bear the cost associated with sharing the technology [142,143]. Developed nations are unwilling to share their wind energy technologies because they feel that it is not in their best interest with regards to innovation. Furthermore, they feel that if they must share, then it is the developing nations requiring the technology that should bear the associated costs [144]. Developing nations, on the other hand, argue exactly the opposite [145]. As a result, no agreement has been reached regarding the transfer of intellectual property rights associated with wind energy [146,147]. This lack of agreement has hindered the successful transfer of wind energy amongst EU member states [148].

The ramification of this challenge is that there has been no successful wind energy technology transfer between Germany (i.e., a developed European Union nation) and India, thereby depriving the European Union of the benefits of technology sharing and transfer [149]. The main reason for this unsuccessful co-operation was that Indian technologies were being marked as completely different technologies in Germany [150].

Undoubtedly, there is a stalemate with regards to the transfer of wind energy amongst EU member states. This stalemate has hindered the full implementation of renewable energy technologies amongst European member states [151]. Developed nations are not willing to enhance the transfer of wind technologies (which most of them hold) to the less-developed nations in the EU [152]. It is because of this reason that the correlation between renewable energy intellectual property rights and the implementation of renewable energy among EU member states is divergent [153]. Nations with larger GDPs tend to have a larger number of renewable energy patent applications and larger investments in renewable energy, while the opposite is true for smaller nations (nations with smaller GDP per capita). This is evidence of a lack of technology transfer amongst EU member states [154].

It is therefore recommended that, to enhance technology transfer, the UNFCC Article 4.5 be applied, according to which developed nations, to all practicable steps, should facilitate, finance, and promote the transfer of clean energy technologies and intellectual property rights to other nations, especially to developing nations.

Marine renewable energy often comes from six sources, namely: tidal currents, ocean currents, waves, salinity gradients, tidal ranges, and ocean thermal energy conversion [155]. These marine energy sources are often research and development intensive, and most are in the demonstration or prototype stage [156].

Currently, the global installed capacity of ocean renewable energy is approximately 77 million MW. Countries like Australia, the United Kingdom, Germany, France, South Korea, the Netherlands, China, Canada, and others have already installed varying amounts of marine renewable energy technologies [157,158]. With the current campaigns towards adopting renewable sources, it is expected that the installed capacity of these renewable sources of energy will increase in the future [159]. Figure 10 depicts an artist illustration of the futuristic OpenHydro marine current turbine [160].

One of the major challenges affecting the technology transfer of marine renewable sources of energy is that these technologies are still young and most of them are yet to be refined. This means that they are still in the prototyping and developing stage [161], and thus are not ready for use by the masses. As a result, the custodians of these technologies are unwilling to share their technologies with the masses, regardless of the amount of cash being offered. They feel that sharing the intellectual property rights of non-refined technology may lead to them losing control of the technology and any benefits that may be associated with it [162].

Another major barrier associated with technology transfer in marine renewable sources of energy is the disagreement regarding who should bear the costs associated with sharing intellectual property rights [163]. On one hand, nations that have already developed and are implementing marine energy technologies (most of which are developed EU member states and have invested heavily in research and development) feel that sharing the technology without proper cash involved will hurt their research and development industry [164]. That is, their scientists will be unwilling to invest their time in developing new technologies. On the other hand, nations in need of these technologies (most of which are developing EU member states) feel that it is their developed counterparts who should bear any costs associated with the transfer of marine energy technologies [165]. This stalemate that hinders the transfer and mass implementation of renewable sources of energy amongst EU member states has already been discussed.

From the discussion above, it is observed that there is a stalemate amongst European Union member states regarding who should be responsible for the transfer of intellectual property rights associated with marine energy technologies [166]. This disagreement has resulted in the slow implementation of marine energy renewable sources among EU member states, and fewer investments in marine-based renewable sources across the European Union [167]. To deal with this challenge, an amicable agreement amongst the EU member states needs be reached on how to safely release this technology [168].

It is also observed that most of the technologies associated with marine energy are not fully refined as they are still being developed. This means that, as already mentioned in Section 7.2, the technology is not yet ready for the market and use by the masses [169]. As a result of this, the implementation of marine renewable energy technologies amongst EU member states is not widespread.