Organic Rankine Cycle (ORC) System Applications for Solar Energy: Recent Technological Advances

: Organic Rankine Cycle (ORC) power generation systems may be used to utilize heat source with low pressure and low temperature such as solar energy. Many researchers have focused on di ﬀ erent aspects of ORC power generation systems, but none so far has focused on the patent landscape of ORC system applications. As such, the objective of this study is to identify published patents on ORC system applications, particularly for solar energy. Four (4) technologies were identiﬁed in ORC application for solar energy: parabolic dish, parabolic trough, solar tower, and linear Fresnel reﬂector. A methodical search and analysis of the patent landscape in ORC system applications for solar energy published between 2007–2018 was conducted using the Derwent Innovation patent database. From the approximately 51 million patents in the database from various countries and patent agencies, 3859 patents were initially identiﬁed to be related to ORC applications for solar energy. After further stringent selection processes, only 1100 patents were included in this review. From these 1100 patents, approximately 12% (130 patents) are associated with parabolic dishes, about 39% (428 patents) are associated with parabolic troughs, approximately 21% (237 patents) are associated with solar towers, and about 28% (305 patents) are associated with linear Fresnel reﬂectors. Published patents on solar tower technology are currently on an increasing trend, led by China. All of these patents were published in the past 11 years. From this study, further researches on ORC application are still ongoing, but ORC application for solar energy has the potential to advance; allowing the world to ease issues related to over-reliance on fossil fuel.


Introduction
Despite its negative connotation, the greenhouse effect is a natural phenomenon and is, in fact, crucial for the continuous survival of humankind on Earth. When sunlight reaches the surface of the Earth, some of the energy is absorbed by the land and the oceans while some of it is reflected back into space. Greenhouse gases in the atmosphere; which include water vapor (H 2 O), carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide (NO 2 ), etc., prevent some of the heat from escaping into space  As can be seen from Figure 1, Rankine Cycle, Kalina Cycle, and low-temperature fuel cells have relatively low working temperatures and have the potential to be used in plants utilizing low-grade heat. Thus far, Organic Rankine Cycle (ORC) systems have been a more popular choice as a power generation system, as they only require simple components, which are widely available on the market. The Rankine Cycle is composed of four stages: (1) isentropic compression at the pump, (2) isobaric evaporation of the boiler, (3) isentropic expansion on the turbine, and (4) isobaric condensation on the condenser. In terms of working fluid, ORC utilizes organic refrigerants with low condensation and boiling points; allowing ORC to utilize low heat grade with low pressure and low temperature [48][49][50][51][52][53][54].
Similar to other power generation plants utilizing low-grade heat, ORC power generation plants are not specifically designed to utilize solar only and have wider applications using other sources of energy. Indeed, they have been used in various applications such as ones employing biological waste heat, geothermal, engine exhaust gases, domestic boilers, and of course, solar thermal power [55][56][57][58][59][60]. Many researchers have expended efforts on various aspects of ORCs; their application, techno-economic analysis, thermo-dynamic analysis, working fluid selections, efficiency optimization of ORC power generation plant, etc. [61][62][63][64][65]. However, thus far, no work has been found that focuses on reviewing the design patent landscape related to ORC. For this study, focus is directed towards the design patent landscape of ORC power generation plants utilizing low-grade heat with low pressure and low temperature, from only solar energy. Four (4) applications have been shortlisted and identified as technologies in ORC application for solar energy as shown in Figure 2. In the next section, a methodical patent search is going to be performed on published patents concerning these technologies related to ORC applications for solar energy.

Methodology
Patent databases are well known as abundant and useful sources of data for forecasting disruptive technology, cutting-edge technology analysis and global management of worldwide invention portfolios. Analysis of patents is especially important in academia and even more so, for corporate entities; as a guide for abundant technology development measurements, and due to the high prospects of patents as an economic scale through commercialization [66].

Methodology
Patent databases are well known as abundant and useful sources of data for forecasting disruptive technology, cutting-edge technology analysis and global management of worldwide invention portfolios. Analysis of patents is especially important in academia and even more so, for corporate entities; as a guide for abundant technology development measurements, and due to the high prospects of patents as an economic scale through commercialization [66].
Derwent Innovation (https://www.derwentinnovation.com), known in the past as Thomson Innovation, was utilized in this study, as an analytics and search platform for our study on patents related to ORC [67]. In order to perform this study, an institution must first subscribe to Derwent Innovation. Derwent Innovation provides more than 51 million patents originating from some major nations, major patent authorities and proprietary sources, as well as further 23 million basic worldwide inventions. It is also equipped with the capability of providing analysis on worldwide patents with connections to numerous records; with English translations from over 30 languages, originating from up to 50 patent-issuing authorities.
Using keywords in patent claims and titles, advanced patent search for technology in ORC application for solar energy was executed with the Derwent Innovation analytics and search platform tool. Search results were then extracted onto Microsoft Excel to allow systematic analysis. The search strategy used to search the patents on ORC technology applications for solar energy was performed using selected keyword terms that are presented in Table 1. Dashboard and spreadsheet facilities in Excel were then used to tabulate results from the search; with details relevant to the patents including title, abstract, names of applicants, priority date, names of the inventor, International Patent Classification (IPC) and patent claims. All the listed patent details were then systematically analyzed and re-organized into correlated categories. Using the PRISMA statement [68] as our basis, the methodical patent landscape review process shown in Figure 3 was followed. Searches were performed for published patents from 2017 up to July 2018, and full patent or patent abstracts were methodically categorized, analyzed and reviewed. The identification stage of the search retrieved a total of 3859 patents; with 1686 patents deemed as duplicate patents, and thus, removed from the results. Title, abstract and claims of the patents were then extracted and meticulously assessed to investigate relevance of the patents for further analysis. In particular, relevance of the patents to Organic Rankine Cycle application for Solar Energy was examined. From the total of 2173 patents in the screening stage, 1001 patents were excluded from our results due to its inapplicability to organic Rankine cycle applications while a further 72 patents were excluded for not satisfying eligibility criteria for solar energy technology. A total of 1100 patents on technology in ORC applications for solar energy, were finalized to be included for further review.

Patent Landscape
A total of 1100 patents on four technologies used in ORC applications-parabolic dish, parabolic trough, solar tower, and linear Fresnel reflector-were selected for review. Approximately 12% or Figure 3. Flowchart of process adopted to review patents results; based on PRISMA Statement [68]. It is noted that only patents with publication dates between 2007 and July 2018 were included in the search. As only the Derwent Innovation platform was used, patents not incuded in the Derwent Innovation database were excluded. Also excluded were prospectively associated patents that were not cited in the patent abstract, keywords and title. A few non-English full patents were also removed; despite their probable relevance to the topic based on the abstracts and claims which were available in English language, due to inaccessibility issues related to language barriers, and limitations of the data and database.

Patent Landscape
A total of 1100 patents on four technologies used in ORC applications-parabolic dish, parabolic trough, solar tower, and linear Fresnel reflector-were selected for review. Approximately 12% or 130 patents from the total 1100 patents are associated with parabolic dishes, 39% or 428 patents associated with parabolic troughs, 21% or 237 patents associated with solar towers and the remaining 28% or 305 patents are associated with linear Fresnel reflectors. A pie chart showing the distribution of patents according to technologies, is given in Figure 4. A plausible explanation on why more patents about parabolic troughs were published may be due to its affordability as compared to the other technologies and due to the fact that they are viewed as more energy efficient [69].

Patent Landscape
A total of 1100 patents on four technologies used in ORC applications-parabolic dish, parabolic trough, solar tower, and linear Fresnel reflector-were selected for review. Approximately 12% or 130 patents from the total 1100 patents are associated with parabolic dishes, 39% or 428 patents associated with parabolic troughs, 21% or 237 patents associated with solar towers and the remaining 28% or 305 patents are associated with linear Fresnel reflectors. A pie chart showing the distribution of patents according to technologies, is given in Figure 4. A plausible explanation on why more patents about parabolic troughs were published may be due to its affordability as compared to the other technologies and due to the fact that they are viewed as more energy efficient [69].    promising. Around 59 patents were published during half of the year; approximately half the number of patents published in the previous year, and as such, the number of published patents in 2018 is expected to be almost similar to the previous years (i.e., in 2015-2017 within the range of 115-125 patents per year). The high annual number of published patents in ORC application for solar energy is important as the use of solar energy is increasing rapidly due to improvement in renewable energy technology. A pie chart depicting the distribution of countries/organizations where patents were filed or granted, is shown in Figure 6A. For each country/organization, the number of different solar energy technologies that were patented, is shown in Figure 6B. It can be seen that the top three countries/organizations with the highest number of published patents are China (CN), the World Intellectual Property Organization (WIPO) and the United States (US), with approximately 37%, 22% and 20% of the total selected patents, respectively. In total, the top three countries/organizations patented 79% of the total 1100 selected published patents.
China has the highest number of published patents in ORC applications for solar energy with 402 patents; composed of 217 patents about solar towers, 83 patents on linear Fresnel reflectors, 81 patents concerning parabolic troughs and 21 patents on parabolic dishes. It is interesting to note that despite the high number of patents about solar tower technology in China, solar tower technology only ranks second in terms of overall number of patents for different technologies from our 1100 selected published patents; superseded by parabolic trough technology, as can be seen from Figure  4. This is because parabolic trough technology is the preferred technology in all other countries/organizations with the exception of China. Parabolic trough technology represents the highest number of patents with 48%, 49%, 78%, 59%, 47%, 53%, 35% and 54% of selected published patents, in Australia, European Union Office, Japan, Korea, United States, WIPO, India and Denmark, respectively.
The number of published patents for different solar energy technologies in ORC application from 2007 until 2018 are presented in Figure 7, with patent data for parabolic troughs, linear Fresnel reflectors, solar towers and parabolic dishes, given in Figure 7A-D, respectively. A pie chart depicting the distribution of countries/organizations where patents were filed or granted, is shown in Figure 6A. For each country/organization, the number of different solar energy technologies that were patented, is shown in Figure 6B. It can be seen that the top three countries/organizations with the highest number of published patents are China (CN), the World Intellectual Property Organization (WIPO) and the United States (US), with approximately 37%, 22% and 20% of the total selected patents, respectively. In total, the top three countries/organizations patented 79% of the total 1100 selected published patents.
China has the highest number of published patents in ORC applications for solar energy with 402 patents; composed of 217 patents about solar towers, 83 patents on linear Fresnel reflectors, 81 patents concerning parabolic troughs and 21 patents on parabolic dishes. It is interesting to note that despite the high number of patents about solar tower technology in China, solar tower technology only ranks second in terms of overall number of patents for different technologies from our 1100 selected published patents; superseded by parabolic trough technology, as can be seen from Figure 4. This is because parabolic trough technology is the preferred technology in all other countries/organizations with the exception of China. Parabolic trough technology represents the highest number of patents with 48%, 49%, 78%, 59%, 47%, 53%, 35% and 54% of selected published patents, in Australia, European Union Office, Japan, Korea, United States, WIPO, India and Denmark, respectively.
The number of published patents for different solar energy technologies in ORC application from 2007 until 2018 are presented in Figure 7, with patent data for parabolic troughs, linear Fresnel reflectors, solar towers and parabolic dishes, given in Figure 7A-D, respectively.
As can be seen in Figure 7A, the number of published patents for parabolic troughs followed an increasing trend post-2007; peaking at 60 patents in 2011, before following a decreasing trend after 2011. For 2018, it is predicted that the number of published patents to be less than the previous year; based on the half-year data which were available.
For linear Fresnel reflector technology in Figure  As can be seen in Figure 7A, the number of published patents for parabolic troughs followed an increasing trend post-2007; peaking at 60 patents in 2011, before following a decreasing trend after 2011. For 2018, it is predicted that the number of published patents to be less than the previous year; based on the half-year data which were available.
For linear Fresnel reflector technology in Figure   The number of published patents for parabolic dishes generally follows an almost similar pattern to that of linear Fresnel reflectors, as can be seen from Figure 7D. The maximum number of published patents for the parabolic dish was in 2014 with 21 published patents.
These are unlike the number of published patents for solar tower technology. From Figure 7C, the number of published patents also increased annually after 2007. However, assuming the full-year data would be double that of the half-yearly data of 29 patents, the number of published patents in 2018 was expected to increase, exceeding the maximum annual published patents of 41 patents in 2016. As such, it may be assumed that the number of published patents for solar tower technology has yet to reach its peak. The number of published patents for parabolic dishes generally follows an almost similar pattern to that of linear Fresnel reflectors, as can be seen from Figure 7D. The maximum number of published patents for the parabolic dish was in 2014 with 21 published patents.
These are unlike the number of published patents for solar tower technology. From Figure 7C, the number of published patents also increased annually after 2007. However, assuming the full-year data would be double that of the half-yearly data of 29 patents, the number of published patents in 2018 was expected to increase, exceeding the maximum annual published patents of 41 patents in 2016. As such, it may be assumed that the number of published patents for solar tower technology has yet to reach its peak.
Overall number of patents vs publication year, is presented in Figure 8. Generally, it can be deduced that the numbers of published patents for these technologies initially   Collectively, it can be deduced from Figure 5 that the number of published patents in ORC applications has been almost constant in the period 2015-2018. This observation is likely due to the fact that policies from various countries are still maintaining renewable technologies as their prime sources of energy. Potential environmental impacts associated with solar power; such as climate change, global warming, uncertainties by countries worldwide, habitat loss, can vary depending on the implementation of technologies. One thing is for sure, it is crucial at this current time to conserve the scarce natural resources that we have, which have been over-utilized for the past decades. Huge difference may be realized by putting minimal effort on conservation; to help preserve the natural  Collectively, it can be deduced from Figure 5 that the number of published patents in ORC applications has been almost constant in the period 2015-2018. This observation is likely due to the fact that policies from various countries are still maintaining renewable technologies as their prime sources of energy. Potential environmental impacts associated with solar power; such as climate change, global warming, uncertainties by countries worldwide, habitat loss, can vary depending on the implementation of technologies. One thing is for sure, it is crucial at this current time to conserve the scarce natural resources that we have, which have been over-utilized for the past decades. Huge difference may be realized by putting minimal effort on conservation; to help preserve the natural resources for future generations.

Technology Updates
This section discusses current research updates available in the patent databases on the topic of ORC system applications on solar energy. As presented in Figures 2 and 4 in previous sections, ORC system applications may be categorized into four broad applications: parabolic dishes, parabolic troughs, solar towers and linear Fresnel reflectors. Details of technology updates for each category are discussed in the following sections.

Parabolic Dish
Parabolic dish systems contain a concave dish-shaped concentrator, which reflects sunlight onto a receiver located at the focal point of the parabolic dish, as shown in Figure 9. Supplemented by a solar tracking system, concentrated reflections from the relatively large area of the parabolic dish onto the heat receiver are capable of increasing the temperature of the receiver up to 200-700 • C; with the heat engine of the receiver used to convert heat energy onto electricity. The efficiency of the systems to convert heat onto electricity is commonly quite high, capable of producing average annual yield rates that are typically 18-23% higher than those of other solar energy systems. The high efficiency of the system coupled with the modularity of its components, makes parabolic dish systems highly suitable for distributed electricity generation from solar energy [70].  One of the research focuses on parabolic dish systems for ORC applications, is in further improving efficiency of the solar receiver with the use of tubular cylindrical cavities [70]. A coated copper closed-tube open cylindrical cavity was used as heat engine with thermal oil as its working fluid. Another working fluid considered was the refrigerant gas R141B under saturated vapor conditions. Thermal operations of the system were initially modelled to allow optimization of the cylindrical cavity receiver. Important parameters determining performance of the system include the shape, reflectivity and optical error of the concentrator. Also important are the tracking error of the solar tracking system, inlet temperature and flow rate of the thermal oil as well as the aperture area, tube diameter, cavity depth of the receiver.

Parabolic Trough
Parabolic troughs are some of the most popular solar thermal electrical generation systems. It is the most developed concentrating solar thermal technology with the most number of published One of the research focuses on parabolic dish systems for ORC applications, is in further improving efficiency of the solar receiver with the use of tubular cylindrical cavities [70]. A coated copper closed-tube open cylindrical cavity was used as heat engine with thermal oil as its working fluid. Another working fluid considered was the refrigerant gas R141B under saturated vapor conditions. Thermal operations of the system were initially modelled to allow optimization of the cylindrical cavity receiver. Important parameters determining performance of the system include the shape, reflectivity and optical error of the concentrator. Also important are the tracking error of the solar tracking system, inlet temperature and flow rate of the thermal oil as well as the aperture area, tube diameter, cavity depth of the receiver.

Parabolic Trough
Parabolic troughs are some of the most popular solar thermal electrical generation systems. It is the most developed concentrating solar thermal technology with the most number of published patents. In the US, research on parabolic trough technology was started back in the early 1980s by the Department of Energy, with parabolic trough electrical generation systems already working steadily and privatized by the mid-1990s. It is expected that the currently available parabolic trough electrical generation systems will be operational for the next 20 years.
As indicated in Figure 10, parabolic trough systems use curved highly reflective mirrors that are designed to reflect and direct the sunlight onto the linear heat receiver fixed on the focal axis of the trough. The linear heat receiver is made up of heat-absorbing pipes. The heat transfer fluid absorbs thermal energy produced from the concentrated solar reflections on the pipe, which consequently flows to the steam generator. The heated fluid drives the turbine of the steam generator, producing super-heated steam, which is then converted to electricity. Once the thermal energy from the heated fluid is used up, it is then recirculated and reused by the system [70]. One of the articles compares the performance of solar ORC (s-ORC) systems using parabolic trough technology and photovoltaic (PV) systems, both with capacity of 50 kWe, in terms of its technical and economic performances [71]. Solar ORC and PV systems utilize thermal energy and battery storage systems, respectively, for their energy storage requirements. Results indicate that ORC using parabolic troughs is potentially more cost-effective in scenarios where power supply reliability is essential, provided the system is coupled with efficient thermal energy storage [71]. A performance comparison between parabolic troughs and linear Fresnel reflectors was studied in [72] by assuming integration of the two different collectors into a mid-size concentrating solar power plant, based on ORC power generation. Using solar data from Italy with an average annual energy production per unit area of 1729 kWh/m 2 y, the power plants were modelled with different solar multiples and storage capacities values, and simulations were performed. With an assumed ORC power generation capacity of 1 MW with 24% conversion efficiency, the parabolic trough has been shown to be more cost effective in terms of energy produced per unit area of solar collector; capable of producing 180-190 kWh/m 2 of energy. The superior performance of the parabolic trough may be attributed to its higher optical efficiency. Figure 11 depicts a typical solar power tower system; which is a type of solar furnace utilizing a high tower to gather focused sunlight. As can be seen from the figure, arrays of movable, flat heliostats are used to reflect and concentrate sunlight onto the solar power tower. These concentrated rays heat liquid onto steam, which is then used to power up the turbine to generate electricity. As compared to parabolic trough, solar power tower is relatively cheaper. This is because heliostats used in solar tower system utilize standard flat flare glasses which are less expensive than trough mirrors One of the articles compares the performance of solar ORC (s-ORC) systems using parabolic trough technology and photovoltaic (PV) systems, both with capacity of 50 kWe, in terms of its technical and economic performances [71]. Solar ORC and PV systems utilize thermal energy and battery storage systems, respectively, for their energy storage requirements. Results indicate that ORC using parabolic troughs is potentially more cost-effective in scenarios where power supply reliability is essential, provided the system is coupled with efficient thermal energy storage [71]. A performance comparison between parabolic troughs and linear Fresnel reflectors was studied in [72] by assuming integration of the two different collectors into a mid-size concentrating solar power plant, based on ORC power generation. Using solar data from Italy with an average annual energy production per unit area of 1729 kWh/m 2 y, the power plants were modelled with different solar multiples and storage capacities values, and simulations were performed. With an assumed ORC power generation capacity of 1 MW with 24% conversion efficiency, the parabolic trough has been shown to be more cost effective in terms of energy produced per unit area of solar collector; capable of producing 180-190 kWh/m 2 of energy. The superior performance of the parabolic trough may be attributed to its higher optical efficiency. Figure 11 depicts a typical solar power tower system; which is a type of solar furnace utilizing a high tower to gather focused sunlight. As can be seen from the figure, arrays of movable, flat heliostats are used to reflect and concentrate sunlight onto the solar power tower. These concentrated rays heat liquid onto steam, which is then used to power up the turbine to generate electricity. As compared to parabolic trough, solar power tower is relatively cheaper. This is because heliostats used in solar tower system utilize standard flat flare glasses which are less expensive than trough mirrors used in parabolic trough system which need to be specifically manufactured with specific curvatures depending on the designs of the parabolic trough system [73].

Linear Fresnel Reflector
Linear Fresnel reflector technology is notable for its similarity to the parabolic trough system. Whilst mirrored troughs are used to reflect and concentrate sunlight in parabolic trough systems, arrays of slightly curved or flat mirrors are placed at different angles to reflect and concentrate sunlight onto a rigid receiver, made up of a coated long tube and located on top of the arrays of mirrors. A single axis Sun tracking system is used to ensure that the mirrors track the Sun movement, such that maximum sunlight is concentrated onto the receiver. Similar to parabolic trough system, heat is used to convert the heat transfer fluid into steam as it passes through the receiver; which are consequently used to drive the steam turbine for electricity production [74]. Solar thermal electricity generation by linear Fresnel reflectors is illustrated in Figure 12.
Recent work involving the use of linear Fresnel reflectors is given in [74] for the liquefaction of natural gas using solar technology. A cascaded ORC configuration was used to produce liquefied natural gas as well as electrical power; by integrating the system to arrays of linear Fresnel reflectors for supplying energy to the system. It is shown that the novel configuration can reduce the production cost of liquefied natural gas.
In [72], the performance of mid-size solar power plants integrated to arrays of linear Fresnel reflectors was compared to that of similar plants integrated with parabolic troughs. Although the performance of systems integrated to linear Fresnel reflectors has been shown to be inferior to systems integrated with parabolic troughs, plants with linear Fresnel reflector technology have been shown to be capable of producing a respectable annual amount of 55-60 kWh of electricity per m 2 of the solar collector. This electricity generation estimation was produced using solar data from Italy with an average annual energy production per unit area of 1729 kWh/m 2 y. Two large and prominent electric power generation plants/projects in the United States have been developed utilizing solar tower technology; the Ivanpah solar electric power generation system and the Crescent Dunes solar energy generation project. Located in the Californian desert, the Ivanpah solar electric generation system is considered the biggest concentrated solar thermal plant in the United States, capable of producing a massive 392 MW of electricity. The plant utilizes a total of 173,500 heliostats; with each heliostat consisting of two mirrors, to reflect and concentrate sunlight onto its three solar towers. The Crescent Dunes solar energy generation project, which is located in Nevada, has a much smaller capacity than the Ivanpah system, with a capacity of 110 MW.
Other than the United States, other countries have also developed electric power generation plants utilizing solar tower technology. Notably, Spain has developed quite a number of solar tower power generation systems. For instance, Planta Solar 10 and Planta Solar 20 are capable of generating 11 MW and 20 MW of electricity, respectively, by integrating steam turbine power generator to solar tower technology. Another project is Gemasolar, which can generate 20 MW of electricity.

Linear Fresnel Reflector
Linear Fresnel reflector technology is notable for its similarity to the parabolic trough system. Whilst mirrored troughs are used to reflect and concentrate sunlight in parabolic trough systems, arrays of slightly curved or flat mirrors are placed at different angles to reflect and concentrate sunlight onto a rigid receiver, made up of a coated long tube and located on top of the arrays of mirrors. A single axis Sun tracking system is used to ensure that the mirrors track the Sun movement, such that maximum sunlight is concentrated onto the receiver. Similar to parabolic trough system, heat is used to convert the heat transfer fluid into steam as it passes through the receiver; which are consequently used to drive the steam turbine for electricity production [74]. Solar thermal electricity generation by linear Fresnel reflectors is illustrated in Figure 12.

Technology Updates
In this section, some selected recently registered patents in the database are discussed and elaborated. The first one is on solar energy overlapping Rankine cycle power generation systems with different exothermic modes [75]. This newly patented system is based on ORC power generation using solar energy as its source of heat. Different exothermic modes have been used for the system. The patent also includes parabolic groove type heat collector arrays to power steam ORCs. This newly patented technology allows annual ORC savings, such as shortening of the payback period, makes operating time longer, as well as generating more energy. Another patent [76] is on combined solar thermal power generation system using ORC. This patent combines solar thermal power generation using ORC for a power generation system, a heat exchanger, a parabolic trough solar collector and a dish power generation. This ORC power generation uses the heat released by a Stirling engine. The ORC utilized an extra heat source that increases steam turbine capability and increases the total efficiency of power generation [76].
One of the most interesting newly patented technologies is based on photovoltaic and photothermal coupled thermoelectric generation systems and methods that use ORC [77]. This newly patented solar power generation is a power generation subsystem, a heat collection subsystem, and a heat supply system; with these systems linked together in series. The heat collector of the system is parabolic and is connected to a photovoltaic and photoelectric system. The ORC is a heat exchanger, a condenser, a turbine generator, a pump and a storage tank that are all connected in series. The system maximizes the use of absorbed solar energy and therefore, increases energy efficiency and reduces the life cycle cost of the entire system. Another newly patented technology is based on ORC power generation device that use a flow path control method for heat collecting fluid [78]. The developed system is a combination of ORC and solar energy heat collector; with the solar collector consisting of shell pipes that are required for liquid distribution, and parabolic concentrator. The patent claims through this new method a stable and efficient power generation that can be achieved by just adjusting flow rate of the system. Latest technology updates on newly patented implementation of solar energy in ORC are tabulated in Table 2. Table 2. Patent updates on organic Rankine cycle (ORC) system applications for solar energy. Recent work involving the use of linear Fresnel reflectors is given in [74] for the liquefaction of natural gas using solar technology. A cascaded ORC configuration was used to produce liquefied natural gas as well as electrical power; by integrating the system to arrays of linear Fresnel reflectors for supplying energy to the system. It is shown that the novel configuration can reduce the production cost of liquefied natural gas.
In [72], the performance of mid-size solar power plants integrated to arrays of linear Fresnel reflectors was compared to that of similar plants integrated with parabolic troughs. Although the performance of systems integrated to linear Fresnel reflectors has been shown to be inferior to systems integrated with parabolic troughs, plants with linear Fresnel reflector technology have been shown to be capable of producing a respectable annual amount of 55-60 kWh of electricity per m 2 of the solar collector. This electricity generation estimation was produced using solar data from Italy with an average annual energy production per unit area of 1729 kWh/m 2 y.

Technology Updates
In this section, some selected recently registered patents in the database are discussed and elaborated. The first one is on solar energy overlapping Rankine cycle power generation systems with different exothermic modes [75]. This newly patented system is based on ORC power generation using solar energy as its source of heat. Different exothermic modes have been used for the system. The patent also includes parabolic groove type heat collector arrays to power steam ORCs. This newly patented technology allows annual ORC savings, such as shortening of the payback period, makes operating time longer, as well as generating more energy. Another patent [76] is on combined solar thermal power generation system using ORC. This patent combines solar thermal power generation using ORC for a power generation system, a heat exchanger, a parabolic trough solar collector and a dish power generation. This ORC power generation uses the heat released by a Stirling engine. The ORC utilized an extra heat source that increases steam turbine capability and increases the total efficiency of power generation [76].
One of the most interesting newly patented technologies is based on photovoltaic and photo-thermal coupled thermoelectric generation systems and methods that use ORC [77]. This newly patented solar power generation is a power generation subsystem, a heat collection subsystem, and a heat supply system; with these systems linked together in series. The heat collector of the system is parabolic and is connected to a photovoltaic and photoelectric system. The ORC is a heat exchanger, a condenser, a turbine generator, a pump and a storage tank that are all connected in series. The system maximizes the use of absorbed solar energy and therefore, increases energy efficiency and reduces