Various options of energy storage are described in patented solutions in the field of solar energy. They include such technologies as those using latent heat, molten materials, compressed air, and chemical reactions. In the pool of collected patent documents on solar energy storage, technical solutions disclosing the use of latent heat form the largest group of documents. In continuation of the article on energy storage technologies dated 05.06.2022 and articles dated 20.06.2022 and 22.12.2022 on CSP tracking systems, below we provide for your consideration a short analysis of patent documents related to solar energy storage systems employing latent heat approach.
More than 350 patent documents published in the twenty-year period from 2002 to 2021 were used for the present analysis by using Advanced Energy Technologies methodology. The collected documents are published in 22 patent offices of the world by 145 applicants from 21 countries.
Solar energy. Energy storage employing latent heat. Relationship of number of applications to total number of documents by year
From the chart above, we can see that in general the number of both granted patents and registered patent applications in recent years was consistently high. In 2013-2020 in average about 40% of the technical solutions were represented by start patent applications, that didn’t belong to previously formed patent families. Although the peak of emergence of new applicants and new IPC subclasses in the collected pool of documents was in 2018, later on these values also were high, which, combined with a consistent appearance of new patent offices, can indicate that this subject attracts new participants, who expand technical and geographical coverage of the technology.
During the twenty-year period, the largest number of patents were granted in USPTO (US) – almost 35% of all collected patents. It was followed by CNIPA (CN) with about 22%. Similar picture can be seen in the collection of patent applications registered in the past 5 years, excluding that the gap between the shares of the two offices is smaller here – USPTO (US) – about 26%, and CNIPA (CN) – about 22%. EPO, JPO (JP), INPI (FR), and OEPM (ES) should also be mentioned as the patent offices that granted more than 5 patents each on the subject of interest during 2002-2021.
Solar energy. Energy storage employing latent heat. Breakdown of inventions by patent offices. Patents, 2002-2021 (left); Applications, 2017-2021 (right)
Residents of the USA were in the lead by the number of patents granted during the 20-year period with a share of almost 27% of all cases. In the case of recent patent applications, the first place was shared by the residents of the USA and China with a share of almost 20% for each of the two countries. High activity was also shown by residents of the United Kingdom, France, Germany, and Spain.
Following is a list of top 10 applicants for patents published in the 20-year period:
Solar energy. Energy storage employing latent heat. Top applicants. Patents, 2002-2021
|Status||Country||Name||Average rating||Total 2002-2021|
|Organization||FR||Commissariat à l'énergie atomique et aux énergies alternatives||16.2||11|
|Company||US||Sunlight Power, Inc.||10.8||9|
|Company||DE||SGL CARBON AG||13.3||4|
|Company||US||Bluelagoon Technologies Ltd||12||3|
|Company||AU||Climate Change Technologies Pty Ltd||11||3|
|Company||US||Dow Global Technologies, LLC||15.7||3|
In the collection of patents published in 2002-2021, Sunamp Limited (GB) was leading in terms of Market involvement ratio (Market involvement ratio = volume ratio multiplied by ownership ratio, where Volume ratio - share of applicant documents in total number of documents, Ownership ratio - applicant's participation share in total number of documents) with a value of more than 11%. It was followed by Commissariat à l'énergie atomique et aux énergies alternatives (FR) with more than 6%. Commissariat à l'énergie atomique et aux énergies alternatives (FR) and Sunamp Limited (GB) were also in the lead in the case of applications published in the past five years, with about 11% and 6%, respectively.
Solar energy. Energy storage employing latent heat. Top applicants. Applications, 2017-2021
|Status||Country||Name||Average rating||Total 2017-2021|
|Organization||FR||Commissariat à l'énergie atomique et aux énergies alternatives||12.2||11|
|Company||AU||Climate Change Technologies Pty Ltd||6.2||5|
|Organization||US||University of California||9||5|
|Organization||GB||City University London||4.3||4|
|Company||AU||Sunlands Company Pty Ltd||4.3||4|
|Company||US||Sunlight Power, Inc.||7.3||4|
|Company||IL||Yeda Research and Development Co., Ltd.||11.5||4|
|Company||JP||Ibiden Co., Ltd.||6||3|
In the collection of patent documents describing technologies of energy storage employing latent heat, the most commonly mentioned problems were Low efficiency due to solar movement, High costs of equipment production, and High costs of repair and replacement. Generally, both patents and patent applications were presented in the form of devices. Methods can also be met in a substantial number of documents, while compositions are encountered less often. In addition to the IPC subgroups defining the selection of patent documents used for the present analysis (F28D20/02, F24S60/10, C09K5/02), the most popular IPC subgroups were F28D20/00 (Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D 17/00 or F28D 19/00), C09K5/06 (the change of state being from liquid to solid or vice-versa [2006.01]), F24J2/34 (having heat storage mass), F03G06/06 (with solar energy concentrating means), and F03G6/00 (Devices for producing mechanical power from solar energy).
The largest patent family in the collection of documents used in the present analysis includes 26 patent documents and is represented by core document EP2865965A1 (Core document is a base document for which a complete description of the invention is available in generally-accessible patent databases). It is followed by patent families with core document US20150260463A1 (22 patent documents) and WO2011058383A3 (21 documents):
METAL HEAT STORAGE APPARATUS / A: EP2865965A1 / IPC: F24J2/10, F24J2/30, F24J2/34 / KIM BYUNGGYUN / KIM BYUNGGYUN / Appl. date: 10/01/2014; Publ. date: 29/04/2015 / European Patent Organisation / Core document: EP2865965A1 / Technology categories: SH / Technology elements: ES / Problems: HCEP, LEEF, LESE / Types of technical solution: D / Claims: 6 / Rating: 8
SYSTEMS AND METHODS FOR ENERGY STORAGE AND RETRIEVAL / A: US20150260463A1 / IPC: F28D20/00, F24J2/34, F28D15/00 / Laughlin Robert B, Larochelle Philippe, Cizek Nicholas / GIGAWATT DAY STORAGE SYSTEMS, INC. / Appl. date: 25/03/2015; Publ. date: 17/09/2015 / United States Patent and Trademark Office / Core document: US20150260463A1 / Technology categories: CPV / Technology elements: ES / Problems: HCEP, HCPC / Types of technical solution: D, M / Claims: 20 / Rating: 8
Energy storage systems / A: WO2011058383A3 / IPC: F24H7/00 / Field John, Bissell Andrew / SUNAMP LIMITED [GB/GB] / Appl. date: 16/11/2010; Publ. date: 19/05/2011 / World Intellectual Property Organization / Core document: WO2011058383A3 / Technology categories: LFR, PT, SH, ST / Technology elements: ES / Problems: LESM / Types of technical solution: D / Claims: 93 / Rating: 9
The following abbreviations are used in the documents hereinbefore and hereinafter: D – device; M – method; CPV – Concentrator photovoltaics; E – Experimental CSP; LFR – Linear Fresnel reflector; PT – Parabolic trough; SH – Storage CSP or Hybrid CSP; ST – Solar tower; G – CSP or PV in general; AOP – Administrative and organisational problems; HCEP – High costs of equipment production; HCM – High costs of maintenance; HCPC – High costs of plant construction; HCRR – High costs of repair and replacement; LEEF – Low efficiency due to environmental factors; LEOA – Low efficiency of optics or absorber; LESE – Low efficiency of secondary equipment; LESM – Low efficiency due to solar movement; ES – Energy storage.
Below are several examples of patent documents with the highest rating calculated using Advanced Energy Technologies methodology, from the collection of documents describing energy storage technologies employing latent heat:
Solar energy. Energy storage employing latent heat. Prominent patent documents by rating, 2002-2021:
IMPROVED PHASE-CHANGE LATENT HEAT THERMAL STORAGE DEVICE / P: EP3120098B1 / IPC: F28D20/02, F28F19/00, F28F19/01, F28G1/08, F28G3/10 / COUTURIER Raphaël, CHAZELLE Benjamin, FOURMIGUE Jean-François / COMMISSARIAT À L'ÉNERGIE ATOMIQUE ET AUX ÉNERGIES ALTERNATIVES / Appl. date: 20/03/2015; Publ. date: 28/02/2018 / European Patent Organisation / Core document: WO2015140297A1 / Technology categories: SH / Technology elements: ES / Problems: HCEP, HCM, LESM / Types of technical solution: D, M / Claims: 19 / Rating: 19
Electrical power systems incorporating thermal energy storage / P: US10326276B2 / IPC: F01K13/00, F01K3/00, F01K3/18, F02C1/05, F03G6/00, F24S10/00, F24S20/20, F24S60/00, F28D20/00, F28D20/02, G05D23/19, H02J15/00, H02J3/28, H02J3/38 / Green Adam / Solarreserve Technology Llc / Appl. date: 05/04/2016; Publ. date: 18/06/2019 / United States Patent and Trademark Office / Core document: US20180083449A1 / Technology categories: E, LFR, PT, ST / Technology elements: ES / Problems: AOP, HCEP, LESE, LESM / Types of technical solution: D, M / Claims: 23 / Rating: 18
IMPROVED PHASE-CHANGE LATENT HEAT THERMAL STORAGE DEVICE / P: FR3018905B1 / IPC: F24J2/04, F28D20/02 / COUTURIER RAPHAEL, HAZELLE BENJAMIN, FOURMIGUE JEAN-FRANCOIS / COMMISSARIAT À L'ÉNERGIE ATOMIQUE ET AUX ÉNERGIES ALTERNATIVES / Appl. date: 21/03/2014; Publ. date: 06/05/2016 / National Institute of Industrial Property / Core document: WO2015140297A1 / Technology categories: SH / Technology elements: ES / Problems: HCEP, HCM, LESM / Types of technical solution: D, M / Claims: 28 / Rating: 18
Dispositif de stockage d'énergie thermique par matériau à changement de phase solide/liquide comprenant un condenseur (en: Device for storing thermal energy by a solid-liquid phase-change material comprising a condenser) / P: EP3368852B1 / IPC: F28D20/02, F28D20/00 / Caron Adèle, Couturier Raphaël, Doiseau Aude-claire / Commissariat Energie Atomique / Appl. date: 12/10/2016; Publ. date: 06/11/2019 / European Patent Organisation / Core document: WO2017071959A1 / Technology categories: SH / Technology elements: ES / Problems: HCRR, LEOA / Types of technical solution: D, M / Claims: 14 / Rating: 17
Echangeur thermique a fluide caloporteur a assemblage optimise et un dispositif de stockage d'energie thermique par materiau a changement de phase comprenant ledit echangeur (en: Optimized assembly heat pump heat exchanger and thermal energy storage device by phase change material comprising said exchanger) / P: FR3046838B1 / IPC: F28D20/02 / Garcia Pierre, Nivelon Pierre / Commissariat Energie Atomique / Appl. date: 20/01/2016; Publ. date: 14/12/2018 / National Institute of Industrial Property / Core document: WO2017125513A2 / Technology categories: G / Technology elements: ES / Problems: HCEP, HCRR, LESM / Types of technical solution: D, M / Claims: 23 / Rating: 17
Storage device intended for a thermal power plant and method for using same / P: EP3234353B1 / IPC: F03G6/00, F28D20/00, F28D20/02 / Deydier Alexandre, Couturier Raphaël, Garcia Pierre / Commissariat À L'énergie Atomique Et Aux Énergies Alternatives / Appl. date: 18/12/2015; Publ. date: 17/10/2018 / European Patent Organisation / Core document: WO2016098075A1 / Technology categories: SH / Technology elements: ES / Problems: HCRR, LESM / Types of technical solution: D, M / Claims: 6 / Rating: 17
Electrothermal energy storage system and an associated method thereof / P: US9695715B2 / IPC: F01K25/10, F01K3/12, F03G6/00, F03G6/06, F22B1/02, F28D20/00, F28D20/02 / Kalra Chiranjeev Singh, Peter Andrew Maxwell, Shisler Roger Allen / General Electric Company / Appl. date: 26/11/2014; Publ. date: 04/07/2017 / United States Patent and Trademark Office / Core document: US20160146061A1 / Technology categories: G / Technology elements: ES / Problems: HCEP, HCRR, LESE, LESM / Types of technical solution: D, M / Claims: 20 / Rating: 17
In addition to systems employing latent heat, among the energy storage technologies used in solar power plants, groups of patent documents can be distinguished, describing technical solutions based on the use of compressed air, various chemical reactions, and molten materials.
A few dozens of patent documents describing compressed air solutions and published between 2002 to 2021 were collected for the analysis. Among them, the most popular patent offices were USPTO (US), EPO, WIPO and KIPO (KR). The most common problems that the collected patent documents address are: Low efficiency due to solar movement, High costs of equipment production, and Low efficiency of secondary equipment. The most active applicants with the largest number of patent documents are LightSail Energy, Inc. (US), IFP Energies nouvelles (FR), and Storelectric Ltd (GB).
In the field of technologies employing chemical processes for energy storage, several dozens of patent documents published over 20 years were collected and reviewed. Among them, the documents published by the CNIPA (CN), USPTO (US), JPO (JP), and WIPO patent offices are predominant. The most frequently encountered problems in these patent documents are Low efficiency due to solar movement, High costs of equipment production, and High costs of repair and replacement; while NJTech Nanjing University of Technology (CN) and Aichi Steel Works, Ltd (J.P.) can be mentioned as the most active applicants.
More than a hundred of patent documents were collected for a 20-year selection of inventions disclosing technical solutions using molten materials. The most popular patent offices in this case are CNIPA (CN), USPTO (US), EPO, and WIPO. The most common problems here are High costs of repair and replacement, Low efficiency due to solar movement, and Low efficiency of secondary equipment. Among the applicants with the largest number of patents and applications in the collection, BASF, SE (DE) leads by a wide margin, followed by Shenzhen Enesoon Science & Technology Co Ltd (CN), Siemens AG (DE).
Following are several examples of patents and patent applications that concern energy storage employing the above technologies:
- US10907620B2 – a heat storage including a heat injection system using alkali metal transfer fluid in vapor form, a storage tank with a thermal storage material containing both molten and solid salt, and a Sodium or Potassium heat transfer fluid. The system is aimed at reducing operational complexity and decreasing salt freezing risks;
- US10451358B2 – decreased production costs and improved efficiency is achieved by a heat storage system employing latent heat capable of heating a heat storage material on both the side of a cooling heat exchanger and on the side of a heating heat exchanger;
- US9938896B2 – the need for large storage reservoirs is avoided by a compressed air storage system capable of storing and managing air above 225 bars;
- US20190233701A1 – improved specific heat capacity of thermal energy storage material is achieved by a nanocomposite material comprising a nanoporous material and a base heat transfer fluid disclosed in the invention;
- US20210164696A1 – the application aims at reducing capital and maintenance costs and improving energy storage efficiency by providing a thermal-electrochemical energy storage device comprising heat transport medium, storage medium, an electrochemical cell to convert storage medium.
Energy storage employing latent heat
Patent US10907620B2 by Sunlight Power, Inc. (US) discloses a heat storage system comprising a heat injection system with a thermally conductive tube containing a working fluid (alkali metal transfer fluid in vapor form – Sodium or Potassium) volatile under depressurized conditions and flowing down-tube in one-way direction. The working fluid circuit is substantially evacuated of non-condensing gas. The system further includes a storage tank with an operating temperature of about 800°C comprising a closed volume bounded by a thermally conductive subfloor, an insulating wall, and an endwall, and containing a thermal storage material (both molten and solid sodium chloride or potassium chloride salt that naturally separate by density difference) and a heat transfer fluid (sodium or potassium) that floats on the thermal storage material under de-pressurized conditions. The tube extends through the closed volume from the endwall into a chamber below the subfloor and is separated from the storage tank. The claims of the invention also disclose a method of delivering and recovering heat energy from the storage system.
The authors mention that NaCl salt used in the invention has a high latent heat, and state that the prior-art solutions can increase operational complexity and pose a risk of salt freezing in transfer pipes in specific conditions.
The patent is a part of a patent family comprising 20 documents published in US, WO, EP, EA, CA, AU, and ZA between 2013 and 2021.
400 - storage tank, 402 - insulation layer, 404 - liquid NaCl, 406 - solid NaCl
Image from: US10907620B2
Patent US10451358B2 granted to IHI Corporation (JP) describes a heat storage system for solar heat power generating plants. In the system, a heat storage material is contained in a heat storage tank having a cooling side heat exchanger at an upper inner section, a heating side heat exchanger at a lower inner section, and a wall surface heater. The heat exchangers are positioned on the lines connecting the upstream side and the downstream side of the heat source. Flow rate regulating valves are positioned on the cooling line, heating line, and on a heat medium circulating line that is located between a heat source and a heat exchanger at a side of the heat load. When heating the heat storage material, the three valves are opened, and the high-temperature heat medium is introduced into the cooling side heat exchanger and the heating side heat exchanger, so that the heat storage material is heated by both the cooling side and the heating side.
The inventors claim that the provided heat storage system can be produced at lower cost and ensure high heat transmission efficiency.
The invention belongs to a patent family including 10 patent documents published between 2014 and 2019 in US, AU, EP, JP, and WO.
2 - heat storage material, 3 - heat storage tank, 4, 5 - two heat exchangers, 62 - the wall surface heater
Image from: US10451358B2
Energy storage employing compressed air
Patent US9938896B2 by Cheesecake Energy Ltd (GB) describes a compressed air energy storage and recovery system that includes a compressed air tank capable of storing air above 225 bars, and a heat storage unit with a heat transfer fluid (HTF, comprising liquid and particles, for instance, oil, salt and metal particles), comprising a cool HTF reservoir, a hot HTF reservoir, a circulation pump, and a heat exchanger to receive the compressed air. The heat exchanger is connected to the air tank, to an air compressor, and a motor, and is capable of receiving the HTF from cold and hot conduits of the heat storage unit. The heat exchanger extracts heat from the compressed air for storage, and heats the compressed air prior to expansion to recover energy in the air motor. The heat exchanger includes a plurality of tubes made of stainless steel with an inner diameter of 2.5-4.5mm, and a thickness of 0.7-2mm. According to the method of the invention, external energy source is used to compress air to a pressure above 225 bar. The air is conducted through the heat exchanger, and the absorbed heat is stored in a latent heat storage medium, while the compressed air is stored in a storage vessel. The heat exchanger is used to provide heat to the compressed air so that the expanded and heated compressed air could be used for regeneration of energy and generation of power.
Among the prior-art problems, the authors mention the need for a large storage reservoir and large-size or high-cost heat exchanger.
The invention forms a part of a patent family comprising 4 documents published in US, WO, and EP in 2017-2021.
2 – compressor, 4 - heat exchangers, 6-7 - high-pressure gas tanks, 8 - electric motors, 10 - generator , 13 - pressure regulators, 15,16 – valve, 22 – reservoir, 23 - dehumidifier
Image from: US9938896B2
Energy storage employing molten salt
Patent application US20190233701A1 filed by Fundacion Centro de Investig Cooperativa de Energias Alternativas CIC Energigune Fundazioa (ES) discloses a nanocomposite material to be used in a thermal energy storage unit in such applications as a concentrated solar power plants. The nanocomposite material comprises a nanoporous material (preferably, selected from Y-zeolite, Beta-zeolite, MCM-41 zeolite, and ZSM-5 zeolite; 0.5wt%-2wt%) and a base heat transfer fluid within the pores (for instance, alkali metal nitrate salts – a mixture of NaNO3 and KNO3; 98wt%-99.5wt%). The nanocomposite material can be in the form of a fluid or in the form of a dispersion. The authors also propose a method for preparing the nanocomposite material, including the steps of mixing the nanoporous material with a base heat transfer fluid, and melting the resulting mixture at a temperature above the liquidus temperature of the heat transfer fluid. The claims of the invention also specify other composition variants for the nanocomposite material.
The object of the invention is to provide a heat storage material with improved specific heat capacity for high temperature energy storage applications.
The application belongs to a family comprising 8 patent documents published between 2018 and 2020 in WO, AU, EP, US, CL, MX, MA, and ZA patent offices.
Image from: US20190233701A1
Energy storage employing chemical reactions
Patent application US20210164696A1 filed by Karlsruhe Institute of Technology (KIT) (DE) describes a thermal-electrochemical energy storage device and method for such applications as solar thermal power plants. The device comprises a thermal energy storage with heat transport medium (sodium) and storage medium (electrochemical storage medium – sodium cations and chloride anions in liquid form; thermal storage medium – sodium chloride and calcium chloride in solid form adapted to form a fixed bed), a heating device to heat the heat transport medium for the thermal energy storage. The device further comprises an electrochemical cell with a gas compartment and at least a pair of electrodes, one of which are 3-phase electrode with a first phase boundary to the gas compartment and a second phase boundary to the electrochemical storage medium. The cell electrochemically converts the electrochemical storage medium. The device also includes a container adapted to receive the heat transport medium and the thermal storage medium from the thermal energy storage. The method according to the invention comprises heating the heat transport medium to 500°C-850°C by a heating device to change it to a liquid phase for the thermal energy storage; converting the electrochemical storage medium by electrochemical cell, performing back reaction, and flowing it to the container where it changes into a thermal storage medium and releases thermal energy. The claims of the invention further provide detailed description of the chemical processes occurring in the device.
As the disadvantages of the known methods the authors mention material compatibility, difficulties in converting molten fixed bed to fixed bed and associated investment costs, and membrane-related efficiency and maintenance problems.
The application belongs to a patent family of 4 documents published in 2020 and 2021 in WO, US, and DE.
122 Fixed bed, 124 Particle, 146 Electrochemical cell, 150 First electrode, 152 Second electrode, 154 3-phase electrode, 156 First phase boundary, 158 Second phase boundary, 162 Arrow
Image from: US20210164696A1
More detailed information about inventions in the field of solar energy storage, and patent research methodology can be found on aenert.com and in CONCENTRATED SOLAR POWER. Energy Storage. Patent Database. May 2022.