1. Thermal energy storage (TES) technologies like phase change materials (PCMs), sorption, and thermochemical materials can store solar and renewable heat for use when needed. 2. PCMs use the heat of phase change during melting and freezing to efficiently store and release thermal energy. Organic PCMs like paraffin wax are promising due to their high storage density and melting temperatures around human comfort levels. 3. Sorption technologies use physical or chemical bonding to store heat in materials like silica gels, zeolites, or chemical reactions. A demonstration used zeolite to store nighttime heat from district heating for use during the day.

1. Compact Thermal Energy Storage Wim van Helden Webinar Leonardo-Energy 23 Jan. 2009

2. Contents of this Webinar Share and potential of Thermal Energy Storage Introduction to Compact TES TES technologies: principles and applications Phase Change Materials Sorption Thermal Storage Thermochemical Materials International developments

3. PRIMARY ENERGY USE FOR HEATING PURPOSES EU energy consumption

4. Position of Thermal Energy Storage Thermal storage: enabling technology solar thermal concentrated solar power biomass cogeneration heat pumps district heating …

5. enables a larger share of renewables system optimisation - diminish the number of on/off cycles - satify peak demand (enabling smaller heat generators) demand-side management - operation determined by energy prices - optimally controlling (micro) cogeneration Relevance of Thermal Energy Storage For all energy sources buffering of heat is desirable . For the application of solar thermal energy and ambient heat buffering is even necessary .

6. Stage of development of TES technologies TCM (chemical) Research Sorption (latent) Development PCM (latent) Demonstration Water (sensible) Mature market

7. Sensible heat - principle: heat capacity - reservoirs, aquifers, ground/soil Latent heat - principle: phase change (melting, evaporation, crystallisation) - water, organic and inorganic PCMs Sorption heat and Chemical heat - principle: physical (adhesion) or chemical bond (reaction enthalpy) - a d sorption and a b sorption and chemical reactions Principles for Thermal Energy Storage

8. Classification of Thermal Energy Storage

9. Characteristics of TES Values Unit temperature level [ºC] specific energy density [kJ/kg] or [MJ/m 3 ] thermal power [kW] Categories Choice between - time to market research/test,demo/available for market storage period day / week, month / season Building integration possible / not possible

10. COMPACT HEAT STORAGE When available storage volume is limited  compact heat storage Volume of a seasonal storage for a single family house (m 3 ) kWh/m 3 140-830 70 31 MJ/m 3 500-3000 250 110 Storage density Chemical Latent Sensible

11. Phase Change Materials Principle: heat used to melt or evaporate material Typical storage densities 334 kJ/liter (ice-water) 250 kJ/liter (parafines) Applications Cold storage Overheat protection Comfort temperature control CSP: system optimisation

12. PCM Energy stored as function of temperature

13. Latent heat storage in PCMs PCM interesting at small temperature difference (around melting temperature) Left: volume of water and of TH29 needed for storage of 1 MJ heat. Right: mass of water and of TH29 needed for storage of 1 MJ heat. Volume water and TH29 for 1 MJ storage 0 5 10 15 20 25 0 - 100 10 - 60 15 - 40 20 - 30 temperature difference (°C) litres water TH29 Mass of water and TH29 for 1 MJ storage 0 5 10 15 20 25 0 - 100 10 - 60 15 - 40 20 - 30 temperature difference (°C) kilograms water TH29

14. Water as Phase Change Material storage of heat in phase change from solid - liquid (334 kJ/kg) cheap medium (also available encapsulated) interesting in case of combined heating and cooling demand water-ice mixture behaves like liquid up to 20-25 % ice storage at 0ºC results in small losses to ambient storage at 0ºC results in necessary upgrading heat (heat pump)

15. Latent heat storage in ice Storage tanks for water filled polyethene balls, 2 projects in United States

16. for instance paraffines or polymers heat conduction of material determines charging power, length of polymer chains determines melting temperature relative to anorganic PCMs: larger melting heat and higher heat capacity uniform melting behaviour, stable, non toxic, non corrosive suited for impregnation of building materials prevention of evaporation, odours and volume changes by encapsulation available in different forms Organic PCMs

17. Organic PCMs Left to right: - powder: 60% paraffine and silica material - granulate: 35% paraffine and diatomee earth - boards: 65% paraffine and wood fibre board New development. Compound: 80% paraffine, for direct contact with water, for instance in reservoir

18. Latent heat storage: PCM for daily storage demonstration house in Perth, Australia day storage of solar heat from 30 m 2 collectors storage in 90 m 2 TH29-system (equivalent to 0,65 m 3 PCM) TH29-system: capsules on long strips integrated in floor, melting temperature of PCM 29ºC buffer is charged with flexible pipes between capsules LT floor heating system

19. Phase change Materials in walls development project with the partners BASF, caparol, maxit and Sto with Fraunhofer ISE 1/1999 - 9/2004 funded by BMWi FKZ 0329840A-D

20. measurements two identical rooms measured without and with two PCM products monitored one year each result: - 4 K difference reached - night ventilation essential

21. Since 2004 several products: Different products with microcapsules: plaster, plasterbords, porous concrete… ….. Different macrocapsules: Dörken, Rubitherm, SGL, Climator and others BASF: micronal SmartBoard™ Other systems: Energain, Rubitherm granules Foto: BASF

22. Latent heat storage: inorganic PCMs PCM can of Climator: typically applied in transformer rooms and telecom installations Nodule of Cristopia: HDPE ball filled with eutectic salt

23. Storage for Concentrated Solar Power CSP KNO 3 – NaNO 3 mixture Melting around 250 C Spain, USA Two-tank direct molten-salt thermal energy storage system at the Solar Two power plant. (National Renewable Energy Laboratory)

24. Sorption heat storage Physi-sorption: molecular adhesion forces Adsorption: Surface effect, porous media Silicagel, zeolites Mixing effect: absorption NH 3 , LiCl, LiBr Similar to sorption heat pumps

25. Zeolites Microporous structure Composed of AlO 2 and SiO 2 with metal atoms Adsorption of vapours and gases Selective adsorption dependent on molecule size Stronger bond: higher desorption temperature Crystal structures of three basic zeolite types: ITA, CHA and MFI

26. Temperature dependance Differential mass loss for ALPO-18, ALPO-5, LiNaX (zeolite) and SAPO-34 as function of temperature (Jänchen, 2005)

27. Zeolite Zeolite 13X beads and pellets Small zeolite particles are bound with clay-like binding materials

28. Heat Storage with Zeolite Monosorp system (ITW Stuttgart, DE) Zeolite channeled bricks Solar thermally loaded heat exchanger

29. Sorption heat storage: diurnal storage Field experiment in school in Munich, Germany Diurnal storage of heat from district heating Storage in 7000 kg Zeolite 13X (volume 10 m 3 ) Charging at night (at 130ºC) by separating water vapour from zeolite Discharge at day by absorption of water vapour in zeolite Air heating (for base load) and LT radiators and floorheating Peak power at discharging 120 kW

30. Chemical heat storage General principle A + B  AB + heat Components stored sepearately without heat loss Long term heat storage Charge with temperatures typically higher than 100ºC Storage capacity between 250 and 4000 kJ/kg

31. Materials selection (ECN, 2004) Principal criteria: energy storage density, temperature

32. Thermochemical material – MgSO 4 x7H 2 O Reaction: MgSO 4 xnH 2 O + heat  MgSO 4 + nH 2 O Sample mass decreases at increasing temperature

33. The scale of chemi-sorption Grain of MgSO 4

34. Magnesiumsulphate (ECN –NL) Separate reactor concept

35. Sodiumhydroxide Storage (EMPA – CH) 2NaOH  Na 2 O + H 2 O

36. Chemical heat storage at higher temperatures Chemical reactions e.g. 1/2 N 2 + 3/2 H 2  NH 3 + heat (Nat. University of Canberra, Australia) presently 1 kW prototype: dissociation (charging) at 400 - 500ºC and discharge in a reactor that drives a steam cycle plans to scale up to a 15 kW system

37. TCM Research and Development Goal: a compact heat storage system with storage density 8 times better than water. Activities: materials research process development system development Typical system requirements for application of TCM heat storage in the built environment: storage density > 1 GJ/m 3 driving temperatures < 180 °C charge/discharge power 1-10 kW storage capacity 100 kWh (micro-cogeneration) – 20 GJ (seasonal storage) # cycles: 30 (seasonal storage) – 1500 (micro-cogeneration)

38. International developments IEA SHC Task 32: Advanced storage systems for solar and low energy houses (www.iea-shc.org/task32) PREHEAT project: raising the political awareness of the importance of Thermal Energy Storage. (www.preheat.org) ESTTP Strategic Research Agenda SRA (esttp.org) National R&D programs for TES (FR, GE, …) New IEA SHC/ECES joint Task 42/24: Compact Thermal Energy Storage: Materials Development for System Integration (www.iea-shc.org/task42)

39. Materials and Applications Two International Energy Agency (IEA) programs: Energy Conservation through Energy Storage Solar Heating and Cooling

40. Task 42/24: Compact Thermal Energy Storage: Material Development for System Integration Joint Task between Solar Heating and Cooling (SHC) and Energy Conservation through Energy Storage (ECES) Operating Agents: SHC: Wim van Helden, ECN (NL) ECES: Andreas Hauer, ZAE Bayern (DE) January 2009 – December 2012 Kick-off meeting: 11-13 February 2009. Bad Tolz, DE Main added value: Bring together experts from applications and material science

41. Objectives Identify, design and develop new materials and composites Develop measuring and testing procedures Improve performance, stability, and cost-effectiveness Develop multi-scale numerical models Develop and demonstrate novel storage systems Assess the impact of new materials on systems performance Disseminate the acquired knowledge and experience Create an active and effective research network

42. IEA Task/Annex 42/24 Matrix approach

43. The building blocks for Compact Thermal Energy Storage Political awareness International programmed approach Active national participation Active industrial participation Clever ideas from.. ..Bright enthusiastic people

44. References IEA 32: www.iea-shc.org/task32 Ecostock conference: http://intraweb.stockton.edu/eyos/page.cfm?siteID=82&pageID=29 Preheat project: www.preheat.org IEA ECES Annex 19, see www.iea-eces.org T4224: www.iea-shc.org/task42 wikis.lib.ncsu.edu/index.php/Zeolites