Sand Battery

Sand Battery Technology: A Promising Solution for Renewable Energy Storage^[1][edit | edit source]

• Sand: abundant, inexpensive, available, Non-toxic
• sand-based electrodes--> store &release energy
• Use in small-scale residential systems to large-scale grid-level storage
• Adv:
  • High energy density
  • Long cycle life
  • Cycle stability
  • Safety
  • Potential for renewable energy storage
• Sand-based electrodes--> potential in Li-ion & supercapacitors
• Sand-Based Energy Storage Technologies:
  • Thermal energy storage.
  • Mechanical energy storage.
  • Electrochemical energy storage.
• Required materials:
  • Sand
    • storage medium
    • should have high thermal conductivity
    • low thermal mass
    • withstand high temperatures
  • Thermoelectric Generators
    • Thermal energy in sand to electric energy (discharge: for electricity generation, power industry, space heating)
    • selection: phase-change temperature & energy storage capacity.
  • Electrodes/Heating Coil
    • Transfer thermal energy between sand & the thermoelectric generator
    • graphite or metal foils
  • Insulation
    • Reduce heat loss in charge & discharge
    • Improves efficiency
  • Heat Source:
    • charge the battery & heat the sand
    • Can be solar/ waste heat from industry/ renewable / nonrenewable thermal energy
  • Container
    • Holds everything
    • withstand high temperatures & thermal stresses.
• Design-->based on amount of required thermal energy & storage duration
• Energy generation & storage:
  • wind / solar --> electricity
  • 30%-->immediately power local infrastructure
  • 70%-->store in sand battery & heat to 600-1000°C
  • weaker solar--> use the stored energy
• Charge:
  • Heat to sand--> increase temp --> until treshold-->full energy
  • sand type & heat source--> different charge time
• Discharge:
  • sand--> expose to a heat sink or device that extracts the heat
  • sand temp drop-->energy release as heat
  • Sand type & heat sink temp-->different discharge time
• Sand-battery type:
  • Indirect Heat-Storing:
    • heat transfer fluid (transfer heat to & from the sand)
    • higher temp operation
    • large physical footprint
  • Direct Heat-Storing
    • Direct contact with heat source & heat sink
    • lower temperatures operation
    • compact
  • Thermochemical Heat-Storing
    • chemical reaction
    • store more energy
    • longer charge & discharg time
  • Hybrid Heat-Storing
  • Combine of direct & indirect
  • higher energy density
  • faster charge & discharge
• Application
  • Renewable Storage
  • Heat & Cool
  • Emergency Backup Power
• Challenges
  • Efficiency --> depends on material/ design/ operating condition
  • operating temp
  • scale up

Sand Battery: An Innovative Solution for Renewable Energy Storage (A Review)^[2][edit | edit source]

• UAE --> aims to use 7% of its energy from renewable sources (specifically solar)--> but challenging -->UAE deserts sand
• Sand composotion: silicon dioxide
• Subzero temp areas -->sand-bed-based solar heat/thermal storing promissing
• Dry sand-based TE--> High temp and high energy --> can be used in infrustructure of facilities like car parks
• Obtainable Materials: sand and rocks
• Installedcyclical storage structures: Germany, Canada, Turkey, Korea, the Netherlands, the United States, Finland, France, and Switzerland
• Sand: store up to 1000 °C, zero mass loss, reduced ownership and maintenance costs, improved and stable energy exchange rates
• sand medium: in a single basin solar--> increases the yearly mean of daily output by 23.8% (compared to no sand), hold the thermal energy for extended time, can be used during winter (when no solar available)
• Principle:
  • 30% of the renewable used, 70% stored in sand --> increase temp to 600-1000
• Component of battery:
  • steel casing--> sand & heat transmission piping
  • External--> mechanical mechanisms, regulators, heat exchangers, fan
• Operation:
  • Charge
  • Storage
  • Discharge
• Mechanism:
  • Circulating hot air around sand --> Renewables control a resistance electric heater to increase the temp of the air near sand
  • heat exchange tubing by a fan
  • Dense insulation --> cover --> maintain temp
  • Discharge: blow cool air--> heats up --> can steam water
  • A COMPARISON OF DIFFERENT TES SYSTEMS TABLE AVAILABLE
• Disadv:
  • Limited Temperature Range (300-1000)
  • Slow Charge
  • Low Power Density
  • Land Use
  • Transportation
• Recent:
  • optimize particle size & distribution
• Application
  • grid-level storage
  • portable devices
  • off-grid power systems
  • industrial heating
  • building heating
  • district heating
  • agriculture
  • mining systems

Uses of sands in solar thermal technologies^[3][edit | edit source]

• rock or mineral particles-->silica (quartz), feldspar, carbonates, micas, amphiboles, pyroxenes--> 0.06 to 2 mm in diameter
• 6% of land surface area (6% of the Earth land surface area in different regions)
  • 2% North America
  • over 30% Australia
  • more than 45% Central Asia
• $11 and $58 per metric ton
• specific heat capacities: between 700 and 1000 J/kg◦C
• Thermal conductivity depends on porosity, granularity, moisture content, & mineralogy
  • less porous-->higher thermal conductivity
  • Smaller particles--> less thermal conductivity
  • saturated with water --> higher thermal conductivities
  • Quartz thermal conductivity: 7.7 W/m.K
  • other sand constituents thermal conductivities: from 2.5 to 3.6 W/m.K
• non-toxic, non-corrosive, and non-flammable
• Sand in solar
  • Thermal Energy Storage
  • Solar Absorption
  • Heat Transfer
  • heat insulationsuitable
  • large surface area --> water evaporation as evaporative medium
• Solar Distillation
  • solar radiation --> obtain fresh water from impure water
  • Limitation: low yield during the day and none at night
  • with sand
    • fill the area beneath the basin liner, the basin itself /using containers like metallic boxes, cotton bags, or mud pots
    • maintain higher temperatures
    • increase the evaporative surface area through capillary action
    • fine, uniform sand better, black better, min thickness better, no water height above
• Solar heating
  • Solar thermal collectors + thermal energy storage media
  • High quartz content, low porosity, & high moisture content
  • Dry sand with low quartz content
• Tank thermal energy storage
  • Water: high specific heat capacity but Heat Loss --> Surrounding tanks with sands of low thermal conductivity; Sandy soil: lower heat capacity & thermal conductivity--> less heat loss from tanks compared to granite soil
  • Require
    • Low specific heat capacity and thermal conductivity
    • Dry
    • sufficient depth
• Aquifer Thermal Energy Storage (ATES)
  • contain porous and permeable sand layers
  • hot water in summer--> inject to the aquifer-->heat the soil and existed water--> extract the heat in winter, e.g. 72% recovery in Gassum Formation in Denmark
  • Require
    • High heat capacity and thermal conductivity
    • High porosity and permeability
• Borehole Thermal Energy Storage (BTES)
  • heat to ground by U-pipe heat exchangers in summer-->extract in winter
  • high quartz low porosity sand --> good over bentonite or gravel
  • 50% more heat for a 50% longer duration compared to gravel --> 78% efficiency
  • Belgium: yearly storage efficiency 70%
  • Require
    • high thermal conductivity and heat storage capacity
• Packed-Bed Thermal Energy Storage
  • use packed-bed sand in insulated pits
  • 64% to 91% savings
  • 65–75% of domestic hot water needs
  • Finland
  • Sand --> filled in containers or pits, heat transfer fluid flow through the bed--> Heat transfer in low demand (summer) & extract in high demand
  • Require
    • high thermal conductivity and specific heat capacity
• Solar Greenhouse Enhancement
  • thermal storage walls (Trombe walls) --> increase air and soil temperatures in greenhouses
  • made of: blackened surface (absorbs solar radiation, transferring heat to the sand), sand, and insulation
  • greenhouses with sand thermal storage walls
    • daytime air temp--> rise by 6.4°C above ambient, nighttime temp--> rise by 1.1°C
    • Soil temp-->depth of up to 8 cm--> rise by 6.4°C during the day and by 4°C at night
    • earlier flowering (by 14 days), earlier maturities (by 20 days), and higher yields (by 33.4%)
• Solar Dryers
  • solar radiation --> dry agricultural or food products
  • quartz, sand, gravel, soil minerals, sandstone, rocks, limestone, granite stone, soil, clay, waste concrete, fire bricks, and water
  • sand:
    • in drying chamber and the solar air heater--> reduce drying time & prevent the re-absorption of moisture at night
    • increase the absorber surface area & roughness
    • black-painted fine sand & high specific heat capacity & thermal conductivity
• Solar cooking
• Concentrating Solar Power (CSP)
  • run a power block
• Which sand?
  • Impurities in quartz (should be below 2%) --> less energy density
  • Clays, carbonates, and feldspars--> agglomeration, degradation / reduced specific heat capacity
    • Clays --> higher agglomeration at 600°C
    • Carbonates --> decarbonization below 800°C--> mass loss & altered grain-size distribution
    • Feldspars --> vitrify below 1200°C-->agglomeration --> impact on sand movement.
  • Moderate cooling rates ~ 573°C required
  • Below 1200°C --> quartz to cristobalite --> grain crack
• Solar gasification
  • gasification: carbonaceous materials (like cokes, coal, biomass) --> fuels or chemicals
  • Conventional methods: burning some of these raw materials --> heat generation for gasification --> loss of material & CO2 emission
  • solar--> heat the material (no need to burn materials)----> quarts: receive, transfer & store heat & is inert (no reaction with materials) --> higher fuel quality & less carbon emission
  • mix the carbonaceous materials with quartz --> solar is absorbs and transfers heat by sand --> raise temp (1100) --> thermal decomposition of carbonaceous materials --> syngas (synthetic gas) production
  • require:
    • High specific heat capacity and thermal conductivity
  • Adiabatic Compressed Air Energy Storage
    • Conventional: Excess electricity compresses air --> stored in underground--> natural gas required for reheat when required
    • in sand: heat generated during compression --> store --> reheat compressed air when required by sand
      • Charge: Hot air--> through heat exchanger --> sand flow in apposite direction --> sand warm, compressed air cold
      • Discharge: cold compressed air--> through heat exchanger --> hot sand raise air temp
      • electric cycle efficiency 69%
      • High thermal conductivity and specific heat capacity
• Solar Photovoltaic/Thermal Panels
  • PV-->small fraction of radiation to electricity --> excess to heat --> damage
  • can be store in sand --> Cools down Pannels & prevent overheat
  • e.g: desert sand and phase change materials (e.g., n-octacosane) --> Desert sand better heat transfer
  • most suitable: high thermal conductivity and specific heat capacity
• Solar ponds:
  • application:
    • Industrial Process Heat
    • Desalination
    • Space Heating
    • Power Generation
    • Greenhouse Heating
    • Salt Production
  • Upper zone: low-salinity water--> insulator
  • middle zone (Non-Convective Zone or Halocline) --> gradient of increasing salinity as depth increases --> density gradient--> convection currents prevention from forming -->traps heat in the lower layer
  • Lower zone: high-salinity water-->Stores solar heat--> temp up to 85°C (185°F) or higher
  • encasing sand in bottom and aournd lower layer --> reduce heat losses ( 69%) & store TE
  • high thermal conductivity and specific heat capacity sand
• Solar-Powered Refrigerators:
  • two metal cylinders --> sand-filled space between saturated with water
  • solar --> power evaporation for cooling --> effective, accessible, sustainable
• Recommendation for research gaps:
• Coatings for Quartz Sand--> improve absorption, high mechanical wear & high temperatures up to 1000°C

  

Comparative CFD analysis of thermal energy storage materials in photovoltaic/thermal panels^[5][edit | edit source]

• Desert sand (abundant, resistant to agglomeration, withstand high temperature) & silicon carbide --> enhanced heat transfer
• This study: copper pipe containing a water stream in a rectangular phase change material (PCM) exposed to solar, Additional absorber Layer
• under varying solar irradiance levels (ranging from 150 to 1,200 W/m2)
• desert sand: temperature of the liquid at the outlet boundary and the maximum temperature of the TES matrix are closer --> better heat transfer
• Relationship between the PCM solid fraction and the solar irradiance:
• Desert sand retains heat -->4,500 seconds after heat flux switched off
• n-octacosane retains for longer periods-->store and release heat over an extended period--> better for when heat release overnight required

Cost-effective Electro-Thermal Energy Storage to balance small scale renewable energy systems^[6][edit | edit source]

• Assumes 100% conversion of electricity to heat
• quantity of electricity (P) needed to charge the energy storage: P=mCp​ΔT​/t
  • m: mass of the thermal storage material
  • Cp​: average specific heat capacity
  • ΔT: temperature difference during charging
  • t: time taken
• Thermal to electric = ηth*efficiency (efficiency in sand~85%)
• Heat rate = Power output /Thermal to electric efficiency
• Time for temperature decrease = Energy stored/ Heat rate

Summary comparison between different thermal storage materials for the new electric grid energy storage system. The efficiency is measured by (discharging/ charging *100)

Materials (1.5 mᶟ)	Tmin (◦C)	Tmax (◦C)	Charging (kWh)	Discharging (kWh)	Efficiency
Thermal Oil	180	410	192	84	44%
Molten Salt	200	500	372	118	32%
Sand	180	950	424	360	85%

The cost estimate of the ETES system with sand as the thermal storage material

System/material selection	Quantity of storage material(kg)	Unit price	Total capacity	Base load capacity	Price in ($)	Systemcomponents cost $	Total designcost $	Storage cost $/kWh
ETES/Sand	2446 kg	0.25 $/kg	359 kWh	88 kWh	672	24142	24814	69

Performance evaluation of a sand energy storage unit using response surface methodology^[7][edit | edit source]

• Annual energy consumption: ~624,430 TWh
• Carbon footprint from fossil fuels: 36.7 billion ton
• Renewable energy demand in 2019: 6890.7 TWh
• Expected increase by 2,493 TWh between 2022 and 2025
• Types of TES Systems:
  • Sensible Heat Storage: Simple and cost-effective.
  • Latent Heat Storage: phase change materials.
  • Thermoelectrical Storage: conversion between thermal and electrical energy
  • Storage media:
    • rocks, water, oil, salt
    • Salt: Must be below 600°C
    • Concrete Bricks: daytime, under 500°C, Temperature changes during discharge--> cycle effectiveness reduction
    • SAND:
      • High Thermal Capacity
      • High Thermal Conductivity
      • cost-effective
      • Long-Term Stability
      • Non-Toxic and Environmentally Friendly
      • High-Temperature
      • Optimum size for heat transfer 2–3 mm (larger: heat transfer effectiveness reduction, smaller: Increase in pressure drop-->larger heat exchanger volume)
• This Research:
  • helical coil made of copper inserted inside a cylindrical tank
  • Hot inlet fluid --> into the coil at temperatures up to 200°C
  • Thermal Conductivity Measurement: KD2 Pro Decagon device with a TR1 single needle sensor type at 25°C
  • Specific Heat Capacity Measurement: DSC-25, temperature range 25–200°C
  • Specific Gravity Measurement: 1 kg of desert and beach sand, dried to constant mass (at 110 ± 5 ◦C) then add 6% moisture--> dry for 15-19 h.
• Experimental results:
  • XRF
    • Desert sand:13 elements, calcium 60.96%.
    • Beach sand: 11 elements, calcium 86.9%.
  • specific heat capacity
    • increase with temperature
    • Cp for desert-->higher
    • dehydration of calcium hydroxide formed after heat treatment at 200°C
  • Density
    • Beach sand: denser
  • scenario for simulation:
    • Hot oil--> at 100°C & 0.01 m/s velocity--> heat transfer to 25°C sand, oil temperature decrease--> sand temperature and stored energy increase
    • oil temp change --> increase sand temp and stored thermal energy
    • oil velocity and coil turns increase--> stored energy increase
    • total stored energy per kg of sand-->6.348 kJ/kg after an 8h charging .
    • pressure drop -->71.4 Pa
    • desert sand Thermal conductivity -->higher than beach sand by 1.77%
    • Thermal resistivity of beach sand -->29.3% higher compared to desert sand

Improved effective thermal conductivity of sand bed in thermal energy storage systems^[8][edit | edit source]

• Introduction:
  • TES--> substitute for lithium-ion batteries in stationary electric-grid storage
  • Sand--> high thermal tolerance (melting point around 1700°C)
  • wide temp range-->Enhanced Carnot cycle efficiencies
  • sand High specific heat capacity --> high energy density BUT granular form & point contact between grains -->low thermal conductivity
  • Coating of quartz sand --> improve solar absorption & thermal stability & enhancing energy storage efficiency by 60% to 80% compared to raw sand
  • thermal conductivity of bentonite sand--> increase by add granite powder
  • common methods-->Direct solar heating and heating by fluidisation (Circulating heat transfer fluids through heat exchangers in sand-packed beds)
  • Mixing different heat storage materials--> improve storage properties
  • Waste material streams-->economical materials option
    • cut metal scrap from Metal workshops --> circular economy
• This research:
  • Rectangular aluminium container (height 380 mm, length 230 mm, width 380 mm) --> investigate thermal properties of sand bed
  • Two tubular-type resistance heaters (height 298 mm, width 309 mm, diameter 50 mm)--> 95 mm apart in the center of the box--> 2 kW On/Off control box & temp regulation up to 1000 °C
  • K-type thermocouples --> between heaters (45 ±0.7 mm from each heater) and 30 mm away from heaters
  • Sand bed -->exposed to air (T below 26 °C) without insulation
  • Combination of sand and metallic by-products (enhance thermal conductivity)
    • Brown Silica: silica (SiO2), grain size 0.06 to 0.2 mm, melting point 1713 °C, specific heat capacity 703 J/(kg⋅K), thermal conductivity 0.2 to 0.7 W/(m⋅K), bulk density 1800 kg/m3
    • aluminium:15 to 20 mm long, 0.5 mm thick, 1.5 mm wide, melting point 660 °C, specific heat 897 J/(kg⋅K), thermal conductivity 205 W/(m⋅K), density 2712 kg/m3
    • brass:diameter 0.25 mm, length 4.5 mm, melting temperatures 900 to 940 °C, specific heat 380 J/(kg⋅K), thermal conductivity 113 W/(m⋅K), density 8430 to 8730 kg/m3
    • mixed metal chips: 90% steel, 10% aluminium/ length 10-15 mm, thickness 0.5 mm, breadth 1.5 mm/ Tm: 1370-1540 °C/ specific heat 490 J/(kg⋅K)/ thermal conductivity 50-70 W/(m⋅K) (varies by alloy)/ density: 7850 kg/m³
  • T4: between wall and electric heater/ T3: between two electric heaters
  • surface temperature reaches 500 °C within 30 min
  • T4: heat faster than T3 in first 75 min (17.5 mm closer to heat source) & temperature constant at 350 °C after 3 h & rapid temperature decline outside heating elements
  • T3: hotter than T4 after 80 min, equals surface temperature of heaters after 7 h & less rapid heat loss to environment & heat trap/ low thermal conductivity, high heat capacity of sand --> Terminal lag in T3
  • Sand conductivity: 0.114 W/(m⋅K)
  • Simulated charging time: five hours
  • Brass-sand layer: highest effective thermal conductivity/ higher density and less porous structure--> lower thermal conductivity than aluminium
  • Aluminium chips:
    • More effective in uniform mixture: high thermal conductivity
    • 20% aluminium: heat rate 1.7 times of pure sand & increases stable T4 temperature --> higher effective thermal conductivity
    • 10% and 5% aluminium heat rates 1.36 times and 1.18 times of pure sand
    • Higher aluminium:increased percolation & more interconnections --> facilitate heat transfer
    • Lower chip concentrations: isolation of chips, fewer conductive paths, & lower thermal conductivity
    • enhances overall temperature gradient of sand bed
  • mix-metal chips--> lower performance: higher steel content (lower thermal conductivity)
  • temperature outside thermocouples: metal composite--> Higher temperature than pure sand
  • Metallic chips: easy heat travel--> more storage
  • Commercial scrap metal prices in Finland--> Aluminium: 0.7 & Brass: 3.1 & Stainless steel: 0.7

From waste to value: Utilising waste foundry sand in thermal energy storage as a matrix material in composites^[9][edit | edit source]

• Introduction:
  • Waste foundry sand (WFS) by-product of metal casting processes
  • WFS characteristics: ceramic composition, density, particle size (0.15 mm < D < 0.6 mm), specific surface area
  • WFS recycling pathway: key material for composite phase change materials to capture, store, reuse waste heat
• This research:
  • Materials:
    • NaNO3, natural materials including clay, fully recyclable, Bentonite in sodium form, waste foundry sand (CPCM matrix material, predominant component: SiO2 at 87.91%, secondary components: Al2O3 at 4.7%, Fe2O3 at 0.94%), Additive X (?)
  • Fabrication:
    • Comminution with mortar and pestle (85–95% between 0.6 mm and 0.15 mm uniform grain size distribution)
    • Hand-stirring mixture
    • Shaping into 13 mm pellets under 60 MPa pressure for 2 min
    • Sintering at 400 °C, 5 °C/min in high-temp
    • Cooling to room tempe for shape-stable structure
  • Poor cohesion at 70–30 (WFS-salt) mass ratio -->instability
  • Additive X (?):
    • Thixotropic properties form gel-like matrix with water--> improving WFS particle binding
    • Increases CPCM resistance to stresses during phase change process
  • Tests:
    • Sand grain density: Helium-based pycnometer, 2.51 ± 0.06 g/cm³
    • Bulk density: Mass and volume (dimensions) of individual pellets, Porosity deduced from density ratio
    • Latent heat, melting point, specific heat capacity: DSC: Temperature range: 20 to 400 °C, ramping speed: 10 °C/min, Aluminum crucibles, ambient air environment, gas flow rate: 100 ml/min, sapphire method for specific heat
    • Thermal conductivity and diffusivity: Laser Flash Technique, Level sample surfaces, graphite spray coatingAirflow setting: 100 ml/min, Thermal conductivity formula: λ = a(T)ρ(T)Cp(T)
    • TGA: Sample weight: ~10 mg, platinum crucible, Temperature range: 25 to 500 °C, heating rate: 10 °C/min, ambient air
    • Microstructure and pore size distribution: X-ray nano-CT, Cylindrical samples: φ 2 × 15 mm, Voltage: 95 kV, current: 150 μA, pixel resolution: 9.5 μm, Projection images at 0.1° intervals, 180° rotation, Data analysis: Recon software, CTan software
    • Coefficient of thermal expansion: Optical dilatometer, Cylindrical samples: ~13 mm diameter, Heating: ambient temperature to 500 °C, rate: 5 K/min, air environment
    • Compressive strength
    • Thermal cycling protocol: Temperature increase to 400 °C, hold for 30 minutes, Temperature decrease to 270 °C, hold for 10 minutes,Total of 48 cycles, Structural resilience and thermal efficacy assessment of WFS-salt CPCMs
    • ..... (discussion)
    • Energy storage density: 628 ± 27 kJ/kg for Na60, 567 ± 43 kJ/kg for Na55
    • Average thermal conductivity: 24% higher for Na60 (1.38 W/mK) than Na55 (1.08 W/mK), due to higher porosity of Na55
    • Compressive strength: 141 MPa for Na60, 105 MPa for Na55, influenced by porosity and pore size
    • Larger porosity beneficial for CTE of CPCM

Heat Storing Sand Battery^[10][edit | edit source]

• Desert sand can store thermal energy up to 1000 ℃
• 400 ℃ higher than molten salt
• Molten salt:
  • maintenance to avoid plugging
  • External heat needed to maintain temp above 260 °C
  • 28,000 tons --> for 7.5 hours of storage
  • 25.2 million dollars for storage medium
• This research:
  • Electric heater chosen as heat input
  • Heat by heater -->to heat exchanger through Heat Transfer Fluid (oil)
  • Oil -->in an oil tank, pumped through pipes to heat exchanger
  • Temp sensors--> monitor sand temp change
  • Charging: Sand heated to desired temperature (150 °C)
  • Storing: sand thermal energy retention over time
  • Discharging:
    • Cold oil -->through pipes to absorb sand heat
    • Thermoelectric generator--> thermal energy to electrical energy

What Is a ‘Sand Battery’?^[11][edit | edit source]

• First commercial sand battery: In Kankaanpää, Western Finland (max temp:600 ℃, can be higher though)--> integrated into a district heating network operated by Vatajankoski (Green energy supplier)
  • In residential and commercial buildings (homes & swimming pool)
• Structure:
  • Insulated silo of steel housing filled with sand & heat transfer pipes.
  • Automation components, valves, a fan, & heat exchanger or steam generator.
• Heating:
  • Electricity from the grid or local production from wind and solar.
  • Charged during periods of clean and cheap electricity availability.
  • Electrical energy -->heat air with electrical resistors --> via a closed-loop air-pipe--> circulate it through heat transfer piping--> to heat storage
• Extraction:
  • Blowing cool air through pipes--> heat up
  • used to convert water into process steam / heat district heating water in an air-to-water heat exchanger.
• Stay hot for months, typically charged and discharged in 2-week cycles
• Best range of use when charged and discharged 20 to 200 times per year
• In "Polar night energy":
  • 600 °C, 10GWh, 100MW
  • 36% of industrial heating demand can be provided by sand battery (now is relying on oil and gas)
  • can save 100 Mt/year carbon mono oxide in 2030
  • can supply power for about 10,000 people
• 30% of solar/wind--> direct use, 70% stored as heat, less than 10% need for external energy for the whole year

Climate change: 'Sand battery' could solve green energy's big problem^[12][edit | edit source]

• Finland long border with Russia and halted gas and electricity supplies due to Finland joining NATO -->Concerns over heat and light sources during long, cold winters
• World first fully working sand batteryinstalled by Finnish researchers-->developed by "Polar Night Energy"
• power plant in western Finland --> 100 tonnes of sand inside a grey silo
• Difficulty in efficiently converting stored heat back to electricity.

Sand Battery For Thermal Storage^[13][edit | edit source]

• Batsand: Thermal battery with heating generator and sand vessel.
• bring hot and fresh sand directly to the home
• Charge (with solar panels) in summer--> heating / cooling when needed
• potential to return investment in 4-6 years
• combine with solar panel --> Can disconnect from grid
  • Rated Power: 1:14 KW, 2: 25KW
  • Battery Capacity: 1: 12000 KWH, 2: 21000 KWH
  • Suitable Home Size: 1: 300-600 m², 2: 500-1200
  • Size: 1: 140 cm x 72 cm x 55 cm, 2: 185 cm x 85 cm x 72 cm
  • Weight: 1: 142 Kgs, 2: 174 Kgs

How a Sand Battery Could Revolutionize Home Energy Storage^[14][edit | edit source]

• University of Michgan: 30% of total US residential enery use--> dedicated to heating (water heating:13%)
• US Lawrance Berkeley National Laboratory: 1/5 of energy produced in US--> building thermal load
• DraKE landing solar community-->2012: 96%, 2015, 2016: 100% of their yearly heating from solar
• TES: good round trip efficiency (RTE) rates (% of electricity into storage)--> 100% RTE: every stored energy can be used; thermodynamically impossible
• lead acid:70%, Li ion: 90%
• sand: low specific heat, high density: large storage of thermal, no chemical reactions: no maintanace, above boiling water
• heat sand with solar-->move to home with air
• challenge: size--> Batsand ($7700-increase to $19000 with installation, store energy at 92% efficiency with 94% RTE) is in small size (40m^3), under ground-->300-400 m^2 building, 10680 kW/h with +30 kW solar
• Newton Energy Solution (NES) ($5300-6400, 95% RTE)--> between TES & water heater & buffer tank--> water heater already a TES (but can't turn heat to electricity) water volume of 590 mm x 1650 mm (214 L)--> 20 kWh (can heat 600 L tap water to 40 °C &, 320 L--> 29 kWh
• the efficiency drop to 50-70% when heat to electricity

DIY Sand battery HEATER. Over 599f simple to make^[15][edit | edit source]

• Equipment:
  • 30 L steel tub
  • water heating element--> 300W 12v
  • hardware sore sand (play sand)--> 5-8 kg
  • ventiliser is required
  • watt meter
• Method:
  • Fill half way
  • put element in center
  • connect the w meter to the element wire
• in 40 min--> 179°C, in 50 min--> 290 °C

Sand Energy Storage System for Water Heater[edit | edit source]

• Demand for new and effective storage materials.
• Use of sand, abundant in Jordan, as a storage material.
• Silica sand predominant in southern Jordan, comprising 95.5% to 98.31% SiO2
• Specific heat capacity of silica sand: average 830 J/kg°C
• Energy stored proportional to temperature rise, specific heat capacity, and mass of medium.
• Solar Radiation in Jordan:
  • Yearly average: 2080 kWh/m2.
  • More than 300 sunny days annually.
  • Average daily radiation: 5.7 kWh/m2, with 8 hours of sun.
  • June and July have highest sun hours (almost 12 hours) and radiation values (8.2 kWh/m2).
  • December and January --> least sun activity ( 5 hours/day) and lowest daily radiation (2.9 kWh/m2).
  • Optimizing inclination angle between 10° and 60° increases yearly radiation to 2419 kWh/m2.
  • Most economical and effective inclination angle for PV system installation in Jordan: 30°.
  • Yearly radiation at this angle: 2330 kWh/m2.
• Jordan Weather:
  • Hottest month: July (average temperature 25°C/77°F).
  • Coldest month: January (average temperature 8°C/46°F).
  • Temperature fluctuation parameters: between 31°C and 4°C throughout the year.
  • Rare cases of extreme temperatures: up to 43°C and as low as -10°C in different regions of Jordan.
  • Energy storage design for night use as water heating source.
  • Standard hot water temperature: 70°C.
  • Average hot water use per person in Jordan: 40 liters/day.
  • Average household size in Jordan: 5 people.
  • Total water to heat: 200 liters (rounded to 240 liters).
  • Water mass: 240 kg.
  • Specific heat of water: 4.186 kJ/kg°C.
  • Required temperature: 80°C (including error).
  • Min temperature in January: 5°C.
  • Temperature difference (∆T): 75°C.
  • Energy required (Q):
    • Q=m×Cp​×ΔT=240kg×4.186kJ/kg°C×75°C=75,348kJ
  • Least sun hours per day in December: 5 hours.
  • Least average solar radiation per day in December: 2.9 kWh/m².
  • Energy demand: 75,500 kJ --> 20.98 kWh.
• Silica sand
  • Thermal conductivity: 0.33 W/m°C.
  • Average thermal heat capacity: 0.83 kJ/kg°C
  • ∆T: 75°C
  • m=Q/Cp​×ΔT​-->m=1,213kg.
  • Density of silica: 1,522 kg/m³ --> V= 1 m3
• System Design
  • Storage tank
  • Heat exchanger
    • D= 60 cm & H= 0.9 m
    • inlet top, outlet bottom

Solar Power Calculator for London, Ontario, Canada^[16][edit | edit source]

• yearly avg of solar radiation in London Ontario: 1547.32 kWh/m2
• avg daily radiation: 4.232 kWh/m2
• Months of highest sunny days: June 9.6h & 6.08 kWh/m2, July 10.1h & 6.11 kWh/m2
• Least sun activity: Jan 2.3h & 1.97 kWh/m2, Dec 2.7h & 1.67 kWh/m2

Climate and monthly weather forecast, London, Canada^[17][edit | edit source]

• Avg temp in hottest month: 25.5
• Avg temp in coldest month: -8.2