Magneto caloric materials for energy efficient heat pumps

Ekkes Brück, Delft University of Technology,

Fundamental Aspects of Materials and Energy

World population

year

popu

lati

on /

mill

ion

11 billion

World population and energy use Country Population

(million) Electricity kWh/cap)

Energy (Mtoe/cap)

World 6958 2933 1.88

OECD 1241 8226 4.28

China 1351 3312 2.03

Asia 2313 823 0.69

Africa 1045 592 0.67

IEA, Key world energy statistics, 2013

data from 2011

Last 160,000 years (from ice cores) and the next 100 years

Time (thousands of years) 160 120 80 40 Now

–10

0

10

100

200

300

400

500

600

700 CO2 in 2100

(with business as usual)

Double pre-industrial CO2

CO2 now

Temperature difference

from now °C

CO2

conc

entr

atio

n (p

pm)

Source: IPCC

CO2 concentration

Energy Information Administration (EIA) Annual Energy Outlook, 2009

Residential energy consumption

BSRIA Building Services Research and Information Association

World Air Conditioning market

•>10% growth •Columbia, Brazil, Nigeria, India, Vietnam and Indonesia

Refrigerant Chemical formula

Atmospheric lifetime (years)

GWP ASHRAE safety group

ODP

R22 CHClF2 12 1810 A1 0.05 R134a C2H2F4 14 1430 A1 0 R290 CH3CH2CH3 12 3.3 A3 0

R404a 44±2% C2HF5 52±1% C2H3F3 4±2% C2H2F4

40 3920 A1 0

R407c 23±2% CH2F2 25±2% C2HF5 52±2% C2H2F4

16 1774 A1 0

R600a CH(CH3)2CH3 12 3 A3 0

Frequently used Refrigerants

GWP Global Warming Power ODP Ozone Depletion Power A1 no flame propagation, A3 highly flammable

Nickel metal ΔB = 1.5 T ΔT = 0.7K

Magnetocaloric effect 1917 Weiss & Piccard

Magnetic cooling: Debye and Giauque 1926

61g Gd2(SO4)3·8H2O, ΔB=0.8T, 1.5K →0.25K Nobel prize 1949

spins lattice

Basic magnetocalorics

E

Two energy reservoirs

E

Basic magnetocalorics

spins lattice

Example UVic prototype μ0H ~ 1.4 T, f ≤ 4Hz

•CES 2015 Las Vegas

Magnetic heat pump

Which material is most suited for use? •https://www.youtube.com/watch?v=jnl9m0rSE7U

Giant MCE Materials @ room temperature, @ ∆B = 1 T (available with permanent magnets)

toxicity cost + availability

Figure of Merit • Refrigerant capacity RC = ΔS·ΔT Measure of net work in reversible cycle. Often used, but not a good FoM.

Wood & Potter Cryogenics 1985

• Coefficient of Refrigerant performance CRP

Dimensionless Figure of Merit which can be used to compare different materials even gas compression

Desired Magnetization processes

Material with field induced first order phase transition.

Replace Fe with Mn and Si for As magnetic response of MnxFe2-xP0.5Si0.5 in 1T

Mn content strong reduction in hysteresis followed by other structural transformation

Same effect in 2T as earlier in 5T Huu Dung et. al. Adv. Energy Mat. (2011)

Partial phase-diagram

Electronic structure

Fe (0μB)

Mn (2.6 μB)

Fe (0μB)

Mn (2.6 μB)

Fe (0μB)

paramagnetic Closer look at the layers

Fe (P,Si)

Mn (P,Si)

Fe (P,Si)

Mn (P,Si)

Fe (P,Si)

Electronic structure

Fe (0μB)

Mn (2.6 μB)

Fe (0μB)

Mn (2.6 μB)

Fe (0μB)

paramagnetic Closer look at the layers

Fe (1.5μB)

Mn (2.8 μB)

Fe (1.5μB)

Mn (2.8 μB)

Fe (1.5μB)

ferromagnetic

MnFe0.95P0.595B0.075Si0.33

From MB(T)

F. Guillou et. al. Adv. Mat. (2014)

B 0.075 B 0.0

MnFe0.95P0.595B0.075Si0.33

Cyclic insertion and extraction in 1.1 T field Resulting ΔT

Sample ∆Str = L/Tc (J kg-1 K-1)

∆M (A m2 kg-1)

dTC/dB (K/T)

Transit. Width

(K)

∆S MCE B=1T

(J kg-1 K-1)

Boron 7.5% 21.1 65 4.4 ±0.2 7.5 -10.5

Mn rich 29.8 61 3.2 ±0.2 8.0 -10.5

-36% +40%

MnFe(P,Si,B) vs Mn1.25Fe0.7P0.5Si0.5

Reminder: MnFe(P,Si,B) Mn1,25Fe0,7P1/2Si1/2

+40% !!

+6%

CRP for different compositions

Consequences of no volume change

Mn1.3Fe0.7P0.5Si0.5 ΔV/V ≤ 0.2 %

MnFe0.95P0.587B0.078Si0.34

ΔV/V ≤ 0.05 %

Summary: MCE materials @ 1T Room T. ∆B=1 T

∆Smax (J kg-1 K-1)

∆Tmaxad

(K) CRP

Gd ʘ 3 2.5 0.17

LaFe11.38Mn0.36Si1.26H1.52 * ~10 2.6 ~0.4

Mn1,25Fe0,7P0,51Si0,49 10.5 1.9 0.47

MnFe(P,Si,B) 10 2.8 0.62

Not toxic Not expensive (Boron only 0.5 wt%)

Good mechanical stability Easy tunability of TC

Mn/Fe + P/Si + B, from 130 K to 450 K ʘ Dankov et al Phys. Rev. 57 (1998)

* Morrison et al Int. J. Ref. 35 (2012)

TU Delft: N.H. van Dijk, F. Guillou, L. Caron, G. Porcari, H. Yibole, X.F. Miau, N. Van Thang, M. Boeije, K.H.J. Buschow Radboud Universiteit: R.A. de Groot, P. Roy, G.A. de Wijs BASF: L. Zhang, B. Reesink

Thank You for Your attention

Optimisation of MnFe(P, Si, B)

Recommendations to design MnFe(P,Si,B): B content as high as possible (from 0.06 to 0.09) Si between 0.3 and 0.4 then TC adjustment with Mn and Fe from Mn1.3Fe0.7 to Mn0.7Fe1.3 -(P,Si,B)

Control of TC

# Magnetic refrigeration: Room T.

# Regenerator: Stacking of materials with different TC

# Cryogenic operation/Gas liquefaction: as low as possible

# Thermomagnetic generator: at least up to 400 K

MnFe0.95P0.583B0.077Si0.34

Mn/Fe ~ 1 Si ~ 1/3

Tuning the latent heat with Boron

DSC

MnFeP1-yXy

Hexagonal Fe2P type of structure

Bacmann, JMMM 1994

Space group: P62m

Mn 3g sites

Fe 3f sites

P/As 1b & 2c sites

_

Temperature dependence of Magnetization

Step-like

transition

first order

but very little

hysteresis

Tegus et al. Nature 415

Comparison of magnetocaloric effect in different materials

Entropy change

concentrated in

relevant T interval

Tegus et al. Nature 415

•0-2T

•Fujita et al Phys Rev B 67 (2003) •Hu, et al, JAP 97 (2005)

Giant MCE Materials

Magnetocaloric material

Sample preparation MnFe(P,x)

Starting Fe, Mn2As3, Ge, Si, Mn & P

mechanical alloying

sintering 1000oC

annealing 800oC

Ball milled material SEM analysis

Homogeneous

Alloy formed

XRD Fe2P phase

Magn. phase trans.

MnFe(P,Si) first samples

Large hysteresis

MnFeP0.6Si0.4

Magnetization isotherms

Metamagnetic transition with little hysteresis

Magnetic response in different fields

Sharp transition with little hysteresis

Typical refrigerator and refrigeration cycle