15.07.2015   EuroSun2008-5

. Overview of technologies and status for solar heat

J.-C. Hadorn

Groupe Bemey — BASE Consultants SA, Geneva, Switzerland
ichadom@baseconsultants. com

Abstract

This paper presents the state of the art of the main storage solutions for storing solar heat. Keywords: heat storage, seasonal storage, water tank, duct storage, aquifer, solar

1. Storage of heat : overview of classical and advanced materials

Water is a good candidate for all kind of heat storage in the range -30 to 200 C. Table 1 compares basic materials and shows that water has a high volumetric heat capacity.

Thermal

conductivity

@20C

Density

@20C

Volumetric

heat

capacity

@20C

Thermal diffusivity @20C ‘

W/mK

Kg/m3

10+6J/m3

10-8 m2/s

Air

0.025

1.29

0.001

1938

Water

0.6

1000

4.180

14

Ice

2.1

917

2.017

104

Aluminium

237

2700

2.376

9975

Copper

390

8960

3.494

11161

Stainless Steel

16

7900

3.950

405

Concrete

1.28

2200

1.940

66

Marble

3

2700

2.376

126

Glass

0.93

2600

2.184

43

PVC

0.16

1300

1.950

8

PTFE

0.25

2200

2.200

11

Sand (dry)

0.35

1600

1.270

28

Sand (saturated)

2.7

2100

2.640

102

Wood

0.4

780

0.187

214

Cork

0.07

200

0.047

150

Foam glass

0.045

120

0.092

49

Mineral insulation materials

0.04

100

0.090

44

Table 1: Thermal properties of some materials for sensible heat storage

Heat storage candidates

image010

BASE CONSULTANTS

Figure 1: Energy density of some storage material: 3 ranges emerge as competitors to water: PCM, Sorption and Chemical storages.

New solutions have been recently investigated in Task 32 (Figure 1). There is a lot to of potential for medium temperature solutions but as we will see new materials are urgently needed.