1. P20 Thermal energy storage with PCM for energy systems in buildings
S.Sawalha, S.Piscopiello, Tianhao.Xu

2. Overview of the project Specific project objectives
Implementation plan
Application focus in buildings
Descripition of the experimental test rig
Future work plans

3. Funding: 1,236 KSEK from Energimyndigheten
Project details
Project partners:
Vesam AB (including Swerod AB)
Danfoss Värmepumpar AB (Thermia)
Svensk Energi & Kylanalys AB
Funding: 1,236 KSEK from Energimyndigheten
Period: October 2015 to July 2018 (33 months)
Working group at KTH
Project leader: Samer Sawalha;
Senior researches involved: Viktoria Martin, Justin Chiu
Research engineer: Salvatore Piscopiello
PhD student: Tianhao Xu

4. Test at least three types of PCM for heating and cooling applications
Build a permanent test rig to investigate thermal storage units with PCM;
Experimentally investigate the performance characteristics of at least three thermal storage unit configurations
Test at least three types of PCM for heating and cooling applications
Identify the energy systems solutions for buildings and propose solutions integrating PCM thermal storage that save 10%-20% energy

5. Work packages 1-4
WP1: Design and build a test rig for PCM and thermal storage tank/unit (Currently working in)
WP2: Modelling of PCM tanks and heat exchange configurations (COMSOL or MATLAB).
WP3: Modelling of energy systems with PCM thermal storage (EES and TRNSYS).
WP4: Design and test the energy system with PCM thermal storage that has the highest potential for energy saving (Beyond time frame of project)

6. Energy systems will be investigated representing: Space heating (SP);
Energy systems for residential or commercial buildings
Energy systems will be investigated representing:
Space heating (SP);
Air conditioning (A/C);
Domestic hot water (DHW);

7. Average Single-family house in Sweden
Space heating
Average Single-family house in Sweden
Temperature range: 40/45 °C or 47/55 °C (EN 14825);
Heating load: maximum around 10 kW
PCM-TES application: shifting of heating capacity from daytime to nighttime with air-source heat pump
Achieve peak shaving;
Reduce dependence on back-up
Increase COP
Comparing to sensible heat storage – More compact and smaller

8. Connection to ongoing project (NxtHPG) in KTH
Space heating – One application example
Connection to ongoing project (NxtHPG) in KTH
State-of-the-art R290 heat pumps (air and ground source)
Performance curves of both heat pumps (already-tested) will be used for input of modelling energy system with PCM;
Comparisons between air source heat pump integrated with PCM-TES unit and ground source heat pumps:
System performance: SPF, etc.
Economic analysis: pay-back time, etc.

9. Connection to ongoing project in KTH
Space heating – One application example
Connection to ongoing project in KTH
Performance curves of both heat pumps (already-tested) will be used for input of modelling energy system with PCM;
Air-source heat pump
Ground-source heat pump

10. Commercial buildings in Stockholm
Air conditioning
Commercial buildings in Stockholm
Temperature range for chilled water:
7/12 °C for fan coil;
13/17 °C for chilled beams.
Cooling load: Maximum 25 W/m2 of building area
Cooling load occurs in summer & working hours
PCM-TES application:
For chillers: Peak load shaving & Size reduction
Better EER during nighttime – Increase total efficiency

11. Average Single-family house in Sweden
Domestic hot water (DHW)
Average Single-family house in Sweden
Supply temperature: 60 °C – Heated up from °C
Heating load: up to 1 kW – occurs at around 7:00 a.m.
Large load variation during a day
PCM-TES application: Utilization of exhaust air heat pump for heat recovery
Comparing to hot water tank storage
No advantage in tank size (80%)
Less priority
Reference: (a)

12. Phase-change temperature
PCM Product
PCM Product - Swerod
PCM Product used for tests – Overview
PCM Product name
Phase-change temperature
Latent heat of fusion C7
8°C
123 kJ/kg
C10
11°C
116 kJ/kg
C48
48°C
180 kJ/kg
C58
58°C
260 kJ/kg

13. Summary of applications with specific PCM
Priority
C48
Medium temp.
SH (40-45°C)
Single-family house with ASHP
High
C58
High temp.
SH(47-55°C) C7
A/C
in commerical buildings
Fan coil(7-12°C)
Chilled beams
(13-17°C)
C10
DHW
Single-family house with ExHP
Less
C21,C32…

14. PCM Thermal storage tank in real application
Charging
Heated up water from heat source (solar heat collector, HP, etc.)
Discharging
To heating systems in the building (radiators, underfloor heating, etc.)

15. Test rig Requirements for the test equipment
Flexibility in temperature
(-10 to +100 °C);
Flexibility in flow rate (different TS size and applications);
Temperature stability (with a variable heat/cooling capacity)
Ready-to-start (Stable conditions from the first moment that thermal storage unit is connected)
Different unit configurations (how the storage is connected to the load/source)
11/9/2018

16. Semplified scheme TES unit HP Hot brine tank Cold brine tank

17. Detailed scheme
Hot brine
tank HP
TES unit
Cold brine
tank

18. Two tanks (hot and cold)
Flexibility in temperature
Temperature stability

19. Flexibility in flow rate
Detailed scheme
Flexibility in flow rate

20. Separate heating/cooling waterborne system with tank
Heat exchanger
Separate heating/cooling waterborne system with tank
Allows the by-passing of heat exchanger if needed

21. Connection of different TES tank configuration
Detailed scheme
Connection of different TES tank configuration
Two levels of system boundaries T3 T1 T4 T2

22. Possibility to change flow directions in the tank
Four-way valve
Possibility to change flow directions in the tank

23. The configuration allows the thermal storage unit
Ready-to-start
The configuration allows the thermal storage unit
to be functioning when supply temperature stabilizes

24. To achieve project objectives:
Summary of proposed test plans
To achieve project objectives:
At least three different tank configurations:
With or by-passing HX;
Changing flow direction in charging/discharging (4-way valve)
Different tank size & PCM rods placement
At least three different PCM
C48/C58 for medium/high-temperature space heating application;
C7 and C10 for air conditioning in commercial buildings
C21, C32…for further exploration in other applications

25. To achieve project objectives:
Summary of proposed test plans
To achieve project objectives:
At least four energy systems with integrated PCM-TES
Single-family house space heating with air source heat pump; (medium and high temperature application)
Commecial buildings air conditioning in summer
Using fan coil;
Using chilled beams.
(Less priority) DHW production in single-family house; Extra subcooling

26. Test rig: Final selection of components; design of hydraulic loops;
From now on…
Test rig: Final selection of components; design of hydraulic loops;
Test matrix:
Based on different heating/cooling applications and different PCM products (phase-changing temperature):
Capacity & temperature level & flow rates to be designed;
Computer simulation models to be defined – Tank characterization and energy system simulation

27. Thank you for your attention! Any questions?