1. Low Temparature Solar
Thermal Technology
Supervisor: Professor Herbert kabza
Prepared By: A.S.M. Abdul Hye
Energy Science Seminar

2. Energy-Resources word-wide
Energy Cubes: the Annual Solar
Irradiation Exceeds Several Times
the Total Global Energy Demand and All
Fossil Energy Reserves
Energy Resources word wide –
all Renewable

3. What is Solar Thermal?

Uses sun energy for thermal energy
Courtesy: xolar group

4. Thermal use of solar energy

5. Low Temperature Solar collectors


Flat plate collectors
Evacuated tube collector

6. Flat plate collectors
Courtesy: estif

7. Processes in a Flat-plate Collector

8. Glazed Flat Plate

9. Unglazed Flat plate collectors

10. Flat plate collectors

Pros are:
- cheaper to purchase.
-Non.tracking option
-Diffuse solar radiation utilization

Cons are:
- heavier to install (thereby potentially increasing installation costs).
- if any part of the panel is broken, a whole-panel replacement is required.
- less efficient than vacuum-tube.
- a greater collector area is required to match the same energy output as a
vacuum tube collector.
- dirt collects on the panel and over time reduces efficiencies further.

11. Evacuted-tube Collectors

12. Heat pipe evacuated tube array
Source: reuk.co.uk

13. Evacuated U-tube array
Source: reuk.co.uk

14. Evacuted-tube Collectors
Pros are:
-Very low heat loss.
-Eliminate convective loss.
-High efficiencies at high temperatures.
- light and therefore easier to install (hence reducing install costs).
- if one of the tubes breaks or fails, tube replacement is simple and cheap (the
whole panel does not need replacing).
- more efficient than flat-plate collectors by around 20%.
- smaller collector area required to match energy output of flat-plate
collectors.
- stay clean given the cylindrical shape of the tubes. Hence efficiency of panel
is maintained.
Cons:
- higher initial cost

15. Energy Conversion in the Solar
Collector and Possible Losses
Source: Wagner and Co, 1995

16. Energy Conversion in the Solar
Collector and Possible Losses
The sum of The reflectance ρ, absorptance α and
transmittance τ must always be equal to one.
ρ+ α+ τ=1.
The corresponding radiant powers are:
Φe=Φρ +Φα +Φτ= ρ .Φe+ α .Φe+τ.Φe

17. How much energy does a solar
collector provide?
Graph of
efficiency and
temperature
ranges of various
types of collectors
(radiation: 1000
W/m²)

18. Conversion Factor

19. Flat plate vs Evacuted tube
Optional

20. Flat plate vs Evacuted tube
Optional
source:
wikipedia
energy output (kW.h/day) of a flat plate
collector (blue lines; absorber 2.8 m2)
and an evac. tube collector (green lines;
absorber 3.1 m2.
A field trial illustrating the differences discussed
in the figure on the left. A flat plate collector
and a similar-sized evacuated tube collector
were installed adjacently on a roof, each with a
pump, controller and storage tank.

21. Efficiency Comparison between
collectors

22. Thermal Storage


Short-term storage systems.
Long-term storage systems.
Large storage systems can be:
• artificial storage basins
• rock caverns (cavities in rocks)
• aquifer storage (groundwater storage)
• ground and rock storage.


23. Different Types Of Heat Storage
There are different types of heat storage such as:
• Storage of sensible (noticeable) heat
• Storage of latent heat (storage due to changes in
physical state)
• Thermo-chemical energy storage.

Table Parameters of Low-temperature Storage Materials

24. Sytem layouts


Open loop
Closed loop

25. Open Loop Systems
Courtesy: Design handbook by
MPMSAA

26. Closed loop Systems
Courtesy: design handbook by
MPMSAA

27. Heat transfer medium Selections
Water
>Nontoxic and inexpensive .
>With a high specific heat, and a very low
viscosity, it's easy to pump
> Disadvantage: water has a relatively low boiling
point and a high freezing point

28. Heat transfer medium Selections
Non-toxic propylene glycol(in frost condition)
> Most common fluid used in closed solar water
heating system
> Ethylene and propylene glycol are
´´antifreezes´´
Dis Advantage: Most glycols deteriorate at very
high temperatures

29. Heat transfer medium Selections
Air
>Will not freeze or boil.
>Non-corrosive.
>Dis Advanteges:
>very low heat capacity.
>Tends to leak out of collectors, ducts, and
dampers.

30. Technology aspects


Systems for domestic hot water
Systems for space heating

31. Thermosiphon (or: natural flow)
systems

32. Forced circulation systems

33. Solar combisystem
• deliver solar energy to heat store (s)
with as low heat loss as possible;
• distribute all the heat needed to hot
water and space heating demand;
• reserve sufficient store volume for
auxiliary heating taking into account
minimum running time for the specific
heater;
• low investment costs;
• low space demand;
• easy and failure safe installation.

34. Freezing
Few common strategies to prevent damage from
freezing:
>Polypropylene glycol
>Drain down
>Pump circulation
>Insulation of piping
>Collector selection

35. HEAT DEMAND AND SOLAR
FRACTION
The heat demand QD=c.m.(θHW- θCW)
 the heat capacity of water [cH2O = 1.163
Wh/(kg K)] , the taken water mass m,
 the cold water temperature ϑCW and the
 warm water temperature ϑHW

36. Hot Water Demand of Residential
Buildings in Germany
Hot water
demand in
litres/(day and
person)
ϑHW = 60°C
Low demand 10-20
Average
demand
High
demand
Hot water
demand in
litres/(day and
person)
ϑHW = 45°C
15-30
Specific heat
content in
Wh/(day and
person)
600-1200
20-40
30-60
1200-2400
40-80
60-120
2400-4800

37. Hot Water Demand of Hotels, Hostels
and Pensions in Germany
Room with
bath
Room w/
shower
Hostels and
pensions
Hot water
demand in
litres/(day and
person)
ϑHW = 60°C
95-138
Hot water
demand in
litres/(day and
person)
ϑHW = 45°C
135-196
5500–8000
50-95
74-135
3000–5500
25-50
37-74
1500–3000
Specific heat
content in
Wh/(day and
person)

38. SOLAR FRACTION

It describes the share of the heat demand
provided by the solar thermal system.

solar fraction SF
Where

39. Solar Fraction as a Function of the
Collector Surface
Note: Location: Berlin, Collector Inclination: 30°, Heat Demand: 10 kWh/day

40. Economics
Well established market in Germany.
Overall upward trend of installed solar thermal capacity.
About 7.9 GWth solar thermal installed until end of
2008 in Germany
- over 1/3 of installed systems in EU.
Imporatnt factor for successful growth of solar thermal
market in germany is MAP.
20% raise per year though different in 2009.

41. Annually installed Solar Thermal
Power (0,7 kWth / m²) in Germany

42. German market for solar thermal
systems
Standard system for
DHWS
 Typical data for 4personshousehold:
 5-6 m² collector area
 300-400 l. solar storage
tank
 Costs ~ 4.000 – 5.000
Euro incl. Installation
 Market share: ~45%

43. Typical Solar Thermal CombiSystem





Combined solar thermal
system for DHW and
room heating support
8-15 m² collector area
500-1.000 liter combi
storage tank
Costs 10.000 - 15.000
Euro
Market share: ~55%

44. Installed Solar Thermal Power in
2007 (0.7 kWtherm / m²)
Optional

45. Flat Plate Collectors newly installed
in Germany in 2008
( Total : ~ 1.960.000 m2 )
Optional

46. Evacuated Tube Collectors newly
installed in Germany 2008
( Total : ~ 225.000 m2 )
Optional

47. German incentive program (MAP)
Paymerts provided by the program for solar
thermal systems
Payments base upon investement costs, not upon
energy output
 Related to installed collector area
>average investment per m^2 collector area: 900 €
> Average amount of incentive per m^2 Ac: 118 €
 Additional stimulation for innovations through bonus
incentives
 Overall volume of 196 million € in 2008


48. Paymerts provided by the program for
solar thermal systems
Including base and bonus payments: incentive
rate of 11.5 %
 Installations in private house provide 19% taxes
 Basically a tax decreases to 7.5% of system costs
 Over 1.3 GWth new solar thermal installations
in 2008 and most installed systems are DHW (4
m^2 collector areaand 300 litre tank)and
combisystems (11.5 m^2 collector area and 850
litre tank).


49. Summary

Solar thermal systems are cost effective at low
temperatures for water heating or cooking and
space heating.

50. References



Deutsches Institut für Normung e.V., DIN (1996) DIN
EN 1057, Copper and CopperAlloys – Seamless, Round
Copper Tubes for Water and Gas in Sanitary and Heating
Applications. Berlin, Beuth Press
Hahne, E.; Kübler, R. (1994) Monitoring and
Simulation of the Thermal Performance of Solar
Heated Outdoor Swimming Pools. Solar Energy vol 53,
pp9–19
Khartchenko, N. (1998) Advanced Energy Systems. New
York, Taylor and Francis Group

51. References





Kleemann, M.; Meliß, M. (1993) Regenerative Energiequellen.
Berlin, Springer
Lien, A. G.; Hestenes, A. G.; Aschehoug, O. (1997) The Use of
Transparent Insulation in Low Energy Dwellings in Cold
Climates. Solar Energy vol 59, pp27–35
Ladener, H. (1995) Solaranlagen. Staufen, Ökobuch Verlag
Manz, H.; Egolf, P. W.; Suiter, P.; Goetzberger, A. (1997) TIMPCM External Wall System for Solar Space Heating and
Daylighting. Solar Energy vol 61, pp369–379
Smith, C. C.; Löf, G.; Jones, R. (1994) Measurement and
Analysis of Evaporation from an Inactive Outdoor Swimming
Pool. Solar Energy vol 53, pp3–7

52. References




SPF Institut für Solartechnik (2002) SPF Info CD 2002 Thermal
Solar Energy.Rapperswil, SPF
TiNOX GmbH (2004) TiNOX Absorbers. Available at
http://www.tinox.com
Verein Deutscher Ingenieure, VDI (1982) VDI 2067 Blatt 4.
Economic Calculation of Heat-consumption: Installation of
Warm Water Supplies. Düsseldorf, VDI press
Wagner & Co. (Hrsg.) (1995) So baue ich eine Solaranlage,
Technik, Planung und Montage. Cölbe, Wagner & Co.
Solartechnik GmbH

53. Thanks!
I will be happy to answer questions