1. Solar Systems in Practice
Alan Kiff CEng MCIBSE
Managing Director
Portsmouth SBN Meeting – 25th November 2010

2. Contents
• CASE STUDY - Solar Thermal Installation
• CASE STUDY - Solar PV Installation
• Conclusions

3. Solar Thermal
• Generation of Hot Water by absorbtion of solar
radiation
Collector
Pump
Tank
With only 3 components what can go wrong???

4. Solar Thermal - Tank
• What’s wrong with this
picture?
– Blue tank is the new
solar tank
– Other tank is existing
• Integration into existing
systems
• Storage capacity
– Matched to load?

5. Solar Thermal - Pump
• Is the pump powerful
enough?
• How fast is the solar fluid
moving?
• Has the system been
correctly commissioned?
PUMP
Flow Meter

6. Solar Thermal - Collector
• Orientation
– Taken at lunchtime so
why is the sun on the
other side of the roof?
• Type
– Overheating
– Stagnation
• Number
– Too Few / Too many
• Does Collection profile
match usage profile?
What’s wrong with this picture?

7. Solar Thermal – Case Study
• System purchased direct from installer
• No evidence of design calculations
• Client questions system performance after 18
months
• 5 evacuated tube collectors on exposed South
facing roof at 35° pitch.
• Good quality pump and control station

8. Solar Thermal – Case Study
• Collector selection and location
– Good quality tubes
– Correct orientation and pitch
– Right number of tubes
BUT
• three storeys between collector and tank and
VERY long poorly insulated pipe run
• Collector had overheated due to poor location of
expansion tank

9. Solar Thermal – Case Study
• Pump
– Flow rate set to 5 litres / minute – too fast
– Pump slightly undersized for “head”
• Tank size
– 315l tank used for preheat of existing 400l tank
– House has 4 bathrooms but typically only 2 occupants
– Any solar heat collected will never get to the tap!

10. Solar Thermal – Case Study
• How we proved the system wasn’t working
– Data-logging of flow-rates and temperatures
– Collector had hydraulic locked – fluid short circuiting
through expansion loop
– Proved no heat transfer between collector and tank
• How we fixed it
– Removed original cylinder and used solar cylinder as
intended
– Re-commissioned flow rates and pump speeds
– Installed Auto air-vent and relocated expansion
vessels

11. Solar Thermal - Conclusions
• Insist on seeing design calculations
– Collector type and sizes
– Tank sizes
• Insist on a formal commissioning report
USE AN INDEPENDENT CONSULTANT !!
Unless the installation is small scale domestic
DON’T rely on the installer.

12. Photo-Voltaic
• Client considering PV as an investment
• Maximise payments under FIT
• Installation on an outbuilding rather than main
house
Key Features
• Own electricity meter
• South facing, 45° roof pitch
• Room in roof
• 5000 kWh/yr electricity use

13. PV –Stage 1- Simulation
• Different panels (makes and models) and
inverters
• Different numbers of panels
Transient Simulation
(TRNSYS16)
• Product specific performance
data
• NASA Weather data
•10 min time steps

14. PV – Stage 1 – Simulation (Results)

15. PV – Stage 2 Financial Analysis
“Benefit” from the panel =
Feed In Tariff + Export Tariff + Electricity Offset
41.3 + 3 + 12.5
Electricity Use = 5000 kWh per year
PV output = max. 1910 kWh per year
Therefore
Export = 0 kWh, Offset = 1910 kWh, FIT based on 1910 kWh
Majority of income is due to FIT

16. PV – Stage 2 Financial Analysis
• Done for each panel / inverter combination
• Costs based on manufacturer prices +
installation costs
• Lifetime analysis includes panel degradation in
accordance with manufacturer warranty

17. PV – Stage 2 Financial Analysis
-£30,000.00
-£20,000.00
-£10,000.00
£-
£10,000.00
£20,000.00
£30,000.00
£40,000.00
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Cumulative Cash Flow - Yingli with SMA inveter
Yingli 8
Yingli 6
Yingli 4

18. PV – Stage 3 – Technical Feasibility
STRUCTURAL SURVEY
• Each panel weighs around 20kg
• Mounting frames weigh around 10kg per
panel
• Survey revealed that the structure could
support the additional weight BUT only if the
joist fixing bolts were replaced.

19. PV – Stage 4 - Quotes
• To qualify for FIT the system must be installed
by MCS accredited installer.
• Specify the exact makes and models
• Quotes obtained for installation + remedial work
to roof.
• Recalculate the payback period

20. PV - Conclusions
• Selection of the panels is critical to project success
• Inverter losses must be factored in
• Panel degradation must be factored in
• Modelling should be accurate – don’t use SBEM
– Initial feasibilty should be done in RETScreen
– Detailed simulation (TRNSYS) is worthwhile
• Panels and frames are
– Heavy
– Increase wind sheer
have a structural survey done!

21. CONCLUSIONS
• There are poorly installed Solar Thermal
Systems
• There are accurate modelling tools
• The FIT and RHI are significant
• Do you trust your installer to act as consultant?