"Solar Systems in Practise" - Alan Kiff, ARK Specialist Services

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"Solar Systems in Practise" - Alan Kiff, ARK Specialist Services

  1. 1. Solar Systems in Practice Alan Kiff CEng MCIBSE Managing Director Portsmouth SBN Meeting – 25th November 2010
  2. 2. Contents • CASE STUDY - Solar Thermal Installation • CASE STUDY - Solar PV Installation • Conclusions
  3. 3. Solar Thermal • Generation of Hot Water by absorbtion of solar radiation Collector Pump Tank With only 3 components what can go wrong???
  4. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 14. PV – Stage 1 – Simulation (Results)
  15. 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. 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. 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. 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. 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. 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. 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?

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