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

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

  • Solar Systems in Practice
    Alan KiffCEng MCIBSE
    Managing Director
    Portsmouth SBN Meeting – 25th November 2010
  • Contents
    CASE STUDY - Solar Thermal Installation
    CASE STUDY - Solar PV Installation
    Conclusions
  • Solar Thermal
    Generation of Hot Water by absorbtion of solar radiation
    Collector
    Tank
    Pump
    With only 3 components what can go wrong???
  • 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?
  • Solar Thermal - Pump
    Is the pump powerful enough?
    How fast is the solar fluid moving?
    Has the system been correctly commissioned?
    Flow Meter
    PUMP
  • Solar Thermal - Collector
    What’s wrong with this picture?
    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?
  • 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
  • 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
  • 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!
  • 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
  • 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.
  • 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
  • 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
  • PV – Stage 1 – Simulation (Results)
  • 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
  • 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
  • PV – Stage 2 Financial Analysis
  • 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.
  • 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
  • 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!
  • 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?