Modernisation of the very remote property included the addition of two bathrooms and a utility room in which a 2.2kW washing machine would be installed. A combined fridge freezer and microwave would also join the list of electrical appliances never before seen at the location. All of the 5 bedrooms, 2 new bathrooms, kitchen, lounge and utility rooms would have heating and lighting installed. 

We started by modelling the forecast electricity demand across various scenarios including both Winter and Summer occupation with between 2 and 8 persons and then Winter and Summer periods when the property was unoccupied and in “shutdown mode”. 
Central to the system is an SMA Sunny Island 6.0 Off Grid inverter. This is supplied by a 4kW roof mounted solar PV system which is backed up by a 10kVA Stephill Super Silenced diesel generator located within a ventilated canopy some 15m from the house. A Rolls FLA 48V 546Ah capacity battery bank is also connected into the Sunny Island inverter. 
Our calculations indicate that during Summer occupation the solar PV will supply over 80% of the demand. The generator will be required only when there are successive poor light days and the solar PV output is reduced. The generator is fitted with a Deep Sea Electronics Auto start module linked directly to the Sunny Island inverter. When the remaining battery capacity falls to a pre-set level then the generator is automatically started to recharge the battery to full capacity before being shut down again. The Sunny Island is programmed to not start the generator between 22:00 and 07:00 unless the battery state of charge reaches 45%.
A load shedding contactor is in the electrical power circuit which supplies the heavy loads such as the washing machine and microwave etc. In the event that the remaining battery capacity falls to a pre-set level and the generator fails to start, the contactor will open and isolate this circuit. The remaining battery capacity is then preserved for lighting, communications and heating. As an additional safeguard and in case of emergencies the communications suite has a separate battery backup supply which will maintain the modems, router and telephone for 8 hours following a total system power failure.
An SMA Cluster Controller provides the communication link between the Sunny Island inverter, the SMA 5000 solar PV inverter and the internet router which is enabled by a TooWay Broadband Satellite connection. All required system information including solar PV output, battery capacity, released energy and generator run time is uploaded to the Sunny Portal every 2 hours and generates a daily report which is emailed to the Westflight monitoring team and the clients on a daily basis. Any fault indications are emailed directly to Westflight should they arise.

A VoIP (voice over internet protocol) phone system enables our clients to both make and receive telephone calls over the internet connection with no perceptible drop in voice quality of transmission lag.