Renewable energy systems

from Castaway 2000 TV program

NOTE: I designed and installed this system with some labour input from the 'castaways' themselves.  This page was orignally written as a description of the equipment for sale at the end of the project.  The castaway renewable energy systems are no longer on the market.    But I am leaving the details here on the web in case they are of general interest.

The castaways' electricity came from two renewable sources: wind and hydro turbines.  Energy was stored in a battery, and then converted to 230 volts mains power by two inverters - one for normal use, and one for backup.  These are Trace SW series inverters, with many sophisticated software functions built in - including the ability to automatically start a generator (not used on Taransay, where the generator was hand started if necessary).   The backup inverter was also used to feed surplus power to heaters and prevent the battery from overcharging.  There is a changeover switch to allow easy transfer of the load between inverters and also (in the worst case) to a backup generator.  This switch was never needed.  The inverters synchronised with the generator automatically (when it was started up), and use it to charge the battery when necessary.

The wind turbine is a 2.5kW 'Proven' with 48 volt output, on a 6.5 metre free standing tower (see bottom of page for detailed pics of tower).  The tower comes complete with a Tirfor rope hoist for easy erection.  There is a kit of spares for the turbine, including blades and springs.  Heavy armoured cable takes the power down to the battery room.  Adjacent to the battery room is a plant room, with the 'controller' for the wind turbine.  This converts the 3 phase AC power form the wind turbine to DC, and monitors the battery voltage.  If voltage indicates that the battery has reached its maximum optimum charging rate, then surplus current is diverted to a special (multiple element) immersion heater.

The battery comprises 8 quantity, 12 volt units, each with 230 amphour capacity (at the 20 hour rate), giving a total of 460 amphours at 48 volts nominal.  This represents about 15-20kh units of usable electricity storage.  Battery charge level is displayed as a % on an amphour meter panel, for easy interpretation by the castaways.

      The hydro turbine is a 'stream engine' from Energy Systems and Design
  <>  It has two nozzles which can be used to control water usage.

At present it has 440m of 5 inch pipe (MDPE which could be re-used with new fittings) and a mile of high voltage cable (6mm 3-core steel wire armoured).  There is a 3-phase transformer at the battery, to step the voltage down to 48 volts for battery charging.  The existing site has 30m head (drop from intake to outlet).  It functions with between 1 and 8 litres of water per second, as available.

 This turbine would supply all the electrical needs of a typical home, from a stream one mile away, producing up to 1kW charge rate into a 48 volt battery, (depending on the available water),

Here is a rough guide to the NEW costs of the above items
battery 2320
immersion heaters 105
amphour meter 205
Switch boxes 168
Inverter 3.3kW 2361
inverter 4.5kW 2697
wind turbine 3385
tower 1580
Tirfor 360
Cable 259
Spares 521
controller 855
hydro and transformer 2400
Pipe 2500
cable 1530

Liz (a castaway) reports to me on the state of the system on 6th December 2000 as follows:
The hydro & windmill have worked fantastically well throughout the year (apart from the lack of water during the summer).
- windmill - great no problems whatsoever
- hydro - started working again when the water
levels rose in September.  Have got 13 amps continuously from it since then.  fuses blew once on the hydro, not sure why - maybe the unit got wet - but replaced them with new ones and it has been fine since.
Diesel - used hardly at all except for the odd windless day during the summer & when the fuses went on the above for a couple of days.  The diesel supply we started with has lasted all year.
So all in all the system's worked brilliantly.



wind turbine tower details: