preparing the windgenerator installation; here foundation for tower, stay wires, and winch.  Not visible: digging in 200m of underground cable (any place nearer to the house was too sheltered).

Data: 2.5m propeller diameter, rated 1kW at 11m/s, producing 24VDC. Tiltable tower 6m high (one length of standard galvanized steel pipe).

The system feeds 24VDC lights, plus 230VAC loads via an 800W sine wave inverter.  Initially, we used a 2nd hand 24v 400Ah forklift battery.  Excess electricity (usually on a windy day) diverted into a 700W wall heater (DC). 

The average electricity production of the system was sufficient.  However, due to the changeable nature of the input, especially from wind, storage capacity was not always sufficient, therefore we often adjusted consumption to the input.  During the first year, the house was still connected to the ESB network (on a changeover switch), but we used this option very seldom.

The forklift batteries seemed to get to the end of their life after year 1.

Addition of another 500Wp solar PV panels. 

Replacement of forklift batteries with tubular plate liquid lead acid 'OPzS' batteries (24V 950Ah, acidity 1.24kg/l); this type is traditionally used in standby power supplies e.g. for hospitals or airports.  They have a realistic life expectancy of 15 years; similar to the now common LifePO batteries, but less than half their price. 

These improvements made the system less dependent on the actual weather, even though storage capacity is still limited to a few days.

Changeover relay on the fridge/freezer to make sure they cannot start at the same time.  (Fridges and freezers easily use 1kW for a split second when starting, even though running power may only be 100W or less.) 

And finally: Disconnection from the ESB network.

Shaft of windgenerator broke; machine fell to the ground.  This was most likely caused by turbulence from a high 'step' in the land close to the windgenerator. Luckily, only one blade was damaged close to its root, so by cutting some 4 inches off each blade, the machine was still useable.  After this, we lengthened the tower from 6m to 9.5m; this brought the propeller out of the turbulent zone.  And, despite the slightly smaller diameter, output was now better than before. 

 Apart from this major 'meltdown', some maintenance was necessary on the windgenerator over the years, mainly on the tail hinge bushings.

The sharp price drop for PV panels allowed a doubling of the installed capacity to 2.1kWp.  This was mainly done for a steadier supply in calm spells in winter, even though on very dull days, the contribution from PV could still be very little.  At the same time, it made supply in the remainder of the year (February to October) very comfortable, enabling the use of e.g. electric kettle and electric oven, saving on bottled LPGas.  On sunny days, quite a lot of electricity is diverted into the wall heater (mentioned above) and into a new 700W immersion heater.  While most water heating is being done by separate solar water heaters, the immersion heater makes sure that the top of the cylinder is always at least at shower temperature.

 We also added a larger 2.5kW inverter, allowing the use of rather large power tools (electric chainsaw, woodsplitter). 

Finally, another 900Wp of PV panels installed free-standing. 

What is the payback time for such a system?  In our case around 15 years.  This may seem long - but would a bank pay 7% interest on a deposit?  And, perhaps more importantly, it is an insurance against future energy price hikes like we now experience in 2022. 

 Generally, off-grid is the more economical option for low electricity demand, while on-grid is more economical for high demand. 

 Maintenance cost should also be taken into account.  If you cannot maintain the system yourself, this could become quite expensive for wind generators.

If I started from scratch again, would I do anything different?  Hardly.  Perhaps I would use double the PV capacity instead of a wind generator, however at our 54 degrees latitude, I am not sure.  The extra winter power from wind energy is surely welcome, however at the expense of much higher maintenance. 

And perhaps use the larger inverter from day 1 - however having two inverters increases reliability in case that one breaks down.

Do I regret having gone off-grid?  No!

More questions?  contact us by email: solarpeters att gmail dot com