Life/Work Balance - Alternative Energy at Grandtully

Solar array
There are two types of solar panel in general use, ones that heat water, called solar thermal, and ones that generate electricity. The electrical ones are known as photo-voltaic, PV for short.

PV panels get their name from the action of light on a cell made of silicon, and it’s this type that make up the array at Aultbeag. PV panels come in various shapes and sizes – they can even be flexible or see-through – but the Sharp panels in the Aultbeag array are conventional aluminium framed modules made up of several hand-sized cells connected together. They are also currently about the most economical means of generating electricity from PV.

Each of these particular panels produces electricity at somewhat over 20 volts and up to about eight amps, so their rated output is 162 watts each. To enable the array to be connected to the electrical grid – the mains – the direct current from the panels has to be converted to AC, and with a quality suitable for the grid.

This is done by a gadget called an inverter, which uses the mains signal to match the grid voltage and frequency. An important feature is that if the signal fails (that is if the mains power goes off) then the inverter shuts down in less than a second. So anyone working on the mains system won’t be at risk from the PV system continuing to generate.

The inverter needs a fairly high input voltage from the array, so at Aultbeag two strings of 12 panels are connected in series, giving a total size for the installation of nearly four kilo-watts peak power. In fact, on a sunny day, the array will put four kW AC into the mains, the maximum that can conveniently be fed into a single AC phase.

If the Applebys aren’t using as much as the system is producing, then the surplus automatically goes into the grid and forms part of the supply of the next nearest electricity user. Because the supply is local, the transmission losses of conventional grid supply are avoided - a small extra ‘plus’ for small scale generation.

In addition, the whole array is mounted on a frame of locally grown, treated larch. The use of timber avoids the use of energy-intensive metals and concrete foundations and also, for the life of the frame, ‘fixes’ the carbon that is taken in by the growing trees.

A House Designed for Wildlife
In designing the house and workshop at Grandtully Malcolm Appleby wanted to consider the needs of the wild creatures in the locality. The building becomes a large pipistrel bat roost over the summer and swallows continue to nest in the outside workshop.

This year swifts were checking out the eaves – possibly displaced from their regular nesting site in nearby conversions. The bats were so numerous that the amount of droppings started to cause problems. After consulting SNH, Malcolm designed an extra layer of larch panelling to go on the outside of the main structure of the house, not only giving the bats more room, but providing holes for swifts.

Burnside Joiners took on the work and quickly completed it before winter sets in – the result looks good and improve the design of the original structure.

Phillipa told Comment: “We wait with excitement to see who takes up residence in the Spring – midgies beware! Other birds that nest in the house include wrens in a spare swallow nest, great tits and blue tits in crevices and a spotted flycatcher in a nestbox, now relocated to a safer place.”