A year of solar heating

The unseasonably good weather at Hillside over the past few days, with clear blue skies from dawn to dusk and temperatures around 25C, is a very pleasant suprise. Along with giving us a welcome last taste of summer that wasn't very forthcoming in July and August, it means we can eke some more use out of the solar hot water system.

2011 has been our first full year of using solar hot water. Whilst we'll get a few more good days from the unexpected sunshine, we've now had most of the useful sunshine for the year so now is a good time to review how the system has performed.

This year has seen us generate around 2,200 kwhs of hot water from the sun, and we expect it to reach 2,500 before the year is out. If we had used gas to generate the same amount of hot water it would have cost us approximately £92 on a typical tariff. However, we don't have gas in the village so would have to use either electricity, oil or wood pellets. The equivalent costs for these would be £315, £145 or £130 respectively. As wood pellets are our fuel source we'll use that in our calculations.

Our Navitron, self-installed, 30 tube solar thermal system cost just over £1,000 excluding the twin coil hot water cylinder which we bought separately. If you bought the complete kit from Navitron it'd set you back £1,600.

So, using the figures calculated above and the cost of the complete kit, a simple payback calculation shows the solar thermal system will pay for itself in 12 years. I must admit I'm slightly disappointed by this as I thought it'd be less. However, you could take the view that before the renovation project we would've been using oil, and we had to replace the cylinder anyway so the true payback is £1000/£145, and is a much more satisfying 6.9 years.

Even the 12 year payback period shows that the system will easily pay for itself in it's 20+ year lifetime. So we can rest in the knowledge that the solar thermal system is not only cutting our CO2 emissions, it's also saving us money in the long-term.

910 bottles lying in a wall....

Okay, so we slightly underestimated how much time it'd take to fill the gabions. Not only was this due to the amount of time to collect all the bottles we needed, but also it proved to be a labour intensive and fiddle job getting the bottles and stone facing to look exactly how we want. Lobbing random rocks in would've been quicker and easier but wasn't the aesthetic we wanted, or the materials we planned on using.


So the combination of 15 baskets, 910 bottles (beer, wine & champagne), 23 tonnes recycled aggregate, several tonnes of builders rubble, 2 tonnes of recalimed local stone and plenty of hard labour have resulted in our final section of retaining wall.




We're really pleased with the result, but won't be rushing to build anymore! And the local wildlife must like it as we've already spotted a Death's Head Hawk Moth caterpillar setting up home in one of the many crevices.