How I have upgraded my semi-detached town house

PEC's own Energy Advisor, Didier shares his personal energy efficiency journey...


Since a young age I have been fascinated by the concept of free and clean energy. As a child I tinkered with, and built, various wind-powered ‘contraptions’ to go on water, land and ice. More recently, I wrote a dissertation on marine electric propulsion in Plymouth Sound as part of a Master in Marine Renewable Energy.

Naturally, when we moved in our semi-detached house in Plymouth many years ago we immediately wanted to reduce our carbon footprint and dependence on the grid, but quickly realised that solar thermal or PV installations were prohibitively expensive. This was in part because prices were much higher then, but also because the roof lay-out was not ideal (PV spread over two roof elevations, interference from Velux window and chimney stack). So we prioritised External Wall Insulation (EWI) subsidised at the time under the Green Deal scheme. Our loft was also insulated with spray-foam insulation between the rafters to make the roof space useable.

Recently I became aware that there was a strong market for second-hand solar PV systems and that it was relatively straight-forward to install ‘plug-in’ renewable micro generation systems.

Project Description

I installed a second-hand solar PV system on our low-pitched corrugated garage roof using second-hand panels and anchor bolts which cost a fraction of the price of new ones. I bought galvanised unistrut channel sections (rather than more expensive bespoke aluminium systems) to attach the array on garage roof. The roof was large enough to accommodate 12 panels (~3.1 kW) and fortunately was accessible enough to work on safely. The inverter and cabling were purchased new.

I also fitted a small vertical axis wind turbine (VAWT) on top of a scaffolding pole in our garden. The aim was to produce enough energy when the sun is not shining (i.e. night-time, winter) to offset most of the residual domestic consumption of items like chargers, fridge, router, etc... Unfortunately, I never managed to find a suitable grid-tie inverter that works at low voltage (12v) and power (300w), so the turbine is instead feeding a 12v car battery via a charge controller, and is used for lighting.

I am close to completing the conversion of an obsolete 16ft dinghy catamaran to electric propulsion. When completed the boat will also be powered by two SUP paddles (when used double-handed) and - it is hoped – by a solar panel to boost range.

Lessons Learnt

What worked well

  • Installing the solar PV system myself helped me learn a great deal about how solar PV installations work.
  • It is very satisfying to design a system that is both efficient and inexpensive whilst also reducing one’s carbon foot print and cutting energy bills.
  • It is also striking that the PV system has led to behavioural changes by the whole family. We are learning to maximise the use of the free electricity we generate, e.g. running the washing machine or boiling kettle when sun is shining!

What worked not so well

  • The wind turbine project was not as successful as intended. With the benefit of hindsight I should have gone for a more powerful system, but the cost was prohibitive.
  • The self-installed ‘plug-in’ solar system is not MCS (Microgeneration Certification Scheme) certified and as such will not generate Smart Export Guarantee (SEG) revenue. But this is minimal compared to the old FIT tariffs.

Advice to others

Use suitable opportunities to install retrofit measures. In our case the first trigger point arose when the walls of our house needed re-rendering. Having EWI installed instead allowed us to waterproof and insulate the house in one hit, at little extra cost. Our garage roof was also starting to leak and in need of TLC and fitting the solar PVs on it was done at the same time as its refurbishment.

What next?

  • In an ideal world battery storage will be added to the solar PV system in order to maximise the period during which we can use free electricity rather than send to the grid.
  • The roof on our small extension will need to be redone soon. We will try to use this trigger-point to add extra insulation (warm roof insulation set-up) and bring in the rainwater harvesting pipework required to feed the toilets.
  • Further down the line, our existing condensing boiler will be replaced by a heat-pump, and we envisage that at some point in the future our car will be electric and a charging point will be required. Before that, the acquisition of an electric bicycle is likely.