As a new poster on these forums, I wondered whether folks might be interested in the renewable energy system we have put in to our house in Scotland.
First, our situation. We live in a sheltered part of Northern Scotland, relatively dry. Summer highs of around 18 C on average. Winters typically below freezing at night, highs of 2-6 C in the day. The house is 200 years old, rendered rubble walls, slate roof, single-glazed windows. It is sheltered and shaded by trees, preventing the effective use of wind or solar power. The house is also "listed", meaning there are limits to the changes we can make to the structure or appearance. We have put in some insulation, and secondary double glazing, but the house is never going to be the most thermally efficient property.
When we bought the house it had an oil-fired boiler (furnace) providing hot water and serving a typical wet central heating system via radiators. We were going through around five tank-fills a year (over 1000 gals). We wanted a system that would run on wood (of which we have an ample supply), and would be efficient.
Looking around, we found that a lot of talk around energy efficiency focused either on the combustion efficiency of the actual appliance, or the thermal efficiency of the building. We'd already accepted we didn't have a thermally efficient building (not by current standards,anyway!)
We eventually opted for a wood fired Rayburn. Anyone with a UK background will know that a Rayburn is a multi-function range-cooker and boiler. It sits in the kitchen in place of the cooker, providing cooking facilities (two ovens and a hotplate), space heating to the kitchen and hot water and central heating to the radiators. It works in conjunction with the oil fired boiler, feeding heat into a thermal store. The oil boiler rarely comes on, except in especially cold conditions, or in the summer when we don't have the Rayburn lit.
The Rayburn's efficiency is about the same as an average wood burning stove, but not as high as, say, a wood-gasification boiler. It's real strength is the fact that it does so many things. As well as the above functions, it also replaces:
- An electric kettle (a kettle sits on the hotplate most of the time)
- A tumble drier ( we can air clothes on a rack above the stove, or even on the insulated lids over the hotplate)
- A dehydrator for drying food, herbs, etc.
- A toaster
- A warming plate
In winter, the Rayburn runs 24/7, providing constant, gentle heat to replace that lost by the house. At night we bank it up and restrict the airflow so it just ticks over till morning, all the time leaching heat into the thermal store, so there is plenty available when the heating pump kicks in in the morning.
So, a not particularly efficient house, and a stove that's not going to break any records for efficiency. But, as an overall system, it works well for us. Since it went in, we have reduced our electricity consumption by around 25% as a direct result, as well as virtually eliminating oil use in the winter. The secret is in finding a use for the heat that's constantly available.
On a final note, it's low-tech. It requires no electricity to start (newspaper, kindling and a match only!), and the heat reaches the thermal store by thermo-syphoning. There is a circulation pump for the radiators but, in a worst case power-down scenario, we can just gather round the Rayburn for warmth. And we still have hot running water.
Hope this is of some interest. Any observations /questions welcome. You can follow a diary of the installation on our blog (www.newlifeinnorthernscotland.blogspot.co.uk)