Solar energy

Living on the sun

Solar energy is a widely misunderstood concept. Many people automatically associate it with photovoltaics (PV) — shiny high-tech panels that generate electricity from the sun.

At Abrazo House, we do have a few small PV panels — powering isolated appliances like an air pump in our fish pond, and a LED light in the playhouse, although they provide only a minimal fraction of our energy needs.

In theory, Spain is potentially one of the best countries in Europe for solar and many other forms of renewable energy. But in practice, unfavourable government policies mean it is not economically viable to generate your own electricity here on a domestic scale (except in very specific circumstances).

However, all the energy we use to heat our buildings and to generate hot water comes from the sun — either directly or indirectly, in the form of firewood that we burn in our wood stove. Our heating bills are a nice round figure: zero. To achieve this we use solar energy in a number of different ways.

Passive solar design

The main house, where we now live year-round, is designed according to the principles of passive solar design. Where we live, in the northern temperate zone, this means having a well-insulated building with a lot of double-glazed south-facing windows to let in the sun and a large amount of thermal mass to store and release heat, so the house stays at an even temperature day and night, sunny days and cloudy days.

Wood: nature’s energy store

In a passive solar house, you shouldn’t need a boiler or central heating. In winter all our supplementary heat comes from a wood burning stove. We burn a mixture of firewood cut from our own trees, leftovers from building projects, and waste wood that we scavenge — all obtained for free. Essentially, we’re still using the sun’s energy, stored in the form of wood.

All the wood we burn is stacked to dry first (for a minimum of a year in the case of fresh-cut wood) which means that we have to burn a relatively small amount in order to keep the house warm. In winter we tend to live mostly around the wood stove in the main room of the house, the most pleasant area to be in. We like to look at the flickering flames; it’s what we have instead of TV.

Sun bathing

To heat water for baths, showers and washing up, we do have some solar panels — but not the kind that generate electricity. These are much simpler: they are more like anti-radiators that sit in the sun, heating up. The water that runs through them then circulates (by gravity, no pump required) to a storage tank that sits upstairs in the main house, and stores the hot water ready for use. We make the most of the sun by taking showers in the evening when the water’s nice and hot. On cloudy days, the wood stove also acts as a backup source of heat. It has a water tank attached to the back which heats up, and the hot water circulates to the storage tank via the same gravity-flow principle.

The whole system is extremely simple, with no electricity and no moving parts to go wrong. The total cost of the system (wood stove, solar panels, storage tank, valves, pipes and installation) came to about €3600 including installation. You can, of course, make solar thermal as complicated as you like, with electrical backup, thermostats, pumps, etc., for dubious gains in efficiency; but why would you bother? When you have a simple system that works, the way to improve it is not to make it more complicated, but to optimise the system while keeping it simple.