Passive Solar Power

One of the key routes to using solar power

Of the three main routes to using solar power - active, passive and photovoltaic - passive solar could arguably have the biggest impact on our daily lives.

Passive solar's potential impact on energy consumption is enormous, and its technology can be applied anywhere with sufficient sunshine.

The concept behind passive solar is simple. It involves managing natural sunlight in such a way that it maintains a desired temperature inside a building. The remains of early Greek buildings show that their architects were experts in passive solar design.

How did the Greeks use solar power in their homes?

Perhaps the Greek architects drew their inspiration from compass termites. When digging their mounds, these creatures choose a position relative to the sun in order to maintain a steady temperature deep inside the mound. In a twenty-four hour period, the temperature does not vary beyond two or three degrees.

In much the same way, the orientation and design of ancient Greek buildings maximized the use of the sun to maintain constant temperatures all year round. Very thick walls captured and retained the heat, whilst trees were used to protect the exterior of the building from the greatest temperature extremes.

Now that we have temperature controlled living spaces, why use passive solar design?

Air conditioning and central heating may be convenient, but we pay a high personal and environmental cost.

Western countries, in particular, use massive amounts of energy to heat and cool their buildings. For example, homes and commercial buildings account for approximately one third of US energy use.

With today's technology, houses with passive solar design and efficient insulation have been proven to save as much as ninety nine per cent of energy used for space heating and cooling.

A striking example of passive solar design is the Rocky Mountain Institute (RMI) Headquarters. Some of the energy saving equipment was more expensive (for example "super windows", which can insulate as well as twelve panes of normal glass). However, this outlay was compensated for because investment in heating boilers and ducting was no longer necessary.
The overall cost of the RMI building was no greater than it would have been using traditional methods. The difference lies in the projected savings, which come from a ninety-nine per cent decrease in the energy used for space on water heating and other such activities. These savings alone are sufficient to pay for the entire building costs in forty years.

Are there any other benefits to passive solar?

Sunlight by its very nature provides light as well as thermal energy. Harnessing the sun's rays to their fullest extent not only saves energy, but also makes for a brighter and more pleasant living or working environment.

What is more, the pace of technological change in this sector is such that many of the building techniques used in passive solar have been dramatically improved upon, and their costs have reduced. Passive solar has come a long way since its ancient Greek origins, and its place in our future is assured.