Sunny day

May 1, 2009 | Bruce N. Wright

In addition to recent talk in the current down cycle about making our automobiles smaller and greener as the world economy forces all automobile manufacturers to reassess their future, architects have acknowledged the equally important need for designing energy miserly buildings to sustain future design possibilities. Besides designing more thermally efficient buildings, architects are discovering the use of alternative energy systems such as wind, solar and biomass energy systems. All of these “new” systems have a long way to go before they become intuitive in regular practice. However, several new technological innovations have started to give hope of more regular use of photovoltaics, the subject of this issue’s theme.

British scientist David J. C. McKay has identified four forms of solar power that can be exploited, some more easily than others.* According to McKay, these four forms are solar thermal, solar photovoltaic, solar biomass and food. Solar thermal uses the sunshine directly on the surface of a building or on water to heat it up. (McKay estimates a system of 10m² per person would generate about 13kWh per day at a 50% efficiency.) Solar photovoltaic converts the sun’s rays directly into electricity. (Typical solar panels have a range of 10– 20% efficiencies maximum and would produce about 5kWh per day per person.) Solar biomass uses trees, bacteria, algae, corn, soy beans or oilseed to make energy fuels, chemicals or building materials. (McKay estimates about 24kWh/day per person but the system requires large tracts of land to produce.) The fourth category, food, converts the energy stored in food plants and puts it directly into humans or animals.

Of these four methods, the one that has been attracting designers with the most interesting possibilities for building technology is solar photovoltaics. Although there is much still to do in increasing efficiencies and practicality, enough has been done in this line of exploration to cause many designers to seriously consider integrating PV into their designs. Read the feature stories in this issue and judge for yourself.

* David J.C. MacKay, Sustainable Energy – without the hot air (Cambridge, u.k.: UIT Cambridge ltd., 2009), Available free online from www.withouthotair.com.

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