Skylights are an aesthetically pleasing design choice, but they are also an underrated source of sustainable thermal energy for buildings, according to a new study by researchers at the University of Oregon, US.
Passive solar heating systems collect natural light through skylights or windows and use it to heat rooms directly, without converting it into electricity. Based on a detailed analysis of heating needs and solar energy availability in the United States, researchers calculated that such installations could meet one-third of residential space heating needs.
The results of the first ever detailed survey of passive solar appear in the November issue of Renewable and Sustainable Energy Reviews.
Passive solar, great news
The news is very encouraging given our need to move away from fossil fuels. Heating uses about 50% of most people's household energy budgets and is the main source of building-related carbon emissions. In Europe, more than 80% of heating is powered by fossil fuels. And even in the US, most heating systems still rely on oil or natural gas.
While studying sustainable architecture, it became clear that there were many resources that we were not tapping into. Passive solar heating was one of them. Although it has been used for centuries, it has no longer been widely practiced as a sustainable design technique.
Alexandra Rempel, co-author of the study
A systematic review
To find out how much solar energy was left unused, Alexandra Rempel and colleagues compared a lot of data. To be precise, those on solar radiation levels, external temperatures and energy consumption for heating at different times of the year. The team took into account many different variables, such as the position of the sun in the sky and the length of daylight hours. Based on these calculations, he then mapped the locations and times of year where passive solar heat resources exceeded heating needs.
According to their calculations, there are about 7 megawatt hours of solar energy available per household per year. And this at times of the year when homes need heating! Current technology could capture about 50% of that for use, assuming 10 square meters of glass per roof. This means that if everyone installed a passive solar heating system, the sun could provide about a third of the heat a typical household needs in a year.
That's not all, but it's much more than today. Or am I wrong?
It is a lot more than just theoretical work
During the pandemic, Rempel herself was convinced of the goodness of her studies and installed a series of skylights in her home in Eugene, the city (170.000 inhabitants) in which she lives. In addition to the glazing, he then proceeded to install sliding insulating panels to keep the heat at night. Based on its typical power consumption and the size of the skylight, he estimated it will reduce heating bills by 80%.
It is worth considering, I would say. More and more architects and building planners should convince themselves of the merits of skylights in new buildings, where it is cheaper and easier than adding them later. More incentives for passive solar should be provided. Discounts or tax breaks for buildings that incorporate these solutions.
When we say "opening a window" onto a more sustainable future.
