Thursday, September 8, 2016

Miscellaneous “Sun & Shadow” Items – August 2016

The following are miscellaneous sun, shade, solar and solar energy facts and comments. They were derived from our twitter feed @SunPosition

Our monthly sunrise/sunset tables have been updated.

The science of shadows and solar panels | InfraCircle

Free stock photo of sun, technology, reflection, power

image via pexels

“What happens when shadow falls on a solar panel?

Imagine a multi-lane expressway with automobiles moving at high speeds without any congestion. A solar panel consists of a number of cells, which are comparable to the expressway lanes. When solar radiation falls on these cells, free electrons are released because of the photovoltaic effect and move around in the circuit (like the automobiles) in the form of an electric current. These cells are connected in series to form a string and a number of such strings are connected in parallel to form a panel.

Now if an obstacle casts a shadow on one cell, the photovoltaic effect is cut off, blocking the path of all the electrons from all the cells in that string. This is similar to a large fissure appearing in one of the lanes on the highway. All the automobiles in that lane would create congestion similar to the entire string of cells rendered useless because of the shadow. This creates enormous stress on the entire panel as a hot spot is formed due to accumulation of electrons. This may have a propagative effect, if not rectified, and can destroy the entire panel over time. Similarly, if the crack is not repaired, it will propagate into other lanes and soon the cascading effect will lead to utter chaos on an impassable expressway. The actual physics behind this phenomenon is slightly more complicated, but the comparison above could give an idea of the same.

How do shadows affect RTPV systems?

After having interacted with numerous RTPV consumers, it was observed that most of the complaints were about systems generating less revenue than expected. Subsequent site visits showed that a majority of these RTPV systems were poorly designed and did not account for shadows. Consumers, who had not been informed about the adverse impacts of shadows, had been criticising the distribution utilities for foul play when in fact, their own RTPV systems were generating less electricity.

In India, RTPV systems should face true south and any nearby obstacle, including neighbouring buildings, trees, poles and wires, should be factored into the designing phase. Nearby objects such as water tanks, clothes lines, adjacent buildings and poles cast darker shadows compared with obstacles which are at a fair distance. Shadows from the latter category and thin wires do not cause much hindrance because sunlight tends to diffuse around them and compensate. However, caution should be exercised while designing a RTPV system. Another aspect of shadows is that they are not static. They follow the sun’s trajectory, thereby becoming shorter in their span during summer and longer during winter for any particular time of the day. Hence, it is essential to calculate the area covered by shadows throughout the year for optimal RTPV system design…”

Toronto dips to under 14 hrs of daylight after Aug 14. Still not too shabby.

Watch the sun rise in line with Toronto streets tomorrow morning. Torontohenge Aug 23 - 6:32 AM

To assist earthquake rescuers, we have posted a sunrise/sunset table for Amatrice Italy -

There are just over 13 hrs daylight available in the Italy Earthquake area to the end of this month. Rise ~6:30, set ~19:45 local time.

RT CanSIA @CanadianSIA Solar Power sculpture could desalinate 1.5 billion gallons of drinking water for California | Independent

“Is it public art, or is it a power station? This shimmering design for “The Pipe”, a finalist in the 2016 Land Art Generator Initiative (LAGI), is intended to blur the lines between the two. Imagined here as a floating installation off the coast of Santa Monica, California, the Pipe is an electromagnetic desalination device, powered by the sun. It also looks great on the horizon…”

> Genius! Oakland California also saw a solar billboard / artwork designed for SunChips. @CanadianSIA -

time-lapse video here -

Industry groups call for national plan for energy-efficient buildings | Construction Canada

“Eleven organizations, including the Royal Architectural Institute of Canada (RAIC), Passive House Canada, and the Canadian Energy Efficiency Alliance (CEEA), are calling on the federal government to implement a national plan for improving the energy efficiency of the country’s buildings…”

My twitter header photo is of the Air India Flight 182 memorial sundial in Toronto that I had the honour of designing.

Cheers, Ralph

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